Metabolically associated steatotic liver disease in children: clinical guidelines

List of Abbreviations

BP – blood pressure

AH – arterial hypertension

ALT – alanine aminotransferase

AST – aspartate aminotransferase

WHO – World Health Organization

GGT – gamma-glutamyl transferase (gamma-glutamyl transpeptidase)

HCC – hepatocellular carcinoma

GLP-1 – glucagon-like peptide-1

CI – confidence interval

DHA – docosahexaenoic acid (omega-3 polyunsaturated fatty acid)

DPP-4 – dipeptidyl peptidase-4

FLD – fatty liver disease

GD – gallstone disease

IL – interleukin

BMI – body mass index

IR – insulin resistance

HDL – high-density lipoproteins

LDL – low-density lipoproteins

VLDL – very low-density lipoproteins

HCF – healthcare facility

LPS – lipopolysaccharide

MASLD – metabolic dysfunction-associated steatotic liver disease

MASH – metabolic dysfunction-associated steatohepatitis

MS – metabolic syndrome

MRI – magnetic resonance imaging

NAFLD¹ – non-alcoholic fatty liver disease¹

NASH – non-alcoholic steatohepatitis

LPO – lipid peroxidation

PUFA – polyunsaturated fatty acids

RAAS – renin-angiotensin system

RCT – randomized controlled trial

DM – diabetes mellitus

FFA – free fatty acids

CVD – cardiovascular disease

TG – triglycerides

UDCA** – ursodeoxycholic acid**

US – ultrasound examination

TNF-α – tumor necrosis factor-alpha

Chol – cholesterol

ALP – alkaline phosphatase

AUROC (Area Under The Receiver Operating Characteristic Curve) – area under the receiver operating characteristic curve

HbA1c – glycated hemoglobin (A1c)

HOMA-IR (Homeostasis Model Assessment-Insulin Resistance) – homeostasis model assessment of insulin resistance

IRS-1 – gene encoding insulin receptor substrate 1

KLF-6 – gene encoding Krüppel-like factor 6

LPIN1 – gene encoding lipin-1

NAS - NAFLD activity score – NAFLD activity score¹

NAFLD - nonalcoholic fatty liver disease – non-alcoholic fatty liver disease¹

PAI-1 (plasminogen activator inhibitor-1) – plasminogen activator inhibitor-1

PDFF (proton density fat fraction) – proton density fat fraction of liver tissue, assessed by MRI

PNFI (Pediatric NAFLD Fibrosis Index) – Pediatric NAFLD Fibrosis Index

PNFS (Pediatric NAFLD Fibrosis Score) – Pediatric NAFLD Fibrosis Score

PNPLA3 (patatin-like phospholipase domain-containing protein 3) – patatin-like phospholipase domain-containing protein 3, adiponutrin gene

SDS (Standard Deviation Score) – standard deviation score

SOD-2 – superoxide dismutase 2 gene

TM6SF2 (transmembrane 6 superfamily member 2) – transmembrane 6 superfamily member 2

TLR (toll-like receptors) – toll-like receptors 

Note:

¹ – NAFLD (non-alcoholic fatty liver disease) is an outdated term; MASLD (metabolic dysfunction-associated steatotic liver disease) is currently accepted for use. It is mentioned in the current clinical guidelines within grading scales, as these were developed before the terminology change.

Terms and Definitions

Fatty liver disease (FLD) / steatotic liver disease – a general term combining pathological conditions characterized by excessive lipid accumulation in the liver, including the following diseases/groups of diseases:

1) metabolic dysfunction-associated steatotic liver disease (MASLD);

2) alcoholic liver disease;

3) metabolic dysfunction-associated steatotic liver disease combined with excessive alcohol consumption;

4) fatty liver disease of specific etiology;

5) cryptogenic fatty liver disease.

Metabolic dysfunction-associated steatotic liver disease - MASLD – represents an association of hepatic steatosis with overweight/obesity and cardiometabolic risk factors.

Metabolic dysfunction-associated steatohepatitis - MASH – a progressive form of MASLD, characterized by steatosis, hepatocyte injury as a result of inflammation and necrosis development, with or without fibrosis.

Waist circumference (WC) – an indicator used to diagnose visceral fat accumulation and abdominal (visceral) obesity. Determined by measurement at the midpoint between the lower ribs and the upper iliac crest.

Controlled attenuation parameter – refers to an ultrasound method for assessing hepatic steatosis, based on the property of ultrasound signals to "attenuate" in fat-containing tissues (signal attenuation occurs in proportion to the degree of steatosis).

Proton density fat fraction of the liver – determined during MRI, calculated as the ratio of the proton density (number of protons) of liver fat to the total proton density of the liver (number of protons of fat and water).

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

The introduction of the term "metabolic dysfunction-associated steatotic liver disease" (MASLD) is caused by changes in the nomenclature of conditions grouped under the term fatty liver disease (FLD), a characteristic feature of which is the excessive accumulation of lipids in the liver. Previously, FLD included two main pathological conditions: alcoholic liver disease (ALD), the development of which is associated with alcohol consumption, and non-alcoholic fatty liver disease (NAFLD) – an umbrella term encompassing all liver pathologies that have morphological similarities with ALD but are not related to alcohol intake [3, 12]. Thus, the term NAFLD only indicated the exclusion of alcohol consumption as an etiological factor, but did not help in deciphering the causes of steatosis development.

Epidemiological data have shown that in the majority of patients, the development of hepatic steatosis is closely interrelated with obesity, insulin resistance (IR), impaired carbohydrate metabolism, atherogenic dyslipidemia, and high risks of cardiovascular diseases: atherosclerosis, coronary artery disease, and myocardial infarction. Such metabolic changes combined with high risks of cardiovascular pathology led to the separation of a distinct condition from the NAFLD cluster – metabolic dysfunction-associated steatotic liver disease (MASLD). However, there remained a group of patients with hepatic steatosis who did not fit the clinical characteristics of MASLD. Therefore, in pediatrics, the following groups of diseases presenting with hepatic steatosis are distinguished [6]:

1 type – patients with FLD due to inherited metabolic disorders;

2 type – patients with MASLD;

3 type – patients with fatty liver disease of undetermined etiology.

Metabolic dysfunction-associated steatotic liver disease – a chronic liver disease characterized by excessive fat accumulation associated with overweight/obesity, IR, carbohydrate metabolism disorders, dyslipidemia, and chronic low-grade nonspecific inflammation, with the exclusion of genetic diseases, infections, and exposure to exogenous factors (ethanol, drugs, fasting, etc.) causing steatosis. MASLD represents a hepatic manifestation of systemic metabolic disorders and is an independent risk factor for a more severe course and unfavorable prognosis of cardiovascular (and probably renal) diseases in both adults and children [4, 5].

The diagnosis of MASLD [6] includes the presence of hepatic steatosis (detected by ultrasound (liver ultrasound) or another imaging method, or by histological method) in overweight/obese patients in the presence of 1 or more cardiometabolic risk factors:

- waist circumference greater than the 90th percentile for age, height, and sex;

- impaired carbohydrate metabolism (fasting glucose > 5.6 mmol/L in capillary blood or > 6.1 mmol/L in venous plasma, postprandial glucose > 7.8 mmol/L, HbA1c > 5.7%) or type 2 diabetes mellitus;

- elevated blood pressure ≥ 130/85 mm Hg or greater than the 90th percentile for age, height, and sex;

- plasma triglycerides: in children under 9 years old ≥ 1.13 mmol/L, in children 10–18 years old ≥ 1.47 mmol/L;

- plasma HDL cholesterol < 1.04 mmol/L.

MASLD includes 2 pathological conditions: simple steatosis and steatohepatitis (metabolic dysfunction-associated steatohepatitis – MASH).

Simple steatosis – a condition in which signs of inflammation and fibrosis in the liver are absent. With persistent risk factors, simple steatosis may acquire a progressive course with the development of fibrosis, but the rate of its progression is significantly slower than in MASH [2].

Metabolic dysfunction-associated steatohepatitis (MASH) – characterized by steatosis, intralobular inflammation, and may proceed with the development of pericentral and perisinusoidal (less commonly portal) fibrosis. Unlike adults, ballooning degeneration of hepatocytes is not characteristic of children. MASH is a progressive form of MASLD with a risk of developing liver cirrhosis, hepatocellular carcinoma (HCC), cardiovascular diseases, and their complications [1].

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

Currently, MASLD is considered a multifactorial pathology developing as a result of a complex interaction of environmental, genetic, and epigenetic factors [7].

Proven risk factors for the development of MASLD are presented in Table 1.

Table 1. Risk factors for the development of MASLD in childhood [5, 7]

Hepatic steatosis, which is a key feature of MASLD, develops as a result of an impaired balance of hepatic lipid homeostasis due to:

1) excessive influx of energy substrates, predominantly carbohydrates, fatty acids, and cholesterol. The main sources of free (non-esterified) fatty acids entering the liver include their increased release from adipocytes as a result of lipolysis (about 60%), hepatic carbohydrate conversion (de novo lipogenesis – 26%), and excessive dietary fat intake (14%) [8, 9];

2) dysfunction of hepatocyte organelles involved in lipid metabolism (oxidation);

3) impaired lipid export from hepatocytes with the formation of very-low-density lipoproteins (VLDL) [6].

In response to excessive lipid accumulation, innate immunity factors are activated in the liver with the participation of resident macrophages (Kupffer cells) and sinusoidal endothelial cells, leading to the production of inflammatory mediators and the subsequent recruitment of neutrophils and macrophages to the liver [10].

MASLD develops as a result of complexly acting, concurrently occurring pathological processes [5, 10], which include:

1. IR with the development of glucotoxicity.

2. Lipotoxicity caused by excessive triglyceride accumulation in hepatocytes due to an imbalance in adipose tissue hormone production (decreased adiponectin production and increased leptin synthesis) characteristic of visceral obesity.

3. Impairment of the microbiota-gut-liver axis. Characteristic changes in the gut microbiota in MASLD include an increase in representatives of Proteobacteria and Bacteroidetes along with a decrease in the abundance of Firmicutes. In addition to the synthesis of a number of hepatotoxic substances (ammonia, phenol, ethanol, etc.), the main bacterial product involved in the pathogenesis of MASLD and MASH is lipopolysaccharide (LPS), an active component of bacterial endotoxin that activates Toll-like receptors type 4 (TLR4), with a subsequent increase in the expression of genes involved in the synthesis of inflammatory cytokines, such as tumor necrosis factor alpha (TNF-α), interleukin 1 (IL-1), and IL-6, which promotes the development of insulin resistance, hepatosteatosis, and initiates inflammation and fibrogenesis in the liver.

4. Influence of genetic factors – identification of sequence variations (single nucleotide polymorphisms) in gene loci (Table 2).

Table 2. Influence of single nucleotide polymorphisms on the development and progression of MASLD [10, 73].

Carriers of the PNPLA3 I148M and TM6SF2 E167K variants have higher liver fat content and an increased risk of developing MASLD. Detection of SOD2, IRS1, KLF6 polymorphisms is associated with the risk of fibrosis progression and the development of steatohepatitis in patients with MASLD. Currently, it is premature to discuss the widespread use of genotyping in routine practice [11].

Consequently, the pathogenesis of MASLD represents a complex of pathological processes leading to impaired hepatic lipid homeostasis: free fatty acids (FFAs) formed in adipose tissue as a result of lipolysis and de novo lipogenesis exceed the liver's capacity for their metabolism (via β-oxidation) and excretion with VLDL formation [10]. The consequence is the development of oxidative stress, low-grade inflammation, and activation of profibrotic factors that determine the development of hepatitis with a potential progression to cirrhosis/HCC. Visceral obesity, subclinical inflammation, and insulin resistance represent common pathogenetic links of both metabolic syndrome (MetS) and MASLD, which emphasizes the relationship between liver pathology and metabolic dysregulation and provides a rationale for considering MASLD as a manifestation of MetS not only in adults but also in pediatric practice [12, 74].

Components of MetS include: waist circumference greater than the 90th percentile for age, height, and sex; impaired carbohydrate metabolism (fasting glucose > 5.6 mmol/L in capillary blood or > 6.1 mmol/L in venous plasma, postprandial glucose > 7.8 mmol/L, HbA1c > 5.7%) or type 2 diabetes mellitus; elevated blood pressure ≥ 130/85 mm Hg or greater than the 90th percentile for age, height, and sex; plasma triglyceride level in children under 9 years ≥ 1.13 mmol/L, in children 10–18 years ≥ 1.47 mmol/L; plasma HDL cholesterol level < 1.04 mmol/L.

1.3 Epidemiology of the Disease or Condition

Due to the steady rise in childhood obesity worldwide, MASLD is one of the most common causes of chronic liver disease. The prevalence of hepatic steatosis based on ultrasound data is 7.4% among children and adolescents in the general population, reaching 34% in children with obesity and 80% in the morbid obesity group [13]. Autopsy data in children indicate the detection of hepatic steatosis in 4.2–9.6% of cases, increasing to 38% in children with obesity [14].

The frequency of MASLD increases with age, rising from 0.7% in children aged 2–4 years to 17% in adolescents [15]. The prevalence of MASLD is significantly higher in boys (3.4%, 71/2,080) than in girls (2.8%, 58/2,061) [16].

With age, MASLD in children tends to progress, partly due to comorbidities associated with obesity, leading to a decrease in quality of life and life expectancy [4].

The proportion of MASH in the structure of MASLD ranges from 12.5% to 23.4%, depending on the severity of obesity [17].

1.4 Features of Coding the Disease or Condition

K75.8 - Other specified inflammatory liver diseases

K76.0 - Fatty (change of) liver, not elsewhere classified

1.5 Classification of the disease or condition

Two main phenotypes (forms) of MASLD are distinguished:

- simple steatosis;

- steatohepatitis.

1.6 Clinical presentation of the disease or condition

The clinical presentation of MASLD in children is nonspecific and variable, and in most cases, it is asymptomatic. Manifestations of metabolic disorders – obesity, impaired glucose tolerance, arterial hypertension – come to the forefront in the clinical picture. As a rule, the intensity of complaints reported by children does not correlate with the degree of liver parenchyma damage.

The absence of pathognomonic symptoms makes the diagnosis of MASLD a diagnosis of exclusion.

The clinical picture may include the following nonspecific clinical manifestations:

- asthenic syndrome: fatigue, quick exhaustion, weakened concentration, labile mood, decreased physical and mental activity;

- dyspeptic syndrome: flatulence, mushy stool consistency;

- abdominal pain syndrome: dull, aching pain and/or a feeling of heaviness in the right upper quadrant.

On palpation and percussion of the abdomen in patients with MASLD, a moderate enlargement of the liver may be detected. Hepatomegaly syndrome with significant liver enlargement (more than 2–3 cm below the costal margin) and splenomegaly are not characteristic of MASLD [1, 11].

Clinical manifestations, biochemical or imaging methods do not allow differentiation between hepatic steatosis and MASH [11]. At the same time, cytolysis syndrome when hepatic steatosis is detected by non-invasive imaging methods, after excluding other possible causes of steatosis, may indicate the presence of steatohepatitis.

2. Diagnostics, medical indications and contraindications for diagnostic methods

Criteria for Establishing the Diagnosis/Condition

To establish a diagnosis of MASLD, the following data are taken into account:

1. Epigenetic risks – presence of overweight/obesity and/or diabetes mellitus in the child's mother during pregnancy [18] and other risk factors listed in Table 1.

2. Lifestyle characteristics – increased caloric intake due to an excess of saturated fats, refined carbohydrates, sugar-sweetened beverages, high fructose consumption, and a sedentary lifestyle [1, 11].

3. Physical examination – determination of anthropometric parameters (height, BMI, waist circumference) with evaluation of physical development, type of obesity, detection of clinical symptoms of insulin resistance (Acanthosis nigricans), detection of red flags characteristic of diseases with similar symptoms [41], and determination of liver and spleen size.

4. Laboratory evaluation aimed at detecting cytolysis, cholestasis, and metabolic disorders (carbohydrate and lipid metabolism disorders).

5. Instrumental evaluation aimed at detecting steatosis (liver ultrasound, magnetic resonance imaging [MRI]), liver fibrosis (elastography), and performing a liver biopsy in complex and ambiguous situations.

Due to the absence of specific symptoms, the diagnosis of MASLD is based on the detection of hepatic steatosis and cardiometabolic risk factors (see definition) and the absence of "red flags", the presence of which requires differential diagnosis with liver diseases having similar laboratory and instrumental findings.

Red flags indicating liver pathology caused by other causes include [4, 6]:

1. Early onset of hepatic steatosis signs (in children under 10 years of age). MASLD is generally uncommon in children under 3 years of age and less common in children under 10 years of age.

2. Typical age of steatosis onset (over 10 years of age) characteristic of MASLD, but in the presence of laboratory/ultrasound abnormalities that:

1) are uncharacteristic of MASLD;

2) lack positive dynamics against the background of weight loss.

3. Clinical features uncharacteristic of MASLD, indicating other liver diseases:

• absence of overweight/obesity

• symptoms of acute liver failure;

• symptoms of cholestasis;

• marked hepatomegaly/hepatosplenomegaly.

When "red flag" symptoms are identified, pathological conditions presented in Appendix A3.1 [6] must be ruled out.

2.1 Complaints and Anamnesis

Taking the history of present illness and anamnesis is aimed at identifying diseases associated with MASLD and their complications: overweight/obesity, arterial hypertension, type 2 diabetes mellitus, dyslipidemia [1, 6, 11].

• In children with suspected MASLD, it is recommended to:

  - take the medical history, including family history, to identify risk factors for MASLD development;

  - identify epigenetic risks — the presence of overweight/obesity and/or diabetes mellitus in the child's mother during pregnancy (Taking anamnesis and complaints in diseases of the liver and biliary tract) — performed as part of the initial and follow-up appointment (examination, consultation) of a gastroenterologist and/or pediatrician/general practitioner (family doctor) [6, 18].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comments: see section 1.2 "Etiology and pathogenesis of the disease or condition (groups of diseases or conditions)". When taking the history of a patient with suspected MASLD, attention should be paid to the presence of individual and family risk factors (Table 1) [5, 7].

• In children with suspected MASLD, it is recommended to assess dietary preferences (consumption of high-calorie foods, excessive intake of saturated fats, refined carbohydrates, sweetened beverages, fructose) and evaluate the level of physical activity, performed as part of the initial and follow-up appointment (examination, consultation) of a gastroenterologist and/or nutritionist and/or pediatrician/general practitioner (family doctor) for diagnostic purposes [1, 11].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comments: high-calorie nutrition with excessive fructose consumption, along with decreased physical activity, contributes to the progression of MASLD and serves as a target for therapeutic strategies in this group of patients [11].

2.2 Physical Examination

• In a child with suspected MASLD, it is recommended to perform a visual examination in diseases of the liver and biliary tract, Palpation in diseases of the liver and biliary tract, Percussion in diseases of the liver and biliary tract, Determination of waist circumference, Measurement of blood pressure on peripheral arteries to roughly assess the size of the liver and spleen, and search for symptoms indicating cardiometabolic risk factors (performed as part of the initial/follow-up appointment (examination, consultation) of a gastroenterologist/pediatrician/general practitioner (family doctor)) [11].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comments: in patients with MASLD without signs of advanced fibrosis, a moderate enlargement of the liver may be noted; the liver edge is rounded, and its consistency is unchanged. A significant enlargement of the liver and spleen (hepatosplenomegaly) is uncharacteristic of MASLD and refers to "red flag" symptoms indicating other liver pathology (see section 1.6 "Clinical presentation of the disease or condition (groups of diseases or conditions)" and section 2 "Criteria for establishing the diagnosis/condition") [4, 6].

In turn, in patients with overweight/obesity, impaired carbohydrate metabolism, and lipid metabolism disorders, the condition of the liver must be assessed. Metabolic syndrome (MS) and its components correlate with liver fat content, regardless of BMI values; the presence of MS increases the risk of MASLD progression [1, 5, 11].

• In all children with suspected MASLD, to determine the presence, as well as the degree and type of obesity, it is recommended to measure height, body weight with the calculation of body mass index (BMI), determine standard deviation scores (SDS) of these indicators, and subsequently interpret them [21].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comments. According to clinical guidelines and taking into account WHO recommendations, obesity in children and adolescents aged 0 to 19 years should be defined as a BMI equal to or greater than + 2.0 BMI SDS, and overweight as from + 1.0 to + 2.0 BMI SDS. Normal body weight is diagnosed when BMI values are within ± 1.0 BMI SDS. The diagnosis of abdominal obesity is associated with a waist circumference indicator (> 90th percentile) when compared with the age norm of the indicator.

To diagnose overweight and obesity in children, WHO Anthro (for ages 0-5 years) and AnthroPlus (for ages 5-19 years) software for personal computers should be used. An increase in waist circumference is a sign of abdominal obesity, which is a component of metabolic syndrome.

• In a child with detected hepatic steatosis, in the absence of characteristic manifestations of MASLD, it is recommended to perform differential diagnosis in order to rule out/confirm congenital inborn errors of metabolism (type 1 pediatric fatty liver disease) associated with carbohydrate, protein, and lipid metabolism, mitochondrial disorders, and aminoacyl-tRNA synthetase deficiencies) [6, 20].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comments: due to the absence of pathognomonic symptoms for MASLD, attention should be paid to "red flag" symptoms and the presence of syndromic manifestations, which requires differential diagnosis with other pathological conditions having symptoms similar to MASLD, primarily congenital metabolic disorders (see section 1.6 "Clinical presentation of the disease", Appendix A3).

2.3 Laboratory Diagnostics

Comments: abnormalities in the complete blood count with differential are not characteristic of MASLD.

Comments: the biochemical blood test may show an increase in the activity of serum transaminases (ALT and AST), GGT, ALP, and bilirubin levels. In simple steatosis, serum transaminase activity usually does not exceed the upper limit of normal values. MASH is characterized by the following changes:

o A persistent (> 3 months) increase in ALT levels by more than two times compared to the upper limit of normal requires screening for MASH or other causes of chronic hepatitis, including, if necessary, liver biopsy (Ultrasonographically guided liver biopsy, pathological-anatomical examination of biopsy (surgical) material from percutaneous liver biopsy) [1].

o An increase in the AST/ALT ratio of more than 1 is characteristic of MASH [20].

o GGT activity in patients may be elevated, but as a rule, no more than 2–3 times, and in some of them, this may be the only abnormality in the biochemical test.

o ALP activity increases less frequently and usually does not exceed reference values by more than 2 times [23].

Comments: carbohydrate metabolism disorders are diagnosed at a glucose level > 5.6 mmol/L in capillary blood or > 6.1 mmol/L in venous blood plasma, postprandial glucose level > 7.8 mmol/L, HbA1c > 5.7%.

Comments: MASLD is characterized by increased plasma triglyceride levels: in children under 9 years old $\ge$ 1.13 mmol/L, in children aged 10–18 years $\ge$ 1.47 mmol/L; plasma HDL cholesterol < 1.04 mmol/L [3].

Comments: for more details on assessing renal function, see the clinical guidelines "Chronic Kidney Disease" (pediatric age group).

2.4 Instrumental Diagnostics

2.4.1 Diagnosis of steatosis

Comments: to detect hepatic steatosis, ultrasound examination (ultrasound) of the abdominal cavity (comprehensive) is used as a widely available and effective method. The combined sensitivity and specificity of ultrasound in detecting steatosis are 85% (ranging from 60–96%) and 94% (84–100%), respectively, when compared with liver biopsy results [11].

The main limitations of the ultrasound method lie in detecting steatosis only when fat accumulation exceeds 12.5–20%. Sensitivity and specificity increase with the severity of steatosis and, to a certain extent, depend on the experience of the examining physician [26].

Ultrasound signs of MASLD include:

o diffuse hyperechogenicity of the liver parenchyma and heterogeneity of its structure;

o indistinctness and/or accentuation of the vascular pattern;

o distal echo attenuation [27].

Ultrasound makes it possible to rule out other pathological changes in the liver and gallbladder—cysts, congenital anatomical disorders, and masses [11].

Comments: the possibility of quantifying steatosis is carried out by measuring the attenuation of the ultrasonic echo wave using liver elastography. The method has high sensitivity and specificity in detecting minimal and moderate steatosis.

Determination of the controlled attenuation parameter of the ultrasound wave for the diagnosis of hepatic steatosis in children surpasses comprehensive abdominal ultrasound. Hepatic steatosis is indicated by values exceeding 249 dB/m with a sensitivity of 0.72 and a specificity of 0.98–1.00 [28]. The application of the method is limited for assessing steatosis grades in children with BMI > 30 kg/m² [30].

Comments: the MRI-PDFF method allows the most accurate calculation of the quantitative and volumetric fat content in the liver (the minimum threshold for detecting fat accumulation is 5%).

Good correlation has been shown in the detection of steatosis by MRI-PDFF and histological (pathological-anatomical) methods. Mean AUROC values for patients without steatosis and with mild steatosis (5–33%) ranged from 0.69 to 0.82. The overall accuracy of predicting the histological grade of steatosis using MRI-PDFF was 56%. Diagnostic accuracy decreased in the presence of pronounced fibrotic changes [31].

Application in clinical practice is limited due to the high cost and low availability of the method.

2.4.2 Diagnosis of steatohepatitis

Comments: due to the invasiveness of the method and the possibility of complications, the practical application of the study is limited and is performed when the disease progresses and in diagnostically unclear cases [6, 11, 23].

Ultrasound-guided liver biopsy should not be performed in MASLD in the form of simple steatosis detected during instrumental examination, in the absence of "alarm" symptoms, normal biochemical parameters, and absence of signs of progressive course (fibrosis) according to non-invasive methods (biomarkers (determination of ALT, AST, GGT activity), elastography (liver elastometry)).

During the pathological-anatomical examination of a liver biopsy specimen, the presence and severity of steatosis, inflammation, and fibrosis are evaluated. Ultrasound-guided liver biopsy in a number of cases makes it possible to detect/exclude other causes of liver damage.

The severity of steatosis is assessed by the proportion (%) of hepatocytes containing macrovesicular fat droplets upon hematoxylin and eosin staining: grade 0 - < 5%; grade 1 - 5–33%; grade 2 - 34–66%; and grade 3 - > 66% [33].

The morphological picture of steatohepatitis in MASLD in children is characterized by the following changes:

o inflammation is predominantly portal in nature,

o steatosis may have a periportal distribution, is localized in acinar zone 3 or panacinar,

o ballooning degeneration is rare [34].

o with the progression of steatohepatitis, intralobular inflammation with hepatocyte damage appears.

Liver biopsy currently remains the reference standard for the diagnosis of MASH in patients with MASLD. In the absence of histological (pathological-anatomical) examination of liver tissue, but convincing data from non-invasive tests regarding a progressive course of the disease (e.g., elevated surrogate markers of inflammation - transaminases (AST, ALT), data from non-invasive methods indicating fibrosis, etc.), it is permissible, according to experts working with adult patients, to establish the diagnosis of "Probable MASH" [22].

There are differences in the histological (pathological-anatomical) picture of MASLD in preschool, early school-age children, and adolescents/adults. Preschool and early school-age children are not characterized by ballooning degeneration of hepatocytes, but rather by a predominance of portal rather than lobular inflammation and slow disease progression with the development of fibrosis [4].

2.4.3 Diagnosis of fibrosis

In children, MASLD in the form of simple steatosis is characterized by a slowly progressive course with a prolonged absence of signs of fibrosis. Determining the stage of fibrosis is relevant for patients with MASH and type 1 pediatric steatotic/fatty liver disease [6, 34].

Comments: transient elastography (liver elastometry) is the most widely used study to determine the stiffness of liver tissue. The method is based on a comparative assessment of the stiffness of normal and pathologically altered organ tissue. When comparing liver elasticity indicators according to transient elastography with the results of morphological assessment of the degree of fibrosis using the METAVIR scale, the following rating scale was obtained [35]:

o 5.9–7.2 kPa interval – F1 fibrosis stage (mild fibrosis)

o 7.3–9.5 kPa interval – F2 fibrosis stage (moderate fibrosis)

o 9.6–12.5 kPa interval – F3 fibrosis stage (severe fibrosis)

o Values greater than 12.5 kPa – F4 fibrosis stage (cirrhosis)

The sensitivity and specificity of the method increase as the degree of fibrosis progresses. At fibrosis stage F3, sensitivity and specificity approach 90% [11, 35]. The results of transient elastography (liver elastometry) can be affected by inflammation activity; results are unreliable when ALT levels are high.

Comments: liver tissue stiffness measurements obtained using shear wave techniques available on modern ultrasound systems are comparable in accuracy to transient elastography (liver elastometry), although data on patients with MASLD are limited [11].

2.4.4 Other methods for assessing fibrosis

Non-invasive non-patented tests are used in patients with MASLD primarily in adult practice to rule out advanced fibrosis and cirrhosis and are not validated in pediatrics [36]. Pediatric scores such as PNFI and PNFS exist and are used mainly in clinical trials; currently, there is no conclusive evidence regarding their efficacy in clinical practice [39].

2.5 Other Procedures

Comments: see red flag symptoms in Section 2 "Criteria for Establishing Diagnosis/Condition" [6, 20].

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

The main objectives of MASLD therapy include:

1. Prevention of liver disease progression and regression of existing steatosis, steatohepatitis, and fibrosis.

2. Reduction of cardiometabolic risk factors (correction of overweight to improve dyslipidemia, insulin resistance, and blood pressure), which are closely associated with MASLD [7, 11].

Treatment of MASLD includes non-pharmacological methods (diet and physical activity), which are fundamental, as well as pharmacotherapy [1, 20].

3.1 Non-pharmacological therapy

• As first-line therapy, lifestyle modification and dietary correction (adhering to balanced nutrition standards tailored to age characteristics and increasing physical activity) are recommended for children with MASLD [1, 5, 10, 11].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comments: the primary focus of therapy is reducing or stabilizing BMI SDS through dietary therapy and exercise [1, 11]. The combination of physical activity and dietary therapy leads to a significant reduction in subcutaneous and intrahepatic fat, lowered ALT levels, and improvement in the histological (pathological-anatomical) picture of the liver in children and adolescents with MASLD [41].

Since parents serve as role models for a child, lifestyle modifications should affect not only the patients but also their immediate environment—their family members. It is important to consider the diet and physical activity levels of parents for comprehensive work with children and adolescents.

3.1.1 Physical activity

• Regular physical activity in the form of aerobic exercise and strength training, tailored to examination results and supervised by specialists, is recommended for patients with MASLD and comorbid conditions to reduce liver fat content [1, 42].

Level of Evidence AGrade of Recommendation 1Level of Recommendation A (Level of Evidence — 1)

Comments: moderate- to high-intensity aerobic exercise and strength training for at least 60 minutes a day, three times a week, lead to a reduction in visceral and liver fat [5, 42].

Examples of moderate-intensity physical activity: brisk walking, dancing, gardening, housework and chores, active games and sports, walking pets, etc.

Examples of high-intensity physical activity: running, aerobics, fast cycling, uphill hiking, etc. [43].

Physical activity recommendations must take into account the patient's individual characteristics (age, physical fitness) and comorbid conditions. Sedentary children and adolescents should start with low physical loads and gradually increase their frequency, intensity, and duration. Systematic reviews have established that resistance training (strength training) may be preferable to aerobic exercise in patients with MASLD and low cardiorespiratory fitness or in those who poorly tolerate aerobic exercise [44].

Comments: Reducing children's screen time to less than 2 hours a day aims to correct a sedentary lifestyle and increase physical activity [45].

3.1.2 Diet

Dietary therapy is one of the effective non-pharmacological treatments for both MASLD and overweight/obesity [1, 11].

• Dietary therapy is recommended for children and adolescents with MASLD to achieve weight reduction and stabilization, normalization of metabolic processes, and prevention of cardiometabolic risks [46].

LeveL of Recommendation BGrade of Evidence 2LeveL of Recommendation B (Grade of Evidence - 2)

Comments: Currently, there is no conclusive evidence confirming the superiority of any specific diet in the treatment of MASLD (e.g., low-glycemic index or low-fat diets). The primary requirement for dietary recommendations is adherence to the physiological macronutrient and micronutrient needs of children according to age, in order to prevent deficiency states [1].

General principles of dietary therapy include:

o Regular meals, 4–5 meals a day consisting of 3 main meals and 1–2 snacks;

o Incorporation of vegetables (300 g/day for young children, 400 g/day for adolescents, excluding potatoes from this volume), dietary fiber, and whole-grain products into the diet;

o Formation of proper eating behavior – eating slowly, not "on the run," and without electronic gadgets that distract from the meal [47].

• Children with MASLD are recommended to avoid foods and beverages containing added fructose or other easily digestible carbohydrates to reduce hepatic fat accumulation [48, 49, 50, 79].

GCR ALeE 2Grade of Recommendation A (Level of Evidence - 2)

Comments: consumption of added fructose (found predominantly in sugar-sweetened beverages) leads to a significant increase in liver fat and elevated ALT levels. The negative effect of added fructose is caused by:

1) increased dietary caloric density,

2) specific features of fructose metabolism.

Unlike glucose, fructose is more readily converted into fatty acids due to the upregulation of lipogenic enzymes in the liver [49, 51, 79]. Fructose metabolism differs between children with MASLD and healthy children with normal body weight: children with MASLD exhibit increased fructose absorption and more pronounced metabolic shifts in response to dietary fructose intake [49]. Natural sources of fructose (honey, fruits, dried fruits), provided that the diet's energy value is appropriate, have no negative impact on the course of MASLD [51].

3.2 Pharmacological therapy for MASLD

Currently, despite the progress made in understanding the pathogenesis, clinical features, and prognosis of MASLD, the indications for pharmacotherapy are still under discussion. In addition, drug therapy may be used in the comprehensive treatment of comorbid conditions.

Comments: the results of most available studies were obtained in small patient groups and are contradictory and inconclusive, since the evaluation of drug efficacy was based primarily on determining the dynamics of ALT levels after a short-term intervention [1].

Comments: the option of prescribing drug therapy, especially in comorbid pathology, is provided in cases where lifestyle modification alone is insufficiently effective and/or the disease has a progressive course. This is due to the fact that the effectiveness of lifestyle modification remains low. According to studies, less than 10% of patients achieve weight loss within a year, and less than half of them maintain the achieved result for five years [31].

Comments: the potential of UDCA** in reversing liver damage in children with MASLD requires further investigation.

o with concomitant biliary dysfunction,

o biliary sludge,

o at the stage of weight loss, when the risk of gallstone formation increases.

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

• In patients aged 12 years and older with MASLD and obesity, it is recommended to selectively use glucagon-like peptide-1 (GLP-1) receptor agonists as subcutaneous liraglutide (ATX code A10BJ02) (per instructions) for weight loss, reduction of IR, and signs of inflammation and liver injury [81].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

Comments: a general positive effect of GLP-1 analogues is significant weight loss, which helps reduce liver damage in MASLD and lowers the risks of cardiovascular events and renal complications.

It is important to emphasize that according to the 2024 clinical guidelines for childhood obesity, liraglutide may be prescribed "when interventions aimed at promoting a healthy lifestyle lasting at least 1 year are ineffective" [90].

3.4 Surgical treatment

• Bariatric surgery is not recommended as a specific therapy for MASLD in children due to the lack of long-term surgical outcome data [67].

LeveL of Recommendation BGrade of Evidence 3LeveL of Recommendation B (Grade of Evidence - 3)

Comments: indications and the method of bariatric intervention should be determined on an individual basis by a multidisciplinary team, including a pediatric surgeon.

3.5 Other treatments

Comments: whenever possible, work is also carried out with members of the child's family.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

Specific rehabilitation measures for patients with MASLD are lacking. Sanatorium-resort treatment in the "Gastroenterology" profile may be used.

Comments: the most beneficial for liver metabolism are: bicarbonate-rich mineral waters, which neutralize dietary acid stress, improve insulin sensitivity, and lower lipid/cholesterol levels [86]; calcium-magnesium sulfate waters, which promote bile secretion and improve the gut microbiome, which is critical for regulating the gut-liver axis.

Inpatient medical rehabilitation is carried out in multidisciplinary medical rehabilitation departments or medical rehabilitation departments for children with somatic pathology.

5. Prevention and Dispensary Observation

5.1 Prevention

Preventive measures for MASLD are aimed at:

- preventing the development of MASLD;

- timely detection of MASLD and MASH;

- preventing the progression of MASLD/MASH to liver cirrhosis [1, 11].

5.1.1 Prevention of MASLD development

5.1.2 Timely detection of MASLD and MASH

Comments: Type 2 diabetes and other cardiometabolic risk factors contribute to the progressive course of MASLD and the development of MASH. Approximately a quarter of patients with established MASH progress to cirrhosis with the risk of developing HCC [70]. According to experts, in patients with type 2 diabetes or several cardiometabolic risk factors, the assessment of potential fibrosis development/progression should be performed every 1-2 years [24].

At a younger age, screening may be performed selectively at the discretion of the physician.

5.1.3 Prevention of MASLD/MASH progression to liver cirrhosis

• Children with MASLD are recommended lifestyle modifications (dietary correction excluding sugar-sweetened beverages, increased physical activity with reduced screen time) to prevent MASLD progression, including through the use of family-based rehabilitation and psychological counseling programs [1, 41, 52].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

Comments: lifestyle modification measures, discussed in detail in Section 3.1. "Non-pharmacological therapy", serve not only for the treatment of MASLD, but also represent the most effective measure for preventing its onset and progression, as well as having a positive impact on most comorbid conditions [43, 52].

• Patients with MASLD are recommended pharmacological and non-pharmacological management of comorbid conditions to prevent the progressive course of MASLD [34].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comments: MASLD and many comorbid diseases exacerbate each other's course (e.g., arterial hypertension, chronic kidney disease). This suggests that managing comorbid conditions can have a positive effect on preventing an adverse course of MASLD [11].

5.2 Dispensary monitoring

• Children with MASLD without signs (laboratory or instrumental) of a progressive course/fibrosis, and without clinical manifestations of metabolic syndrome, are recommended follow-up outpatient visits (examination, consultation) by a pediatrician/general practitioner (family physician)/initial and follow-up consultations by a gastroenterologist once every 2 years, including determination of blood ALT and AST activity, as well as imaging methods (comprehensive ultrasound of the abdominal organs, hepatobiliary ultrasound elastography (liver elastometry) or magnetic resonance imaging of the liver, depending on indications and availability at the medical facility) with assessment of liver fibrosis signs for the timely detection of disease progression, as indicated [1].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comments: the optimal frequency of follow-up care has not been established, but according to European experts, patients with MASLD without laboratory or instrumental signs of progressive disease should be monitored once every 2 years [1, 5].

• Patients with MASLD who have prediabetes, type 2 diabetes mellitus, and more than two cardiometabolic risk factors are recommended regular follow-up (follow-up outpatient visit (examination, consultation) by a pediatrician/general practitioner (family physician), initial and follow-up consultations by a gastroenterologist, initial and follow-up consultations by a pediatric endocrinologist) — once a year, utilizing imaging methods (comprehensive ultrasound of the abdominal organs, hepatobiliary ultrasound elastography (liver elastometry) or magnetic resonance imaging of the liver, depending on indications and availability at the medical facility) with assessment of liver fibrosis signs for the timely detection of disease progression [1].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

6. Organization of Medical Care

Depending on their needs, patients with MASLD may receive any type, conditions, and form of medical care provided for by the legislation of the Russian Federation.

The majority of patients with MASLD are subject to outpatient monitoring and treatment.

Indications for planned hospitalization of patients with MASLD:

o lack of response to outpatient treatment or atypical disease course;

o need for diagnostic procedures that cannot be performed in an outpatient setting (e.g., imaging methods using anesthesia (including early postoperative management) in young children, ultrasound-guided liver biopsy);

o need for differential diagnostic procedures to rule out other causes of liver damage that cannot be performed in an outpatient setting;

o combination of MASLD with manifestations of metabolic syndrome that complicate the course of the disease and require multidisciplinary management and/or round-the-clock monitoring.

The organization of dietary nutrition for patients receiving inpatient care in medical organizations is carried out in accordance with Appendix 3 of the Order of the Russian Ministry of Health No. 1008n dated September 23, 2020, "On approval of the procedure for providing patients with therapeutic nutrition".

Indications for patient discharge from a medical organization:

1. completion of the course of treatment or one of the stages of specialized medical care (including establishing a diagnosis) in a 24-hour or day hospital setting, provided there are no treatment complications requiring drug correction and/or inpatient medical interventions;

2. refusal of specialized medical care in a 24-hour or day hospital setting by the patient or their legal representative;

3. necessity of transferring the patient to another medical organization of the appropriate medical profile. The conclusion on the feasibility of transferring a patient to a specialized medical organization is made following a preliminary consultation based on provided medical documents, a telemedicine consultation, and/or a preliminary examination of the patient by specialist physicians of the planned receiving medical organization.

7. Additional Information

To reduce the risk of MASLD progression and complication development, early detection of the disease and correction of metabolic risk factors are crucial.

Further research, particularly in the field of long-term follow-up and the development of effective therapeutic strategies, is needed for more accurate prognosis and the formulation of individualized treatment approaches.

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

Baranov Aleksandr Aleksandrovich - Academician of the RAS, Professor, Doctor of Medical Sciences; Honorary President of the Union of Pediatrists of Russia, Advisor to the Head of the Research Institute of Pediatrics and Child Health at the Petrovsky National Research Centre of Surgery (NCC No. 2), Professor at the Department of Pediatrics and Pediatric Rheumatology, I.M. Sechenov First Moscow State Medical University of the Ministry of Health of Russia (Sechenov University), Chief freelance pediatric specialist of the Russian Ministry of Health.

Bokova Tatyana Alekseevna - Doctor of Medical Sciences, Associate Professor, Head of the Department of Children's Diseases, Head of the Pediatrics Department, Moscow Regional Research Clinical Institute named after M.F. Vladimirsky (MONIKI). No conflict of interest.

Volynets Galina Vasilevna - Doctor of Medical Sciences, Head of the Department of Gastroenterology at the Veltischev Research and Clinical Institute of Pediatrics and Pediatric Surgery, Pirogov Russian National Research Medical University (RNRMU), Professor at the Department of Innovative Pediatrics and Pediatric Surgery, Faculty of Additional Professional Education, Pirogov Russian National Research Medical University of the Ministry of Health of Russia, Associate Professor at the Department of Pediatrics with Infectious Diseases in Children, Faculty of Additional Professional Education, Pirogov Russian National Research Medical University of the Ministry of Health of Russia. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists. Member of the Union of Pediatrists of Russia. Member of the Euro-Asian Society for Infectious Diseases. No conflict of interest.

Vlasov Nikolay Nikolaevich - Candidate of Medical Sciences, Associate Professor at the Department of Children's Diseases named after Professor I.M. Vorontsov, Faculty of Postgraduate and Additional Professional Education, St. Petersburg State Pediatric Medical University of the Ministry of Health of Russia. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists.

Goryacheva Larisa Georgievna - Doctor of Medical Sciences, Professor at the Department of Infectious Diseases in Children, Faculty of Postgraduate and Additional Professional Education, St. Petersburg State Pediatric Medical University of the Ministry of Health of Russia. Leading Researcher at the Department of Viral Hepatitis and Liver Diseases, Children's Scientific and Clinical Center of Infectious Diseases of the Federal Medical-Biological Agency. Member of the Union of Pediatrists of Russia. No conflict of interest.

Gurova Margarita Mikhailovna - Doctor of Medical Sciences, Professor at the Department of Propaedeutics of Children's Diseases, St. Petersburg State Pediatric Medical University of the Ministry of Health of Russia. Leading Researcher at the Laboratory of Medical and Social Problems, Research Center in Pediatrics, St. Petersburg State Pediatric Medical University of the Ministry of Health of Russia, Academician of the International Academy of Ecology and Life Protection Sciences (MANEB). Professor at the Department of Pediatrics, Medical Institute, Belgorod State National Research University. Deputy Chief Medical Officer for Medical Affairs, St. Petersburg Consultative and Diagnostic Center for Children. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists of Russia. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists. Member of the League of Physicians of the North-West. No conflict of interest.

Greshnyakova Vera Aleksandrovna - Researcher at the Department of Viral Hepatitis and Liver Diseases, Children's Scientific and Clinical Center of Infectious Diseases of the Federal Medical-Biological Agency. Member of the Union of Pediatrists of Russia. No conflict of interest.

Zavyalova Anna Nikitishna - Doctor of Medical Sciences, Professor at the Department of Propaedeutics of Children's Diseases with a Course in General Patient Care. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists of Russia. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists. Member of the League of Physicians of the North-West. No conflict of interest.

Evdokimova Nina Viktorovna - Candidate of Medical Sciences, Assistant at the Department of Propaedeutics of Children's Diseases with a Course in General Patient Care, St. Petersburg State Pediatric Medical University of the Ministry of Health of Russia. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists. Member of the League of Physicians of the North-West. No conflict of interest.

Komissarova Marina Yurievna - Candidate of Medical Sciences, Deputy Chief Medical Officer for Clinical and Expert Work, L.M. Roshal Children's Scientific and Clinical Center. Member of the Union of Pediatrists of Russia. Member of the League of Physicians of the North-West. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists. No conflict of interest.

Namazova-Baranova Leyla Seymurovna - Academician of the RAS, Professor, Doctor of Medical Sciences, President of the Union of Pediatrists of Russia; Past-President of EPA/UNEPSA; Head of the Research Institute of Pediatrics and Child Health at the Petrovsky National Research Centre of Surgery (NCC No. 2), Head of the Department of Faculty Pediatrics, Pediatric Faculty, Pirogov Russian National Research Medical University of the Ministry of Health of Russia, Chief freelance pediatric specialist in preventive medicine of the Russian Ministry of Health. No conflict of interest.

Novikova Valeria Pavlovna - Doctor of Medical Sciences, Professor, Head of the Department of Propaedeutics of Children's Diseases with a Course in General Patient Care, Head of the Laboratory of Medical and Social Problems, Research Center in Pediatrics, Academician of the International Academy of Ecology and Life Protection Sciences (MANEB). Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists of Russia. Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists. Chair of the League of Physicians of the North-West. No conflict of interest.

Pavlovskaya Elena Vyacheslavovna - Doctor of Medical Sciences, Leading Researcher at the Department of Pediatric Gastroenterology, Hepatology, and Dietotherapy, Federal Research Centre of Nutrition and Biotechnology, Professor at the Department of Dietology and Nutrition, Russian Medical Academy of Continuous Professional Education (RMANPO). Member of the Association of Pediatric Gastroenterologists, Hepatologists, and Nutritionists. No conflict of interest.

Potapov Aleksandr Sergeevich - Doctor of Medical Sciences, Professor, Head of the Center for Inflammatory Bowel Diseases in Children, National Medical Research Center for Children's Health of the Ministry of Health of Russia; Professor at the Department of Pediatrics and Pediatric Rheumatology, I.M. Sechenov First Moscow State Medical University (Sechenov University).

Rogozina Nataliya Vasilyevna - Candidate of Medical Sciences, Associate Professor at the Department of Infectious Diseases in Children, Faculty of Postgraduate and Additional Professional Education, St. Petersburg State Pediatric Medical University of the Ministry of Health of Russia. Member of the Union of Pediatrists of Russia. No conflict of interest.

Strokova Tatiana Viktorovna — MD, Professor of the Russian Academy of Sciences, Head of the Department of Pediatric Gastroenterology, Hepatology and Dietotherapy at the Clinic of the Federal Research Centre of Nutrition and Biotechnology, Head of the Department of Gastroenterology and Dietology at Pirogov Russian National Research Medical University. Member of the Russian Society of Pediatric Gastroenterologists, Hepatologists and Nutritionists. Member of the Union of Pediatricians of Russia. No conflict of interest.

Surkov Andrey Nikolaevich — MD, Head of the Gastroenterology Department for Children at the Children's Hospital, Head of the Department of Scientific Foundations of Pediatric Gastroenterology, Hepatology and Metabolic Disorders at the Research Institute of Pediatrics and Child Health of the Academician B.V. Petrovsky National Research Centre of Surgery, Professor at the Department of Faculty Pediatrics, Pediatric Faculty, Pirogov Russian National Research Medical University of the Russian Ministry of Health. Member of the Union of Pediatricians of Russia. No conflict of interest.

Khavkin Anatoly Ilyich — MD, Professor, Head of the Moscow Regional Center for Pediatric Gastroenterology and Hepatology at the Research Clinical Institute of Childhood of the Ministry of Health of the Moscow Region; Professor at the Department of Pediatrics with a Course of Pediatric Surgical Diseases at the Medical Institute of Belgorod State National Research University. Chairman of the Society of Pediatric Gastroenterologists, Hepatologists and Nutritionists. No conflict of interest.

Appendix A2. Methodology for Developing Clinical Guidelines

The proposed guidelines aim to provide practicing physicians with current concepts on the etiology and pathogenesis of MASLD, and to introduce currently used algorithms for diagnosis, prognosis assessment, and treatment.

Target audience of these clinical guidelines:

1. Gastroenterologists

2. General practitioners (family physicians)

3. Pediatricians

4. Pediatric cardiologists

5. Pediatric endocrinologists;

Table 3. Levels of Evidence (LE) rating scale for diagnostic methods (diagnostic interventions)

Table 4. Scale for assessing the levels of evidence (LE) for methods of prevention, treatment, and medical rehabilitation, including those based on natural therapeutic factors (preventive, therapeutic, and rehabilitative interventions)

Table 5. Scale for assessing the grades of recommendation (GR) for methods of prevention, diagnosis, treatment, and medical rehabilitation, including those based on natural therapeutic factors (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Procedure for updating clinical guidelines

The update mechanism for clinical guidelines provides for their systematic revision—at least once every three years, as well as upon the emergence of new evidence-based data regarding the diagnosis, treatment, prevention, and rehabilitation of specific conditions, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

These clinical guidelines have been developed taking into account the following regulatory and legal documents:

1. Order of the Ministry of Health and Social Development of the Russian Federation No. 906n dated November 12, 2012, "On Approval of the Procedure for Providing Medical Care to the Population in the Field of Gastroenterology";

2. Order of the Russian Ministry of Health No. 120n dated February 20, 2026, "On Approval of the Procedure for Providing Medical Care in the Field of Pediatrics";

3. Order of the Russian Ministry of Health No. 1094n dated November 24, 2021, "On Approval of the Procedure for Prescribing Medicinal Products, Prescription Form Templates for Medicinal Products, the Procedure for Issuing These Forms, Their Accounting and Storage, Templates of Prescription Forms Containing Prescriptions for Narcotic Drugs or Psychotropic Substances, the Procedure for Their Manufacture, Distribution, Registration, Accounting and Storage, as well as the Rules for Issuing Prescription Forms, Including in the Form of Electronic Documents";

4. International Statistical Classification of Diseases and Related Health Problems (ICD-10);

5. Order of the Russian Ministry of Health No. 205n dated May 2, 2023, "On Approval of the Nomenclature of Positions of Medical Workers and Pharmaceutical Workers" (Registered with the Ministry of Justice of Russia on June 1, 2023, No. 73664);

6. Order of the Ministry of Health of the Russian Federation No. 541n dated July 23, 2010. Unified Qualification Handbook of Positions of Managers, Specialists, and Employees, section Qualification Characteristics of Healthcare Sector Employee Positions;

7. Federal Law No. 489-FZ dated December 25, 2018, "On Amendments to Article 40 of the Federal Law 'On Compulsory Health Insurance in the Russian Federation' and the Federal Law 'On the Basics of Protecting the Health of Citizens in the Russian Federation' Regarding Clinical Guidelines";

8. Order of the Russian Ministry of Health No. 103n dated February 28, 2019, "On Approval of the Procedure and Timelines for the Development of Clinical Practice Guidelines, Their Revision, Standard Template of Clinical Practice Guidelines and Requirements for Their Structure, Composition and Scientific Validity of Information Included in Clinical Practice Guidelines";

9. Order of the Russian Ministry of Health No. 804n dated October 13, 2017, "On Approval of the Nomenclature of Medical Services".

Appendix A3.1 Differential diagnosis of MASLD

When detecting signs of hepatic steatosis in patients under 10 years of age, congenital metabolic disorders must be excluded (alpha-1 antitrypsin deficiency, cystic fibrosis, galactosemia, type 1 tyrosinemia, peroxisomal oxidation disorders, Wilson's disease, abetalipoproteinemia, hypobetalipoproteinemia, congenital lipodystrophy, familial hyperlipidemia, lysosomal acid lipase deficiency, acid sphingomyelinase deficiency, type 2 citrullinemia, etc.) [5, 10].

Table. Conditions that may be accompanied by hepatic steatosis and/or transaminasemia [1, 4, 19]

Appendix B. Physician Action Algorithms

Fig. 1. Algorithm for the diagnosis of MASLD in children.

Appendix C. Patient Information

Key to success in the treatment of MASLD:

● healthy diet

● physical activity

❖ Reduce the size of your portions, eat frequently if possible, but in small portions.

❖ Exclude foods rich in simple carbohydrates (sweets, flour products) from your regular diet and try to consume them occasionally and in small amounts.

❖ Try to eat vegetables and fruits several times a day.

❖ Replace sweet and carbonated beverages with water or unsweetened drinks.

❖ Eat high-fiber foods, including whole grains.

❖ Avoid saturated fats, use extra virgin olive oil as the main added source of fat in meals.

❖ Eat fish 2–3 times a week.

❖ Avoid processed foods and fast food.

❖ Read food labels to check for hidden fats, sugar, and sodium.

❖ Try to engage in some form of physical activity for at least 60 minutes a day. This does not have to be all at once. Walk more, exercise, and take the stairs whenever possible.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

Appendix G1. NAS scale (NAFLD activity score — NAS)

[71].

Russian name: NAFLD activity scale¹ .

Original name (if applicable): NAFLD activity score — NAS1.

Source (official developer website, validation study): CRN (Clinical Research Network) expert morphologist consensus, 2005 [Kleiner DE, Brunt EM, Van Natta M, Behling C, Contos MJ, Cummings OW, Ferrell LD, Liu YC, Torbenson MS, Unalp-Arida A, Yeh M, McCullough AJ, Sanyal AJ; Nonalcoholic Steatohepatitis Clinical Research Network. Design and validation of a histological scoring system for nonalcoholic fatty liver disease. Hepatology. 2005 Jun;41(6):1313-21. doi: 10.1002/hep.20701. PMID: 15915461.]

Type (underline):

- assessment scale

- score

- questionnaire

other (specify):

Purpose: for semi-quantitative assessment of the severity and stage of NAFLD.

Contents (template): the scale assesses the degree of morphological changes in scores (from 0 to 8): the severity of liver steatosis, intralobular (lobular) inflammation, hepatocyte ballooning degeneration, and the stage of fibrosis.

Key (interpretation):

• NAS 0–2: MASH diagnosis is unlikely;

• NAS 3–4: "grey zone", NASH/MASH may be present in the patient;

• NAS ≥ 5: NASH/MASH diagnosis is probable.

Notes:

^{1 -} NAFLD (non-alcoholic fatty liver disease) is an obsolete term; the currently accepted term is MAFLD (metabolically associated fatty liver disease). It is mentioned in these clinical guidelines within the scales because they were developed before the terminology change.

^{2 -} Presence of inflammatory infiltrate cell clusters at 20x magnification.

Appendix G2. SAF scale (steatosis, activity, and fibrosis score)

[72].

Russian name: Scale for semi-quantitative assessment of NAFLD severity¹.

Original name (if applicable): SAF score (steatosis, activity, and fibrosis score).

Source (official developer website, validation study): [FLIP pathology consortium, 2014. Bedossa P. FLIP Pathology Consortium. Utility and appropriateness of the fatty liver inhibition of progression (FLIP) algorithm and steatosis, activity, and fibrosis (SAF) score in the evaluation of biopsies of nonalcoholic fatty liver disease // Hepatology. 2014. Vol. 60, № 2. Р. 565-75., Li X, Wang S, Zhang Z, Deng W, Zhang Y, Cao W, Wei X, Gao Z, Yao L, Wang S, Yi W, Xie Y, Li M. Exploring the severity and risk factors of non-alcoholic fatty liver disease using the SAF scoring system. Front Med (Lausanne). 2025 Mar 28;12:1510679. doi: 10.3389/fmed.2025.1510679. PMID: 40224639; PMCID: PMC11985763].

Type (underline):

- assessment scale

- score

- questionnaire

-  other (specify):________________________________________________________________

Purpose: for semi-quantitative assessment of NAFLD severity¹.

Contents (template): the scale includes histological (pathoanatomical) characteristics of NAFLD such as the severity of steatosis (S), ballooning degeneration and lobular inflammation (A, activity), and the stage of liver fibrosis (F, fibrosis).

*the presence of (sub)total liver steatosis in young patients, especially without signs of metabolic syndrome, requires evaluation of lysosomal acid lipase activity to rule out cholesteryl ester storage disease/Wolman disease or screening the patient for Wilson's disease. A rarer cause may be carriage of recessive mutations in the POLG, DGUOK, or MPV17 genes characteristic of mitochondrial disorders.

Interpretation key: the assessment result is recorded as an index such as S1A2F3, S2A1F1, etc.

Notes:

^{1 –} NAFLD (non-alcoholic fatty liver disease) is an obsolete term; the currently accepted term is MAFLD (metabolically associated fatty liver disease). It is mentioned in these clinical guidelines within the scales because they were developed before the terminology change.