Digestive diseases in children: pathomorphology

Q: Which gastrointestinal malformations are most common in newborns?

The main congenital malformations of the gastrointestinal tract in newborns include: - Esophageal atresia. - Duodenal atresia — the most frequent congenital obstructive lesion of the small intestine. - Atresia and stenosis of the small and large intestine. - Anal atresia. - Meconium peritonitis. Duodenal atresia has an incidence of 1 in 10,000 live births and in 30–40% of cases is associated with trisomy 21 and combined anomalies, including congenital heart disease, urinary system malformations, and other GI malformations.

General pathogenesis of digestive system lesions

In congenital infections (CIs) of viral, parasitic, or bacterial etiology, the pathological process in the digestive organs is frequently triggered hematogenously. The pathogen (e.g., herpesviruses, cytomegalovirus, parvovirus, *Toxoplasma*, *Treponema pallidum*) reaches the fetal liver directly via the umbilical vein. Subsequently, the infection is disseminated to other organs via the bloodstream.

General morphological features of hepatobiliary system and abdominal cavity lesions include:

Early fibrosis of organ stroma.
Extramedullary hematopoiesis (intensive formation of hematopoietic foci in the liver and spleen tissue).
Delayed tissue maturation.
Development of hemorrhagic syndrome.

Macroscopically, these processes manifest as pronounced hepatosplenomegaly (enlargement of the liver and spleen) and jaundice, which accompany intrauterine growth restriction.

Viral infections: hepatitis and sialadenitis

Viruses transmitted transplacentally play a special role in the pathology of the neonatal digestive system.

Congenital rubella Infection occurs during maternal viremia. The virus causes multiple malformations and inflammatory processes. Macroscopically, the hepatobiliary system shows hepatosplenomegaly, while microscopic examination reveals giant cell hepatitis and multiple foci of extramedullary hematopoiesis.

Congenital cytomegaly The risk of fetal infection in seronegative mothers reaches 50%. The pathological anatomy is characterized by specific involvement of the salivary glands and liver. Cytomegaloviral transformation predominantly affects epithelial cells:

Cells increase sharply in size (cytomegalocytes).
The nucleus is displaced eccentrically.
A halo zone forms around the nucleus ("owl-eye" phenomenon).
Eosinophilic inclusions are found inside the nucleus (more rarely in the cytoplasm).

Lymphomacrophage infiltration develops in the stroma of the organs. Clinically, the process manifests with jaundice and hepatosplenomegaly.

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Bacterial and parasitic infections of the GI tract

Various pathogens form a specific morphological picture in the abdominal organs.

Congenital listeriosis: The pathogen Listeria monocytogenes penetrates transplacentally. The most frequent form is granulomatous sepsis. Granulomas (gray-white foci 1–10 mm in size) are localized in the liver, spleen, and intestinal wall. Microscopically, these are foci of necrosis containing gram-positive microbes, surrounded by macrophages, lymphocytes, and leukocytes. In extremely premature infants, the cellular response is absent—only foci of necrosis with an abundance of listeriae are visible in the liver.
Congenital tuberculosis: Characterized by liver and spleen involvement with the formation of large foci of caseous necrosis. Fibrinous peritonitis often develops in the abdominal cavity. A distinctive histological feature in fetuses is the extremely rare formation of epithelioid and Langhans giant cells.
Congenital syphilis: Vasculitis followed by fibrosis develops in the liver and spleen, with the formation of infiltrates composed of plasma cells and lymphoid follicles (early congenital syphilis).
Toxoplasmosis: In addition to classic CNS involvement, microscopic examination of the liver may reveal hepatitis with specific pseudocysts (spherical structures 20–60 µm in size filled with parasites).

Fetal and neonatal sepsis

Intrauterine sepsis also heavily impacts the digestive organs. Characteristic signs of fetal sepsis include pronounced jaundice, persistent hepatosplenomegaly, and splenic myelosis (along with thymic involvement). When the disease develops as septicopyemia, purulent peritonitis becomes one of the most frequent manifestations alongside purulent meningitis.

Briefly: answers to topical questions

Which gastrointestinal malformations are most common in newborns?

The main gastrointestinal malformations in newborns include:

Esophageal atresia.
Duodenal atresia—the most common congenital obstructive lesion of the small intestine.
Atresia and stenosis of the small and large intestine.
Anal atresia.
Meconium peritonitis.

Duodenal atresia has a frequency of 1 in 10,000 live births and is associated in 30–40% of cases with trisomy 21 and combined anomalies, including congenital heart defects, urinary system malformations, and other GI malformations.

What types of peritonitis develop in fetuses and newborns?

Fetuses and newborns can develop fibrinous, purulent, and meconium types of peritonitis.

Fibrinous peritonitis—a macroscopic manifestation of congenital tuberculosis.
Purulent peritonitis—a characteristic manifestation of septicopyemia in intrauterine fetal and neonatal sepsis.
Meconium peritonitis—an intense inflammatory reaction (chemical peritonitis) occurring during intrauterine intestinal perforation and the leakage of sterile meconium, leading to fibrosis and peritoneal calcification.

Class and exam questions

Why is the liver one of the first organs affected in intrauterine infections?

This is due to the characteristics of the hematogenous spread pathway: the pathogen travels from the infected placenta via the umbilical vein directly to the fetal liver, from where it is disseminated to other organs.

What does the liver of a premature infant look like in congenital listeriosis?

Unlike full-term infants, extremely premature fetuses lack a pronounced cellular inflammatory reaction (accumulation of macrophages and lymphocytes). Only foci of necrosis containing numerous *Listeria* bacteria are identified in the liver.

What specific cells are found in the salivary glands in cytomegaly?

Cytomegalocytes—giant epithelial cells with an eccentric nucleus, a surrounding halo zone ("owl-eye" appearance), and eosinophilic inclusions—are found in the salivary glands and liver.

What is the histological feature of tuberculosis involvement of the gastrointestinal tract in the fetus?

In congenital tuberculosis, caseous necrosis predominates in the liver, and fibrinous peritonitis may develop; however, specific Langhans giant cells and epithelioid cells are formed extremely rarely, complicating diagnosis in the absence of bacteriology.

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What else to study on this topic

Pathogenesis of extramedullary hematopoiesis in the fetal liver during infections
Differential morphological diagnostics of giant cell hepatitis
Histology of cytomegaloviral transformation of the salivary gland epithelium
Mechanisms of fibrinous peritonitis development in congenital tuberculosis

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Digestive system diseases in children