Functional disorders

Features of biliary dysfunction in children

The primary target of functional disorders in pediatrics is the biliary system. Anatomically, it includes intra- and extrahepatic ducts, vesica biliaris (gallbladder), and the sphincter of Oddi. In the interdigestive period, the orifice of the common duct (ductus choledochus) is closed, bile is retrogradely stored in the gallbladder, and during a meal, it is expelled into the intestine.

In children, this rhythm often fails due to the functional immaturity of neurohumoral regulation. This leads to dyskinesias—disorders of coordinated motility. Predisposing factors include:

• Congenital malformations (e.g., choledochal cyst or Caroli syndrome).
• A positive family history of cholelithiasis.
• Hypodynamia, obesity, regular overeating, and consumption of poor-quality food.
• Initial pathological state of the gastroduodenal zone.

Infection and the "vicious circle" of pathogenesis

The addition of infection significantly exacerbates functional disorders. Pathogens enter the biliary tract via three pathways: hematogenous (from remote foci), lymphogenous (from the intestinal wall), or ascending enterogenic (directly through the ductus choledochus).

Once in the bile ducts, bacterial enzymes disrupt the normal dehydroxylation processes of bile acids. This triggers massive epithelial desquamation and further disrupts the weak neurohumoral regulation of the organ. As a result, a vicious circle is formed:

1. The gallbladder becomes a permanent focus of infection.
2. The pathological process spreads to adjacent structures (stomach, liver, pancreas).
3. Bile formation is disrupted, the passage of secretion and its enterohepatic circulation are impaired.
4. Maldigestion (digestive disorder) develops and the endogenous intoxication syndrome increases.
5. Conditions are created for active gallstone formation.

Functional immaturity of the liver

In addition to biliary motility, the immaturity of the liver's own enzyme systems is a critical factor in functional disorders. Early-age children exhibit high metabolic lability and increased permeability of histohematic barriers. Because of this, toxicoses are extremely severe: toxins easily penetrate tissues (including the central nervous system), causing multiple organ failure.

Transient pigment metabolism disorders are also caused by functional immaturity of the liver. Physiological jaundice is based on:

• Massive hemolysis: the replacement of fetal hemoglobin with adult hemoglobin sharply increases the substrate load.
• Transport deficit: physiological hypoalbuminemia reduces the blood's ability to bind free bilirubin.
• Weak conjugation: low activity of the enzyme UDP-glucuronosyltransferase inhibits the conversion of indirect bilirubin into direct bilirubin.
• Intestinal phase: a deficiency of normal microflora reduces stercobilin production, while the reabsorption of bilirubin from the intestine increases the load on hepatocytes.

Furthermore, in premature and infant children, the activity of vitamin D 25-hydroxylation processes is reduced. This explains why the risk of severe hypervitaminosis D is high at this age, followed by cell membrane damage and suppression of renal excretory function.

Class and exam questions

What else to study on this topic

• Mechanisms of physiological and pathological jaundice in newborns
• Anatomical and genetic anomalies of the bile ducts (Caroli syndrome, choledochal cyst)
• Transient hyperinsulinemia and hypoglycemia syndrome
• The role of the liver in maintaining acid-base balance
• Iatrogenic causes of syndrome of inappropriate antidiuretic hormone secretion

Other topics in the "Additional Topics" section

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