• Clinical science

Congenital visceral malformations

Abstract

Congenital visceral malformations develop during organogenesis, which occurs in the first 8 weeks after conception (embryonal period). Common malformations include anal atresia, omphalocele, gastroschisis, and biliary atresia. They may occur on their own or together with other malformations and syndromes. Anal atresia is characterized by an absent anal opening and failure to pass meconium, which may lead to an ileus or the formation of fistulas. An omphalocele is often associated with trisomies and manifests with the herniation of abdominal viscera through the abdominal wall into a hernia sac. In cases of gastroschisis, by contrast, herniated parts of the intestine are not covered by a sac, but exposed. All three conditions are clinical diagnoses and require surgery to prevent infections and further complications. In extrahepatic biliary atresia, the infant presents with prolonged neonatal jaundice, acholic stools, dark urine, and hepatomegaly. Conjugated hyperbilirubinemia and abnormalities on ultrasonography provide valuable clues for diagnosis. If extrahepatic biliary atresia remains undetected or surgery is delayed, the infant may die within the first two years of life, usually as a result of biliary liver cirrhosis.

Anal atresia

  • Definition: sporadically occurring malformation of the rectum with absence of an anal opening
  • Epidemiology
  • Clinical features
    • Flat bottom (no or poorly developed midline groove between buttocks), absence of anal opening, small or missing anal dimple
    • Thin anal membrane in place of anal opening through which meconium is visible; possible bucket-handle malformation
    • Patients may present with obstipation and ileus; , or develop fistulas which enable limited defecation (e.g., rectourethral, rectovaginal).
  • Diagnosis
    • Clinical diagnosis
    • Lateral pelvic radiography to determine position of the rectal pouch
    • Fistula screening
      • Examination of the genital area and the urethra (e.g., abdominal ultrasound)
      • Urinanalysis: meconium detectable in case of a rectourinary fistula
      • Augmented-pressure distal colostography to reveal fistulas.
    • Investigation of additional malformations (e.g., spinal ultrasonography, sacral x-ray)
  • Treatment
    • IV hydration, no oral feeding
    • Anal reconstructive surgery (primary anoplasty) or temporary colostomy in more complex malformations

References:[1][2][3][4]

Omphalocele

  • Definition: congenital herniation of abdominal viscera through the abdominal wall at the umbilicus; the hernia sac is covered by the amniotic membrane and the peritoneum
  • Pathophysiology: failed return of the midgut to the abdominal cavity
  • Epidemiology
  • Clinical features
  • Diagnosis
  • Complications: rupture of hernia sac with infection (peritonitis); secondary intestinal wall atresia as a result of injury
  • Treatment
    • Cesarean section to prevent rupture of the sac
    • Wrapping of the hernia sac with sterile saline dressings covered with plastic wrap
    • Nasogastric suction; and administration of IV fluids to avoid abdominal distention and to compensate fluid loss
    • Surgery (within the first 24 h of life): usually primary abdominal wall closure
      • Primary abdominal wall closure
      • Alternative: secondary closure after
  • Prognosis: dependent on the size of the defect and birth weight; survival rate over 90% in the absence of additional malformations

References:[5][6][7][8]

Gastroschisis

  • Definition: paraumbilical herniation of the intestine through the abdominal wall without formation of a hernia sac
  • Epidemiology: approx. 1:2,000 live births in the US
  • Pathophysiology
    • Failed formation of a sufficiently large peritoneal cavity → growing bowel leads to rupture of the anterior abdominal wall at its weakest point herniation of bowel sections
    • Because the malformation occurs relatively late in development, additional anomalies are rarely present (in contrast to omphalocele)
  • Clinical features
  • Diagnosis
    • Usually a clinical diagnosis!
    • Can be detected prenatally (see “Diagnosis” of omphalocele above)
  • Treatment
    • Cesarean delivery has no advantage over vaginal delivery
    • See “Treatment” of omphalocele above
    • Emergency surgery
      • Primary abdominal wall closure (success rate of 70%)
      • Alternative: staged silo repair (see “Treatment” of omphalocele above)
  • Prognosis
    • Survival rates generally good (> 90%)
    • Short bowel syndrome is a common complication
    • 20% of children develop necrotizing enterocolitis

Unlike in cases of omphalocele, gastroschisis does not manifest with a hernia sac!
References:[5][6][9][10][11]

Biliary tract malformations

Biliary atresia

  • Definition: obliteration or discontinuity of the extrahepatic biliary system, most commonly of the common bile duct
  • Epidemiology: approx. 1/10,000–15,000 live births in the US; >
  • Etiology
    • Exact etiology unknown, most likely an embryonal malformation or acquired lesion
    • Approx. 10–35% of cases involve additional anatomical malformations (e.g., situs inversus, asplenia, polysplenia, cardiac anomalies)
  • Pathophysiology: : obliteration or discontinuity of the biliary system → obstruction to bile flow (cholestasis) → secondary biliary cirrhosis and portal hypertension
  • Clinical features
  • Diagnosis
    • Laboratory analysis: conjugated hyperbilirubinemia; , mild/moderate increase in aminotransferases and alkaline phosphatase, increased GGTP
    • Ultrasonography: absence of the gallbladder; no dilatation of the biliary tree
    • Liver biopsy: active inflammation with bile duct degeneration and fibrosis
    • Hepatobiliary scintiscanning (HBSS): failed excretion of the tracer into the bowel
    • To establish definite diagnosis: intraoperative cholangiography
  • Treatment
  • Complications

Intrahepatic biliary hypoplasia (Alagille syndrome)

References:[12][13][14][15]