Pathophysiology
Summary
Congenital GI disorders encompass a range of conditions that originate from developmental anomalies, affecting various parts of the digestive system and presenting with distinct clinical manifestations. Hypertrophic pyloric stenosis is a common congenital anomaly that typically presents in the 4th-5th week of life. Manifestations include projectile, non-bilious vomiting due to obstruction of the pyloric sphincter. Gastroschisis and omphalocele involve herniation of abdominal organs, the former without a peritoneal covering and the latter with a peritoneal covering. Omphalocele is associated with trisomies and other congenital defects, and is a true umbilical hernia. Congenital diaphragmatic hernia (CDH) occurs when abdominal organs to herniate into the thorax, leading to pulmonary hypoplasia and hypertension.
Tracheoesophageal fistulas (TEF) occur due to failure of septation of the tracheoesophageal tube. Type-C TEF is the most common malformation, where the distal esophagus is connected to the trachea, resulting in non-bilious emesis. TEFs can also occur due to esophageal atresia and a rare anomaly where the trachea and esophagus are connected by a bridge, known as pure TEF.
Duodenal atresia results from the failure of the second portion of the duodenum to recanalize, and manifests as bilious emesis and a ‘double-bubble’ sign on X-ray. Distal intestinal atresia in the jejunum or ileum is often caused by vascular accidents in-utero, presenting similarly to duodenal atresia but also with abdominal distension.
Hirschsprung’s disease stems from the failure of neural crest cell migration, leading to absent innervation and perpetual contraction of the rectal muscles. This results in proximal dilation, or ’megacolon.’.
A meckel diverticulum is a remnant formed when the vitelline duct fails to obliterate, and can be remembered with the ‘rule of 2’s’ (2% of the population, 2 ft proximal to the ileocecal valve, 2 in long, 2 yrs old, 2:1 male:female) Meckel diverticula often presents as painless melena, and can contain various ectopic tissue, most commonly manifesting as gastric tissue. This ectopic gastric tissue can uptake technetium-99m in a technetium-99m pertechnetate scan, an important diagnostic tool.
Intestinal malrotation occurs when the intestines fail to rotate 270 degrees counterclockwise during development, resulting in a cecum located in the RUQ. This can result in fibrous bands that obstruct the duodenum, causing abdominal distension. Twisting around these “Ladd’s bands” can cause midgut volvulus, a surgical emergency.
Acquired conditions include necrotizing enterocolitis (NEC), which occurs when bacteria from feeding overwhelms the immature GI immune system in premature infants. NEC often manifests as abdominal distension and bloody stools, as well as pneumatosis intestinalis on X-ray.
Lesson Outline
Don't stop here!
Get access to 155 more Pathophysiology lessons & 13 more medical school learning courses with one subscription!
FAQs
Pyloric stenosis is a congenital condition characterized by hypertrophy of the pyloric sphincter, which usually develops around the 4th to 5th week of life. It is more common in males, particularly first-borns. The condition often presents with "projectile," non-bilious emesis, as the obstruction occurs before the bile ducts in the duodenum. Additionally, a palpable "olive-shaped" mass at the pylorus may be detected.
Gastroschisis and omphalocele are both congenital conditions involving herniation of abdominal organs. In gastroschisis, the herniated organs protrude through a defect in the ventral abdominal wall near the umbilicus and are not covered by peritoneum. In contrast, omphalocele is a true umbilical hernia where the herniated organs are covered by peritoneum. Omphaloceles are often associated with other congenital anomalies such as trisomies, cardiac abnormalities, and neural tube defects.
Congenital diaphragmatic hernia (CDH) occurs when abdominal organs herniate through a defect in the left hemidiaphragm into the thoracic cavity. This can lead to pulmonary hypoplasia and pulmonary hypertension due to compression of the lungs. Diagnosis is typically made through a chest X-ray, which will show bowel gas and abdominal organs located above the diaphragm.
Type-C tracheoesophageal fistula is a congenital anomaly where the proximal esophagus ends in a blind pouch and the distal esophagus is connected to the trachea. This leads to non-bilious emesis, as food cannot reach the intestines, as well as abdominal distention due to air flow from the trachea into the stomach. It can also cause recurrent pneumonitis and aspiration pneumonia due to reflux of stomach contents into the lungs. In utero, it can lead to polyhydramnios, as the fetus is unable to swallow amniotic fluid.
Hirschsprung's disease arises from failed neural crest cell migration, resulting in a lack of innervation in the distal colon, always involving the rectum. This absence of innervation causes the rectal muscles to remain contracted, inhibiting the passage of stool. As a result, the colon proximal to the constricted area, often the sigmoid colon, becomes filled with stool and dilates, forming a ‘megacolon.' Clinically, it presents with a failure to pass meconium within the first 48 hours after birth.
MCAT® is a registered trademark of the Association of American Medical Colleges. The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). NAPLEX® is a registered trademark of the National Association of Boards of Pharmacy. PANCE© is a registered trademark of the National Commission on Certification of Physician Assistants. NCLEX® is a registered trademark and service mark of the National Council of State Boards of Nursing, Inc. None of the trademark holders are endorsed by nor affiliated with Sketchy or this website.
