Pediatric GI Pathology

Small bowel obstruction (SBO) is an interruption of the flow of the intraluminal contents through the small intestine, and is classified as mechanical (due to physical blockage) or functional (due to disruption of normal motility). The most common cause of SBO in the Western countries is post-surgical adhesions. Small bowel obstruction typically presents with nausea, vomiting, abdominal pain, distention, constipation, and/or obstipation. The diagnosis is established via imaging. Up to 80% of all cases will resolve with supportive management (bowel rest, intravenous (IV) hydration, and nasogastric decompression). However, surgery is required for persistent or complicated cases.

Diarrhea is described as passage of large amounts stools that are often loose, liquid, or watery, resulting in excess loss of fluids and electrolytes. Diarrhea is one of the most common illnesses in children, representing the largest percentages of morbidity and mortality worldwide in the pediatric age group. The majority of cases are infectious, caused by rotavirus, while the rest are caused by bacteria (Escherichia coli, Salmonella) and parasites (Entamoeba histolytica). Management is largely based on rehydration; antibiotic therapy is used only when indicated. Prognosis is excellent if diarrhea promptly treated.

Hirschsprung disease (HD), also known as congenital aganglionosis or congenital megacolon, is a congenital anomaly of the colon caused by the failure of neural crest-derived ganglion cells to migrate into the distal colon. The lack of innervation always involves the rectum and extends proximally and contiguously over variable distances. Most cases are diagnosed in the neonatal period, with a classic triad of symptoms including delayed passage of meconium, abdominal distension, and bilious vomiting. Individuals having less severe degrees of functional obstruction may not be diagnosed until later in infancy or childhood when they present with symptoms of chronic refractory constipation, abdominal distension, and failure to thrive. The diagnosis of HD is confirmed by the absence of ganglion cells on rectal biopsy after noninvasive testing such as anorectal manometry and the use of contrast enema. Surgical resection of the aganglionic segment is the standard treatment.

Vomiting, or emesis, is the forceful oral expulsion of gastric contents. Vomiting is a common presenting symptom in pediatrics. The frequency and characteristics of vomiting may point toward a specific pathology, just as its presence can be another symptom of a greater clinical situation. The majority of vomiting symptoms are benign and self-limited. A good history and physical examination can bring into focus the underlying cause and workup. Management is with antiemetics and treating the underlying cause, if needed. The most common complications are dehydration and malnutrition.

Acute abdomen, which is in many cases a surgical emergency, is the sudden onset of abdominal pain that may be caused by inflammation, infection, perforation, ischemia, or obstruction. The location of the pain, its characteristics, and associated symptoms (e.g., jaundice) are important tools that help narrow the differential diagnosis. Patients will typically have severe tenderness with associated rigidity and rebound tenderness. Laboratory evaluation will demonstrate leukocytosis, acidosis, and in some cases, abnormal hepatic function tests. Imaging helps narrow the differential diagnosis; first-line imaging is always an upright chest X-ray to evaluate for pneumoperitoneum. The treatment and prognosis of acute abdomen strongly depend on the underlying cause, but the vast majority of these cases constitute a surgical emergency with associated morbidity and mortality.

Intussusception occurs when a part of the intestine (intussusceptum) telescopes into another part (intussuscipiens) of the intestine. The condition can cause obstruction and, if untreated, progress to bowel ischemia. Intussusception is most common in the pediatric population, but is occasionally encountered in adults. The pediatric patient typically presents with acute cyclical abdominal pain and vomiting, while adults present with symptoms of bowel obstruction. The diagnosis in children is frequently clinical but may be supported by an abdominal ultrasound showing a classic target sign. Management options in children include contrast or pneumatic enema, with surgical options reserved for failure of the non-operative measures, complications such as gangrene or perforation, and treatment of underlying pathology. In adult patients, surgery is usually required.

Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. The diagnosis can frequently be established clinically, but imaging is used in uncertain cases. Computed tomography (CT) scan provides the highest diagnostic accuracy. Perforation occurs in 13%–20% of cases and can present as localized (abscess/phlegmon) or free perforation with generalized peritonitis. The standard treatment is appendectomy, but localized perforations are frequently managed non-operatively with antibiotics.

Constipation is a common complaint in children that is relatively defined for individual age groups based on the frequency and difficulty of defecation and stool consistency. The majority of constipation cases are functional or non-organic. Clinical presentation may vary, from insufficient evacuation noted by the parents, to complaints of abdominal pain, to secondary incontinence. Often, a combination of non-pharmacologic and pharmacologic management is needed for evacuating bowel content, eliminating pain upon defecation, and improving bowel habits.

Congenital duodenal obstructions are a group of inborn conditions that cause obstruction of the lumen of the duodenal segment of the small intestine, impeding the passage of food and gastric juices. The condition may have intrinsic etiologies, such as duodenal atresia (most common) and/or extrinsic etiologies, such as an annular pancreas. The hallmark of duodenal obstruction is bilious vomiting. The condition can be diagnosed through prenatal or postnatal ultrasound. Associated anomalies, including congenital heart disease, are common. Treatment includes fluid resuscitation and surgical duodenoduodenostomy.

Hypertrophic pyloric stenosis is hypertrophy and hyperplasia of the pyloric sphincter muscle. The condition is the most common cause of gastrointestinal obstruction in infants. Affected newborns typically present after the third to fifth week of life with progressive non-bilious vomiting and a firm, olive-like mass in the epigastrium. Ultrasound confirms the diagnosis based on the thickness and length of the pyloric muscle and channel diameter. Initial treatment consists of fluid resuscitation with correction of electrolyte imbalances, followed by either open or laparoscopic pyloromyotomy.