A 19-month-old boy is brought to the emergency department with severe abdominal pain and vomiting. On initial evaluation, rebound and guarding are present. Laparotomy is performed, and a portion of the intestine is resected; the gross specimen is shown in the image below:
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Which of the following best describes the underlying pathologic process that led to this patient's condition?
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In this surgical specimen, a longitudinally opened portion of the intestine (identified by the luminal transverse folds) has another intestinal segment that is ischemic (ie, dusky appearance) within its lumen. This is diagnostic of intussusception, an invagination of a portion of the intestine into an adjacent segment.
Intussusception classically occurs in children age 6 months to 3 years, often following a viral infection. Viral stimulation of lymphoid follicles within the small intestine (Peyer patches) can lead to hypertrophy of those areas, which can then act as lead points that become trapped by peristalsis and dragged into a distal portion of the intestine. The most common location is at the ileocecal junction, as in this patient, and is likely due to a dense concentration of Peyer patches in the terminal ileum.
Classic presentation is characterized by periods of inconsolability with colicky abdominal pain correlating with waves of peristalsis at the affected site; air enema usually reduces the intussusception. If untreated, impaired venous return of the invaginated segment can lead to ischemia and necrosis of the intestinal wall. Late findings correlating to bowel ischemia include currant jelly stools (ie, containing blood and mucus) and signs of peritonitis (eg, severe pain, rebound tenderness) warranting urgent surgical intervention, as in this patient.
(Choice A) Eosinophilic infiltration of the lamina propria within the mucosal layer of the intestines is characteristic of eosinophilic gastroenteritis. This typically presents with chronic abdominal pain, nausea/vomiting, or diarrhea; peritoneal signs and invaginated intestinal segments would not be seen.
(Choice C) Intraluminal bacterial overgrowth occurs when the small intestine is colonized by excessive microbes normally found in the colon. However, most patients are older adults with a history of motility disorders or pancreatitis, and symptoms include bloating and diarrhea.
(Choice D) Clostridioides difficile infection causes neutrophilic infiltration of the colonic wall and may be complicated by peritonitis due to toxic megacolon. Invagination of the intestine would not occur.
(Choice E) Pyloric stenosis is caused by smooth muscle hypertrophy at the gastric outlet and presents with vomiting in infants age 3-6 weeks. This patient's age and intestinal findings are inconsistent with this diagnosis.
Educational objective:
Intussusception, which presents with colicky abdominal pain, is characterized by telescoping of one intestinal segment into an adjacent one, most commonly at the ileocecal junction. Pathophysiology usually involves hypertrophy of intestinal lymphoid follicles (Peyer patches), which can act as lead points of the invaginated bowel.