Review Question - QID 107538

This child is presenting with acute abdominal distress and currant jelly stools The finding of a "target sign" on ultrasonography is highly sensitive and specific for intussusception, therefore a pneumatic enema is very effective at diagnosing and reducing intussuscepted sections of bowel.

Intussusception occurs when a proximal loop of bowel telescopes and invaginates into a distal segment, which results in compression of the proximal bowel's mesentery and subsequent vascular compromise. Intussusception often occurs when lead points, or segments of bowel which protrude into the lumen of the bowel, advance into adjacent segments. In children, lead points can result from mesenteric adenitis, hypertrophied Peyer's patches, or Meckel's diverticulae. Patients will present with colicky abdominal pain, and investigation with ultrasonography can demonstrate the two segments of bowel invaginated in one another (Illustration A and B)

Beres et al. conducted a systematic review of contrast versus pneumatic enemas for the treatment of intussusception in children. They found that pneumatic enemas were more likely to successfully reduce intussusception in children without evidence of increased morbidity.

Daneman et al. review the literature on diagnostic approaches to intussusception. In general, they comment on the high sensitivity and specificity of the abdominal ultrasound. Moreover, studies have demonstrated negative predictive values as high as 100% when characteristic findings are excluded on via ultrasonography. Comparatively, abdominal radiograph NPV is around 90%.

Figure A shows an ultrasonogram with acoustic attenuations around a mass with tell-tale ring-inside-a-ring appearance known as the "target sign." This finding is highly suggestive of intussusception of one hollow viscus into another. Illustration A shows this same ultrasonogram with an outline of the bowel walls demonstrating the "target sign." Illustration B is a figure of a sagittal section of intussuscepted bowel.

Incorrect Answers
Answer 1: Transanal mucosal biopsy is appropriate in attempting to diagnose Hirschsprung's disease. In such a biopsy a paucity of myenteric plexus neurons will clinch the diagnosis.
Answer 2: This child is unlikely to have toxic megacolon from C. Difficile infecion, therefore antibiotics are not appropriate.
Answer 3: Suspected peritonitis from a hollow viscus rupture is grounds for laparoscopic exploration. This child is hemodynamically stable for his age, and thus can be managed more conservatively with a pneumatic enema.
Answer 5: An upper GI series is unlikely to help resolve this patient's condition, though it may help in diagnosis. However, a pneumatic enema can be both diagnostic and therapeutic.