A 51 -year-old man complains of abdominal pain and blood-stained stools. The barium study of his intestines shows the following finding. What is the most likely diagnosis?

Correct Answer: D. Intussusception

Intussusception in adults is a telescoping of one bowel segment into an adjacent segment, classically presenting with the pathognomonic "target sign" or "doughnut sign" on barium studies and CT imaging. In a 51-year-old with abdominal pain and blood-stained stools, this radiological finding is diagnostic. Unlike paediatric intussusception (idiopathic, ileocolic, age 6–36 months), adult intussusception is almost always secondary to an underlying lesion—commonly a polyp, malignancy, Meckel's diverticulum, or adhesions. The barium study demonstrates the characteristic concentric rings of invaginated bowel wall, with the lead point often visible. The clinical triad of colicky abdominal pain, palpable mass, and blood-stained stools (though the mass is rarely palpable in adults) should trigger immediate imaging. Management in adults requires surgical exploration because of the high likelihood of pathology requiring resection. The target sign (axial imaging showing alternating layers of mesenteric fat and bowel wall) is virtually pathognomonic and distinguishes intussusception from other causes of obstruction in this age group.

Why the other options are wrong

A. Diverticulitis — Diverticulitis presents with left lower quadrant pain and fever, but barium studies show outpouchings (diverticula) arising from the colonic wall, not the concentric telescoping pattern. Barium is contraindicated acutely in diverticulitis due to perforation risk. The blood-stained stools and radiological target sign are not typical of uncomplicated diverticulitis. B. Volvulus — Volvulus (sigmoid or caecal) presents with acute obstruction and shows a bird's beak or coffee bean appearance on barium studies—a twisted, narrowed segment. There is no target sign, and the clinical presentation differs. Volvulus is more common in elderly patients with chronic constipation and does not typically produce blood-stained stools unless ischaemia develops. C. Ulcerative colitis — Ulcerative colitis is a chronic inflammatory bowel disease with continuous mucosal involvement starting at the rectum. Barium studies show loss of haustra, granular mucosa, and lead pipe appearance, not the concentric target sign. UC typically presents with diarrhoea and mucus, not acute obstruction, and is a diagnosis of exclusion in this acute presentation with a pathognomonic radiological finding.

High-Yield Facts

Mnemonics

TARGET sign = Intussusception Telescoping bowel → Axial imaging → Rings of mesentery → Get to surgery → Explore for pathology → Treat the cause. Use when you see concentric rings on CT/barium in an adult with obstruction. Adult Intussusception = Secondary Malignancy, Meckel's, Adhesions, Polyp = MMAP. Always look for an underlying lesion in adults; paediatric is idiopathic. Use to remember why adult cases need surgery.

NBE Trap

NBE may pair blood-stained stools with inflammatory bowel disease (UC) to trap students who overlook the pathognomonic target sign on imaging. The key discriminator is the radiological finding, not the symptom alone.

Clinical Pearl

In Indian practice, adult intussusception is often missed because clinicians anchor on paediatric presentations. Always demand imaging (CT preferred over barium) in any adult with acute obstruction and blood-stained stools; the target sign mandates immediate surgical consultation to identify and resect the underlying pathology (often malignancy in this age group).

_Reference: Robbins Ch. 17 (Gastrointestinal Pathology); Harrison Ch. 287 (Gastrointestinal Bleeding); Bailey & Love Ch. 71 (Small Intestine)_