Adult Intussusception
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Direct answer
Adult intussusception is rare — under 5% of all intussusceptions and roughly 1% of adult bowel obstructions — and differs from the childhood disease in one decisive way: a pathological lead point exists in about 90% of cases, and that lead point is malignant in up to a third of small bowel and a majority of colonic cases. Intermittent colicky pain, vomiting and a palpable mass make the classic triad. CT is the diagnostic test of choice, showing the target and pseudokidney signs, and treatment is surgical — en bloc resection without reduction for colonic disease, since reducing a malignant lead point risks tumour dissemination. The childhood reflex of non-operative pneumatic or hydrostatic reduction is actively wrong here.
What you must remember
- Epidemiology: under 5% of intussusceptions, about 1-3% of mechanical bowel obstruction in adults; enteric, colonic and ileocolic patterns, with colonic lesions carrying the highest malignant yield.
- Lead point spectrum: colonic — adenocarcinoma and lymphoma dominate; small bowel — benign lesions (lipoma, the commonest, Peutz-Jeghers hamartomas, leiomyoma), Meckel diverticulum, metastases and melanoma; postoperative and tube-related intussusception occur in unusual settings.
- Clinical pattern: intermittent, self-reducing episodes mean chronicity — pain with vomiting and a mass, easing spontaneously, recurring over weeks; complete obstruction or ischaemia ends the remitting course.
- Imaging: CT defines site, lead point, vascularity and complications (target sign in cross-section, pseudokidney in longitudinal section, mesenteric fat and vessels dragged within the intussusceptum); ultrasound is operator-dependent; barium studies add nothing surgical and waste time.
- Why reduction is forbidden in the colon: the lead point is usually cancer; manipulation risks tumour embolisation into veins and lumen, and the intussuscepted bowel wall is oedematous and friable — hence en bloc resection with oncological clearance for colonic cases.
- Small bowel judgement: if the lead point is clearly benign and the bowel viable (Peutz-Jeghers polyp, lipoma), careful reduction with limited resection or endoscopic removal may preserve bowel; suspicion of malignancy mandates resection without reduction.
- Exam anchors: adults get surgery, children get non-operative reduction; lipoma is the classic benign small bowel lead point; melanoma metastasis is the memorable cause of multiple small bowel intussusceptions.
Reading the scan before the theatre list
A 47-year-old reports three episodes over two months of cramping central pain with vomiting, each settling within hours, and now a firm, mildly tender mass in the right iliac fossa. CT shows ileocolic intussusception — ileum telescoped through the ileocaecal valve into the ascending colon — with an irregular 4 cm mass as the lead point and preserved wall enhancement. The temptation to attempt hydrostatic reduction belongs to paediatrics; here the mass, the age and the colonic location close that door. The operation is a right hemicolectomy with the intussusception left unreduced, en bloc, with lymphadenectomy — the standard oncological resection for what is presumed cancer until histology argues otherwise. Contrast a 19-year-old with Peutz-Jeghers syndrome, laparoscopically found to have a viable small bowel intussusception led by a palpable hamartomatous polyp: there, gentle reduction and polypectomy — or even a deliberately planned endoscopic route if it reduces spontaneously — preserves bowel, because the lead point's benignity is known in advance. The lead point's identity, known or presumed, is the whole decision.
How the exam frames it
The comparison question is always adult versus child: idiopathic and lymphoid hyperplasia in children, pathological lead points in adults, and non-operative reduction reserved for the young. Single-best-answer stems test the malignant yield in colonic disease, lipoma as the classic small bowel lead point, and the target and pseudokidney CT signs. Viva examiners push on the reason reduction is prohibited in colonic cases — venous dissemination of tumour cells and friable wall — and on the management of a viable small bowel intussusception with a known benign lead point, where restraint and bowel preservation are the marks. Multiple simultaneous intussusceptions point the stem towards metastatic melanoma, a favourite exotic distractor that occasionally turns out to be the answer.
Frequently asked questions
How common is adult intussusception?
Under 5% of all intussusceptions and about 1-3% of adult mechanical bowel obstruction — rarity itself becomes the exam hook.
What is the usual lead point in adults?
A pathological lesion in around 90% — carcinoma or lymphoma in the colon; lipoma, hamartomas or Meckel diverticulum in the small bowel.
Which imaging modality is preferred?
Contrast CT — it shows the target and pseudokidney signs, identifies the lead point, and assesses bowel viability; it guides rather than delays surgery.
Why is reduction contraindicated in colonic cases?
The lead point is usually malignant — manipulation risks venous and intraluminal tumour dissemination — and the intussuscepted wall is oedematous, so en bloc resection is standard.
Which adult scenario allows reduction?
A viable small bowel intussusception with a known benign lead point, such as a Peutz-Jeghers polyp or lipoma, may be gently reduced with limited resection.