Adult intussusception

Clinical History

45-year-old man presented to the Emergency Department with a 2-day history of crampy intermittent abdominal pain, vomiting and absolute constipation.

Imaging Findings

Plain radiographs demonstrated distended central small bowel loops.
CT with IV contrast was performed, followed by reconstruction in orthogonal planes with post-processing MPR software. A characteristic target-like structure consistent with entero-enteric intussusception was identified in the ileum, measuring approximately 5 cm in length. Small bowel obstructive over-distension was seen proximally, distally the bowel looked collapsed.
The intussusception was identified at the transition point between the collapsed terminal ileum and dilated upstream small bowel. The colon appeared empty and collapsed.
There was no appreciable mural thickening, soft tissue mass or peri-intestinal abnormalities, and therefore idiopathic intussusception was suspected.

Laparoscopic reduction of the involved small bowel was performed. Histopathological samples disclosed no evidence of dysplasia or malignancy. The postoperative period was uneventful and the patient was discharged 7 days after surgery.

Discussion

Intussusception is the invagination of a proximal bowel segment into the distal bowel lumen. Common in children, adult cases are comparatively rare, accounting for only approximately 5% of all intussusception cases and only between 1-5% of intestinal obstruction [1].

Only 15-20% of adult patients present with the classic paediatric symptom/sign triad of crampy abdominal pain, bloody diarrhoea and palpable ‘sausage-shaped’ mass. Pain is reported in 70-90% [2] – its intermittent nature accounts for delays in diagnosis. Other symptoms & signs may include nausea, vomiting, weight loss, diarrhoea and abdominal distension [3]. Pre-operative diagnosis is difficult because symptoms and signs can be non-specific and subacute, while its rarity means it is not commonly considered in differential diagnoses.

Due to the obstructive nature of presenting symptoms, plain abdominal X-rays are usually the first diagnostic tool, demonstrating typical signs of acute intestinal obstruction [4]. They may also demonstrate an elongated soft tissue mass (typically in the right upper quadrant in children) with related proximal bowel obstruction [5].

Ultrasound is the imaging modality of choice in paediatric cases. However, it is disadvantaged in cases of adult intussusception due to large amounts of air in adult bowel and operator dependency [3].

Abdominal CT is largely considered the most sensitive diagnostic modality for adult cases [6], helping elucidate lead points and underlying causes. The appearance of intussusception on CT is characteristic, depending on the imaging plane and where along the bowel images are obtained.

Characteristic CT features include a ‘target-like/sausage-shaped’ soft-tissue mass with evident layering effect [6]. At the proximal end of the intussusception there will be two concentric enhancing / hyperdense rings, formed by the inner bowel and the folded edge of the outer bowel. As one images further along the intussusception the mesentery (fat and vessels) will form a crescent of tissue around the compressed innermost lumen, surrounded by the two layers of the outer enveloping bowel. Even further distally the lead point (if present) will be visualised [7].

CT accuracy has been shown to be commonly confirmed on the operating table [8]. More frequent use of CT, particularly with orthogonal reconstruction in cases of non-specific abdominal pain, can help increase pick-up rates [9].

As approximately 65% of cases carry a significant risk of associated malignancy [10], radiologic decompression is not addressed preoperatively in adults. Therefore most adult intussusception cases require definitive surgical intervention via laparotomy and bowel resection [1] as a lead point is usually present [5].

Differential Diagnosis List

Final Diagnosis

Adult idiopathic ileo-ileal intussusception

URL:	https://www.eurorad.org/case/12279
DOI:	10.1594/EURORAD/CASE.12279
ISSN:	1563-4086