Transient, idiopathic adult entero-enteric intussusception

Clinical History

A 55-year-old male patient with clinical and radiographic diagnosis of acute mechanical bowel obstruction and unremarkable past medical history was transferred to our hospital for further investigation and treatment. He denied any previous abdomino-pelvic surgical procedure.
All laboratory tests were within normal limits.

Imaging Findings

Urgent multidetector CT confirmed mechanical obstruction, by showing markedly dilated stomach and entire small bowel with abundant endoluminal fluid and several air-fluid levels.
A characteristic target-like structure consistent with entero-enteric intussusception was identified in the jejunum, measuring approximately 5 cm in length. Small bowel obstructive overdistension was seen both proximally and distally to the abnormality. The transition point between collapsed terminal ileum and dilated upstream small bowel was identified as an abrupt kinking without appreciable mural thickening, soft tissue mass or perivisceral abnormalities. The entire colon appeared empty.
Urgent laparotomic surgery was performed. Kinking and stenosis of the distal ileal loop causing obstruction was identified and treated by ileocecal resection. Meticulous exploration of the upstream small bowel excluded signs of intussusception or other palpable abnormalities.
Surgical pathology specimen, including appendix and perivisceral lymphnodes, excluded inflammatory and neoplastic changes. One month after discharge, repeat CT showed normal postoperative findings, and disappearance of the jejunal intussusception.

Discussion

Intussusception consists of invagination of a gastrointestinal segment (the intussusceptum) with its mesenteric fold, into an adjacent tract (the intussuscipiens). Unlike in children, in adults intestinal intussusception is uncommon (less than 5% of all obstruction conditions), and has an underlying cause in the vast majority of occurrences. Approximately half of cases are small bowel intussusceptions (SBI), which are most usually caused by benign abnormalities (such as Meckel’s diverticulum, infectious ulcers, Crohn’s disease, sprue, inflammatory or adenomatous polyps, or lipomas) rather than by malignant tumours [1-3].
Clinical and radiographic manifestations of SBI reflect the degree of upstream bowel obstruction. Adult intestinal obstructions are currently investigated with multidetector CT with multiplanar image review. Early-stage SBI is confidently diagnosed when the characteristic “target-like” CT appearance is identified in planes perpendicular to the longitudinal axis of the process, including an intraluminal soft tissue (the intussusceptum) surrounded by mesenterial fat, entering the upstream (intussuscipiens) segment. Over time, progressive bowel wall thickening with oedema and vascular compromise lead to a sausage-shaped appearance with alternating attenuation seen in planes parallel to the abnormality, or a bilobed reniform mass with peripheral high attenuation [2, 3].
Very recently, self-limiting SBIs without identifiable lead point and underlying cause have been increasingly detected on CT studies. Secondary to dysrhythmic contraction, transient SBIs outnumber adult surgical intussusceptions, and most usually involve the proximal small bowel. Therefore, an early, uncomplicated jejunal SBI without obvious lead point should lead to question its clinical importance. Furthermore, as this case exemplifies, imaging detection of such an abnormality should prompt careful search for an alternative cause of obstruction. Although SBIs shorter than 3.5 cm are almost invariably benign and most likely spontaneously reducing, this cut-off length is unreliable as a predictive factor because many clinically insignificant lesions are longer. Conversely, a sausage-shaped or reniform CT appearance suggesting bowel ischaemia should dictate immediate surgical treatment [2-4].
Currently, adult SBI cases are treated surgically. Considering the possibility of intermittent SBI without underlying pathology, conservative treatment or laparoscopic reduction may obviate the need for intestinal resection [5-7].

Differential Diagnosis List

Final Diagnosis

Small bowel obstruction from distal ileal kinking. Transient jejunal intussusception.

URL:	https://eurorad.org/case/10279
DOI:	10.1594/EURORAD/CASE.10279
ISSN:	1563-4086