Teaching Case

A 44-year-old man presented to the emergency department with acute abdominal pain, started a few hours earlier and abdominal distension. The medical history was completely negative. Laboratory tests showed an increase in WBC with neutrophil predominance and no other significant anomalies.

Abdominal computed tomography (CT) shows a complete midgut malrotation, with the colon occupying the left side and the small intestine the right abdominal fields, associated with a topographic inversion of the superior mesenteric artery (SMA) and vein (SMV). These findings give evidence to a congenital defect of intestinal rotation. Moreover there is a fluid distension of the ileal loops, but no evidence of volvulus consequent to the congenital malrotation. The ileal loop immediately distal to the tract abnormally distended appears stenotic with thickened and stratified wall. The hyperdensity of the mesenteric fat and endoperitoneal pelvic effusion are demostrated.
The examination identifies an intestinal lesion, 1cm in size, with intense and homogeneous contrast enhancement, located in the stenotic tract.

Midgut malrotation is a condition rarely diagnosed in adulthood because generally it becomes clinically manifest in childhood or young adulthood [1]. During the first quarter of embryonic life there is a progressive elongation and herniation of the midgut in the extraembrionaria cavity with a counterclockwise rotation respect to the axis of superior mesenteric artery. The last stage of embryonic development is the fixation of midgut mesentery with bowel. Any disorders in the midgut development modify the physiological bowel anchoring to its mesentery, predisposing to volvulus formation and so to bowel obstruction [2].
CT findings include: the dislocation of the intestinal loops, the “whirlpool sign”, in case of volvulus, which corresponds to the intestine strangled by its mesentery [3, 4]. The topographical inversion between SMA and SMV caused by the lack of intestinal rotation on the axis of SMA is well visualised.
The patient underwent surgery; a resection of the stenotic loop was performed. The intestinal occlusion with consequent canalisation was solved this way.
Macroscopic histological examination of the surgical specimen reveals 1 cm in size nodule with starry appearance and widespread from the mucosa to the sierosa. Immunohistochemistry demonstrates positivity for chromogranin A and synaptophysin. This reveals a well-differentiated endocrine tumour, G2 (WHO).
Subcentimetric ileal NETs are tumours that, in 15-25% of cases, tend to metastasise at distance, while characteristically they cause an extended local fibrotic reaction that can produce an intestinal obstruction [5]. The CT study plays an important role in the diagnosis of a small stenosing NET and consequently the midgut malrotation appears as an incidental finding.