Pedunculated polyp of the ileum protruding from a large diverticulum

A 52-year-old woman presented with iron deficiency anaemia and postprandial right lower quadrant pain. Abdominal examination was unremarkable and laboratory results showed mild anaemia (haemoglobin 11.3 g/dL). Upper and lower endoscopies did not reveal any source of bleeding. Video capsule endoscopy was performed which showed a large polypoid lesion in the mid-ileum (figure 1). Abdominal contrast enhanced CT demonstrated a heterogeneously enhancing pedunculated polyp measuring approximately 6 cm (figure 2). Retrograde double-balloon enteroscopy was performed which revealed a large pedunculated polyp with hyperplastic-like mucosa protruding from a large diverticulum located approximately 70 cm proximal to the ileocaecal valve (figure 3A). The stalk appeared to arise from the base of the diverticulum (figure 3B). A technetium-99m pertechnetate scintigraphy revealed no ectopic gastric mucosa.Figure 1Video capsule endoscopy shows a large polypoid lesion.Figure 2CT shows a heterogeneously enhancing pedunculated polyp (arrow).Figure 3Retrograde double-balloon enteroscopy images. (A) Large pedunculated polyp protruding from a large diverticulum. (B) The stalk appears to arise from the base of the diverticulum.

What is the diagnosis?