Intraluminal duodenal diverticulum

A 61-year-old woman presented to the gastroenterology clinic with long-lasting intermittent episodes of postprandial epigastric pain and loss of appetite. Blood tests were unremarkable. Gastroscopy revealed duodenal stenosis with suspicion of an extramural lesion distorting the duodenum and a periampullary diverticular opening.

Coronal CT enterography (Movie 1) demonstrates a distended stomach and an elongated, distended first and second part of the duodenum. Within the descending duodenum, a fluid-filled intraluminal outpouching can be seen, which extends into the third part of the duodenum and leads to an obstruction of the true duodenal lumen. Opening of this blind-ending sac-like mass can be recognized on axial CT enterography (Movie 2) and on sagittal reformation (Figure 1, arrow). Volume rendering CT image shows the fluid-filled sac within the duodenum, representing the pathognomonic “windsock sign”, suggestive of an intraluminal duodenal diverticulum (Figure 2). A previous CT examination without oral contrast medium nine years ago with coronal and axial reformations (Figures 3 and 4) demonstrates the non-distended, intraluminal partially fluid, partially gas-filled intraluminal mass (arrows). The diagnosis correlates well with endoscopy (Figure 5) showing the opening of the diverticulum (arrow) and the stenotic true lumen (arrowhead).

Background

Duodenal diverticula are usually incidental findings that do not require intervention [1, 2]. While extraluminal diverticula are caused by prolapse of the mucosa or the entire duodenal wall, intraluminal diverticula are a rare congenital abnormality [1, 3]. They usually occur at the second part of the duodenum near the papilla of Vater due to incomplete recanalization of the duodenum between the fifth and twelfth week of gestation. Consequently, a duodenal web remains in the lumen, which can expand into a diverticulum a few times bigger than its initial size due to chronic anterograde peristalsis [4].

Clinical Perspective

Despite their congenital origin, intraluminal duodenal diverticula take time to develop and therefore, patients are usually not symptomatic until the third decade of life [5]. Complications have been reported in up to 25% of patients [4]. Symptoms are usually nonspecific, and patients present with epigastric pain, abdominal fullness, nausea and vomiting, which is thought to be caused by intermittent obstruction of the duodenal lumen [5, 6]. Other rare symptoms are gastrointestinal bleeding or pancreatitis [5]. Diagnosis via endoscopy can be difficult if the intraluminal diverticulum is collapsed [5].

Imaging Perspective

The pathognomonic imaging finding of an intraluminal duodenal diverticulum is the “windsock sign”, which was initially described in upper gastrointestinal barium studies with a contrast filled diverticulum within the duodenal lumen [7]. Nowadays, diagnosis is usually made by CT and MRI imaging, where the distended intraluminal diverticulum appears very similar to the “windsock sign” [4]. Especially CT enterography can be a valuable method for diagnosis since luminal distension facilitates diagnosis of this rare entity. If the intraluminal diverticulum only has a very small orifice, an endoscopic examination may help make the diagnosis and establish the exact location of the diverticular neck with respect to the ampulla of Vater [4].

Outcome

Symptomatic patients can be treated surgically or endoscopically, with endoscopy being the preferred approach since it is less invasive. Endoscopic treatment consists of either diverticulotomy with needle-knife incision or diverticulectomy via snare resection [8].

Take Home Message / Teaching Points

1. Intraluminal duodenal diverticulum should be considered as a differential diagnosis of duodeno-duodenal intussusception.
2. In cases of transient symptoms and visible intraluminal duodenal tumor, CT enterography with distension of the lumen may help find the correct diagnosis.
3. The “windsock sign”, although described for upper GI series, can be depicted on CT imaging and is a characteristic imaging finding for an intraluminal duodenal diverticulum.