Giant duodenal diverticulum mimicking tumor recurrence after nephrectomy

Clinical History

A 64-year-old female attended her first follow up appointment after nephrectomy for renal cell carcinoma performed 12 months ago. Clinical examination revealed no specific findings. The cicatrix on her right flank healed without reddening or widening of the scar. A tapotment on both sides was denied. Laboratory diagnostics were normal.

Imaging Findings

The ultrasound examination demonstrated an apparent, solid mass in the right renal bed (not shown). Due to the presence of multiple overlying gas filled loops of bowel that filled out the former right renal bed a recurrent tumor could not be excluded. The patient was therefore referred for a computer tomography (CT) of the abdomen for further investigation. Following our standard protocol a CT scan (Volume Zoom, Siemens, Erlangen, Germany) of the abdomen with (Fig. 1a) and without (Fig. 1b) oral contrast agent (1500 ml of bariumsulfate) was performed. The following parameters: pitch 1.5; 120 kV; 165 mAs; collimation 4x1 mm; slices reconstructed with 3 and 5 mm were used. The images were then assessed on a dedicated workstation (Vitrea, Vital Images, Plymouth, USA). The non-contrast scan demonstrated a tubular structure containing numerous small air bubbles in the region of the right nephrectomy bed (Fig. 1a). After oral contrast was given, this structure was seen to fill with the x-ray positive contrast-agent (Fig. 1b). By using curved multiplanar reformation (MPR) a direct communication with the duodenum could be delineated (Fig. 1c). The diagnosis of a benign giant duodenal diverticulum was therefore established. The patient required no further therapy and remained asymptomatic. On year the patient was followed-up within the scope of the tumor aftercare with magnetic resonance imaging. The duodenal diverticulum was again demonstrated and remained unchanged in position and size compared to the CT-scan (Fig. 2).

Discussion

Diverticula involving all parts of the duodenum are observed in 3 to 22% of the population and are reported in 1.1 to 14% of all conventional upper gastrointestinal tract examinations [1,2,3]. Besides the colon (which in majority are in fact pseudo-diverticula), the duodenum contains the highest number of intestinal diverticula. Duodenal diverticula are classified as true or pseudo-diverticula. True diverticula are mostly innate sacks of intestinal wall that include all five layers. Pseudo-diverticula are less common and formed from mucous membrane alone which herniates through a muscular gap. These gaps primarily result from local traction from adjacent masses. Occasionally, true diverticula may also develop like this. Other forms of diverticula are intraluminal diverticula, first described by Nelson in 1947 [4]. Initially they were thought to represent duplication cysts or intraluminal extensions of an intramural diverticulum. More recently it was suggested that they result from propulsive forces on incomplete duodenal diaphragms. In 65% duodenal diverticula are located on the inner curvature of the duodenal „C“ most frequently near the Ampulla of Vater. Duodenal diverticuli in other locations are quite uncommon. Solitary and multiple diverticula were described with sizes ranging from millimeters to several centimeters. Symptomatic diverticula (2-5%) are caused by retention of intestinal contents (including oral contrast agent) resulting in inflammation, mechanical occlusions, bleeding and perforation. Large, juxtapapillary placed diverticula lead to compression of bile and pancreatic ducts. Hence, they are associated with intermittent cholestasis, cholangitis, choledocho- and cholecysto-lithiasis, pancreatico-biliary reflux and widening of the choledochus duct [5]. A few cases described duodenal diverticulitis afflicting the pancreas [6], perforating into the retroperitoneum [7] or the aorta [8]. First x-ray based diagnosis of a duodenal diverticulum was described in 1916 [9]. Most non-symptomatic diverticula are diagnosed by chance on upper GI examinations or during endoscopy procedures. Due to increasing number of endoscopies and decreasing upper gastrointestinal contrast examinations it is essential that radiologists recognize duodenal diverticula on cross sectional imaging [10]. This is especially important when existing diverticula become symptomatic. Air-fluid-levels or completely air-filled diverticula and the extent in transversal scans lead to diagnosis [10,11]. To show small air-fluid-levels coronal or curved MPR are helpful (Fig.1c). T2-weighted coronal MR-images and magnetic resonance cholangio-pancreaticography (MRCP) can demonstrate the shift or obstruction of the pancreatic or hepato-choledochal duct. If diverticula are completely filled with fluid they can be misdiagnosed as pancreatic cysts, focal pancreatitis or cystic neoplasia of the pancreas [11,12,13]. Likewise pseudo-diverticula of the pancreas should be excluded by follow-up exam or surgery. Pancreas pseudo-diverticula are paraduodenal necrotic tumor excavations which can spread to the duodenal wall and can be mistaken for pancraetic or duodenal cysts. Intraluminal duodenal diverticula originate from the papilla or surrounding duodenal wall and are unfavorable for surgery. They often become symptomatic when the duodenal lumen is narrowed and are easily detected by CT [7,14]. We described CT and MRI findings of a giant asymptomatic duodenal diverticulum extending into the nephrectomy bed that initially mimicked tumor recurrence on ultrasound but it’s origin and benign nature could readily be delineated on cross sectional imaging.

Differential Diagnosis List

Final Diagnosis

Giant duodenal diverticulum in the renal bed

URL:	https://www.eurorad.org/case/5231
DOI:	10.1594/EURORAD/CASE.5231
ISSN:	1563-4086