Preventing an Unfortunate Polypectomy Attempt in a Large Broad-Based, Smooth, and Soft Polypoid Elevation of the Colonic Wall

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• Answer to the Clinical Challenges and Images in GI Question: Image 2: Giant Inverted Colonic Diverticulum
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Question: A 65-year-old black man with a medical history significant for hypertension and hemorrhoids was referred by his primary care doctor for colorectal cancer screening. The patient denies constipation and notes a small amount of blood on the toilet paper. Also the patient denies any abdominal pain or weight loss. The patient has no family history of colon cancer. Medication list significant for lisinopril 40 mg once a day and ibuprofen 800 mg tablet as needed. Physical examination and laboratory data are unremarkable. Colonoscopy revealed a large polypoid mass with short, thick stalk in the proximal transverse colon, approximately 70–75 cm from anal verge (Figure A). The polypoid mass appeared smooth, with a shiny pink mucosa; the mucosa overlying the mass lesion and stalk was similar to that surrounding normal colonic mucosa. On gentle insufflation, the lesion does not recede into the wall of the colon. The polypoid structure was palpated with forceps (Figure B); it was soft and easily compressible to palpation, which also resulted in a small indentation (Figure C). No diverticulum was seen during our evaluation. The rest of the examination was normal except for internal hemorrhoids.

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The patient was scheduled for a double-contrast barium enema; however, he refused it. Instead abdominal computed tomography (CT) was ordered, which reported a 3.5 × 1.9 × 2.4-cm, dumbbell-shaped, and fat density, is seen within the lumen of the proximal transverse colon on (Figure D). There is no adjacent bowel wall thickening, fat stranding, or lymphadenopathy. The bowel is otherwise unremarkable in appearance. The appendix is visualized and is normal. What is the most likely diagnosis in this patient?

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Answer to the Clinical Challenges and Images in GI Question: Image 2: Giant Inverted Colonic Diverticulum 

Giant inverted colonic diverticulum (ICD) is an unusual complication of diverticulosis, which may lead to misinterpretation as a polyp or a submucosal lesion; biopsy or endoscopic resection of these lesions may lead to severe complications. ICD is a rare colonic finding with a prevalence of 0.7%. ICD may resemble an adenomatous polyp of varying size or submucosal mass, such as lipoma or gastrointestinal stromal tumor and in rare cases as carcinoma arising from the diverticulum. Seventy-five percent have been reported in the sigmoid area.¹, ², ³ The pathophysiology is unknown, but is suspected to be related to segmental variations in mural structure, motility patterns, and intraluminal pressure. The size is also variable from few millimeters to 30 mm. Our patient had a large ICD, measuring 35 mm in diameter. Cases in which the polyp was seen during endoscopy insertion and no longer seen during the withdrawal are assumed to be inverted polyps; the possible explanation probably is that at the time of withdrawal air insufflations may cause the lesion to revert.

The distinction between colonic diverticula and polyps can be made readily on air contrast examination. Where ICD can be seen as a dumbbell-shaped lesion, apparent, except in rare cases; however, this is not the case during endoscopic evaluation, especially when the head of the diverticulum may invaginate into the lumen of the diverticulum and extend into the lumen of the colon as in our patient. Recognition or suspicion of ICD during endoscopic evaluation of the colon may prevent inadvertent or unnecessary diverticulectomy.², ³ When necessary a second study (barium enema or as in our case a CT scan) may permit accurate diagnosis and result in appropriate management. The endoscopic appearances of ICD are variable, and there are no specific features that readily distinguishes them from polyps. Hence in the setting of colonic polyps with and without diverticulosis, the possibility of inverted diverticulum always should be considered.

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References 

1. Saenz R, Kinney TP, Santander R, et al. Inverted colonic diverticula: an uncommon endoscopic finding. Gastroenterologia y Hepatologia. 2008;31:285–288
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2. Ladas SD, Prigouris SP, Pantelidaki C, et al. Endoscopic removal of inverted sigmoid diverticulum-is it a dangerous procedure?. Endoscopy. 1989;21:243–244
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3. Siaka I, Yusuf CG. Inverted colonic diverticulum: a rare finding in a common condition. Gastrointestinal Endosc. 2000;52:111–115
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