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Abdomen » Gastrointestinal
Carcinoma of the sigmoid colon
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Author(s) :
Ravi Kadasne, MD
Presentation A 37 year old woman presents with pain in the lower abdomen and constipation for 3 months. She has been intermittantly febrile and reports no history of weight loss.
Caption: Transverse transabdominal pelvic scan
Description: There is significant circumferential bowel wall thickening noted in this image.
Caption: Sagittal transabdominal scan
Description: The sagittal scan also shows the thickening of the sigmoid colon. With transducer pressure, the patient had severe tenderness at the site of the thickened bowel wall.
Caption: Single contrast barium enema study
Description: The barium study shows a narrowed segment of the sigmoid colon with shouldering [apple-core appearance]. This is a reliable sign for malignancy.
Caption: Double contrast barium enema image
Description: This double contrast image shows the mucosal irregularity in the narrowed segment of the sigmoid colon. This is also highly suggestive of a malignant lesion.
Caption: Double contrast barium enema image
Description: The narrowed segment of the sigmoid colon and the mucosal irregularity is noted again, marked between arrows.
Differential Diagnosis Inflammatory versus neoplastic bowel wall thickening
Final Diagnosis Neoplastic involvement of sigmoid colon - adenocarcinoma
Discussion Colorectal carcinomas are the most common malignant tumors of the gastrointestinal tract. Although ultrasound is not the diagnostic modality of choice for reaching this diagnosis, colorectal tumors are now increasingly detected by ultrasound. This is because many patients with these malignancies present with non-specific abdominal pain and often ultrasound is the initial diagnostic modality that is offered.

Ultrasound appearance:
Of the bowel mass:
1. The bowel mass per se may appear as an exophytic hypoechoic mass arising from the bowel wall, or
2. There might be concentric diffuse or irregular bowel wall thickening. Wall thickness of > 3mm with the lumen distended and > 5mm with a collapsed lumen is highly suspicious of bowel pathology.
3. The normal layered appearance of the bowel wall may be lost.
4. In advanced cases, the mass may contiguously infiltrate the urinary bladder or the other pelvic organs.

Of complications:
1. Enlarged, hypoechoic mesenteric and para-aortic lymphadenopathy may be present.
2. If the patient presents with intestinal obstruction, dilated aperistaltic bowel loops may be seen leading to the mass.
3.  If the patient presents with intussusception, the classical target appearance with multiple layers of alternate hyper and hypoechoic rings are noted. The intusscepient may show a bowel mass at its leading edge.
4. The primary role of ultrasound in colonic malignancy is to detect hepatic metastases, which can be reliably detected. These are most often hyperechoic.  However they may be hypoechoic or have a target appearance.

Barium studies show the diagnostic ‘apple-core’ appearance or shouldering in the region of the mass. Contrast enhanced CT and now newer techniques such as virtual colonoscopy can demonstrate the tumor and help in complete staging.
Case References 1. Hassan I. Colon, adenocarcinoma
2. Wittenberg J, et al. Algorithmic Approach to CT Diagnosis of the Abnormal Bowel Wall. Radiographics. 2002;22:1093-1107.
Follow Up This patient had a biopsy proven adenocarcinoma of the colon
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