Ahmed-Emad Mahfouz MD, Presenter: Nothing to Disclose

Hanan Sherif MD, Abstract Co-Author: Nothing to Disclose

Ahmed El Sayed Sayedin MBBCh, Abstract Co-Author: Nothing to Disclose

Moamena Ahmed El-Matbouly MBBCh, Abstract Co-Author: Nothing to Disclose

Rashad Alfkey MD, Abstract Co-Author: Nothing to Disclose

Diagnosis of rectosigmoid carcinoma on contrast-enhanced CT relies on demonstration of thickening and enhancement of the rectosigmoid wall and enlarged lymph nodes. Rectal wall thickening may be the only sign seen in early carcinoma and may be mimicked by spasm or adherent fecal matter. Angiogenesis and arteriovenous shunting within the carcinoma may result in earlier venous return in the draining inferior mesenteric vein (IMV) compared to the superior mesenteric vein (SMV). The purpose of this study is to evaluate fast venous return of intravenous contrast agent in IMV compared to SMV (the IMV sign) as a diagnostic sign for rectosigmoid carcinoma.

Contrast-enhanced CT of the abdomen and pelvis of 35 patients with rectosigmoid carcinoma and 50 patients free of colorectal disease as a control group have been randomized and reviewed in consensus by two experienced radiologists, blinded to the diagnosis. In the first session transverse CT sections of the pelvis were reviewed for rectosigmoid wall thickening and lymph nodes. In the second session, only 3-D reconstructions of the arterial and venous-phase CT were reviewed to note whether contrast agent appeared earlier in IMV compared to SMV (positive IMV sign). The diameter of IMV and the IMV/SMV enhancement ratio have been measured and compared in the two groups by the Student’s T-test.

Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of IMV sign for diagnosis of carcinoma have been 83, 100, 100, 89, and 93% as compared to 100, 84, 81, 100, and 91% for wall thickening and 40, 98, 93, 70, and 74 % for nodal enlargement respectively. IMV/SMV enhancement ratio on arterial phase has been significantly higher in the carcinoma group (1.38±0.42) compared to control group (0.68±0.25) (p<0.05), denoting faster venous return in IMV, while the difference was not statistically significant in the venous phase. There has been no statistically significant difference of IMV diameter between the carcinoma (5.8±1.1 mm) and the control group (4.3±1.2 mm).

The IMV sign is a useful sign for the diagnosis of rectosigmoid carcinoma on contrast-enhanced CT

IMV sign is specific for rectosigmoid carcinoma. Rectosigmoid wall thickening should not be interpreted as a spasm if associated with the positive IMV sign.

Mahfouz, A, Sherif, H, El Sayed Sayedin, A, El-Matbouly, M, Alfkey, R, The Inferior Mesenteric Vein Sign: A New Sign for Diagnosis of Rectosigmoid Carcinoma on Contrast-enhanced CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005773.html