Retroperiton

Carcinome colique hypoéchogène. Une Paroi intestinale excentrique épaisse est visible et la lumière intestinale est rétrécie et hyperéchogène. La tumeur se présente comme une masse de la fosse iliaque gauche.
histologie : carcinome lieberkuhnien

Colic carcinoma

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Almost all colon cancers are primary adenocarcinomas. Tumors of the colon arise as intramucosal epithelial lesions, usually in adenomatous polyps or glands. As cancers grow, they invade the muscularis mucosa and lymphatic and vascular structures to involve regional lymph nodes, adjacent structures, and distant sites, especially the liver.
The most common site for a bowel tumor in the adult is around the caecum. It is useful to target this area in patients with altered bowel habit in whom bowel carcinoma is suspected, although detection with ultrasound is usually incidental

Ultrasound :
The normal bowel has a typical appearance on sonography. In general it has a bull's-eye or target-like appearance with a central hyperechoic component and an outer hypoechoic ring. There are three hyperechoic layers and two hypoechoic layers: The inner hyperechoic layer arises from the interface reflection between the lumen and the surface of the mucosa. The second layer is hypoechoic and arises from the-combined deep mucosa and the muscularis mucosa. The third layer is hyperechoic and arises from the submucosa. The fourth layer is hypoechoic and arises from the muscularis propria. The final outer layer is hyperechoic and arises from the interface reflection between muscularis propria and the serosa or adventitia (peri-intestinal fat). These five layers are routinely se on endoscopic ultrasound and are intermittently seen transcutaneous scans.
On US, Colonic neoplasms give rise to hypoechoic or heterogeneous bowel wall thickening, the target or atypical target sign. A colonic tumor appears typically as an echo-poor or mixed mass with a hyperechoic and eccentric gas-filled lumen. This cannot be differentiated, however, from an inflammatory mass on ultrasound. Vigorous Doppler flow can usually be visualized in both inflammatory and malignant masses. Other findings include localized irregular colonic wall thickening, an irregular contour, lack of normal peristalsis, and an absence of the normal layered appearance of the colonic wall.
With high resolution scans disruption of the layered bowel pattern may be seen. Malignant lesions are more common in patients with greater wall thickness, asymmetric involvement, loss of stratification, absence of perigut findings and involvement of short segments.
When a colonic lesion is seen, a search for possible lymph node and live metastases should be made. Bowel obstruction is not an unusual mode of colonic carcinoma presentation. With a fluid-filled proximal bowel the obstructive bowel lesion may be directly visualized. The finding of a colonic mass would normally prompt a barium enema, to delineate the nature, extent and position of the mass, with subsequent staging by CT if malignancy is confirmed. The advantage of ultrasound over barium enema is that of displaying the tumor itself, rather than just the narrowed lumen. The role of ultrasound in patients with known bowel carcinoma is to identify and document the presence of distant metastases, particularly in the liver, as metastases from colorectal carcinoma are particularly amenable to curative resection.
Hepatic metastases from a colonic primary tumor are usually hyperechoic (increased echogenicity in relation to normal liver; but also may be hypoechoic (decreased echogenicity).
Large bowel lymphoma represents 1.5 % of all abdominal tumors. It is usually indistinguishable from a carcinoma causing an atypical or typical target sign. However the bowel thickness tends to be more hypoechoic in lymphoma than bowel carcinoma.

Differential :
*Inflammatory bowel disease.
*Bowel infarction.
*Intramural hematoma.
*Diverticular mass or abscess.
*Metastases.
*Lymphoma.