Benign Disease

Because endoscopic ultrasonography relies on alterations of the 5-layer architecture to diagnose abnormalities, it can precisely localize lesions such as adenomas, ulcers, submucosal tumors, and anal sphincter defects and determine whether any layers are destroyed [22,73-75]. However, EUS cannot reliably distinguish between a benign adenoma on the surface of the mucosa and a localized carcinoma that has not disrupted deeper layers. Once the integrity of deeper layers becomes disrupted, EUS becomes quite accurate in staging a lesion However, inflammatory changes due to benign ulcerations can mimic disruption of integrity of deeper layers and may result in an incorrect diagnosis or stage. Biopsy confirmation of the histological nature of the lesion is there fore essential to accurately assess colon wall abnormalities

Thickening of all layers of the colorectal wall or absence of superficial layers can be seen in ulcerative colitis [74]. Benign pericolic lymph nodes can also be detected by EUS. Therefore, it is unlikely that EUS will have a role in finding areas suspicious for malignancy in patient with ulcerative colitis.

EUS has made an impact in the management of patients with Crohn's disease by improving detection and mapping of abscesses and fistulas [22,74,75]. These lesions can be found even in patients without symptoms suggestive of anal-rectal disease. For detection of pararectal abscesses, sensitivity of transrectal ultrasound appears to be more than 90%, compared with less than 60% for CT. EUS has also been reported to differentiate transmural inflammation from mucosal inflammation; however, the utility of this information has yet to be determined.

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