Preoperative staging of colorectal cancer with a balloon-sheathed miniprobe

Conventional endoscopic ultrasonography (EUS) is a valuable modality for staging the depth of invasion of colorectal cancer. However, there are difficulties with this technique in reaching as far as the cecal area, traversing tight strictures, and obtaining clear images of smaller lesions. Due to these factors, mis-staging often occurs. The literature shows that the miniprobe is superior to EUS, because of its easy manipulation and better diagnostic accuracy. We therefore conducted a prospective study using a balloon-sheathed miniprobe for colorectal cancer staging.

Eighty-six patients underwent preoperative staging using a miniprobe combined with an outer balloon sheath. Six patients were excluded from lymph-node examination due to local tumor resection. Acoustic coupling was achieved with or without water immersion. The results were compared with the histopathological findings in the resected specimens.

The balloon-sheathed miniprobe had an overall accuracy rate of 85 % for T staging, with 100 % in T1; 78 % in T2; 90 % in T3; and 40 % in T4. Lymph-node metastasis was correctly diagnosed in 73 % of cases, with sensitivity and specificity rates of 74 % and 71 %, respectively. It was not possible to obtain clear cross-sectional images using the miniprobe in three patients.

The balloon-sheathed miniprobe is a good alternative for evaluating colorectal tumor lesions, since it can usually obtain cross-sectional images even in markedly stenosed lesions, and the examination can be performed easily with endoscopy, with or without water-infusion techniques. One major limitation with the probe is the difficulty in evaluating deeper structures, such as lymph-node groups and contiguous organ involvement.