Endorectal ultrasound detection of focal carcinoma within rectal adenomas

The misdiagnosis of a rectal adenoma by biopsy and subsequent finding of invasive cancer after transanal excision is associated with a number of pitfalls. Problems include suboptimal therapy for a potentially curable cancerous lesion, potential tumor transgression of the local site with increased chance for local recurrence, and increased potential for more radical surgery or adjuvant chemoradiation. The utility of endorectal ultrasound (ERUS) in guiding treatment decisions of rectal villous adenomas has been reported, but series are small and are from single institutions. To determine the utility of ERUS in the diagnosis of rectal adenomas, we compared diagnosis made by biopsy alone to diagnosis made by a combination of biopsy and ERUS.

A systematic literature review was performed by way of a PubMed search to find articles with the following terms: "biopsy-negative rectal adenomas," "preoperative ERUS diagnosis," and "surgical histopathology." Five studies met the criteria, thus providing data for 258 adenomas. A quantitative meta-analysis was performed on the data.

Among the 258 biopsy-negative rectal adenomas, 24% had focal carcinoma on histopathology. ERUS correctly established a cancer diagnosis in 81% (95% confidence interval 69 to 90) of these misdiagnosed lesions. Thus, ERUS diagnosis of biopsy-negative rectal adenomas could be expected to decrease the need for additional surgery and other associated problems caused by misdiagnosis from 24% to 5%.

ERUS is a useful adjunct to biopsy in the preoperative workup of rectal villous adenomas, and we recommend its routine use. Accurate preoperative assessment allows the surgeon to counsel the patient appropriately regarding the best operation, the perioperative risks, and the chances of local recurrence.