Measurement of the anal cushions by transvaginal ultrasonography.

Abstract

The anal cushions are believed to contribute to the anal continence mechanism. Transvaginal ultrasound previously has been used to visualize the anal sphincters. Using this method, visualization of the anal cushions has been described but no quantitation of the cushions has been undertaken. Because impairment of the anal cushion function may lead to anal incontinence, this study was designed to evaluate the use of transvaginal ultrasound to measure the anal cushions. Patients attending a gynecologic ultrasound list were recruited into the study. By measuring cross-sectional areas, a cushion:canal ratio was calculated. Fifty females were studied. Results showed that the area enclosed within the internal anal sphincter had a median of 2.37 cm(2) (interquartile range, 1.76-2.61). The cushion:canal ratio was 0.66 (interquartile range, 0.57-0.7). Interobserver error was 0.98 and intraobserver error 0.99. In this pilot study, we conclude that transvaginal ultrasonography is a reliable method of measuring the anal cushions in healthy control subjects. A narrow normal range can be established. This may be compared later with anal cushion size in patients who have symptoms of incontinence and may be used to assess changes in the size of the cushions in response to recently described anal cushion bulking agents.