&NA;Endoanal ultrasonography has become an important tool in the evaluation of patients with anal incontinence. However, the extent of anterior defects is sometimes difficult to quantitate during endoanal ultrasonography.PURPOSE:This study was designed to evaluate perineal body measurement during endoanal ultrasonography in assessing patients with obstetric anal sphincter injuries.METHODS:Forty‐two patients with anal incontinence because of obstetric sphincter injuries and 13 asymptomatic subjects were investigated with endoanal ultrasonography. Sphincter muscle thickness, sphincter defects, and perineal body were measured. Perineal body measurement was performed by inserting a finger, held gently against the posterior vaginal wall, into the vagina and measuring the distance between the inner surface of the internal sphincter and the ultrasonographic reflection of the finger.RESULTS:All patients had anterior sphincter lesions of varying extent. Mean size of internal sphincter lesions was 146°, and mean size of external sphincter lesions was 107° (P<0.001). Perineal body measurement was performed without difficulty in all patients and subjects. Perineal body measurement (mean ± standard deviation) was 6±2 mm in patients and 12±3 mm in asymptomatic subjects (P<0.001). Ninety‐three percent of patients had perineal body measurement <‐10 mm, and 70 percent of asymptomatic subjects had perineal body measurement >10 mm. Digital delineation of the perineal body during endoanal ultrasonography improved the visualization of sphincter lesions in 74 percent of patients.CONCLUSIONS:Digital delineation of the perineal body during endoanal ultrasonography improved the visualization of sphincter lesions in the majority of patients. Perineal body measurement is performed without difficulty and is a good predictor of anterior sphincter lesions. Use of this technique improves visualization of sphincter lesions.