Ultrasonographic patterns in patients with obstructed defaecation

Anal ultrasound is helpful in assessing organic anorectal lesions, but its role in functional disease is still questionable. The purpose of the present study is to assess anal-vaginal-dynamic perineal ultrasonographic findings in patients with obstructed defecation (OD) and healthy controls.

Ninety-two consecutive patients (77 women; mean age 51 years; range 21-71) with symptoms of OD were retrospectively evaluated. All patients underwent digital exploration, endoanal and endovaginal ultrasound (US) with rotating probe. Forty-one patients underwent dynamic perineal US with linear probe. Anal manometry and defaecography were performed in 73 and 43 patients, respectively. Ultrasonographic findings of 92 patients with symptoms of OD were compared to 22 healthy controls. Anismus was defined on US when the difference in millimetres between the distance of the inner edge of the puborectalis muscle posteriorly and the probe at rest and on straining was less then 5 mm. Sensitivity and specificity were calculated by assuming defaecography as the gold standard for intussusception and rectocele and proctoscopy for rectal internal mucosal prolapse. Since no gold standard for the diagnosis of anismus was available in the literature, the agreement between anal US and all other diagnostic procedures was evaluated.

The incidence of anismus resulted significantly higher (P < 0.05) in OD patients than healthy controls on anal (48 vs 22%), vaginal (44 vs 21%), and dynamic perineal US (53 vs 22%). A significantly higher incidence of rectal internal mucosal prolapse was observed in OD patients when compared to healthy controls on both anal (61.9 vs 13.6%, P < 0.0001) and dynamic perineal US (51.2 vs.9% P = 0.001). For the diagnosis of rectal internal mucosal prolapse, anal US had a 100% sensitivity and specificity. For diagnosis of rectal intussusception, anal US had an 83.3% sensitivity and 100% specificity and perineal US had a 66.6% sensitivity and 100% specificity. In the diagnosis of anismus, anal ultrasonography resulted in agreement with perineal and vaginal US, manometry, defaecography, and digital exam (P < 0.05). Other lesions detected by US in patients with OD include solitary rectal ulcer, rectocele and enterocele. Damage of internal and/or external sphincter was diagnosed at anal US in 19/92 (20%) patients, all continent and with normal manometric values.

Anal, vaginal and dynamic perineal ultrasonography can diagnose or confirm many of the abnormalities seen in patients with OD. The value of the information obtained by this non-invasive test and its role in the diagnostic algorithm of OD is yet to be defined.