Simple ultrasound evaluation of the anal sphincter in female patients using a transvaginal transducer

Fecal incontinence affects 0.2% of women aged 15-64 years and about 1.3% of women over 64 years. Most cases are related to instrumental deliveries affecting the anal sphincter complex. We propose a simple technique using the generally available transvaginal transducer to evaluate the anal sphincter complex.

Ninety-two patients underwent ultrasound examination. Group I consisted of 53 nulliparous patients. In Group II there were six patients with normal spontaneous vaginal deliveries without episiotomies. In Group III there were 14 patients with vaginal deliveries and one to three episiotomies but no lacerations. In Group IV there were nine postpartum patients with recently repaired (48 h to 3 weeks) third- and fourth-degree lacerations. All women in Groups I-IV were asymptomatic. Group V consisted of 10 patients symptomatic for fecal incontinence. We used a vaginal probe (5-9-MHz) with the footprint placed in the fourchette pointing towards the anus in a transverse and then in a median (sagittal) plane. If seen, the combined internal and external anal sphincter thickness at the 12 o'clock location was measured. We visualized normal star-shaped mucosal folds on the transverse section and described the sonographic anatomy in both planes.

The mean sphincter thickness measured at 12 o'clock in Group I was 2.3 (range, 1.0-4.7) mm, in Group II it was 2.9 (range, 2.4-3.4) mm, and in Group III it was 2.3 (range, 1.0-3.7) mm. The differences between these three groups were not significant. Patients from Group IV showed thinning or discontinuous sphincter anatomy at the 12 o'clock position. All symptomatic patients from Group V showed abnormal sphincter anatomy, and the normal star-like appearance of the anal mucosa on the transverse section was deformed, radiating from the point of the sphincter damage. Four of the 10 patients in this group underwent surgical repair. In these patients the sonographic findings were confirmed.

The images obtained using this imaging modality show the sphincter muscle anatomy as well as the possible pathology. Due to its simplicity the technique can be applied in any place where a vaginal transducer is available.