Background: Perineal body thickness (PBT) is measured by endoanal ultrasonography. The literature has shown that women with obstetric trauma to the anal sphincter have decreased PBT, and a measurement of 10 mm or less has been proposed as abnormal. Therefore, this study aimed to compare the proposed definitions of normal to pathologic findings in patients with fecal incontinence (FI) and to correlate PBT with anorectal physiologic findings.
Methods: All female patients who had endoanal ultrasonography and PBT measurement for evaluation of FI were assessed and divided into three groups on the basis of PBT: 10 mm or less, 10 to 12 mm, more than 12 mm. The degree of FI (0 = complete continence; 20 = complete incontinence) was correlated with PBT.
Results: For this study, 83 female patients with a mean age of 59.7 years (range, 30-88 years) had endoanal ultrasonography and PBT measurement. Sphincter defects were suggested by endoanal ultrasonography in 77% of the patients in the three groups as follows: 57 (97%) of 59 patients, 4 (36%) of 11 patients, and 3 (23%) of 13 patients. The mean external sphincter defect angle was 110 degrees (range, 45-170 degrees ), and the mean FI score was 13.8. For 89% of the patients there was a history of vaginal delivery. As reported, 35% had undergone one or more prior perineal surgeries, 27% had both, and 4% denied having had either. A significant correlation between sphincter defect and PBT (p < 0.001) was noted. External sphincter defect angles were negatively correlated with PBT (p = 0.001).
Conclusion: A PBT of 10 mm or less is considered abnormal, whereas a PBT of 10 mm to 12 mm is associated with sphincter defect in one-third of patients with FI. Those with a PBT of 12 mm or more are unlikely to harbor a defect unless they previously have undergone reconstructive perineal surgery.