Manometric Evaluation of the Sphincter Complex in Anterior Anus and Mild Anorectal Malformations-An Important...

Background: Distinguishing between the anatomical variant of an anterior anus and mild forms of imperforate anus with rectoperineal fistula often requires inspection, calibration, and, in uncertain cases, electrical stimulation (ES) under general anesthesia. Anorectal manometry (AM), despite its ability to assess sphincter configuration and function, is rarely reported as a diagnostic tool. This study evaluated the utility of AM in such cases. Methods: A retrospective analysis of AM and clinical data from 38 patients (35 female, 3 male) with suspected anterior anus was conducted from October 2009 to September 2021. Water-perfused catheter probes with eight radial channels were used to perform pull-through maneuvers. Sphincter locations were identified through vector reconstruction, and pressure ratios of the anterior part to the circumference were recorded. Results were compared to clinical data, including ES findings. Statistical significance was assessed using Mann-Whitney U and Chi-Square tests. Results: Following AM, ES was unnecessary in 25 patients. Of the remaining patients, 83% showed abnormal sphincter configurations on ES, and seven underwent anoplasty. Patients with abnormal sphincter complexes demonstrated significantly lower mean anterior pressures (61.2 mmHg vs. 136.4 mmHg, U = 336.5, p = 0.001) and a trend toward lower anterior-to-circumferential pressure ratios (mean 0.42 vs. 0.85, U = 613, p = 0.270). Constipation was also more frequent in this group (X²(1,N = 38) = 4.1, p = 0.044). Average anterior pressures < 75 mmHg and ratios < 0.7 indicated an anus outside the sphincter complex (sensitivity 80%, specificity 90%). Conclusions: AM proves valuable for evaluating ambiguous anterior anus cases, potentially reducing reliance on ES under general anesthesia. 3D high-resolution AM may further increase diagnostic accuracy.