Sacral anomaly and pelvic floor muscle in imperforate anus: a clinical and experimental study.

Influences of sacral anomalies on the postoperative continence of imperforate anus were evaluated clinically and experimentally. Postoperative continence was clinically assessed by the quantitative scoring system for 77 patients (44 of high-type anomalies and 33 of low-type anomalies). Incidence of combined sacral anomalies was 28.6% (38.6% in high type anomalies and 15.2% in low type anomalies). Combined sacral anomalies had harmful effects on the postoperative defecational function, especially on the parameters of rectal sensation and soiling. Patients with more than four segments of sacral vertebrae had relatively satisfying results on the postoperative assessment. For a teratological study to obtain a model of sacral anomalies, Donryu rats were used. Trypan blue was injected as the teratogen intraperitoneally on the nineth day of gestation. Of the 198 live fetuses, 5 rats had tail defect and sacral anomalies. Two of the 5 anomalous rats also had imperforate anus. Four of 5 rats had vertebrae intact above the first sacral segment. In these 4 rats the pelvic floor muscles had developed to some degree. All the vertebrae were agenetic below the thoracic segments in the other rat fetus. This rat had no pelvic floor muscles. These studies showed that the severity of sacral anomalies had a relationship to postoperative continence. Intact sacral vertebrae above the 4th in humans and the 1st in rats correlated with fair development of pelvic floor muscles and satisfying postoperative continence.