Anorectal atresia. An experimental model in the rat

Aiming to assess the development of the anorectal sphincteric apparatus and whether it is influenced by the presence of an intestinal conduit through the muscular complex, we seek to develop an experimental model of anorectal atresia in foetuses of female pregnant rats, given orally the herbicide et hylenethiourea (ETU). Six 3-months-old, 300 g female Wistar rats were included in the study group (SG). The foetuses of another unexposed rat formed the control group (CG). In the SG 54, foetuses were alive, all had hypoplasia of the tail and 47 ( 87%) had no visible anal orifice. The 18 foetuses of the CC were normal. Th e histological study was performed at the level of the pubic symphysis. Typ e I anorectal atresia was defined when this section demonstrated an intesti nal conduit and Type II when only a muscular cord was found, without any in testinal tube. This study was completed in 15 (32%) of the SG, 9 (60%) with anorectal atresia Type II and 6 (40%) with atresia Type I, and in 11 anima ls (61%) of the CG. The thickness of the sphincter muscle was larger in the CC; (260.47 +/- 35.32 mu) than in the SG (208.98 +/- 55.01 mu), p < 0.05, but this difference was due to the animals showing atresia Type II. To conclude: ETU had a teratogenic effect. The foetuses with atresia, parti cularly Type II, had a decreased development of the muscular complex. The p resence of an intestinal conduit does not significantly influence the devel opment of the muscular complex.