Rectovesical fistula: a possible cause of postnatal lethality in F1 Dh/+ male mice between DDD female and DH (Dh/+) male.

To reveal a major cause of postnatal lethality in F1 Dh/+ male mice from DDD x DH (Dh/+) mating, the current study was performed. Dh/+ males with retarded growth appeared within a few days after birth. The unusual junction between the rectum and the urinary bladder (rectovesical fistula) was found in nine of 22 Dh/+ male mice, and the bladder contained unusual substances derived from the intestines. When the fistula was recognized, the urine was always gelatinous, and the anus was imperforate in eight cases, suggesting that an affected individual would have trouble in urination and evacuation. From these observations we conclude that the rectovesical fistula is a major cause of postnatal death in the F1 Dh/+ male.