Incomplete caudal duplication in a puppy: gross and radiological observations.

Caudal duplication is a rare type of conjoined twinning. The aim of this case report is to describe a case of caudal duplication in a male crossbreed puppy. The puppy was macroscopically and radiographically examined after death. External features included a supernumerary limb projecting from the perineum, complete lack of tail, anal atresia, double penis and absence of scrotal sacs. Internal examination showed anomalies involving the intestine and the urinary system. At x-ray examination, the supernumerary limb showed features similar to that of the normal right hindlimb but showed absence of fibula and tibia and presence of three metatarsi and phalanges. The authors discuss the pathogenic mechanisms of this condition, infrequently reported in veterinary practice, pointing out the importance of embryonic duplications commonly associated with dystocia.