The pattern of venous drainage of the equine ileocaecal junction.

The veins draining the ileocaecal junctions of horses (n = 19), donkeys (n = 3) and a plains zebra, (Equus burchelli antiquorum) were injected with latex via the ileocolic vein, and dissected. In all specimens the ileocaecal papilla was drained by 2 major papillary veins: one cranial and one caudal to the papilla. A smaller dorsal vein drained either into the cranial or into the caudal vein. The submucosal veins seemed to increase in number in the ileocaeacal junction to form a venous plexus. This plexus, together with veins from the caecum and the distal ileum immediately bordering the ileocaecal junction, drained either into the cranial or the caudal veins of the papilla. In 14 specimens both the cranial and caudal veins drained into a common vein, which opened into the V. caecalis lateralis in 10 specimens or into the R. ilei mesenterialis in 4 specimens. In 3 specimens the 2 veins opened separately into the V. caecalis lateralis. In 2 specimens the cranial vein opened into the V. caecalis lateralis, while the caudal vein drained into the R. ilei mesenterialis.