Lateral Branches of the Testicular Artery Affect Testicular Shape in Adult Stallions

• We evaluated arterial patterns of 251 stallion testes.
• Forty-five (18%) testes had one or two lateral branches of the testicular artery.
• Lateral branches of the testicular artery in testes from the adult stallions were associated with distinct lateral bulging.
• Normal stallion testes have either ellipsoid shape or pear-like shape.

The objective of this study was to investigate the arterial patterns of the stallion testis in relation to testicular shape. Two hundred and fifty-one stallion testes were evaluated for the presence of the lateral branches of the testicular artery. Seven specimens had their testicular arteries filled with latex milk, fixed in 70% alcohol, and dissected. Two hundred six specimens (82%) had a single testicular artery and no lateral branches; 39 testes (16%) had one lateral branch of the testicular artery; and six testes (2%) had two lateral branches of the testicular artery each. The lateral branches of the testicular artery obtained from the adult stallions, more than 5 years old, were associated with distinct lateral bulging, giving them a pear-like shape, whereas similar vascular pattern in young colts, less than 1 year old, did not cause similar shape change. Five distinct patterns of the branching of the testicular artery were determined. We concluded that the lateral branches of the testicular artery are present in approximately 20% of stallion testes. This anatomic pattern is associated with a lateral bulge that develops slowly over several years and is associated with a change in testicular shape from an ellipsoid in colts to a pear-like shape in adult stallions.