The study of varicocele through the use of animal models

The pathophysiology of the varicocele has received considerable study, both in humans and in animal models. Mechanistic information is difficult to obtain from human subjects because study designs must not be invasive and the subject population is variable in the status of the varicocele, patient age, fertility or other health-related issues. Because of these limitations, animal models of varicocele have been developed in several species, the most common being the rat. Surgery to establish the varicocele involves partial obstruction of the left renal vein, causing a varicosity of the left spermatic vein, including the pampiniform plexus. Studies using this model have shown that experimental left varicocele induces bilateral increases in testicular blood flow and temperature contemporaneous with decreases in intratesticular testosterone and testicular sperm output. Spermatic vein reflux is not related to the pathophysiological consequences of experimental varicocele. Many questions remain regarding the mechanism by which varicocele induces testicular dysfunction, chief among them being how the unilateral varicocele causes a bilateral testicular response in the first place.