This is a condition in which the opening of the prepuce (the skin that covers the penis) is too small. Although it is usually a defect the animal is born with, it can also be the result of injury. Typically, this is only a problem during mating. When the male gets an erection, the penis cannot pass through the preputial opening to be exposed for breeding. In severe cases, it can cause problems with urination, as urine will build up within the sheath and then slowly drip out.
What are the symptoms?
During breeding, the male may make repeated and unsuccessful attempts to mate. The penis trapped in the sheath causes a large bulge under the skin. These animals frequently traumatize themselves during mating attempts, which results in blood dripping from the preputial opening. Animals that have difficulty with urination chronically leak urine on their skin.
What are the risks?
Dogs attempting to mate, in addition to not being able to mate, can damage the penis. Those with urine leakage will suffer from urine scalding. This is an irritation from chronic exposure or contact with urine. Evidence of it will be found on the skin surrounding the preputial opening and on the structures within the sheath.
What is the management?
Phimosis is easily corrected with surgery. Males that are not intended to be part of a breeding program and have no problem with urination should be neutered. In breeding males or those with difficulty voiding urine, the preputial opening can be enlarged. There is some question if dogs born with this condition should be allowed to breed.