Several weeks ago I saw a friendly older small terrier mix whose owner brought him in because he seemed uncomfortable and was straining to urinate. He also had been having accidents (urine only) in the house for about a day. As you may know, I work at an emergency clinic. I only treat emergencies.

Does urinary discomfort qualify as a true emergency?

It absolutely does. First, urinary discomfort is a form of pain. No dog should be left in pain overnight or during a weekend while waiting for his regular vet’s office to open. Also, urinary discomfort can sometimes be caused by stones that have moved from the bladder into the urethra. Such stones are capable blocking the flow of urine out of the bladder. That condition, called urinary obstruction, is incredibly serious and can cause a horrible, painful death within a day. The owner of the dog in question did exactly the right thing by heading to the emergency clinic when she did.

I evaluated my patient. He was bright, alert, and friendly. He was also quite a muscular fellow. He did not seem dramatically distressed. His prepuce (foreskin) and penis appeared normal. Crucially, his bladder was small and soft — such a finding is not compatible with a life-threatening urinary obstruction.

I asked the owner a few questions about the symptoms. She stated that the dog had always seemed to urinate more frequently than other dogs, and she assumed that he enjoyed marking his territory. However, his urinary frequency had gone up dramatically that day, and he was sometimes only squeezing out a few drops. His appetite, thirst, and activity were not affected.

There are several things that can cause such symptoms in dogs. Urinary tract infections, also known as UTIs or colloquially as bladder infections, are the most common cause. Bladder stones, non-infectious inflammation of the bladder, anatomical anomalies, urinary tract tumors, and foreign bodies such as foxtails in the urinary tract round out the list. Or rather, almost round it out. There is one other thing that can cause such symptoms only in male dogs who’ve not been neutered: prostatitis. This dog was neutered.

But I had to wonder: Was he definitely neutered? Muscular dogs who like to mark territory often have a lot of testosterone in their systems, and testosterone is made by testicles. Neutering a dog involves removing the testicles.

I begged the dog’s pardon, and then broke etiquette (in general it is best to buy dinner for an individual before doing what I did next) by doing a reach-around. There were no testicles palpable in his scrotum. For good measure, I also palpated his inguina (his groin, which is a common place to find non-descended testicles). There were none there, either.

I felt compelled to ask: Was the dog definitely neutered? Yes. When? At about six months of age. By whom? A family veterinarian in another state. Did he have two testicles before he was neutered?

That last question resulted in an awkward moment. The owner looked at me like I was crazy. After a pause she replied that she hadn’t paid much attention to that area before he was neutered. Fair enough, I thought — only someone in the know would be likely to devote much thought to such a subject.

I have to admit that the question does sound odd. But there was a reason why I asked it. Virtually all male dogs, it turns out, have two testicles. But sometimes the testicles do not descend into the scrotum. Dogs with non-descended testicles are called cryptorchids. They often seem to have only one testicle, but there almost always is another one lurking within the abdomen or under the skin of the groin.

Back in the olden days, I imagine some time after bloodletting lost favor but before the recognition that animals feel pain, it was common practice for vets to remove only the testicle(s) in the scrotum during neuter surgeries. If a dog, like most dogs, had both his testicles in his scrotum, then they’d both be removed. If there was only one, then only it would be removed. And if neither testicle had descended into the scrotum, then nobody saw any need to neuter the dog at all. The reason for this was simple: It’s harder to find and remove a testicle if it’s not in the scrotum.

But it turns out that leaving an undescended testicle in a dog is an extremely bad idea. The testicle will produce testosterone, which might lead to behavioral issues. But more important, undescended testicles develop cancer at astronomically high rates. In the modern day, leaving an undescended testicle in place in a dog is considered the height of malpractice. Pretending that an undescended testicle does not exist can be a death sentence for the dog later in life.

The dog in question had been neutered in the 2000s. Surely, I thought, no vet in that era would commit the error of leaving an undescended testicle in place. The dog probably had a bladder infection.

We collected a urine sample for analysis and culture. To be safe, we also took X-rays to check for bladder stones. No stones were seen, but the prostate was visible on the radiographic image. A visible prostate is a normal finding in an un-neutered dog. A dog neutered as a juvenile should not have a visible prostate.

I begged the dog’s pardon again and gently performed a rectal exam. The prostate was palpable and enlarged. It was also sensitive. The dog appeared to have prostatitis — a condition that occurs almost exclusively in un-neutered males.

The owner was surprised when I told her about the dangers of cryptorchidism and my strong suspicion that her dog still had at least one testicle, most likely located within his abdomen. I recommended that she follow up with her family vet for an ultrasound and testosterone assays as soon as possible due to the risk of testicular cancer. She seemed a bit skeptical. Antibiotics and pain killers were meanwhile prescribed.

Later that evening, the urinalysis was performed. There were loads of bacteria and white blood cells in the urine, which is characteristic of an infection of the urinary tract or the prostate. But there were also, rarely, sperm in the urine. I looked in the microscope myself to verify the finding. The sperm were grizzled and irregular. There was no way on earth that those sperm could ever get anyone pregnant.

However, there is also only one thing on earth that can possibly produce a sperm, grizzled or not: a testicle. The dog in question most definitely had a retained testicle — and that testicle was ripe to develop cancer.

I called the owner and advised her that her dog needed to undergo further tests and treatments to locate and remove the testicle as soon as possible. She seemed convinced by the end of the conversation.

I realize that a dog owner may reasonably be averse to paying too much attention to his or her pet’s scrotum. However, owners of male dogs need to be aware of whether both testicles are descended. If one is not, the matter needs to be addressed. This is true even for dogs owned by people who do not desire neutering — in such cases it is best to remove the cryptorchid testicle and leave in place the one in the scrotum.

Learn more about dogs with Dogster:

• 6 Ways to Thwart an Off-Leash Dog Rushing You and Your Dog
• On Dogs and Body Language: How I Learned to “Speak” Dog
• Aspirin and Ibuprofen: Are Human Pain Meds Safe for Dogs?

Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)