The most common cause of incontinence in spayed female dogs is Urinary Sphincter Mechanism Incontinence (USMI). Male dogs rarely get urinary incontinence, but it is possible and diagnostic tests are needed to investigate the cause. USMI is a very common condition in spayed females, it is diagnosed by a simple urine test known as an urinalysis.
If the dog’s urinalysis suggests everything is normal, and she is showing the typical signs of passive urine leaking, then most vets will assume a diagnosis of USMI and treat accordingly. It is important to rule out an underlying infection as a cause of inappropriate urination before treating USMI; your vet may recommend a urine culture in addition to the urinalysis for this reason.
There are many other possible causes of urinary incontinence, including: arthritis in the hind end causing difficulty to posture to urinate, neurological trauma or cancer, or a non-incontinence issue. Other causes include:
Submission incontinence occurs when a dog (often young) is very submissive in personality and urinates when excited. This is a behavioral issue rather than a medical one. Reducing excitement & stimulation and working on behaviour modification techniques to reduce triggers will help with this issue. Screening for infection or another cause might be recommended to make sure there isn’t a medical issue first.
Urinary Tract Infection (UTI)
Just like with humans, UTIs are seen more often in female dogs as they are more prone to bacteria ascending their shorter urethra compared to males. Typically it presents as frequent urination, including accidents in the house. Other signs include straining to pee (posturing to urinate but only a drop or two comes out), or blood can be seen in the urine.
Some dogs are more prone to recurrent UTIs because of anatomical abnormalities like a recessed vulva or urine pooling, or a polyp or defect in the bladder that compromises urine flow. Urinary incontinence is much more rare in male dogs; often diagnostic tests will be conducted to figure out the underlying cause. Prostate disease, cancer, and neurological disease are all possible causes in these cases.
Kidney disease is more commonly seen in older dogs, usually together with weight loss and a fussy appetite. Increased thirst and urine volume are also usually present, as well as accidents in the house. The urine will also seem more watery than normal.
Bladder stones are more commonly seen in certain breeds such as Shih Tzus, Miniature Schnauzers, Bichon Frises, Lhasa Apsos and Yorkshire Terriers, but can develop in any dog. Along with accidents in the house, dogs will also urinate more frequently than normal, strain to pee, or there is blood in the urine.
A urinalysis will look for crystals in your dog’s urine and microscopic amounts of blood. If these are present, ultrasounds or x-rays will likely be recommended to look for stones. While some stones can be dissolved with diet change, others will require surgery to be removed.
A dog can develop bad habits and regress to urinating in the house from a breakdown in training. All the other medical causes should be looked into first and if no abnormalities are detected in their urine, then a behavior cause might be assumed.
There’s usually some kind of change that triggers this, for example, a dog that has a bout of diarrhea and has accidents in the house because of that, may continue to urinate in the house afterwards as a consequence of that behavior.
Sterile cystitis refers to an inflammation of the bladder not related to infection. It is more common in cats, but can occur in dogs as well. The underlying cause is not fully understood but stress may play a role.
Diabetes is a disease that causes high blood sugar in dogs. It will often be noticed by dog owners as inappropriate urination (in the house). The dog is usually drinking more water than normal and eating a lot, but losing weight. They may have other symptoms as well such as new cataracts in their eyes or skin issues.
A tumor in the bladder can partially block the urethra and cause incontinence. The pressure created can sometimes force the urine to leak uncontrollably around the blockage. Worryingly, this overflow does not usually allow for much urine to be excreted and the bladder can quickly enlarge and fill with urine that is trapped. Total blockage of the urine flow is a medical emergency and should be seen by a vet immediately.
Anatomic Abnormalities or Disorders
Injuries or physical trauma, birth defects or surgery can sometimes alter normal bladder function. The most common birth defect that causes incontinence in young dogs is ectopic ureter(s), ureters that are not in the correct anatomical location. Some neurological conditions or injuries can also cause urinary incontinence, including spinal cord and nerve injuries, brain diseases or lesions.