If your dog strains to pee with little or no urine production, it can indicate a significant urinary issue. This article discusses reflex dyssynergia, a condition where the bladder and urethra fail to coordinate properly during urination. Although urethral dyssynergia is uncommon in dogs and cats, it is still an important topic, especially if you have noticed urinary issues in your male dog.
What is reflex dyssynergia in dogs?
Reflex dyssynergia is a functional disorder of the lower urinary tract. These disorders of micturition are complex. Micturition, or urination, involves a coordinated process controlled by nerves from the sacral spinal cord. Normally, when a dog urinates, the detrusor muscle of the bladder contracts to push urine out, while the urethral sphincter simultaneously relaxes to allow urine flow. This coordinated contraction and urethral relaxation is key.
In dogs with dyssynergia in dogs, this synchronized action fails. The bladder contracts, but the urethral sphincter, particularly the internal urethral sphincter and sometimes the external urethral sphincter, does not relax adequately. This creates a functional urethral obstruction, preventing the complete ability to void the bladder.
This condition is often idiopathic, meaning the exact cause is unknown, and it primarily affects middle-aged to older male dogs. It is rarely seen in female dogs. One study from a college of veterinary medicine revealed an average age of 5 years and a weight of ~36kg.
What are the potential complications of reflex dyssynergia in dogs?
This incomplete emptying of the urinary bladder and urine retention can lead to further complications. When urine stays in the bladder for too long, it creates a perfect environment for bacteria to grow, leading to a secondary urinary tract infection.
Additionally, suppose the bladder is constantly overstretched from being full. In that case, its main muscle can become weak and lose its ability to contract properly (a condition known as detrusor atony or bladder atony). Over time, this chronic stretching can even cause the bladder wall to become thickened and scarred (fibrosis), making it harder for the bladder to function correctly.
What are the symptoms of reflex dyssynergia in dogs?
The most common sign of this micturition disorder is difficulty urinating (dysuria). These signs can appear suddenly or develop over a period ranging from two weeks to a year.
A key characteristic of this condition is the pattern of the urine stream. An affected dog may initially start with a normal, strong urine stream, but the stream quickly becomes thin, weak, and may stop and start intermittently. The dog will often posture and strain repeatedly, trying to finish urinating, but is unable to completely empty their bladder.
How is this condition diagnosed?
To diagnose this micturition disorder, it's a process of elimination to rule out other causes of urinary difficulty, like a physical urinary obstruction.
I'll start by discussing the history you've observed at home, focusing on the specific urination problems. During the physical exam, we'll palpate your dog's abdomen. In dogs with this condition, the urinary bladder often feels large, firm, and is difficult for me to empty by gentle squeezing (manual expression).
Sometimes, you might see "overflow urinary incontinence," where urine leaks out because the bladder is so full. This is different from urethral sphincter mechanism incompetence, which is a more common cause of urinary incontinence in spayed female dogs. A key diagnostic step for me is passing a urinary catheter; if it's reflex dyssynergia, the catheter usually passes easily, which helps me rule out a physical blockage like a stone. I'll also perform a basic neurogenic exam, as dogs with this condition typically don't have other neurological problems.
Next, we'll take a urine sample to analyze for signs of inflammation or infection and to check the urine volume. A urine culture helps me identify specific bacteria so I can prescribe the right antibiotic if a secondary urinary tract infection is present.
Additionally, we will likely recommend imaging to get a clear picture of your dog's urinary tract. An ultrasound or special contrast X-rays help me rule out other issues that cause similar symptoms, such as bladder stones or tumors.
What is the treatment for reflex dyssynergia in dogs?
Once we have a diagnosis, our goal is to achieve urethral relaxation so your dog can void normally. Treatment often involves a combination of approaches.
Medical therapy
The primary treatment involves medications called alpha-adrenergic antagonists. These drugs work by relaxing the smooth muscle of the urethral sphincter and decreasing urethral sphincter tone.
I may also prescribe a second medication, like diazepam, which acts as a skeletal muscle relaxant to further promote relaxation. I'll typically recommend giving this medication about 30 minutes before you take your dog for a walk to achieve the best results.
A potential side effect of these medications can be low blood pressure, so we will monitor your dog accordingly.
Supportive therapy
If a urinary tract infection is present, we will treat it with antibiotics based on the culture results. In some cases, your dog may need temporary urinary catheterization to ensure the bladder is fully emptied and to prevent it from becoming overstretched. This catheterization helps manage the residual urine volume.
Once the functional urinary obstruction is relieved, I may consider a medication that helps with bladder contraction to improve bladder contractility and minimize urine retention. In some intact male dogs, neutering has also been reported to be helpful.
Surgical therapy
For dogs that don't respond well to medical management, there are surgical options. This is not a primary treatment of urinary incontinence but rather a way to manage the obstruction. These are more invasive and can include placing a urethral stent to hold the urethra open or creating a permanent opening for urination (perineal urethrostomy).
These surgical options are usually a last resort, reserved for dogs that don't improve with medication.
What is the prognosis?
The good news is that the prognosis for returning to normal voiding behavior with treatment is generally good. However, it's important to know that most dogs require life-long therapy.
If your dog's signs resolve completely, we may be able to slowly decrease the medication doses for long-term maintenance.
It's also important to remember that not all dogs respond to medication, and potential complications like a permanently weakened bladder (detrusor atony) and recurring urinary tract infections can still occur. This atony means the detrusor muscle has poor contraction.
In conclusion, this urine retention disorder is a complex but manageable condition. If you notice your dog straining to urinate, starting and stopping, or being unable to fully empty their bladder, you should make an appointment with your veterinarian. Diagnosis is often achieved after ruling out all other common causes of the symptoms. While treatment often requires lifelong medication to help the bladder and urethral sphincter work together, the prognosis is generally good.