Blocked bladder in cats

Content by Dr Nicole Olewinski – BVSc MRCVS

A blocked bladder happens when something prevents urine from leaving the bladder through the urethra. As the kidneys continue to produce urine, it builds up inside the bladder with nowhere to go. It’s a life-threatening emergency.

An average 4kg cat produces about 40-80 ml of urine a day, but the bladder normally only holds around 50ml. This means it can take less than a day for dangerously high pressure to build up inside the bladder, causing intense pain and potentially damaging the kidneys.

• A life-threatening emergency
• A few drips of urine may still come out even when blocked
• Very painful
• Can rapidly damage the kidneys
• Toxins build up in the blood and can affect the heart

While trauma from accidents, cancer or inguinal hernias can block the bladder, by far the most common causes are those to do with feline cystitis. Small stones that slip from the bladder into the urethra, plugs made of protein and sediment, muscle spasms, inflammation and blood clots can all block the urethra and stop your cat from being able to urinate.

You can read more about cystitis in our guide to feline idiopathic cystitis.

Any breed can be affected, but males are much more likely to suffer from a blocked bladder because their urethra is narrower, longer and more winding than a female cat’s. Overweight and indoor cats also appear to be at higher risk.   

The signs of cystitis almost always start before the bladder actually blocks. Going to the vet as soon as you notice symptoms can sometimes prevent the bladder from blocking at all.

Look for:

• Straining to urinate with little or no urine coming out
• Repeatedly going in and out of the litter tray
• Weeing in strange places
• Dripping urine
• Vomiting
• Overgrooming the back end
• Loss of appetite or drinking less

At later stages, pain and toxin build-up may make cats lethargic, pant like a dog, or lash out when touched.

Diagnosis

A blocked bladder is often easy for a vet to feel during an examination, so it doesn’t take long to pick up on the problem. The next step is emergency treatment, but your vet will want to perform tests to diagnose what caused the blockage and check for toxin build-up in the blood.

You can expect:

• Multiple blood samples to check kidney health and potassium levels before and after unblocking
• Urine tests to look for crystals and culture for bacteria
• X-rays and ultrasound to look for urinary stones

Unblocking a cat’s bladder usually starts with sedation, pain relief and medication to counteract inflammation and muscle spasms. Next, a urinary catheter will be passed slowly into the urethra, using sterile saline to gently break down or flush any blockages back into the bladder.

This is a delicate procedure. An inflamed urethra can tear and, in severe cases, the bladder may rupture. The urinary catheter is usually sewn in place for a few days while medication to treat the underlying cause of the blockage takes effect.

Fluid therapy via an intravenous catheter helps flush toxins from the body and the urine produced then helps dilute and flush out inflammatory debris from the bladder. For cats whose potassium is extremely high, additional medication is needed to protect the heart.

Medications targeted at inflammation and muscle spasms are often given for several weeks, while urinary diets and anti-stress medication are likely to be recommended for the rest of your cat’s life. Weight loss is also advised.

For male cats who have blocked more than once or are at high risk of blocking again, surgery can be done to create a new, wider opening for the urethra (perineal urethrostomy). This isn’t a perfect solution though, and can have complications.  

Prognosis

Short-term and long-term prognosis are two different things. Recovery from a blocked bladder depends on the degree of damage done to the kidneys. With rapid veterinary attention, many cats quickly get back to normal. However, unlucky cats will be left with kidney damage and need ongoing management for chronic renal failure.

When the urinary catheter is removed, there is also a risk period when reblocking can happen quickly.

Long-term, without treatment for the underlying cause of the blockage, recurrence is common. Sadly, a cat that was lucky to avoid kidney damage once may not be so lucky a second time – around 30% of urinary obstructions result in death or euthanasia.

“I’ve found that when it comes to cystitis, there’s a tragic mismatch between human medicine and veterinary medicine. Many people have first-hand experience of human cystitis as a run-of-the-mill medical condition. However, the anatomy of a male cat means cystitis in cats can be the polar opposite, and the first time a cat blocks can tragically be the last.

“For the lucky cats that make it to the clinic in time, the transformation can be remarkable. A lethargic, painful and sometimes aggressive blocked cat can become relaxed, comfortable and cuddly in just a few short days.

“Relief is understandable. But months or years later, owners can develop a false sense of security. Perhaps you’re wondering if your cat is bored of the same urinary diet, or whether those stress-reduction supplements are really necessary. If your cat is doing well, please don’t risk it! I don’t want to scare people, but more than that, I don’t want to see your cat on my clinic table with a bladder the size of an orange.”

Dr Nicole Olewinski – BVSc MRCVS

If you’re thinking about buying a Petgevity Lifetime Plus policy, we’ll consider all pre-existing conditions when offering cover for your cat*. 

When you apply for cat insurance, you need to let us know: 

• Which medical conditions they’ve had in the last two years 

• Their health status now

Find out more about Petgevity’s cat insurance for pre-existing conditions.