Managing urinary obstruction in cats

A comprehensive exam of the abdominal area with an ultrasound and monitor is a fast way to help determine if a cat has a urinary obstruction

A comprehensive exam of the abdominal area with an ultrasound and monitor is a fast way to help determine if a cat has a urinary obstruction. Obtaining a complete history of the patient is crucial in diagnosing this common ailment.

Urinary obstruction in male feline patients is quite common in general and emergency practices. This condition is life threatening and should be treated with urgency. Veterinarians and veterinary technicians must be comfortable managing and treating these critical patients when they walk into the clinic.

Urinary obstruction occurs when there is a partial or total blockage of the urethra to the bladder. This can cause urine to fill the urinary bladder and up to the kidneys. This can cause multiple electrolyte imbalances, which, if severe enough, can cause death. Causes of urethral obstruction can vary from urinary calculi, mucous plugs, strictures, neoplasia, or can even be idiopathic. 

Gathering data

The history of these patients is very crucial in the diagnosis. Usually they are “in and out of the litterbox,” vocalizing during urination, straining to urinate in or out of the litterbox, hematuria, or not producing any urine at all. Some owners can mistake a urinary obstruction with constipation, so it is important to make sure a thorough history is taken.

Some owners with multiple cats in the household may not even realize their cat has even had a problem until it is suddenly not eating, or not coming out from under the bed. These patients can even present as being lethargic or vomiting.

The physical exam usually can point us in the right direction of diagnosing a patient with a urinary obstruction. Their bladder is, usually, abnormally large, and turgid upon palpation and cannot be expressed. If the blockage is recent, sometimes the bladder can be small, but feel very turgid.

The penis may be inflamed or an abnormal color due to self-trauma, but this may not always be the case. If the blockage has been there for a significant period, the patient will present very lethargic or laterally recumbent. Depending on the severity of the blockage, the patient may present bradycardic (<140 bpm) and hypothermic (<99 F). Hypotension may also be observed.

Stabilization of these patients is crucial. Bloodwork must be taken immediately to assess electrolytes. An intravenous catheter should be placed. Blood can be taken from that catheter to minimize trauma to the patient. (Do not flush your catheter if you decide to do this). Once the blood is taken, a PCV/TP, glucose, and “stat” bloodwork should be done. It is crucial to remember to perform bloodwork with pH and electrolytes included. An electrocardiogram should be performed.

So, what’s the big deal about electrolytes? Potassium plays an important role in how the heart functions. Remember the sodium-potassium pump? This is the mechanism that helps with ion transport in the heart. If you have too much potassium, the heart will not beat appropriately, or at all.

On the patient’s ECG, there may be “high-tented” T-waves, absent “P-waves”, prolonged P-R interval, and bradycardia. These abnormalities usually do not show up in a patient until their potassium levels are greater than 6 mmol/L, but can occur with even lower potassium levels. Acidosis and azotemia can also be found on the initial bloodwork. These should be noted, but the hyperkalemia should be treated and corrected first. 

Treating and healing

A comprehensive exam of the abdominal area with an ultrasound and monitor is a fast way to help determine if a cat has a urinary obstruction. Obtaining a complete history of the patient is crucial in diagnosing this common ailment.

Treating the hyperkalemia should be instituted first before the patient is to undergo anesthesia for a unblocking and a urinary catheter. There are multiple ways to treat hyperkalemia. One is to correct with intravenous crystalloid fluids.

There are people who will debate if 0.9 percent NaCl or other electrolyte balanced isotonic fluid, such as Plasma-Lyte, is better for a urinary obstructed patient. Either way, isotonic fluids will help with vascular volume as well as dilute the serum potassium and support heart function.

It is important to remember to assess the patient for a heart murmur before and during administrating fluids. A patient can easily be fluid overloaded if a heart condition is undetected.

The most common way to treat hyperkalemia is with regular insulin and dextrose. Regular insulin can be given intravenously at a dose of 0.5units/kg. Insulin can shift potassium into the cells, thereby decreasing serum potassium. A dextrose solution should be given intravenously after the insulin at a 0.5-1ml/kg dose diluted as a one-to-one ratio with 0.9 percent NaCl. After this is given, a 1.25 percent – 2.5 percent dextrose CRI for four to six hours, should be considered.

Other ways to treat hyperkalemia are with calcium gluconate and sodium bicarbonate. Calcium gluconate can be administered at 10 to 20 mg/kg IV slowly over 15 to 20 minutes. Bradycardia and arrhythmia can result if calcium gluconate is given too quickly. Calcium gluconate can protect the heart by increasing the threshold for the cell’s membrane potential, which results in a normal difference between the resting membrane potential and the action potential.

This does not have any effect on potassium levels, but usually after un-obstruction, potassium levels tend to decrease. Sodium bicarbonate is usually the last resort to treat hyperkalemia. It can drive potassium into the cells, but it can also cause hypocalcemia, hypernatremia, alkalosis, and seizures. Sodium bicarbonate should only be given to those patients who are also acidemic and hyperkalemic.

Cystocentesis is a controversial topic when it comes to blocked cats. There is one study claiming there are some benefits to do multiple cystocentesis when combined with pain medication, acepromazine, a low stress environment. This protocol was used when owners had financial concerns. In this study, 11 out of 15 cats were discharged. The risk of a cystocentesis would be bladder rupture, but this is uncommon (Cooper, 2010).

Placing a catheter

Urethral catheterization is the next step after stabilizing the patient. Anesthesia in these patients can be tricky. Clinicians all have their own drug protocols. It is crucial you familiarize yourself with the drug combinations they use and, educate yourself on the side effects and modes of action.

Some clinicians are now using nerve blocks/epidurals as a safer, quicker way to unblock these felines. Again, familiarize yourself with the protocols used by the clinician.

There are also multiple ways clinicians unblock cats. Some like the patient on their side, some like them on their back, etc. Familiarize yourself with how each clinician likes to unblock cats. Once the cat is anesthetized, clip and sterilely prep around the penis. The technician should have gotten out urinary catheters, syringes of saline, a urinary collection bag, tape, and suture.

There are multiple catheters that can be used to unblock these patients. Open ended tomcat catheters can be used first to aid in relieving the obstruction. These should not be used long term in patients because it is rigid and can cause inflammation.

A red rubber catheter can then be used once the obstruction is relieved as a long-term catheter. There are multiple other catheters on the market to relieve obstructions in cats.

Once the catheter is placed in the urethra, tape is placed around the catheter and sutured into the prepuce to prevent the catheter from coming out, and the urinary collection bag is connected to the catheter. A radiograph is then taken to confirm placement in the bladder as well as to check for any bladder stones. The catheter should be placed in the bladder, not in the urethra distal to the bladder.

Once the catheter is placed, a urine sample should be tested for a urinary tract infection, stones, or other abnormalities. Medications should be started based on the result. Antibiotics are not recommended unless a urinary tract infection is detected.

Catheters should be kept in placed for 36 to 48 hours or until the urine has improved color and the patient has normal bloodwork. Once the catheter is removed, the patient should be kept on fluids and urine should be seen in the litterbox.

During discharge, the technician should advise the owners to keep stress levels down, add more litterboxes, add more water into the patient’s diet (canned food can be an option), and certain pheromone sprays/plug-ins can be used. Re-obstruction can occur quickly after discharge from the hospital. The patient should have a urinalysis rechecked seven to 10 days post-obstruction.

Prognosis for these patients when treated quickly is quite good, but once a feline has an obstruction, they are at risk of having another obstruction in the future. If a patient has multiple obstructions, they may require a perineal urethrostomy (PU). PU surgery widens and shortens the urethra
to help prevent obstructions at the tip of the penis. However, they do not prevent stones from obstructing the urethra.

Urinary obstructions in cats are quite common in every practice. It is important to know the physiology behind treating these patients. There are multiple ways of un-obstructing these cats. It can mean life or death if veterinary professionals do not know how to care for these patients.

Tami Lind, BS, RVT, VTS (ECC), is the current ICU and ER supervisor at Purdue University Veterinary Teaching Hospital. Lind has been at the university for 10 years. She went to veterinary technology school at Purdue and graduated in 2010 with her bachelor’s degree in veterinary technology and has never left. She started as a veterinary technician in the ICU and has been the supervisor at Purdue since 2012.


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Cooper, Edward S. Controversies in the management of feline urethral obstruction. J of Vet Emergency and Critical Care. 2015; 25(1): 130-137

Cooper, Edward S. Owens TJ, Chew D, Bluffington C.A.T. A protocol for managing urethral obstruction in male cats without urethral catheterization. J of Vet Med Assoc. 2010; 237(11): 1261-1266

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