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Management of the blocked cat for veterinary technicians

dvm360dvm360 July 2021
Volume 57

Veterinary technicians play a critical role in identifying and treating blocked cats in the emergency department.

Valerie Potapova / stock.adobe.com

Valerie Potapova / stock.adobe.com

Blocked cats are a common emergency presentation in the veterinary hospital. Veterinary technicians should be able to recognize a blocked cat during triage and alert the veterinarian. Rapid identification of these patients will allow for the lifesaving emergency stabilization and treatment that is required. In a session at the recent Fetch dvm360® virtual conference, David Liss, MS, MBA, RVT, VTS (ECC, SAIM), CVPM, discussed must-know facts and practical management tips for blocked cats that can be used by the entire veterinary team.

Clinical presentation

Patient presentation will vary depending on how long the obstruction has been present. Liss notes that these patients are generally “either alert, bright, and ready to kill you, or on death’s door.”

Often, these cats present with a history of lower urinary tract signs (stranguria, dysuria, hematuria, or pollakiuria), hiding, or vocalizing in the litter box. Liss cautions veterinary team members that owners who are not aware of the signs of a urethral obstruction may call with concerns that their cat is constipated. If the cat is a younger adult male, urethral obstructions are more likely than constipation and these cats should be evaluated on an urgent basis..

Triage and physical examination

For male cats presenting for urinary signs or vague clinical signs, such as lethargy, inappetence, vomiting or hiding (known to many in the profession as“ADR”), veterinary technicians should perform their usual triage, including temperature, pulse, respiration, checking mucous membranes, and assessing mentation. They should add one additional step and palpate the bladder. Liss notes that technicians cannot make the diagnosis of urethral obstruction because this is beyond their scope of practice, but they can alert the veterinarian if they palpate a firm, large bladder as part of their triage assessment.

The large, firm bladder is the hallmark physical examination finding in blocked cats, and most present with abdominal pain. They may be tachycardic or bradycardic depending on the disease progression. Blocked cats presenting with bradycardia, hypothermia, obtunded mental state, or in lateral recumbency are unstable and require immediate stabilization.


The first step in treating a blocked cat is to obtain emergency consent from the owner for treatment. This can be done by a technician while other team members prepare for stabilization, obtain a blood pressure measurement and blood for a minimum database (including acid-base status, electrolytes, and renal values), and connect an ECG for cardiac monitoring.

When it comes to stabilization, the first step is to place an IV catheter and administer a small fluid bolus. Liss states, “There was a time when we worried about giving fluids to blocked cats. We really shouldn’t.” These patients present in shock and fluid therapy will help with the acidemia and hyperkalemia that are present. Buffered crystalloids, such as Normosol-R, are the most efficient in reducing acidemia and do not affect resolution of hyperkalemia.1

Common laboratory abnormalities in blocked cats include azotemia, hyperkalemia, acidemia, hyperlactatemia, and hypocalcemia. An ECG should be assessed at presentation and monitored during treatment. Classic findings in the presence of hyperkalemia include tall, sometimes tented T waves, wide QRS complexes, and absent P waves. Ventricular escape rhythms may be present.

Hyperkalemia is the most immediately life-threatening abnormality. Although hyperkalemia may be reduced somewhat by the initial fluid bolus, severe cases warrant additional treatments. Calcium gluconate is considered cardioprotective because of its effect on the electrical conduction in the heart, but it does not address the hyperkalemia directly. Regular insulin can be administered to move potassium back to the intracellular spaces. Dextrose should be administered as well to prevent hypoglycemia secondary to the insulin. Blood glucose should be monitored in these patients to ensure dextrose supplementation is sufficient.

In some cases, a decompressive cystocentesis can be performed to relieve some pressure from the bladder until the patient is stable enough for anesthesia and deobstruction. Historically, some clinicians have had concerns that performing a cystocentesis in an obstructed cat could result in iatrogenic bladder rupture. However, studies support the safety of decompressive cystocentesis in these patients.2,3 Finally, Liss reminds veterinary teams to institute pain management as soon as the patient is stable enough to tolerate it.


Definitive treatment of the blocked cat requires relieving the obstruction. Although pain medication may provide some sedation, additional anesthetic agents are often required. Some patients will need to be placed under general anesthesia whereas others may be deobstructed under strong sedation with a sacrococcygeal nerve block.

It is important to minimize anesthesia time in these compromised patients. Technicians should ensure that all supplies are prepared before inducing anesthesia. The patient should be preoxygenated, premedicated, and closely monitored. Monitoring should include ECG, oxygenation, blood pressure, and heart rate.

The procedure for deobstruction involves the use of an open-ended tomcat catheter. Saline is pulsed gently through the catheter to break up and retropulse the obstruction. Once the obstruction is relieved and the bladder and urethra have been flushed, an indwelling catheter can be placed to maintain a patent urethra during diuresis. If a red rubber catheter is used, a radiograph should be taken to ensure optimal placement due to the length of this type of catheter.

Following placement of the indwelling catheter, a closed collection system should be connected. Leaving the catheter open creates a high risk of urinary tract infections. Liss notes that resterilized IV sets work well if commercially available setups are not available. He recommends removing all clamps from these IV sets to prevent them from being accidentally closed, impeding urine flow in the line. He also cautions team members to always check the cage door to ensure the urine line is not inadvertently kinked in the door.

Potential complications of blocked cats include bladder rupture, urethral trauma from catheterization, and cardiac arrest. Liss notes these are all rare, but technicians “have to be prepared because [blocked cats]are really variable.”

Nursing considerations

Most blocked cats are hospitalized with a urinary catheter in place. Maintenance of the urinary catheter is an important part of nursing care. The collection system should be kept closed to prevent the introduction of bacteria. Gloves should be worn when handling the urinary catheter and collection set. The perineal area and urinary tubing should be cleaned with diluted chlorhexidine every 4 to 6 hours during the hospital stay.

In addition to standard monitoring, Liss notes the following items that should be considered for blocked cats:

  • Pain scoring, such as the Feline Grimace Scale, should be utilized regularly to ensure that the patient is receiving sufficient analgesia.
  • Patients receiving antispasmodic medications should have blood pressure monitored. These medications, most often prazosin and phenoxybenzamine, are α-antagonists, which relax smooth muscle in the body, including the urethra and blood vessel walls. This can lead to vasodilation and hypotension.
  • Urine output should be monitored closely because these patients will enter a post-obstructive diuresis, during which their urine production can reach 3-5 ml/kg/hr. Fluid rates should be carefully monitored to ensure they are matching urine production.

Take-home points

Veterinary technicians play a key role in the care of blocked cats, starting with patient identification. They can help to stabilize, assist with deobstruction, and monitor patients under anesthesia and in recovery. During the patient’s hospital stay, technicians have the most contact with the patient and can advise the attending veterinarian of concerns related to pain management, blood pressure, and hydration. Liss notes that blocked cats are a rewarding emergency because most patients do well with treatment.

Kate Boatright, VMD, a 2013 graduate of the University of Pennsylvania, is a practicing veterinarian, freelance speaker, and author in western Pennsylvania. She is passionate about mentorship, education, and addressing common sources of stress for veterinary teams and recent graduates. Outside of clinical practice, she is actively involved in organized veterinary medicine at the local, state, and national levels.


  1. Drobatz KJ, Cole SG. The influence of crystalloid type on acid-base and electrolyte status of cats with urethral obstruction. JVECC. 2008;18(4):355-361. doi:10.1111/j.1476-4431.2008.00328.x
  2. Hall J, Hall K, Powell LL, Lulich J. Outcome of male cats managed for urethral obstruction with decompressive cystocentesis and urinary catheterization: 47 cats (2009-2012). JVECC. 2015;25(2):256-262. doi:10.1111/vec.12254
  3. Gerken KK, Cooper ES, Butler AL, Chew DJ. Association of abdominal effusion with a single decompressive cystocentesis prior to catheterization in male cats with urethral obstruction. JVECC. 2020;30(1):11-17. doi:10.1111/vec.12914
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