Improving outcomes in feline urethral obstruction
Dr. Natalie Stilwell provides freelance medical writing and aquatic veterinary consulting services through her business, Seastar Communications and Consulting. In addition to her DVM obtained from Auburn University, she holds a MS in fisheries and aquatic sciences and a PhD in veterinary medical sciences from the University of Florida.
According to emergency critical care specialist Dr. Justine Lee, this common condition offers both challenges and rewards for the veterinarian.
“It still saddens me that cats are euthanized or found dead from being blocked,” said Justine Lee, DVM, DACVECC, DABT, at the start of her lecture at Fetch dvm360 conference in Baltimore. Dr. Lee explained the importance of stabilization, continuous monitoring and analgesia for a successful patient outcome in cats with feline urethral obstruction (FUO), a serious but common emergency condition.
FUO usually presents in overweight to obese male cats ranging in age from 2 to 6 years, although the condition can occur in older individuals, particularly those with underlying disease. Most cases of FUO are idiopathic (53%), whereas fewer cases are caused by uroliths (29%) or urethral plugs (18%) composed of crystals, cells, protein or amorphous material.1
“It's very important that we take the time for historical questions and education,” Dr. Lee said. The patient's medical history, clinical signs, diet and litterbox history can all provide a better understanding of the patient's status. For example, she noted, “indoor/outdoor cats are more likely to present critically ill because owners have no idea if the cat is urinating outside.”
Cats may present due to inappropriate elimination, dysuria, pollakiuria, stranguria, hematuria and/or constipation. In addition, FUO can cause lethargy, anorexia, dehydration and severe pain. Although “the majority of cats present stable,” according to Dr. Lee, “approximately 10% to 12% are critically ill” and are typically obtunded, bradycardic and hypotensive. “Any vomiting cat is immediately triaged back to the emergency room,” she added.
Abdominal palpation will typically reveal an enlarged, firm and non-expressible urinary bladder. Because acid-base imbalances can cause cardiac conduction abnormalities or arrhythmias, baseline blood work and a lead II electrocardiogram should be prioritized above other diagnostics. Also, imaging may help identify calculi, uroabdomen or urinary masses.
If available, blood work should include packed cell volume, total solids, blood urea nitrogen, blood glucose, venous blood gas and electrolytes (e.g. sodium, potassium and ionized calcium). Dr. Lee noted that FUO usually leads to hemoconcentration, hyperglycemia, azotemia, hyperkalemia and, less commonly, anemia.
If the client is limited financially, Dr. Lee advised “when in doubt, allocate your resources toward treatment rather than diagnostics.”
Mainstays of FUO treatment
Initial stabilization with aggressive fluid and emergency drug therapies
Alleviation of the obstruction while the patient is under sedation
Symptomatic/supportive care (e.g. antibiotics, antispasmodics)
The first step of treatment is to stabilize the patient by addressing likely hyperkalemia, dehydration, azotemia and anticipated postobstructive diuresis. “If you have a dying, blocked cat right in front of you, you don't need to unblock it. You need to stabilize it,” Dr. Lee said.
Begin with either 50 to 100 mg/kg of 10% calcium gluconate or 1 to 2 mEq/L of sodium bicarbonate to provide a cardioprotective effect against hyperkalemia. Either solution should be administered as a slow intravenous (IV) infusion. Dr. Lee prefers not to use insulin:dextrose for this step due to the risk for hypoglycemia; if insulin is preferred, however, only short-acting insulin should be used.
Also, a 60- to 100-mL fluid bolus of a balanced, buffered isotonic crystalloid should be administered over 30 minutes (or longer for patients with cardiopulmonary disease). This step of fluid therapy is essential to counteract the 50% chance of severe diuresis following unblocking, Dr. Lee said.2
Aggressive maintenance fluid therapy should continue after unblocking until clinical signs resolve. Dr. Lee recommended a rate of 60 mL/hr for most cases; administer 50 mL/hr for patients with a gallop rhythm or 40 mL/hr for those with a heart murmur. Fluid input and output monitoring is essential after alleviation of urinary obstruction. Normal urine output is 1 to 2 mL/kg/hr; however, some diuretic cats may urinate 50 to 100 mL/hr.
All but the most critically ill patients should be sedated for urinary catheterization. Only choose quick-acting, reversible and cardiovascular-sparing medications. “Make sure you're well prepared and have everything set up before you unblock,” Dr. Lee added. She prefers a combination of butorphanol (4 mg IV per cat), diazepam (2.5 mg IV per cat) and ketamine (10 mg IV per cat). For critically ill patients, only butorphanol and diazepam are used and at half-strength.
Alleviation of urinary obstruction
Although the preferred method to alleviate urethral obstruction is clinician dependent, Dr. Lee recommended choosing soft, pliable catheters to avoid trauma to the already inflamed urethra. Equally important are the use of aseptic technique and a closed collection system to reduce the risk of ascending infection.
She prefers initial use of a tomcat sterile polypropylene catheter, with added traction on the prepuce to straighten the pelvic flexure. Copious flushing during placement will help dislodge the obstruction either out of the urethra or backward into the bladder. The tomcat catheter is then removed and immediately replaced by an indwelling, 3.5- to 5.0-Fr red rubber catheter, sutured in place with a Chinese finger trap and followed with more flushing. Next, confirm correct placement of the catheter via radiography or measurement.
Dr. Lee noted that decompressive cystocentesis (DC) is necessary occasionally for patients that cannot be unblocked via catheterization; however, some practitioners choose to follow DC with catheterization and supportive hospital care, rather than using it as the sole treatment for FUO.3 One study suggested that DC, when combined with a “stress-free” environment and pharmacotherapy, offers an effective, low-cost alternative to euthanasia.4 She countered that repeated DC increases the risk of hemoperitoneum or uroperitoneum.
Analgesia should be provided while the urinary catheter is in place. Dr. Lee prefers buprenorphine (11-22 µg/kg IV every six hours) or long-acting buprenorphine (Simbadol, Zoetis), which is typically dosed either based on lean body weight or at half-dose (0.12 mg/kg subcutaneously once daily for three days). Also, 100 mg oral gabapentin can be initiated approximately one to two hours after waking and dosed two to three times daily.
If needed, acepromazine (0.005-0.01 mg/kg IV) can be added as an anxiolytic and to relieve urethral spasm. For some patients, Dr. Lee also performs a coccygeal block for additional, albeit short-lived, analgesia. Pain should be monitored closely throughout hospitalization. “If the patient is hissing and aggressive, he needs more pain meds,” she asserted.
Once the patient has been stabilized, unblocked and provided with analgesia, the remaining components of hospitalization involve symptomatic and supportive care. Monitoring of fluid input and output, blood pressure, and nutrition and hydration status is indicated. Dr. Lee recommended performing daily renal panels during hospitalization for all patients and electrocardiographic monitoring for critically ill cats. All patients should wear an Elizabethan collar during recovery.
The urinary catheter should be flushed copiously during removal, usually 24 to 72 hours after placement or once urine appears normal. Patients are typically discharged once they urinate on their own and azotemia and dehydration are resolved.
Dr. Lee prefers to reserve antibiotic therapy for after catheter removal, due to the risk for developing resistant urinary tract infection (UTI) with antibiotic prophylaxis during catheterization. However, she added that urine culture and antibiotics should be pursued promptly if the patient shows any signs of a UTI, such as a fever, bacteriuria or renal pain.
Antispasmodic therapy with smooth (e.g. prazosin, phenoxybenzamine) or striated (IV diazepam) muscle relaxants can be used to treat urethral spasm, a particularly common issue with tight-fitting catheters.
Communication with clients is an essential component of FUO therapy, beginning at initial presentation and continuing throughout hospitalization and the follow-up period. Although patients with FUO have a 90% to 95% survival rate,5 clients still need to understand the critical nature of the condition and the high risk for associated complications.
Reobstruction occurs in 19% to 25% of FUO patients. Depending on the underlying cause, the cat may require surgical correction and/or modifications to diet, litterbox husbandry and lifestyle to prevent recurrence. Dr. Lee prefers to switch FUO patients with chronic renal issues to a grueled, canned diet to provide additional water intake. Also, several litterboxes should be made available to recovering cats, and changed at least once daily, to reduce the risk of repeated obstruction.
1. Reineke EL. Feline urethral obstruction: Emergency treatment and stabilization. In Proceedings. 85th West Vet Conf 2013.
2. Francis BJ, Wells RJ, Rao S, et al. Retrospective study to characterize post-obstructive diuresis in cats with urethral obstruction. J Feline Med Surg 2010;12:606-608.
3. Hall J, Hall K, Powell L, et al. Outcome of male cats managed for urethral obstruction with decompressive cystocentesis and urinary catheterization: 47 cats. J Vet Emerg Crit Care 2015;25(2):256-262.
4. Cooper ES, Owens TJ, Chew DJ, et al. A protocol for managing urethral obstruction in male cats without urethral catheterization. J Am Vet Med Assoc 2010;237(11):1261-1266.
5. Lee JA, Drobatz KJ. Characterization of the clinical characteristics, electrolytes, acid-base and renal parameters in male cats with urethral obstruction. J Vet Emerg Crit Care 2003;13(4):227-233.