Clinical Diagnosis, Treatment and Prevention of Feline Urethral Obstruction

Urethral obstruction (UO) is one of the most common and urgent clinical conditions, mostly occurring in young male cats. It is a disease caused by urethral blockage that prevents normal urination, which can rapidly induce life-threatening hyperkalemia and acute kidney injury. The main inducement is urethral embolism caused by feline lower urinary tract disease (FLUTD)/feline interstitial cystitis (FIC); in addition, urolithiasis and other rare diseases may also cause the disease. Timely identification and intervention can avoid serious metabolic and cardiovascular complications, directly determining the morbidity and mortality of affected cats. The use of standardized diagnosis and treatment protocols can improve the success rate of treatment, with the discharge survival rate of affected cats reaching more than 90%.

Cats with urethral obstruction often show non-specific clinical symptoms such as anorexia, vomiting, and lethargy. Some cat owners may report more specific urinary symptoms, such as dysuria, painful urination, and hematuria. A typical physical examination finding is a palpable, firm, tender, and distended urinary bladder; at the same time, most affected cats are dehydrated, and some may experience bradycardia.

Urethral obstruction leads to rapid overdistension of the bladder, which in turn causes bladder damage and even the risk of bladder rupture. Increased intravesical pressure is transmitted to the kidneys, resulting in decreased renal blood flow and filtration function, leading to a sudden rise in blood potassium levels, metabolic acidosis, and azotemia. Without timely active treatment, affected cats may develop fatal bradycardia within 24 hours. Although female cats may also show symptoms related to feline interstitial cystitis (such as painful urination), male cats have a longer urethra that narrows sharply at the end of the penis, making urethral embolism secondary to lower urinary tract edema or crystalluria more likely to cause urethral obstruction.

The focus is to test the examinee's ability to identify emergency diagnostic items, with priority given to the following three:

Hyperkalemia is the most urgent threat, and arrhythmia caused by sustained elevation of blood potassium may lead to cardiac arrest. Intravenous infusion of calcium gluconate can temporarily provide cardiac protection; continuous intravenous infusion of short-acting insulin combined with glucose alone, terbutaline, or sodium bicarbonate can also temporarily reduce blood potassium ion concentration.

Post-renal azotemia, acute kidney injury, dehydration, and shock can all lead to azotemia and hyperphosphatemia. Relieving urethral obstruction and intravenous fluid replacement with crystalloids to promote renal filtration can alleviate azotemia in most cases.

When blood potassium levels rise to the dangerous range, characteristic changes will appear on the electrocardiogram, including peaked T waves, flattened or absent P waves (i.e., atrial standstill), followed by secondary bradycardia. In a few affected cats, the heart rate may remain normal due to sympathetic excitement, but the characteristic abnormalities on the electrocardiogram will still persist. Auxiliary diagnostic items such as complete blood count, full set of biochemical tests, blood gas analysis, targeted ultrasound examination, and blood pressure monitoring are also important components of the initial assessment of the cat's condition.

Cats with urethral obstruction suffer severe pain. Full μ-opioid agonists (such as methadone, hydromorphone) are preferred; if such drugs are not available, buprenorphine can be selected. Non-steroidal anti-inflammatory drugs should be avoided to prevent worsening the already impaired renal function of the affected cat.

Immediately establish an intravenous access and start fluid replacement. Based on the preliminary diagnosis results, if the affected cat has hyperkalemia, symptomatic treatment should be given in a timely manner. At the same time, manage shock-related indicators such as hypotension and hypothermia. After sedating the affected cat, cystocentesis decompression can be performed; if the affected cat is critically ill, the operation can be performed directly upon admission, with the core requirement of keeping the affected cat still. This operation can quickly relieve bladder distension, reduce intraurethral pressure, and create conditions for subsequent catheterization.

Catheterization should be performed under anesthesia, and the choice of anesthetic drugs should be determined according to the severity of the cat's condition. Benzodiazepines help relieve urethral spasm; caudal epidural anesthesia can reduce the dosage of anesthetic drugs and improve the success rate of catheterization. During the operation, a fully lubricated soft urinary catheter should be used, and the operation must be gentle. Short-term indwelling catheters should be sutured and fixed, with a closed urine collection system for continuous urine drainage. After relieving the obstruction, gently flush the bladder with normal saline.

After the cat's condition is stabilized and the obstruction is relieved, the diagnostic process should be further improved: take abdominal X-rays to confirm the correct position of the catheter and check for radiopaque uroliths; collect urine samples before catheter flushing for a full set of urinalysis and urine culture (if necessary) to determine whether the affected cat has urinary system infection and crystalluria.

Continue intravenous infusion of crystalloids, administer analgesics (buprenorphine combined with gabapentin, if necessary), and review blood indicators regularly until they return to normal. Electrolytes should be monitored frequently, every 2-4 hours before returning to normal, and adjusted to every 8-12 hours after returning to normal; if the blood gas indicators of the affected cat are abnormal at the initial diagnosis, blood gas should be reviewed to assess whether acidemia is relieved; renal function indicators should be reviewed daily.

Some affected cats will experience obvious post-obstructive diuresis. Urine output should be monitored every 1-2 hours, and the lost body fluids should be supplemented by adjusting the intravenous fluid rate to avoid dehydration of the affected cat and adapt to diuretic needs. As the cat's condition stabilizes, gradually adjust the fluid replacement rate. In addition, measures such as drug intervention, environmental optimization, and standardized operation should be taken to minimize the stress response of the affected cat during hospitalization.

After the catheter is indwelled for at least 24 hours, the suitability for removal can be judged based on the following four indicators:

After catheter removal, it is necessary to confirm that the affected cat can urinate independently and smoothly. Considering that catheterization may cause iatrogenic infection, urine culture can be performed after catheter removal. At discharge, prescribe short-term oral analgesics according to the cat's condition, and antibiotics if necessary.

The lifelong recurrence risk of feline urethral obstruction is as high as 50%. Cat owners should be reminded of the related risks and symptoms of disease recurrence, and informed of intervention measures to reduce the recurrence rate. Prevention methods include: increasing the cat's water intake (feeding wet food, using water fountains, placing more water bowls); reducing stress factors (especially paying attention to environmental changes, such as the number and cleanliness of litter boxes); if the affected cat has crystalluria, feeding urinary prescription food.

For cats with recurrent urethral obstruction, perineal urethrostomy (PU) can be considered, but this operation is invasive and may cause complications, so it is not the first-choice treatment. If the affected cat has uroliths, cystotomy should be performed to remove the stones after the condition is completely stabilized and blood indicators return to normal, and the operation should be completed before catheter removal to avoid immediate recurrence of obstruction after surgery. After stone removal, component analysis should be performed to determine the type of prescription food that the affected cat needs to eat for a long time.

Cat owners should be guided to understand that stress is the main inducement of feline interstitial cystitis, and provide them with multi-faceted preventive suggestions such as environmental adjustment, dietary management, and drug intervention.