Veterinary protocol for cats with urinary blockage

Feline urethral obstruction is a life-threatening but treatable emergency that is frequently encountered in veterinary practice. With appropriate management the prognosis is good, with one study indicating a survival rate to discharge of more than 90%.²

Predisposing factors

Male cats have an increased predisposition to obstructive disease compared to females. The higher incidence of male cat urinary blockage is largely due to anatomical differences, namely the longer, narrower diameter male urethra, compared to that of females.

FLUTD, including obstructive disease, is seen most commonly in young to middle-aged cats. Additional predisposing factors include stress, a less active or indoor lifestyle, obesity, and an exclusively dry food diet.

History and physical examination

Cats with obstructive FLUTD tend to be sicker at the time of presentation than those with non-obstructive disease. Clinical signs are summarised in Table 1.

Table 1: Clinical signs of FLUTD

Typical physical examination findings in a cat with feline urinary obstruction are a distended painful bladder which cannot be expressed. Stranguria is the most common clinical sign associated with urinary blockage and owners frequently mistake this for constipation or faecal tenesmus, so it is imperative that a thorough history is obtained, and that clinical examination establishes whether the bladder is empty or full. A full bladder in combination with signs of urinary blockage in cats, is a medical emergency requiring immediate treatment.

As well as assessing bladder size, a full physical examination should be performed to include checking for signs of hypovolaemia (heart rate, pulse quality and blood pressure).

Diagnostics

Due to the emergency nature of obstructive FLUTD, diagnostics, stabilisation and management are usually performed concurrently. Diagnosis should include:

• Emergency database blood profile
• Electrocardiogram
• Urinalysis
• Radiography

> Bloods

Full blood profiles are important to include in all cats with obstructive FLUTD as dehydration, electrolyte imbalances and acid-base balance disturbances are all commonplace. An initial emergency database should include as a minimum:

• Packed cell volume (PCV) and total protein (TP)
• Urea and creatinine
• Serum electrolytes
• Acid-base status if available

Obstructive FLUTD can lead to either renal or post-renal azotaemia. In most cases, azotaemia will resolve with the administration of intravenous fluids together with relief of the obstruction.

Hyperkalaemia is another serious consequence of obstructive FLUTD; it causes bradycardia and cardiac dysrhythmias due to its effects on cardiac conduction. Consequently, hyperkalaemia can be life-threatening and requires urgent treatment.

In cats with bradycardia or arrhythmias, it is particularly important that serum potassium is checked, and any abnormalities corrected before attempting sedation or anaesthesia.

> Urinalysis

Full urinalysis should be performed to aid in determining the underlying cause of obstruction so guiding management and reducing the chance of recurrence. This should include urine specific gravity, dipstick, sediment analysis, and bacterial culture.

Samples should be collected at initial presentation and stabilisation, but priority should be given to emergency care of the patient rather than full urinalysis in the first instance.

> Imaging

Survey radiography or ultrasonography should be performed in all cases of obstructive FLUTD, to rule out causes such as urolithiasis or neoplasia.

Stabilisation

Initial emergency stabilisation is likely to involve a combination of intravenous fluid therapy together with relieving the urinary obstruction.

> Fluid therapy

Fluid therapy should be administered in the form of isotonic crystalloids, with the choice of intravenous fluid depending to some extent on the condition of the individual patient. Some clinicians suggest that potassium-containing fluids (such as Hartmann’s) should be avoided if the cat is hyperkalaemic, in which case 0.9% sodium chloride is the fluid of choice. In reality, correcting hypovolaemia and relieving urinary obstruction may be of greater importance than whether potassium-containing fluids are administered.

> Additional management of hyperkalaemia

In cases where potassium is significantly elevated, additional treatments should be considered in addition to intravenous fluids:

• Calcium gluconate: calcium gluconate acts quickly to protect against the cardiotoxic effects of hyperkalaemia by altering the heart cell membrane action potential threshold. It does not alter serum potassium concentrations and its protective effect lasts for about 20 minutes so other treatment must be instigated concurrently.³
• Intravenous dextrose: administering glucose stimulates endogenous insulin production and this insulin promotes an intracellular shift of potassium. However, the effect of endogenous insulin may be limited, and intravenous insulin may be required in addition to dextrose to help correct hyperkalaemia. Blood glucose and potassium levels should be monitored throughout.
• Bicarbonate: bicarbonate therapy is recommended in cases of severe hyperkalaemia where the patient is acidotic but careful monitoring is required to avoid adverse effects. Bicarbonate should only be administered where blood gas monitoring is available.

> Therapeutic cystocentesis

If emergency decompression of the feline bladder is required and passing a urinary catheter is challenging, therapeutic cystocentesis may be indicated to provide immediate relief. A small gauge needle (25 gauge needle or butterfly) attached to an extension set should be used. The procedure carries a risk of laceration of the bladder wall, especially when the bladder is over-distended so should only be used when necessary. Benefits include:

• Rapid resolution of bladder distension
• Increase in glomerular filtration rate
• Reduction in bladder pressure which may increase ease of urethral catherisation
• Collection of a sterile urine sample for urinalysis

Management of feline urinary blockage

Ultimately, this life-threatening condition is treated by relieving the urinary obstruction and this has to be a priority in managing feline urinary blockage.

Urethral obstruction is a very painful condition and analgesia should be administered at the first opportunity. In all but the most obtunded cats, sedation or anaesthesia will also be necessary. In many cases, anaesthesia is preferable to sedation, because it provides better urethral relaxation which aids passage of the urinary catheter. Many different analgesia, sedation and anaesthesia protocols are discussed in the literature, and it is beyond the scope of this article to cover these. An appropriate anaesthetic regime should be determined by the clinician after thorough assessment of the patient and initial stabilisation.

After checking the tip of the penis for urethral plugs the catheter should be lubricated and gently introduced into the tip of the urethra. Flushing with warm sterile saline allows the catheter to be gently advanced. Repeated flushing may be required to establish urethral patency. Patience is essential and use of force should be avoided to reduce the risk of urethral trauma. For more tips read our article on <Feline urinary catheter placement>

Once the obstruction has been relieved, the bladder should be emptied and flushed with warm sterile saline to remove debris and inflammatory mediators.

Aftercare

An in-dwelling catheter is not required in all cases of obstructive cat FLUTD and should be avoided where possible. Factors that need to be considered in the decision-making process include:

• Ease with which urinary catheter was passed
• Bladder size at presentation
• Whether the patient is systemically ill
• Presence of significant haematuria⁴

Cats with systemic illness are likely to require intensive nursing but with appropriate ongoing care and monitoring, recovery rates are good.

References

1. Johnston SA and Tobias KM (2018). Veterinary Surgery: Small Animal Expert Consult (2nd edn), Elsevier, St Louis.
2. 2. 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
3. Gerardo Polli, December 2017. Hyperkalaemia, pt 2: treatment, Vet Times
4. Susan Little, 2011. Management of cats with urethral obstruction (Proceedings), dvm360