Animals - Blocked cat

By: Olaf Klein

Urethral obstruction in cats is a fairly common condition encountered in small animal practice. It affects primarily young to middle-aged neutered males. The condition presents itself as unsuccessful attempts to urinate. Restlessness interspersed with frequent squatting without urine flow and pink urine spots in the litter tray are the most frequent indicators. The condition is painful, often due to the very significant bladder distention (enlargement).

The symptoms can go unnoticed until the condition is relatively advanced. In these cases the urine retention has led to a shift in electrolyte balances in the blood and the increase in potassium in particular slows down the heart rate. At this stage, these cases represent a true medical emergency and require a fair bit of time and medical input to resolve. Once the animal is presented at a vet clinic, palpation of the bladder will confirm the distention. X-rays may show sediment in the bladder and ultrasound will give a good indication of bladder wall thickness and inflammation (cystitis). Lab tests, such as a urine culture, will give certainty about bacterial involvement and potassium levels will give an indication of the anaesthetic risk involved to clear the blockage.

The treatment will employ a three-pronged approach. The first step is to resolve the electrolyte imbalances, the second is to release the bladder distention by catheter or cystocentesis (removal of urine via a needle) and the third step is to re-establish urine flow by flushing the urethra with saline solution. The primary reason for these obstructions is usually a combination of things. The urethral plugs that we flush out consist of crystalline minerals from the urine mixed with mucus and epithelial cells from the bladder. Crystal formation in the urine is often caused by changes in the acidity of the urine due to inflammation or high magnesium content of the diet. Narrower urethras in neutered males foster the aggregation of crystals. This in turn leads to irritation of the urethral lining and the urethral muscles respond with spasm, which results in major flow reduction.

Once the condition has resolved, and this may involve a few days of hospitalisation, you want to strictly adhere to feeding your cat a special prescription diet to decrease the risk of your cat getting blocked again. If your cat has shown a predisposition to the disease the recurrence rate is high, especially with sub-optimal diets. Furthermore, the condition is more difficult to resolve second time round because of existing scaring of the urethra.  
If it cannot be resolved in the fashion I described, ureterostomy or the implantation of a urethral stent are solutions which bring their own raft of complications. My advice is be observant and consult your vet early.


Olaf Klein, Wellsford Vet Clinic
www.vetsonline.co.nz/wellsfordvet

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