Kidney and Bladder Stones in Cats and Dogs: Causes, Diagnosis, and Treatment

by Mariana Burgos

Metabolic kidney stones are those that occur as a result of an imbalance in the blood or urine. Kidney and bladder stones are far more prevalent in dogs and cats than in humans.

The explanation for this might simply be due to dogs’ and cats’ quadruped posture, according to Harriet M. Syme in her article, “Stones in cats and dogs: What can be learnt from them?”. She claims the bladder’s most reliant region is ventral, which may favor the preservation of crystal aggregates or extremely tiny stones and their eventual progression into clinically visible uroliths (kidney stones).

Urinary stones (urolithiasis) are a major cause of lower urinary tract illness in dogs and cats. The production of bladder stones (calculi) is linked to the precipitation and crystallization of a number of minerals, according to the article, “Urinary Stones” of the American College of Veterinary Surgeons’ (ACVS) website. Urinary stones are caused by a variety of reasons. Understanding these mechanisms is critical for the treatment and prevention of urinary stones.

Causes
The ACVS says that the possible causes of these stone formations may be attributed to the following:

• a high salt content in urine
• retention of these ions and crystals in the urinary system for an extended length of time
• a pH that is ideal for salt crystallization
• a structure for crystal formation
• a reduction in the body’s natural inhibitors of crystal formation.
  They claim that if the diet of the pet companion is high in minerals and protein but the animal is taking less water, that would lead to increased salt saturation in the urine.
  So, this means that it is not a good practice that if your pet is eating wet food often, you would think less to monitor its water intake. And, this is usually the mentality of a number of pet owners I know. Now we know, giving a diet of wet food to our pets does not mean we can forget about giving them water on a daily basis.

Signs and Symptoms
According to ACVS, the symptoms that your pet may exhibit are determined on the location of the urinary stones. The majority of urinary stones are found in the urinary bladder or urethra, with only a tiny fraction stuck in the kidneys or ureters. Urinary stones can cause inflammation by causing damage to the lining of the urinary system. This inflammatory response may predispose your pet to a bacterial urinary tract infection (UTI).
If the stones are in the bladder, symptoms may include the following:

• pee with blood in it
• struggling to urinate
• urinating regularly in tiny amounts
• abdominal pain
• urinary mishaps
  If the stones are in the urethra, you may see these signs:
• urine dribble
• straining or posturing to pee but producing no urine
  According to ACVS, the stones can also become stuck in the ureter (the section of the urinary tract that transports urine from the kidney to the bladder), producing a blockage that can lead to catastrophic kidney damage. If your pet exhibits any of the following symptoms of a urinary blockage, you should seek veterinarian assistance right away.
  Ureteral stones can be identified by the following symptoms:
• abdominal pain
• reduced appetite
• lethargy
• vomiting
• blood in the pee

Diagnostics
Your primary care veterinarian will almost certainly advise you to have your pet’s blood and urine tested. He or she may also recommend that an ECG be performed. Your veterinarian may also want to culture not only the urine but also the bladder lining or the urolith (bladder stone).
ACVS tells us that the most often used imaging techniques are X-rays (radiography) and ultrasound. Most, but not all, stones will be seen on radiographs. Stones that do not show up well on conventional radiographs can be identified by inserting a contrast agent and/or gas into the urinary system, commonly by a urinary catheter.
Ultrasound examination is particularly effective in evaluating the kidneys, ureters, and bladder, but it has limited capacity to check the urethra. Nuclear scintigraphy, a non-invasive technology for analyzing renal blood flow and function, has also recently been employed.

Treatment
Stones made of calcium oxalate, urate, cystine, or silicate cannot be dissolved and must be removed through operation. Struvite stones can be dissolved on occasion by giving your pet a commercially prepared diet (e.g., Hill’s S/D). This type of diet is specially created for this purpose and should be discontinued once the patient is cured, according to ACVS.
Urinary blockage caused by urethral stones is a medical emergency. The urinary blockage must be removed in order for the bladder to empty, or the bladder must be drained using cystocentesis (a treatment in which a needle is inserted through the abdominal wall into the distended bladder and the urine is extracted using a syringe).
Stones stuck in the urethra can often be removed and driven back into the urinary bladder by flushing the urethra with a urinary catheter, a procedure known as retrograde urohydropulsion.

Aftercare and Results
ACVS reminds us that the specific aftercare will be determined by the location of the stones as well as the operation that your pet underwent. Your veterinarian will provide you and your pet precise advice. Most dogs recovering from bladder surgery should be restrained for the first two weeks. To prevent self-trauma at the surgical site, your pet may need to wear an E-collar. You should keep an eye on your pet following surgery to ensure proper urine flow and a return to normal appetite and activity levels. For the first week or two following urinary surgery, it is normal for pets to have a tiny quantity of blood in their urine.

About the Author: Mariana Burgos is a freelance artist. She has been a solo parent for 16 years now because she is wife to a desaparecido. She and her daughter are animal lovers and are active in advocating not only human rights but the rights of animals as well.

This article also appears in the Manila Standard