Stones in my pet’s belly?

By dnp-team On Sep 15, 2014

Many pet parents don’t even know that like humans even their pets can also suffer from urinary stones. Here’s more on this health issue.
Dr. Munmun De
Calculi are formed when the urine is supersaturated with salt and minerals such as calcium oxalate,struvite (ammonium magnesium phosphate), uric acid and cystine. Almost 60-80 percent of stones contain calcium. They vary considerably in size from small ‘gravel-like’ stones, to large staghorn calculi. The calculi may stay in the position in which they are formed, or migrated down the urinary tract, producing symptoms along the way. Some mineral solutes precipitate to form crystals in urine. These crystals may aggregate and grow to macroscopic size, at which time they are known as urolith.
Kidney stones are rare in dogs. But bladder stones are common. Stones that form in the bladder may pass into the urethra.

Terminology…
Urolithiasis is the condition where urinary stones are formed or located anywhere in the urinary system. The term ‘nephrolithiasis’ refers to stones that are in the kidney. And the term ‘cystolithiasis’ refers to stones which form or have passed into the urinary bladder, while the term ‘ureterolithiasis’ refers to stones that are in the ureter. Urolithiasis is the main cause of obstruction in the lower urinary tract.

Types of stones…
There are several different types of calculi like sabulous material or fine sand like, gravel or small concretions resembling coarse sand depending on their chemical constituents. Struvite, calcium oxalate, urate, cystine, calcium phosphate and silicate are very common and can be determined only by calculi analysis like Quantitative Reflectance Fourier Transform, Infrared Spectroscopy, Quantitative Polarising Microscopy, etc in certain labs.

Causes of urinary calculi in dogs…
Genetics: Some physiology of animal’s body is genetically controlled. An inherited condition called hypercalcuria, which leads to large amounts of calcium in urine or an inherited condition called cystinuria may cause calculi in urine.

Concentration of stones: The concentration of these constituents can be influenced by the amount of minerals and protein in your pet’s diet, the amount of water the animal drinks, and the animal’s unique metabolism.

Urine pH: The acidity or alkalinity of the urine influences whether the stone constituents will remain dissolved or form stones. The urine pH is largely influenced by diet.

Bacterial infections: Cystitis due to a bacterial infection plays the major role in stone formation. Bacterial infections tend to make the urine more alkaline, which enhances the formation of calculi.

Symptoms of urinary calculi…

Some pets may show initial signs of haematuria and may urinate frequently, passing only drop by drop urine at times.
Pyuria is also one of the symptoms. Pyelitic urine is always alkaline and contains albumin, pus cells, blood cells renal casts, etc.
Many pets try to urinate but fail to pass urine after they take the posture or lift their legs which is a sign of anuria and sometimes can also show symptoms of oligouria. Difficult micturition dysuria or frequent micturition sychuria or painful micturition can all be an alarming sign.
Pain on external palpation in lumbar region in small animals. It may also be manifested by stiffness on movement. Swelling can also be detected on manipulation.
At home pet parents will witness their pets licking their genital area more than normal.
Some dogs with bladder or renal stones may show no signs at all.

Diagnosis…

Diagnosis is made out of symptoms which are not always characterised.
Initial step would be to send your pet’s urine for a routine urinalysis and urine culture.
In today’s practice an ultrasonography of lower abdomen is of much helpful in evaluation of urinary tract calculi with images of kidney, urinary bladder, uretovesicular junctions, etc. Ultrasound has tremendous value of imaging follow up as well.
The diagnosis of bladder stones in pets is also confirmed with abdominal x-rays. Most stones are radiopaque, meaning they show up on the radiographic film as obvious white circles or shapes. A few are radiolucent, where the x-ray beams pass right through and therefore, they do not show up on the finished film.

Treatment of bladder stones in dogs…
Your vet will take the call, either to treat medically or surgically. Options vary according to the size, type and location of the stone.

(Dr Munmun De, BVSc and AH (Gold Medalist), MVSc, is PhD scholar-surgery and radiology, West Bengal University of Animal and Fishery Sciences, Kolkata).