Key Point

Underlying causes of bladder stones should always be investigated by your veterinarian

Some bladder stones may dissolve with a prescription diet; if the stones do not dissolve after a six week trial with a stone dissolution diet, then surgery is recommended

Surgical removal of the stones is frequently required to alleviate clinical signs

Prognosis is good following surgery, however, stone recurrence can be a problem if no additional treatment or dietary

Anatomy The urinary system is made of the kidneys, the tubes (ureters) that pass urine from the kidneys to the bladder, the bladder which is a reservoir for urine, and the urethra, which is the tube that drains urine from the bladder to the outside. The urethra in males is fairly long and a portion of it runs through the tissue of the penis. In dogs the penis has a bone (os penis) that surrounds the urethra for part of its length. The diameter of the urethra narrows as it passes through the os, therefore stones frequently get lodged in this region.

Why do stones form?

A bacterial infection of the bladder will cause an increased breakdown of urea to ammonium, thus struvite stones can form

Oxalate stones may form if the pet has a tumor of the parathyroid gland or another type of cancer. Calcium oxalate stones can form if there is a kidney defect that allows more oxalate to be secreted in the urine than normal. Some Schnauzers are born with a defect that predisposes them to calcium oxalate stone formation

Ammonium biurate stones form if the pet has a liver disease such as a portosystemic shunt.

Urate stones form in Dalmatians due to a defect in metabolism (see photo right).

Some diets encourage stone formation.

Diagnostic tests

Complete blood cell count and chemistry profile of the blood are run to check the health of the internal organs and to look for underlying causes of the bladder stones.

Other tests may include urinalysis and culture of the urine, ultrasound of the bladder and the kidneys, and x-rays of the abdomen may be taken to indentify the stones.

Radiograph right – note the multiple round white appearing stones in the bladder

Surgery

An incision is made in the lower part of the belly over the bladder. An incision is then made in the bladder and the stones are retrieved (photo right). It is very important to flush the urethra to ensure that all stones have been removed. Sometimes a small stone can hide in the crypt of the prostate and will then fall back into the bladder. This is not common, but results in a stone being left in the bladder, thus surgery will be needed again.

Laparoscopic cystostomy can be performed in many centers which involves making a single incision in the abdomen to retrieve stones. This procedure is less painful for the patient allowing for a quicker recovery.

A radiograph should always be made of the bladder and urethra to confirm that all stones have been removed after the surgery.

Potential complications

Even though rare, anesthetic death can occur. With the use of modern anesthetic protocols and extensive monitoring devices (blood pressure, EKG, pulse oxymetry, inspiratory and expiratory carbon dioxide levels, and respiration rate), the risk of problems with anesthesia is minimal.

Straining and frequent urination of small amounts of urine for 7 to 10 days after surgery is expected. This is due to irritation of the bladder from the surgery. The urine may also appear to be blood tinged for the first week after surgery.

Recurrence of stones may take place if the underlying condition is not treated; some stones are more prone to recurring regardless of what is done (Schnauzers with calcium oxalate stones). A special diet may be recommended in some cases to prevent stone reformation.  In male dogs a urethrostomy may be recommended if the stones are expected to recur; this procedure will help prevent the stones from getting lodged in the penis.

Breakdown of the sutured incision in the bladder is very rare, but can make the pet very ill due to leakage of urine in the belly cavity.

Suture reaction may cause chronic irritation of the bladder (rare complication), thus necessitating another surgery.

Infection is an uncommon complication.

rev 10/5/11