East Lincoln Animal Hospital

7555 Highway 73 East
Denver, NC 28037



"Oreo" - Case of the month - Bladder stones

Oreo is a 12-year-old Springer Spaniel who had been having recurrent urinary tract infections. After the most recent infection, his bladder was radiographed and we found that Oreo had bladder stones.
Oreo had blood work performed to check his kidney and liver function and his red blood cells, white blood cells, and platelets in preparation for surgical removal of the bladder stones. His blood work was normal and on his day of surgery, Oreo had an intravenous catheter placed and was hooked up to intravenous fluids to support his kidney function and help maintain his blood pressure during anesthesia and surgery (see "Is Anesthesia Safe?").

Oreo had a cystotomy performed (we opened up the bladder) to remove the bladder stone. Here are some pictures of his surgery:                                    

Stones in Oreo's bladder

Bladder was thick and inflamed from the stones.

After surgery, Oreo recovered uneventfully. He had to urinate frequently after his surgery because his bladder was so thickened and inflamed from the stones but that soon passed. His urine was cultured for bacteria and his stones were submitted to the lab to find out what type they were. Knowing what type of stones a dog has can help us change the diet or add medications to help prevent the stones from reoccurring. His stone analysis came back as mixed struvite and calcium oxalate stones.
Struvite stones are often caused by repeated bladder infections. Struvite crystals are made of Ammonium, Magnesium, and Phosphate. A normal dog may have struvite crystals in the urine and in small amounts they do not cause problems. When the struvite crystals are present in large amounts, they may form stones. You may wonder how this occurs. Urea is an important biochemical excreted in urine.  When urine is infected with bacteria that are able to digest urea, urea is broken down into ammonia (NH3).  Ammonia in water ionizes into ammonium (NH4+).  Ammonia is toxic to the cells of the bladder wall and its presence generates inflammation (the infection can also generate inflammation).  The proteins released in the inflammatory reaction form a matrix which the struvite crystals use to form a stone.  The reaction takes place only in an alkaline pH.  The presence of ammonia creates just the alkaline pH needed for stone formation.
Calcium oxalate stones are cause by a hereditary defect or another disease. Both humans and dogs can have defective nephrocalcin (a glycoprotein in the urine which inhibits the formation of calcium oxalate crystals) which may cause calcium oxalate stones to form. Hyperadrenocorticism (Cushing's disease) or hyperparathyroidism may cause increase elimination of calcium in the urine and the formation of calcium oxalate stones.
Our plans to control Oreo's mixed struvite and calcium oxalate stones are:
1.       Diet change - Oreo will be eating Hills Science Diet U/D formula. This diet is formulated to create a urinary environment with minimum calcium and oxalate excretion and creates a pH (acidic) not favorable for calcium oxalate formation. 
2.       Urinalysis - We will monitor his urine for any infections to prevent struvite stones from forming.
3.       Radiographs - we will periodically x-ray his bladder to check for any stones.
4.       If the diet is not working to keep the urine PH acidic and prevent calcium oxalate crystals from forming, we will add potassium citrate to his treatment plan. The potassium citrate tablets will help increase citrate levels in the urine and calcium binds to citrate instead of oxalate. Calcium citrate stays dissolved and can be eliminated in the urine whereas calcium oxalate precipitates into a mineral (therefore a stone). Potassium citrate also helps by making the urine pH alkaline which helps to prevent calcium oxalate stones from forming.
Oreo was a good boy during his work up and surgery. He handled everything we did to him with a smile on his face.
He even still likes to come see us and beg for treats!