Blood in the urine (hematuria) of male dogs: Kidneys & Ureters

Causes of hematuria from the upper portion of the urinary tract:

The upper portion of the urinary tract includes the kidneys and ureters. The ureters are thin, flexible tubes that carry urine all the way from the dog’s back near the ribs to the bladder in the distal pelvis. Bleeding can occur from anywhere along the ureters or in the kidneys, especially if there are stones or material that damages the delicate tissues.

In some dogs the stones are so large they plug the ureters and prevent urine from flowing down to the bladder. The fluid builds up in the kidney causing the ureter and kidney to become swollen. These blockages cause extreme pain and are best seen with X-rays. When blockage causes swelling, the dog is diagnosed as having a hydroureter or hydronephrosis.

Some breeds are prone to developing stones. For example, Labrador Retrievers have a genetic tendency to develop cystinuria. With cystinuria, the kidneys don’t resorb certain amino acids (cysteine, ornithine, arginine, and lysine) and these amino acids are excreted into the urine where they precipitate and form crystals or stones. With Labrador Retrievers prone to cystinuria (cystine is an oxidized form of cysteine), as with any breed prone to stones, water intake is increased. Because acidic urine reduces cystine stone formation, these dogs are given acidic materials such as increased meat and potassium citrate. Other types of stones are treated differently, some by materials that alkalize the urine. Cystine stones are diagnosed with X-ray or ultrasound, but not all types of stones are visible on X-rays.

Other conditions that cause swelling and bleeding from the upper urinary tract include infections and tumors. These can destroy blood vessels and cause blood in the urine. For example, German Shepherds are prone to developing a kidney cancer called renal cystadenocarcinoma. Other forms of cancer, such as lymphosarcoma can also occur in the kidneys. Tumors are sometimes visible with X-rays and sometimes not visible. Infections are not visible but they may cause significant swelling that is visible. Leptospirosis is a common cause of kidney infections and it—as with other kidney infections—is best diagnosed by culturing the urine.

While kidneys can be swollen and large, they can also be shrunken and small. Chronic kidney disease often leads to shrunken, irregularly shaped kidneys. Genetic diseases, such as polycystic kidney disease lead to irregularly shaped, nonfunctioning kidneys, and may cause blood in the urine.

Some breeds, such as the English Springer Spaniel, have a genetic tendency to phosphofructokinase deficiency. This deficiency leads to hematuria when they exercise. It appears that Springer Spaniels exhale enough CO2 with heavy exercise that the pH changes and becomes alkalotic, causing hematuria. Welch Corgis also have a genetic tendency to unexplained renal hemorrhage, but the exact mechanism is unclear.

Genetic disease, infections, and cancer are not the only causes of hematuria, in fact, they are probably less common than trauma, poisoning, and medication-caused hematuria. For example, dogs hit by cars, dogs that consume anti-coagulant rodent poisons, and dogs on NSAID medications, such as Rimadyl, are predisposed to bleeding. Dogs that find their family’s NSAID medications (Ibuprofen, Aspirin) can also develop hematuria.

Now that causes for bleeding from the upper and lower urinary tract have been explored, the next blog will look at another cause of hematuria that appears as blood in the urine but is not actually blood in the urine. Unfortunately, it is very common.

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