Canine Hydronephrosis

Hydronephrosis is a word for dilation or swelling of one or both kidneys, caused when urine cannot pass out of the kidneys or the body. It's not a disease itself, but a symptom caused by any of a number of conditions that can affect the urinary system of your canine pal. While it can affect dogs of any age, it sometimes is seen in female puppies as a complication of spaying, particularly at an early age. Regardless of the cause, your buddy needs prompt medical treatment.



In rare instances, a spay operation can lead to damage and obstruction of one or both ureters, the tubes that carry urine from the kidneys to the bladder. Hydronephrosis can result from the blockage. The likelihood of this complication is increased in early spays, as it is more difficult to distinguish the ureters of a very young puppy during surgery. Many problems can cause hydronephrosis, however, and it can occur in dogs of any breed at any age. One of the most common causes in adult dogs is stone (calculus) formation in the kidneys or bladder, blocking urine flow. Tumors of the urinary system, blood clots, or abdominal trauma can all cause hydronephrosis.


Symptoms associated with hydronephrosis can vary widely. You may note that your puppy's abdomen appears enlarged or distended, or that she seems uncomfortable when lying down or moving around. She may begin leaking urine, or urinating in the house despite being housebroken. Blood in the urine may signal a tumor of the urinary system, a clotting disorder or an infection, any of which can wind up causing hydronephrosis. If kidney function is affected, you may notice more severe signs, such as vomiting, loss of appetite or increased thirst and urination.


Your dog's veterinarian generally will make use of abdominal ultrasound to diagnose hydronephrosis. Ultrasound may also identify the abnormalities of the urinary tract, such as tumors or calculi, that caused the problem. Other important tests done in conjunction with the ultrasound may include blood work to assess the function of the kidneys, urine analysis and culture to rule out infection, and abdominal X-rays (radiographs) to identify any abnormalities ultrasound can't detect.


The treatment of canine hydronephrosis varies, depending on the cause and severity of the condition. Treatment often includes hospitalization for fluid and medication administration if the kidneys are affected, and may include antibiotic therapy if infection is diagnosed. If damage to the ureter or a blockage by a stone caused the problem, surgery may be necessary. Your veterinarian may prescribe dietary changes to prevent further calculus formation. If a tumor is the cause, your vet may recommend a treatment such as chemotherapy.


It is important to remember that hydronephrosis is a symptom caused by an underlying disease, not a disease itself. Treatment should focus on resolving the underlying problem. Although the kidney structure and function may not completely return to normal after treatment, it is possible for the symptoms to cease, and for your dog to return to a normal life.

By Amanda Fulmer

About the Author
Amanda Fulmer is a veterinarian in Greenville, S.C. who earned specialty certification in medical oncology in 2008. She received a veterinary degree and advanced oncology training from Louisiana State University. Her scientific research has been published in several professional veterinary journals. She also lectures around the country on various topics in her field.