Fluid Buildup in the Kidney Due to Kidney or Ureter Obstruction in Dogs

By PetMD Editorial on Aug. 31, 2009

Hydronephrosis in Dogs

Hydronephrosis is usually one-sided and occurs secondary to complete or partial obstruction of the kidney or ureter by kidney stones, tumor, retroperitoneal (the anatomical space behind the abdominal cavity), disease, trauma, radiotherapy, and accidental binding of the ureter during spaying and after ectopic ureter surgery.

In most patients, hydronephrosis occurs when fluid builds up in the kidney, causing progressive distention of the renal pelvis (the funnel-like dilated proximal part of the ureter in the kidney) and diverticula (out pouching, with atrophy of the kidney secondary to obstruction).

Bilateral hydronephrosis (distention and dilation of the renal pelvis) is rare. When it does occur, it is usually secondary to trigonal (a triangular smooth area at the base of the bladder), prostatic, or urethral disease.

Symptoms and Types

Some dogs may be without overt symptoms, while others may display one or many of the following:


Any cause of ureteral obstruction:

  • Kidney stones
  • Ureteral stenosis (narrowing of the ureters)
  • Atresia (closed)
  • Fibrosis (formation or development of excess fibrous connective tissue)
  • Tumor
  • Trigonal mass
  • Prostatic disease
  • Vaginal mass
  • Retroperitoneal (anatomical space behind the abdominal cavity) abscess, cyst, hematoma, or other mass occupying this space
  • Accidental ureteral ligation during spaying
  • Postoperative complication from ectopic ureter surgery
  • Perineal hernia (abnormal displacement of pelvic and/or abdominal organs into the region around the anus called the perineum)
  • Secondary to congenital ectopic ureters


You will need to give your veterinarian as much information on your dog's health and recent activities as possible. Your veterinarian will perform a complete physical exam on your dog after taking a thorough medical history from you. Standard laboratory tests include a blood chemical profile, a complete blood count, an electrolyte panel and a urinalysis to rule out or confirm other causes of disease.

Abdominal X-rays and an ultrasound are important tools for diagnosing hydronephrosis and its underlying cause. Also essential is a transurethral urethrocystoscopy or vaginoscopy, procedures that are performed using a small camera to visualize the inside of the vagina or the urethra (two tubes which drain from the kidneys to the bladder).




Your dog will be treated on an inpatient basis and will be started on supportive care (e.g., fluids and antibiotics) while diagnostic testing is performed. Correction of fluid and electrolyte deficits will be undertaken using intravenous fluid therapy over four to six hours, followed by maintenance fluids as needed. If your dog is exhibiting extreme polyuria, (excessive urination), higher maintenance fluid rates will be necessary for replacing those being excreted.

Relieving the lower urinary tract obstruction as soon as possible by catheterization will be a foremost priority, along with serial cystocentesis. Cystostomy is the surgical formation of an opening through the abdomen into the urinary bladder using a tube-like structure. Any obstructions should then be surgically corrected as soon as is possible.

Your veterinarian will discuss with you the possible presence and implications of renal disease and the possible need for surgery should it be diagnosed. Specific treatment (usually surgical) depends on the cause of the disease and whether there is concurrent renal failure or other disease process at work (e.g., metastatic cancer). Emergency surgery is rarely required for renal disease. Kidney removal is generally not necessary unless is is infected or cancerous. If mild disease is secondary to the kidney stones, extracorporeal shock wave lithotripsy, which uses shock waves to break up the kidney stones, may be used as an alternative to surgery.

Ureteral stents have also been used experimentally in dogs. These are hollow, plastic tubes that are surgically placed between the kidney and the bladder, functioning to hold the ureter open to allow normal drainage of urine.

Living and Management

Your veterinarian will schedule follow-up appointments with you every two to four weeks after the obstruction has been successfully removed in order to monitor your dog's progress. Bloodwork will be taken at these appointments to be sure that the blood urea nitrogen and blood creatinine levels have fallen to normal levels. If you notice that your dog is urinating excessively and/or losing weight after the obstruction has been removed, contact your veterinarian for a further examination.

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