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

Hydronephrosis in Dogs

Hydronephrosis in dogs typically manifests unilaterally and arises as a consequence of complete or partial obstruction within the kidney or ureter. Such obstructions can result from kidney stones, tumors, retroperitoneal ailments, trauma, radiotherapy, or inadvertent ureteral binding during surgical procedures like spaying or ectopic ureter surgery.

In most canine cases, hydronephrosis develops due to fluid accumulation in the kidney, leading to progressive distention of the renal pelvis and the formation of diverticula. Consequently, kidney atrophy may occur as a consequence of the obstruction.

Bilateral hydronephrosis, characterized by distention and dilation of the renal pelvis, is an infrequent occurrence. When bilateral hydronephrosis does arise, it typically stems from conditions affecting the trigonal, prostatic, or urethral regions.

Symptoms and Types

Symptoms and types of hydronephrosis in dogs vary, with some exhibiting no apparent signs while others may experience one or several of the following:

  • Loss of appetite (anorexia)
  • Restlessness
  • Increased thirst and urination (polydipsia and polyuria, respectively)
  • Presence of blood in the urine (hematuria)
  • Signs indicating uremia
  • Halitosis (bad breath)
  • Oral sores
  • Vomiting
  • Abdominal pain
  • Lower back pain
  • Abdominal swelling


The causes of hydronephrosis in dogs include any condition leading to ureteral obstruction such as:

  • Presence of kidney stones
  • Ureteral stenosis (narrowing of the ureters)
  • Ureteral atresia (closure of the ureters)
  • Formation of excess fibrous connective tissue (fibrosis)
  • Tumors
  • Trigonal masses
  • Prostatic diseases
  • Vaginal masses
  • Retroperitoneal abscesses, cysts, hematomas, or other masses in the anatomical space behind the abdominal cavity
  • Accidental ureteral ligation during spaying surgery
  • Complications following ectopic ureter surgery
  • Perineal hernias (abnormal displacement of pelvic and/or abdominal organs into the perineal region)
  • Secondary effects of congenital ectopic ureters


To diagnose hydronephrosis in your dog, it’s crucial to provide your veterinarian with detailed information about your dog’s health and recent activities. Following a comprehensive medical history obtained from you, your veterinarian will conduct a thorough physical examination of your dog.

Standard laboratory tests will be performed, including a blood chemical profile, a complete blood count, an electrolyte panel, and a urinalysis to rule out or confirm other potential causes of disease.

Abdominal X-rays and ultrasound examinations serve as vital diagnostic tools for identifying hydronephrosis and determining its underlying cause. Additionally, transurethral urethrocystoscopy or vaginoscopy procedures may be necessary, involving the use of a small camera to visualize the interior of the vagina or urethra, the tubes draining from the kidneys to the bladder.


Your dog will receive treatment as an inpatient and will initially be provided with supportive care, including fluids and antibiotics, while diagnostic procedures are carried out. Intravenous fluid therapy will be administered over four to six hours to correct fluid and electrolyte imbalances, followed by ongoing maintenance fluids as required. In cases where extreme polyuria (excessive urination) is observed, higher rates of fluid replacement will be necessary to compensate for urinary losses.

Immediate relief of lower urinary tract obstruction through catheterization will be prioritized, along with serial cystocentesis. Surgical intervention, such as cystostomy to create an opening in the urinary bladder through the abdomen using a tube-like structure, will be performed to address any obstructions promptly.

Your veterinarian will discuss the potential presence and implications of renal disease and the need for surgery if diagnosed. Treatment, typically surgical, will depend on the underlying cause of the disease and whether concurrent renal failure or other conditions are involved, such as metastatic cancer. Emergency surgery is rarely needed for renal disease, and kidney removal is generally not considered unless it is infected or cancerous. In cases where mild disease is secondary to kidney stones, extracorporeal shock wave lithotripsy, a procedure that uses shock waves to break up kidney stones, may be considered as an alternative to surgery.

Ureteral stents have been used experimentally in dogs, involving the surgical placement of hollow, plastic tubes between the kidney and the bladder to maintain normal urine drainage.

Living and Management

After the successful removal of the obstruction, your veterinarian will arrange follow-up appointments every two to four weeks to monitor your dog’s recovery. During these appointments, bloodwork will be conducted to ensure that blood urea nitrogen and blood creatinine levels have returned to normal. If you observe excessive urination and/or weight loss in your dog following the obstruction removal, promptly contact your veterinarian for further evaluation.

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