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Hydronephrosis in Cats

In most cats, 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).

The disease 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. 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. This condition is relatively uncommon in cats.

Symptoms and Types

• May be without overt symptoms
• Anorexia (lack of appetite)
• Restlessness
• Polydipsia and polyuria (excessive thirst and excessive urination)
• Hematuria (blood in urine)
• Signs of uremia
• Very foul breath
• Mouth sores
• Vomiting
• Abdominal pain
• Lower back pain
• Abdominal distention

Causes

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

Diagnosis

Your veterinarian will perform a complete physical exam on your cat after taking a thorough medical history from you. You will need to give your veterinarian as much information on your cat's health and recent activities as you can. 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).