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Hydronephrosis This develops secondary to complete or partial obstruction of urinary flow, the resulting back pressure on the kidney causes a dilatation of the renal pelvis and destruction of the functional kidney tissue. The obstructions can be congenital deformations of the urinary tract, or they can develop secondary to imflammation, tumours or calculi (kidney/bladder stones). Unless the obstruction is removed or relieved then tissue damage becomes irreversible. If only one kidney is affected then renal failure will not develop as long as the other kidney is functioning properly, if both kidneys are involved then uraemia and acute renal failure will develop. The back pressure causes kidney swelling, if this is a gradual process affecting one kidney then it can become transformed into a large fluid filled sac, if it is an sudden process then the condition becomes painful due to the stretching of the renal capsule. Any part of the urinary tract which contains static collections of fluid is prone to developing an infection (pyonephrosis). Enlarged kidneys may be palpable, if not then X-rays or ultrasounds scans will reveal the problem. The clinical signs will involve pain in the affected kidney, some blood may be passed in the urine. If the obstruction is at the level of the bladder or urethra then the animal will be unable to pass urine. Uraemia will develop, secondary infection is common which can lead to fever and lethargy. Blood tests will show increased urea and creatinine levels if both kidneys are affected. The only available treatment is to relieve the obstruction, usually surgically. Antibiotics are necessary to control secondary infection. Once changes have developed in the kidney tissues then the change is irreversible. If one kidney has been severely affected and the opposite kidney is normal then removal of the affected kidney may be advisable. If renal failure has started to develop then conservative management and symptomatic treatment should be instituted. The prognosis is good if only one kidney is affected and the cause is non-neoplastic. Bilateral involvement has a guarded prognosis. |
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