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Causes of Kidney Failure

Some of the more serious causes of kidney failure include:

Hereditary and Congenital Abnormalities

These types of kidney disease are very frustrating to try to control or repair. Most cats with abnormally constructed kidneys will develop kidney failure and do not live anywhere near a normal life span.

A few hereditary conditions that lead to kidney failure include:

• Polycystic kidney disease (PKD), though uncommon, creates cystic areas in the kidneys where normal function and structure are lost.  Eventually, even if the cat reaches maturity, gradual increases in metabolic waste products and signs of kidney disease prevent optimum quality of life and the animal dies or is mercifully euthanized. If found, it typically occurs in Persian/Exotic cats.
• Renal agenesis, also called kidney aplasia, causes the cat to be born without one or both kidneys.
• Renal hypoplasia is a condition where the kidney(s) do not develop completely.
• Renal cortical hypoplasia is a condition where the cortex of the kidney(s) develops incompletely.
• Renal dysplasia is a condition where the kidneys develop abnormally. Renal failure develops with protein loss in urine.
• Renal tubular dysfunction occurs when the filtering tubules of the kidneys do not function properly.

Bacterial Invasion

Infections of the urinary tract of cats are, unfortunately, very common. Generally arising from gradual spread of external bacterial organisms near the external urinary orifices, the bacteria multiply and invade the urethra, then into the bladder (causing what is termed cystitis), and occasionally further retrograde up the ureters and eventually into the kidneys. 

Another less common means of kidney infection arises from a blood-borne dispersion of bacteria from a remote area such as an abscess or skin infection. Leptospirosis bacteria, for example, can have a severe effect on kidneys.

Another severe bacterial infection (Borrelia burgdorferi) may be caused by the bite of a tick. This infection causes Lyme Disease, which damages the kindey's ability to filter body waste products and transport of those waste products into the urine. Even after eliminating the bacteria with antibiotic therapy there may remain permanent structural damage to vital renal tissues -- and kidney failure ensues.

Fungal Infections

Systemic fungal infections such as Blastomycosis, Coccidioidomycosis (Valley Fever), and Histoplasmosis can attack nearly any tissue or organ in the body, including the kidneys. Most systemic fungal diseases are geographically oriented.

Trauma to Kidney

Direct trauma to the kidneys can result in kidney failure. Although rare, cats that are run over by vehicles can suffer permanent and irreparable kidney trauma. Also, sudden physical shock to the kidney tissues from being struck by vehicles, baseball bats, kicking, or falls from a height, etc. can result in suffusive bleeding into the kidney tissue and permanently impair renal function.

Blockage of Urine Flow

The most notable condition seen in cats from blockage of urine flow from the kidneys involves kidney stones or bladder stones or urethral obstructions. The obstructions caused by these mineral concretions (usually called struvite uroliths) can increase back pressure on the affected kidney, which permanently damages kidney function and causes what is termed hydronephrosis -- a kidney swollen under pressure with backed up urine. 

Cats with bladderstones often obstruct when a stone passes from the bladder but cannot be voided past the os penis -- the bone present in the male feline's penis. There is an inherent lack of room for the urethra to dilate in the area of the os penis and small bladder stones often dam up the urine flow at this site. Surgical intervention is often required in these emergency urinary tract blockage cases.

Tumors, cysts, abscesses and scar tissue, if present in critical areas of the urinary tract, can create obstructive situations where the urine flow from a kidney is compromised. This can result in damage to delicate kidney tissue structures, which is often permanent. If enough tissue is destroyed or its function impaired, kidney failure will occur.