Chronic Renal Failure

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Overview

Chronic renal failure (CRF) is the progressive loss of kidney function. The kidneys attempt to compensate for renal damage by hyperfiltration (excessive straining of the blood) within the remaining functional nephrons (filtering units that consist of a glomerulus and corresponding tubule). Over time, hyperfiltration causes further loss of function.

Chronic loss of function causes generalized wasting (shrinking in size) and progressive scarring within all parts of the kidneys. In time, overall scarring obscures the site of the initial damage. Yet, it is not until over 70% of the normal combined function of both kidneys is lost that most patients begin to experience symptoms of kidney failure.

Types

Chronic renal failure (CRF) can be classified by the site (location) of primary damage:

• Pre-renal CRF
• Post-renal CRF (obstructive uropathy)
• Renal CRF

Causes

The cause for CRF sometimes can be determined by a detailed medical history, a comprehensive physical examination, and laboratory studies. More often than not, determining the cause of CRF is difficult if not impossible. Even a kidney biopsy may be inconclusive, because all forms of kidney failure eventually progress to diffuse scarring and look the same on kidney biopsy. The most common causes for CRF are diabetes and high blood pressure (hypertension.)

Kidney disorders, including chronic renal failure, are common in patients who have multiple myeloma (cancer that begins in a type of white blood cell called plasma cells). Several different factors are related to renal disease associated with multiple myeloma. Myeloma cells produce large numbers of proteins in the urine (called proteinuria). These proteins often form deposits in the kidneys (condition called amyloidosis) and cause kidney failure. In addition, multiple myeloma increases the risk for hypercalcemia (high levels of calcium in the blood) and anemia (low levels of red blood cells) and results in high blood levels of uric acid, which also increase the risk for chronic renal failure.

Pre-Renal CRF
Some medical conditions cause continuous hypoperfusion (low blood flow) of the kidneys, leading to kidney atrophy (shrinking), loss of nephron function, and chronic renal failure (CRF). These conditions include poor cardiac function, chronic liver failure, and atherosclerosis ("hardening") of the renal arteries. Each of these conditions can induce ischemic nephropathy.

Post-Renal CRF
Interference with the normal flow of urine can produce backpressure within the kidneys, can damage nephrons, and lead to obstructive uropathy, a disease of the urinary tract. Abnormalities that may hamper urine flow and cause post-renal CRF include the following:

• Bladder outlet obstruction due to an enlarged prostate gland or bladder stone
• Neurogenic bladder, an overdistended bladder caused by impaired communicator nerve fibers from the bladder to the spinal cord
• Kidney stones in both ureters, the tubes that pass urine from each kidney to the bladder
• Obstruction of the tubules,the end channels of the renal nephrons
• Retroperitoneal fibrosis, the formation of fiberlike tissue behind the peritoneum, the membrane that lines the abdominal cavity
• Vesicoureteral reflux (VUR), the backward flow of urine from the bladder into a ureter

Renal CRF
Chronic renal failure caused by changes within the kidneys, is called renal CRF, and is broadly categorized as follows:

• Diabetic nephropathy, kidney disease associated with diabetes; the most common cause of CRF
• Hypertension nephrosclerosis, a condition that occurs with increased frequency in African Americans; the second leading cause of CRF
• Chronic glomerular nephritis, a condition caused by diseases that affect the glomeruli and bring about progressive dysfunction
• Chronic interstitial nephritis, a condition caused by disorders that ultimately lead to progressive scarring of the interstitium
• Renal vascular CRF, large vessel abnormalities such as renal artery stenosis (narrowing of the large arteries that supply the kidneys)
• Vasculitis, inflammation of the small blood vessels
• Cystic kidney disease, kidney disease distinguished by multiple cysts (lined cavities or sacs)
• Hereditary diseases of the kidney, such as Alport's syndrome (hereditary nephritis)

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