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Chronic Renal Failure
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(s) of 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.

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:

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