Renal insufficiency

'''For more detailed information please see the chapters on acute renal failure and chronic renal failure. This chapter is simply an overview of these more specific disease states.'''

Overview
 Renal failure or kidney failure is the condition in which the kidneys fail to function adequately.

Biochemically, it is typically detected by an elevated serum creatinine. In the science of physiology, renal failure is described as a decrease in the glomerular filtration rate.

Classification
Renal failure can broadly be divided into two categories (see flowchart below): acute renal failure and chronic renal failure.

Renal failure classification

The type of renal failure (acute vs. chronic) is determined by the trend in the serum creatinine. Other factors which may help differentiate acute and chronic renal failure include the presence of anemia and the kidney size on ultrasound. Long-standing, i.e. chronic, renal failure generally leads to anemia and small kidney size.

Acute renal failure
Acute renal failure (ARF) is, as the name implies, a rapidly progressive loss of renal function, generally characterised by oliguria (decreased urine production, quantified as less than 400 mL per day in adults, less than 0.5 mL/kg/h in children or less than 1 mL/kg/h in infants); body water and body fluids disturbances; and electrolyte derangement. An underlying cause must be identified to arrest the progress, and dialysis may be necessary to bridge the time gap required for treating these fundamental causes. ARF can result from a large number of causes.

Chronic renal failure
Chronic renal failure (CRF) can either develop slowly and show few initial symptoms, be the long term result of irreversible acute disease or be part of a disease progression. There are many causes of CRF. The most common cause is diabetes mellitus. End-stage renal failure (ESRF) is the ultimate consequence, in which case dialysis is required unless a donor for a renal transplant is found.

Acute on chronic renal failure
Acute renal failure can be present on top of chronic renal failure. This is called acute-on-chronic renal failure (AoCRF). The acute part of AoCRF may be reversible and the aim of treatment, as with ARF, is to return the patient to their baseline renal function, which is typically measured by serum creatinine. AoCRF, like ARF, can be difficult to distinguish from chronic renal failure, if the patient has not been monitored by a physician and no baseline (i.e., past) blood work is available for comparison.

Use of the term uremia
Before the advancement of modern medicine, renal failure was often referred to as uremic poisoning. Uremia was the term used to describe the contamination of the blood with urine. Starting around 1847, this term was used to describe reduced urine output, that was thought to be caused by the urine mixing with the blood instead of being voided through the urethra. The term uremia is now used to loosely describe the illness accompanying kidney failure.

Differential Diagnosis of Reversible Renal Failure
In alphabetical order.


 * Congestive Heart Failure
 * Drugs, toxin
 * Hypercalcemia
 * Hyperkalemia
 * Hypertension
 * Infection of the urinary tract
 * Obstruction
 * Volume depletion