Acute renal failure

Published on 01/03/2015 by admin

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Last modified 01/03/2015

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Acute renal failure

Renal failure is the cessation of kidney function. In acute renal failure (ARF), the kidneys fail over a period of hours or days. Chronic renal failure (CRF) develops over months or years and leads eventually to end-stage renal failure (ESRF). ARF may be reversed and normal renal function regained, whereas CRF is irreversible.

Aetiology

ARF arises from a variety of problems affecting the kidneys and/or their circulation. It usually presents as a sudden deterioration of renal function indicated by rapidly rising serum urea and creatinine concentrations. As acute renal failure is common in the severely ill, sequential monitoring of kidney function is important for early detection in this group of patients.

Usually, urine output falls to less than 400 mL/24 hours, and the patient is said to be oliguric. The patient may pass no urine at all, and be anuric. Occasionally urine flow remains high when tubular dysfunction predominates.

Kidney failure or uraemia can be classified as (Fig 18.1):

Diagnosis

In nearly all cases the clinical history and presentation will indicate that a patient has, or may develop, ARF. The first step in assessing the patient with ARF is to identify any pre- or post-renal factors that could be readily corrected and allow recovery of renal function. The history and examination of the patient, including the presence of other severe illness, drug history and time course of the onset of the ARF, may well provide important clues. Factors that precipitate pre-renal uraemia are usually associated with a reduced effective ECF volume and include:

Pre-renal factors lead to decreased renal perfusion and reduction in GFR. Both AVP and aldosterone are secreted maximally and a small volume of concentrated urine is produced.

Biochemical findings in pre-renal uraemia include the following:

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