ABSTRACT
ARF typically presents with oliguria/anuria, but is occasionally diagnosed in the presence of a normal urine output. Plasma components that depend on clearance by the kidney accumulate. Of these, creatinine is the most practical indicator. Note that the accumulation of creatinine takes time, and therefore the plasma concentration underestimates rapidly worsening kidney function. It is useful to consider the diagnosis under the following three headings.
Pre-renal; hypovolaemia.Hypovolaemia causes a physiological oligo/anuria, which is reversed when hydration is re-established. The oliguric response is accentuated if there is coexisting sepsis, recent surgery or the use of nephrotoxic drugs.
Renal parenchymal disorders. These may be:
vascular (e.g. haemolytic uraemic syndrome, renal venous thrombosis, malignant hypertension);
glomerular (e.g. severe glomerular nephritis);
renal tubular (e.g. hypoxia/ischaemia, toxic);
Drug-induced (e.g. non-steroidal anti-inflammatory agents, aminoglycosides).
Post-renal; obstruction.Obstruction may occur at a tubular level (e.g. in the tumour lysis syndrome) or at any level of the urinary tract itself (e.g. pelvi-ureteric junction obstruction in a single kidney, calculus, bladder outflow obstruction).
