Renal failure- initial investigations

Urea and creatinine
Serum electrophoresis - myeloma screen
Serum lactate dehydrogenase – acute elevation occurs in renal infarction

Haematology

Eosinophilia – suggests vasculitis
Raised erythrocyte sedimentation rate - suggests vasculitis
Fragmented red cells and/or thrombocytopenia – suggests intravascular haemolysis due to accelerated hypertension or haemolytic uraemic syndrome

Complement components – low in active disease due to systemic lupus erythematosus (SLE), mesangiocapillary glomerulonephritis (G-N), post-streptococcal G-N or cryoglobulinaemia
Autoantibodies – useful in SLE, scleroderma, Wegner's granulomatosis, microscopic polyarteritis, Goodpasture's syndrome
Cryoglobulins – occur in patients with unexplained glomerular disease, particularly mesangiocapillary G-N

Haematuria – may indicate G-N
Proteinuria – strongly suggestive of glomerular disease
Glycosuria – with a normal blood sugar indicates tubular disease

White cells – active bacterial urinary infection
Eosinophilia – strongly suggestive of allergic tubulo-interstitial nephritis
Granular casts – formed from abnormal cells within tubular lumen and indicates active renal disease
Red cell casts – highly suggestive of G-N

24-hour creatinine clearance – useful in measuring the severity of renal failure
Urinary electrolytes – unhelpful in renal failure
Urinary osmolarity – measure of the concentrating ability
Urine electrophoresis – necessary for the detection of light chains

Urine culture
Early morning urine – especially for tuberculosis
Antibodies to streptococcal antigens – antistreptococcal antibody titres, anti-DNAase B, especially if post-streptococcal G-N is possible
Antibodies to hepatitis B & C – polyarteritis nodosa or membranous nephropathy (hepatitis B)
Antibodies to HIV
Malaria – important cause of glomerular disease in the tropics