Microscopy

Careful urine microscopy is essential; red cell casts in the urine may indicate bleeding from the kidney most often due to the glomerulonephritides. Red cell casts are always abnormal. White cell casts may be seen in pyelonephritis. Hyaline casts are precipitated protein; these can be seen after exercise, but granular casts are a sign of pathological proteinuria of tubular and glomerular disease.

Significant proteinuria is rare without UTI. It is indicative of a kidney cause, such as tubulointerstitial, renovascular or systemic disease. Urine sticks can detect as little as 100 mg/L proteinuria. The predominant protein detected is albumin.

Urine dipsticks are insensitive at detecting globulins and Bence Jones protein in myeloma. 24 h collection is indicated if urine is positive for protein. Selective determination of protein type can be performed using electrophoresis e.g. albumin, immunoglobulins.

Microalbuminuria is an early indication of diabetic renal disease. Proteinuria may be associated with postural changes, exercise and can occur in patients with a pyrexia.

Urine cytology is reliable only for high grade transitional tumours and is less sensitive for detecting low grade transitional cell tumours.