Fundamentals

1. Hematuria: Hematuria is blood in the urine. It may be macroscopic (visible to the naked eye) or microscopic (visible under a microscope). Sometimes urine may look red even without hematuria e.g. eating beets, free hemoglobin or myoglobin, porphyrins, phenazopyridine. Urine dipstick test will be positive in hematuria as well as in the presence of free hemoglobin and myoglobin. Hematuria can definitely be confirmed only by microscopy. Causes of true hematuria include renal calculi, polycystic kidney disease, Alport’s syndrome, sickle cell anemia, analgesic nephropathy, diabetes mellitus, glomerular and tubulointerstitial disorders like glomerulonephritis, interstitial nephritis, trauma, tumors of the urinary tract, hemorrhagic cystitis and coagulopathy.

Pointers to the differential diagnosis of hematuria

• RBC casts - renal parenchymal origin
• Dysuria, urgency, frequency - UTIs
• Renal colic - renal stones
• Recent sore throat or skin infections, hypertension, periorbital puffiness - Streptococcal glomerulonephritis
• New heart murmur, recent dental procedure - endocarditis
• Travel or previous residence in Africa, Middle-East, Southeast Asia, China, Indonesia - Schistosomiasis
• Inherited, deafness - Alport’s syndrome
• Renal cysts, berry aneurysms - ADPKD
• Analgesics, DM - Papillary necrosis
• Hemorrhagic cystitis - Cyclophosphamide
• Acute interstitial nephritis - Penicillins, cephalosporins, sulphonamides, indomethacin, allopurinol, naproxen, thiazides, cimetidine
• Bleeding tendencies - Acquired or inherited coagulopathies
• Weight loss, smoking history, industrial dye exposure, polycythemia - malignancies of the urinary system

2. Proteinuria: Under physiological conditions, < 150 mg of albumin is excreted in the urine in 24 hours. Urine dipstick specifically detects albumin in urine. Alternatively, sulfosalicylic acid precipitation test can be done to detect proteins in urine including albumin, globulins and Bence-Jones proteins. Bence-Jones proteins precipitate at 56°C and redissolve as the temperature is raised to the boiling point. Proteinuria may be glomerular due to an increase in glomerular permeability or tubular due to impaired reabsorption in the renal tubules. Tamm Horsfall protein is specific to the ascending limb of the loop of Henle and is seen in tubular injury and sometimes in multiple myeloma. Postural proteinuria may be seen in young adults in ambulatory settings but proteinuria disappears in recumbent position. Functional proteinuria occurs transiently during episodes of fever or after strenuous exercise, is not accompanied by renal pathology and does not exceed 500 mg/24 hours.

   Causes of proteinuria

   • Glomerulonephritis, tubulointerstitial diseases, diabetic nephropathy, SLE, amyloidosis, vasculitis, CCF, renal vein thrombosis, constrictive pericarditis, heavy metals, drugs and allergens
   • Monoclonal proteinuria with light chains is seen in multiple myeloma (Ig G, A,D,E and free light chains), Waldenstrom’s macroglobulinemia (IgM), heavy chain disease, lymphomas, amyloidosis

3. Oliguria, anuria and polyuria: The normal urine output per day is about 1-2 litres. Oliguria is defined as a urine output that is less than 400 mL/24 hours or less than 17 mL/hour in adults. Anuria is defined as urine output that is less than 100 mL/24 hours or 0 mL/12 hour. Polyuria is urine output > 3000 ml/24 hours.