- Hematuria: Hematuria means blood in the urine. It may be:
- Macroscopic (gross): visible to the naked eye
- Microscopic: seen only under a microscope
Sometimes urine looks red even when there’s no true hematuria. Examples include eating beets, free hemoglobin or myoglobin, porphyrins, and phenazopyridine.
A urine dipstick test will be positive in hematuria, and it will also be positive when free hemoglobin or myoglobin is present. Because of this, hematuria can be confirmed definitively 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 and 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
- Proteinuria: Under physiological conditions, < 150 mg of albumin is excreted in the urine in 24 hours. A urine dipstick specifically detects albumin in urine.
Alternatively, the sulfosalicylic acid precipitation test can be used 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 increased glomerular permeability
- 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 the proteinuria disappears in the recumbent position.
Functional proteinuria occurs transiently during episodes of fever or after strenuous exercise. It 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
- Oliguria, anuria and polyuria: Normal urine output per day is about 1-2 litres.
- Oliguria is defined as urine output < 400 mL/24 hours or < 17 mL/hour in adults.
- Anuria is defined as urine output < 100 mL/24 hours or 0 mL/12 hour.
- Polyuria is urine output > 3000 ml/24 hours.
