Hematuria is defined as an increased number of red blood cells (RBCs) in urine, namely, >3 RBCs per high-power field (HPF) in a centrifuged urine sample. In microscopic hematuria the color of urine is unchanged. In gross hematuria the color of urine suggests the presence of blood.
Causes and PathogenesisTop
Causes of hematuria: The following classification is based on the origin of RBCs in the urinary tract:
1) Glomerular hematuria (caused by glomerular disease): All types of acute or chronic glomerulonephritis, including IgA nephropathy, anti–glomerular basement membrane disease, and immune complex glomerulonephritis; hereditary causes, such as Alport syndrome; and benign causes, such as thin basement membrane disease.
2) Nonglomerular hematuria:
a) Upper urinary tract: Nephrolithiasis, renal cysts, cancer (renal parenchyma, renal pelvis, renal calyces, ureter), hypercalciuria, hyperuricosuria, pyelonephritis, renal trauma, renal papillary necrosis, renal infarct, renal vein thrombosis, renal tuberculosis.
b) Bladder: Cystitis, cancer, polyp, trauma, bladder stones, endometriosis.
c) Urethra: Urethritis, trauma, stricture, cancer, foreign body.
d) Prostate: Cancer, benign prostatic hyperplasia, prostatitis.
3) Other: Strenuous exercise, fever, sexual intercourse, bleeding disorder, admixture of menstrual blood, unknown cause.
Nonglomerular hematuria accounts for ~90% of all cases of hematuria.
The color of urine suggestive of hematuria may be due to the presence of pigments contained in foods (beetroot, rhubarb, certain mushrooms (Lactarius deliciosus or “saffron milk cap”), synthetic food dyes, or medications (senna, rifampin [INN rifampicin], phenolphthalein).
A positive urine dipstick result for the presence of blood should always be confirmed by microscopic examination (positive result may be due to the presence of hemoglobin or myoglobin). Take a medical history and perform a physical examination with initial diagnostic studies (urinalysis including microscopic examination of the urine sediment; complete blood count; serum levels of creatinine, sodium, potassium, and calcium; coagulation parameters if bleeding disorder is suspected). The scope of diagnostic evaluation and the sequence of tests are determined by the most likely causes of hematuria based on the patient’s history, examination, and results of diagnostic studies above:
1) Nonglomerular causes are more likely in the case of gross hematuria.
2) Glomerular causes are suggested by the presence of proteinuria (>0.5 g/24 h) and RBC casts. The presence of dysmorphic RBCs in urine sediment detected using phase-contrast microscopy strongly suggests glomerular hematuria (although this test is not readily available in many centers). Nephritic syndrome is a syndrome comprising signs of nephritis or inflammation within the glomeruli. Glomerular hematuria (or active urine sediment), proteinuria, elevated creatinine, and hypertension may be present. The diagnostic workup for nephritic syndrome would entail sending bloodwork for complements, antinuclear antibodies, extractable nuclear antigens, rheumatoid factor, cytoplasmic antineutrophil cytoplasmic antibodies, perinuclear antineutrophil cytoplasmic antibodies, anti–glomerular basement membrane antibodies, quantitative immunoglobulins, antistreptolysin O titers, hepatitis B and C serology, cryoglobulins, and HIV in at-risk individuals. Renal biopsy may be considered if clinically indicated after consultation with a nephrologist. In patients with microscopic or gross hematuria without other features strongly suggestive of glomerular etiology, a complete diagnostic workup should be performed, including imaging studies of the kidneys (ultrasonography or high-resolution computed tomography [HRCT]), upper urinary tract (intravenous urography or HRCT urography), cystoscopy, and cytologic examination of urine. In women gynecologic examination should be also considered. In patients receiving anticoagulation treatment, persistent hematuria requires a diagnostic evaluation.
No further evaluation is usually necessary if hematuria has occurred:
1) In a young woman with typical clinical features of cystitis, confirmed urinary tract infection (significant bacteriuria), and hematuria resolving after antibiotic treatment.
2) In the case of strenuous exercise, fever, menstruation, or potential urinary tract injury (eg, sexual intercourse) if follow-up urinalysis obtained >48 hours after resolution of the potential precipitant reveals no hematuria.