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Hematuria is a frequent abnormal finding in the genitourinary system, second only to urinary tract infection. The prevalence of microscopic hematuria among school-aged children is 0.4-2.1%; however, the presence of hematuria alone is rarely indicative of serious illness bloody urine.
Pathophysiology of Hematuria
Blood in the urine is usually first detected with a dipstick test, which reacts with hemoglobin. A reaction greater than 1+ is considered positive hemateria The dipstick is not a test for red blood cells (RBCs); therefore, the dipstick screen must be followed by microscopic examination of the urine to confirm the presence of RBCs (hematuria).
Microscopic hematuria is defined as six or more RBCs per high-power field in a fresh, urine sediment specimen.
Two significant causes of a positive dipstick and a negative microscopic examination are free hemoglobin from hemolysis and myoglobinuria from rhabdomyolysis. Certain drugs and toxins also can cause red urine.
| Causes of Factitious Hematuria |
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Heme-positive
Hemoglobinuria Myoglobinuria |
|
Heme-negative
Metabolites Homogentisic acid Porphyrin Melanin Drugs Salicylates Sulfa Chloroquine Nitrofurantoin Methyldopa Metronidazole bloody urine Levodopa |
Clinical Evaluation of Hematuria
The history often will suggest a presumptive diagnosis and will usually narrow the differential diagnosis. Persistent microscopic hematuria and recurrent episodes of gross hematuria associated with viral illnesses suggests IgA nephropathy.
Dysuria, back pain or flank pain suggests urinary tract infection, hypercalciuria, or nephrolithiasis.
Hematuria from a glomerular lesion may cause the urine to appear to be brown, green, or tea-colored.
Associated Symptoms
Upper respiratory tract infection suggests IgA nephropathy.
Sore throat or an impetiginous lesion, preceding hematuria by 7-21 days, suggests poststreptococcal glomerulonephritis.
Abdominal pain may suggest a urinary tract infection or Henoch-Schönlein purpura (HSP)
Petechial or purpuric rashes of the lower extremity may suggest HSP. A malar rash suggests