Hematuria: A Merck Manual of Patient Symptoms podcast
Hematuria is RBCs in urine, specifically > 3 RBCs per high-power field on urine sediment examination. Urine may be red, bloody, or cola-colored (gross hematuria) or not visibly discolored (microscopic hematuria). Isolated hematuria is urinary RBCs without other urine abnormalities (eg, proteinuria, casts).
Red urine is not always due to RBCs. Red or reddish brown discoloration may result from the following:
RBCs may enter urine from anywhere along the urinary tract—from the kidneys, collecting system and ureters, prostate, bladder, and urethra.
Most cases involve transient microscopic hematuria that is self-limited and idiopathic. Transient microscopic hematuria is particularly common in children, present in up to 5% of their urine samples. There are numerous specific causes (see Some Common Specific Causes of Hematuria).
The most common specific causes differ somewhat by age, but overall the most common are
Vigorous exercise may cause transient hematuria. Cancer and prostate disease are a concern mainly in patients > 50, although younger patients with risk factors may develop cancer.
Glomerular disorders can be a cause at all ages. Glomerular disorders may represent a primary renal disorder (acquired or hereditary) or be secondary to many causes, including infections (eg, group A β-hemolytic streptococcal infection), connective tissue disorders (eg, SLE at all ages, immunoglobulin A–associated vasculitis [Henoch-Schönlein purpura] in children), and blood disorders (eg, mixed cryoglobulinemia, serum sickness). Worldwide, IgA nephropathy is the most common form of glomerulonephritis.
Schistosoma haematobium, a parasitic fluke that causes significant disease in Africa (and, to a lesser extent, in India and parts of the Middle East), can invade the urinary tract, causing hematuria. Schistosomiasis is considered only if people have spent time in endemic areas. Mycobacterium tuberculosis may also infect the lower or upper urinary tract and cause hematuria, occasionally causing urethral strictures.
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History of present illness includes duration of hematuria and any previous episodes. Urinary obstructive symptoms (eg, incomplete emptying, nocturia, difficulty starting or stopping) and irritative symptoms (eg, irritation, urgency, frequency, dysuria) should be noted. Patients should be asked about the presence of pain and its location and severity and whether they have vigorously exercised.
Review of systems should seek symptoms of possible causes, including joint pain and rashes (connective tissue disorder). Presence of fever, night sweats, or weight loss should also be noted.
Past medical history should include questions about any recent infections, particularly a sore throat that may indicate a group A ß-hemolytic streptococcal infection. Conditions known to cause urinary tract bleeding (particularly kidney calculi, sickle cell disease or trait, and glomerular disorders) should be sought. Also, conditions that predispose to a glomerular disorder, such as a connective tissue disorder (particularly SLE and RA), endocarditis, shunt infections, and abdominal abscesses, should be identified. Risk factors for GU cancer should be identified, including smoking (the most significant), drugs (eg, cyclophosphamide, phenacetin), and exposure to industrial chemicals (eg, nitrates, nitrilotriacetate, nitrites, trichloroethylene).
Family history should identify relatives with known polycystic kidney disease, a glomerular disorder, or GU cancer. Patients should be asked about travel to areas where schistosomiasis is endemic, and TB risk factors should be assessed. Drug history should note use of anticoagulants, antiplatelet drugs (although controlled anticoagulation itself does not cause hematuria), and heavy analgesic use.
Vital signs should be reviewed for fever and hypertension.
The heart should be auscultated for murmurs (suggesting endocarditis).
The abdomen should be palpated for masses; flanks should be percussed for tenderness over the kidneys. In men, a digital rectal examination should be done to check for prostate enlargement, nodules, and tenderness.
The face and extremities should be inspected for edema (suggesting a glomerular disorder), and the skin should be inspected for rashes (suggesting vasculitis, SLE, or immunoglobulin A–associated vasculitis).
The following findings are of particular concern:
Interpretation of findings:
Clinical manifestations of the various causes overlap significantly, so urine and often blood tests are required. Depending on results, imaging tests may then be needed. However, some clinical findings provide helpful clues (see Some Common Specific Causes of Hematuria).
On the other hand, some common findings (eg, prostate enlargement, excessive anticoagulation), although potential causes of hematuria, should not be assumed to be the cause without further evaluation.
Before testing proceeds, true hematuria should be distinguished from red urine by urinalysis. In women with vaginal bleeding, the specimen should be obtained by straight catheterization to avoid contamination by a nonurinary source of blood. Red urine without RBCs suggests myoglobinuria or hemoglobinuria, porphyria, or ingestion of certain drugs or foods. Generally, the presence of hematuria should be confirmed by testing a 2nd specimen.
Presence of casts, protein, or dysmorphic RBCs (unusually shaped, with spicules, folding, and blebs) indicates a glomerular disorder. WBCs or bacteria suggest an infectious etiology. However, because urinalysis shows predominantly RBCs in some patients with cystitis, urine culture is usually done. A positive culture result warrants treatment with antibiotics. If hematuria resolves after treatment and no other symptoms are present, no further evaluation is required for patients < 50, especially women.
If patients < 50 (including children) have only microscopic hematuria and no urine findings suggesting a glomerular disorder, no clinical manifestations suggesting a cause, and no risk factors for cancer, they can be observed, with urinalysis repeated every 6 to 12 mo. If hematuria is persistent, ultrasonography or CT with contrast is suggested.
Patients < 50 with gross hematuria or unexplained systemic symptoms require ultrasonography or CT of the abdomen and pelvis.
If urine or clinical findings suggest a glomerular disorder, renal function is evaluated by measuring BUN, serum creatinine, and electrolytes; doing a urinalysis; and periodically determining the urine protein/creatinine ratio. Further evaluation of a glomerular disorder may require serologic tests, kidney biopsy, or both.
All patients ≥ 50 yr require cystoscopy, as do patients who are < 50 but have risk factors, such as a family history of cancer, or systemic symptoms. Men ≥ 50 require testing for prostate-specific antigen; those with elevated levels require further evaluation for prostate cancer.
Treatment is directed at the cause.
Last full review/revision July 2013 by Anuja P. Shah, MD
Content last modified November 2013