Asymptomatic Microscopic Hematuria

The finding of red blood cells in a child’s urine is a frequent cause for referral to the pediatric urologist. Of course, when the child is symptomatic or the urine is grossly bloody there is usually a specific cause; and more extensive laboratory and radiologic evaluation is indicated.

EVALUATION

About 5% of children screened randomly to detect hematuria will manifest red cells. A single repeat examination of a fresh urine specimen is the initial step to confirm that microhematuria is present. Dipsticks are extremely sensitive but can detect clinically insignificant levels of urinary hemoglobin or myoglobin. It is also important to determine whether the erythrocytes being measured are intact or hemolyzed. In the spun urine sediment the presence of 5-10 red cells per high power field is believed to be significant.

The point of origin of red cells in the urine is variable; and the most common causes in children are due to infection, nephritis or trauma. The history may detect the presence of dysuria, urgency and frequency, which may suggest a urinary tract infection. Urologic symptoms suggestive of an obstructive voiding pattern or those of an unstable bladder may indicate a cause for the hematuria. An earlier sore throat or skin infection can suggest the presence of glomerulonephritis. A history of trauma or bleeding diathesis or a family history of stone disease may suggest the origin of the hematuria. A lack of symptoms confirms asymptomatic hematuria.

Physical exam is usually of limited value. Rashes and bruises may be informative. Abdominal examination should rule out a palpable bladder and/or other abdominal masses. The voiding stream should be observed. In a boy, the meatus is inspected to rule out inflammation or stenosis. In a girl, the perineum and introitus should be inspected to detect inflammation. A blood pressure measurement is helpful when evaluating the patient with nephritis.

Laboratory Evaluation

Essential to any evaluation of a child with microhematuria are a urinalysis and a urine microscopy. If the urinalysis reveals greater than 2+ proteinuria with red cells, red cell casts and tubular epithelial cells, it is most likely that the hematuria has a glomerular origin. Urinary red cells characterized by variation in size and shape are often associated with glomerular lesions. A urine culture is important to confirm microscopic findings of pyuria and hematuria.

If a glomerular source exists for the hematuria and proteinuria, and casts and dysmorphic cells are present, then a serum complement (C3), streptozyme and anti-nuclear antibody titers should be obtained. Serum creatinine in conjunction with a 24-hour urinary creatinine clearance and protein excretion are also important.

A determination of the fasting urinary calcium to creatinine ratio is important, as in many children hypercalciuria is an important cause of microhematuria. A fasting urine calcium to creatinine ratio is considered to be a screening test and is positive when the ratio is greater than 0.21. This fasting level defines the so-called renal leak hypercalciuria. A 24-hour urine calcium excretion is necessary for a complete evaluation.

The mechanism by which hypercalciuria produces hematuria is unknown but is probably through epithelial cell injury. The risk for future calculus formation in these children is as yet unknown but does pose a potential problem.

If the patient is black, a sickle cell screening is important to rule out sickle cell disease.

Uroradiological imaging may not be required. However, much screening and reassuring information can be obtained with a renal and pelvic sonogram. Abnormalities discovered on sonography can be further delineated with formal X-rays. Cystoscopy is infrequently indicated in the evaluation of hematuria in children.