Does the Urine Dipstick Detect Blood Reliably?

Urine dipsticks are sensitive and will detect even small numbers of red blood cells (RBCs), especially if the specimen is concentrated. Blood is often identified by dipstick on a routine urinalysis for a totally asymptomatic child. When the dipstick test is “trace,” it reflects < 5 RBCs per high-power field on microscopic examination and is physiologic. Occasionally, the presence of substances other than RBCs, such as hemoglobin and myoglobin, can also cause discoloration of the urine dipstick.

How Is Hematuria Defined?

Microscopic hematuria is defined as more than 5 RBCs per high-power field on a centrifuged urine specimen, and is found on one occasion in as many as 4% of all urine specimens in American school children. It is generally benign when present without proteinuria. When the dipstick reading is “moderate” or “large,” and especially when associated with proteinuria, the hematuria may reflect underlying renal disease. Persistent microscopic hematuria occurs in fewer than 1% of children. Gross hematuria means that urine contains visible blood and occurs in < 0.1% of children.

What Causes Hematuria?

A list of the common causes of hematuria is found in Table 52-1.

Table 52-1 Causes of Hematuria in Children

How Do I Evaluate Isolated Microscopic Hematuria?

An otherwise healthy child with isolated microscopic hematuria needs only a repeat urine specimen while you review the child’s growth, development, and blood pressure. The urine should be sent for urinalysis with microscopic evaluation for RBCs. Isolated microscopic hematuria will resolve spontaneously in most cases and no further workup is needed. Presence of white blood cells (WBCs), crystals, or casts would suggest a diagnosis other than isolated microscopic hematuria.

How Do I Evaluate Persistent Microscopic Hematuria?

Most patients who have asymptomatic persistent microscopic hematuria have no history of gross hematuria and have age-appropriate growth, development, blood pressure, and renal function. Proteinuria is not present on urinalysis. Such patients have, at most, mild renal disorders, which have little chance of progressing to renal failure. Treatment does not alter the management or natural history. A limited workup is appropriate for these patients, including random urine calcium-to-creatinine ratio, and screening for microscopic hematuria in family members to detect familial glomerulonephritis (Chapter 65). A complete workup, as outlined later for gross hematuria, would be necessary if the physician or family wishes to rule out all significant renal diseases or if the patient has microscopic hematuria plus other associated signs or symptoms.

How Do I Evaluate Gross Hematuria?

If your patient has visible blood in the urine a complete workup is needed. A thorough history, physical examination, and urinalysis can usually determine whether the hematuria originates in the renal parenchyma or the collecting system (Table 52-2). If the source is identified, perform the pertinent workup, as discussed later. If you cannot determine the source of hematuria with any reasonable degree of accuracy, do further testing as dictated by the patient’s condition. Referral to a nephrologist or urologist is justified.

Table 52-2 Clinical Findings in Hematuria Based on Source of Bleeding