Chapter 61: Hematuria

I. PROBLEM

A nurse reports that an infant has a red-stained diaper and states the infant may have hematuria. Hematuria is the presence of gross or microscopic blood in the urine. It is more common in premature infants in the neonatal intensive care unit than in healthy newborns. Studies on incidence are lacking, but one older retrospective study reporting gross hematuria in 0.21 per 1000 admitted infants <1 month old. The differential diagnosis in neonates is different than in older children. Gross hematuria requires an immediate evaluation, whereas microscopic hematuria is usually transient and benign in the neonate.

II. IMMEDIATE QUESTIONS

1. Does the infant really have hematuria? A red-stained diaper usually signifies hematuria but may be due to pseudohematuria (red-colored urine in the absence of red cells or hemoglobin) or blood from a nonurinary source that is mistaken for gross hematuria in the diaper or myoglobinuria or hemoglobinuria. First it needs to be decided whether the urine dipstick is positive or negative for blood. If urine is negative for blood then it is pseudohematuria. If it positive for blood microscopic urinalysis needs to be done to confirm RBCs are from the urine.

   1. Negative dipstick for blood

      1. Urate crystals can present as pinkish to reddish brown discoloration in the diaper. It is more commonly seen in volume depletion, especially in breast-fed neonates. This is a benign condition, and treatment is increased fluid intake.

      2. Congenital erythropoietic porphyria (Gunther disease) is a rare autosomal recessive disease due to deficiency of the uroporphyrinogen III cosynthetase enzyme, which results in an accumulation of type I porphyrins. It can present as pink to brown staining of the diaper because of porphyrin pigment in the urine. Red fluorescence of urine on a diaper under a Wood’s light (ultraviolet) indicates porphyria (normal urine shows greenish blue/yellow).

      3. Medications that cause urine to look red or pink include rifampin, phenytoin, methyldopa, chloroquine, nitrofurantoin, senna, heparin, salicylates, ibuprofen, phenothiazines, phenylbutazone, daunorubicin, and doxorubicin.

   2. Positive dipstick for blood

      1. Nonurinary sources of bleeding that can be mistaken for gross hematuria in the diaper.

         1. Vaginal bleeding (pseudomenses) from maternal hormonal withdrawal.

         2. Rectal or other gastrointestinal bleeding

         3. Postcircumcision bleeding

         4. Severe diaper rash with excoriation

      2. Myoglobinuria and hemoglobinuria. In myoglobinuria (seen in severe perinatal asphyxia) or hemoglobinuria (seen with ABO incompatibility with intravascular hemolysis), the urine looks red and the dipstick is positive for blood, but there are no red blood cells on microscopic examination.

      3. Urinary source of bleeding. See causes below.

2. What is the degree of hematuria? Hematuria is classified as gross hematuria (urine that is visibly discolored (seen by naked eye) by blood that can be red or brown colored or frank blood) or microscopic hematuria (defined as ≥5 red blood cells per high-power field on a spun urine sample). Gross hematuria requires immediate evaluation. Microscopic hematuria is more common in premature infants and increases with a lower birth weight and gestation. If present in a ...