56: 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 defined as ≥5 red blood cells per high power field (HPF) on a centrifuged urine sample. Some authors recommend that 2 of 3 urinalyses show microhematuria before an evaluation is undertaken. Hematuria is rare in newborns.

II. IMMEDIATE QUESTIONS

1. Does the infant have normal urine output? Low urine output should raise concern for obstruction of the urinary tract. Beyond the first 24 hours of life, urine output should be 1–2 mL/kg/h. Spontaneous voiding may not occur until after 24 hours of life. If the newborn is not symptomatic and does not have a distended bladder, continuing observation for the wet diaper is appropriate.

2. Were prenatal ultrasounds normal? Abnormalities including hydronephrosis, renal/abdominal masses, and renal cystic changes may lead to hematuria.

3. Has there been any instrumentation to the urinary tract? Traumatic catheterization, bladder aspiration, or instrumentation of the urinary tract may lead to hematuria that is usually transient.

4. Was there a maternal history of diabetes? Maternal diabetes should raise suspicion of renal vein thrombosis.

5. Has vitamin K been given? Consider hemorrhagic diseases of the newborn.

6. Is there an umbilical artery catheter? Presence of a catheter with hematuria should raise question of possible aortic or renal artery thrombosis.

III. DIFFERENTIAL DIAGNOSIS

Hematuria is not common in newborns, and most normal newborns do not have hematuria. Transient hematuria is common in critically ill infants. The most common cause is acute tubular necrosis (see Chapter 123).

1. Rule out causes that are not hematuria. A red-stained diaper usually signifies hematuria but may be due to bile pigments, porphyrins, or urate crystals. Rule out extraurinary sources of bleeding: vaginal bleeding (pseudomenses), rectal bleeding, post circumcision, or a severe diaper rash with excoriation. In myoglobinuria or hemoglobinuria, the urine looks red and the dipstick is positive for blood, but there are no red blood cells on microscopic examination.

2. Causes of hematuria

   1. Trauma. Birth or iatrogenic, such as bladder aspiration or catheterization, nephrostomy tubes. Transient hematuria in asphyxiated newborns.

   2. Vascular. Renal vein or artery thrombosis, hyperosmolar infusions into umbilical catheters, umbilical arterial catheters with or without thrombus. Consider renal venous thrombosis in an infant of diabetic mother (IDM), cyanotic congenital heart disease, or infants with an umbilical venous catheter.

   3. Renal. Renal cortical or medullary necrosis, acute tubular necrosis, neonatal glomerulonephritis (most commonly caused by syphilis), interstitial nephritis (medications), autosomal recessive polycystic kidney disease, multicystic renal dysplasia, congenital nephrotic syndrome.

   4. Urologic. Any cause of obstruction or anatomic anomaly: posterior urethral valves, ureteropelvic junction obstruction, reflux, ureterocele, etc. Obstruction, nephrocalcinosis, urolithiasis (after chronic Lasix administration).

   5. Infection. Inflammation will lead to hematuria. Urinary tract infection.

   6. Neoplasms. Uncommon in newborns: rhabdomyosarcoma, Wilms tumor, neuroblastoma, nephroblastoma, angiomas, congenital mesoblastic nephroma.

   7. Hematologic. Coagulopathy, hemorrhagic disease of the newborn, disseminated ...