Hematuria and proteinuria: Commonplace or cause for concern?

Although pediatricians should no longer be routinely performing universal urine screenings in children, there are times that urinalysis is performed and abnormal results are found.

Beth Vogt, MD, FAAP, a specialist in pediatric kidney disease and medical director of Pediatric Hemodialysis Services, Pediatric Dialysis Services, and the Pediatric Hypertension Center in the Division of Pediatric Nephrology at University Hospitals Rainbow Babies and Children’s Hospital, Cleveland, Ohio, and assistant professor of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, led a session on the advances in the diagnosis and early management of hematuria and proteinuria in pediatrics at the American Academy of Pediatrics (AAP) 2017 National Conference and Exhibition on Saturday, September 16.

“Although universal screening of urine is no longer recommended in children, pediatricians will find abnormal urinalyses from time to time and need to know how to interpret them and know when to refer for further evaluation,” Vogt says. “Many of the findings in a urinalysis are transient and don’t represent true pathology. If the child is well and without symptoms, pediatricians need to repeat urine testing before embarking on a big evaluation.”

Vogt says she hopes her presentation clears up confusion for pediatricians in regard to both hematuria and proteinuria. “I hope my talk helps pediatricians to stop doing routine urine screenings and if they happen to find an abnormal urinalysis along the way, to know how to identify true pathology and refer appropriately,” she says.

According to Vogt’s presentation, 4% to 6% of school-aged children have microscopic hematuria on a single examination, but repeat testing reduces that incidence to 0.5% to 1%. Pediatricians who follow the AAP’s recommendation to eliminate routine urine screenings are more likely to see macroscopic hematuria in the clinical setting, she says.

Hematuria is officially diagnosed through a positive urine dipstick and more than 5 to 10 red blood cells per high power field (rbc/hpf). Dipstick testing should be confirmed on 2 separate visits, and follow-up testing may include urine calcium creatinine ratios; urine cultures if symptoms or pyuria are present; sickle cell screening; kidney/bladder ultrasounds; parental urinalysis; and possible referral to nephrology.

Microscopic hematuria is most often transient-Vogt estimates 90% of the time. For this reason, she recommends a repeat test will “weed out” the transient cases. Beyond transient cases, microscopic hematuria may be caused by hypercalciuria, hereditary nephritis, early chronic glomerulonephritis, tumors, sickle cell trait/disease, or polycystic kidney disease. In transient cases, the hematuria will often resolve and may be caused by concentrated urine, contamination with menstrual blood, dermatitis, trauma, exercise, or resolving subclinical acute glomerulonephritis. In these cases, Vogt recommends reassurance as an intervention, rather than overtesting.

Macroscopic hematuria is evaluated in the same way with the added possibility of a urology referral. It can be caused by trauma with possible underlying urinary tract abnormalities, urinary tract infections, exercise, urolithiasis, tumors, sickle cell trait/disease, or glomerulonephritis.

Vogt cautions that macroscopic hematuria has a broad differential. Clinicians have to evaluate the color of urine, which can range from brown to red, as well as the presence of proteinuria, hypertension, or renal dysfunction to narrow a differential diagnosis.

Proteinuria is similar to hematuria in several ways, Vogt says. Like hematuria, proteinuria can be transient, and this is very common. It can be caused by illness with fever, dehydration, exercise, and urinary tract infections. Orthostatic proteinuria can also occur in urine produced in an upright position, but the same patient’s urine might test negative in the supine position. This benign condition affects 2% to 5% of adolescents. It is diagnosed as less than 1 gram per 24 hours, and causes are unknown, Vogt says.

Proteinuria also can be persistent, but this is defined as 1 gram or more in a 24-hour period. Not transient, this form of proteinuria is present at all times and may indicate kidney disease, Vogt says. Some kidney diseases that proteinuria could signal include focal segmental glomerulosclerosis, membranous nephropathy, reflux nephropathy/renal scarring, renal dysplasia, and polycystic kidney disease.

Vogt recommends testing for proteinuria when children present with puffy eyes or edema because of the possibility of nephrotic syndrome.

Whereas repeated testing is recommended for confirmation of proteinuria, Vogt cautions clinicians against immediately overreacting when abnormal results are repeated on a second test.

“Proteinuria is very common. It can be transient and related to exercise, dehydration, illness, or it can be orthostatic. The key to evaluating proteinuria is to do a urinalysis on a first morning sample. If protein is present there, there may be renal pathology,” Vogt says.

In fact, Vogt says, proven hematuria or proteinuria in a first morning sample is one of the only reasons a pediatrician should refer a patient for this issue to a specialist. Otherwise, a referral may just cost parents a lot of money and anxiety.

However, for patients with both blood and protein in the urine, visible blood in the urine (macroscopic hematuria), or when 1 of these conditions is paired with high blood pressure or swelling, there is also cause for concern.

“This is a different situation and immediate evaluation is indicated,” Vogt says.

Patients with persistent hematuria and/or proteinuria should be referred to a nephrologist, she adds.