The prevalence of gross hematuria in children is estimated to be 0.13%. In more than half of the cases (56%) this is due to an easily identifiable cause. The most common cause appears to be cystitis (20-25%). Asymptomatic microscopic hematuria is, on the average, 10-fold as prevalent as gross hematuria (1.5%, range 0.4-4.1%, depending on the criteria used to define hematuria). With repeated evaluations, the prevalence of asymptomatic microscopic hematuria decreases to less than 0.5%, supporting the notion that most cases of hematuria in children are transient. The incidence of simultaneous hematuria and proteinuria is estimated to be only 0.06%, but their coexistence signals significant renal disease.
In general, children with isolated asymptomatic microscopic hematuria tend to do well, whereas those with associated findings (eg, hypertension, proteinuria, abnormal serum creatinine levels) are more likely to have serious problems. Because hematuria is the end result of various processes, the morbidity and mortality rates of the condition depend on the primary process that initiated it.
The incidence of hematuria in specific racial groups is determined by the primary cause. For example, idiopathic hypercalciuria is infrequent in black and Asian children, but relatively common in whites. Conversely, hematuria caused by sickle cell disease is more common in blacks than in whites.
Sex may predispose a child to specific diseases that manifest as hematuria. For example, the sex-linked form of Alport syndrome has a male preponderance, whereas lupus nephritis is more common in adolescent girls.
Prevalence of certain conditions varies with age. For instance, Wilms tumors are more frequent in children of preschool age, whereas acute postinfectious glomerulonephritis is more frequent in the school-aged population. In adults, hematuria is often a sign of malignancy of the genitourinary tract (eg, renal cell carcinoma, bladder tumors, prostatic tumors). These conditions are rare in children.
The first step in the evaluation of hematuria is a detailed review of the history and a thorough physical examination. An attempt should be made to distinguish glomerular causes of hematuria from extraglomerular ones, as this helps in prioritizing the investigations.
· A history of passage of clots in urine suggests an extraglomerular cause of hematuria.
· A history of fever, abdominal pain, dysuria, frequency, and recent enuresis in older children may point to a urinary tract infection as the cause of hematuria.
· A history of recent trauma to the abdomen may be indicative of hydronephrosis.
· A history of early-morning periorbital puffiness, weight gain, oliguria, the presence of dark-colored urine, and the presence of edema or hypertension suggests a glomerular cause.
· Hematuria due to glomerular causes is painless.
· A history of a recent throat or skin infection may suggest postinfectious glomerulonephritis.
· A history of joint pains, skin rashes, and prolonged fever in adolescents suggests a collagen vascular disorder.
· The presence of anemia cannot be accounted for by hematuria alone, and, in a patient with hematuria and pallor, other conditions such as systemic lupus erythematosus and bleeding diathesis should be considered.
· Information regarding exercise, menstruation, recent bladder catheterization, intake of certain drugs or toxic substances, or passage of a calculus may also assist in the differential diagnoses.
· Because certain diseases that present with hematuria are inherited or familial, asking for a family history that is suggestive of Alport syndrome, collagen vascular diseases, urolithiasis, or polycystic kidney disease is important.
In the general physical examination, the most important step is to measure the blood pressure (with an appropriate-sized cuff) and evaluate for the presence of periorbital puffiness or peripheral edema.
· A detailed skin examination is necessary to look for purpura.
· An abdominal examination is indicated to look for palpable kidneys (Wilms tumor or hydronephrotic kidneys).
· A careful examination of the genitalia is also important.