Given the wide diversity of causes of hematuria, ranging from simple urinary tract
infections with rapid recovery to severe glomerulonephritis with fast decline in kidney
function, it is essential to recognize the underlying disease. The first objective
of the assessment is to determine whether the cause of the hematuria is medically
significant. The combination of hematuria with proteinuria, the presence of hypertension,
or worsening kidney function can represent signs of progressive kidney disease. Differentiating
the various causes of hematuria is often simple and obvious based on the clinical
signs and gross appearance of the urine. However, in some instances, additional non-invasive
investigations, such as ultrasound imaging, urinary red cell morphology, measurement
of calcium and other solutes in the urine, evaluation of kidney function, and protein
excretion, are needed to elucidate the nature of the hematuria. Taking a detailed
family history can help in establishing the underlying cause in cases of familial
hematuria. On the other hand, the decision to perform a kidney biopsy in children
with asymptomatic hematuria remains a challenging issue for clinicians. Ultimately,
the frequency of diagnosis of glomerular involvement causing hematuria may depend
on the threshold for performing a kidney biopsy. The following review will focus on
the diagnostics of hematuria, starting with difficulties regarding its definition,
followed by various means to differentiate between urinary, glomerular, and other
causes, and finally reviewing the most common diseases that, due to their frequency
or their effect on kidney function, present a diagnostic challenge in everyday practice.
