How to Differentiate Glomerular Hematuria from Non-glomerular Hematuria
May 31, 2022
Source: Cainiu Health
Dr. Li Mingchuan
Introduction
It is critically important to distinguish glomerular from non-glomerular hematuria, which can be assessed from the following aspects:
First, glomerular hematuria is invariably total (i.e., present throughout the entire urinary stream), whereas non-glomerular hematuria may manifest as initial hematuria, terminal hematuria, or total hematuria.
Second, most patients with glomerular hematuria do not have clots in their urine; clots occur only in specific conditions such as IgA nephropathy, Henoch–Schönlein purpura nephritis, and small-vessel vasculitis.
The clinical manifestations of glomerular hematuria and non-glomerular hematuria are very similar. So, how can we differentiate between glomerular and non-glomerular hematuria?
How to Differentiate Glomerular from Non-Glomerular Hematuria
Hematuria refers to an abnormal increase in red blood cell excretion in the urine. To diagnose hematuria, collect 10 mL of fresh early-morning urine, centrifuge it, and examine the sediment under high-power microscopy: the presence of more than three red blood cells per high-power field (HPF) confirms hematuria. Distinguishing whether hematuria originates from the glomerulus or from non-glomerular sources is critically important and can be approached from several perspectives: First, glomerular hematuria is invariably “total hematuria” (i.e., blood present throughout the entire urinary stream), whereas non-glomerular hematuria may manifest as initial hematuria (blood only at the beginning of urination), terminal hematuria (blood only at the end), or total hematuria. Second, most patients with glomerular hematuria do not pass visible blood clots; clots occur only in specific conditions such as IgA nephropathy, Henoch–Schönlein purpura nephritis, or small-vessel vasculitis. In contrast, blood clots are relatively common in non-glomerular hematuria. Third, glomerular hematuria is frequently accompanied by proteinuria and edema, whereas non-glomerular hematuria typically occurs without these associated features.
Fourth, the detection of red blood cell casts in the urine almost definitively indicates glomerular hematuria. Fifth, phase-contrast microscopy of urinary red blood cells reveals that glomerular hematuria is predominantly characterized by dysmorphic (abnormally shaped) red blood cells, whereas non-glomerular hematuria typically shows predominantly normomorphic (normal-shaped) red blood cells. Definitive diagnosis generally requires renal biopsy.
The presence of red blood cell casts in the urinary sediment strongly suggests glomerular origin of the hematuria. Phase-contrast microscopy of urinary red blood cells shows that glomerular hematuria is typically associated with dysmorphic red blood cells, while non-glomerular hematuria usually exhibits normal-appearing red blood cells. We hope this article has been helpful to you. Wishing you a happy life and good health!
