American Board of Internal Medicine (ABIM) Certification Practice Exam

What is a key characteristic of glomerular hematuria when urine is examined?

1. Presence of isomorphic erythrocytes

2. Brown- or tea-colored urine

3. No proteinuria

4. Clear urine with no casts

The correct answer is: Brown- or tea-colored urine

A key characteristic of glomerular hematuria is the urine appearing brown or tea-colored. This coloration is due to the presence of free hemoglobin and red blood cell casts that result from the breakdown of red blood cells within the glomeruli or along the nephron. In cases of glomerular disease, the integrity of the glomerular filtration barrier is compromised, leading to the passage of red blood cells into the urine, which can contribute to this distinctive coloration. While the presence of isomorphic erythrocytes can also be a characteristic of glomerular hematuria, the specific color of the urine is a more prominent feature that distinguishes it from other types of hematuria, such as that from the urinary tract, which may present differently. Additionally, proteinuria is commonly associated with glomerular damage, so it's incorrect to describe glomerular hematuria as having no proteinuria. Finally, clear urine with no casts would suggest a more benign source of hematuria or another condition entirely, not indicative of glomerular involvement.