American Board of Internal Medicine (ABIM) Certification Practice Exam

Which of the following is a common finding in glomerular hematuria?

1. Dysmorphic erythrocytes

2. Low urine osmolality

3. Presence of bacteria

4. Immunoglobulin abnormalities

The correct answer is: Dysmorphic erythrocytes

Dysmorphic erythrocytes are a hallmark finding in glomerular hematuria due to the pathological changes that red blood cells undergo as they pass through the damaged glomerular filtration barrier. In conditions affecting the glomeruli, such as glomerulonephritis, the red blood cells can become distorted, appearing smaller or having an irregular shape. This occurs because the cells experience trauma while navigating through the inflamed or injured glomerular capillaries. The presence of dysmorphic erythrocytes can be a useful indicator in differentiating glomerular blood loss from other sources of hematuria, such as lower urinary tract or urological causes, where red blood cells typically remain intact. In contrast, low urine osmolality is not specifically associated with glomerular hematuria; rather, it can occur in various renal and systemic conditions including diabetes insipidus or acute tubular injury. The presence of bacteria indicates a urinary tract infection or infectious process, which is not a characteristic finding of glomerular hematuria. Lastly, while immunoglobulin abnormalities can occur in certain glomerular diseases, they are not a direct finding related to hematuria itself; thus, they do not specifically pertain to