American Board of Internal Medicine (ABIM) Certification Practice Exam

What type of morphology is commonly found in kidney biopsy for proliferative glomerulonephritis?

1. Normal glomeruli

2. Crescents

3. Atrophic tubules

4. Fibrosis

The correct answer is: Crescents

In the context of proliferative glomerulonephritis, the presence of crescents is a significant histological finding noted in kidney biopsies. Crescents form in the glomeruli due to the accumulation of inflammatory cells, particularly when there is severe damage to the glomerular capillary walls. This morphology is indicative of a more severe form of glomerular inflammation, often associated with conditions like rapidly progressive glomerulonephritis (RPGN) or certain forms of lupus nephritis. The development of crescents is a response to severe glomerular injury, and it reflects a rapid proliferation of cells in the Bowman capsule due to the infiltration of monocytes and macrophages, which leads to the crescentic formation. This is particularly relevant because the presence of crescents often correlates with a poor prognosis and signifies the need for urgent therapeutic intervention. In contrast, normal glomeruli would indicate a lack of disease activity, while atrophic tubules and fibrosis are associated with chronic kidney damage and later stages of renal disease rather than the acute processes seen in proliferative glomerulonephritis. Their presence would not be something expected in a biopsy focused primarily on acute inflammatory changes associated with this condition. Thus, cresc