Answer: C

Medullary angiitis is a histopathologic lesion within the renal medulla that is characterized by interstitial hemorrhage with associated neutrophilic inflammation and karorrhectic debris. While the finding is somewhat non-specific in etiology, it has been seen in cases of ANCA-associated glomerulonephritis, IgA nephropathy, and patients with prior infection treated with antibiotics (see reference).

Reference:

Hendricks AR, Harris AA, Walker PD, et al. Renal medullary angiitis: a case series from a single institution. Human Pathology (2013); (44): 521-525.