This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
[{'content': 'The prognosis of rapidly proliferating glomerulonephritis (Crecentric GN) depands upon - \nSelect and explain. \nA. Number of crescents, B. Size of crescents, C. shape of crescents, D. Cellularity of crescents', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Rapidly progressive glomerulonephritis (RPGN) is characterised by number of crescentsby rapid loss of renal function over days to weeks, usually in association with hypeension and oedema. Non-visible haematuria is almost always present with variable amounts of proteinuria, while characteristic red cell casts and dysmorphic red cells may be observed on urine microscopy . Renal biopsy typically shows crescentic lesions , often associated with necrotising lesions within the glomerulus , paicularly in small-vessel vasculitides. This pattern of presentation is typical of post-infectious glomerulonephritis, anti-GBM disease and small-vessel vasculitides (p. 1040). It can also be observed in SLE and occasionally in IgA and other nephropathies . Causes of glomerulonephritis associated with low serum complement * Post-infectious glomerulonephritis * Subacute bacterial infection, especially endocarditis * Systemic lupus erythematosus * Cryoglobulinaemia * Mesangiocapillary glomerulonephritis, usually complement type Ref Harrison20th edition pg 267', 'role': 'assistant'}]