Rapidly progressive glomerulonephritis is characterized by the acute, rapid loss of renal function due to severe glomerular damage. The glomerular filtration rate decreases significantly over days, weeks, to months and may result in irreversible renal failure.
Patients with rapidly progressive glomerulonephritis may initially present with vague, non-specific symptoms such as body aches and pains, pallor, peripheral edema, lethargy, and/or fatigue . Conversely, patients may present with more renal specific symptoms including hematuria, anemia, oliguria, hypertension, and/or peripheral edema . An elevated serum creatinine and renal insufficiency is almost always a presenting feature. The most frequently occurring prodrome of ANCA-associated vasculitis, including rapidly progressive glomerulonephritis, consists of flulike symptoms (e.g., fever, body aches, loss of appetite, chills, weight loss, malaise) . Following this prodrome, patients may develop abdominal pain, a migratory polyarthropathy, and cutaneous ulcerations and/or nodules. Patients may also present with symptoms of sinusitis, cough, and/or hemoptysis when there is pulmonary involvement . Patients with immune-related rapidly progressive glomerulonephritis, such as anti-GBM disease in which the patient has antibodies directed against the alveolar basement membranes, may present with extra-renal symptoms such as hemoptysis and pulmonary hemorrhage. Subsequently, the pulmonary bleeding may result in anemia, iron deficiency, pallor, and weakness.
Blood chemistry and serologic tests should be ordered 'stat' on any patient suspected of having rapidly progressive glomerulonephritis. If clinically indicated, a renal biopsy may also be performed.
Blood serum test results will consist of an elevated creatinine level usually exceeding 3 mg/dL, decreased glomerular filtration rate, elevated erythrocyte sedimentation rate, and C-reactive protein . Complete blood count with differential will show an elevated neutrophil count and thrombocytes. A urinalysis will usually show dysmorphic hematuria, casts, and proteinuria.
Serologic testing should include the following: ANCA, anti-glomerular basement membrane antibodies, anti-dsDNA antibody, complement assays, antinuclear antibodies, and others as indicated from the clinical history, examination, and biopsy results . C3 and C4 complement levels are usually either normal or slightly elevated in patients with rapidly progressive glomerulonephritis type I and III. Circulating anti-GBM antibodies are present in type I rapidly progressive glomerulonephritis. Most patients with type III disease are positive for myeloperoxidase (MPO)–ANCA .
A kidney biopsy can be used to achieve the diagnosis of various types of rapidly progressive glomerulonephritis (types I, II, III). A microscopic examination of renal tissue will show crescentic glomerulonephritis . Crescent formation is a result of a response to injury to the glomerular capillary walls . The extent of crescent formation is correlated with the disease severity; patients that have crescent formations in less than half of their glomeruli are likely to have a mild disease course and full recovery, whereas those with greater than three-quarters of glomeruli present with advanced renal failure that is refractory to therapy .
Chest X-ray and/or chest computed tomography (CT) may be useful for patients with vasculitis and Goodpasture syndrome  . Patients may have a normal/negative chest X-ray and a chest CT that shows reticulonodular infiltrates. An abdominal and renal ultrasound can be used to evaluate echogenicity, renal atrophy or enlargement, and rule out obstruction .