genitourinary disorders
Rapidly Progressive Glomerulonephritis (RPGN)
Diagnosis of RPGN
Progressive renal failure over weeks to months Nephritic urinary sediment Serologic testing Serum complement levels Renal biopsy Diagnosis is suggested by Acute Kidney Injury (AKI) in patients with hematuria and dysmorphic red blood cells (RBCs) or RBC casts. Testing includes serum creatinine, urinalysis, complete blood count (CBC), serologic tests, and renal biopsy. Diagnosis is usually by serologic tests and renal biopsy. Serum creatinineis almost always elevated. Urinalysisshows hematuria is always present, and RBC casts are usually present. Telescopic sediment (ie, sediment with multiple elements, including white blood cells [WBCs]; dysmorphic RBCs; and WBC, RBC, granular, waxy, and broad casts) is common. OnCBC,anemia is usually present, and leukocytosis is common. Serologic testingshould include anti-GBM antibodies (anti-GBM antibody disease); antistreptolysin O antibodies, anti-DNA antibodies, or cryoglobulins (immune complex RPGN); and antineutrophil cytoplasmic antibodies (ANCA) titers (pauci-immune RPGN). Complement measurement(serum C3 and C4) may be useful in suspected immune complex RPGN because hypocomplementemia is common. Earlyrenal biopsyis essential. The feature common to all types of RPGN is focal proliferation of glomerular epithelial cells, sometimes interspersed with numerous neutrophils, that forms a crescentic cellular mass (crescents) and that fills Bowman space in>50% of glomeruli. The glomerular tuft usually appears hypocellular and collapses. Necrosis within the tuft or involving the crescent may occur and may be the most prominent abnormality. In such patients, histologic evidence of vasculitis should be sought. Immunofluorescence microscopyfindings differ for each type: In anti-GBM antibody disease, linear or ribbon-like deposition of IgG along the GBM is most prominent and is often accompanied by linear and sometimes granular deposition of C3. In immune complex RPGN, immunofluorescence reveals diffuse, irregular mesangial IgG and C3 deposits. In pauci-immune RPGN, immune staining and deposits are not detected. However, fibrin occurs within the crescents, regardless of the fluorescence pattern. In double antibody RPGN, linear staining of the GBM is present. In idiopathic RPGN, some patients have immune complexes and others have absence of immune staining and deposits. 