[Approach to suspected glomerulonephritis]

Glomerulonephritides (GNs) are inflammatory diseases of the glomeruli and may have primary or secondary causes. They frequently present as nephrotic or nephritic syndrome, and sometimes only as asymptomatic proteinuria or glomerular hematuria. Given that clinical presentations overlap and the underlying etiologies are diverse, kidney biopsy remains the gold standard for establishing the diagnosis, classification, and prognosis. Approximately two-thirds of GNs are primary and one-third secondary, for example in the context of collagen vascular diseases, vasculitides, metabolic disorders, or hematologic conditions. Accurate diagnosis relies on thorough history taking as well as urine and blood testing. Indicators of GN include proteinuria, dysmorphic erythrocytes, red blood cell casts, impaired kidney function, or newly developed hypertension. Proteinuria greater than 0.5 g/day or glomerular hematuria should always prompt further evaluation. Definitive diagnosis is obtained by biopsy, while serologic tests are important for identifying secondary forms. Prognosis varies widely. Rapidly progressive GN is a nephrological emergency and requires immediate inpatient evaluation and treatment.