Renal involvement and renal function disorders are commonplace in patients with rheumatic diseases and are often decisive for the prognosis. Typical nephrological complications in rheumatology are renal manifestations or delayed sequelae of the underlying disease in addition to drug-induced renal failure, e.g. by nonsteroidal anti-inflammatory drugs (NSAIDs). The differentiation from other common causes of disturbed renal function (e.g. diabetes and hypertension) is important and often difficult in individual cases. Renal involvement can be clinically manifested in many different ways. The spectrum ranges from slight functional disorders with, for example discrete erythrocyturia/proteinuria and normal renal function up to rapidly progressive renal failure. The probability of renal damage also varies greatly between different underlying diseases. For example, renal involvement in rheumatoid arthritis is a rarity but in contrast relatively normal in systemic lupus erythematosus. In the course of the differential diagnostics urine sediment, protein values and sonography are still the most important factors and the indications for kidney biopsy should be generously applied. Early initiation of immunosuppression can substantially improve the renal prognosis of inflammatory systemic diseases.
