Renal involvement or complications in systemic diseases occur frequently and crucially influence patient outcomes. In addition to functional renal failure caused by medications (especially nonsteroidal antirheumatic agents), typical nephrological complications in rheumatology include manifestations of the underlying condition which range from mild disorders of renal function to severe and partially irreversible disease progression. The primary physician thus plays a key role in ensuring rapid and specific diagnostic workup and initiating appropriate treatment measures. Sonography and examination of urine sediment still take priority in the differential diagnosis. The indication for kidney biopsy should be broadly defined. Early initiation of immunosuppression in systemic diseases can decisively improve renal prognosis. Despite the current availability of considerably improved pharmacological options, numerous questions about the ideal therapeutic regimen still remain open.