The role of ultrasonography in the study of medical nephropathy. Diagnostic techniques in nephrology include clinical history, physical examination, laboratory tests, scintigraphy, diagnostic imaging techniques as well as renal biopsy. In kidney diseases, ultrasonography is used as a first-line imaging technique, and its role in medical nephropathy is to exclude urological pathologies, to differentiate between acute and chronic renal failure, to follow-up on the course of a disease, to guide needle biopsy, etc. Ultrasound images are useful at characterizing the pelvis, assessing renal dimensions and parenchymal echogenicity, sampling color-power Doppler signals and evaluating their characteristics and distribution as well as measuring parenchymal resistive index. Taken together, these data can provide useful clues to the diagnosis and help to reduce the number of possible differential diagnoses.