A nephrologist is a physician who specializes in diagnosing and treating kidney problems, except for injuries or tumors. They determine when dialysis is needed and select patients for kidney transplantation. Patients who should see a nephrologist include those with suspected or known kidney failure, swelling of the face or feet, abnormal urine output, loin pain and fever, blood in the urine, long-term diabetes or hypertension, unexplained anemia, or a family history of kidney disease. A nephrologist can diagnose kidney problems early, recommend specific treatments, and help slow the progression of renal failure.