Definition: Nephrology is the medical specialty which focuses on the treatment of kidney conditions and abnormalities. A physician who practices nephrology is called a nephrologist. Nephrology is a subspecialty of internal medicine. Therefore, a nephrologist would complete the same training as an internist, and then complete an additional fellowship in nephrology. Nephrologists diagnose causes and levels of kidney failure, and prescribe appropriate treatment such as medication, diet changes, or dialysis. If none of these treatments work, a kidney transplant would be performed by a transplant surgeon.