Early detection of deterioration in Kidney function is essential in preventing catastrophic outcomes in patients with kidney disease. Whereas, invasive methods to ascertain the kidney functions may be more accurate, but non-invasive methods are easier done and are more accessible. Interest is developing in newer techniques like evaluation of ureteric jet flow studies on ultrasonography. This textbook will go a long way in giving preliminary overview of all the non-invasive tests available to detect loss of kidney function or early deterioration therein.