Urology - Kidney Stone Centre
Mechanical Percussion and Inversion (MPI)
While shockwave lithotripsy is a very effective treatment for kidney stones, it sometimes leaves fragments in the lower portion of the kidney. Gravity and certain technical features of kidney anatomy can trap these pieces so that they settle in the lower pole and do not pass. They can enlarge over time to form new kidney stones or infections.
A combination of mechanical percussion and inversion (or MPI) can eliminate the sand particles before they can cause problems. During this treatment, the patient is placed on a stretcher with the top half of the body angled towards the floor. A large vibrator called a percussor is held against the skin of your back over the kidney that contains the stone fragments. A diuretic is administered to increase the flow of urine. The combination of these three factors helps the sandy particles to pass out of the lower pole and out of the body before they can enlarge and cause problems.