Researchers studied 110 patients who suffered from kidney stones that were confined to one side of their body. Of this group, 93 patients consistently favored sleeping on one side. 75% of these patients had kidney stones on the same side. Dr. Marshall Stoller, a professor of urology at UCSF reported, “Sleeping in the same position each night appears to alter bloodflow to that kidney, impairing the organ’s ability to clear itself of stone-forming crystals and deposits.”