Currently, the cause of loin pain-hematuria syndrome (LPHS) is unknown. Researchers have hypothesized that the syndrome may be due to blood vessel diseases of the kidney, spasms of the kidney vessels, or other bleeding disorders (coagulopathy).
The hematuria in LPHS may be due to an abnormal (thick or thin) glomerular basement membrane. The glomerular basement membrane is a tissue in the kidney that filters the blood. An abnormal glomerular basement membrane may allow red blood cells into the urinary space.
Because kidney stones are so common in people with LPHS, crystals in the kidney tubules may also play a part in bleeding and pain.