Causes
Kidney or bladder stones
Stones in the kidneys or bladder [2] are a common cause of hematuria. These stones are minerals that have clumped together to form crystals in your bladder or kidneys. These crystals vary in size and some may be difficult to pass out.
Sometimes these stones block the urethra and cause severe pain. The abrasion and irritation of the urethral wall can cause bleeding. Stones may cause either gross or microscopic hematuria.
Kidney injury
Trauma [3] to the flank, sides, or back that affects the kidney may cause it to rupture or tear. This can make blood leak into the urine being formed in the kidneys.