Why Kidney Stones Can Be a Problem
Stones don’t always stay in the kidney. Sometimes, they pass from the kidney into the ureters. Ureters are small and delicate, and the stones may be too large to pass smoothly down the ureter to the bladder. Passage of stones down the ureter can cause spasms and irritation of the ureters as they pass, which causes blood to appear in the urine.
Sometimes stones block the flow of urine. This is called a urinary obstruction. Urinary obstructions can lead to kidney infection (pyelonephritis) and kidney damage.