How does a kidney stone cause damage to the kidney?

A kidney stone can damage the kidney mainly by blocking the normal flow of urine and irritating the urinary tract.

When a stone gets stuck in the kidney or ureter, urine backs up and increases pressure inside the kidney. This pressure can stretch and damage delicate kidney tissues, reducing how well the kidney filters blood. Over time, prolonged blockage can lead to hydronephrosis (swelling of the kidney) and even permanent kidney damage.

Kidney stones can also scrape and irritate the lining of the kidney and urinary tract as they move, causing inflammation, bleeding, and pain. If bacteria are present, the blockage can trap urine and lead to infection, which further damages kidney tissue.

In short, kidney stones harm the kidney by causing obstruction, increasing pressure, triggering inflammation, and sometimes leading to infection, all of which can impair kidney function if not treated.