Infarction means tissue death from blood circulation getting cut off. In the kidney, it’s very rare, but signs and symptoms can look just like a much more common Kidney Stone or Infection (pain, blood in the urine, maybe fever). We’d only think of Infarction when tests for the other conditions don’t pan out. Diagnosis is made by a CT scan which may need to be specially timed, to catch injected dye when it reaches the kidney.
Kidney infarctions can be caused by trauma, by clots from Atrial Fibrillation (an irregular heart rhythm) or from artificial heart valves, or by hereditary diseases that make blood clot inappropriately inside the body. Sometimes they’re caused by estrogens in birth control pills (very rare). And sometimes the cause is simply unknown.