"In patients who present with atraumatic flank pain with or without haematuria, a CT KUB is often the first test obtained as the differential is renal colic. Acutely the diagnosis is difficult on non-contrast scans, which may only demonstrate subtle swelling and surrounding stranding 1."
"from heart valve, ventricular or atrial thrombus, aorta"
"iatrogenic (e.g. angiography)"
"seen in infancy secondary to severe dehydration (e.g. gastroenteritis)"