A 19-year-old female college student presents to the emergency department at 10:30 PM on a Friday night with severe left-sided flank and pelvic pain. While she has never had similar pain, she states that she thinks she has a kidney stone. The pain started in her mid-back about a week ago and then subsided and now the pain has increased and moved interiorly along her flank and also extends down into her labia majora. She is taking birth control pills, but is not currently sexually active. She is having her period, but denies the pain is menstrual. Abdominal and pelvic CT are ordered. What two specific locations will one look for in the CTs for obstructing calculi?

Answer: (d) As the ureter crosses the external iliac artery at the pelvic brim and as the ureter passes through the wall of the bladder.* Renal and ureteric calculi generally are formed in the kidneys and then lodge at one of three locations:o at the junction of the renal pelvis with the ureter;o as the ureters cross the external iliac vessels at the pelvic brim;o as the ureters pass through the wall of the bladder.* Calculi occasionally form in the minor or major calyces or in the renal pelves and infundibula, but those so called "staghorn"calculi, would produce mid-back pain.* Renal calculi rarely become stuck as the ureter crosses the edge of the false pelvis.* The ureter does not pass through the center of the trigone, but rather opens at the superior lateral edge of the trigone.* The referred pain from ureteric calculi is usually described as from "loin to groin" in that it often starts in the mid back then over the kidney and extends in a band toward the labia majora or scrotum (from T11-L2).* Normally the pain is intermittent and comes and goes in waves and may change in location, generally moving interiorly.* Since the ureters undergo peristaltic movement, the calculi often move with time.