A 35-year-old man presents with sudden-onset left flank pain radiating to the groin and hematuria. A plain AP KUB X-ray is performed. The structure marked **B** in the diagram shows the expected anatomic course of the ureter. Which of the following represents the THREE normal anatomic sites where ureteric calculi preferentially lodge along this course?

Explanation

## Why "Pelviureteric junction (L2), pelvic brim at sacroiliac joint, and ureterovesical junction" is right The three normal anatomic narrowings of the ureter where kidney stones preferentially lodge are: (1) **Pelviureteric junction (PUJ)** at the level of L2, where the ureter originates from the renal pelvis; (2) **Pelvic brim / sacroiliac joint**, where the ureter crosses the iliac vessels — this is the second narrowing; and (3) **Ureterovesical junction (UVJ)**, which is the narrowest point overall and where the ureter enters the bladder. These three sites correspond to the anatomic course marked as **B** in the diagram, which descends along the tips of transverse processes L1–L5, crosses the sacroiliac joints, and then enters the bladder anteriorly. Knowledge of these three sites is essential for predicting stone location on imaging and planning intervention (Bailey & Love 28e; Harrison 21e Ch 311). ## Why each distractor is wrong - **"Renal hilum, mid-ureter at L3, and bladder trigone"**: The renal hilum is not a site of ureteric narrowing; the mid-ureter at L3 is not a recognized narrowing site; the bladder trigone is an anatomic landmark but not a site of ureteric narrowing. This conflates renal anatomy with ureteric anatomy. - **"Pelviureteric junction (L1), crossing of iliac vessels, and mid-ureter at L4"**: While the PUJ and crossing of iliac vessels are correct, the PUJ is at L2, not L1; and "mid-ureter at L4" is not a recognized narrowing site. The third narrowing is the UVJ, not a mid-ureteric point. - **"Renal pelvis, crossing of gonadal vessels, and ureteropelvic junction"**: The renal pelvis is not a ureteric narrowing; the crossing of gonadal vessels is not a site of ureteric narrowing; "ureteropelvic junction" is another term for the PUJ but is listed separately here, creating confusion. This option mixes renal and vascular anatomy. **High-Yield:** The three ureteric narrowings (PUJ at L2, pelvic brim at SI joint, UVJ) are the classic sites where stones lodge — essential for imaging interpretation and predicting clinical presentation. [cite: Bailey & Love 28e; Harrison 21e Ch 311]