Quiz: The case of the missing stone

Oct 09, 2019

Igor Sorokin, MD, presents the case of a 36-year-old female in whom two proximal stones are seen on KUB, but intraoperatively, only one stone is seen.

A 36-year-old female presented 1 month ago with right sided flank pain and two proximal ureteral stones were seen on KUB (figure 1a). She had not seen the stones pass since that KUB and pain did not improve. Therefore, she underwent right ureteroscopy with laser lithotripsy and stent placement (figure 1b). Intra-operatively, only one of the stones in the proximal ureter was seen. The patient was discharged home the same day but returned to the emergency room 2 days later with intractable right flank pain. Based on the imaging in figure 1, what are you suspicious of?

A. Duplicated collecting system

B. Post-operative stent pain

C. Migrated stone into kidney

D. Pyelonephritis

Continue to the next page for the answer.


A. Duplicated collecting system



Duplication of the collecting system is the most common anomaly of the urinary tract. On closer inspection of the image in figure 1a, the stones are not aligned with the course of one ureter. In figure 2b, the arrow points to the second stone seen just medial to the ureter. Often in an effort to reduce radiation by using the settings of “pulse” and “low dose” mode, the very radiopaque appearing stones on KUB are only seen faintly on intra-operative imaging. The patient went back to the operating room where she was found to have a completely duplicated collecting system. The second stone was found in the proximal ureter of the upper pole moiety and was fragmented and removed with stent placement (figure 2b).


Suggested reading


Ureteral duplication and its complications. RadioGraphics 1997; 17:109-27


Dr. Sorokin, Assistant Professor at the University of Massachusetts, Worcester, MA, is section editor for Urology Times Clinical Quiz.