Urolithiasis/Endourology

Ureteral Stone Location at Emergency Room Presentation

With Colic

Brian H. Eisner,*,† Adam Reese, Sonali Sheth and Marshall L. StollerFrom the Department of Urology, School of Medicine, University of California-San Francisco, San Francisco, California

Purpose: It is thought that the 3 narrowest points of the ureter are the uretero-pelvic junction, the point where the ureter crosses anterior to the iliac vessels andthe ureterovesical junction. Textbooks describe these 3 sites as the most likelyplaces for ureteral stones to lodge. We defined the stone position in the ureterwhen patients first present to the emergency department with colic.Materials and Methods: We retrospectively reviewed the records of 94 consecu-tive patients who presented to the emergency department with a chief complaintof colic and computerized tomography showing a single unilateral ureteral cal-culus. Axial, coronal and 3-dimensional reformatted computerized tomographyscans were evaluated, and stone position and size (maximal axial and coronaldiameters) were recorded, as were the position of the ureteropelvic junction, theiliac vessels (where the ureter crosses anterior to the iliac vessels) and theureterovesical junction. Patients with a history of nephrolithiasis, shock wavelithotripsy, ureteroscopy or percutaneous nephrolithotripsy were excluded fromstudy. Statistical analysis was performed using Student’s t test and Pearson’scorrelation coefficient.Results: At the time of emergency department presentation for colic ureteralstone position was the ureteropelvic junction in 10.6% cases, between the ure-teropelvic junction and the iliac vessels in 23.4%, where the ureter crossesanterior to the iliac vessels in 1.1%, between the iliac vessels and the ureteroves-ical junction in 4.3% and at the ureterovesical junction in 60.6%. Proximal calculihad a greater axial diameter than distal calculi (mean 6.1 vs 4.0 mm) and agreater coronal diameter than distal calculi (6.8 vs 4.1 mm, each p �0.001). Axialand coronal diameters moderately correlated with stone position (r � �0.47 and�0.55, respectively, each p �0.001).Conclusions: Proximal ureteral stones were larger in axial and coronal diameterthan distal ureteral stones. At emergency department presentation for colic moststones were at the ureterovesical junction and in the proximal ureter between theureteropelvic junction and the iliac vessels. A few stones were at the ureteropelvicjunction and only 1 lodged at the level where the ureter crosses anterior to theiliac vessels, despite the literature stating that these locations are 2 of the 3 mostlikely places for stones to become lodged.

Abbreviations

and Acronyms

CT � computerized tomography

PCNL � percutaneousnephrolithotripsy

SWL � shock wave lithotripsy

UPJ � ureteropelvic junction

UVJ � ureterovesical junction

Submitted for publication November 20, 2008.Study received institutional review board ap-

proval.* Correspondence: Department of Urology,

University of California-San Francisco, 400 Par-nassus Ave., San Francisco, California 94143(telephone: 415-353-2200; FAX: 415-353-2641;e-mail: eisnerbh@urology.ucsf.edu).

† Financial interest and/or other relationshipwith Boston Scientific.

For another article on a related

topic see page 343.

Key Words: ureter, ureteral calculi, colic, emergencies

IT has long been urological dogmathat the 3 narrowest points in the ure-ter are the UPJ, the point where theureter crosses anterior to the external

iliac vessels, and the UVJ, and these

0022-5347/09/1821-0165/0THE JOURNAL OF UROLOGY®

Copyright © 2009 by AMERICAN UROLOGICAL ASSOCIATION

are the 3 most likely locations for ure-teral stones to lodge.1–5 With the ad-vent of medical expulsive therapy asfirst line treatment for the index pa-

tient with ureteral calculi6 it is impor-

Vol. 182, 165-168, July 2009Printed in U.S.A.

DOI:10.1016/j.juro.2009.02.131www.jurology.com 165

URETERAL STONE LOCATION AT EMERGENCY ROOM PRESENTATION WITH COLIC166

tant to understand the natural history of ureteralstone passage and the points in the ureter wherestones are likely to become lodged or impacted. Re-cent evidence suggests that historical teachings re-garding the UPJ, the level where the ureter crossesanterior to the iliac vessels and the UVJ as the mostlikely places to find an obstructing ureteral stonemay be inaccurate.7 We determined the exact loca-tion of ureteral stones when patients first presentedto the emergency department with colic.

MATERIALS AND METHODS

We retrospectively reviewed the records of 94 consecutivepatients who presented to the emergency department witha chief complaint of colic and unenhanced CT that showeda single unilateral ureteral calculus. Axial, coronal and3-dimensional reformatted CT images were evaluated by 2observers. Stone position and size (axial and coronal di-ameters) were recorded, as were the position of the UPJ,the site where the ureter crosses anterior to the iliacvessels and the UVJ. The UPJ was defined as the conver-gence of the renal pelvis and the ureter. The UVJ wasdefined as the segment of ureter that traverses the blad-der wall. Ureteral distances were calculated by subtract-ing CT slice numbers and multiplying by CT cut thick-ness. Patients with a history of nephrolithiasis, SWL,ureteroscopy or PCNL were excluded from study. Statis-tical analysis was performed using Student’s t test andPearson’s correlation coefficient.

RESULTS

The records of 94 patients were analyzed. Mean agewas 43.6 years (range 23 to 74). The female-to-maleratio was 17:77. CT cut thickness was 0.625 mm in 2patients (2.1%), 1.25 mm in 81 (86.2%), 2.5 mm in 3(3.2%) and 5 mm in 8 (8.5%). Calculi were located inthe left ureter in 42 patients (45%) and in the rightureter in 52 (55%). There was no difference in meanureteral length between females and males (21.7 vs20.9 cm, p � 0.25).

At emergency department presentation for colicureteral stones were at the UPJ in 10 cases (10.6%),between the UPJ and the iliac vessels in 22 (23.4%),where the ureter crosses anterior to the iliac vesselsin 1 (1.1%), between the iliac vessels and the UVJ in4 (4.3%) and at the UVJ in 57 (60.6%) (see figure).

The 22 stones in the proximal ureter (between theUPJ and the iliac vessels) were significantly closerto the UPJ than to the iliac vessels. Mean distancebelow the UPJ was 4.3 cm (range 0.75 to 7.5) andmean distance above the iliac vessels was 8.9 cm(range 5.0 to 12.5) (p �0.001). The 4 stones in thedistal ureter (between the iliac vessels and the UVJ)were significantly closer to the UVJ than to the iliacvessels. Mean distance below the iliac vessels was4.9 cm (range 3.5 to 6) and mean distance above the

UVJ was 1.75 cm (range 1.25 to 2.25) (p � 0.001).

Proximal calculi in 28 patients had a greater meanaxial diameter than distal calculi in 65 (6.1 mm, range2.0 to 16.3 vs 4.0, range 1.8 to 7.2, p �0.001) as well asa greater coronal diameter than distal calculi (6.8 mm,range 1.8 to 15 vs 4.1, range 1.9 to 10.2, p �0.001).Axial diameter and coronal length moderately corre-lated with stone position (r � �0.47 and �0.55, respec-tively, each p �0.001).

DISCUSSION

We examined the veracity of what has long beentaught in urology, that the UPJ, the site where theureter crosses anterior to the iliac vessels and theUVJ are the 3 narrowest points in the ureter andthe likeliest places for stones to lodge.1–5 Despitehistorical teachings there is a paucity of corroborat-ing evidence. Older data relied on traditional excre-tory urography and plain abdominal x-ray to deter-mine stone location. These studies cannot definitivelyidentify the site of the iliac vessels and may not beable to identify the site of the UPJ and UVJ asaccurately as CT.8–10 Recent data suggest that themost common places where stones become impacted

Ureteral stone location at emergency department presentationwith colic.

in the ureter may not be at those 3 sites.7

URETERAL STONE LOCATION AT EMERGENCY ROOM PRESENTATION WITH COLIC 167

Our findings contradict what has been taught toresidents in urology, surgery, medicine, emergencymedicine and medical students for decades. Wefound that the 2 most common places for stones tolodge at emergency department presentation withcolic were the UVJ (60.6% of cases) and the proximalureter between the UPJ and the iliac vessels (23.4%).A few stones were located at the UPJ (10.6%) andthe distal ureter (4.3%), and only 1 (1.1%) was at theiliac vessel level. While textbooks are correct aboutthe UVJ, our findings do not agree with the state-ment that stones often lodge at the UPJ or where theureter crosses anterior to the iliac vessels. Our anal-ysis included patients upon initial presentation tothe emergency room and excluded those with a his-tory of nephrolithiasis, or any surgical or minimallyinvasive treatment for nephrolithiasis to ascertainthe location of stones when colic first becomes severeenough to bring patients to the emergency depart-ment.

We also found that axial and coronal diametersmoderately correlated with ureteral stone position.The smaller the stone, the more likely it is to passdown to the distal ureter. This is consistent withpreviously published data.11

Schuler et al recently examined the site of ure-teral stones in a patient referred to a urologicalclinic for extracorporeal shock wave lithotripsy.7

Histogram analysis showed 2 peaks of calculous dis-tribution, that is the first adjacent to the proximalborder of the third lumbar vertebra and the secondin the pelvic ureter near the UVJ. There was nohistogram peak at the point where the uretercrosses anterior to the iliac vessels. However, thereare several important distinctions between thatstudy and ours. That group examined patients re-ferred for SWL, not at the time of emergency depart-ment presentation with renal colic. In some if not allof their patients presumably several weeks wouldhave passed between the initial presentation withcolic and the time of imaging for SWL. Their studydoes not reflect the position in patients when theyfirst present with colic. In contrast, we examinedpatients upon the initial presentation to the emer-gency department. In addition, they did not distin-guish patients who had previously passed stones orhad been previously treated with ureteroscopy orPCNL from those who had not.7 In our study pa-tients with a history of previous stone passage, ure-teroscopy, SWL or PCNL were excluded to avoid thepossible confounding effects of previous stone pas-sage or surgery. Thus, we believe that we addressedthe natural history of ureteral stone passage in ure-ters that have not been previously instrumented or

altered by inflammation due to prior stone passage.

To our knowledge no studies have truly examinedvariations in ureteral diameter with respect to ure-teral site. However, 2 groups have radiographicallyexamined ureteral width. Zelenko et al examined 212patients with a single obstructing ureteral stone.12

The obstructed ureter and the ureter without a stonewere measured. Findings showed that the mean ax-ial diameter of the ureter that did not contain astone was 1.8 mm (range 1 to 6) and 96% of ureterswere 3 mm or less in diameter. Eisner et al looked atthe 2 ureters in 50 patients who presented for ure-teroscopy with a single obstructing ureteral calcu-lus.13 Ureteral diameter was measured and strati-fied by location. For unobstructed ureters there wasno statistically significant difference between prox-imal and distal ureteral diameters (4.3 vs 3.8 mm, pnot significant).

There are several inherent weaknesses of ourstudy. It is a retrospective study and, thus, subject tothe shortcomings of retrospective review. In addition,although we report the site where stones lodged at thetime of emergency department presentation withcolic, we did not measure ureteral diameter to con-firm whether stone site corresponded with ureteraldiameter. It is possible that the UPJ and the levelwhere the ureter crosses anterior to the iliac vesselsmay be 2 of the 3 narrowest points of the ureter butthey are not among the most common places forstones to lodge when patients present with colic.Also, there were significantly more men than womenin our study (77 vs 17). This occurred by chance, iethis was the gender ratio after excluding patientsineligible for study. While it is known that nephro-lithiasis occurs with greater frequency in men thanin women,6 theoretically this could confound ourresults if differences exist between male and femaleureters. Finally, we did not examine outcomes,which would be interesting with respect to our find-ings. A future study of the rate of spontaneous pas-sage relative to initial obstruction site would yieldinteresting information for clinicians.

CONCLUSIONS

This study shows that a few stones lodge at the UPJand the point where the ureter crosses anterior tothe iliac vessels. Most stones lodge at the UVJ andthe proximal ureter (60.6% and 23.4%, respectively).Based on our findings we have certain recommenda-tions for clinicians who evaluate patients with colic.1) When interpreting plain x-ray of the kidneys,ureters and bladder, the points of focus should bethe UVJ and the upper ureter, which accounted for84% of stones in our study. 2) When evaluating colicon abdominal ultrasound, the study should be per-formed in a patient with a full bladder (to serve as

an acoustic window) to best visualize the UVJ.

URETERAL STONE LOCATION AT EMERGENCY ROOM PRESENTATION WITH COLIC168

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