Variations Among Urology Trainees in Their Use of Fluoroscopy During Ureteroscopy

Abstract

Background and Purpose:

Recently, surgeon behavior has been identified as a determinant of fluoroscopy time (FT) during ureteroscopy (URS). In a training program, postgraduate trainees (PGTs) assist in performing URS under direct supervision of an attending urologist. Therefore, the aim of the present study was to assess variations among PGTs in their use of FT during URS.

Patients and Methods:

A retrospective review of prospectively collected data was performed for consecutive patients undergoing URS between July 2009 and December 2010 using standard fluoroscopy (30 frames per second). Urology PGTs in the fourth year assisted in performing these cases under the direct supervision of a single endourologist. Patient and stone characteristics together with operative data were compared among PGTs using univariate and multivariate analyses.

Results:

Seven PGTs (A, B, C, D, E, F, and G) assisted in 100 URS with a median (range) of 13 (11–18) procedures per trainee. Mean FT (95% confidence interval) for trainees A through G were 194 (115–272), 104 (65–144), 91 (66–117), 117 (58–175), 91 (52–131), 107 (7–143), and 64 (36–91) seconds, respectively (P=0.004). There were no significant differences among trainees in terms of patient (age and sex), stone (size, laterality, location, and multiplicity), and operative characteristics (operative time and balloon dilation) (P>0.05). Trainees, however, varied significantly in their use of access sheath (P=0.03). Trainees, male sex, balloon dilation, ureteral access sheath, and residual stones maintained their significance as predictors of FT on multivariate analysis.

Conclusion:

PGTs, in addition to male sex, balloon dilation, ureteral access sheath, and residual stones were significant predictors of FT during URS. Whether these differences in the behavior of PGTs are intrinsic to themselves or from perioperative factors remains to be clarified.

Introduction

I ntraoperative fluoroscopy is used to guide endourologic procedures. In spite of being minimally invasive, these interventional procedures might be complex and lengthy, which may result in high radiation exposures to both patients and surgeons.¹ Although the amount of radiation received from fluoroscopy during ureteroscopy (URS) may not be large, the effects of radiation are cumulative.²

There has been recent interest in assessing and minimizing the amount of radiation used during endourologic procedures, especially URS. While earlier studies focused on patient, stone, and technical aspects of URS to determine factors affecting fluoroscopy time (FT) during URS, recent work has revealed that surgeons themselves play a significant role in minimizing the amount of FT during URS.^3,4 Furthermore, when urologists were observed and feedback was given in terms of amount of FT used, there was a 24% decrease in FT.⁵

Because urologists at academic centers often have postgraduate trainees (PGTs) assisting them with procedures such as URS, they could also introduce a confounding variable in the FT used during endourological procedures. Previous studies have not examined this factor. Therefore, the aim of the present study was to assess variations in FT among PGTs assisting a single fellowship-trained endourologist performing URS.

Patients and Methods

A retrospective review of prospectively collected data was performed for consecutive patients undergoing URS by a single fellowship-trained endourologist (SA) assisted by urology PGTs in their fourth-year between July 2009 and December 2010. The attending urologist was scrubbed throughout every URS and instructed PGTs to minimize FT during each case.

Preoperative patient (age, sex) and stone characteristics (size on preoperative CT scan, side, location, radiolucency, and multiplicity) were recorded. Intraoperative data (operative [OR] time, FT, preoperative ureteral stentplacement, ureteral balloon dilation, use of ureteral access sheath, type of ureteroscope used, and stone-free status) were recorded immediately postoperatively on research data forms. Stone composition was reviewed to differentiate radiolucent calculi. Stone-free status was defined as absence or presence of <3 mm fragments using intraoperative assessment and postoperative imaging studies.

Six procedures were excluded for having congenital renal anomalies, ureteral stricture, or partial staghorn stones. Another 11 procedures were excluded because they were assisted by third-year and fifth-year PGTs. A standard fluoroscopic unit using 30 frames per second was used in all cases, and intraoperative FT was recorded by the attending urologist from the timer on the C-arm and confirmed from the final radiology reports. All fluoroscopic procedures were performed using a C-arm unit (OEC 9900 Elite, General Electric). The foot pedal was controlled by the PGTs assisting these URS procedures.

Technique of URS

All URS were performed under general anesthesia with the patient in the lithotomy position and broad spectrum antibiotic prophylaxis. Cystoscopy was performed first to negotiate a safety wire consisting of Sensor^™ guidewire (Microvasive Boston Scientific, Natick MA). A 7F semirigid ureteroscope (Storz, Tuttlingen, Germany) followed to visualize ureteral stones when intracorporeal lithotripsy, if indicated, was performed using holmium:yttrium-aluminum-garnet laser using either 200 μ or 365 μ laser fibers at a setting of 10 W. Whenever possible, stones were fragmented and removed using Zero Tip^™ basket (Boston Scientific, Natick, MA) rather than pulverized. For proximal ureteral and renal stones, a second wire was placed, a 14 to 16F Peel-Away (Cook Urological, Inc, Spencer, IN) ureteral access sheath was placed and a 7.5F Storz Flex-X^™ ureteroscope was used. When difficulty was encountered in negotiating tight ureteral segments, an 18F balloon was used to dilate these segments to allow placement of the ureteral access sheath.

All patients had postoperative 6F double pigtail indwelling ureteral stents placed at the end of the procedure and removed 1 week later if there were no residual stones larger than 3 mm diagnosed intraoperatively. Otherwise, patients were followed by serial radiography of the kidneys, ureters, and bladder before removal of the ureteral stent to make sure of stone-free status (≤3 mm). In the presence of significant residual fragments, a repeated flexible URS was scheduled.

Statistical analysis

Data analysis was performed using the commercially available Statistical Package of Social Sciences for Windows (SPSS, Chicago, IL), version 17. Descriptive data were presented in terms of number, percentages, means, and 95% confidence interval (CI) of the mean. Continuous variables were compared using a test of analysis of variance while the Fisher exact test was used to compare categorical variables with two-tailed P<0.05 considered as statistically significant. General linear model was used for multivariate analysis to correct for patient and stone characteristics, duration of surgery, and surgical outcome. Univariate and multivariate linear regression analyses were used to determine predictors of FT.

Results

PGTs were arranged chronologically according to their rotation. Of the 100 URS procedures, seven PGTs (A, B, C, D, E, F, and G) assisted in 11, 18, 18, 11, 16, 13, and 13 URS, respectively, with a median (range) of 13 (11–18) URS per trainee (Table 1). There were no significant differences regarding patient (age and sex) and stone characteristics (laterality, size, location, multiplicity, and radiolucency) (P>0.05) (Table 1). In terms of operative characteristics, OR time, type of ureteroscopes used, and balloon dilation were comparable among trainees (P>0.05). There were significant differences among trainees in their use of the ureteral access sheath (P=0.03). This ceased to be significant after correction for other patient, stone, and operative confounders. Most importantly, there were significant differences in the mean FT (95% CI) used among PGTs with FT ranging from 194 to 64 seconds (P=0.004) (Table 1) (Fig. 1).

FIG. 1.

Mean fluoroscopy time used by postgraduate trainees during ureteroscopy. CI=confidence interval.

Table 1.

Patient, Stone, and Operative Characteristics

PGT
Variable	A No (%)	B No (%)	C No (%)	D No (%)	E No (%)	F No (%)	G No (%)	P value
No. of URS	11	18	18	11	16	13	13	NA
Male sex	7 (64)	12 (67)	12 (67)	8 (73)	12 (75)	7 (54)	8 (62)	0.74
Mean age (years) (95% CI)	55 (47– 64)	50 (41–58)	55 (48–63)	50 (39–60)	56 (48–64)	56 (46–65)	50 (43–57)	0.69
Left-sided	7 (58)	9 (50)	7 (35)	5 (45)	11 (69)	10 (63)	6 (46)	0.58
Mean stone size (mm) (95% CI)	15 (10–20)	19 (9–29)	12 (10–15)	11 (7–14)	12 (8–15)	11 (8–14)	9 (6–11)	0.10
Stone location
Ureteral	3 (27.3)	9 (50)	6 (33.3)	6 (54.5)	9 (56.2)	7 (53.8)	5 (38.5)	0.57
Renal	6 (54.5)	8 (44.4)	7 (38.9)	4 (36.4)	5 (31.3)	4 (30.8)	6 (46.1)
Both	2 (18.2)	1 (5.6)	5 (27.8)	1 (9.1)	2 (12.5)	2 (15.4)	2 (15.4)
Multiple stones	6 (54.5)	6 (33.3)	7 (38.9)	2 (18.2)	5 (31.3)	4 (30.8)	5 (38.5)	0.46
Lucent stones	3 (27.3)	2 (11.1)	3 (16.7)	0 (0)	3 (18.7)	1 (7.7)	0 (0)	0.15
Preoperative stents	3 (27.3)	11 (61.1)	13 (72.2)	4 (36.4)	8 (50.0)	8 (61.5)	10 (76.9)	0.16
URS type
Flexible	6 (54.5)	9 (50.0)	8 (44.4)	5 (45.4)	6 (37.5)	6 (46.1)	2 (15.4)	0.84
Rigid	1 (9.1)	4 (22.2)	3 (16.7)	1 (9.1)	2 (12.5)	1 (7.7)	4 (30.8)
Both	4 (36.4)	5 (27.8)	7 (38.9)	5 (45.4)	8 (50.0)	6 (46.1)	7 (53.8)
Balloon dilations	1 (9.1)	2 (11.1)	1 (5.6)	2 (18.2)	0 (0)	0 (0)	2 (15.4)	0.77
Access sheath	7 (63.6)	10 (55.6)	8 (44.4)	5 (45.5)	6 (37.5)	5 (38.5)	3 (23.1)	0.03
Residual stone	2 (18.2)	5 (27.8)	3 (16.7)	2 (18.2)	3 (18.7)	1 (7.7)	2 (15.4)	0.35
Mean OR time (min) (95% CI)	79 (50–107)	75 (59–91)	81 (67– 94)	66 (57–74)	81 (60–101)	76 (57– 95)	83 (56–110)	0.90
Mean FT (sec) (95% CI)	194 (115–272)	105 (65–144)	91 (66–117)	117 (58–175)	91 (52–131)	107 (71–143)	64 (36–91)	0.004

PGT=postgraduate trainees; URS=ureteroscopy; NA: not applicable;

CI=confidence interval; OR time=operative time; FT=fluoroscopy time.

On univariate analysis to analyze predictors of FT, there was a significant increase in FT with renal stones (22 sec, P=0.048), larger stone sizes (1.6 sec/mm, P=0.04), and longer OR times (6.9 sec/10 min, P=0.004). These variables, however, lost their significance on subsequent multivariate analysis (Table 2). Significant predictors of FT on univariate analysis that maintained their significance on multivariate analysis were: Male sex (34 sec more FT, P=0.02), balloon dilation (81.7 sec more FT, P=0.004), residual stones (54.1 sec more FT, P=0.01), ureteral access sheaths (41.7 sec more FT, P=0.03), and trainees (P=0.02) (Table 2). Specifically, trainee A had significantly more (74.5 sec; P=0.01) and trainees E and G had significantly less FT (8.7 sec; P=0.02) and (36.7 sec; P=0.04), respectively.

Table 2.

Predictors of Fluoroscopy Time on Univariate and Multivariate Analyses

	Univariate		Multivariate
Variable	Change (sec)	P value	Change (sec)	P value
Trainee
A	98.3	0.001	74.5	0.01
B	−2.0	0.92	3.4	0.81
C	−18.1	0.39	−12.4	0.32
D	11.7	0.65	8.7	0.72
E	−17.8	0.04	−8.7	0.02
F	1.0	0.97	2.3	0.82
G	−48.8	0.03	−36.7	0.04
Male sex	29.6	0.04	34	0.02
Age	8.8/10 years	0.11	6.8/10 years	0.15
Left-sided	−11.6	0.74	6.8 sec	0.63
Stone size	1.6/mm	0.04	0.38	0.67
Renal stones	22.0	0.048	16.0	0.26
Multiple stones	14.8	0.38	− 26.6	0.19
Lucent stones	6.5	0.79	14.6	0.52
Preoperative stents	−23.6	0.14	−25.4	0.08
Flexible ureteroscopy	4.0	0.69	−3.9	0.69
Balloon dilation	115.7	0.001	81.7	0.004
Access sheath	62.4	0.001	41.7	0.03
Residual stones	67.6	0.001	54.1	0.01
Operative time	6.9/10 min	0.004	4.2/10 min	0.07

Discussion

Fluoroscopy is the main source of occupational radiation exposure among endourologists. In a national study examining trends in incidence and management of urolithiasis, there was a 63% increase in the number of hospital admissions and 127% increase in the number of URS being performed from 2000 to 2010 (from 6283 to 14,242 cases per year).⁶ With increasing incidence of urolithiasis and use of CT scanners for diagnosis and URS for management, the potential for excess radiation exposure for both patients and operating room personnel exist.^7,8 On average, patients are exposed to an effective dose of 1.13 mSv (range 0.31–7.17) per URS.⁹ Furthermore, the urologist's lower legs and feet are exposed to an average of 11.6 and 6.4 μGy per ureteroscopic case.¹⁰

Previous research in radiation exposure during endourological procedures has concentrated on factors relating to patient, stone, procedure, and fluoroscopy unit while rarely evaluating impact of the operator on FT.¹¹ The study by Bagley and Cubler-Goodman³ was the first to show that when the urologist controlled the foot pedal with the use of “last-image hold” technology, there was a significant decrease in FT from 4.7 minutes down to 0.62 minutes per combined flexible and rigid URS case.

Recently, it has been shown that there are significant differences in fluoroscopy use among urologists performing the same URS procedure.⁴ Thus, surgeon behavior during URS was one of the most significant predictors of FT on multivariate analysis.⁴ In addition, Ngo and colleagues⁵ have shown that surgeon behavior during URS could be modified by giving feedback on their use of FT.⁵ Specifically, there was a 24% decrease in FT per URS case over a 3-year period.⁵

Urologists, however, do not perform URS procedures alone in academic training centers. They often supervise senior PGTs who perform these procedures under the direct supervision of the attending urologist. Therefore, the aim of the present study was to ascertain the role of these PGTs in the use of FT during URS. The present study showed that although there was a trend of decreasing FT over consecutive PGTs, there were significant variations among the PGTs in the use of FT during URS (Fig. 1). These differences maintained their significance on multivariate analysis.

All PGTs were given the same radiation safety lecture at the beginning of the academic year. Furthermore, this was their first exposure to URS procedures without any simulation training. There could be several hypotheses as to the significant differences in their use of FT during URS. First, these could be because of different learning curves of different PGTs in performing URS.¹² For example, the Accreditation Council for Graduate Medical Education minimum requirements for URS is 40 procedures.¹³ Therefore, it is possible that these PGTs may not have reached their competency with a median number of 13 URS. Second, the differences in FT seen among the PGTs reflect the difficulty in changing the behavior and clinical practice pattern of some trainees. A recent study found that most PGTs did not change their prescribing patterns after being educated about radiation exposure from CT. Only 30% of PGTs modified their behavior in reducing radiation exposure from CT scans.¹⁴ Third, “halo” and “de-halo” effect may have played a role. This halo effect originally described by Thorndike in 1920 describes the phenomenon that a good or bad performance in one area affects assessments in other performance domains.^15,16 Therefore, a PGT who has excelled in endourology research may be perceived to have superior technical skills and is allowed to perform more of the procedure with fewer demands from the attending urologist for fluoroscopic confirmation of the location of the instruments. Finally, it is possible that the Hawthorne effect, with increased awareness and experience of the attending urologist, contributes to the trend of decreasing FT with subsequent PGTs.¹⁷

In addition to PGTs being significant predictors of FT during URS, male sex, balloon dilation, residual stones at the end of the procedure together with the use of an access sheath were other significant independent predictors of FT on multivariate analysis (Table 2). Male sex has been previously reported to be associated with increased FT.^4,5 Perhaps this is related to the use of fluoroscopy in addition to endoscopic cues to identify anatomic landmarks such as ureteral orifices in male patients, especially in those with enlarged prostatic lobes.

The effect of residual stones on FT may be explained by the increased attempts to localize and clear these residual stone fragments to achieve stone-free status. It makes sense that the use of balloon dilation and ureteral access sheaths are associated with significantly higher FT during URS because these maneuvers necessitate fluoroscopic guidance and monitoring to avoid ureteral injury. Similarly, Ngo and colleagues⁵ found that the use of ureteral access sheath (P=0.04) and balloon dilation (P=0.0001) were associated with significantly higher FT during URS.

There are several potential limitations to the present study, including its retrospective nature, the relatively small number of URS performed by each PGT, and the unequal number of URS procedures per PGT. During their short endourology rotations, there were no significant reductions in FT. It is possible that once PGTs gain more experience in URS, their use of FT may decrease. It is important to recognize, however, that there are significant variations in the intraoperative behavior of PGTs apparent even when relatively small numbers of PGTs are studied for a short time. These differences in the behavior of the PGTs in the use of FT during procedures may contribute to differences in FTs seen among attending urologists. Although this is a pilot study identifying PGTs as a significant variable in determining FT during URS, the same outcome measurements could be incorporated into assessment tools used to evaluate technical proficiency of PGTs in performing URS. Future studies with longer duration of endourology rotations with greater number of URS procedures are necessary to determine the number of procedures needed to detect significant decline in the amount of FT during URS.

Conclusion

Urology trainees vary significantly in their use of fluoroscopy during URS. Whether these differences in the behavior of PGTs are intrinsic to themselves or from perioperative factors remains to be clarified. Trainees, male sex, ureteral balloon dilation, residual stones at the end of the procedure together with the use of ureteral access sheaths were the most significant independent predictors of prolonged FT.

Footnotes

Acknowledgments

This work was supported in part by the Canadian Urological Association Scholarship Foundation and the Montreal General Hospital Foundation awards to Sero Andonian.

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

References

International Commission on Radiological Protection. Avoidance of radiation injuries from medical interventional procedures. ICRP Publication 85. Ann ICRP, 2000; 30:7–67.

Yoshinaga

, Mabuchi

, Sigurdson

et al. Cancer risks among radiologists and radiologic technologists: Review of epidemiologic studies. Radiology, 2004; 233:313–321.

Bagley

, Cubler-Goodman

. Radiation exposure during ureteroscopy. J Urol, 1990; 144:1356–1358.

Violette

, Szymanski

, Anidjar

, Andonian

. Factors determining fluoroscopy time during ureteroscopy. J Endourol, 2011; 25:1837–1840.

Ngo

, Macleod

, Rosenstein

et al. Tracking intraoperative fluoroscopy utilization reduces radiation exposure during ureteroscopy. J Endourol, 2011; 25:763–767.

Turney

, Reynard

, Noble

, Keoghane

. Trends in urological stone disease. BJU Int, 2012; 109:1082–1087.

Ferrandino

, Bagrodia

, Pierre

et al. Radiation exposure in the acute and short-term management of urolithiasis at 2 academic centers. J Urol, 2009; 181:668–673.

Fahmy

, Elkoushy

, Andonian

. Effective radiation exposure in evaluation and follow-up of patients with urolithiasis. Urology, 2012; 79:43–47.

Lipkin

, Wang

, Toncheva

et al. Determination of patient radiation dose during ureteroscopic treatment of urolithiasis using a validated model. J Urol, 2012; 187:920–924.

10.

Hellawell

, Mutch

, Thevendran

et al.

Radiation exposure and the urologist: What are the risks?

J Urol, 2005; 174:948–952.

11.

Elkoushy

, Shahrour

, Andonian

. Pulsed fluoroscopy in ureteroscopy and percutaneous nephrolithotomy. Urology, 2012; 79:1230–1235.

12.

Skolarikos

, Gravas

, Laguna

et al. Training in ureteroscopy: A critical appraisal of the literature. BJU Int, 2011; 108:798–805.

13.

Accreditation Council for Graduate Medical Education ACGME Program Requirements for Residency Education in Urology. http://www.acgme.org/acWebsite/RRC_480/480_resLetter2009.pdf. 2012 June 11.

14.

Horowitz

, Yaghmai

, Miller

, Russell

. Will CT ordering practices change if we educate residents about the potential effects of radiation exposure? Experience at a large academic medical center. Acad Radiol, 2011; 18:1447–1452.

15.

McKinstry

, Cameron

, Elton

, Riley

. Leniency and halo effects in marking undergraduate short research projects. BMC Med Educ, 2004; 4:28.

16.

Smilen

, Funai

, Bianco

. Residency selection: Should interviewers be given applicants' board scores? Am J Obstet Gynecol, 2001; 184:508–513.

17.

Vehmas

. Hawthorne effect. Shortening of fluoroscopy times during radiation measurement studies. Br J Radiol, 1997; 70:1053–1055.