|Year : 2020 | Volume
| Issue : 2 | Page : 62-67
Comparative study of simultaneous supine percutaneous nephrolithotomy with ureteroscopic lithotripsy and semi-rigid ureteroscopic lithotripsy in the management of large proximal ureteral calculi
Yu-Chen Chen1, Hao-Wei Chen1, Wen-Jeng Wu1, Ching-Chia Li1, Yung-Shun Juan2, Yii-Her Chou3, HungLung Ke1, Chun-Nung Huang2, Yung-Chin Lee3, Ming-Chen Paul Shih4, Sheng-Chen Wen3, Shih-I Tseng3, Tsung-Yi Huang3
1 Department of Urology, Kaohsiung Medical University Hospital; Department of Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
2 Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung Medical University; Department of Urology, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung, Taiwan
3 Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
4 Department of Radiology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
|Date of Submission||26-Sep-2019|
|Date of Decision||28-Dec-2019|
|Date of Acceptance||31-Dec-2019|
|Date of Web Publication||25-Apr-2020|
Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan. No. 100, Tzyou 1st Road, Kaohsiung 807
Source of Support: None, Conflict of Interest: None
Purpose: The aim of the study was to compare the outcomes of simultaneous supine percutaneous nephrolithotomy (sPCNL) with semi-rigid ureteroscopic lithotripsy (SR-URSL) (Group A) and SR-URSL (Group B) for treating large proximal ureteral calculus. Materials and Methods: Between January 2015 and April 2019, all patients with large proximal ureteral stones (≥10 mm) who underwent simultaneous sPCNL with SR-URSL or SR-URSL at three medical centers were retrospectively included. Two surgical options were provided based on patients and doctors' decision. The intraoperative and postoperative results, including operating time, hospital stay, need for auxiliary procedures, and complications, were compared between the two groups. Stone-free clearance was defined as the absence of fragments or a single fragment of ≤4 mm on standard radiography 1 month after surgery. Results: A total of 38 and 27 patients were included in Groups A and B, respectively. The mean stone size was 21 mm and 18.2 mm and stone-free rate (SFR) was 97% and 33% in Groups A and B, respectively. Larger ureteral stones (P < 0.001), longer operation time (P < 0.001), prolonged hospitalization (P < 0.001), higher SFR (P < 0.001), and less patients requiring auxiliary procedures (P < 0.001) were observed in Group A. No significant difference regarding complications was observed between groups (P = 0.1). Conclusion: Simultaneous sPCNL with SR-URSL is a feasible and effective treatment for large proximal ureteral stones. Even though larger stone size was observed, simultaneous sPCNL with SR-URSL results in significantly higher SFR and reduced need for auxiliary procedures, without major complications, compared to SR-URSL alone. More clinical studies are required to confirm the outcomes of the present study.
Keywords: Endoscopes, percutaneous nephroscopy, supine position, upper ureteral stone, ureteroscopic lithotripsy
|How to cite this article:|
Chen YC, Chen HW, Wu WJ, Li CC, Juan YS, Chou YH, Ke H, Huang CN, Lee YC, Shih MCP, Wen SC, Tseng SI, Huang TY. Comparative study of simultaneous supine percutaneous nephrolithotomy with ureteroscopic lithotripsy and semi-rigid ureteroscopic lithotripsy in the management of large proximal ureteral calculi. Urol Sci 2020;31:62-7
|How to cite this URL:|
Chen YC, Chen HW, Wu WJ, Li CC, Juan YS, Chou YH, Ke H, Huang CN, Lee YC, Shih MCP, Wen SC, Tseng SI, Huang TY. Comparative study of simultaneous supine percutaneous nephrolithotomy with ureteroscopic lithotripsy and semi-rigid ureteroscopic lithotripsy in the management of large proximal ureteral calculi. Urol Sci [serial online] 2020 [cited 2020 May 24];31:62-7. Available from: http://www.e-urol-sci.com/text.asp?2020/31/2/62/283252
| Introduction|| |
Ureteroscopic lithotripsy (URSL) and extracorporeal shock wave lithotripsy (ESWL) were proposed by the European Urological Association (EAU) and American Urological Association guidelines as first-line treatments for managing proximal ureteral calculi., However, ESWL has a poor stone-free outcome rate and requires multiple sessions in cases of upper ureteral stones ≥10 mm. URSL, when approaching large proximal ureteral stones, is often associated with a long operative time, the migration of stones or fragments, and further auxiliary procedures, such as ESWL and flexible ureteroscopy (URS). According to EAU guidelines, percutaneous nephrolithotomy (PCNL) is considered a treatment alternative in cases when ESWL and URSL were highly suspected to fail, especially large impacted proximal ureteral calculi, but bleeding is commonly reported with a 7% need for transfusion.
Since each technique has its own limitations, large proximal ureteral stones are challenging to treat, and optimal management of large proximal ureteral stones (≥10 mm) remains controversial. We previously reported a preliminary experience describing an effective method of simultaneous supine percutaneous nephrolithotomy (sPCNL) with semi-rigid (SR)-URSL in the Galdakao-modified supine Valdivia (GMSV) position to treat large proximal ureteral calculi. Hereby, the aim of this article is to further compare the surgical outcomes of simultaneous sPCNL with SR-URSL and SR-URSL for treating large proximal ureteral calculus.
| Patients and Methods|| |
Study population and study design
Between January 2015 and April 2019, all patients with large proximal ureteral stones (≥10 mm) who underwent sPCNL with SR-URSL and SR-URSL at the Kaohsiung Medical University Hospital, Kaohsiung Municipal Siaogang Hospital, and Kaohsiung Municipal Ta-Tung Hospital were retrospectively reviewed.
Inclusion and exclusion criteria
The inclusion criteria were the presence of a single stone in the proximal ureter (defined as the ureteral stone located between the ureteropelvic junction and the lower border of the fourth lumbar vertebra), stone major length ≥10 mm, and radio-opaque densities on kidney–ureter–bladder (KUB) plain film (KUB; in consideration of follow-up measurements).
The exclusion criteria were patients with a large proximal ureteral calculus combined with other renal, contralateral ureteral, or bladder stones. Patients with untreated urinary tract infections, pregnancy, potential malignant renal tumors, or bleeding tendency or those who had an abnormal interposition of visceral organs (retrorenal colon) were excluded. Patients who could not be placed in the GMSV position due to bone deformity or muscle contracture were also excluded.
Two surgical options (simultaneous sPCNL with SR-URSL [Group A] or SR-URSL [Group B]) were provided based on patients (cosmetic outcomes and acceptance of operative wound in flank area in Group A) and doctors' decision. Procedural details and possible outcomes including residual stones and double J stent placement were explained. Informed consent was obtained from all patients. Participation in either group was at the discretion of the patients and surgeons. The study was approved by the institutional review board of Kaohsiung Medical University Hospital (ID: KMUHIRB-E (I)-20170273).
Surgical procedure of simultaneous supine percutaneous nephrolithotomy with semi-rigid ureteroscopic lithotripsy
One day before the operation, renal puncture was performed with an 18G Chiba biopsy needle, and a Radifocus® hydrophilic guidewire was introduced into the targeted calyx under fluoroscopic guidance by a radiologist. On the operation day, the patient was placed in the GMSV position, with one leg in extension ipsilateral to the stone and the other in flexion. Two surgeons simultaneously performed the sPCNL and retrograde SR-URSL. After tract dilatation with an UltraxxTM nephrostomy balloon through a Radifocus® hydrophilic guidewire, a 30 French (Fr) Amplatz sheath was introduced. One surgeon placed a 26 Fr nephroscope (Richard Wolf, Knittlingen, Germany) at the ureteropelvic junction and waited for the other surgeon to approach the proximal ureteral stone in a retrograde manner with a 6 Fr SR ureteroscope (Richard Wolf, Knittlingen, Germany). Ureteral stones were disintegrated by a holmium: yttrium aluminum garnet (YAG) laser by SR URS and were then pushed retrogradely and removed in an anterograde manner by forceps under nephroscopy through an Amplatz sheath. Baskets were unnecessary during all procedures. At the end of the operation, a double J stent was positioned, which was subsequently removed as an outpatient procedure 2–4 weeks postoperatively depending on the outcome of stone clearance. We routinely placed the hemostatic compressed sponge (Gelfoam®) through the percutaneous nephrostomy (PCN) tract instead of the nephrostomy tube. We monitored all the patients' vital sign. Laboratory data were checked if unstable hemodynamic status appeared.
Surgical procedure of semi-rigid ureteroscopic lithotripsy
We used 6 Fr or 8 Fr Storz SR ureteroscopes with a holmium: YAG laser or lithoclast. The usage of a basket was at the surgeon's discretion. The double J stent was placed in all patients.
Data analysis, outcome assessment, and postoperative care
Demographic data (age, body mass index [BMI], sex, and estimated glomerular filtration rate [eGFR]), stone laterality, stone size, operative duration, postoperative hospitalization, stone-free rate (SFR), and complication rates were compared between groups. Complications were graded according to the modified Clavien classification. The postoperative hematuria was defined as the persistent gross hematuria 8 h after the operation. The operating time in Group A was defined as the time between PCN tract dilatation and the end of the operation (Foley insertion), which excluded the time required for anesthesia and patient positioning. The operating time in Group B was defined as the time of the start of URS and the end of the operation (Foley insertion), which excluded the time required for anesthesia, patient positioning, and cystoscopy. Continuous bladder irrigation was administered for one night if gross hematuria was present, and the Foley catheter was removed if there was no evidence of hematuria. KUB radiography was used to confirm postoperative stone clearance. We discharged the patient if there was no evidence of persistent pain, fever, or anemia. All patients were under urologic outpatient clinic follow-up observation after discharge. The primary outcome was stone-free clearance, which was defined as the absence of fragments or a single fragment of ≤4 mm on standard radiography at the 1-month follow-up examination.
Statistical analysis was performed using the Statistical Package for Social Sciences version 20.0 software (SPSS Inc., Chicago, IL, USA). Student's t-test and Chi-squared test were used for statistical analysis. P < 0.05 was designated as statistically significant.
| Results|| |
A total of 65 consecutive patients with a single large proximal ureteral calculus were included (38 patients in Group A; 27 patients in Group B). Patient demographics and stone characteristics are described in [Table 1]. There were 29 (76%) males and 9 (24%) females in Group A, and 24 (88%) males and 3 (12%) females in Group B (P = 0.3). The mean patient age was 55.9 and 60.3 years in Groups A and B, respectively, with no statistical significance (P = 0.2). The mean stone size was significantly larger in Group A (21 mm) compared to Group B (18.2 mm; P < 0.001); however, no other significant difference was observed regarding BMI, preoperatively eGFR, and stone side.
|Table 1: Patient demographics and clinical data in Group A (simultaneous supine percutaneous nephrolithotomy with ureterolithotripsy) and Group B (semi-rigid ureteroscopic lithotripsy)|
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Intraoperative and postoperative outcomes are reported in [Table 2]. There were 37 (97%) and 9 (33%) patients who achieved postoperative stone-free status in Groups A and B, respectively. Significantly higher SFR (P < 0.001), less patients requiring auxiliary procedures (P < 0.001), but longer operation time (P < 0.001), and prolonged hospitalization (P < 0.001) were observed in Group A. There were 10 (26.3%) modified Clavien Grade I (hematuria or flank pain renal colic) and 5 (13.2%) Grade II (fever treated with intravenous antibiotics during prolonged hospitalization) complications in Group A; 1 (3%) modified Clavien Grade I (hematuria), 3 (11%) Grade II (fever with intravenous antibiotic treatment needed), and 3 (11.1%) Grade III (one patient's double J stent failed to be removed due to steinstrasse, treated with secondary URSL; the other two patients suffered from postoperative ureteral stricture with persistent hydronephrosis and fever after stent removal, treated with further URS and double J stent insertion) complications in Group B. Overall, no significant difference regarding complications was observed between groups (P = 0.1). No blood transfusions were needed in this series, and no urinary tract perforation or adjacent organ injury occurred in either group.
|Table 2: Intraoperative parameters and postoperative outcomes in Group A (simultaneous supine percutaneous nephrolithotomy with ureterolithotripsy) and Group B (semi-rigid ureteroscopic lithotripsy)|
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| Discussion|| |
There are many treatment options for large proximal ureteral calculi (defined as ≥10 mm, based on previous literature), including ESWL, URSL, PCNL, and ureterolithotomy. Since each method has its pros and cons, the best treatment option is still controversial. ESWL has the advantage of being a less invasive procedure with SFR reported as high as 88%. However, for upper ureteral stones ≥10 mm, stone clearance rates fell to 42%–59%,, possibly because the larger stones are usually impacted and wrapped around the ureteral polyp, which causes ESWL to often be ineffective. SR-URSL was reported to have a wide range of success depending on the stone size. Sofer et al. reported a 97% SFR in upper ureteral stones with a mean stone size of 11.3 mm; Tunc et al. reported a 60% SFR with a mean stone size of 12.87 mm; Galal et al. reported a 68% success rate with a mean stone size of 13.5 mm. In our study, although the SFR in the URSL group was lower compared to the data reported in the literature, the mean stone size was 18.2 mm and the largest ureteral stone in the URSL group was 47 mm, which is much larger than those in the literature. According to a previous paper by Hong and Park, the success rate decreased with stone size ≥10 mm in URSL, which may explain the lower SFR observed in our study. Ureterolithotomy is also an alternative method for treating large ureteral stones but is more invasive and associated with greater postoperative morbidity.
According to EAU guidelines, PCNL can be considered as a treatment alternative for large impacted proximal ureteral stones but with a high risk of transfusion. sPCNL was first reported by Valdivia-Uría, who modified PCNL to no longer be exclusively performed in the prone position. sPCNL has the advantage of being more comfortable for the anesthetist, especially in obese or high-risk anesthesia patients, compared to prone PCNL. sPCNL was then further improved by Ibarluzea, opening the era of endoscopic-combined intrarenal surgery (ECIRS). Although ECIRS, with the simultaneous contribution of PCNL and flexible URS, has the advantage of aiming at the one-step and one-access resolution of urolithiasis along the whole urinary tract, it is not commonly available worldwide due to the high cost and skill dependency of flexible URS. Hence, we first proposed a novel technique that uses simultaneous sPCNL with SR-URSL in the management of urolithiasis with the advantage of durability and affordability of SR URSL., However, these study designs are only retrospective, which provides a low level of evidence. We hereby conducted this retrospective comparative study between simultaneous sPCNL with SR-URSL and SR-URSL.
Using this approach to manage large upper ureteral stones, it could create an open low-pressure system that reduces the absorption of irrigation fluid into the circulation. The proximal ureteral stone could be pushed back to the renal pelvis and retrieved by forceps with a nephroscope through an Amplatz sheath during a single procedure, without the need for baskets, reducing the risk of ureteral injury causing ureteral stricture in the future. Furthermore, during withdrawal of the URS, the ureter and bladder could be evaluated for any residual stone fragments or blood clots.
Indeed, the development of a postoperative ureteral stricture is one of the serious complications that may occur after URSL. Preminger et al. reported a 3%–6% postoperative stricture rate, while Bader et al. reported a 0%–0.2% postoperative stricture rate. It is possible that the improvements in surgical technology and technique are responsible for this dramatic reduction. In our study, the postoperative stricture rate in Group B is 0.07%. Although the cause of a ureteral stricture is likely multifactorial, impacted large ureter stone, defined by the inability to pass a wire or catheter beyond the stone or stones that have been present and not moved for 2 months or more, was reported to be associated with a 24% postoperative stricture rate, and ureteral perforation during URS was reported to increase the risk of stricture. To reduce the risk for stricture, care should be taken during the URS procedure, especially in the management of large ureter stones.
Regrading the complications of PCNL, hemorrhage is the most significant complication, with transfusion rates reported to be from <1% to 10%. A multi-institution study of more than 5000 cases reported an overall transfusion rate of 5.7%. Significant bleeding usually requires cessation of the procedure and the placement of a nephrostomy tube. In our study, at the end of the operation in Group A, we routinely placed the hemostatic compressed sponge through the PCN tract instead of the nephrostomy tube. We closely monitored all the patients' vital sign and checked the lab data if necessary. In our series, no blood transfusion was administered.
There were no significant differences in baseline demographic data between groups, except stone size in our study. Although significantly larger ureteral stones were found in Group A, the SFR was also significantly higher in Group A (P < 0.001). The possible reasons that longer operative time was observed in Group A were as follows: (1) the goal of simultaneous sPCNL with SR-URSL is complete or nearly complete clearance of stone material under fluoroscopy; therefore, it took more time to grasp the stone fragments and (2) due to the fact that once the stone fragments migrated into the renal pelvis, it is nearly impossible to grasp the fragments and the operation may come to the end, which also caused the lower SFR in Group B. In addition, although no significant difference was observed in complication rates between groups (P = 0.1), higher gross hematuria and flank renal colic pain and rates of postoperative fever, which required intravenous antibiotics, were found in Group A. Notably, no higher than Grade II complications occurred in Group A, and most of the complications were gross hematuria and flank renal colic pain, which could be subsided by supportive care, while ureteral stricture and steinstrasse, which required secondary URS/URSL, occurred in Group B. Compared to Group A, there were significantly more patients who required auxiliary procedures in Group B (P < 0.001), with 8 (29.6%) patients treated with auxiliary ESWL due to stone migration, which was possibly because of the increased irrigation to improve the visibility during fragmentation, and 4 (14.8%) patients treated with auxiliary URSL. Those facts in addition to (i) lack of major complications, (ii) significantly higher SFR, even with significantly larger ureteral stone, and (iii) significantly lower frequency of auxiliary procedure requirement suggested that simultaneous sPCNL with SR-URSL could be considered a safe and effective surgical option when treating large proximal ureteral stones.
To the best of our knowledge, this is the first study comparing simultaneous sPCNL with SR-URSL and SR-URSL in the treatment of a single large proximal ureteral stone. Based on our experience, SR-URSL has significantly lower SFR and is associated with a higher frequency of auxiliary procedure requirement in the treatment of proximal ureteral stones ≥10 mm, which suggests that the explanation to patients of the possibility of further auxiliary procedures is necessary when choosing SR-URSL in these cases.
Our study has some limitations. A few number of cases were included in the study, and our design was retrospective. Participation in either group was determined by the patients and surgeons instead of randomization. Therefore, further randomized controlled studies are required to confirm the outcomes of the present study.
| Conclusion|| |
Compared with URSL, although simultaneous sPCNL with SR-URSL has significantly longer operative time and hospitalization, it also has significantly higher SFRs, lower frequency of auxiliary procedure requirement, and no difference in complication rate in the treatment of large proximal ureteral stones. Based on these clinical data, we believe that simultaneous sPCNL with SR-URSL presents a safe and effective treatment option for large proximal ureteral stones; however, further randomized controlled studies are required to confirm these outcomes.
I am very grateful for the cooperation and interest of all authors.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Assimos D, Krambeck A, Miller NL, Monga M, Murad MH, Nelson CP, et al
. Surgical management of stones: American Urological Association/Endourological Society Guideline, PART I. J Urol 2016;196:1153-60.
Türk C, Petřík A, Sarica K, Seitz C, Skolarikos A, Straub M, et al
. EAU guidelines on interventional treatment for urolithiasis. Eur Urol 2016;69:475-82.
Preminger GM, Tiselius HG, Assimos DG, Alken P, Buck C, Gallucci M, et al
. EAU/AUA nephrolithiasis guideline panel. J Urol. 2007;178:2418-34.
Seitz C, Desai M, Häcker A, Hakenberg OW, Liatsikos E, Nagele U, et al
. Incidence, prevention, and management of complications following percutaneous nephrolitholapaxy. Eur Urol 2012;61:146-58.
Chen YC, Chen HW, Juan YS, Lo IS, Shih MP, Wu WJ, et al
. Management of large proximal ureteral calculi: A three-year multicenter experience of simultaneous supine percutaneous nephrolithotomy and retrograde ureterolithotripsy. Urol J 2019;16:433-8.
Scoffone CM, Cracco CM, Cossu M, Grande S, Poggio M, Scarpa RM. Endoscopic combined intrarenal surgery in Galdakao-modified supine Valdivia position: A new standard for percutaneous nephrolithotomy? Eur Urol 2008;54:1393-403.
Khazaali M, Khazaeli D, Moombeini H, Jafari-Samim J. Supine ultrasound-guided percutaneous nephrolithotomy with retrograde semi-rigid ureteroscopic guidwire retrieval: Description of an evolved technique. Urol J 2017;14:5038-42.
Tefekli A, Ali Karadag M, Tepeler K, Sari E, Berberoglu Y, Baykal M, et al
. Classification of percutaneous nephrolithotomy complications using the modified clavien grading system: Looking for a standard. Eur Urol 2008;53:184-90.
Karami H, Mazloomfard MM, Lotfi B, Alizadeh A, Javanmard B. Ultrasonography-guided PNL in comparison with laparoscopic ureterolithotomy in the management of large proximal ureteral stone. Int Braz J Urol 2013;39:22-8.
Segura JW, Preminger GM, Assimos DG, Dretler SP, Kahn RI, Lingeman JE, et al
. Ureteral stones clinical guidelines panel summary report on the management of ureteral calculi. The American Urological Association. J Urol 1997;158:1915-21.
White W, Klein F. Five-year clinical experience with the Dornier delta lithotriptor. Urology 2006;68:28-32.
Park H, Park M, Park T. Two-year experience with ureteral stones: Extracorporeal shockwave lithotripsy v ureteroscopic manipulation. J Endourol 1998;12:501-4.
Sofer M, Watterson JD, Wollin TA, Nott L, Razvi H, Denstedt JD. Holmium: YAG laser lithotripsy for upper urinary tract calculi in 598 patients. J Urol 2002;167:31-4.
Tunc L, Kupeli B, Senocak C, Alkibay T, Sözen S, Karaoglan U, et al
. Pneumatic lithotripsy for large ureteral stones: Is it the first line treatment? Int Urol Nephrol 2007;39:759-64.
Galal EM, Anwar AZ, El-Bab TK, Abdelhamid AM. Retrospective comparative study of rigid and flexible ureteroscopy for treatment of proximal ureteral stones. Int Braz J Urol 2016;42:967-72.
Hong YK, Park DS. Ureteroscopic lithotripsy using Swiss Lithoclast for treatment of ureteral calculi: 12-years experience. J Korean Med Sci 2009;24:690-4.
Liu Y, Zhou Z, Xia A, Dai H, Guo L, Zheng J. Clinical observation of different minimally invasive surgeries for the treatment of impacted upper ureteral calculi. Pak J Med Sci 2013;29:1358-62.
Valdivia Uría JG, Valle Gerhold J, López López JA, Villarroya Rodriguez S, Ambroj Navarro C, Ramirez Fabián M, et al
. Technique and complications of percutaneous nephroscopy: Experience with 557 patients in the supine position. J Urol 1998;160:1975-8.
Manohar T, Jain P, Desai M. Supine percutaneous nephrolithotomy: Effective approach to high-risk and morbidly obese patients. J Endourol 2007;21:44-9.
Ibarluzea G, Scoffone CM, Cracco CM, Poggio M, Porpiglia F, Terrone C, et al
. Supine Valdivia and modified lithotomy position for simultaneous anterograde and retrograde endourological access. BJU Int 2007;100:233-6.
Cracco CM, Scoffone CM. ECIRS (Endoscopic Combined Intrarenal Surgery) in the Galdakao-modified supine Valdivia position: A new life for percutaneous surgery? World J Urol 2011;29:821-7.
Huang TY, Feng KM, Lo IS. Percutaneous Nephrolithotomy: Update, Trends, and Future Directions for Simultaneous Supine Percutaneous Nephrolithotomy and Retrograde Ureterolithotripsy in the Galdakao-modified Supine Valdivia Position for Large Proximal Ureteral Calculi. Eur Urol 2017;71:837-8.
Preminger GM, Tiselius HG, Assimos DG, Alken P, Buck C, Gallucci M, et al
. 2007 guideline for the management of ureteral calculi. J Urol 2007;178:2418-34.
Bader MJ, Eisner B, Porpiglia F, Preminger GM, Tiselius HG. Contemporary management of ureteral stones. Eur Urol 2012;61:764-72.
Roberts WW, Cadeddu JA, Micali S, Kavoussi LR, Moore RG. Ureteral stricture formation after removal of impacted calculi. J Urol 1998;159:723-6.
Meng MV, Freise CE, Stoller ML. Expanded experience with laparoscopic nephrectomy and autotransplantation for severe ureteral injury. J Urol 2003;169:1363-7.
Yamaguchi A, Skolarikos A, Buchholz NP, Chomón GB, Grasso M, Saba P, et al
. Operating times and bleeding complications in percutaneous nephrolithotomy: A comparison of tract dilation methods in 5537 patients in the Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study. J Endourol 2011;25:933-9.
[Table 1], [Table 2]