Vol 16 No 01 January-February 2019 21 ENDOUROLOGY AND STONE DISEASE Chinese One-shot Dilation versus Sequential Fascial Dilation for Percutaneous Nephrolithotomy: A Feasibility Study and Comparison Xiong Jing1#, Shi Ying2#, Zhang Xiaoping2, Xing Yifei2, Li Wencheng M.D.2* Purpose: Nephrostomy tract creation is a key step to perform a successful percutaneous nephrolithotomy (PCNL). In an attempt to improve the conventional technique of the tract dilation, a Chinese one-shot dilation was devel- oped and compared with the sequential fascial dilation using a retrospective study. Materials and Methods: We retrospectively reviewed medical records of 116 patients who had undergone 116 PCNL in our department from January 2012 to December 2012. The nephrostomy tracts had been created by using Chinese one-shot (one-shot group, 59 cases) or sequential fascial dilation technique (sequential group, 57 cases). Tract creation time, hemorrhage loss, overall renal function, tract dilation failure and major complications were compared between the two groups. Results: The one-shot group had a significantly shorter mean (SD) tract creation time (1.9 ± 0.5 vs 4.5 ± 0.8 min, P < 0.001) and lower mean (SD) decrease in hemoglobin concentration (0.60 ± 0.34 vs 0.69 ± 0.36 g/dL, P = 0.0008) compared to the sequential group, respectively. There were no significant differences in mean (SD) value changes of preoperative and postoperative serum creatinine concentrations (4.7 ± 11.5 vs 4.8 ± 14.8 μmol/L, P = 0.2611) and stone-free rate (86.4% vs 85.9%, P = 0.6145) between the one-shot and sequential group. No tract dilation failure or major complications occurred in both of the groups. Conclusion: This retrospective study demonstrated that the Chinese one-shot dilation technique is as safe and feasible as the conventional sequential fascial dilation. Furthermore, a greater reduction in tract creation time and blood loss was achieved using this technique. Key words: Nephrolithotomy, Percutaneous; Dilation; Kidney Calculi; Complications INTRODUCTION Percutaneous nephrolithotomy (PCNL) is an effec-tive treatment method for large and complex kid- ney stones (1,2) and increasingly applied to moderate stone burdens, particularly for stones in the lower pole calyces(3). The key step of PCNL is nephrostomy tract creation and the most common complications of PCNL, such as renal hemorrhage, tract dilation failure, and collecting system perforation, are all associated with this step(4). Currently, nephrostomy tract creation is per- formed with three classical dilation techniques: Alken metal telescopic dilation(5), Amplatz serial fascial dila- tion(6,7), and high-pressure balloon dilation(8). Alken met- al telescopic dilation and Amplatz serial fascial dilation are sequential dilation methods composed of repeated insertion and withdrawal of incremental dilators, and associated with prolonged tract dilation time, excessive radiation exposure and increased possibility of tract loss and collecting system perforation(9). High-pressure balloon dilation technique, though decreases the num- ber of exchanges, still requires multiple exchanges and time consuming(10), and may cause disruption of dilated 1Department of Nephrology, Union Hospital, Tongji Medical College, Huangzhong University of Science & Technology, Wuhan, China. 2Department of Urology, Union Hospital, Tongji Medical College, Huangzhong University of Science & Tech- nology, Wuhan, China. # These authors contributed equally to this work. *Correspondence: Jiefang Avenue 1277, Wuhan, China. Postal code: 430022. Phone: +8618108626569. Email addresses: liwencheng@hust.edu.cn. Received July 2018 & Accepted December 2018 structures. Moreover, the expensiveness of high-pres- sure balloon precludes it to be commonly used(9,11), and the effect of this technique on blood loss is still in con- troversy(2,12-14). A safe, efficient and easy-to-perform technique for nephrostomy tract creation of PCNL are always high- ly desired by endourologists. Over a decade before, a “one-step” or “one-shot” dilation technique was devel- oped by using a single 25-30 F Amplatz dilator over Alken guidance, which was safe and effective, as well as less time consuming, less blood loss, and less X-ray exposure as reported(15,16). However, this technique still required to exchange the dilator once. Recently, we described a novel one-shot nephrostomy tract dilation technique (Chinese one-shot) using a single fascial di- lator, and the clinical outcome demonstrated that it was safe and highly efficient(17). In this retrospective study, we present our experiences by comparing the outcomes of Chinese one-shot dilation group to those of a conven- tional sequential fascial dilation group. The parameters included tract creation time, hemorrhage loss, overall renal function, tract dilation failure and major compli- cations. We aim to further evaluate the safety and effi- cacy of our Chinese one-shot technique and discuss the possibility of popularizing it. PATIENTS AND METHODS A retrospective review of 116 PCNL cases performed by a single surgeon from January 2012 to December 2012 in our department were performed. Demographic and stone information was presented in Table 1. Stone burden was assessed by preoperative CT, where for each stone the cross-sectional area was calculated by multiplying length by width. The cross-sectional area of all stones was summed and reported as the total burden in case of multiple stones. Fifty-seven consecutive patients who had undergone the sequential fascial dilation technique (the sequential group) were compared to fifty-nine patients who had undergone with the Chinese one-shot technique (the one-shot group). All patients were in accordance with the routine indications of PCNL, and exclusion criteria were patients who required bilateral PCNL or second stage PCNL. Nephrostomy tract creation time, puncture position, renal hemorrhage, blood transfusion rates, overall renal function (preoperative and postoperative serum creatinine concentrations), tract dilation failure, the incidence of complications and stone-free rate were compared between the two groups. The outcomes included tract creation time, hemorrhage, overall renal function, tract dilation failure, stone-free rate and major complications. The tract creation time was defined as the time from the Chiba needle puncture to the direct observation of the collecting system under nephroscope. The hemorrhage loss was evaluated by comparing the last preoperative hemoglobin level with 24-hour postoperative counterpart. Blood transfusion was conducted provided that the cardiopulmonary com- pensation mechanisms were insufficient due to anemia or the postoperative hemoglobin value was less than 80 g/dL. The number and volume of blood transfusion were recorded. The overall renal function assessed by comparing the last preoperative and the 24-hour postop- erative serum creatinine concentration level. Residual fragments <4 mm was considered to be stone-free. The incidence of complications such as tract dilation failure and collecting system perforation was noted. Chinese one-shot dilation After adequate epidural anesthesia was induced, each patient received a single dose of antibiotic intravenous- ly and positioned in the lithotomy position. A 6 F ure- teral catheter was introduced to the ipsilateral renal pel- vis using cystoscopy. After indwelling a Foley catheter, the patient was then repositioned in a prone position. The puncture pathway of the 18 G Chiba needle was strictly through the central point of the target fornix and along the axis of the infundibulum with the guidance of a grayscale ultrasound (US, B-K Medical, Herlev, Den- mark) (Supplementary Figure. 1). The aspiration of urine on removal of the stylet of the needle confirmed the entrance into the collecting system, a super-rigid guidewire (Urovision GmbH, Bad Aibling, Germany) was then introduced under US guidance (Supplementa- ry Figure. 2). Before the needle was removed, the skin and fascia were incised over the puncture site, and then a 22 F pencil-shaped fascial dilator (Create, Yokohama, Japan, Figure. 1) with matched sheath was advanced into collecting system over super-rigid guidewire di- rectly. Rotating the dilator with angular shearing force may facilitated the passage through the renal capsule into the renal collecting system. The appearance of break-through feeling or aspiration of urine from the dilator indicated the matched sheath was advanced smoothly into the collecting system, and then the dilator was removed while holding the sheath in position for the next operation (Figure. 2). All steps including nee- dle puncture, tract dilation and sheath placement were performed without fluoroscopic control in all patients. Table 1. Patient demographics and stone features One-shot group n: 59 Sequential group n:57 P value Age (y) Mean ± SD 46.7±12.3 47.4 ± 10.6 0.6076 Range 20-77 24-69 Gender, n (%) Male 36 (61.0) 37 (64.9) 0.6641 Female 23 (39.0) 20 (35.1) Stone side, n (%) Left kidney 32 (54.2) 35 (61.4) 0.4347 Right kidney 27 (45.8) 22 (38.6) Stone location, n (%) 0.2312 Pelvis 23 (39.0) 17 (29.8) Upper segment of ureter 5 (8.5) 2 (3.5) Middle calyceal group 1 (1.7) 4 (7.0) Lower calyceal group 6 (10.2) 3 (5.3) Pelvis and calyx 24 (40.7) 31 (54.4) Stone burden (cm) 0.5169 Mean ± SD 4.9 ± 3.2 4.8 ± 3.9 Range 1.9-10.5 1.6-11.4 Figure 1. The detail of the special design of Creator dilator. As pointed out by the red square, Creator dilator (the upper) has a sharper tip and longer tapered end compared to Amplatz dilator (the lower) (2.5 cm vs. 1.5 cm). Chinese one-shot dilation for percutaneous access-Jing et al. Endourology and Stone Diseases 22 Vol 16 No 01 January-February 2019 23 Stone treatment and removal were performed in a conventional manner. A 20.8 F nephroscope (Wolf, Mainburg, Germany) was introduced through the 22 F sheath and stones were disintegrated using ultrasonic/ pneumatic lithotripters (Swiss Lithoclast, Nyon, Swit- zerland). At the end of the procedure, residual stones were detected by abdominal radiography (Siemens, Muenchen, Germany) or ultrasound in case of radiolu- cent stones. After complete clearance was confirmed, a 6 F double-J stent was introduced antegradely, fol- lowed by a 20 F nephrostomy tube placement. After the clearance of hematuria (usually within 12 to 48 h), the urethral catheter was removed and the nephrostomy tube was clamped. If neither fever nor urine leakage oc- curred, the nephrostomy tube was removed 12-24 hours later after the clamping. Conventional sequential fascial dilation Using the conventional technique, the access tract was dilated with a series of pencil-shaped fascial dilators (Create, Yokohama, Japan) from 8 F to 22 F in a mul- ti-increment manner, overlapping at 2 F intervals, over the super-rigid guidewire. After the correct position of 22 F dilator (with matched sheath) was verified, the matched sheath was introduced and retained in the col- lecting system. Statistical Data were analyzed using SAS 9.13 for Windows (SAS Institute Inc, Cary, NC), whereby statistical signifi- cance was determined at the level of α = 0.05. Univar- iate descriptive statistics included mean and standard deviation (mean ± SD) for quantitative variables and frequency and percentage for qualitative variables. Student’s t test or Mann-Whitney U test was applied to compare one-shot dilation with sequential fascial di- lation for quantitative variables, and Chi-square test or Fisher’s exact test for qualitative variables. RESULTS As shown in Table 1, there were no significant differ- ences between the one-shot and sequential group in demographic data such as age, gender, or clinical data such as stone location and burden. Nine patients in the one-shot group and seven in the sequential group had a history of ipsilateral open nephrolithotomy. The intraoperative and postoperative variables of clin- ical data in both groups were summarized in Table 2. Successful access was established in all patients of both groups. The one-shot technique resulted in a significant reduction in mean tract creation time (1.9 ± 0.5 min vs 4.5 ± 0.8 min, P < 0.0001) compared to the convention- al technique. Of note, a statistically significant drop in mean postoperative hemoglobin value was observed in the sequential group (0.60 ± 0.34 g/dL vs 0.69 ± 0.36 g/dL, P = 0.0008). However, none of these patient was administered blood transfusion intraoperatively or post- operatively. There were no significant difference in se- rum creatine concentration between the two groups (4.7 ± 11.5μmol/L vs 4.8 ± 14.8 μmol/L, P = 0.2611) and stone-free rate (86.4% vs 85.9%, P = 0.6145). No tract dilation failure occurred in both of the groups. Notably, there were three cases (two cases in one-shot group and one in the sequential group) whose kidney rotated even when the 18 G needle touched the renal capsule surface. For those patients, target calices were punctured successfully with prompt action, and then the nephrostomy tracts of all the 3 cases were dilated successfully. Furthermore, there are no major compli- cations such as adjacent organ injury, major vascular injury or hydrothorax occurred in all cases during or after the surgery. DISCUSSION The success and safety of PCNL are directly influenced by the quality of the access(18). Great efforts have been made to improve the methods for establishing renal access over decades. In 1991, Travis et al(10) first de- scribed a single-increment dilation method in a canine model, and the result demonstrated that this technique was as safe as conventional dilation techniques with minimal hemorrhage or parenchymal damage either im- mediately or at 6 weeks. Fattini et al(15) later reported a novel “one-shot” method to dilate the nephrostomy ac- cess for percutaneous lithotripsy. They first introduced Alken guide or 8 F Amplatz dilator over the guidewire, and then a single 25 F or 30 F Amplatz dilator was ad- vanced, followed by a 34 F sheath. Their results showed that this “one-shot” technique was feasible and effective and also significantly reduced X-ray exposure during Table 2. Comparison of two groups: the outcomes during and after surgery of 116 cases One-shot group n: 59 Sequential group n:57 P value Tract creation time (min) Mean ± SD 1.9 ± 0.5 4.5 ± 0.8 < 0.0001 Range 1.5-3 3.5-6 Successful access, n (%) 59 (100%) 57 (100%) Hemoglobin value (g/dL), mean ± SD Preoperative 133.7 ± 16.3 131.6 ± 16.5 0.6405 Postoperative 127.5 ± 15.7 123.5 ± 15.8 0.5917 Decrease after operation 0.60 ± 0.34 0.69 ± 0.36 0.0008 Serum creatine concentration (μmol/L), mean ± SD Preoperative 85.4 ± 42.7 78.4 ± 21.6 0.6164 Postoperative 80.6 ± 39.4 73.2 ± 18.4 0.4759 Increase after operation 4.7 ± 11.5 4.8 ± 14.8 0.2611 Stone-free rate 51 (86.4%) 49 (85.9%) 0.6145 Adjacent organ injury 0 0 Major vascular injury 0 0 Collecting system perforation during tract dilation procedure 0 0 Dilation failure 0 0 Transfusion requirement 0 0 Angiography requirement 0 0 Chinese one-shot dilation for percutaneous access-Jing et al. the dilation of the tract. The safety and efficacy of this method were subsequently verified by other urological centers in adult patients(9,11,16,19-23). As distinct from the one-shot dilation technique described by Fattini(15) and Falahatkar(16), we established the renal access with a sin- gle 22 F fascial dilator passing over the J-tip super-rigid guidewire into the collecting system directly(17). In this study, the retrospective data strongly demonstrated that our Chinese one-shot dilation technique was as safe and feasible as the conventional sequential fascial dilation, and greater reductions in tract creation time and blood loss were achieved using this technique as well. On the basis of these results, we later innovated our Chinese one-shot dilation technique by applying stimulated diu- resis instead of retrograde ureteral catheter placement, which is more time-saving(17). Dilation failure is one of the most frequent complica- tions of PCNL, especially when more exchanges or passes were needed during dilation with sequential di- lators(3). The cause could be ascribed to the presence of excessive fibrotic scarring from previous open surgery or displacement of guidewire. It was documented that the tract dilation failure rates were 6% (4/67) in Am- platz group and 1.7% (2/121) in Alken group, respec- tively(4). Ozok et al(4) reported that excessive scarring, renal hypermobility and insufficient insertion of the J-tip rigid guidewire into the collecting system resulted in dilation failure when using Amplatz serial dilation. The scarring and renal hypermobility also attributed to dilation failure of one-shot dilation technique and used to be regarded as real contraindications to one-shot di- lation(15). However, Falahatkar et al(16) reported that the successful access rate of one-shot dilation technique was 87.0% (20/23) in patients who had past history of ipsilateral open stone surgery. Amjadi(19) and Sofikerim (24) also confirmed that one-step dilation was feasible in patients with previous open nephrolithotomy as well as Amplatz serial fascial dilation. In our study, we chose a special designed dilator with sharper tip and longer tapered end compared to Am- platz dilator (Figure.1), and applied it in both of the groups. The successful access rate was 100% in either group, including sixteen patients who had previous his- tory of ipsilateral open nephrolithotomy (nine in one- shot group and seven in the sequential group). More- over, the data analysis revealed a significant reduction in mean tract creation time in one-shot group (1.9±0.5 min vs 4.5 ± 0.8 min, P < 0.0001) compared to the con- ventional technique, since the operating procedure was remarkably simplified in one-shot technique. The renal hypermobility often causes guidewire displacement. We encountered three cases (two in one-shot group and one in sequential group) whose kidney rotated along the long axis even when the 18 G Chiba needle touched the renal capsule surface, and we managed to create the nephrostomy tract successfully in all of the cases. There are two key points that should be noticed under cer- tain situations mentioned above. First, the super-rigid guidewire should be inserted as deep as possible, which ensures the super-rigid part of the guidewire is actually located in the collecting system. Second, do remind that the super-rigid guidewire should be pushed gently by the assistant all the time, which allows the movement of the guidewire is synchronous with that of the kidney during the dilation procedure. Renal hemorrhage is the most common complication of PCNL and related to sheath size, aggressive manip- ulation, stone burden and operating time(2,25,26). It was reported that nephrostomy tract dilation procedure accounted for half of the total blood loss in PCNL(27). The correct needle puncture route and proper dilation technique are critical factors that may affect, even de- cide, the bleeding and transfusion rates. Practice indi- cates that renal hemorrhage can be best avoided when the puncture and dilation route strictly goes through the center point of the fornix of the target calyx and along the axis of the infundibulum(17,28). During the process of stone disintegration, a cautious and minimal an- gulation of the working sheath and nephroscope may minimize the risk of calyceal neck laceration and con- sequent renal bleeding. In the present study, the mean hemoglobin decline 24 h after surgery in one-shot and sequential group was 0.60 ± 0.34 g/dL and 0.69 ± 0.36 g/dL, respectively, which clearly indicated that the one- shot technique was associated with less blood loss (P = 0.0008). The fascial sequential dilators system com- prised 8 semi-rigid dilators which increased at a 2 F in- terval from 8 F to 22 F. During the tract dilation, every exchange of serial dilators would cause hemorrhage due to disappearance of tamponade effect on the small ves- sels. On the contrary, there is no dilator exchange or in- crement happened during the tract creation process with one-shot dilation technique. Employment of a single 22F fascial dilator tamponades the access tract, impos- es consecutive pressure on the potential impaired small vessels throughout the entire dilation procedure, and therefore reduces blood loss. Ozok et al(4) reported that mean hemoglobin decrease was 1.5 ± 1.2 g/dL in Am- platz group with mean stone surface area 673.4 ± 466.9 mm2. The Clinical Research Office of the Endouro- logical Society Percutaneous Nephrolithotomy Study Group concluded that working sheath was associated with increased transfusion rates, with rates of 1.1% for the smallest sheath and 12.0% for the largest sheath(2). One of the reasons account for the different hemoglobin decrease values between our study and Ozok’s might be the different size of working sheath used in the two studies (22 F vs 30 F). Figure 2. The dilator is removed and the sheath kept in place for the next nephroscopic operation when the sheath is advanced smoothly into the collecting system. Chinese one-shot dilation for percutaneous access-Jing et al. Endourology and Stone Diseases 24 Vol 16 No 01 January-February 2019 25 CONCLUSIONS We developed a novel, safer and more efficient Chinese one-shot tract dilation technique for PCNL. In contrast to the conventional sequential dilation technique, the major advantages of this solution are simpler without any dilator exchanges, less time-consuming and less re- nal hemorrhage. REFERENCES 1. Miller NL, Lingeman JE. Management of kidney stones. Bmj 2007; 334:468-72. 2. Yamaguchi A, Skolarikos A, Buchholz NP, et al. Operating times and bleeding complications in percutaneous nephrolithotomy: a comparison of tract dilation methods in 5,537 patients in the Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study. J Endourol 2011; 25:933-9. 3. Antonelli JA, Pearle MS. Advances in percutaneous nephrolithotomy. Urol Clin North Am 2013; 40:99-113. 4. 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