Original Article Evaluation of success rate of percutaneous ...0, respectively). The modified GSS...

Int J Clin Exp Med 2018;11(4):3175-3185www.ijcem.com /ISSN:1940-5901/IJCEM0065087

Original ArticleEvaluation of success rate of percutaneous nephrolithotomy with a modified Guy’s stone score system

Leihua Cao1, Weimin Chen2, Qi Chen3, Jinhua Wu4, Fengui Leng5, Yu Zeng6

1Department of Urology, The Third Hospital of Nanchang, Nanchang, Jiangxi, China; Departments of 2Urology, 3Imaging, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China; 4Department of Pediatric Surgery, Maternal and Child Health Care Hospital of Ganzhou, Ganzhou, China; 5Department of Urology, The First People’s Hospital of Xiushui, Xiushui, China; 6Department of Urology, Liaobu Hospital of Dongguan, Dongguan, China

Received September 6, 2017; Accepted January 4, 2018; Epub April 15, 2018; Published April 30, 2018

Abstract: Objective: To develop and validate a modified Guy’s Stone Score (GSS) in predicting the success rates and stone free rate (SFR) of percutaneous nephrolithotomy (PNCL). Furthermore, related factors were also evalu-ated. Methods: From December 2012 to December 2014, a total of 270 patients undergoing PCNL were evaluated prospectively. All the patients underwent a plain abdominal radiography (KUB) and/or computed tomography (CT) preoperatively, and the stones were classified according to the modified GSS. The success of the PCNL procedure was defined as the absence of residual stones or the presence of asymptomatic fragments <4 mm in the final CT. Surgical complications were graded according to the modified Clavien classification system. Results: The initial SFR were 96%, 89.9%, 54.2%, 50%, 33.3% and 19.1% in modified GSS grades 1, 2a, 2b, 3, 4a and 4b, respectively, while SFR were 84.6%, 69.6%, 52.4% and 42.3% in the original grades 1, 2, 3 and 4. The global final success rate was 86.1% after the auxiliary procedures and/or re-PCNL. It was found that stone classification, hydronephrosis and congenital malformations of kidney were the three key factors that had statistically significant correlations with the SFR (p<0.05). Conclusions: The modified GSS is a simple, reproducible and high efficient tool for preoperative risk assessment and stone clearance predicting PCNL. It is a potentially clinically translational system.

Keywords: Modified Guy’s stone score, percutaneous nephrolithotomy, renal stone, stone-free rate

Introduction

Percutaneous nephrolithotomy (PCNL) remains the gold standard treatment modality for large and/or complex renal stones [1, 2]. On the other hand, although accepted as minimally invasive, PCNL is an operation which still poses a significant risk of complications. The most frequent complications of PCNL include extrav-asation, blood loss which may lead to the requirement of blood transfusion, and fever [3]. These complications could be graded by the modified Clavien system [4, 5] (Table 1).

According to previous studies, pre- and peri-operative factors such as stone size and con-figuration, percutaneous access number and location, whether the entry was performed by a radiologist or a urologist, and the presence of hydronephrosis are the critical predictors of

stone free rate (SFR) and complications [3, 6-11].

Despite the technique having been introduced for more than 30 years, a standardized method of preoperatively classifying stone diseases to accurately predict the stone-free rates and complications is still lacking. Though complete stone clearance is desirable, it is not possible to achieve every time, especially in cases of stag-horn calculus or in cases where stones are situated in multiple calyces.

Although a number of classification systems have been attempted in the past to predict a stone-free rate [8, 9, 11-16], no currently stan-dardized method has been available to predict the stone-free rate after PCNL. Aiming to obtain a quick, simple and reproducible method for the prediction of PCNL outcomes, Thomas et al.

Evaluation of SFR for PCNL via modified guy’s stone score

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Table 1. Modified Clavien classification systemGrade DescriptionGrade 1 Any deviation from the normal post-operative course without the need for pharmacological treatment

or surgical, endoscopic and radiological interventions (allowed therapeutic regimens are antiemetics, antipyretics, analgesics, diuretics, electrolytes and physiotherapy)

Grade 2 Requiring pharmacological treatment with drugs other than such allowed for grade I complicationsGrade 3a Requiring surgical, endoscopic or radiological interventions not under general anesthesiaGrade 3b Requiring surgical, endoscopic or radiological interventions under general anesthesiaGrade 4a Life-threatening complication requiring Intensive Care Unit management (single organ dysfunction)Grade 4b Life-threatening complication requiring Intensive Care Unit management (multiple organ dysfunction)Grade 5 Death of a patient

[17] developed a scoring system (known as Guy’s scoring system) to grade PCNL stone-free rate and complications.

The Guy’s stone scoring system involves four grades (Grades 1, 2, 3 and 4) according to the caliceal localization of stones, the presence of single or multiple stones and renal anatomic structure (Table 2). The Guy’s stone scoring system is a quick, simple, and reproducible method which has a good correlation with the SFR and the complication rates of PCNL. However, there are still some shortcomings

Table 2. The Guy’s stone scoring systemGrade DescriptionGrade 1 A solitary stone in the mid/lower pole with simple anatomy or a solitary stone in the pelvis with simple

anatomyGrade 2 A solitary stone in the upper pole with simple anatomy or Multiple stones in a patient with simple

anatomy or any solitary stone in a patient with abnormal anatomyGrade 3 Multiple stones in a patient with abnormal anatomy or stones in a calyceal diverticulum or partial

staghorn calculusGrade 4 Staghorn calculus or any stone in a patient with spina bifida or spinal injury

such as the SFRs between the solitary stone in the upper pole and the multiple stones are dif-ferent in Grade 2. To overcome these disadvan-tages, in this study, we refined the Guy’s stone scoring system and evaluated the modified sys-tem’s efficacy in grading stone-free rate and perioperative complications.

Materials and methods

Study population

A total of 270 patients who underwent PCNL from December 2012 to December 2014 at our

Table 3. Modified Guy’s Stone ScoreGrade DescriptionGrade 1 A solitary stone in the mid/lower pole with simple anatomy or a solitary stone in the pelvis with simple

anatomyGrade 2Grade 2a A solitary stone in the upper pole with normal anatomyGrade 2b Multiple stones in a patient with normal anatomy (multiple stones scattered at least 2 calices) or par-

tial staghorn calculus (less than half of all renal calices); or a solitary stone in a patient with abnormal anatomy

Grade 3 Multiple stones in a patient with abnormal anatomy (multiple stones scattered at least 2 calices) or partial staghorn calculus (more than half of all renal calices) or in a calyceal diverticulum;

Grade 4Grade 4a A complete staghorn calculus Grade 4b A complete staghorn calculus complicated calyceal multiple calculi or any stone in a patient with

severe spina deformity or with kidney dysplasia


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Figure 1. Stone free rates and complication rates in modified Guy’s stone score.

hospital were prospectively evaluated. Ethical clearance was obtained by our Institutional Ethical Committee. All patients were informed about the potential benefits and risks of the PCNL procedure and patients signed an informed written consent form. Inclusion crite-ria comprised renal stone of size ≥ 2 cm (1.5 cm if lower pole), multiple stones, or failure of other treatment modalities. Exclusion criteria were under age 14 and co-morbidities such as ureteral calculi, renal insufficiency, or untreat-ed coagulopathy. Patients with concomitant ureteral stones requiring simultaneous ure-teroscopy or extracorporeal shockwave litho-tripsy (ESWL) were also not included in this analysis. All the trails were performed in prone position and by one single surgeon (F.C.V.) who had more than 20 years of surgical experi-ence and had performed more than 1000 PCNL procedures.

All patients were classified according to the modified Guy’s Stone Score (Table 3 and Figures 2-7) based on the findings of plain abdominal radiography (KUB) and/or Computed tomography (CT).

Operations and outcome evaluation

Minimally invasive PCNL (mini-PCNL) technique was utilized with the use of an 8/9.5 F rigid ure-teroscope. To be brief, all of the operations were performed under general anesthesia. After ureteral catheter insertion in the lithoto-my position, the patients were tilted to prone position. The pyelocalyceal system was app-

roached with the insertion of an 18-gauge needle under fluoroscopy. Tract dilation was achieved with fascial dilators and an amplatz sheath was placed. A holmi-um laser lithotripter was used for stone fragmenta-tion. The stone fragments were mechanically extracted and a 14 F nephrostomy catheter was placed inside the renal pelvis; in cases of ure-teropelvic junction signifi-cant edema, extensive pelvic injury, or ureteral manipula-tion, a 6 F double-J stent was used instead. Operation time was recorded from the

beginning of the cystoscopy for ureteral cathe-ter insertion to the end of the nephrostomy placement. Surgical complications were graded according to the modified Clavien classification system. Postoperative stone-free rates were determined by KUB and/or CT. In our study, suc-cess of the PCNL procedure was defined as the absence of residual stones or the presence of asymptomatic fragments <4 mm in the final CT.

Statistical analysis

SPSS 19.0 (USA) was used for statistical analy-sis. The results were presented as the mean ± standard deviation and range. P<0.05 was considered to indicate a statistically significant difference. Multivariate linear regression was used to analyze the correlation between the preoperative variables and postoperative SFR in PCNL.

Results

From December 2012 to December 2014, 270 patients were treated by mini-PCNL at our hos-pital. In terms of gender incidence, 156 (57.8%) of the patients were female, and 114 (42.2%) were male. The mean patient age was 45 ± 14 (range 14-81). According to the modified Guy’s stone stratification, of the 270 PCNLs, 75 (27.8%) were classified as G1; 69 (25.6%) as G2a; 48 (17.8%) as G2b; 36 (13.3%) as G3; 21 (7.8%) as G4a and 21 (7.8%) as 4b.The mean pre-operative haemoglobin (Hb) of the 270 patients was 122 ± 16 (range 78-156). Ninety-eight patients were with solitary stone and 172


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patients were with multiple stones. The demo-graphic and clinical characteristics of the patients and stones are summarized in Table 4.

The surgical procedure information and the outcomes are summarized in Table 5. Single channel puncture was done in 223 (82.6%) patients, double channel puncture was done in 45 (16.7%) patients, and three channel punc-ture was done in 2 (0.7%) patients. The average operation time was 99 ± 25 min (range 45-180

min) and the mean post-operative Hb was 113 ± 16 g/L (range 65-148 g/L). The overall com-plication rate according to the modified Clavien grading system was 20% (54) and most of the complications encountered were Clavien grade 1(11.9%). Clavien grade 2, 3a, 3b, 4a, 4b and 5 were seen in 8.1% (4.4%, 0.7%, 2.3%, 0.7% and 0, respectively). The modified GSS accurately predicted a significant difference among groups (P=0.004, Figure 1). The overall immediate success rate was 61.1%. Twenty and 29

Figure 2. Representative images of grade 1. A: Left renal pelvis stones shown by CT. B: Left renal lower calyx stone shown by KUB.

Figure 3. Representative images of grade 2a. A: Left renal upper calyx stone shown by KUB. B: Left renal upper calyx stone shown by CT.


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Figure 4. Representative images of grade 2b. A: Left renal multiple calculi shown by KUB. B: Left renal multiple cal-culi shown by CT. C: Staghorn calculus of left kidney shown by KUB. D: Hypoplasia of right kidney with nephrolithiasis shown by CT.

patients underwent ESWL and re-PCNL for residual stones, respectively. The global final success rate of the patients was 86.1% after the auxiliary procedures and/or re-PCNL.

The SFR were 96%, 89.9%, 54.2%, 50%, 33.3% and 19.1% in modified Guy’s stone grade 1, 2a, 2b, 3, 4a and 4b, respectively, while SFR were 84.6%, 69.6%, 52.4% and 42.3% in the Guy’s grade 1, 2, 3 and 4, respectively (Table 6). Multivariate linear regression analysis (SPSS) was used to investigate the factors potentially affecting SFR. The stone score, hydronephro-sis, and congenital malformations of kidney were three key factors that significantly predict-

ed the SFR. None of other factors (i.e., patient age, stone amount, other disease, operation time etc.) was statistically correlated with the SFR.

Discussion

Although PCNL is a common therapeutic strat-egy in patients with renal stones, the ultimate success rate cannot be predicted exactly as it depends on several variables. Some of these can be predicted before surgery, such as stone burden and upper tract anatomy, but success also depends on the surgical experience [18]. Researchers have been attempting to develop


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Figure 5. Representative images of grade 3. A: Diverticulum of right renal diverticulum shown by KUB. B: Diverticu-lum of right renal diverticulum shown by Intravenous Urogram (IVU). C: Part of staghorn calculus of left kidney shown by KUB (Bigger than half of all kidney calices). D: Polycystic kidney with multiple renal calculi shown by CT.

a grading system to predict the success of PCNL for a long time. Several scoring systems have been developed for predicting the SFR. These have tried to incorporate different vari-ables in an efficient and simple manner to quantify the complexity of renal stones. Tefekli et al. [19] attempted to compartmentalize the

severity of complications according to the com-plexity of stone, but they did not find any signifi-cant correlation. De la Rosette et al. [20] ass- orted renal stones based on the stone burden. They divided stone burden into three classifica-tions as <1 cm, 1-2 cm and >2 cm. They found that the size of stone was significantly related


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Figure 6. Representative images of grade 4a. A: Complete staghorn calculus of right kidney shown by KUB. B: Stag-horn calculus of both kidneys shown by KUB.

to the operation time. Michel et al. [3] found that stone size had statistical significant corre-lation with complications. Okhunov et al. [21] put forward a novel quantitative scoring system which integrates five components measured from before surgery to predict the stone free status of a patient from preoperative character-istics available on non-contrast-enhanced CT images: stone size, tract length (skin-to-stone distance), degree of obstruction, number of calyces involved and stone essence (density). The scoring system can be used as a standard method for predicting the SFR after PCNL, how-ever, other investigators have not validated in this study.

Recently, Thomas et al. [17] developed the GSS trying to predict success rate and complication of PCNL preoperatively. Mandel et al. [22] applied GSS to PCNL and found it to correlate well with SFR. They observed a final SFR of 97.7 % and stone clearance in GSS I and II was 100%. Vicentini et al. [23] confirmed that the GSS was highly efficient in predicting SFR even on applying computed tomography (CT). They defined SFR status as the absence of a residual fragment or the presence of an asymptomatic fragment of ≤4 mm and they found a significant correlation between GSS and both stone-free rate and complication rate.

However, some problems still existed in the sys-tem: First, multiple stones were not clearly

defined, especially for Grades 2 and 3; Second, partial staghorn calculus can be grouped into grade 2, which has obvious differences with multiple stones in puncture and stone clear-ance; Third, the types of spinal deformity and kidney dysplasia should be covered grade 4; Fourth, the impact of hydronephrosis on SFR was not taken into account; Fifth, spinal injury cannot be classified as Grade 4, since it was easy to lead to stone recurrence and urinary tract infection and had little relevance for resid-ual stones after PCNL.

The present study was undertaken to refine the GSS and evaluate the modified system’s effi-cacy in grading stone-free rate and periopera-tive complications. The modified GSS is shown in Table 3. Kidney stones in a patient with spi-nal injury were excluded in the modified GSS, while the complete staghorn calculus was com-plicated calyceal multiple calculi were incorpo-rated in grade 4b innovatively. There has been no study about the complete staghorn calculus complicated calyceal multiple calculi and the SFR of which is completely different with the SFR of the complete staghorn calculus as the stone burden is larger, the operation time is lon-ger and the bleeding risk increases.

We applied KUB and/or CT findings to classify the patients according to the modified GSS and we defined stone-free status as no residual fragment or fragment <4 mm. We found


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Figure 7. Representative images of grade 4b. A: Sponge kidney with multiple renal calculi shown by CT. B: Multiple calculi of renal calyx with double kidney complete staghorn calculi shown by KUB. C: Left kidney cast stone of left kidney shown by KUB (Ectopic kidney). D: Horseshoe kidney with left renal multiple calculi shown by CT. E: Spinal deformity with left kidney stones shown by KUB. F: Multiple calculi of renal calyx with left kidney complete staghorn calculi shown by KUB.

Table 4. Pre-operative clinical data of the patientsVariable Value P valueGender (n/%) 0.066 Male 156/57.8% Female 114/42.2%Patient age (years) 0.836 Mean ± SD 45 ± 14 Range 14-81Pre-operative Hb (g/L) - Mean ± SD 122 ± 16 Range 78-156Stone amount (n/%) 0.103 Solitary stone 98/36.3% Multiple stones 172/63.7%Hydronephrosis (n/%) 0.022 Nil 40/14.8% Mild 97/35.9% Moderate 61/22.6% Severe 72/26.7%Other disease (n/%) 0.976 Nil 185/68.5% Solitary kidney 34/12.6% Severe lung disease 27/10% Chronic kidney disease 20/7.4% Heart disease 4/1.5%Previous ipsilateral renal surgery 0.622 Yes 88/32.6% No 182/67.4Preoperative urinary tract infection 0.766 Yes 129/47.8% No 141/52.2%Congenital malformations of kidney 0.014 Yes 43/15.9% No 227/84.1%

that the modified GSS could predict the SFR better than the original system. Additionally, it had a positive correlation between the modi-fied GSS and the complication rate. Unlike Thomas et al. [18], Mandal et al. [22] also found a positive correlation between the GSS and complication rates.

The main limitation in our study was that it was a single-center study with a limited number of

cases, especially in grades 3, 4a and 4b. A larger scale multi-center study should be undertaken to validate and confirm our results. Further- more, the results discussed here were all generated from surgeries performed by a single surgeon, who had more than 20 years of expe-rience in urology. It is also necessary to validate the applicability of our modified guy’s stone score system in predicting the general out-come in the cases where several surgeons with differ-ent experience levels are involved.

The present study detailed the improvement of Guy’s stone score system with an increase of two grading sub-types and appropriate ad- justment of the original method, making the classifica-tion more reasonable, closer to the clinic and better corre-lated with the SFR. It is a simple, reproducible, and high efficient tool for preopera-tive risk assessment and for predicting complications with PCNL. Further multi-cen-ter studies with larger scale samples will be necessary to clarify these findings.

Disclosure of conflict of Interest

None.

Address correspondence to: Weimin Chen, De- partment of Urology, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang 330006, Jiangxi, China. Tel: 0086 13970010866; E-mail: wmchennc2000@ 126.com

mailto:[email protected]

mailto:[email protected]


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Table 5. Operative data and outcome of PCNL proceduresVariable Value P valueOperation time (min) 0.077 Mean ± SD 99 ± 25 Range 45-180Number of tracts (n/%) 0.242 1 223/82.6% 2 45/16.7% 3 2/0.7%Modified Guy’s stone score (n/%) 0.001 G1 75/27.8% G2a 69/25.6% G2b 48/17.7% G3 36/13.3% G4a 21/7.8% G4b 21/7.8%Post-operative Hb (g/L) - Mean ± SD 113 ± 16 Range 65-148Hospitalization time (d) 0.066 Mean ± SD 13.2 ± 6.3 Range 5-51Auxiliary procedures (n/%) - Conservative treatment 56 (53.3%) ESWL 20 (19.1%) Re-PCNL 29 (27.6%)Complication rate (n/%) 54 (20%) 0.004 Clavien 1 32 (11.9%) Clavien 2 12 (4.4%) Clavien 3a 2 (0.7%) Clavien 3b 6 (2.3) Clavien 4a 2 (0.7%) Clavien 4b - Clavien 5 -Final success rate (%) 86.1%

thiasis. Eur Urol 2001; 40: 362.

[2] Pearle MS, Wolf JS Jr; AUA Nephrolithiasis Guideline Panel. Chapter 1: AUA guideline on manage-ment of staghorn calculi: diagnosis and treatment recommendations. J Urol 2005; 173: 1991-2000.

[3] Michel MS, Trojan L and Rassweiler JJ. Complica-tions in percutaneous nephrolithotomy. Eur Urol 2007; 51: 899-906.

[4] de la Rosette JJ, Opondo D, Daels FP, Giusti G, Ser-rano A, Kandasami SV, Wolf JS Jr, Grabe M and Gravas S. Categorisation of complications and va- lidation of the Clavien score for percutaneous nephrolithotomy. Eur Urol 2012; 62: 246-255.

[5] Dindo D, Demartines N and Clavien PA. Classifica-tion of surgical complica-tions: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004; 240: 205-213.

[6] Akman T, Binbay M, Sari E, Yuruk E, Tepeler A, Ak-cay M, Muslumanoglu AY and Tefekli A. Factors af-fecting bleeding during percutaneous nephrolithotomy: single surgeon ex-perience. J Endourol 20- 11; 25: 327-333.

[7] El-Assmy AM, Shokeir AA, Mohsen T, El-Tabey N, El-

Nahas AR, Shoma AM, Eraky I, El-Kenawy MR and El-Kappany HA. Renal access by urologist or radiologist for percutaneous nephrolithoto-my--is it still an issue? J Urol 2007; 178: 916-920.

[8] Turna B, Umul M, Demiryoguran S, Altay B and Nazli O. How do increasing stone surface area and stone configuration affect overall outcome of percutaneous nephrolithotomy? J Endourol 2007; 21: 34-43.

[9] Olbert PJ, Hegele A, Schrader AJ, Scherag A and Hofmann R. Pre- and perioperative predic-tors of short-term clinical outcomes in patients undergoing percutaneous nephrolitholapaxy. Urol Res 2007; 35: 225-230.

[10] El-Nahas AR, Shokeir AA, El-Assmy AM, Mohsen T, Shoma AM, Eraky I and El-Kenawy MR, El-

Table 6. The relationship between the original and the modified Guy’s stone scoreGuy’s stone score SFR (%) Modified Guy’s

stone score SFR (%)

Grade 1 81 Grade 1 96.0Grade 2 72.4 Grade 2a 89.9

Grade 2b 54.2Grade 3 35 Grade 3 50.0Grade 4 29 Grade 4a 33.3

Grade 4b 19.1

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