Clinical comparison of the pneumatic and the combined lithotripters in percutaneous nephrolithotomy

Clinical comparison of the pneumatic and the combinedlithotripters in percutaneous nephrolithotomy

Gokhan Koc,1* Kaan Esat Akbay,2 Huseyin Tarhan,1 Ozgur Cakmak1 andYuksel Yilmaz1

1Department of Urology, Tepecik Teaching and Research Hospital, and 2Department of Urology, Metropol MedicalCenter, Izmir, Turkey.

Aim: To compare the effectiveness of the pneumatic lithotripter and the combined lithotripter (pneumatic +ultrasonic) in percutaneous nephrolithotomy (PNL).Patients and Methods: A total of 150 patients who underwent PNL between March 2009 and January 2011were included in the study. In the first 49 cases, only the pneumatic lithotripter (group 1) was used, while in thenext 101 patients, combined lithotripter (group 2) was used. Differences with regard to total clearance time,fluoroscopic screening time (FST), duration of hospital stay, duration of nephrostomy removal, haematocritloss, blood transfusion rate and successful treatment rate were investigated between the two groups.Results: The general characteristics of the patients were similar between the two groups. However, the meanstone size was statistically significantly higher in group 2. No statistically-significant difference was detectedbetween the two groups in terms of hospital stay, nephrostomy removal days, successful treatment rate andblood transfusion rate, but compared to group 1 patients, total clearance time, FST and haematocrit loss weresignificantly less in group 2.Conclusion: Although pneumatic and ultrasonic lithotripters are both sufficiently effective when used sepa-rately, the combined device was observed to positively influence total clearance time, FST and haematocritloss significantly.

Key words: calculi, lithotripter, percutaneous nephrolithotomy, pneumatic, ultrasonic.

Introduction

Stone therapy has been revolutionized during the pastthree decades. Extracorporeal shock wave lithotripsy(ESWL) and percutaneous nephrolithotomy (PNL)have changed the general approach to the kidneystones, and have replaced open stone surgery.1,2 Dueto both higher success rates and lower complicationand mortality rates, PNL has been the standardmethod for the treatment of kidney stones larger than2 cm and lower pole renal calculi larger than 1.5 cm.3

Currently, pneumatic4 and the ultrasonic5 lithot-ripters are widely used in PNL, although laser lithot-ripters, such as pulse dye laser (PDL),6 alexandritelaser (AXL),7 neodymium : yttrium–aluminium–garnetlaser (Nd : YAG),8 and holmium : yttrium–aluminium–garnet laser (Holmium : YAG)9 and other differentlithotripters, such as electrohydraulic lithotripsy(EHL)10 and electrokinetic lithotripsy11 are also avail-

able. The pneumatic and the ultrasonic lithotripsydevices can be used separately or combined(pneumatic + ultrasonic), where the two systems canbe used either separately or simultaneously.12 Theyfunction through different mechanisms, thus bothpossess different advantages and disadvantages inpractice. However, the superiority of the combinedlithotripsy device has been demonstrated in variousstudies.13–18

Despite the known advantages of the combinedlithotripsy device, it is not available in some urologyclinics. As we have a combined lithotripter, we usedthis device in PNL operations to evaluate our results. Inthe present study, we aimed to compare the pneu-matic and the combined lithotripsy devices used inPNL operations by comparing their clinical efficiencyand possible complications relative to each other.

Methods

A total of 150 patients who underwent PNL at our clinicbetween March 2009 and January 2011 were includedin the study. This study was done in accordance with

*Author to whom all correspondence should be addressed.Email: [email protected] 16 May 2012; accepted 16 July 2012.

bs_bs_bannerSurgical Practicedoi:10.1111/1744-1633.12000 Original Article

© 2012 The AuthorsSurgical Practice © 2012 College of Surgeons of Hong Kong Surgical Practice (2013) 17, 58–62

the principles of the Declaration of Helsinki, 2008.Written, informed consent was obtained for eachpatient, and institutional review board approval wasobtained from the local ethics committee. Patients whohad more than one renal access were excluded fromthe study. In the first 49 cases, only the pneumaticlithotripter (Vibrolith®; Elmed, Ankara, Turkey) (group1) was used, while in the next 101 cases, thepneumatic + ultrasonic lithotripsy device (SwissLithoClast® Master; EMS, Nyon, Switzerland) wasused (group 2). Total clearance time was calculated asthe seconds per each mm2 of stone burden (s/mm2)during the period, starting from the initiation of stonecrushing just after the completion of renal access untilthe nephrostomy tube was inserted.

Radiological examinations, including excretoryurography and/or noncontrast spiral tomography, wereperformed in all of the study patients preoperatively.Stone size was assessed as the surface area andcalculated according to the EAU guidelines.19 Urineculture was performed 1 week before surgery; appro-priate treatment was administered if necessary, andthe operation was then performed. Some laboratorytests, such as complete blood count, serum creati-nine, liver function tests, electrolytes, prothrombin timeand partial thromboplastin time, were conducted foreach patient before intervention.

All PNL procedures were performed with the patientunder general anaesthesia. After cystoscopy andurethral catheterization, percutaneous access wasachieved using an 18 gauge access needle under Carm fluoroscopy. A guidewire was inserted through theneedle, and the tract was dilated with an Amplatzdilator (Cook Urological, Spencer, IN, USA). A 30 FrAmplatz working sheath (Cook Urological) was placedinto the collecting system, and a 26 Fr rigid nephro-scope was placed through the sheath. Kidney stoneswere crushed into tiny fragments with a pneumaticlithotripter and removed with grasping forcepsin group 1 patients. In group 2 patients, the kidneystones were crushed with a pneumatic and ultrasoniclithotripter and aspirated with a ultrasonic probe orwith a grasping forceps for the larger fragments. At the

end of this procedure, a 14 F nephrostomy tube wasplaced. On the first postoperative day, all patientsunderwent routine plain radiography in order to checkfor residual stone fragments. If the radiological studyrevealed stone-free or clinically-insignificant residualfragments (CIRF) of < 4 mm, then treatment was con-sidered successful.

In the first 30 patients, antegrade nephrostogramwas performed on the second postoperative day, andthe nephrostomy tube was removed if ureteral flow tothe bladder was detected. In the next 120 patients,antegrade nephrostogram was not performed, butthe nephrostomy tube was clamped, and during thefirst 3 h, if the patient did not suffer pain and ifurinary extravasation was not detected at the rims ofthe nephrostomy tube, then the nephrostomy tube wasremoved. All patients were reevaluated with excretoryurography and/or spiral computerized tomography inthe third postoperative month. A second-look proce-dure was not performed in any of the patients, butESWL was performed in the first postoperative monthin patients with residual fragments > 5 mm.

Total clearance time, fluoroscopic screening time(FST), duration of hospital stay, duration of nephros-tomy removal, haematocrit loss, blood transfusion rateand, successful treatment rates of all patients wererecorded. These values were evaluated retrospec-tively and compared for groups 1 2. For the statisticalanalysis, c2-test and t-test methods were used;P < 0.05 was considered statistically significant.

Results

Age, sex, stone location, operative time and a historyof ipsilateral kidney stone operation, which mightaffect FST and body mass index values between thetwo groups, were similar; however, compared to group1, the mean stone size was statistically significantlyhigher in group2 [mean stone size: 404.4 mm2 (93.2–1061.6) and 583.6 mm2 (92.4–1971.7), respectively,P < 0.05] (Table 1).

In terms of hospital stay, nephrostomy removal days,successful treatment rate and blood transfusion rate,

Table 1. General characteristics of the patients

Overall Group 1 Group 2 P-value

No. patients 150 49 101Age 46.2 (17–73) 47.5 (20–71) 42.7 (17–73) 0.06Mean stone size (mm2) 491.8 (92.4–1971.7) 404.4 (93.2–1061.6) 583.6 (92.4–1971.7) < 0.05No. males/females 101/49 37/12 64/37 0.50Renal surgery history (per cent) 30 (20.0) 8 (16.3) 22 (21.7) 0.50Body mass index 27.8 � 4.3 27.5 � 3.7 26.5 � 4.4 0.76

Lithotripters in percutaneous renal surgery 59


statistically-significant differences could not bedetected between the two groups. In group 1 patients,the stone-free rate was 75.5 per cent, the CIRF ratewas 18.3 per cent and the successful treatment ratewas 93.8 per cent. In group 2 patients, the stone-freerate was 78.4 per cent, the CIRF rate was 13.7 percent and the successful treatment rate was 92.1 percent. Total clearance time, FST and haematocrit lossrevealed statistically-significant differences betweenthe two groups. Compared to group 1, group 2patients showed significantly shorter total clearancetime (12.8 � 8.3 s/mm2 and 9.9 � 4.7 s/mm2, respec-tively, P < 0.05) and FST (285.3 � 112.6 s and216.7 � 89.6, respectively, P < 0.05), and significantlyless haematocrit loss (5.0 � 3.4 g/dL and 3.3 � 2.0 g/dL, respectively, P < 0.05) (Table 2).

Discussion

Although pneumatic and ultrasonic lithotripters areused for PNL, there are different lithotripters available.EHL was the first lithotripter used in clinical practice.The mechanism of the EHL system is through vapori-zation and cavitation bubbles due to electrical sparkdischarge.20 High success rates were noted for theremoval of ureteric stones; however, the safety marginwas reduced because of serious complications, suchas ureteral perforation and bleeding.10

Laser technology can also be used for lithotripsy.The advantage of laser fibres is their thin and flexiblestructure; therefore, laser technology can be used inall endoscopic instruments available and allows easyaccess to all parts of the urogenital system. However,it is an expensive system, and has a low fragmentationrate, especially for hard and large stones. In addition,it might cause tissue damage due to thermal effects.21

Different laser types, such as PDL, AXL, Nd : YAG,Holmium : YAG are available.6–9 The Holmium : YAGlaser was developed with advancing laser technology,and has been the gold standard for laser lithotripsy.The principle mechanism in stone fragmentation isthe photothermal chemical effect.9 Unlike other laser

technologies, it executes effective disintegration in alltypes of kidney stones, including cystine and calciumoxalate monohydrate, excluding calculi > 2 cm, andmight cause complications, such as tissue damageand ureteral perforation.22

Pneumatic lithotripters use compressed air to accel-erate a projectile to the metal probe. This mechanicalenergy is dissipated through the metal wire and actsas a chisel on the surface of the stone; therefore, directcontact with the stone surface is required, and heat isnot generated throughout this action. An overall frag-mentation rate of 84–100 per cent and stone-free rateof 70–98.6 per cent have been reported.23,24 There arevarious probe sizes available, but they cannot be usedwith flexible instruments, which is considered a disad-vantage. The inability to simultaneously extract stonesduring fragmentation, and retropulsion of the stonedue to the energy released after contact with thestone, are other disadvantages.

Ultrasonic lithotripters use ultrasonic waves gener-ated by piezoceramic elements. The ultrasonic waveenergy is transmitted along a probe and converted tovibration at the tip, which results in the drilling action.Direct contact between the probe and the stone isrequired. The fragments are aspirated through thehollow probe.5 Being safe, causing minimal tissueeffects and aspirating fragments through the hollowprobe are the known advantages. The inability to beused with flexible instruments due to the thick probes,and overheating, are disadvantages. In order to avoidthis, it should not be used for prolonged periodswithout a suction probe.25 A fragmentation rate of97–100 per cent and stone-free rate of 94 per centhave been reported.21

Currently, combined devices using both pneumaticand ultrasonic lithotripters have been used clinically.The 1 mm pneumatic probe runs through the 3.3 mmultrasonic probe, and the tip remains approximately1 mm outside to ensure direct contact with calculi.While fragmenting the calculi, suction of the tinypieces can also be managed simultaneously. Usingthis system, different stones could be successfully

Table 2. Comparison of outcomes of groups 1 and 2

Group 1 Group 2 P-value

Total clearance time � SD (sec/mm2) 12.8 � 8.3 9.9 � 4.7 < 0.05FST � SD (s) 285.3 � 112.6 216.7 � 89.6 < 0.05Hospital stay (day) 2.7 (1–6) 2.7 (1–5) 0.14Nephrostomy removal (day) 2.3 (1–5) 2.3 (1–5) 0.22Successful treatment (per cent) 93.8 92.1 0.73Haematocrit loss (g/dL) 5.0 � 3.4 3.3 � 2.0 < 0.05Blood transfusion (per cent) 3.7 2.4 0.15

FST, fluoroscopic screening time; SD, standard deviation.

G Koc et al.60


treated with a more rapid application.13 Various in vitroand clinical results have been obtained with thisdevice. Hofmann et al. compared the combineddevice with both the ultrasonic and the pneumaticlithotripsy devices in vitro. They found that the disinte-grated stone mass was 1.5–4 times larger, and the 50per cent disintegration time was 30–50 per centshorter after 1 min with the combined system.13 Agueet al. conducted a similar study. The complete calcu-lus removal time was found to be significantly shorterwith the combined device.14 Pietrow et al. comparedthe combined device and the ultrasonic device clini-cally, and the mean complete stone clearance timewas found to be significantly shorter with the com-bined system.15 Lehman et al. compared the com-bined device and the ultrasonic device and obtainedsimilar values for fragmentation time and operativetime. However, regarding the composition of thecalculi, they reported that the combined device wasmore effective for hard calculi.16 Cho et al. comparedthe combined device and the pneumatic device andfound significantly lower values for operative time,number of hospital days and average haemoglobinloss with the combined device.17 In their patientstreated with the combined system, Hofmann et al.reported a complete stone-free rate of 66 per centfollowing the first PNL, without significant complica-tions, and as 76 per cent when a second PNL wasrequired.18 In the present study, we did not find astatistically-significant difference between the groupsregarding hospital stay, nephrostomy removal days,successful treatment rate and blood transfusion rate;however, the differences regarding total clearancetime, FST and haematocrit loss were statistically sig-nificant between the two study groups. The combineddevice might appear not to significantly affect thestone-free rate, but it does reduce the operative time,and therefore, reduces haematocrit loss and FST.However, it does not cause any increase in the rate ofcomplications. Additionally, our stone-free rates weresimilar to the results of other studies.26,27

We did not examine the stone composition, whichcan be considered a limitation of our study. In clinicalpractice, the combined system has been shown tohave successful treatment rates and significantlylower complication rates, which supports our argu-ment that the combined device should be appliedroutinely in clinical use. In this respect, further data ofthe multicenter studies conducted with more patientsare required for evaluation.

Conclusions

Pneumatic and ultrasonic lithotripters are widely usedin PNL surgery. Although they are effective when used

separately, their combined use might significantlyaffect operative time, blood loss and stone-free rates.The efficacy and safety of the combined device hasbeen proved, and we believe that it should be routinelyused in PNL operations.

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Clinical comparison of the pneumatic and the combined lithotripters in percutaneous nephrolithotomy