The current status of percutaneous nephrolithotomy in the ... · The current status of percutaneous...

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The current statusof percutaneous nephrolithotomy

in the management of kidney stones

M. P. YUHICO, R. KO

Department of Urology, Nepean HospitalUniversity of Sydney, Sydney, Australia

Large kidney stones (>2 cm) is a common pro-blem affecting all population groups across theglobe and may result in significant complica-tions if left untreated. The treatment for thiscondition has evolved dramatically over thepast seven decades with the advent of mini-mally invasive treatment options. At the fore-front of this paradigm shift is the developmentof percutaneous nephrolithotomy (PCNL). Thishas resulted in shorter hospital stays, reducedpostoperative pain, and quicker convalescencecompared with the previous criterion standardof open stone surgery. PCNL is only one of themany minimally invasive treatment optionsavailable for this condition, but remains themost efficient in all patient groups. However, itcontinues to be one of the more challengingurological procedures, which if not performedwell, can be associated with significant com-plications. Refinements in techniques, impro-vement in equipment and increasing clinicalexperience have led to improved stone freerates being achieved with acceptably low patientmorbidity. In this article, authors review thetechnical aspects, outcomes, and current role ofPCNL in the treatment of large kidney stones. Key words: Nephrostomy, percutaneous -Kidney calculi - Surgical procedures, minimallyinvasive.

History and development

Percutaneous nephrolithotomy (PCNL) inthe modern era has been the culmina-

tion of nearly seventy years of development.The foundations were laid in 1941 whenRupel and Brown first reported that renalstones could be removed through an opera-tively established nephrostomy tract.1 Theyperformed the first nephroscopy when a rigidcystoscope was passed through a nephros-tomy tract and residual stones removed fol-lowing open surgery. It was not until 1955when Goodwin et al. created the first percu-taneous tract by inserting a nephrostomy tubeinto an infected hydronephrotic kidney.2 Thisled to the realization that a percutaneous tractcould be used as access into the kidney. In1976, Fernström and Johansson described anew extraction technique when they removedkidney stones through a percutaneousnephrostomy under radiological control.3Subsequently in 1977, Kurth et al. provideda means for removing large stones through anephrostomy tract when they described theuse of an ultrasonic lithotripsy device dur-ing PCNL to fragment a staghorn calculus.4

In the 1980s, PCNL underwent rapid evo-

Conflict of interest.—None.Acknowledgments.—The authors would like to express

their deep gratitude for technical assistance given by: MrDavid Barnes, Diploma of Diagnostic Radiology and to Ms.Zaphiria Takonis, BaAppSc, Diagnostic Radiography,University of Sydney.

Corresponding author: R. Ko, Consultant Urologist, NepeanHospital, Kingswood, 2747, NSW, Australia.E-mail: [email protected]

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YUHICO PERCUTANEOUS NEPHROLITHOTOMY

lution following an overall paradigm shift ofstone treatment towards a more minimallyinvasive approach. The percutaneous tech-nique for the creation of a nephrostomy tractwas improved upon and facilitated the safeintroduction of endourologic proceduresthrough this route. Initially, conventional rigidcystoscopes were used but these were sub-sequently replaced with purpose built offsetnephroscopes featuring a large caliber straightworking channel.

The technique of PCNL gained popularityin Europe through the pioneering achieve-ments of Alken et al.5 in Germany, Marbergeret al.6 in Austria, and in the United Kingdomby Wickham and Kellet 7 around similartimes. Subsequently, the technique gainedacceptance in the United States following fur-ther development by Segura’s group 8 at theMayo Clinic, along with Clayman et al. at theUniversity of Minnesota.9 PCNL was initiallyreserved only for patients who were poorcandidates for open surgery but with rapiddevelopments of purpose built equipmentand ancillary tools, PCNL has now becomethe treatment of choice for large kidneystones.10

Indications

Multiple factors are taken into considera-tion when deciding upon PCNL. These aredivided into: stone, kidney, and patient fac-tors. Individually, they each play an importantrole in determining the optimal approachthat will render the patient stone free in themost efficacious manner.

Stone characteristics

Stone size remains important because larg-er stones are more efficiently treated percu-taneously relative to other minimally inva-sive modalities. In a study comparing extra-corporeal shock wave lithotripsy (SWL) andPCNL, Lingeman et al. showed an increasedincidence of residual fragments and higherretreatment rates following SWL as stone sizeincreased.11 When treated with SWL alone,the stone free rate decreased from 77% for

stones ≤1 cm to 29% for stones >3 cm. Thenumber of ancillary procedures also increasedfrom 12% to 46%, respectively. Importantly,in the only randomized, prospective trialcomparing PCNL to SWL for staghorn cal-culi, Meretyk et al. showed that stone freerates for PCNL based therapy was more thanthree times better when compared to SWLmonotherapy (74% vs 22%. respectively,P=0.0005).12

Stone composition, if known prior to treat-ment, should be taken into consideration indeciding between various treatment options.Stones such as cystine, calcium oxalatemonohydrate, and brushite are known tofragment poorly to SWL 13 and may best betreated with either retrograde intrarenalpyeloscopic surgery or PCNL. Computedtomography (CT) has been reported to beuseful in determining the stone’s compositionaccording to its Hounsfeld unit (HU) value.14

In vitro studies show attenuation levels foruric acid and struvite stones to be consis-tently below 1 000 HU, whereas calciumoxalate and hydroxyapatite usually exceed-ed 1 000 HU.15, 16 Joseph et al. suggested thatPCNL be used more judiciously for stoneswith attenuation levels exceeding 1 000 HUdue to poor stone clearance rates usingSWL.17 Similarly, Gupta et al. suggested aneven lower cutoff of 750 HU above whichPCNL would be a better alternative.18 Basedon these studies, better results may beachieved using PCNL for stones having highHU values comparing to SWL.

Kidney factors

Kidneys with complex or anomalous anato-my such as ureteropelvic junction obstruc-tion, calyceal diverticulum, and benign ureter-al strictures can impair renal drainage andhinder stone passage. When suitable, PCNLoffers potentially better stone free rates andallows simultaneous correction of the under-lying problem. Other congenital malforma-tions such as horseshoe, malrotated, orectopically positioned kidneys may be besttreated initially by PCNL alone, or in combi-nation with other modalities.

Kidneys containing stones in the lower

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Patient characteristics

PCNL may be a better option for patientswith stones who are morbidly obese, or whohave musculoskeletal defects such as scol-iosis and spina bifida when compared toother stone treatment modalities. Morbidlyobese patients with renal stones present atherapeutic challenge because they mayexceed the weight limits for SWL machines.23

For those who do not exceed the weightlimit, Pareek et al. found in a series of low-er pole stone patients that a skin-to-stonedistance (SSD) greater than 10 cm as deter-mined on axial CT images was predictive offailure using SWL.24 Additionally, eventhough body mass index (BMI) has beenshown to be an independent predictor ofSWL success, this study showed SSD to be amore reliable predictor than either BMI orHU measurements alone.24 For obese patients(BMI>30) with large stone burden, treatmentwith PCNL may require longer instruments,but stone-free rates of up to 83% to 88%were achieved without any significant dif-ferences in morbidity compared with non-obese patients.25, 26

Recommendations of the EAU GuidelinesPanel

The accepted indications for PCNL accord-ing to the European Urology Associationguidelines panel are summarized in TableI.27-29


pole have always been the subject of con-tention as to which approach represents thebest treatment option. The factors in lowerpole anatomy described by Sampaio et al.consisting of an infundibulopelvic angle lessthan 90°, infundibular width less than 4 mm,and infundibular length more than 3 cm areconsidered unfavorable for drainage of stonefragments in the lower pole.19 Elbahnasy et al.also presented similar findings although themanner of measuring the infundibulopelvicangle and critical value for infundibular widthwas measured differently.20

In 2001, a Lower Pole Study Group wasconvened in the United States to determinethe optimal treatment of lower pole stones.21

They performed a multicenter, prospective,randomized trial investigating the treatmentof lower pole stones with PCNL or SWL.Results showed that stone free rates for low-er pole PCNL treated patients was 95% com-pared with 37% for lower pole stones treat-ed with SWL (P<0.001). Furthermore, whenthis was stratified to stone size, the stone freerates for PCNL was 100% for stones less than10 mm and 91% for stones greater than 10mm. In contrast, the stone free rate for SWLdecreased from 63% for stones less than 10mm, to 21% for stones between 10 and 20mm and to 14% for stones larger than 21 mm.They concluded that stone free rates for PCNLwere not dependent on stone burden andremains a more efficacious treatment for low-er pole stones greater than 10 mm.

More recently, ureteroscopy (URS) hasbecome an acceptable alternative to SWL andPCNL for lower pole stones. In 2005, a secondphase of the Lower Pole Study Group was ini-tiated to compare URS and SWL for the treat-ment of 1 cm or less lower pole stone.22 Thestudy postulated that URS would improveSWL outcomes without having significantpatient morbidity. Although the URS grouphad better outcomes, the study was under-powered and did not show any statisticallysignificant differences in stone free ratesbetween the two groups. In fact, SWL showedgreater patient acceptance and shorter con-valescence. Consequently, URS was not rec-ommended as an alternative to SWL forstones 1 cm or less in the lower pole.

TABLE I.—Guidelines of the European Association ofUrology.27-29

Indications for PCNL— Large stone burden >2 cm or 1.5 cm for lower caly-

ceal stones— Staghorn stones— Stones that are difficult to disintegrate by ESWL (cal-

cium-oxalate monohydrate, brushite, cystine)— Stones refractory to ESWL or ureteroscopy— Urinary tract obstructions that need simultaneous

correction (e.g. UPJ obstruction)— Malformations with reduced probability of fragment

passage after ESWL (e.g. horseshoe or dystrophickidneys, calyceal diverticula)

— Obesity

UPJ: urinary pelvic junction; ESWL: extracorporeal shock wavelithotripsy.

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Preoperative evaluation

Patient selection and preoperative plan-ning are important to achieve a successfuloutcome in PCNL. The absolute contraindi-cations are uncorrected coagulopathy,untreated urinary tract infection (UTI), andpyonephrosis.30 The generally accepted rec-ommendations include actively treating UTIsince patients with infected urine from therenal pelvis or infected renal stones havebeen shown to have a fourfold greater risk ofdeveloping urosepsis.23 This may involve theuse of prophylactic antibiotics as it has beenreported to reduce the risk of infectious com-plications even in cases of sterile urine andnoninfectious calculi.31 Mariappan et al. foundthat a one week course of ciprofloxacin pri-or to PCNL significantly reduced upper uri-nary tract infection and urosepsis.32 They alsoextended the indications to patients withstones greater than 2 cm or kidneys withassociated hydronephrosis.33 If purulent urineis found at the time of puncture, PCNL shouldbe postponed and a nephrostomy tube insert-ed to avoid the risk of urosepsis.30

Preoperative evaluation also includes acomplete blood count, coagulation profile,blood sugar determination, blood group andscreen, and anesthetic review if warranted. Tominimize the risk of bleeding, correctablehematological conditions should be under-taken and treated (such as withholdingantiplatelet agents in conjunction with thepatient’s primary care physician). Kukreja etal. found that diabetes was one of severalrisk factors associated with increased bloodloss during PCNL.34 Turna et al. also had sim-ilar findings and suggested that arterioscle-rosis with thickened basement membranesin diabetics may increase the risk for bleed-ing.34, 35 For this reason, strict control andpreparation of patients with diabetes is rec-ommended prior to surgery.

Preoperative planning

Preoperative planning is essential in orderto identify the position and number of stones,assess the intrarenal collecting system archi-

tecture, and to evaluate the relationship ofthe kidney and its surrounding organs.36 Fourmodalities are in common use to image renalstones. They are plain radiograph (KUB),IVU, renal ultrasonography, and CT scan.

KUB X-ray

KUB X-ray is useful in determining if thestone is radio-opaque, which may then guidefurther therapy. Most calcium containingstones are visible on KUB provided they aresufficiently large, not obscured by overlyingfecal matter, and not overlying any bonystructures. Although KUB has the advantageof being rapidly acquired, readily availableand inexpensive, it has a reported low sen-sitivity of 58% and low specificity of 69% fordetecting kidney stones.37 Its use in preop-erative planning is limited due to its inabili-ty to delineate the kidney, the collecting sys-tem, and surrounding organs.38

Intravenous urogram

IVU in the past has been the standard imag-ing modality used in uroradiology but it isslowly becoming obsolete. It still remainsvaluable for the preoperative planning andevaluation of kidney stones due to its abilityto demonstrate fine detail in the collectingsystem anatomy of the kidney.39-41 A disad-vantage is that it does not provide informa-tion on 3-dimensional relationships of thestone to the kidney, or to adjacent visceralorgans. An example where this knowledgecould be useful preoperatively would be intreating stones situated in an anterior calycealdiverticulum, where alternative options intreatment may be better utilized.

CT scan

CT has become the gold standard in thediagnosis and evaluation of urolithiasis.42

Numerous studies have shown CT to be supe-rior to IVU for evaluating patients with flankpain.43-47 Studies have found the sensitivityand specificity of CT to range from 98-100%across all clinical scenarios 48 including inthe pediatric setting where CT detects 96 to100% of stones.49


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et al. show that the upper pole is drained bya single infundibulum in 100% of cases, themiddle calyces drained by two infundibuliin 89% of cases, and the lower pole drainedby either a single infundibulum (36%) or twoinfundibuli (64%).53 This has previously beencorroborated by Sampaio’s classic study onendocast models of the human renal col-lecting system.19 Therefore, when treatinginferior pole stones, the inferior calyceal sys-tem can have two distinct systems and entryinto one calyx may not allow access to theother lower pole calyx if required. Awarenessand having a careful considered approachwill help avoid this situation.

With patients in the prone position duringpuncture, the ideal access is one where theneedle enters a posterior calyx at the fornix,traversing the smallest amount of renalparenchyma and minimizing injury to largerrenal vessels.54 In contrast, direct punctureinto the anterior calyx will traverse more renalparenchyma and renders further access intothe collecting system difficult without exces-sive tract angulation, and result in morebleeding.

When using fluoroscopy in prone PCNL,access into the desired calyx is best achievedusing a “bull’s eye” technique as it allowscomplete control and direction of the needle,and subsequent tract placement. Initially theimage intensifier C-arm is in the vertical orzero degree position.52 A slow and carefulretrograde pyelogram with dilute contrast isperformed to opacify the collecting system.The posterior calyces are identified by rec-ognizing these calyces fill later and the con-trast is seen as less dense. Alternatively, withthe introduction of 10 cc of air using asyringe, these calyces preferentially outlinewith an air interface. Once the posterior calyxof interest has been identified, the imageintensifier is rotated 20° to 30° towards thesurgeon in the axial plane. This allows entrynear Brodel’s line which is relatively avascu-lar, due to the arterial network being end-arteries in this region. A 5-10° tilt in the cau-dal direction for lower pole access, or cranialdirection for upper pole access respective-ly, is added to allow for entry into the col-lecting system in the same direction as the


Aside from being used for the diagnosisof renal stones, CT delineates the extent, ori-entation, and location of the stones withinthe kidney, which can facilitate tract selectionfor PCNL. It also provides detailed informa-tion on the relationship of the collecting sys-tem to adjacent organs such as the colon, liv-er, or spleen thereby helping the surgeonavoid injury to these structures. In addition,the proximity of an upper pole calyx to thepleural space can be ascertained by CT, andintrathoracic complications anticipated oravoided altogether when doing PCNL if thetract is carefully planned beforehand.38

Recently, CT urography has benefited fromenhancements in newer technologies, andthe development of sophisticated three-dimensional CT reconstruction software. Thishas led to the creation of detailed three-dimensional CT images of the renal collect-ing system, thereby improving preoperativeplanning.50, 51 This allows accurate identifi-cation of the target calyx for safe puncture,along with the relationship to adjacent viscerato avoid complications. With three-dimen-sional reconstruction images, the kidney canbe rotated on its axes to identify anterior andposterior calyces to provide for accurate tractplacement. This information can be juxta-posed in the operating room by thoughtfulevaluation of the pyelogram or ultrasound(US) images at the time of puncture.

Technique of PCNL

Many techniques have been described forPCNL, including having the patient eitherprone, supine or a modification of the two. Adetailed description of our technique forPCNL has been described elsewhere.52

Obtaining optimal access is the key to achiev-ing efficient stone clearance with minimalmorbidity and requiring fewer ancillary pro-cedures.

Knowledge of the configuration of the pye-lo-calyceal system, the renal blood supply asit relates to the pyelo-calyceal system and itsvariations are a prerequisite for successfulPCNL outcome. Calyceal studies using 3-dimensional reconstructive CT by Al-Qahtani

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infundibular axis. This potentially causes lesstorque of the kidney and facilitates a nearbloodless tract. The tip of a hemostat is usedto mark the position on the skin overlyingthe selected calyx and a diamond tipped nee-dle introduced through this point. The nee-dle is advanced under fluoroscopic guidanceusing the hemostat clip as a holder, timinginsertion when the patient is in full expirationand in the same trajectory as the C arm posi-tion of the fluoroscopy unit providing a “bull’seye” effect (Figure 1). This effect is seen whenthe hub of the needle is in direct alignmentwith the needle, the calyx of interest and theaxis of the C-arm. Needle advancement isdone in one smooth motion and is carriedon until it just enters into the renal parenchy-ma, which is denoted by needle movementduring respiration. The C-arm of the fluo-roscopy unit is then tilted away from the ver-tical by 10° to provide depth perception

(Figure 2). The surgeon will now see the nee-dle in profile and the target calyx in front ofit. The tip of the needle is then advancedalong the same trajectory until it just pene-trates the calyx. The stylet is removed andentry into the collecting system is achievedusing an angled hydrophilic tipped guidewire.

The safest route for accessing the collect-ing system is directly into the fornix of a calyxand not the infundibulum, thereby avoidingthe larger blood vessels that are adjacent tothe infundibulum.55 Punctures into the col-lecting system that are too medial have ahigher risk of injury to segmental and inter-lobar branches of the renal artery. This hasbeen supported by studies from Sampaio etal. which showed that 67% of upper poleinfundibular punctures and 13% of lowerpole infundibular punctures respectively hadarterial injuries, whilst no arterial injury wasdetected when the puncture was made


Figure 1.—The “bull’s eye” effect. A) Start of PCNL. Stone at inferior pole with ureteric catheter at renal pelvis; B) retro-grade pyelogram; C) tip of hemostat overlying target calyx; D) with C arm rotated 300 towards surgeon, “bull’s eye” obtai-ned when axis of fluoroscopy (dotted lines) is in direct alignment with needle and hub; E) fluoroscopic image of “bul-l’s eye” effect during needle insertion; F) needle overlying target calyx and into renal parenchyma.

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Tract dilation

An important and integral aspect of PCNLis tract dilation, and access sheath insertion.There are currently three methods common-ly used: one step balloon dilation, Alken met-al reuseable telescoping dilators, and Amplatzsequential fascial dilators. In competenthands, all three methods are considered safe.However, higher blood loss has been asso-ciated with telescoping metal dilators versusAmplatz or balloon dilation.34 Studies haveshown the least amount of bleeding is asso-ciated with the use of balloon dilation whencompared to Amplatz fascial dilators.35, 58, 59

The reduced blood loss is thought to be dueto the constant pressure applied on the renalparenchyma during dilation before the sheathis advanced. The disadvantages are itsexpense and its non-reuseable nature. With


through the calyceal papilla.56 The posteriorsegmental artery is the most commonlyinjured artery during PCNL and needs to beavoided especially when performing inter-polar and upper pole punctures.57

For most patients, the inferoposterior calyxis ideal for initial access. However, whererenal anatomy and stone bulk dictates anupper pole access, puncture should be per-formed in full expiration to minimize pleur-al injury.45, 55 Access through the upper calyxprovides a straight line along the long axisof the kidney and gives excellent exposureand entry into the superior calyces, the renalpelvis, the lower calyces and proximalureter, often without the need for signifi-cant torque on the kidney during the pro-cedure which can result in excessive bleed-ing.38, 54, 55, 58, 59

Figure 2.—Needle in profile view. A) C-arm rotated 10° awayfrom surgeon to give needle depth perception; B) fluoroscopicimage of needle (*) in profile view with C-arm in the positionabove. Needle is then advanced up to target calyx under fluo-roscopic guidance.

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the Amplatz fascial dilating system, it hasbeen suggested that during sequential dilatorexchanges, the tamponade effect on the renalparenchymal tract is lost and this leads tomore blood loss during the exchange process.However, animal studies that have beenundertaken to compare the effects of bal-loon vs Amplatz fascial dilation showed nodifference between the two techniques. Onesuch study on porcine kidneys by Al-Kandariet al. showed that after 24 hours, Amplatzfascial dilated tracts were rounded and hadmore surface hemorrhage compared to bal-loon dilated tracts which were V shaped andhad less bleeding. However, after six weeksscar formation was minimal and similar insize in both groups.60 With regards to theAlken dilators which have the advantage ofbeing reusable, centers using these have like-wise claimed minimal bleeding complica-tions when using this technique.61 The find-ings are that all three methods of tract dilation,when used appropriately, are associated withminimal bleeding and result in minimal scarformation on healing.54 One step balloondilators have become popular because of itsease of use, efficacy, and safety during tractplacement.

Lithotripsy devices

Presently, the four basic lithotripsy devicesin use today include ultrasonic, pneumatic,laser or electrohydraulic to achieve stonefragmentation.

The ultrasonic lithotripter works by elec-trical energy being transferred onto a piezo-electric crystal, resulting in a strong vibra-tional energy directed at the tip of a hollowmetal rod, which has the effect of grinding thestone into small sand like particles.62 Suctionis applied to the end of the probe to aid inparticle evacuation and cooling of the probethrough return flow of normal saline irrigantsolution during the procedure. For staghorncalculi, the typical probe size used is 3.5 mm.Due to its rigid nature, the probe must bepassed through an offset viewing nephro-scope that has a straight wide caliber work-ing channel.63

The pneumatic device (Swiss LithoClast®;

Electro Medical Systems, Nyon, Switzerland)uses a forced air activated rigid probe con-taining a metal projectile that fragments thestone.62-64 The probe sizes range from 0.8mm to 4 mm in diameter. The fragments needto be removed manually by the surgeon usinga combination of grasping forceps or stonebaskets. Recently a suction feature has beenbuilt into the pneumatic device (Lithovac®;EMS, Nyon, Switzerland) to facilitate theremoval of stone fragments with some suc-cess.

A combination of pneumatic and ultrasoniclithotripsy into a single handpiece with con-tinuous suction is available (LithoClast® Ultra,EMS, Nyon, Switzerland), and has been avery successful combination.62 Numerousauthors have compared ultrasonic lithotripsyalone with the LithoClast® Ultra (or Master),and found shorter operative times in the lat-ter group. In an in vitro study, Auge et al.found the combination device significantlymore efficient, achieving complete stone frag-mentation and clearance in 7.4 min as com-pared to 12.9 min and 23.8 min respectivelyfor either ultrasonic or pneumatic lithotrites(P<0.002). In the same study, the stone frag-ments were significantly smaller with thecombination device than with the ultrasonicor pneumatic lithotrites (1.67 mm vs 3.67 mmvs 9.07 mm, respectively, P<0.00001).65 Thisis corroborated in a clinical study wherePietrow et al. demonstrated that the combi-nation device was able to disintegrate andremove stones twice as rapidly as the stan-dard ultrasonic lithotrite (21.1 min vs 43.7min respectively, P=0.036).66

The most commonly used flexible lithotrip-sy device is the holmium:YAG (Ho:YAG) laserdue to its efficacy in breaking all stonetypes,67 whilst having a limited local effectin a fluid medium (0.4 mm) making itextremely safe to use. The tip of the laserfiber (200 or 360 microns) causes stonedestruction using a photothermal effect andrequires direct contact with the stone to causefragmentation.68 However, its use in PCNLremains limited when using rigid nephro-scopes due to the better efficiency of stonefragmentation with the currently availablealternative modalities. It is inefficient for


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(44%), and the belief obtaining own accessrequired significantly extra time (50%).70

In a study that compared complicationsand stone free rates between urologist-direct-ed vs radiologist-directed renal access,Watterson et al. reported a three-fold increasein access related complications and clinical-ly significant bleeding when access wasplaced by a radiologist.71 This was despitethe fact that 14% of patients in the urologist-directed access group required multiple tractscompared with no patients in the radiolo-gist-directed group. In addition, stone freerates were significantly lower at 61.1% forthe radiologist-directed group compared with85.7% in the urologist-directed group(P<0.05). An explanation given for this dis-crepancy is the goal of renal access is fun-damentally different; with perhaps the radi-ologist more intent only on gaining entry asfor kidney drainage and not necessarily focus-ing on placing the optimal tract to best treatthe stone.54 In situations when access isachieved by the radiologist, the urologistshould be closely involved regarding opti-mal tract selection.

Occasionally, fluoroscopy guided percu-taneous puncture alone is unsafe for patientswith unusual body habitus such as spinabifida or severe scoliosis since it cannot iden-tify adjacent bowel, liver or spleen at the timeof needle puncture. In these situations, CT-guided percutaneous access or US guidanceis potentially safer as the tract is placed undercontrolled conditions. Matlaga et al., report-ed that CT-guided access was required in 3%of patients within their series for retrorenalcolon, severe vertebral deformity or stones ina transplant kidney.72 After successful CT-guided access by an interventional radiologist,PCNL was completed safely by the urologistwithout undue morbidity.

Minimally invasive PCNL

Jackman et al. first described minimallyinvasive PCNL (MPCNL) and applied it onthe pediatric population.73 The techniqueinvolved dilation of the percutaneous tractto 11 F and resulted in stone free rates of85% at three months. MPCNL has been tried


stones greater than 2 cm diameter and istherefore unsuitable for the primary treat-ment of staghorn calculi.64 It does have a rolein flexible nephroscopy where the flexiblenature of the fibres allow stone destruction tobe undertaken even in difficult to reach partsof the collecting system.

Electrohydraulic lithotripsy (EHL) usesshock wave energy to treat urinary tractstones. The mechanism is a spark-gap dis-charge from the end of a flexible metal probesimilar to HM-3 SWL (Dornier MedTech,Munich, Germany), which results in com-pressive forces as well as cavitatory bubblesthat rapidly expand and collapse causingstone fragmentation.62, 63 The smaller 1.9 Fr or3Fr probes can be used via flexible endo-scopes and results in minimal loss of endo-scopic deflection. However, the disadvan-tage is that it causes more urothelial damagecompared with Ho:YAG laser as the energy isdisseminated over a longer distance up to 1cm.63 Because of these concerns, EHL hasgone out of favor with the advent of theHo:YAG laser. When deployed judiciously,it still remains a very effective tool in thearmamentarium in stone lithotripsy.

Interventional radiologist vs urologist acqui-red renal access

Percutaneous access is commonly per-formed by either the interventional radiolo-gist or urological surgeon. It is performedeither as a single-staged procedure in theoperating room or as a staged procedurewhere access is done at the radiology depart-ment, and the patient transferred to the oper-ating room afterwards. A survey of urologistpractice patterns in the United States revealedthat only 11% of those performing PCNL rou-tinely obtained percutaneous access them-selves.69 Reasons for this trend were cited tobe inadequate training, and the belief thatrenal access is a radiological procedure bestperformed by the interventional radiologist.Lee et al. found that only 27% of urologistscontinued to perform percutaneous accessdespite training during their residency pro-gram.70 Reasons given included the radiolo-gist had better equipment (61%), better skills

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on the adult population by several authors onthe basis of minimizing trauma, with the useof smaller working sheaths, and hence reduc-ing morbidity.73-75 The technique used inthese procedures is dilation of the percuta-neous tract to 13-14 F, after which a standard14 F ureteral access sheath is inserted, andnephroscopy effected with the use of an off-set pediatric cystoscope, or an 8 F semirigidureteroscope. These studies have showngood results with low morbidity, but theyrecommend that MPCNL was ideal in kid-neys where the stone burden was under 2cm2. In a Chinese study, MPCNL was com-plimented by multiple punctures in treatmentof large staghorn calculi with stone free ratesof 72% after the first session and 93% after asecond look procedure.75

There are several issues regarding MPCNLwhich need to be addressed. At present, thebenefit of a smaller diameter tract has notbeen supported by published data. The renalfunctional effects of nephrostomy tract dila-tions have been described in two previousstudies.76, 77 They found that even when tractdilation was carried out to 35 F-50 F, allnephrostomy tracts healed to a fine scar at sixweeks and with minimal effect on function.In an in vivo pig study, Clayman et al. foundthat the average overall amount of renal dam-age was only 0.15% of total measured renalcortical volume.77 In essence, there was noclinically significant difference in terms ofrenal damage caused by MPCNL or tradi-tional 30 F tract in PCNL.77, 78 There havebeen no randomized studies published inthe literature so far, which conclusively showa reduction in blood loss using smaller diam-eter tracts compared to using a 30 F tract.Overall, MPCNL appears to have the best util-ity in the pediatric population and stone bur-den limited to 2 cm.29

Fluoroscopy vs ultrasound guided percuta-neous access

Fluoroscopy is the more commonly usedimaging modality to gain needle access, how-ever US guidance is gaining acceptance andhas been popular in many centers, especial-ly in Europe.27 US guidance requires extra

equipment but is easily performed and hasbeen reported to be a factor in reducingpotential complications during PCNL.34, 61 Itprovides an extra dimension of safety byidentifying overlying bowel or other visceraduring needle insertion, making it especial-ly useful for ectopic and/or transplant kid-neys. For PCNL in the supine position, USguidance is an integral part of the proce-dure.79 It also decreases the exposure of thepatient, surgeon and operating room staff toionizing radiation. US guidance is also usefulin localizing non-opaque stones or when ret-rograde passage of a ureteral catheter to therenal pelvis is not performed or cannot beachieved. The limitations include difficultyin targeting a non-distended collecting sys-tem, poor image quality in obese patientsand use is highly operator dependent.Regardless of modality used to gain access,fluoroscopy is still required for subsequentpassage of guide wires, tract dilation, manip-ulation of stones and instruments within therenal tract, and overall successful comple-tion of PCNL.38

Multiple punctures vs single tracts

The main drawback to multiple puncturesis the belief that it can result in increasedblood loss.34, 35 Ganpule et al. compared stud-ies with multiple tracts versus a single tractPCNL and concluded that when necessary,multiple tracts are safe and may be neces-sary especially for large stone burden.80

Hegarty and Desai in their prospective study,noted that multiple tracts are highly effectivein the treatment of staghorn and other large-volume renal calculi with blood loss andcomplication rates comparable to PCNL hav-ing only a single percutaneous tract.81 Thesefindings are further supported by Aron et al.who presented their results of 121 treatedrenal units.82 In their series, when multipletracts were anticipated, all punctures weremade at the beginning with guide wiresplaced into the collecting system beforehand.They had a 15% blood transfusion rate (18 outof 121 patients), with an overall stone freerate of 84% after primary treatment. Theyconcluded that aggressive PCNL monothera-


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tence of urine leak from the NT site.88, 89

Maheshwari et al. in their study, used 9 Fpigtail NT and compared them with 28 F NTand found significantly decreased analgesicrequirements and duration of urine leak aftertube removal in the former group. No sig-nificant increase in complications were asso-ciated with its use.88

In a prospective, randomized study com-paring three groups: 20 Fr NT, 9 Fr pigtailcatheter (Cook Urological Inc., Spencer, IN,USA) and tubeless drainage; Desai and col-leagues demonstrated that the 9 Fr pigtailcatheter group had a significantly smallerrequirement for analgesia compared to thegroup with 20 Fr large bore nephrostomytubes (140 mg and 218 mg diclofenac sodiumrespectively, P<0.05), and had shorter dura-tion of urine leak (13.2 hours and 21.4 hoursrespectively, P<0.05).90 Tubeless drainagehad the lowest analgesic requirement, short-est hospital stay, and the lowest duration ofurine leakage from the percutaneous tract.In addition, no increase in complications wasobserved with the use of either pigtailcatheters, or tubeless drainage. The authorssuggested that the best application of smallcaliber catheters were in patients who could,but unlikely required further access, and whohad an uncomplicated PCNL (i.e. no mucos-al damage, single access, minimal bleeding,and no residual fragments). Conventionallarge bore nephrostomy drainage is reservedfor procedures with significant bleeding,infected stones, or major collecting systemperforations where reliable drainage is para-mount, or planned second look nephroscopyduring the same admission is likely to beundertaken.

Nephrostomy tube-free PCNL

The placement of a nephrostomy tube aftercompletion of PCNL has been well recog-nized as a standard procedure to providehemostasis, adequate urinary drainage andaccess for additional endoscopic procedures.However, some investigators have questionedthe need for it when patients have had anuncomplicated PCNL and the kidney isknown to be stone free. Wickham et al.91 in


py using multiple tracts is safe and effective,and should be the first option for very largerenal staghorn calculi.

Some investigators however, have advo-cated single punctures in the treatment ofstaghorn calculi and have achieved compa-rably high stone free rates. In 2002, Wongand Leveillee reported a stone free rate of95% using a single tract and flexiblenephroscopy during PCNL for cases ofstaghorn calculi, which avoided having todo multiple punctures.83 After initial stonedebulking, flexible nephroscopy withHo:YAG laser lithotripsy or atraumatic basketswere used to fragment or reach stones notaccessible with rigid instruments. Their meanoperative time was 2.9 hours and the meanblood loss was only 238 mL. Thus, the choicebetween multiple tracts vs single tract accessis individualized for each patient at the timeof surgery. Both options are safe, but multi-ple punctures are associated with a slightlyhigher risk of bleeding.

Recently, publications have demonstratedthe use of flexible pyeloscopy to visuallyguide needle puncture into the desiredcalyx.84-86 Flexible pyeloscopy allows visual-ization of needle entry into the calyx, andfacilitates directing the guidewire down theureter to secure access. Its main use would bein patients who are known to be difficult ingaining access, or have previously failedPCNL due to access related problems.

Mini-nephrostomy tube PCNL

There has been considerable discussionregarding size of drainage catheters on com-pletion of PCNL. Large bore nephrostomytubes (NT) 16-20 F have been used tradi-tionally and thought to be associated withsignificant patient discomfort requiring moreanalgesics, prolonged hospitalization andlonger persistent urine leak from the nephros-tomy site after tube removal.87, 88 Alternativestrategies to avoid these morbidities includethe use of smaller caliber NT or nephrostomytube-free PCNL.

Studies have been designed to investigatewhether the size of the NT correlates withthe degree of patient discomfort and persis-

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1984 was the first to report their experienceomitting the nephrostomy tube after PCNL,but the concept did not gain acceptance espe-cially after conflicting reports resulting in pro-longed hospitalization and pain.92 In 1997,Bellman et al. published his results of patientsundergoing tubeless PCNL and again chal-lenged the need for requirement of a NT fordrainage.87 In their series, all patients had anindwelling ureteral stent inserted in additionto an indwelling catheter instead of an NT.Exclusion criteria for this study included anoperative time of more than 2 hours, PCNLrequiring two or more tracts (the main exclu-sion criterion), significant perforation of thecollecting system, significant residual stoneburden, or significant postoperative bleed-ing. They found no major complications usingthis approach.87 Tube-free PCNL has severalpurported advantages including a reducedhospital stay, decreased patient discomfort,earlier return to normal activities, anddecreased hospital costs.87, 93 No consensusguidelines have been formulated in select-ing patients suitable for tubeless PCNL, butthe recommendations from various studiesare summarized in Table II.

Recently, several investigators have triedto extend the inclusion criteria by includingpatients with larger stones (>3 cm), or thosehaving moderate intraoperative bleeding.Hemostasis was initially achieved throughcauterization of the bleeding points in therenal parenchyma, or the application of fib-rin glue to seal the nephrostomy tract.93, 98 Iffibrin glue is used, it is instilled simultane-ously at the time of removing the sheath fromthe collecting system.

The main disadvantage with the use of fib-rin glue in the urinary tract is the unwantedformation of a cohesive mucoid gel on con-tact with urine, which may persist up to 5days.99 This raised concerns for a possiblelithogenic effect of this agent, especially inlight of a previous report by Eden et al.wherein they described a patient who devel-oped a stone in the renal pelvis after fibringlue was used for a retroperitoneal dismem-bered pyeloplasty.100 Gelatin matrix was alsoevaluated in the study by Uribe et al. and itremained as a fine colloidal suspension for asimilar period of time when also in contactwith urine.99 Because of the potential for col-lecting system obstruction and possible lith-ogenic effect, every effort must be made toprevent these materials from entering intothe collecting system if used.

Nephrostomy tube-free PCNL representsan ongoing evolution in the overall improve-ment in the technique of PCNL. It can resultin shorter hospital stays, decreased patientdiscomfort, earlier return to normal activi-ties, and possibly decrease costs. The mainconcerns of this approach at present timeinclude the necessity for an extra procedurefor the removal of the internal ureteral stent,an increase in treatment costs associated withthe use of biologic hemostatic agents, andthe potential for upper urinary tract obstruc-tion or stone formation associated with theuse of these agents.

Supine versus prone position

PCNL has traditionally been performedwith the patient in prone position. Howeverin the literature, PCNL in the supine positionis well known but has yet to gain widespreadacceptance. This approach was first describedby Valdivia et al. in 1987 and later reportedtheir extensive experience with this tech-nique over 11 years.79 The purported advan-tages of the supine position include: safergeneral anesthesia, ease in positioningpatients, ability to perform the procedureusing local anesthesia, whilst maintainingeasy access to the urethra and ureteral orificeshould a retrograde procedure be required.In over 500 cases, they reported no colon


TABLE II.—Inclusion criteria as reported by variousNephrostomy tube-free PCNL studies.

Inclusion criteria for tube-free PCNL— Patients with stones less than 3 cm in diameter 94

— Kidneys with normal renal function 90

— Kidneys with no previous operations 90, 95

— No renal or obstructive anomalies 96

— Operative time shorter than 2 hours 87, 97

— Subcostal approach 90

— No residual fragments 90, 96, 97

— One to two percutaneous access 90, 94

— No intraoperative complications 90, 94, 95

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achieved this routinely on selected patientsusing local anesthesia in the outpatientdepartment. Stone fragments could also beextracted at the same time using basketsplaced down the instrument channel.

Later, Pearle et al. compared non contrasthelical CT scan and KUB xray to flexiblenephroscopy in looking for residual stonesafter PCNL.104 They found the sensitivity andspecificity in detecting residual calculi was46% and 82% for KUB, and 100% and 62% forCT respectively. In their series, performingflexible nephroscopy only on those with pos-itive CT findings avoided unnecessary pro-cedures in 20% of their patients. They per-formed a cost analysis and found significantcost savings to the hospital if this approachwas adopted.104

Today, the most reliable test in detectingresidual stone fragments after PCNL is noncontrast helical CT scan with 1 to 2 mm axi-al slices because of its unsurpassed sensitiv-ity in detecting renal calculi.86 Although thesize cut off for clinically insignificant residualstones has never been firmly established,many consider this value to be 4 mm orless.105 This could require further reevaluationsince residual fragments previously consid-ered insignificant, may often result in patientmorbidity in the future with stone growthand obstruction.105

There have been no universal recommen-dations on the best postoperative surveil-lance regime. The guidelines adopted by ourgroup are a consensus of the current evi-dence in the literature. They include meticu-lous and thorough flexible nephroscopy atthe end of the PCNL in all patients; a largebore nephrostomy tube (18 F) is left in select-ed patients and a non contrast CT scan per-formed selectively after 24 hours to furtherassess for residual fragments. If the postop-erative CT scan shows no fragments or onlya few small fragments (i.e. <3 mm), thenephrostomy tube is removed. Because ofthe potential for edema of the ureter orureteropelvic junction as a result of PCNL,an antegrade nephrostogram is performedafter the procedure to assure adequatedrainage. When antegrade drainage is con-firmed, the nephrostomy tube is then


perforations or hydro-pneumothoraces. Majorhemorrhage requiring blood transfusionoccurred in only three patients. US guidedpercutaneous access is helpful, and the ante-rior calyces are the preferred sites of punctureby these authors as they are more accessi-ble. Direct comparison of the two techniqueswas evaluated by Shoma et al. in 2002 wherethey treated 53 patients supine and 77 proneand found 89% and 84% stone free raterespectively.101 The overall complication rateswere similar in both groups and none of thepatients experienced injury of adjacentorgans. Ng et al. also adopted the supineposition during PCNL and reported their find-ings on 62 patients.102 They achieved a pri-mary stone-free rate of 76%. One patient withmultiple tracts required an emergent nephrec-tomy for hemorrhage one week after the pro-cedure due to an accidental traction on oneof the nephrostomy tubes. Again, there wereno colon injuries in this series. The supineposition appears to be a safe alternativeapproach to gaining access into the collect-ing system. It appears to be associated withlow complication rates and comparable stonefree rates when performed in expert centers.

Postoperative evaluation: assessmentof stone free status

The primary objectives of imaging aftercompletion of PCNL are to identify residualstones and ensure patency in drainage of theupper urinary tract. Traditionally, KUB X-rayand plain nephrotomograms have been usedto look for the presence of residual frag-ments. Many studies have questioned thisapproach because of the low sensitivities indetecting residual fragments. A study byDenstedt et al. in 1991 compared plainabdominal radiographs and tomograms, toflexible nephroscopy in detecting residualcalculi. Using second look flexible nephrosco-py as the gold standard, they found that KUBand nephrotomograms had a false negativerate of 35% and 17%, respectively.103 Theyrecommended second look nephroscopy asthe gold standard for detecting residual cal-culi during the same hospital admission. They

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removed. If the postoperative CT scan showsany fragments larger than 3 mm, then thenext step is flexible nephroscopy under localanesthesia and treatment of the stones duringthe same admission if feasible.

Conclusions

PCNL remains a technique undergoing con-stant refinement which has resulted inimproved patient outcomes. It remains a chal-lenging operation requiring a good under-standing of the fundamental principles. It hasproven to be safe, effective and remains firstline treatment in the management of largekidney stones. The most important part ofthe procedure is tract placement and thisremains the key to having a successful out-come, denoted by having high stone-freerates and acceptably low patient morbidity.The improvements in rigid and flexible endo-scopic equipment, along with the use of ultra-sonic, pneumatic and Ho-YAG laser lithotrip-sy devices to fragment stones have beeninstrumental in achieving these good out-comes. The ultimate benefit of PCNL hasbeen shorter hospital stays, greater patientcomfort, and earlier return to normal activi-ties by patients compared to earlier tech-niques of open stone surgery. Furtherimprovements will continue to evolve andthis will ultimately result in better patient carein the future.

Riassunto

Stato dell’arte della nefrolitotomia percutanea neltrattamento della nefrolitiasi

I calcoli renali voluminosi (>2 cm) costituisconouna patologia frequente che affligge tutti i gruppi dipopolazione nel mondo e può esitare in gravi com-plicanze se non trattata. Il trattamento di questapatologia si è enormemente evoluto negli ultimi set-tanta anni con l’avvento della chirurgia mini-invasiva.Tra queste, riveste un ruolo fondamentale la nefrol-itotomia percutanea (PCNL). Essa ha comportato unariduzione della degenza ospedaliera, del dolore post-operatorio, e una più rapida convalescenza, rispettoai precedenti criteri della chirurgia tradizionale a cieloaperto. La PCNL è soltanto una delle molteplici

opzioni di trattamento mini-invasivo disponibili pertale patologia, ma rimane tuttora la più efficace intutti i gruppi di pazienti. Comunque, essa continua adessere una delle procedure in ambito urologico piùcomplesse, che se non effettuata in modo adeguato,può essere associata a gravi complicanze. Il per-fezionamento delle tecniche, il miglioramento delleattrezzature e l’incremento dell’esperienza clinicahanno consentito di migliorare i tassi di assenza direcidiva di calcolosi delle vie urinarie con una mor-bilità accettabile per il paziente. In questo articolo, gliautori presentano una revisione degli aspetti tecnici,i risultati e l’attuale ruolo della PCNL nel trattamentodi calcoli renali volumonosi.

Parole chiave: Nefrolitotomia, percutanea - Calcolosirenale - Chirurgia mini-invasiva.

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