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Percutaneous nephrolithotomy for 1-2 cm lower-pole renal calculi

Objectives:Objectives: The most appropriate management of patients with lower-pole calyceal (LC) stones remains controversial. In this review we discuss the role of percutaneous nephrolithotomy (PCNL) in the management of LC stones 1(cid:150)2 cm in maximum dimension. Materials and Methods: Materials and Methods: A detailed literature review was performed to summarize the recent technical developments and controversies in PCNL. The results of PCNL for 1-2 cm LC calculi were reviewed. Results:Results: PCNL is increasingly employed as a primary modality in the treatment of LC calculi. It has a high success rate and acceptably low percentage of major complications in experienced hands. Supine position is found to be as safe and effective as prone position. Urologist-acquired access is associated with fewer access-related complications and better stone-free rates. Ultrasound is increasingly employed as an imaging modality for obtaining access. There have been increasing reports of tubeless PCNL in the literature. Most patients undergoing tubeless PCNL do not need hemostatic agents as an adjuvant for hemostasis. Non-contrast computed tomography does not yield statistically valuable increase in the diagnosis of signi (cid:222) cant residual stones compared with that of plain X-ray and linear tomography. Comprehensive metabolic evaluation and aggressive medical management can control new stone recurrences and growth of residual fragments following PCNL. Conclusions:Conclusions: PCNL highly effective procedure with consistently high stone-free rates when compared with extracorporeal shockwave lithotripsy or retrograde intrarenal surgery. The results also do not depend on anatomic factors and stone size. It is associated with low morbidity in experienced hands.


INTRODUCTION
The most appropriate management of patients with lower-pole calyceal (LC) stones remains controversial. The preferred approaches are extracorporeal shockwave lithotripsy (SWL) for stones < 1 cm and percutaneous nephrolithotomy (PCNL) for those > 2 cm. [1] For stones 1-2 cm in size, there is a decline in the use of SWL with a parallel increase in use of PCNL and retrograde intrarenal surgery (RIRS), since they are associated with better stone-free rates. [1][2][3] After >30 years of worldwide experience, PCNL remains a milestone technique in the field of endourology with a high success rate and acceptably low percentage of major complications. [4] The success of PCNL for treatment of LC calculi dose not depend on the anatomic factors that usually affect the outcome of SWL and RIRS. [5] It is also almost independent of stone size. [6,7] Larger the stone the more efÞ cient is its percutaneous removal. In this review we discuss the recent technical development in PCNL and its role in the management of LC stones 1-2 cm in dimension.

METHODOLOGY OF REVIEW
Pub-med search was performed in June 2008 using the terms "lower calyx, renal calculi, PCNL, complications, management, technique, percutaneous access." Titles and/ or abstracts were reviewed to determine relevance to this article. Only articles discussing the recent technical developments in PCNL and its role in the management of LC stones 1-2 cm in dimension were included in this review.

INDICATIONS
Indications of treating LC calculi are the same as those for stones located in other locations and include increasing size, localized obstruction, associated infection, hematuria and chronic or acute pain. [6] Asymptomatic renal stones larger than 1 cm in size are associated with a 47% risk of developing a symptomatic episode within two years if left untreated. Hence, prophylactic therapy is advisable for stones > 1 cm in size. [6] The only absolute contraindications for PCNL are untreated coagulopathy and pyonephrosis.

Position: prone vs. supine
The prone position is accepted globally due to its familiarity, excellent understanding of the anatomy in this position, and reduced risk of visceral complications. However, the supine position is preferable particularly in morbidly obese patients and in those with cardiorespiratory compromise and stature deformity. It is found to be as safe and effective as the prone position. The major technical disadvantage of the supine position is in accessing the upper calyx. [8,9] Imaging: fluoroscopy vs. ultrasound Access to the pyelocaliceal system is routinely performed using ß uoroscopic guidance. However, there is an increasing use of ultrasound for gaining access during PCNL. Till date, no survey has been undertaken to know the percentage of centers that prefer ultrasound for obtaining percutaneous access. It is proposed that ultrasonography provides a real time three-dimensional monitoring of the puncture, thereby minimizing the chances of segmental artery injury and decreasing the blood loss during the procedure. [10] In a randomized control trial Basiri et al., found ultrasoundguided access an acceptable alternative to fluoroscopy guidance and was associated with lower radiation exposure. Its success and complication rate were comparable to those of ß uoroscopy-guided PCNL. [11] Access: Urologist vs. Radiologist The success and complications of PCNL seem to be directly related to the ability to achieve optimal access. A survey from the US conducted in 2003 showed that only 11% of urologists performing PCNL routinely obtain percutaneous access themselves. [12] The reason for this trend may include lack of training, comfort level and perceived need of radiological involvement. However, urologists are increasingly obtaining access themselves because this eliminates reliance on a second ''surgeon'' and increases ß exibility with respect to procedure timing and the location of the access tract. [13] Watterson et al., in a retrospective study comparing urologist-vs. radiologist-acquired access found that access-related complications were less and stone-free rates were improved during urologist-acquired percutaneous access. [14] Access: site and number The successful removal of stones requires accurate placement of percutaneous tract that provides direct access to the stone. Inferior calyceal stones are usually approached through the inferior calyx [ Figure 1]. However, in complex inferior calyceal calculi, complete clearance may not be possible through a single tract in the inferior calyx because of problems in negotiating the acute angles between the calyces [15] [Figures 2 and 3]. Aron et al., compared the outcome of upper pole access vs. lower pole access for treating complex lower-pole calculi. They found that upper pole access provided faster and better stone clearance with a single puncture, and was associated with less requirement of a second-look procedure. [15] Multiple percutaneous tracts (Y-tract) might be required in some patients with complex LC calculi. This aggressive approach is highly effective in achieving stone clearance but at the cost of increased blood loss. [8,10,16] On the contrary, Hegarty et al., found that the blood loss and complication rates in PCNL with multiple tracts are comparable to those of PCNL incorporating a single percutaneous tract. They found a signiÞ cant rise in serum creatinine and drop in creatinine clearance in patients needing multiple tracts. [17] Post-PCNL drainage Routine placement of nephrostomy tube after an uncomplicated PCNL is being seriously questioned. Since its initial description in 1997, there have been increasing   reports of tubeless PCNL in the literature. [18] In this, the percutaneous nephrostomy is replaced by indwelling ureteral stent or a ureteric catheter at the end of an uncomplicated PCNL. [9,18] It is based on the principle that simple closure of tract with a dressing or parietal suture creates a closed retroperitoneal compartment, which is ideal for achieving self-tamponade. This corresponds to a clamped nephrostomy tube. [19] There are also a few case series on totally tubeless and stentless PCNL in properly selected patients. [20] To minimize or eliminate the risk of bleeding or extravasation after tubeless PCNL, a few authors have employed hemostatic agents in the nephrostomy tracts as an adjuvant to PCNL. [21,22] Borin et al., describe using haemostatic gelatin matrix (FloSeal; Baxter Inc., Irvine, CA) to provide hemostasis of the tract after tubeless PCNL. The authors occluded the collecting system at the level of entry of the Amplatz sheath with an occlusion balloon catheter, passed retrograde. FloSeal was then injected through the partially retracted Amplatz sheath while withdrawing the applicator and the sheath in tandem. The guide wire was withdrawn per urethra until its tip resided in the renal pelvis. A 36-cm, 7F tail stent was passed retrograde, and the skin closed with cyanoacrylate adhesive (Ethicon, Somerville, NJ). [22] However, in a randomized control trial employing haemostatic Þ brin sealant Tisseel TM after tubeless PCNL it was noted that instillation of haemostatic agents did not decrease postoperative bleeding or hemorrhagic complications but only resulted in less postoperative pain and a marginal decrease in hospital stay. The authors felt that most patients undergoing tubeless PCNL do not need these haemostatic agents and its associated cost.

ASSESSMENT OF STONE-FREE STATUS
Although most urologists agree that the goal of PCNL is to achieve stone-free status, the determination of stonefree status varies according to the diagnostic tool used. Historically, plain radiography was accepted as the standard method to judge residual stones following stone surgery. But recently, non-contrast computed tomography (NCCT) has proved to be the most sensitive tool for detecting residual stones after PCNL. The sensitivity for detection of residual fragments was 47.6% for plain radiographs Þ lms as judged by NCCT. [23] In spite of this, all the articles published on the efÞ cacy of PCNL for LC calculi have not employed NCCT scan to determine stone-free status [ Table 1]. NCCT may yield false positive results. There is a possibility of "over reading" with the rate reaching 15% after a secondary operation with ß exible nephroscopy. [24] A recent study also recommended that it should not be routinely performed in patients with opaque stones since it yields no statistically valuable increase in the diagnosis of signiÞ cant residual stones compared with that of plain X-ray and linear tomography. [25]

LONG-TERM OUTCOME AND STONE RECURRENCE AFTER PERCUTANEOUS NEPHROLITHOTOMY
Residual stone fragments after PCNL confer increased risk of future stone events. [26] Even when a stone-free status is achieved after PCNL, the underlying metabolic abnormalities remain. [7] Comprehensive metabolic evaluation and aggressive medical management can control active stone formation and growth in patients with or without residual stone fragments after PCNL. Kang et al., found that selective medical therapy signiÞ cantly decreased stone formation in stone-free and residual fragment groups after PCNL. Hence, they recommended medical management following PCNL without regard to stone-free status. [27] Krambeck et al., recently published an article on long-term outcome following PCNL. [26] At 19 years follow-up, the stone recurrences were less frequent following PCNL compared to SWL (36.8% vs. 53.5%). PCNL was not associated with development of adverse medical events (new onset renal failure, diabetes mellitus and hypertension) compared with SWL and conservatively managed stone cases.

RESULTS OF PERCUTANEOUS NEPHROLI-THOTOMY FOR LOWER-POLE CALYCEAL STONE MANAGEMENT
In 1989, McDougal et al., were the Þ rst to compare the outcome of PCNL with SWL for LC calculi. They noted that PCNL was associated with higher stone-free rates than SWL (86.2 % vs. 54.3%). [7] Similar Þ ndings were noted by Netto et al., in their retrospective study comparing the outcome of 23 patients treated by PCNL with that of 24 patients treated by SWL. [28] However, since ESWL is a noninvasive procedure without the need for routine anesthesia and hospitalization, and with prompt return of the patient to a normal life they considered it to be the method of choice for treating LC stones less than 2 cm in diameter.
Later on, in 1994, Lingeman et al., reported meta-analysis of four series published on PCNL and 13 studies on SWL for LC calculi. [7] They found that overall stone-free rates after SWL were 59.2% and after PCNL were 90%. Among stones of 10 to 20 mm, the stone-free rates were 56% for SWL compared to 89 % for PCNL. On logistic regression analysis, they found that stone size did not affect the stone-free status amongst patients treated by PCNL. In their personal experience of 32 patients with LC calculi treated by PCNL, they had 100% stone-free rates. Because of the signiÞ cantly greater efÞ cacy of PCNL for LC calculi, particularly stones larger than 10 mm in diameter, authors questioned the appropriateness of SWL as an initial therapy for virtually all LC calculi. Based on their Þ ndings, they recommended PCNL as an initial approach to treat these stones. Cass AS reviewed published series of PCNL for lower pole nephrolithiasis and found that the stone-free rate was 70.5-100%, repeat treatment rates were 4-62.5%, the complication rates were 13-38%, and the hospital stay was 3.1 to 6.1 days. [29] Based on these findings, Albala et al., convened a multicentric lower-pole study group (Lower pole study 1) for a prospective multicentric randomized trial comparing the outcome of PCNL vs. SWL in treatment of < 3 cm LC calculi. [30] This study revealed that stone free rates for PCNL were signiÞ cantly better than for SWL (95% vs. 37%). Morbidity was low overall and did not differ signiÞ cantly between the groups. The stone-free rates of SWL were only acceptable for stones < 10 mm (63%). Due to this high degree of efÞ cacy and acceptable low morbidity, the lower pole study Group 1 recommended PCNL as an initial modality for treating calculi > 10 mm size. [30] Similar results were observed by other authors in the literature [ Table 1]. [31,32] Current ß exible ureteroscopes, intracorporeal lithotripsy devices and stone retrieval technology allow for the treatment of calculi located throughout the intra-renal collecting system. Although, difÞ culty in accessing lower-pole calculi, especially when the holmium laser Þ ber is utilized, may be encountered, RIRS is associated with 85% stone-free rates as assessed by intravenous pyelography or computerized tomography scan performed at three months. [33] Chung BI compared outcome of PCNL and Ureterorenoscopy (URS) for medium-sized renal calculi (1-2cm). [34] Out of 15 patients who underwent PCNL, seven had lower pole calculi. There were four patients with lower-pole calculi among 12 patients undergoing URS. The authors noted that overall stone-free rate with PCNL was 87% and that for URS was 67% as judged by postoperative KUB imaging. They found that the stonefree rates and complication rates for PCNL are higher, but In meta-analysis for 1-2 cm size stone, higher SFR for PCNL than SWL (89% vs. 56%) Havel D, 1998 [31] 73 RCS with SWL 1-2 72.5% -SFR for PCNL statistically better than SWL (72.5% vs. 44%) but with higher morbidity Albala DM, 2001 [30] 58* Multicentric < 3 cm 92% * 22% 29 prospective RCT 1-UTI, 3-ileus, 1-sepsis, Calculi > 1 cm are better (1-2 cm) of SWL vs. PCNL 2-hematoma, 1-obstruction, managed by PCNL than SWL 3-perforation, 1-BT, PCNL offers higher SFR 1-AV fi stula than SWL (95 % vs. 37%) Ziaee S, 2004 [39] 45 CS <2.5 cm 88% No major PCNL morbidity low if performed by skilled person Aron M, 2004 [15] 102

TREND IN MANAGEMENT OF LOWER CALYCEAL CALCULI
In a survey of American urologists conducted by Gerber et al., in 2003, two-thirds of the urologists preferred SWL for treating LC calculi of 1-2 cm size. PCNL was preferred by only 30% of urologists at that time. [1] However, approximately Þ ve years later, in a survey done by Bandi et al., the proportion of urologists preferring PCNL increased and more urologists preferred PCNL to SWL for managing LC calculi [ Table 2]. [1,2,41] PCNL is the most preferred modality for treating LC calculi with unfavorable anatomy in view of limited clearance of fragments after SWL.

LIMITATIONS TO WIDESPREAD ACCEPTANCE OF PERCUTANEOUS NEPHROLITHOTOMY
Although PCNL has high therapeutic success rates independent of stone size, the invasiveness and technically demanding nature limits its use. Similarly, it is perceived to be associated with major complications increasing the patient's morbidity.

Learning curve
PCNL is currently the most complicated stone surgery technique to teach. The steep learning curve is mainly related to obtaining renal access. A resident has to perform about 24 PCNL procedures to obtain a good proÞ ciency during the residency period. Competence at performing PCNL is reached after 60 cases and excellence is obtained at >100 cases. [13] Similar Þ ndings were observed by Allen et al. [34] Complications In 1993, Chibber PJ published his experience with 878 patients undergoing PCNL for large and staghorn calculi. [35] Although blood transfusion rate was 12%, only 0.7% patients needed angiography and embolization. The incidence of other complications was very low (urinary tract infection 1.4%; prolonged leak from nephrostomy site 1.3%, hydrothorax 0.5%, bowel Þ stula 0.1%). In a recently published large series of 1338 patients undergoing PCNL from Canada, the incidence of major complications was similarly low at 3.7%. [36] Tefekli et al., classiÞ ed complications in PCNL according to the modiÞ ed Clavein grading system and found that most of the complications were Grade 1 or 2. [37] Grade 3a complications (complications requiring surgical, endoscopic, or radiologic intervention without anesthesia) were seen in 6.6% patients and Grade 3b (complications requiring surgical, endoscopic, or radiologic intervention under anesthesia) occurred only in 2.8% patients. Lifethreatening complications (Grade 4) occurred in only 1.4% patients and mortality was observed in 0.1% cases.
In the current literature, most of the complications are clinically insigniÞ cant bleeding or fever. SigniÞ cant bleeding is reported in < 8%. Conservative treatment is successful in most cases; however, a 5-18% blood transfusion rate is reported in the literature. In a recent review, the frequency of major complications was 0.9-4.7% for septicemia and 0.6-1.4 % for renal hemorrhage requiring intervention. Access-related complications like pleural and colonic injury were also rare ranging between 2.3-3.1% and 0.2-0.8% respectively. [38] CONCLUSIONS PCNL is a highly effective procedure that may be performed in a diverse group of patients with consistently high stonefree rates when compared with SWL or RIRS. The results also do not depend on anatomic factors and stone size. It is associated with low morbidity in experienced hands. Today in the era of evidence-based medicine, patients should be informed about the available modalities of treatment and their efficacy and safety. Higher stone-free rates associated with PCNL should be stressed while discussing the treatment options with the patients. The appropriate procedure in a given patient should be weighed on a caseby-case basis.