Upper Urinary Tract
Percutaneous nephrolithotomy in super obese patients (body mass index ≥ 50 kg/m2): overcoming the challenges Mohamed Keheila, David Leavitt, Riccardo Galli, Piruz Motamedinia, Nithin Theckumparampil, Micheal Siev, David Hoenig, Arthur Smith and Zeph Okeke Smith Institute for Urology, Hofstra North Shore Long Island Jewish School of Medicine, New Hyde Park, NY, USA
Objective To analyse our experience with and the outcomes and lessons learned from percutaneous nephrolithotomy (PCNL) in the super obese (body mass index [BMI] ≥50 kg/m2).
Patients and Methods In this institutional review board approved study we retrospectively reviewed our PCNL database between July 2011 and September 2014 and identified all patients with a BMI ≥ 50 kg/m2. Patient demographics, peri-operative outcomes and complications were determined. Additionally, we identified a number of special PCNL considerations in the super obese that can maximize safe outcomes.
Results A total of 21 PCNL procedures performed on 17 super obese patients were identified. The mean patient age was 54.8 years, the mean BMI was 57.2 kg/m2 and the mean stone area was 1 037 mm2. Full staghorn stones were observed in six patients and partial staghorns in four patients. The mean operating time was 106 min and the mean haemoglobin
Introduction Obesity is a major worldwide health problem for both developed and developing nations [1,2]. It is highly associated with comorbidities such as diabetes mellitus, hypertension, hyperlipidaemia, sleep apnoea and metabolic syndrome, which itself is a risk factor for urolithiasis [3–5]. According to both the European Association of Urology and the AUA, percutaneous nephrolithotomy (PCNL) is the first-line treatment for renal calculi ≥2 cm [6,7]. Current European Association of Urology guidelines suggest that morbid obesity (body mass index [BMI] ≥40 kg/m2) is an indication for open or laparoscopic nephrolithotomy; however, most of the literature supporting this recommendation is more than a decade old. Moreover, open
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decrease was 1.2 g/dL. The overall stone-free rate was 87%. There were four total complications: two Clavien grade II, one Clavien IIIb and one Clavien IVb. We identified several special considerations for safely preforming PCNL in the suber obese, including using extra-long nephroscopes and graspers, using custom-cut extra long access sheaths with suture ‘tails’ secured to easily retrieve the sheath, choosing the shortest possible access tract, readily employing flexible nephroscopes, placing nephroureteral tubes rather than nephrostomy tubes postoperatively, and meticulous patient positioning and padding.
Conclusion With appropriate peri-operative considerations and planning, PCNL is feasible and safe in the super obese. Stone clearance was similar to that reported in previous PCNL series in the morbidly obese, and is achievable with few complications.
Keywords percutaneous nephrolithotomy, obesity, renal stones
and laparoscopic renal stone surgery also present considerable challenges in the morbidly obese [7,8]. Previous studies have shown that PCNL in the obese (BMI ≥ 30 kg/m2) and morbidly obese has acceptable stone-related outcomes with relatively low intra- and postoperative complications [9–12]; however, there can be substantial differences in the anatomy of an obese vs super obese patient, and such differences can render the standard PCNL instruments and techniques unfit for percutaneous stone removal in the latter. As obesity is already rampant in developed nations, and forecast to become a global epidemic in the near future, we anticipate an increased number of super obese patients with complex nephrolithiasis in need of treatment [2]. To this end, we describe the feasibility of and our experience with PCNL in super obese patients, with a particular
© 2015 The Authors BJU International © 2015 BJU International | doi:10.1111/bju.13155 Published by John Wiley & Sons Ltd. www.bjui.org
Percutaneous nephrolithotomy in super obese patients
focus on the technical and anatomical considerations (Figs 1 and 2).
Fig. 2 Non-contrast abdominal CT image (axial view) of the same patient as in Fig. 1.
Patients and Methods After obtaining institutional review board approval, we retrospectively reviewed our PCNL database and identified all super obese (BMI ≥ 50 kg/m2) patients. All the procedures were performed with the patient in the prone position, which is our institutional preference, by a single experienced, fellowship-trained endourologist (Z.O.). In conjunction with our anaesthesiologist, meticulous attention was paid to proper patient positioning, and adequate additional padding was used as needed to avoid compressive neuromuscular injuries. Extra padding was placed under the chest and pelvis to allow adequate respiratory excursions. In all cases, the urologist performed renal calyceal punctures under fluoroscopic guidance using an 18-G diamond-tipped needle. Serial Amplatz fascial dilators (Cook Medical, Bloomington, IN, USA) were used to create a 30-F access tract. Extra-long Amplatz renal access sheaths were routinely used and custom-cut long enough to allow an adequate percutaneous tract length but not so long as to impede the use of the nephroscope. In cases with very long skin-to-stone distances, the tract was cut near-flush to the skin surface. When needed, Fig. 1 Non-contrast abdominal CT image (sagittal view) showing 53-yearold female patient, with a body mass index of 73 kg/m2, a right staghorn calculus and skin-to-stone distance of ~16 cm.
sutures with long tails were secured to the distal end of the sheath to provide a straightforward means for retrieval in instances where the sheath migrated subcutaneously (Fig. 3). Extra-long nephroscopes (Karl Storz, Tuttlingen, Germany; 25 cm length [Fig. 4]) and instruments were used as necessary, based on the tract length and patient anatomy. Determination of the skin-to-stone distance on preoperative CT helped with operative planning and allowed the surgeon to request extra-long instruments ahead of time to prevent intra-operative delay. A combined ultrasonic lithotripter with built-in suction capability (CyberWandTM dual ultrasonic lithotriptor; Olympus, Tokyo, Japan) was used for stone fragmentation. Postoperative renal drainage was accomplished using 24-F nephroureteric tubes. All patients underwent flexible nephroscopy and antegrade nephrostography as part of the PCNL. Operating times recorded included placement of the retrograde ureteric catheter, repositioning the patient to prone position, percutaneous access, stone extraction and nephrostomy drain placement. Postoperative stone-free rates were determined with non-contrast CT or renal ultrasonography within 5 months of surgery. Stone clearance was defined as no residual stones seen on postoperative imaging. Postoperative complications were reported according to the modified Clavien–Dindo classification system as applied to PCNL [13,14]. Complications were further classified as minor (Clavien I and II) or major (Claiven IIIa–V).
Results A total of 17 super obese patients were identified and underwent a total of 21 PCNL procedures between July 2011 © 2015 The Authors BJU International © 2015 BJU International
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Fig. 3 Access sheath shown flush to the skin with two suture tails secured
Table 1 Patient demographics.
to it, allowing the sheath to be pulled back when it migrates. Procedures, n Patients, n Mean age, years Gender, n Male Female Laterality, n Left Right Mean (range) BMI, kg/m2 Comorbidities, n (%) Diabetes mellitus Hypertension Hyperlipidaemia Coronary artery disease Congestive heart failure Chronic renal insufficiency (estimated GFR 1 tract Mean haemoglobin decrease, g/dL Mean estimated blood loss, mL Operating time; mean, min Mean hospital stay, days Fluoroscopy time: mean, min Stone-free, n* After single PCNL When including second stage PCNL Number requiring second stage
1 037 33.0 6 5 5 1
(35) (29) (29) (6)
4 6 14 7 1.2 165 106 4.5 8.1 13/15 11 13 4
PCNL, percutaneous nephrolithotomy. *Follow-up imaging available for 15 patients.
and September 2014. This represents ~5% (21/433) of the PCNL procedures performed in our centre during the same period. Baseline patient demographics and clinical data are shown in Table 1. The mean (range) BMI was 57.2 (50–71.3) kg/m2 and the mean (range) patient age was 54.8 (30–71) years. Eleven of the patients were women and five procedures were performed on the right kidney. The mean stone burden was 1 037 mm2 and the mean largest stone diameter was 33 mm (Table 2). Six PCNL procedures
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were performed for full staghorn stones and four for partial staghorn stones. The most common predominant stone type was uric acid (six patients), followed by calcium phosphate (apatite; five patients), calcium oxalate (five patients) and struvite (one patient). Ten patients had a history of UTIs, four of which were associated with urosepsis. The interpolar calyx was most commonly accessed (n = 11), followed by the lower (n = 6) and upper poles (n = 4). Fourteen procedures were performed through a single tract, six were performed through two tracts and one procedure required three tracts. The mean operating time was 106 min and the mean hospital stay was 4.5 days.
Percutaneous nephrolithotomy in super obese patients
Table 3 Complications.
of the maximum weight limitations of certain lithotripter tables.
Complications, n Clavien II Clavien IIIb Clavien IVb
2 (UTIs) 1 (angioembolization) 1 (sepsis requring intensive care unit)
Postoperative imaging was available for 15 patients, including renal ultrasonography in six patients and CT in nine patients. Eleven patients were stone-free after a single PCNL. Of the remaining four patients, one had a 6-mm residual fragment and opted for observation while the remaining three underwent second-stage PCNL during the same hospitalization. Two of these three were deemed completely stone-free after the second stage PCNL, while a 4-mm residual fragment in the third patient was observed. Thirteen (87%) patients achieved complete stone-free status. Complications are listed in Table 3. Two major complications occurred: one patient required admission to the surgical intensive care unit for sepsis (Clavien IVb), and another required angioembolization for a delayed postoperative bleed (Clavien IIIb). Postoperative fever requiring antibiotics occurred in two patients (Clavien II). There were no pulmonary complications, nor rhabdomyolysis, bowel injuries or deaths.
Discussion A consequence of industrialization and adoption of westernized diets is that the worldwide prevalence of obesity is increasing. It is projected that by 2030, >50% of the world’s adult population will be overweight or obese [2]. Obesity has significant health impacts as it is strongly associated with diabetes mellitus, coronary artery disease, urolithiasis and, more recently, all-cause mortality [15,16]. No single aetiology is known to be fully responsible for the association between obesity and urolithiasis [17]; however, it is thought that changes in urine composition, including increased excretion of calcium, uric acid, oxalate and sodium may be contributing factors which are exacerbated in patients with metabolic syndrome [18]. Taken together, it can be anticipated that urologists everywhere will encounter morbidly and super obese patients with kidney stones more frequently. Obesity limits the available treatment options for kidney stones as well as increases the complexity associated with a given treatment method. Shockwave lithotripsy outcomes are consistently poor in obese, let alone super obese, patients for a variety of reasons, including difficulty with stone localization under fluoroscopic or ultrasonographic guidance and skin-to-stone distances greater than the focal length of available lithotripters [19]. Furthermore, in some instances shockwave lithotripsy may not be physically possible because
With advances in flexible ureteroscope design and manoeuvrability, ureteroscopy has been successfully and safely applied to renal stones up to 2 cm in size in morbidly obese patients [20]. Whenever feasible, ureteroscopy is an excellent technique, given its minimally invasive nature and the limited dependence of urinary tract anatomical variability on BMI. Some studies report acceptable outcomes with ureteroscopy in obese patients with large stones; however, multiple sessions are often necessary to achieve adequate stone clearance [21,22]. A small series has been associated with stone-free rates after a single treatment session in up to 60% of patients. [23], but the utility of this approach in larger and more complex stones is still limited. In the present cohort, 10 patients had partial or complete staghorn stones which would be inadequately treated even with multiple ureteroscopic sessions. A number of mainly retrospective studies have evaluated PCNL outcomes in obese and morbidly obese patients, although to our knowledge there are no reports on outcomes in the super obese [9–12,24–27]. Interestingly, the definition of morbid obesity varies, with some studies using BMI ≥ 35 kg/m2 as the threshold and others using BMI ≥ 40 kg/m2. All studies conclude that PCNL is ultimately safe and effective in such patients when appropriate instrumentation is available and the procedure is carried out by an experienced urologist and anaesthesiologist. There is, however, less uniformity in the reported outcomes of complications, stone-free rates, operating times and need for auxiliary procedures. Results from the PCNL Global Study [10] and from Faerber and Goh [28] suggested a higher complication rate (22.1 vs 6.5%), lower stone-free rate (65.6 vs ~79%), longer operating time (112 vs ~80 min) and more frequent need for auxiliary procedures (28.1 vs 12.4%) in the morbidly obese vs normal weight patients [10,28]. This contrasts with a number of other retrospective studies, which found no significant association in these variables with BMI [9,11,12,26,27]. The present study reports our single-centre experience with PCNL in super obese patients (BMI ≥ 50 kg/m2), and we are aware of no other such reports in this patient population. For the 15 patients with available postoperative imaging, complete stone clearance was achieved in 73% after a single PCNL, and increased to 87% when auxiliary procedures were included. Major complications occurred in two patients (11.7%). We believe these complications were dependent on the patient’s stone characteristics rather than their BMI. The patient who experienced sepsis requiring intensive care (Clavien IVb) had a struvite staghorn stone, commonly implicated in infection risk. Delayed haematuria requiring angioembolization occured in a patient with a BMI of 54 kg/m2. A single tract was used © 2015 The Authors BJU International © 2015 BJU International
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for stone clearance. There was no obvious factor which precipitated his bleeding, and with this rare complication it is difficult to identify causal factors. Overall, these outcomes and complications appear to be in keeping with the existing studies on PCNL in obese and morbidly obese patients. Ten patients (59%) had staghorn stones, which represents a high percentage but does seem consistent with the Global PCNL study in which the percentage of staghorn stones increased with increasing degree of obesity (normal weight 26%; obese 29.8%; morbidly obese 40.2%) [24]. Interestingly, in those 10 patients with staghorn stones, six stones were composed of 100% uric acid, one of 100% struvite, and the remaining three were predominantly apatite. In the entire cohort, stones at least in part were composed of struvite in only three patients. These findings are consistent with others showing an increasing prevalence of uric acid stones in obesity and a contemporary shift away from struvite composition as the main stone type in staghorn stones [29,30]. Although encountered infrequently, super obese patients pose considerable surgical and anaesthetic challenges, and over time more of such patients are likely to exist and require stone treatment. Extrapolating from the Global PCNL study and the present cohort in which a majority of the stones were partial or complete staghorn stones, PCNL will probably play a central role in the stone management of these patients. As a high-volume stone referral centre in the USA, we have performed PCNL in a number of super obese patients and, from this collective experience, have found several technical and procedural modifications to be helpful in maximizing safety and treatment success in super obese patients compared with the ‘standard’ PCNL in non-obese patients. Preoperative planning and medical optimization are paramount in super obese patients. Anaesthesiologists experienced with obese patients and prone positioning are preferred. Reduced lung functional residual capacity and total lung capacity, as well as reduced venous return from inferior vena cava compression may occur with prone obese patients [31–33]. We acknowledge that supine positioning has been suggested to have possible advantages for obese patients over prone positioning, including shorter operating times [34–37]; however this must be balanced with the loss of nephroscope manoeuvrability associated with supine PCNL, which can be troublesome in super obese patients, as nephroscope mobility is already greatly hampered by patient anatomy [38,39]. Furthermore, many contemporary series of PCNL in morbidly obese patients, including the present study, report no occurrences of respiratory compromise in these patients while prone or when repositioning from supine to prone, or vice versa [9,24]. Enlisting additional personnel for safe patient positioning is essential. Fastidious patient positioning and liberal use of
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foam or gel padding under all pressure points and between intertriginous areas (e.g. breast tissue, pannus) helps to reduce possible neuromuscular compression injuries. Additional bolsters underneath the chest and pelvis can help optimize respiratory mechanics. In addition, ensuring the operating table will accommodate the super obese patient’s weight and size is important. Instances in which the patient will not adequately fit on a single operating table can be overcome by securing two operating tables together, side-by-side. Successful percutaneous access in a morbidly obese patient is a major challenge on three levels. First, excessive soft tissue attenuates image quality which reduces the accuracy of identifying a target calyx. Second, as the skin-to-stone distance increases, percutaneously accessing the collecting system, dilating the tract and securing the tract become more challenging. Third, maintaining access is difficult because of the limitations on length of working sheaths, nephroscopes and working instruments. A number of preoperative considerations and instrument modifications can help overcome these challenges. It is important to choose the shortest possible access tract which allows the largest range of instrument manoeuvrability within the kidney. Extra-long access sheaths are available from a few different vendors and these can be custom-trimmed to completely cover the length of the access tract. Often, extralong rigid nephroscopes and graspers must be used with the extra-long access sheaths. If extra-long access sheaths are unavailable, an alternative is to place two 12–15-cm access sheaths in series along the tract. When extra-long rigid instruments are unavailable and standard-sized rigid instruments cannot access some or all of the collecting system, then flexible nephroscopes should be used. Widely incising the skin and subcutaneous tissue down to the muscular fascia to shorten tract length and facilitate precutaneous access, as reported in previous studies, was not necessary in any of the 21 PCNL procedures in the present series [40]. Nor was preoperatively placing a nephrotomy tube for at least 1 week and then subsequently using a flexible cystoscope through the mature tract to access the stone [41]. Securing access with suture ‘tails’ to the sheath as described by Nguyen and Belis [15] is recommended to easily retrieve the sheath if it migrates subcutaneously. Alternatively, the open jaws of a stone grasping forceps can be positioned just past the deep end of the access sheath or insertion of a Foley catheter through the sheath, with partial inflation of its balloon, can be used to retract the sunken sheath [42]. Routinely using flexible nephroscopy after rigid nephroscopy can provide better exploration of the collecting system, improve detection of residual fragments, and reduce the need for additional access tracts. Furthermore, retrograde passage of a ureteroscope can be used to help access portions of the
Percutaneous nephrolithotomy in super obese patients
collecting system not easily located through the percutaneous access tract. Finally, postoperative drainage is better achieved with percutaneous nephroureteric tubes rather than with nephrostomy tubes. The latter frequently dislodge in the super obese patient because of the long tract length and high mobility of the overlying skin relative to the kidney. The main limitations of the present study are its retrospective nature, small cohort size and non-uniform postoperative imaging to determine stone clearance. Given the relatively low volume of super obese patients with kidney stones any single centre may encounter, multi-institutional studies are needed to better understand the surgical outcomes and perioperative morbidity associated with PCNL in this select and highly challenging patient population. In conclusion, percutaneous nephrolithotomy in the super obese patient presents a number of anatomical and anaesthetic challenges. With an experienced anaesthesiologist and urologist, and incorporation of several technical and instrumental modifications, however, PCNL in the super obese patient is feasible with successful outcomes and few complications.
Conflict of Interest None declared.
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12 Kuntz NJ, Neisius A, Astroza GM et al. Does body mass index impact the outcomes of tubeless percutaneous nephrolithotomy? BJU Int 2014; 114: 404–11 13 Dindo D, Demartines N, Clavien PA. Classification of surgical complications: a new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg 2004; 240: 205–13 14 Tefekli A, Ali Karadag M, Tepeler K et al. Classification of percutaneous nephrolithotomy complications using the modified clavien grading system: looking for a standard. Eur Urol 2008; 53: 184–90 15 Nguyen TA, Belis JA. Endoscopic management of urolithiasis in the morbidly obese patient. J Endourol 1998; 12: 33–5 16 Flegal KM, Kit BK, Orpana H, Graubard BI. Association of all-cause mortality with overweight and obesity using standard body mass index categories: a systematic review and meta-analysis. JAMA 2013; 309: 71–82 17 Calvert RC, Burgess NA. Urolithiasis and obesity: metabolic and technical considerations. Curr Opin Urol 2005; 15: 113–7 18 Taylor EN, Curhan GC. Body size and 24-hour urine composition. Am J Kidney Dis 2006; 48: 905–15 19 Grasso M, Loisides P, Beaghler M, Bagley D. The case for primary endoscopic management of upper urinary tract calculi: I. A critical review of 121 extracorporeal shock-wave lithotripsy failures. Urology 1995; 45: 363–71 20 Andreoni C, Afane J, Olweny E, Clayman RV. Flexible ureteroscopic lithotripsy: first-line therapy for proximal ureteral and renal calculi in the morbidly obese and superobese patient. J Endourol 2001; 15: 493–8 21 Wheat JC, Roberts WW, Wolf JS Jr. Multi-session retrograde endoscopic lithotripsy of large renal calculi in obese patients. Can J Urol 2009; 16: 4915–20 22 Aboumarzouk OM, Somani B, Monga M. Safety and efficacy of ureteroscopic lithotripsy for stone disease in obese patients: a systematic review of the literature. BJU Int. 2012; 110(8 Pt B): E374–80 23 Cohen J, Cohen S, Grasso M. Ureteropyeloscopic treatment of large, complex intrarenal and proximal ureteral calculi. BJU Int. 2013; 111(3 Pt B): E127–31 24 Fuller A, Razvi H, Denstedt JD et al. The CROES percutaneous nephrolithotomy global study: the influence of body mass index on outcome. J Urol 2012; 188: 138–44 25 Pearle MS, Nakada SY, Womack JS, Kryger JV. Outcomes of contemporary percutaneous nephrostolithotomy in morbidly obese patients. J Urol 1998; 160(3 Pt 1): 669–73 26 Sergeyev I, Koi PT, Jacobs SL, Godelman A, Hoenig DM. Outcome of percutaneous surgery stratified according to body mass index and kidney stone size. Surg Laparosc Endosc Percutan Tech 2007; 17: 179–83 27 Tomaszewski JJ, Smaldone MC, Schuster T, Jackman SV, Averch TD. Outcomes of percutaneous nephrolithotomy stratified by body mass index. J Endourol 2010; 24: 547–50 28 Faerber GJ, Goh M. Percutaneous nephrolithotripsy in the morbidly obese patient. Tech Urol 1997; 3: 89–95 29 Daudon M, Lacour B, Jungers P. Influence of body size on urinary stone composition in men and women. Urol Res 2006; 34: 193–9 30 Viprakasit DP, Sawyer MD, Herrell SD, Miller NL. Changing composition of staghorn calculi. J Urol 2011; 186: 2285–90 31 Edgcombe H, Carter K, Yarrow S. Anaesthesia in the prone position. Br J Anaesth 2008; 100: 165–83 32 Brodsky JB, Oldroyd M, Winfield HN, Kozlowski PM. Morbid obesity and the prone position: a case report. J Clin Anesth 2001; 13: 138–40 33 Neligan PJ. Metabolic syndrome: anesthesia for morbid obesity. Curr Opin Anaesthesiol 2010; 23: 375–83 34 De Sio M, Autorino R, Quarto G et al. Modified supine versus prone position in percutaneous nephrolithotomy for renal stones treatable with a single percutaneous access: a prospective randomized trial. Eur Urol 2008; 54: 196–202
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35 Falahatkar S, Moghaddam AA, Salehi M, Nikpour S, Esmaili F, Khaki N. Complete supine percutaneous nephrolithotripsy comparison with the prone standard technique. J Endourol 2008; 22: 2513–7 36 Karami H, Mohammadi R, Lotfi B. A study on comparative outcomes of percutaneous nephrolithotomy in prone, supine, and flank positions. World J Urol 2013; 31: 1225–30 37 Al-Dessoukey AA, Moussa AS, Abdelbary AM et al. Percutaneous nephrolithotomy in the oblique supine lithotomy position and prone position: a comparative study. J Endourol 2014; 28: 1058–63 38 Duty B, Okhunov Z, Smith A, Okeke Z. The debate over percutaneous nephrolithotomy positioning: a comprehensive review. J Urol 2011; 186: 20–5 39 de la Rosette JJ, Tsakiris P, Ferrandino MN, Elsakka AM, Rioja J, Preminger GM. Beyond prone position in percutaneous nephrolithotomy: a comprehensive review. Eur Urol 2008; 54: 1262–9 40 Curtis R, Thorpe AC, Marsh R. Modification of the technique of percutaneous nephrolithotomy in the morbidly obese patient. Br J Urol 1997; 79: 138–40
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Correspondence: Mohamed Keheila, The Smith Institute for Urology, North Shore Long Island Jewish Medical Center, 450 Lakeville Road, Suite M41, New Hyde Park, NY 11042, USA. e-mail: [email protected] Abbreviations: PCNL, percutaneous nephrolithotomy; BMI, body mass index.
Percutaneous nephrolithotomy in super obese patients (body mass index ≥ 50 kg/m2): overcoming the challenges Mohamed Keheila, David Leavitt, Riccardo Galli, Piruz Motamedinia, Nithin Theckumparampil, Micheal Siev, David Hoenig, Arthur Smith and Zeph Okeke Smith Institute for Urology, Hofstra North Shore Long Island Jewish School of Medicine, New Hyde Park, NY, USA
Objective To analyse our experience with and the outcomes and lessons learned from percutaneous nephrolithotomy (PCNL) in the super obese (body mass index [BMI] ≥50 kg/m2).
Patients and Methods In this institutional review board approved study we retrospectively reviewed our PCNL database between July 2011 and September 2014 and identified all patients with a BMI ≥ 50 kg/m2. Patient demographics, peri-operative outcomes and complications were determined. Additionally, we identified a number of special PCNL considerations in the super obese that can maximize safe outcomes.
Results A total of 21 PCNL procedures performed on 17 super obese patients were identified. The mean patient age was 54.8 years, the mean BMI was 57.2 kg/m2 and the mean stone area was 1 037 mm2. Full staghorn stones were observed in six patients and partial staghorns in four patients. The mean operating time was 106 min and the mean haemoglobin
Introduction Obesity is a major worldwide health problem for both developed and developing nations [1,2]. It is highly associated with comorbidities such as diabetes mellitus, hypertension, hyperlipidaemia, sleep apnoea and metabolic syndrome, which itself is a risk factor for urolithiasis [3–5]. According to both the European Association of Urology and the AUA, percutaneous nephrolithotomy (PCNL) is the first-line treatment for renal calculi ≥2 cm [6,7]. Current European Association of Urology guidelines suggest that morbid obesity (body mass index [BMI] ≥40 kg/m2) is an indication for open or laparoscopic nephrolithotomy; however, most of the literature supporting this recommendation is more than a decade old. Moreover, open
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decrease was 1.2 g/dL. The overall stone-free rate was 87%. There were four total complications: two Clavien grade II, one Clavien IIIb and one Clavien IVb. We identified several special considerations for safely preforming PCNL in the suber obese, including using extra-long nephroscopes and graspers, using custom-cut extra long access sheaths with suture ‘tails’ secured to easily retrieve the sheath, choosing the shortest possible access tract, readily employing flexible nephroscopes, placing nephroureteral tubes rather than nephrostomy tubes postoperatively, and meticulous patient positioning and padding.
Conclusion With appropriate peri-operative considerations and planning, PCNL is feasible and safe in the super obese. Stone clearance was similar to that reported in previous PCNL series in the morbidly obese, and is achievable with few complications.
Keywords percutaneous nephrolithotomy, obesity, renal stones
and laparoscopic renal stone surgery also present considerable challenges in the morbidly obese [7,8]. Previous studies have shown that PCNL in the obese (BMI ≥ 30 kg/m2) and morbidly obese has acceptable stone-related outcomes with relatively low intra- and postoperative complications [9–12]; however, there can be substantial differences in the anatomy of an obese vs super obese patient, and such differences can render the standard PCNL instruments and techniques unfit for percutaneous stone removal in the latter. As obesity is already rampant in developed nations, and forecast to become a global epidemic in the near future, we anticipate an increased number of super obese patients with complex nephrolithiasis in need of treatment [2]. To this end, we describe the feasibility of and our experience with PCNL in super obese patients, with a particular
© 2015 The Authors BJU International © 2015 BJU International | doi:10.1111/bju.13155 Published by John Wiley & Sons Ltd. www.bjui.org
Percutaneous nephrolithotomy in super obese patients
focus on the technical and anatomical considerations (Figs 1 and 2).
Fig. 2 Non-contrast abdominal CT image (axial view) of the same patient as in Fig. 1.
Patients and Methods After obtaining institutional review board approval, we retrospectively reviewed our PCNL database and identified all super obese (BMI ≥ 50 kg/m2) patients. All the procedures were performed with the patient in the prone position, which is our institutional preference, by a single experienced, fellowship-trained endourologist (Z.O.). In conjunction with our anaesthesiologist, meticulous attention was paid to proper patient positioning, and adequate additional padding was used as needed to avoid compressive neuromuscular injuries. Extra padding was placed under the chest and pelvis to allow adequate respiratory excursions. In all cases, the urologist performed renal calyceal punctures under fluoroscopic guidance using an 18-G diamond-tipped needle. Serial Amplatz fascial dilators (Cook Medical, Bloomington, IN, USA) were used to create a 30-F access tract. Extra-long Amplatz renal access sheaths were routinely used and custom-cut long enough to allow an adequate percutaneous tract length but not so long as to impede the use of the nephroscope. In cases with very long skin-to-stone distances, the tract was cut near-flush to the skin surface. When needed, Fig. 1 Non-contrast abdominal CT image (sagittal view) showing 53-yearold female patient, with a body mass index of 73 kg/m2, a right staghorn calculus and skin-to-stone distance of ~16 cm.
sutures with long tails were secured to the distal end of the sheath to provide a straightforward means for retrieval in instances where the sheath migrated subcutaneously (Fig. 3). Extra-long nephroscopes (Karl Storz, Tuttlingen, Germany; 25 cm length [Fig. 4]) and instruments were used as necessary, based on the tract length and patient anatomy. Determination of the skin-to-stone distance on preoperative CT helped with operative planning and allowed the surgeon to request extra-long instruments ahead of time to prevent intra-operative delay. A combined ultrasonic lithotripter with built-in suction capability (CyberWandTM dual ultrasonic lithotriptor; Olympus, Tokyo, Japan) was used for stone fragmentation. Postoperative renal drainage was accomplished using 24-F nephroureteric tubes. All patients underwent flexible nephroscopy and antegrade nephrostography as part of the PCNL. Operating times recorded included placement of the retrograde ureteric catheter, repositioning the patient to prone position, percutaneous access, stone extraction and nephrostomy drain placement. Postoperative stone-free rates were determined with non-contrast CT or renal ultrasonography within 5 months of surgery. Stone clearance was defined as no residual stones seen on postoperative imaging. Postoperative complications were reported according to the modified Clavien–Dindo classification system as applied to PCNL [13,14]. Complications were further classified as minor (Clavien I and II) or major (Claiven IIIa–V).
Results A total of 17 super obese patients were identified and underwent a total of 21 PCNL procedures between July 2011 © 2015 The Authors BJU International © 2015 BJU International
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Fig. 3 Access sheath shown flush to the skin with two suture tails secured
Table 1 Patient demographics.
to it, allowing the sheath to be pulled back when it migrates. Procedures, n Patients, n Mean age, years Gender, n Male Female Laterality, n Left Right Mean (range) BMI, kg/m2 Comorbidities, n (%) Diabetes mellitus Hypertension Hyperlipidaemia Coronary artery disease Congestive heart failure Chronic renal insufficiency (estimated GFR 1 tract Mean haemoglobin decrease, g/dL Mean estimated blood loss, mL Operating time; mean, min Mean hospital stay, days Fluoroscopy time: mean, min Stone-free, n* After single PCNL When including second stage PCNL Number requiring second stage
1 037 33.0 6 5 5 1
(35) (29) (29) (6)
4 6 14 7 1.2 165 106 4.5 8.1 13/15 11 13 4
PCNL, percutaneous nephrolithotomy. *Follow-up imaging available for 15 patients.
and September 2014. This represents ~5% (21/433) of the PCNL procedures performed in our centre during the same period. Baseline patient demographics and clinical data are shown in Table 1. The mean (range) BMI was 57.2 (50–71.3) kg/m2 and the mean (range) patient age was 54.8 (30–71) years. Eleven of the patients were women and five procedures were performed on the right kidney. The mean stone burden was 1 037 mm2 and the mean largest stone diameter was 33 mm (Table 2). Six PCNL procedures
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were performed for full staghorn stones and four for partial staghorn stones. The most common predominant stone type was uric acid (six patients), followed by calcium phosphate (apatite; five patients), calcium oxalate (five patients) and struvite (one patient). Ten patients had a history of UTIs, four of which were associated with urosepsis. The interpolar calyx was most commonly accessed (n = 11), followed by the lower (n = 6) and upper poles (n = 4). Fourteen procedures were performed through a single tract, six were performed through two tracts and one procedure required three tracts. The mean operating time was 106 min and the mean hospital stay was 4.5 days.
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Table 3 Complications.
of the maximum weight limitations of certain lithotripter tables.
Complications, n Clavien II Clavien IIIb Clavien IVb
2 (UTIs) 1 (angioembolization) 1 (sepsis requring intensive care unit)
Postoperative imaging was available for 15 patients, including renal ultrasonography in six patients and CT in nine patients. Eleven patients were stone-free after a single PCNL. Of the remaining four patients, one had a 6-mm residual fragment and opted for observation while the remaining three underwent second-stage PCNL during the same hospitalization. Two of these three were deemed completely stone-free after the second stage PCNL, while a 4-mm residual fragment in the third patient was observed. Thirteen (87%) patients achieved complete stone-free status. Complications are listed in Table 3. Two major complications occurred: one patient required admission to the surgical intensive care unit for sepsis (Clavien IVb), and another required angioembolization for a delayed postoperative bleed (Clavien IIIb). Postoperative fever requiring antibiotics occurred in two patients (Clavien II). There were no pulmonary complications, nor rhabdomyolysis, bowel injuries or deaths.
Discussion A consequence of industrialization and adoption of westernized diets is that the worldwide prevalence of obesity is increasing. It is projected that by 2030, >50% of the world’s adult population will be overweight or obese [2]. Obesity has significant health impacts as it is strongly associated with diabetes mellitus, coronary artery disease, urolithiasis and, more recently, all-cause mortality [15,16]. No single aetiology is known to be fully responsible for the association between obesity and urolithiasis [17]; however, it is thought that changes in urine composition, including increased excretion of calcium, uric acid, oxalate and sodium may be contributing factors which are exacerbated in patients with metabolic syndrome [18]. Taken together, it can be anticipated that urologists everywhere will encounter morbidly and super obese patients with kidney stones more frequently. Obesity limits the available treatment options for kidney stones as well as increases the complexity associated with a given treatment method. Shockwave lithotripsy outcomes are consistently poor in obese, let alone super obese, patients for a variety of reasons, including difficulty with stone localization under fluoroscopic or ultrasonographic guidance and skin-to-stone distances greater than the focal length of available lithotripters [19]. Furthermore, in some instances shockwave lithotripsy may not be physically possible because
With advances in flexible ureteroscope design and manoeuvrability, ureteroscopy has been successfully and safely applied to renal stones up to 2 cm in size in morbidly obese patients [20]. Whenever feasible, ureteroscopy is an excellent technique, given its minimally invasive nature and the limited dependence of urinary tract anatomical variability on BMI. Some studies report acceptable outcomes with ureteroscopy in obese patients with large stones; however, multiple sessions are often necessary to achieve adequate stone clearance [21,22]. A small series has been associated with stone-free rates after a single treatment session in up to 60% of patients. [23], but the utility of this approach in larger and more complex stones is still limited. In the present cohort, 10 patients had partial or complete staghorn stones which would be inadequately treated even with multiple ureteroscopic sessions. A number of mainly retrospective studies have evaluated PCNL outcomes in obese and morbidly obese patients, although to our knowledge there are no reports on outcomes in the super obese [9–12,24–27]. Interestingly, the definition of morbid obesity varies, with some studies using BMI ≥ 35 kg/m2 as the threshold and others using BMI ≥ 40 kg/m2. All studies conclude that PCNL is ultimately safe and effective in such patients when appropriate instrumentation is available and the procedure is carried out by an experienced urologist and anaesthesiologist. There is, however, less uniformity in the reported outcomes of complications, stone-free rates, operating times and need for auxiliary procedures. Results from the PCNL Global Study [10] and from Faerber and Goh [28] suggested a higher complication rate (22.1 vs 6.5%), lower stone-free rate (65.6 vs ~79%), longer operating time (112 vs ~80 min) and more frequent need for auxiliary procedures (28.1 vs 12.4%) in the morbidly obese vs normal weight patients [10,28]. This contrasts with a number of other retrospective studies, which found no significant association in these variables with BMI [9,11,12,26,27]. The present study reports our single-centre experience with PCNL in super obese patients (BMI ≥ 50 kg/m2), and we are aware of no other such reports in this patient population. For the 15 patients with available postoperative imaging, complete stone clearance was achieved in 73% after a single PCNL, and increased to 87% when auxiliary procedures were included. Major complications occurred in two patients (11.7%). We believe these complications were dependent on the patient’s stone characteristics rather than their BMI. The patient who experienced sepsis requiring intensive care (Clavien IVb) had a struvite staghorn stone, commonly implicated in infection risk. Delayed haematuria requiring angioembolization occured in a patient with a BMI of 54 kg/m2. A single tract was used © 2015 The Authors BJU International © 2015 BJU International
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for stone clearance. There was no obvious factor which precipitated his bleeding, and with this rare complication it is difficult to identify causal factors. Overall, these outcomes and complications appear to be in keeping with the existing studies on PCNL in obese and morbidly obese patients. Ten patients (59%) had staghorn stones, which represents a high percentage but does seem consistent with the Global PCNL study in which the percentage of staghorn stones increased with increasing degree of obesity (normal weight 26%; obese 29.8%; morbidly obese 40.2%) [24]. Interestingly, in those 10 patients with staghorn stones, six stones were composed of 100% uric acid, one of 100% struvite, and the remaining three were predominantly apatite. In the entire cohort, stones at least in part were composed of struvite in only three patients. These findings are consistent with others showing an increasing prevalence of uric acid stones in obesity and a contemporary shift away from struvite composition as the main stone type in staghorn stones [29,30]. Although encountered infrequently, super obese patients pose considerable surgical and anaesthetic challenges, and over time more of such patients are likely to exist and require stone treatment. Extrapolating from the Global PCNL study and the present cohort in which a majority of the stones were partial or complete staghorn stones, PCNL will probably play a central role in the stone management of these patients. As a high-volume stone referral centre in the USA, we have performed PCNL in a number of super obese patients and, from this collective experience, have found several technical and procedural modifications to be helpful in maximizing safety and treatment success in super obese patients compared with the ‘standard’ PCNL in non-obese patients. Preoperative planning and medical optimization are paramount in super obese patients. Anaesthesiologists experienced with obese patients and prone positioning are preferred. Reduced lung functional residual capacity and total lung capacity, as well as reduced venous return from inferior vena cava compression may occur with prone obese patients [31–33]. We acknowledge that supine positioning has been suggested to have possible advantages for obese patients over prone positioning, including shorter operating times [34–37]; however this must be balanced with the loss of nephroscope manoeuvrability associated with supine PCNL, which can be troublesome in super obese patients, as nephroscope mobility is already greatly hampered by patient anatomy [38,39]. Furthermore, many contemporary series of PCNL in morbidly obese patients, including the present study, report no occurrences of respiratory compromise in these patients while prone or when repositioning from supine to prone, or vice versa [9,24]. Enlisting additional personnel for safe patient positioning is essential. Fastidious patient positioning and liberal use of
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foam or gel padding under all pressure points and between intertriginous areas (e.g. breast tissue, pannus) helps to reduce possible neuromuscular compression injuries. Additional bolsters underneath the chest and pelvis can help optimize respiratory mechanics. In addition, ensuring the operating table will accommodate the super obese patient’s weight and size is important. Instances in which the patient will not adequately fit on a single operating table can be overcome by securing two operating tables together, side-by-side. Successful percutaneous access in a morbidly obese patient is a major challenge on three levels. First, excessive soft tissue attenuates image quality which reduces the accuracy of identifying a target calyx. Second, as the skin-to-stone distance increases, percutaneously accessing the collecting system, dilating the tract and securing the tract become more challenging. Third, maintaining access is difficult because of the limitations on length of working sheaths, nephroscopes and working instruments. A number of preoperative considerations and instrument modifications can help overcome these challenges. It is important to choose the shortest possible access tract which allows the largest range of instrument manoeuvrability within the kidney. Extra-long access sheaths are available from a few different vendors and these can be custom-trimmed to completely cover the length of the access tract. Often, extralong rigid nephroscopes and graspers must be used with the extra-long access sheaths. If extra-long access sheaths are unavailable, an alternative is to place two 12–15-cm access sheaths in series along the tract. When extra-long rigid instruments are unavailable and standard-sized rigid instruments cannot access some or all of the collecting system, then flexible nephroscopes should be used. Widely incising the skin and subcutaneous tissue down to the muscular fascia to shorten tract length and facilitate precutaneous access, as reported in previous studies, was not necessary in any of the 21 PCNL procedures in the present series [40]. Nor was preoperatively placing a nephrotomy tube for at least 1 week and then subsequently using a flexible cystoscope through the mature tract to access the stone [41]. Securing access with suture ‘tails’ to the sheath as described by Nguyen and Belis [15] is recommended to easily retrieve the sheath if it migrates subcutaneously. Alternatively, the open jaws of a stone grasping forceps can be positioned just past the deep end of the access sheath or insertion of a Foley catheter through the sheath, with partial inflation of its balloon, can be used to retract the sunken sheath [42]. Routinely using flexible nephroscopy after rigid nephroscopy can provide better exploration of the collecting system, improve detection of residual fragments, and reduce the need for additional access tracts. Furthermore, retrograde passage of a ureteroscope can be used to help access portions of the
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collecting system not easily located through the percutaneous access tract. Finally, postoperative drainage is better achieved with percutaneous nephroureteric tubes rather than with nephrostomy tubes. The latter frequently dislodge in the super obese patient because of the long tract length and high mobility of the overlying skin relative to the kidney. The main limitations of the present study are its retrospective nature, small cohort size and non-uniform postoperative imaging to determine stone clearance. Given the relatively low volume of super obese patients with kidney stones any single centre may encounter, multi-institutional studies are needed to better understand the surgical outcomes and perioperative morbidity associated with PCNL in this select and highly challenging patient population. In conclusion, percutaneous nephrolithotomy in the super obese patient presents a number of anatomical and anaesthetic challenges. With an experienced anaesthesiologist and urologist, and incorporation of several technical and instrumental modifications, however, PCNL in the super obese patient is feasible with successful outcomes and few complications.
Conflict of Interest None declared.
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Correspondence: Mohamed Keheila, The Smith Institute for Urology, North Shore Long Island Jewish Medical Center, 450 Lakeville Road, Suite M41, New Hyde Park, NY 11042, USA. e-mail: [email protected] Abbreviations: PCNL, percutaneous nephrolithotomy; BMI, body mass index.
