Purpose: To investigate the influence of stone opacity in plain radiography on stone free rate and complications of percutaneous nephrolithotomy (PCNL). Materials and Methods: A number of 101 patients who underwent PCNL between July-September 2015 were prospectively included. Stone opacity was judged on preoperative plain Kidney-Ureter-Bladder X-ray. Stone free rate was evaluated two weeks after the operation by ultrasonography and KUB. Results: There were 61 patients with opaque stones and 40 patients with non-opaque stones. The age, body mass index, preoperative creatinine, history of stone surgery, and stone size was not statistically different between patients with opaque and non-opaque stones. Neither operation duration nor access numbers were statistically significant between opaque and non-opaque stones. The frequency of stone free patients in opaque stones and nonopaque stones were 55/61 (90) and 30/40 (75) respectively (P = .04) The magnitude of hemoglobin drop in opaque stones and non-opaque stones were 1.9 Â± 1.2 mg/dL versus 2.9 Â± 1.7 mg/dL (P = .005). Conclusion: The stone free rate is lower and the magnitude of bleeding is higher in PCNL of non-opaque stones when compared to opaque stones if rigid instruments are used for nephroscopy

Etemadian, M.

Kashi, A.H.

Maghsoudi, R.

Ranjbaran, A.

English

eprints Iran University of Medical Sciences

The Association of Stone Opacity in Plain Radiography with Percutaneous Nephrolithotomy Outcomes and ComplicationsRobab Maghsoudi, Masoud Etemadian*, Amir H Kashi, Alireza RanjbaranPurpose: To investigate the influence of stone opacity in plain radiography on stone free rate and complications of percutaneous nephrolithotomy (PCNL).Materials and Methods: A number of 101 patients who underwent PCNL between July-September 2015 were prospectively included. Stone opacity was judged on preoperative plain Kidney-Ureter-Bladder X-ray. Stone free rate was evaluated two weeks after the operation by ultrasonography and KUB. Results: There were 61 patients with opaque stones and 40 patients with non-opaque stones. The age, body mass index, preoperative creatinine, history of stone surgery, and stone size was not statistically different between patients with opaque and non-opaque stones. Neither operation duration nor access numbers were statistically significant between opaque and non-opaque stones. The frequency of stone free patients in opaque stones and non-opaque stones were 55/61 (90%) and 30/40 (75%) respectively (P = .04) The magnitude of hemoglobin drop in opaque stones and non-opaque stones were 1.9 ± 1.2 mg/dL versus 2.9 ± 1.7 mg/dL (P = .005).Conclusion: The stone free rate is lower and the magnitude of bleeding is higher in PCNL of non-opaque stones when compared to opaque stones if rigid instruments are used for nephroscopy. Keywords: nephrolithiasis; opacity; percutaneous nephrolithotomy; stone free rate.INTRODUCTION Percutaneous nephrolithotomy (PCNL) is the treat-ment of choice for large or otherwise complex renal or proximal ureteral stones(1). Since first de-scribed by Fernstrom and Johannson(2), several modi-fications have been described to improve the outcome of surgery or reduce its potential complications by optimizing its surgical steps, including patient posi-tion, puncture of the collecting system, dilation, guid-ance equipment, fragmentation modality, and exit strategy. Currently, fluoroscopic imaging is the most commonly used technique in PCNL for entry to the renal collecting system, checking for the proper place-ment of surgical tools, and locating residual stones.(3)The success in PCNL is recognized as stone-free rate (SFR) which is under influence of factors such as stone burden and location.(4) With the advent of retro-grade intrarenal surgery (RIRS), alternative options are available for patients less likely to benefit from PCNL. After completion of lithotripsy in PCNL, residuals are checked by nephroscopic inspection and by fluoroscop-ic imaging. Observing residual stones through fluor-oscopy is largely dependent on the visibility of stones on plain radiography (namely opacity). Stone opacity can also affect the outcome of ancillary procedures like shockwave lithotripsy which are employed to treat PCNL residuals.(5,6) Previous reports have evaluated the association of computed tomography (CT) Hounsefield units (HU) with PCNL success and complications. Few studies have evaluated the association of stone opaci-ty on KUB with PCNL success. This is important be-cause routine preoperative evaluations before PCNL in many centers include intravenous pyelography without routine use of CT scan. Furthermore, a preoperative KUB is obtained in many centers on the morning of operation. Therefore, opacity on KUB is more readily available for PCNL candidates than CT Hounsefield units. Furthermore, the association of CT HUs with stone opacity on KUB is not perfect and wide apart cut off points have been suggested in the literature.(7,8) The present study aimed to determine whether stone opacity determined in plain KUB influenced the out-comes and complications of the PCNL procedure to help make better treatment decisions before operation.PATIENTS AND METHODSBetween July 2015 and September 2015, 101 patients underwent PCNL at our institution by two endourology fellows. PCNL is typically done in our center for renal stones ≥ 2 cm, smaller stones refractory to ESWL, and large upper ureteral stones. All data were gathered pro-spectively. Preoperative data, operative characteristics and postoperative data were collected. According to our department protocol, every patient was evaluated before the procedure by urine analysis, complete blood count, serum creatinine level and coagulation assays. Preoper-ative imaging studies included intravenous pyelography and/or abdominal CT scan. Stone burden was calculat-ed based on stone surface area. Stones were categorized to opaque stones (visible on plain radiography) and non-opaque stones (non-visible on plain radiography).Our protocol for PCNL was the standard prone Hasheminejad Kidney Center, Iran University of Medical Sciences, Tehran, Iran.*Correspondence: Hasheminejad Kidney Center, Tehran, Iran. Postal code: 1969714713Tel: +2188644486, Fax: +21 88644497. E mail: masoud.etemadian@gmail.com.Received August 2016 & Accepted November 2016ENDOUROLOGY AND STONE DISEASEVol 13 No 06   November-December  2016   2899PCNL under fluoroscopic guidance as pre-viously reported(9) and is summarized below. Renal access was achieved under fluoroscopic guid-ance, preferably through the lower calyx, after injection of contrast medium through a 5F open-ended ureteral catheter placed by cystoscope. Tract dilation was per-formed using the one-shot method, and a 30 F Amplatz sheath was inserted. Nephroscopy was performed by 24F Wolf nephroscope. Pneumatic lithotripter (Swiss Master Lithoclast, EMS, Bern, Switzerland) was used for fragmentation of the calculi. Particles were extract-ed by suction or grasper. Two or three access tracts were created as needed in case of large and complex stones. Residual stones were evaluated by fluoroscopic imaging and rigid nephroscopy intraoperatively. At the end of operation, PCNL was typically terminated without in-sertion of nephrostomy tube (tubeless). A 4.8-F ureteral double-J stent was inserted for patients with a single kid-ney, pyonephrosis, pelvicaliceal system injury or signif-icant residual calculi. The Foley and ureteral catheters were removed 24 to 48 hours after the procedure. Dou-ble-J stent was removed 2 to 4 weeks after the operation. All patients were evaluated 2 weeks after surgery by ultrasonography (US),and/or unenhanced CT scan. In accordance with previous reports, stone free pa-tient was defined as the absence of residual fragments or observing residual fragment of < 4 mm.(10-12) Pa-tients with residual fragments were treated with oral medications after receiving their stone analysis data.Data were entered into SPSS ver. 22.0 software (Chi-cago, IL).  Comparison of numerical data between the two study groups was performed by independent samples t-test or Mann-Whitney as appropriate. Chi-square or fisher exact tests were used for comparison of categorical data across study groups. Statistical sig-PCNL success with stone opacity-Maghsudi et al.nificance was considered at two sided P-value <.05. RESULTSThe mean ± SD of patients’ age was 44.9 ± 13.7 years. 33 patients were female. History of diabetes and hyper-tension was positive in 8 and 27 patients respectively. 58 operations were performed on the left side. Trans-fusion was needed in 11 operations (6 operations in the opaque group and 5 operations in the non-opaque group). Postoperative fever defined by oral T > 38°C for > 24 hours was observed in 5 patients (3 patients in the opaque group and 2 patients in the non-opaque group). No case of pleural or bowel injury was observed. Patients’ and operations’ characteristics between pa-tients with opaque and non-opaque stones have been compared in Table 1.Table 1 illustrates that the relative frequency of stone free patients is higher in the group of patients with opaque stones compared to patients with non-opaque stones.Also, the amount of hemoglobin drop (preoperative he-moglobin – postoperative hemoglobin) in patients with non-opaque stones was higher than patients with opaque stones. (2.9 ± 1.7 mg/dL versus 1.9 ± 1.2 mg/dL, P = .005)DISCUSSIONOur study data simply reveals the inferior stone free rate of PCNL in case of non-opaque stones together with higher hemoglobin loss in these patients. Achiev-ing a high stone free rate together with minimizing complications are the main efficacy targets for PCNL. Recently, the use of RIRS for renal stones has been reported with a high success rate sometimes equal to PCNL.(13-15) Therefore, it is advisable to explore fac-tors that hamper the success of PCNL as alternative Table 1. Patients’ and operations’ data compared between patients with and without opaque stones.     Opaque stones; N=61 Non-opaque stones; N=40  P valueAge,years;  mean±SD    45.0±13.5  44.8±14.3   0.94Body mass index; mean±SD   26.9±4.4  26.8±3.8   0.93Preop creatinine, mg/dL; mean±SD   1.3±0.2  1.3±0.2   0.67History of PCNL or ESWL; N(%)   15 (25)  14 (35)   0.26History of open stone surgery; N(%)   10 (16)  7 (17)   0.88Stone surface area, cm2; mean±SD   4.7±4.2  4.8±4.2   0.95Stone location, N(%)         0.44Single calyx    7 (11)  5 (12) Pelvis     12 (20)  8 (20) Pelvis + single calyx    24 (39)  10 (25) Pelvis + ≥ 2 calices    18 (30)  17 (43) Operation duration, minutes; mean±SD  54±24  55±17   0.73Pelvicaliceal system injury; N(%)   9 (15)  7 (17)   0.71Access numbers, 1/2/3   53/5/2  35/5/0   0.57Preop hemoglobin, mg/dL; mean±SD  13.5±1.4  13.4±1.6   0.76Postop hemoglobin, mg/dL; mean±SD  11.5±1.6  10.5±1.4   0.001Stone free patients, N(%)   55 (90.2)  30 (75.0)   0.04Endourology and Stone Diseases   2900procedures are available in the tray of many centers. One study evaluated the association of CT HUs with SFR in PCNL.(16) They reported higher SFRs when CT HU exceeded 1000. SFR was lower in stones with HU < 1000 which includes both opaque and non-opaque stones in KUB. Flexible Nephroscopy was suggested to improve SFR in PCNL of renal stones with HU > 677 by Gucuk et al.(17) The HU suggested by Gucuk et al. is very near to the cut off point for opacity of re-nal stones in KUB that was proposed by Chua et al.(8) Many patients with renal stones undergo intravenous pyelography for preoperative evaluation as CT is not readily available in many countries or is expensive. Furthermore, a preoperative KUB is taken before the operation in many centers. We think that as fluorosco-py is the most commonly employed imaging modali-ty for PCNL for detection of residual fragments(3), the visibility of renal stones on fluoroscopy images can be more simply predicted on the preoperative KUB than CT images. The association of CT HUs with opacity on KUB has been previously investigated and reported by Chau et al.(7,8) In their first report, the authors suggest-ed HU> 498 as the best cut off point for determination of opacity on plain KUB. In their second study, HU > 630 was reported as the best cut off point. These cut off points were associated with a false negative or positive rate of up to 20%(7,8) simply implying the inaccuracy of CH HUs for determination of opacity on KUB images. Huang and colleagues studied ureteral stone visibility on plain radiography according to their characteristics in unenhanced CT. When the density of the stones ex-ceeded 800 in HU standards, all ureteral stones could be seen, whereas only 17% of the stones could be seen on plain radiography when the HU level was less than 200. These studies point to the fact that there is no strict cut point according to which visibility of plain radiography can be estimated by CT HUs but that there is a gray zone in which some stones with a certain CT HU are visible while some are invisible on pain radiography. As previ-ously indicated stone visibility under C-arm fluorosco-py in PCNL operating room is under the same physics of visibility in KUB. Therefore; visibility of residual stones can be predicted more accurately by their visibil-ity in KUB than their CT HUs. Prior studies on success in PCNL studies evaluated the association of success with CT HUs. Limited publications evaluated the success of PCNL with respect to stone visibility on plain KUB.(10)The reported SFR in PCNL of non-opaque stones are widely different in the published series. SFRs of 95% (for miniperc of radiolucent 1-2 cm lower cal-iceal stones)(11), 87% (pediatric radiolucent stones)(18), 91% (for PCNL of radiolucent 1-2 cm renal stones)(12), and 44% (for PCNL of radiolucent stones with average stone surface area of 693 mm2)(10) have been reported in the literature. Our study data also reveals the inferiority of SFR in patients with non-opaque renal stones. Part of this difference relates to stone size and PCNL technique (miniperc versus standard PCNL) and the use of rigid versus flexible instruments.Non-opaque stones on KUB are hard to trace in fluor-oscopic imaging and instillation of contrast agent into the collecting system is employed during access phase of PCNL to determine the size and location of radiolu-cent stones. The contrast agent is usually washed away during nephroscopy by irrigation fluid. Therefore it is practically improbable to detect non-opaque resid-uals by fluoroscopy at the end of operation although some alternative options exist like intraoperative ultra-sonography. Ultrasonography has long ago been used as a guide for access phase of PCNL operation or as the only method of imaging guidance in PCNL. Use of ultrasonography at the end of operation in case of radiolucent stones could probably increase stone free rate, however the overall sensitivity of US for detec-tion of renal stones is in the range of 24-81% in the reported series(19) and lower in non-opaque stones com-pared with opaque stones.(10) The success of intraoper-ative ultrasonography to detect stone residuals is also influenced by operative factors like the shadow of ac-cess sheath, hematoma around kidney and clots in the collecting system. For these reasons, to minimize the residue rates in patients with non-opaque renal stones, the routine use of flexible nephroscopy has been ad-vocated by Gucek et al. in a randomized clinical trial. (17) However, flexible nephroscopy is not available in some PCNL centers especially in the developing world. Another important finding of our study was the posi-tive correlation between stone opacity and hematocrit drop. We could not find previous reports on the asso-ciation of bleeding in PCNL and stone opacity. More blood loss in non-opaque stones can be possibly ex-plained by more manipulation and trauma to renal col-lecting system or renal parenchyma on entry site while looking for residual fragments with a rigid nephro-scope. Gucuk and colleagues reported more bleeding in case of stones with lower HUs but they used flex-ible instruments for detection of residual fragments. Recent clinical trials disclosed the efficiency of RIRS for treatment of renal stones even when stone size is larger than 2 cm or the stone is in the lower pole of kidney with success rates close to standard PCNL.(13-15) Few publications reported equal SFR for RIRS with respect to opacity.(20) Until further confirmato-ry data will be available, we think that RIRS can be suggested as an alternative method for treatment of small-medium sized non-opaque renal stones or for larger stones flexible nephroscopy should be at hand or the patients should be consulted about a higher probability of residual stones when standard PCNL is employed with only rigid nephroscopes. The study limitations include failure to use flexible in-struments as commented on in the discussion section which compromises generalization of results to centers with availability of these instruments. Furthermore, stone composition data was not part of the study proto-col, therefore it was not possible to comment on the role of stone composition with opacity and PCNL outcomes.CONCLUSIONSThe PCNL stone free rate in cases of radiolucent stones is lower and the magnitude of bleeding is higher if rigid instruments are used for nephroscopy. CONFLICT OF INTERESTThe authors reported no conflict of interest.REFERENCES 1. Basiri A, Nouralizadeh A, Kashi AH, et al. X-Ray Free Minimally Invasive Surgery for Urolithiasis in Pregnancy. Urol J. 2016;13:2496-501.PCNL success with stone opacity-Maghsudi et al.Vol 13 No 06   November-December  2016   2901 2. Fernstrom I, Johansson B. Percutaneous pyelolithotomy. A new extraction technique. Scand J Urol Nephrol. 1976;10:257-9. 3. Andonian S, Scoffone CM, Louie MK, et al. Does imaging modality used for percutaneous renal access make a difference? A matched case analysis. J Endourol. 2013;27:24-8. 4. Bagrodia A, Gupta A, Raman JD, Bensalah K, Pearle MS, Lotan Y. Predictors of cost and clinical outcomes of percutaneous nephrostolithotomy. J Urol. 2009;182:586-90. 5. Buchholz NP, van Rossum M. Shock wave lithotripsy treatment of radiolucent ureteric calculi with the help of contrast medium. Eur Urol. 2001;39:200-3. 6. Perks AE, Schuler TD, Lee J, et al. Stone attenuation and skin-to-stone distance on computed tomography predicts for stone fragmentation by shock wave lithotripsy. Urology. 2008;72:765-9. 7. Chua ME, Gatchalian GT, Corsino MV, Reyes BB. Diagnostic utility of attenuation measurement (Hounsfield units) in computed tomography stonogram in predicting the radio-opacity of urinary calculi in plain abdominal radiographs. Int Urol Nephrol. 2012;44:1349-55. 8. Chua ME, Gomez OR, Sapno LD, Lim SL, Morales ML, Jr. Use of computed tomography scout film and Hounsfield unit of computed tomography scan in predicting the radio-opacity of urinary calculi in plain kidney, ureter and bladder radiographs. Urol Ann. 2014;6:218-23. 9. Etemadian M, Soleimani MJ, Haghighi R, Zeighami MR, Najimi N. Does bleeding during percutaneous nephrolithotomy necessitate keeping the nephrostomy tube? A randomized controlled clinical trial. Urol J. 2011;8:21-6. 10. Gucuk A, Uyeturk U, Ozturk U, Kemahli E, Yildiz M, Metin A. Does the Hounsfield unit value determined by computed tomography predict the outcome of percutaneous nephrolithotomy? J Endourol. 2012;26:792-6. 11. Kumar A, Kumar N, Vasudeva P, Kumar Jha S, Kumar R, Singh H. A prospective, randomized comparison of shock wave lithotripsy, retrograde intrarenal surgery and miniperc for treatment of 1 to 2 cm radiolucent lower calyceal renal calculi: a single center experience. J Urol. 2015;193:160-4. 12. Resorlu B, Unsal A, Ziypak T, et al. Comparison of retrograde intrarenal surgery, shockwave lithotripsy, and percutaneous nephrolithotomy for treatment of medium-sized radiolucent renal stones. World J Urol. 2013;31:1581-6. 13. Bryniarski P, Paradysz A, Zyczkowski M, Kupilas A, Nowakowski K, Bogacki R. A randomized controlled study to analyze the safety and efficacy of percutaneous nephrolithotripsy and retrograde intrarenal surgery in the management of renal stones more than 2 cm in diameter. J Endourol. 2012;26:52-7. 14. De S, Autorino R, Kim FJ, et al. Percutaneous nephrolithotomy versus retrograde intrarenal surgery: a systematic review and meta-analysis. Eur Urol. 2015;67:125-37. 15. Donaldson JF, Lardas M, Scrimgeour D, et al. Systematic review and meta-analysis of the clinical effectiveness of shock wave lithotripsy, retrograde intrarenal surgery, and percutaneous nephrolithotomy for lower-pole renal stones. Eur Urol. 2015;67:612-6. 16. Anastasiadis A, Onal B, Modi P, et al. Impact of stone density on outcomes in percutaneous nephrolithotomy (PCNL): an analysis of the clinical research office of the endourological society (CROES) pcnl global study database. Scand J Urol. 2013;47:509-14. 17. Gucuk A, Kemahli E, Uyeturk U, Tuygun C, Yildiz M, Metin A. Routine flexible nephroscopy for percutaneous nephrolithotomy for renal stones with low density: a prospective, randomized study. J Urol. 2013;190:144-8.PCNL success with stone opacity-Maghsudi et al.Endourology and Stone Diseases   2902

The association of stone opacity in plain radiography with percutaneous nephrolithotomy outcomes and complications

http://eprints.iums.ac.ir/4057/1/The%20association%20of%20stone%20opacity%20in%20plain%20radiography%20with%20percutaneous%20nephrolithotomy%20outcomes%20and%20complications.pdf

The association of stone opacity in plain radiography with percutaneous nephrolithotomy outcomes and complications

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