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Impact of Lower Pole Anatomy on Stone Clearance After Shock Wave Lithotripsy
Y.S. Juan, S.M. Chuang, W.J. Wu et al
IMPACT OF LOWER POLE ANATOMY ON STONE CLEARANCE AFTER SHOCK WAVE LITHOTRIPSY Yung-Shun Juan, Shu-Mien Chuang,1 Wen-Jeng Wu,2 Jung-Tsung Shen, Chii-Jye Wang, and Chun-Hsiung Huang2 Department of Urology, Kaohsiung Municipal Hsiao-Kang Hospital, Departments of 1Anatomy and 2Urology, Kaohsiung Medical University Chun-Ho Memorial Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
This study retrospectively analyzed patients treated with shock wave ithotripsy (SWL) for lower calyceal stones, to determine the influence of the lower pole anatomy and stone size in predicting the clearance of fragments. Between June 2000 and March 2002, we reviewed excretory urography (IVU) of 59 patients with isolated lower pole stones treated with SWL. A total of 44 men and 15 women, with an age ranging between 23 and 78 years (mean, 55 years), were included in the study. The patients were divided into two groups, either a stone-free group or residual-stone group. After SWL, overall stone rate was 57.6%, and clearance for stones less than 10 mm in diameter was 64.5%, whereas clearance was 50% for stones between 10 and 20 mm in diameter. Intrarenal anatomy on IVU, such as infundibular width and infundibulopelvi-ureteric angle showed no significant difference between the stone-free and residual-stone groups. Our analysis showed that three significant variables were relevant to stone clearance: infundibular length, stone size and stone burden. We conclude that SWL is the best treatment for lower pole kidney stones 10 mm or less in diameter, showing lower complication and acceptable stone-free rates.
Key Words: stone, kidney, anatomy, excretory urography (Kaohsiung J Med Sci 2005;21:358–64)
Due to the procedure’s efficacy, efficiency and low morbidity, shock wave lithotripsy (SWL) is currently the primary treatment for most urinary calculi. Stone clearance after SWL has been shown to be affected by the stone’s size, location, and chemical composition, as well as by the anatomy of the kidney [1,2]. Clearance rate, however, differs for stones at various renal sites, with the lowest rates observed for stones in the lower calyx. The low clearance rates for stones in the lower pole
Received: April 1, 2005 Accepted: June 1, 2005 Address correspondence and reprint requests to: Dr. Chun-Hsiung Huang, Department of Urology, Kaohsiung Medical University st Chun-Ho Memorial Hospital, 100 Tzyou 1 Road, Kaohsiung 807, Taiwan. E-mail: [email protected]
358
are more of an issue of retention of fragments, rather than stone disintegration [3], and the causes of fragment retention, therefore, are worth investigating. Sampaio and Arago first described caliceal anatomy and concluded that infundibular length, infundibular width, and the lower pole infundibulopelvic angle (IPA) on preoperative execretory urography (IVU) affect the stone-free rate after SWI [4–7]. Also, other methods have been described, complicating the interpretation of the results [6,8]. This study retrospectively analyzed a group of patients treated with SWL for lower calyceal stones, in order to determine the influence of lower pole anatomy on IVU film in predicting for the clearance of fragments. We also assessed the effectiveness of using SWL, comparing stone-free rates against stone size and stone laterality, as well as with gender. Kaohsiung J Med Sci August 2005 • Vol 21 • No 8 © 2005 Elsevier. All rights reserved.
Stone clearance after shock wave lithotripsy
MATERIALS AND METHODS Between June 2002 and March 2004, we reviewed the charts and X-rays of 154 patients with isolated lower pole stone, treated with SWL. Patients with horseshoe kidney, severe hydronephrosis, multiple stones, a stone size of greater than 2 cm, or a follow-up of less than 3 months after SWL were excluded from the study. Ninety-five patients were excluded, and 59 patients with single lower calyceal stones of 2 cm or less who underwent IVU preoperatively were enrolled. Patients were evaluated by medical history, physical examination, sonography of urinary tract and IVU. Exclusion criteria for SWL treatment were acute urinary tract infection, coagulopathy and pregnancy. Stone size was defined as the largest bidimensional measurement of the stone via an anterior–posterior plain radiograph. The stone burden was calculated by computer software (The Digital Imaging and Communications in Medicine, DICOM 2000). SWL was performed with a Siemens lithostar multiline lithotriptor (Siemens Medizinische Technik, Erlangen, Germany) under intermittent fluoroscopic guidance and a twice-per-second frequency. The infundibulopelvi-ureteric angle (IPUA), infundibular length, infundibular width, infundibular length-to-width ratio, stone size, stone burden and
stone-to-width ratio were determined from IVU films. The lower pole infundibular length was measured in millimeters, from the most distal point at the bottom of the infundibulum to a midpoint at the lower lip of the renal pelvis (Figure 1). Lower pole infundibular width was measured in millimeters at the narrowest point along the infundibular axis (Figure 1). The IPUA was measured through two methods: IPUA1 was determined in degrees between two axes, including the ureteropelvic axis connecting the central point of the pelvis opposite the margins of the superior and inferior renal sinuses to the central point of the ureter opposite the lower kidney pole, and the central axis of the lower pole infundibulum [8] (Figure 2). IPUA-2 was determined in degrees by two axes, the central axis of the lower pole infundibulum and the perpendicular ureteral axis drawn from the kidney lower pole [9] (Figure 3). In each lithotripsy session, 2,500–3,500 shocks were given at 13.7–15.1 kv. The stone-free rate was evaluated by the postoperative radiographs and ultrasonography of the kidneys, 1 month after the last SWL, followed by additional radiographs at 3 months. Patients were considered stonefree with no evidence of urolithiasis or with residual fragments of less than 3 mm on plain abdominal X-ray. Statistical significance for each lower pole anatomic factor versus stone-free rate was evaluated, and a p value of less than 0.05 was considered statistically significant. Ureteropelvic angle Central axis of lower pole infundibulum Central axis of lower pole infundibulum
IPUA-2
IW IPUA-1 IL
Vertical ureteral axis Figure 1. Lower pole radiographic anatomy measurement: lower infundibular length (IL) was measured in mm from the most distal point at bottom of infundibulum to the midpoint at the lower lip of the renal pelvis. Lower pole infundibular width (IW) was measured in mm at the narrowest point along the infundibular axis. Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
Figure 2. Lower pole infundibulopelvicureteric angle-1 (IPUA-1), measured as the inner angle at the intersection of the ureteropelvic axis and the central axis of the lower pole infundibulum.
Figure 3. Lower pole infundibulopelvicureteric angle-2 (IPUA-2), measured as the inner angle at the vertical ureteral axis and the central axis of the lower pole infundibulum.
359
Y.S. Juan, S.M. Chuang, W.J. Wu et al
RESULTS Fifty-nine patients (44 males and 15 females) were treated, where the mean age was 55 years (range, 23–78 years), with all stones located in the lower calix. Median stone size was 10.5 cm (range, 0.5–2.0 cm) and median stone burden was 74.6 mm2 (range, 12–240 mm2). The characteristics of the patients before the procedure are shown in Table 1. We examined the effects of various anatomic factors on the stone clearance rate. On univariate analysis, stone size, stone burden and lower infundibular length were significant predictive factors for stone clearance (Table 2). Lower IPUA-1, IPUA-2, lower infundibular width, lower infundibular length-to-width ratio and stone-to-width ratio Table 1. Demography of patients Age Mean (range)
showed no significant difference between the stone-free group and the residual-stone group. The overall stone clearance rate was 57.6%. Depending on stone size, the stone-free rate was 64.5%, with a stone diameter of less than 10 mm (20 of 31 patients), and 50% with stone diameters between 10 mm and 20 mm (14 of 28 patients) (Table 3). Using the Fisher exact test analysis of intravariable differences, stone side, gender and stone size showed only slight differences in stone-free rates. According to stone side and when assessed against the effect of lower pole radiologic anatomy, stone size and stone laterality were independent factors in a subgroup analysis, and there was no significant effect between the subgroups (Table 3). Several patients had mild hematuria after shock wave treatment, which resolved spontaneously within 24 hours in all cases. Seven cases (11%) had renal colic and two cases (3%) had urinary tract infection. Most complications were minor and did not require operative intervention.
55 years old (23–78 years)
Gender Male Female
44 15
Laterality Left side Right side
41 18
Stone size (mm) Mean (range)
DISCUSSION
10.454 (0.5–2.0) 2
Stone burden (mm ) Mean (range)
74.6 (12–300)
Presently, SWL is the preferred treatment for most urinary calculi. As a primary treatment for lower calyceal stone, however, the procedure remains controversial [10,11]. In general, SWL has a success rate directly correlated to stone size. In cases of lower pole calculi, the efficacy of SWL treatment is not always satisfactory, with less stone clearance than kidney stones in other locations [1]. The stone clearance
Table 2. Univariate analysis of variables for prediction of stone clearance Variable factor Mean age (years) Mean stone size (mm)
Stone-free group
Residual-stone group
p
47.7 ± 11.9
53.3 ± 15.9
0.108
9.3 ± 3.7
12 ± 5.5
0.024
53.3 ± 22.7
103.6 ± 44.0
0.017
Mean IPUA-1 ± SD (degrees)
40.24 ± 12.90
40.37 ± 15.60
0.486
Mean IPUA–2 ± SD (degrees)
38.4 ± 13.1
38.6 ± 16.1
0.476
Mean lower infundibular length ± SD (mm)
33.1 ± 6.9
36.4 ± 9.4
0.089
Mean lower infundibular width ± SD (mm)
6.3 ± 2.3
6.8 ± 2.7
0.289
Mean lower infundibular length/width ratio ± SD
2.9 ± 1.5
5.1 ± 2.0
0.477
Mean stone size/ lower infundibular length ± SD
1.6 ± 1.1
1.8 ± 1.3
0.290
2
Mean stone burden (mm )
IPUA-1 = infundibulopelvi-ureteric angle-1; IPUA-2 = infundibulopelvi-ureteric angle-2.
360
Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
Stone clearance after shock wave lithotripsy Table 3. Analysis of intravariable differences and their effect on stone clearance Variable
Patients, n
Stone free, n (%)
p
Infundibular length > 30 mm < 30 mm
43 16
23 (54.0) 11 (69.0)
0.225
Infundibular width > 5 mm < 5 mm
37 22
19 (51.0) 15 (68.0)
0.161
IPUA–1 > 40° < 40°
29 30
15 (52.0) 19 (63.0)
0.262
IPUA–2 > 40° < 40°
28 31
14 (50.0) 20 (65.0)
0.194
Stone laterality Left side Right side
41 18
23 (56.0) 11 (61.0)
0.473
Gender Male Female
44 15
23 (54.0) 11 (73.0)
0.130
Stone size < 10 mm 10–20 mm
31 28
20 (64.5) 14 (50.0)
0.194
IPUA-1 = infundibulopelvi-ureteric angle-1; IPUA-2 = infundibulopelvi-ureteric angle-2.
rates after SWL for lower calyceal stone are reported to be at around 36–78% [6,8,12,13]. The lower success rate associated with SWL for lower calyceal stones has resulted in many urologists advocating other alternative treatments, including percutaneous nephrostolithotripsy [3,14]. The exact reasons for lower clearance of the fragments from the lower pole after SWL remain unclear. The high rate of residual fragments in the lower pole after SWL is more of a problem of retention of fragments, relating to the gravitydependent position of the stone and lower caliceal spatial anatomy, rather than of stone disintegration [3]. The risk of stone regrowth in patients with residual fragments has also been reported, and there have also been reports of higher incidences of future renal colic status [15,16]. Sampaio and Aragao first described the IPA, created by resin casts of collecting systems, and suggested that these anatomic features should be considered when performing SWL for lower caliceal stones [4]. Sabnis et al used IVU films to determine the IPA as a possible factor in clearance [17]. They reported that patients with a pelvicalyceal angle of less than 90°, infundibular diameter of less than 4 mm, and a complex calyceal pattern had significant residual-stone rates. For their part, however, Madbouly et al retrospectively Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
evaluated anatomic factors and found none of the three lower pole anatomic factors had any significant impact on the stone-free rate at three months [18]. Renal morphology was the only factor significantly affecting the stone-free rate, as stone clearance was significantly less in pyelonephritic kidneys. Other authors have reported that factors such as infundibular length, infundibular width, infundibular length-to-width ratio, and caliceal pelvic height are significant predictive factors for success in stone-free rate after SWL [17,19,20]. The present study, however, showed that only infundibular length was significantly different between the stone-free group and residual-stone group. We suggest that the reason infundibular width is not an important factor in stone clearance rate is because its measurement is not reliable. IVU is usually done at deep expiration, which is a respiratory status rarely adopted during daily activity. Not only that, but caliceal pelvic width may vary during respiratory movement or postural changing of the kidney. Studies may also have been performed during peristalsis, and the dynamic nature of the urinary tract may have made measurements imprecise [18]. 361
Y.S. Juan, S.M. Chuang, W.J. Wu et al
Stone clearance rate significantly decreases as the size of stone increases [3,8,12,18]. Lingeman et al showed that the efficiency of ESWL rapidly decreases as stone size increases [3]; stone clearance rates were 74% for stones of less than 10 mm, 56% for 10–20 mm, and 33% for stones greater than 2 cm. The overall stone clearance rate in the present study of 64.5% was comparable to those reported previously [3,11,18, 21]. Our study also showed that stone size and stone burden were inversely correlated to lower calyceal stone clearance rate after SWL. May and Chandhoke suggested that SWL be the initial treatment choice for most lower pole stones less than 2 cm in diameter, while primary percutaneous nephrolithotomy be considered for stones larger than 2 cm [22]. Many investigators have advocated alternative or adjuvant treatments to improve lower calyceal stone clearance rates after SWL. Brownlee et al proposed controlled inversion therapy using forced hydration, inversion, and diuresis and/or percussion as an enhancement to particle elimination after SWL [23]. The uses of transurethrally placed cobra catheters or percutaneous nephrostomy tubes for direct irrigation of lower calyceal stones were also proposed [24,25]. However, the anesthesia requirement, additional time, and invasive nature of these procedures may reduce their advantage over the noninvasiveness of SWL. In our study, we noted a predominance of male patients (74% men and 26% women), similar to that of Talic and El Faqih (80% men and 20% women) [2]. Interestingly, many authors have reported a higher number of patients with left-sided stones and worse stone-free rates [1,2,11,26]. We treated a similar percentage of patients with left renal stones (69%), but the stone-free rate was not worse than patients with right renal stones (p = 0.473). Some unknown reasons may have led to a greater generation or retention of calculi in the left side. Further studies are warranted to better evaluate the role of other variables that might influence SWL results for left lower calyceal stones. The exact reasons for the lower clearance rate of lower pole renal calculi have yet to be defined. Our study suggests that stone size and infundibular length are predictive factors of stone clearance rate for lower pole stone after SWL, and indirectly indicates the importance of gravitydependent position. SWL is best suited for lower pole kidney stones 10 mm or less, with lower complication rates and acceptable stone-free rates. Further examinations of lower pole anatomy and other contributing factors are still warranted. 362
REFERENCES 1. Kosar A, Turkolmez K, Sarica, K, et al. Calyceal stones: fate of shock wave therapy with respect to stone localization. Int Urol Nephrol 1998;30:433–8. 2. Talic RF, El Faqih SR. Extracorporeal shock wave lithotripsy for lower pole nephrolithiasis: efficacy and variables that influence treatment outcome. Urology 1998;51:544–7. 3. Lingeman JE, Siegel YI, Steele B, et al. Management of lower pole nephrolithiasis: a critical analysis. J Urol 1994;151:663–7. 4. Sampaio FJ, Aragao AH. Inferior pole collecting system anatomy: its probable role in extracorporeal shock wave lithotripsy. J Urol 1992;147:322–4. 5. Sampaio FJ, Aragao AH. Limitations of extracorporeal shockwave lithotripsy for lower caliceal stones: anatomic insight. J Endourol 1994;8:241–7. 6. Ozgur TM, Karaoglan U, Sen I, et al. The impact of radiological anatomy in clearance of lower calyceal stones after shock wave lithotripsy in paediatric patients. Eur Urol 2003;43:188–93. 7. Sampaio FJ, D’Anunciacao AL, Silva EC. Comparative followup of patients with acute and obtuse infundibulum-pelvic angle submitted to extracorporeal shockwave lithotripsy for lower caliceal stones: preliminary report and proposed study design. J Endourol 1997;11:157–61. 8. Elbahnasy AM, Shalhav AL, Hoenig DM,et al. Lower caliceal stone clearance after shock wave lithotripsy or ureteroscopy: the impact of lower pole radiographic anatomy. J Urol 1998; 159:676–82. 9. Bagley DH, Rittenberg MH. Intrarenal dimensions. Guidelines for flexible ureteropyeloscopes. Surg Endosc 1987;1:119–21. 10. Netto NR Jr, Claro J, FLemos GC, et al. Renal calculi in lower pole calices: what is the best method of treatment? J Urol 1991; 146:721–3. 11. Riedler I, Trummer H, Hebel P, et al. Outcome and safety of extracorporeal shock wave lithotripsy as first-line therapy of lower pole nephrolithiasis. Urol Int 2003;71:350–4. 12. Srivastava A, Zaman W, Singh V, et al. Efficacy of extracorporeal shock wave lithotripsy for solitary lower calyceal stone: a statistical model. BJU Int 2004;93:364–8. 13. Obek C, Onal B, Kantay K, et al. The efficacy of extracorporeal shock wave lithotripsy for isolated lower pole calculi compared with isolated middle and upper caliceal calculi. J Urol 2001; 166:2081–4. 14. Stav K, Cooper A, Zisman A, et al. Retrograde intrarenal lithotripsy outcome after failure of shock wave lithotripsy. J Urol 2003;170:2198–201. 15. Zanetti G., Seveso M, Montanari E, et al. Renal stone fragments following shock wave lithotripsy. J Urol 1997;158:352–5. 16. Streem SB, Yost A, Mascha E. Clinical implications of clinically insignificant store fragments after extracorporeal shock wave lithotripsy. J Urol 1996;155:1186–90. 17. Sabnis RB, Naik K, Patel SH, et al. Extracorporeal shock wave lithotripsy for lower calyceal stones: can clearance be predicted? Br J Urol 1997;80:853–7. 18. Madbouly K, Sheir KZ, Elsobky E. Impact of lower pole renal anatomy on stone clearance after shock wave lithotripsy: fact or fiction? J Urol 2001;165:1415–8. Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
Stone clearance after shock wave lithotripsy 19. Sumino Y, Mimata H, Tasaki Y, et al. Predictors of lower pole renal stone clearance after extracorporeal shock wave lithotripsy. J Urol 2002;168:1344–7. 20. Poulakis V, Dahm P, Witzsch U, et al. Prediction of lower pole stone clearance after shock wave lithotripsy using an artificial neural network. J Urol 2003;169:1250–6. 21. Keeley FX Jr, Moussa SA, Smith G, et al. Clearance of lowerpole stones following shock wave lithotripsy: effect of the infundibulopelvic angle. Eur Urol 1999;36:371–5. 22. May DJ, Chandhoke PS. Efficacy and cost-effectiveness of extracorporeal shock wave lithotripsy for solitary lower pole renal calculi. J Urol 1998;159:24–7. 23. Brownlee N, Foster M, Griffith DP, et al. Controlled inversion
Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
therapy: an adjunct to the elimination of gravity-dependent fragments following extracorporeal shock wave lithotripsy. J Urol 1990;143:1096–8. 24. Nicely ER, Maggio MI, Kuhn EJ. The use of a cystoscopically placed cobra catheter for directed irrigation of lower pole caliceal stones during extracorporeal shock wave lithotripsy. J Urol 1992;148:1036–9. 25. Graham JB, Nelson JB. Percutaneous caliceal irrigation during extracorporeal shock wave lithotripsy for lower pole renal calculi. J Urol 1994;152:2227. 26. Drach G.W, Dretler S, Fair W, et al. Report of the United States cooperative study of extracorporeal shock wave lithotripsy. J Urol 1986;135:1127–33.
363
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Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
IMPACT OF LOWER POLE ANATOMY ON STONE CLEARANCE AFTER SHOCK WAVE LITHOTRIPSY Yung-Shun Juan, Shu-Mien Chuang,1 Wen-Jeng Wu,2 Jung-Tsung Shen, Chii-Jye Wang, and Chun-Hsiung Huang2 Department of Urology, Kaohsiung Municipal Hsiao-Kang Hospital, Departments of 1Anatomy and 2Urology, Kaohsiung Medical University Chun-Ho Memorial Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
This study retrospectively analyzed patients treated with shock wave ithotripsy (SWL) for lower calyceal stones, to determine the influence of the lower pole anatomy and stone size in predicting the clearance of fragments. Between June 2000 and March 2002, we reviewed excretory urography (IVU) of 59 patients with isolated lower pole stones treated with SWL. A total of 44 men and 15 women, with an age ranging between 23 and 78 years (mean, 55 years), were included in the study. The patients were divided into two groups, either a stone-free group or residual-stone group. After SWL, overall stone rate was 57.6%, and clearance for stones less than 10 mm in diameter was 64.5%, whereas clearance was 50% for stones between 10 and 20 mm in diameter. Intrarenal anatomy on IVU, such as infundibular width and infundibulopelvi-ureteric angle showed no significant difference between the stone-free and residual-stone groups. Our analysis showed that three significant variables were relevant to stone clearance: infundibular length, stone size and stone burden. We conclude that SWL is the best treatment for lower pole kidney stones 10 mm or less in diameter, showing lower complication and acceptable stone-free rates.
Key Words: stone, kidney, anatomy, excretory urography (Kaohsiung J Med Sci 2005;21:358–64)
Due to the procedure’s efficacy, efficiency and low morbidity, shock wave lithotripsy (SWL) is currently the primary treatment for most urinary calculi. Stone clearance after SWL has been shown to be affected by the stone’s size, location, and chemical composition, as well as by the anatomy of the kidney [1,2]. Clearance rate, however, differs for stones at various renal sites, with the lowest rates observed for stones in the lower calyx. The low clearance rates for stones in the lower pole
Received: April 1, 2005 Accepted: June 1, 2005 Address correspondence and reprint requests to: Dr. Chun-Hsiung Huang, Department of Urology, Kaohsiung Medical University st Chun-Ho Memorial Hospital, 100 Tzyou 1 Road, Kaohsiung 807, Taiwan. E-mail: [email protected]
358
are more of an issue of retention of fragments, rather than stone disintegration [3], and the causes of fragment retention, therefore, are worth investigating. Sampaio and Arago first described caliceal anatomy and concluded that infundibular length, infundibular width, and the lower pole infundibulopelvic angle (IPA) on preoperative execretory urography (IVU) affect the stone-free rate after SWI [4–7]. Also, other methods have been described, complicating the interpretation of the results [6,8]. This study retrospectively analyzed a group of patients treated with SWL for lower calyceal stones, in order to determine the influence of lower pole anatomy on IVU film in predicting for the clearance of fragments. We also assessed the effectiveness of using SWL, comparing stone-free rates against stone size and stone laterality, as well as with gender. Kaohsiung J Med Sci August 2005 • Vol 21 • No 8 © 2005 Elsevier. All rights reserved.
Stone clearance after shock wave lithotripsy
MATERIALS AND METHODS Between June 2002 and March 2004, we reviewed the charts and X-rays of 154 patients with isolated lower pole stone, treated with SWL. Patients with horseshoe kidney, severe hydronephrosis, multiple stones, a stone size of greater than 2 cm, or a follow-up of less than 3 months after SWL were excluded from the study. Ninety-five patients were excluded, and 59 patients with single lower calyceal stones of 2 cm or less who underwent IVU preoperatively were enrolled. Patients were evaluated by medical history, physical examination, sonography of urinary tract and IVU. Exclusion criteria for SWL treatment were acute urinary tract infection, coagulopathy and pregnancy. Stone size was defined as the largest bidimensional measurement of the stone via an anterior–posterior plain radiograph. The stone burden was calculated by computer software (The Digital Imaging and Communications in Medicine, DICOM 2000). SWL was performed with a Siemens lithostar multiline lithotriptor (Siemens Medizinische Technik, Erlangen, Germany) under intermittent fluoroscopic guidance and a twice-per-second frequency. The infundibulopelvi-ureteric angle (IPUA), infundibular length, infundibular width, infundibular length-to-width ratio, stone size, stone burden and
stone-to-width ratio were determined from IVU films. The lower pole infundibular length was measured in millimeters, from the most distal point at the bottom of the infundibulum to a midpoint at the lower lip of the renal pelvis (Figure 1). Lower pole infundibular width was measured in millimeters at the narrowest point along the infundibular axis (Figure 1). The IPUA was measured through two methods: IPUA1 was determined in degrees between two axes, including the ureteropelvic axis connecting the central point of the pelvis opposite the margins of the superior and inferior renal sinuses to the central point of the ureter opposite the lower kidney pole, and the central axis of the lower pole infundibulum [8] (Figure 2). IPUA-2 was determined in degrees by two axes, the central axis of the lower pole infundibulum and the perpendicular ureteral axis drawn from the kidney lower pole [9] (Figure 3). In each lithotripsy session, 2,500–3,500 shocks were given at 13.7–15.1 kv. The stone-free rate was evaluated by the postoperative radiographs and ultrasonography of the kidneys, 1 month after the last SWL, followed by additional radiographs at 3 months. Patients were considered stonefree with no evidence of urolithiasis or with residual fragments of less than 3 mm on plain abdominal X-ray. Statistical significance for each lower pole anatomic factor versus stone-free rate was evaluated, and a p value of less than 0.05 was considered statistically significant. Ureteropelvic angle Central axis of lower pole infundibulum Central axis of lower pole infundibulum
IPUA-2
IW IPUA-1 IL
Vertical ureteral axis Figure 1. Lower pole radiographic anatomy measurement: lower infundibular length (IL) was measured in mm from the most distal point at bottom of infundibulum to the midpoint at the lower lip of the renal pelvis. Lower pole infundibular width (IW) was measured in mm at the narrowest point along the infundibular axis. Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
Figure 2. Lower pole infundibulopelvicureteric angle-1 (IPUA-1), measured as the inner angle at the intersection of the ureteropelvic axis and the central axis of the lower pole infundibulum.
Figure 3. Lower pole infundibulopelvicureteric angle-2 (IPUA-2), measured as the inner angle at the vertical ureteral axis and the central axis of the lower pole infundibulum.
359
Y.S. Juan, S.M. Chuang, W.J. Wu et al
RESULTS Fifty-nine patients (44 males and 15 females) were treated, where the mean age was 55 years (range, 23–78 years), with all stones located in the lower calix. Median stone size was 10.5 cm (range, 0.5–2.0 cm) and median stone burden was 74.6 mm2 (range, 12–240 mm2). The characteristics of the patients before the procedure are shown in Table 1. We examined the effects of various anatomic factors on the stone clearance rate. On univariate analysis, stone size, stone burden and lower infundibular length were significant predictive factors for stone clearance (Table 2). Lower IPUA-1, IPUA-2, lower infundibular width, lower infundibular length-to-width ratio and stone-to-width ratio Table 1. Demography of patients Age Mean (range)
showed no significant difference between the stone-free group and the residual-stone group. The overall stone clearance rate was 57.6%. Depending on stone size, the stone-free rate was 64.5%, with a stone diameter of less than 10 mm (20 of 31 patients), and 50% with stone diameters between 10 mm and 20 mm (14 of 28 patients) (Table 3). Using the Fisher exact test analysis of intravariable differences, stone side, gender and stone size showed only slight differences in stone-free rates. According to stone side and when assessed against the effect of lower pole radiologic anatomy, stone size and stone laterality were independent factors in a subgroup analysis, and there was no significant effect between the subgroups (Table 3). Several patients had mild hematuria after shock wave treatment, which resolved spontaneously within 24 hours in all cases. Seven cases (11%) had renal colic and two cases (3%) had urinary tract infection. Most complications were minor and did not require operative intervention.
55 years old (23–78 years)
Gender Male Female
44 15
Laterality Left side Right side
41 18
Stone size (mm) Mean (range)
DISCUSSION
10.454 (0.5–2.0) 2
Stone burden (mm ) Mean (range)
74.6 (12–300)
Presently, SWL is the preferred treatment for most urinary calculi. As a primary treatment for lower calyceal stone, however, the procedure remains controversial [10,11]. In general, SWL has a success rate directly correlated to stone size. In cases of lower pole calculi, the efficacy of SWL treatment is not always satisfactory, with less stone clearance than kidney stones in other locations [1]. The stone clearance
Table 2. Univariate analysis of variables for prediction of stone clearance Variable factor Mean age (years) Mean stone size (mm)
Stone-free group
Residual-stone group
p
47.7 ± 11.9
53.3 ± 15.9
0.108
9.3 ± 3.7
12 ± 5.5
0.024
53.3 ± 22.7
103.6 ± 44.0
0.017
Mean IPUA-1 ± SD (degrees)
40.24 ± 12.90
40.37 ± 15.60
0.486
Mean IPUA–2 ± SD (degrees)
38.4 ± 13.1
38.6 ± 16.1
0.476
Mean lower infundibular length ± SD (mm)
33.1 ± 6.9
36.4 ± 9.4
0.089
Mean lower infundibular width ± SD (mm)
6.3 ± 2.3
6.8 ± 2.7
0.289
Mean lower infundibular length/width ratio ± SD
2.9 ± 1.5
5.1 ± 2.0
0.477
Mean stone size/ lower infundibular length ± SD
1.6 ± 1.1
1.8 ± 1.3
0.290
2
Mean stone burden (mm )
IPUA-1 = infundibulopelvi-ureteric angle-1; IPUA-2 = infundibulopelvi-ureteric angle-2.
360
Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
Stone clearance after shock wave lithotripsy Table 3. Analysis of intravariable differences and their effect on stone clearance Variable
Patients, n
Stone free, n (%)
p
Infundibular length > 30 mm < 30 mm
43 16
23 (54.0) 11 (69.0)
0.225
Infundibular width > 5 mm < 5 mm
37 22
19 (51.0) 15 (68.0)
0.161
IPUA–1 > 40° < 40°
29 30
15 (52.0) 19 (63.0)
0.262
IPUA–2 > 40° < 40°
28 31
14 (50.0) 20 (65.0)
0.194
Stone laterality Left side Right side
41 18
23 (56.0) 11 (61.0)
0.473
Gender Male Female
44 15
23 (54.0) 11 (73.0)
0.130
Stone size < 10 mm 10–20 mm
31 28
20 (64.5) 14 (50.0)
0.194
IPUA-1 = infundibulopelvi-ureteric angle-1; IPUA-2 = infundibulopelvi-ureteric angle-2.
rates after SWL for lower calyceal stone are reported to be at around 36–78% [6,8,12,13]. The lower success rate associated with SWL for lower calyceal stones has resulted in many urologists advocating other alternative treatments, including percutaneous nephrostolithotripsy [3,14]. The exact reasons for lower clearance of the fragments from the lower pole after SWL remain unclear. The high rate of residual fragments in the lower pole after SWL is more of a problem of retention of fragments, relating to the gravitydependent position of the stone and lower caliceal spatial anatomy, rather than of stone disintegration [3]. The risk of stone regrowth in patients with residual fragments has also been reported, and there have also been reports of higher incidences of future renal colic status [15,16]. Sampaio and Aragao first described the IPA, created by resin casts of collecting systems, and suggested that these anatomic features should be considered when performing SWL for lower caliceal stones [4]. Sabnis et al used IVU films to determine the IPA as a possible factor in clearance [17]. They reported that patients with a pelvicalyceal angle of less than 90°, infundibular diameter of less than 4 mm, and a complex calyceal pattern had significant residual-stone rates. For their part, however, Madbouly et al retrospectively Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
evaluated anatomic factors and found none of the three lower pole anatomic factors had any significant impact on the stone-free rate at three months [18]. Renal morphology was the only factor significantly affecting the stone-free rate, as stone clearance was significantly less in pyelonephritic kidneys. Other authors have reported that factors such as infundibular length, infundibular width, infundibular length-to-width ratio, and caliceal pelvic height are significant predictive factors for success in stone-free rate after SWL [17,19,20]. The present study, however, showed that only infundibular length was significantly different between the stone-free group and residual-stone group. We suggest that the reason infundibular width is not an important factor in stone clearance rate is because its measurement is not reliable. IVU is usually done at deep expiration, which is a respiratory status rarely adopted during daily activity. Not only that, but caliceal pelvic width may vary during respiratory movement or postural changing of the kidney. Studies may also have been performed during peristalsis, and the dynamic nature of the urinary tract may have made measurements imprecise [18]. 361
Y.S. Juan, S.M. Chuang, W.J. Wu et al
Stone clearance rate significantly decreases as the size of stone increases [3,8,12,18]. Lingeman et al showed that the efficiency of ESWL rapidly decreases as stone size increases [3]; stone clearance rates were 74% for stones of less than 10 mm, 56% for 10–20 mm, and 33% for stones greater than 2 cm. The overall stone clearance rate in the present study of 64.5% was comparable to those reported previously [3,11,18, 21]. Our study also showed that stone size and stone burden were inversely correlated to lower calyceal stone clearance rate after SWL. May and Chandhoke suggested that SWL be the initial treatment choice for most lower pole stones less than 2 cm in diameter, while primary percutaneous nephrolithotomy be considered for stones larger than 2 cm [22]. Many investigators have advocated alternative or adjuvant treatments to improve lower calyceal stone clearance rates after SWL. Brownlee et al proposed controlled inversion therapy using forced hydration, inversion, and diuresis and/or percussion as an enhancement to particle elimination after SWL [23]. The uses of transurethrally placed cobra catheters or percutaneous nephrostomy tubes for direct irrigation of lower calyceal stones were also proposed [24,25]. However, the anesthesia requirement, additional time, and invasive nature of these procedures may reduce their advantage over the noninvasiveness of SWL. In our study, we noted a predominance of male patients (74% men and 26% women), similar to that of Talic and El Faqih (80% men and 20% women) [2]. Interestingly, many authors have reported a higher number of patients with left-sided stones and worse stone-free rates [1,2,11,26]. We treated a similar percentage of patients with left renal stones (69%), but the stone-free rate was not worse than patients with right renal stones (p = 0.473). Some unknown reasons may have led to a greater generation or retention of calculi in the left side. Further studies are warranted to better evaluate the role of other variables that might influence SWL results for left lower calyceal stones. The exact reasons for the lower clearance rate of lower pole renal calculi have yet to be defined. Our study suggests that stone size and infundibular length are predictive factors of stone clearance rate for lower pole stone after SWL, and indirectly indicates the importance of gravitydependent position. SWL is best suited for lower pole kidney stones 10 mm or less, with lower complication rates and acceptable stone-free rates. Further examinations of lower pole anatomy and other contributing factors are still warranted. 362
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Stone clearance after shock wave lithotripsy 19. Sumino Y, Mimata H, Tasaki Y, et al. Predictors of lower pole renal stone clearance after extracorporeal shock wave lithotripsy. J Urol 2002;168:1344–7. 20. Poulakis V, Dahm P, Witzsch U, et al. Prediction of lower pole stone clearance after shock wave lithotripsy using an artificial neural network. J Urol 2003;169:1250–6. 21. Keeley FX Jr, Moussa SA, Smith G, et al. Clearance of lowerpole stones following shock wave lithotripsy: effect of the infundibulopelvic angle. Eur Urol 1999;36:371–5. 22. May DJ, Chandhoke PS. Efficacy and cost-effectiveness of extracorporeal shock wave lithotripsy for solitary lower pole renal calculi. J Urol 1998;159:24–7. 23. Brownlee N, Foster M, Griffith DP, et al. Controlled inversion
Kaohsiung J Med Sci August 2005 • Vol 21 • No 8
therapy: an adjunct to the elimination of gravity-dependent fragments following extracorporeal shock wave lithotripsy. J Urol 1990;143:1096–8. 24. Nicely ER, Maggio MI, Kuhn EJ. The use of a cystoscopically placed cobra catheter for directed irrigation of lower pole caliceal stones during extracorporeal shock wave lithotripsy. J Urol 1992;148:1036–9. 25. Graham JB, Nelson JB. Percutaneous caliceal irrigation during extracorporeal shock wave lithotripsy for lower pole renal calculi. J Urol 1994;152:2227. 26. Drach G.W, Dretler S, Fair W, et al. Report of the United States cooperative study of extracorporeal shock wave lithotripsy. J Urol 1986;135:1127–33.
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