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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 29  |  Issue : 2  |  Page : 297-302

Role of multidetector computed tomography without contrast enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi


1 Visitor in Radiology Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Radiology Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Date of Submission14-May-2014
Date of Acceptance02-Jun-2014
Date of Web Publication18-Oct-2016

Correspondence Address:
Alaa Mohamed Mohamed El Mahdy
El-Baramoon, beside DR. Amira Pharmacy, Mansoura, Dakahlia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.192414

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  Abstract 

Objective:
The aim of this study was to evaluate the role of nonenhancing computed tomography as a predictive factor for successful extracorporeal shock wave lithotripsy (ESWL) for urinary calculi to avoid the cost of ineffective ESWL.
Background:
Urolithiasis is a universal problem. Many methods of treatment of urolithiasis are described, among which is ESWLs. The outcome of ESWL is affected by several factors. Multidetector computed tomography (MDCT) can aid the localization of calculi and may provide accurate anatomical detail, providing valuable data such as stone size and stone density as predictors for ESWL success.
Materials and methods:
This study included 54 patients who presented with symptomatic renal colic and hematuria at the ESWL unit. ESWL was used as the primary treatment option for all patients. All patients were investigated by MDCT before and after ESWL treatment. Successful ESWL was defined when a patient had achieved complete clearance of the stone fragments or had small residual gravels of size less than 4 mm. ESWL failure was defined as no breakage of the stone after three sessions.
Results:
A high rate of ESWL success after a second session of ESWL was achieved in 26 cases (48.1%), followed by a first session in 15 cases (27.8%), with an overall success rate of 90.7% in 49 cases. Also, smaller size and density of urinary stones will increase the success rate of ESWL.
Conclusion:
MDCT can be used to provide valuable data on urinary stones to aid treatment decisions and predict the outcome of ESWL.

Keywords: extracorporeal shock wave lithotripsy, multidetector computed tomography, stone density, stone size


How to cite this article:
El Mahdy AM, El Sayed EE. Role of multidetector computed tomography without contrast enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi. Menoufia Med J 2016;29:297-302

How to cite this URL:
El Mahdy AM, El Sayed EE. Role of multidetector computed tomography without contrast enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi. Menoufia Med J [serial online] 2016 [cited 2019 Nov 22];29:297-302. Available from: http://www.mmj.eg.net/text.asp?2016/29/2/297/192414


  Introduction Top


Urolithiasis is a worldwide problem, affecting patients across geographical, cultural, and racial boundaries [1]; many patients may have multiple stones throughout their lifetime, with estimated recurrence rates of 50% within 5–10 years and 75% within 20 years [2].

Urinary stones include five main types: calcium (70–80%), magnesium ammonium phosphate (struvite) (15–20%), uric acid (5–10%), cystine (1–3%), and medications and their metabolites (1%) [3].

Unlike kidney, ureters and bladder (KUB) X-ray imaging, almost all types of stones are visible on computed tomography (CT) [4]. Its ability to detect density differences as low as 0.5% has been exploited to determine the composition and fragility of urinary stones [5].

Since its introduction by Chaussy et al. [6] in 1980, extracorporeal shock wave lithotripsy (ESWL) has become the preferred treatment for renal calculi [5] and has been considered as a first-line treatment for ureteral stones for the past 20 years, with a success rate of about 80–90% [7]. The success of ESWL is related to a number of factors that may be evaluated by CT, including stone location, size, and composition [8].


  Materials and Methods Top


This study included 54 patients, who presented with symptomatic renal colic and hematuria at the ESWL unit at Mansoura Health Insurance Hospital in the period between May 2013 and March 2014. ESWL was used as the primary treatment option for all patients. Written consent was obtained from all patients included in this study. Inclusion criteria included patent urinary tract distal to the stone to allow free clearance of stone fragments. Exclusion criteria included pregnant women, patients with previous ESWL, diabetes mellitus, hypertension, liver diseases, medical kidney diseases including uncontrolled infections, patient with abnormal coagulopathy disorder, those with abdominal vessels, aneurysm, high BMI, and patients with congenital and skeletal abnormalities.

All patients were subjected to a full clinical assessment by a urologist. All patients were investigated by noncontrast multidetector computed tomography (MDCT) before and after ESWL treatment using 16-channel MDCT. No specific medical or bowel preparations were needed other than adequate patient hydration. The stone size was calculated in millimeters on a bone window (1120/300) with a magnification power of 4–5. The CT attenuation value in Hounsfield units (HU) was measured on bone window (1120/300) on three axial planes: one near the upper end, one in the middle, and one near the lower end. A region of interest smaller than the stone was drawn and the mean Hounsfield unit was calculated. The skin to stone distance (SSD) was calculated by measuring three distances from the stone to the skin at 0, 45, and 90°; the average of these values was calculated to represent the SSD for each stone. All patients were subjected to ESWL using lithotripter equipment. This lithotripter equipment had electromagnetic as a source for shock wave and radiographic as stone localization. We started with a low energy of 0.1, which equaled 11.7 kV, and had an image to ensure stone localization; then, we gradually increased the power. An image was taken every 150 shock waves in both vertical and oblique positions to confirm stone localization. The rate of increase of the voltage of the shock wave depended on patient tolerability. The procedure was stopped when complete fragmentation of the stone had been achieved or when the number of shock waves reached 3500 shocks.

The first MDCT was taken 1 week after the session to evaluate the success of the ESWL. Successful ESWL was defined when a patient achieved complete clearance of the stone fragments or had small residual gravels of size less than 4 mm. Patients with noninfected, asymptomatic residual gravels less than 4 mm were scheduled for regular follow-up every 6 months. If there was no breakage of the stone after three sessions, the case was considered as ESWL failure. Repeat treatment was carried out after 2 weeks if inadequate fragmentation of the stone was observed. In case of partial disintegration after three sessions, ESWL was not continued.


  Results Top


This study included 54 (32 men and 22 women) patients who presented with renal colic; the age of the patients ranged from 19 to 65 years, with an average age at presentation of 33.7 years. All patients were subjected to 113 sessions of ESWL, with an average of 2.09 session/patient.

Our study shows that the smaller the size of the stone, the higher the success rate of ESWL, whereas the larger the size of urinary stone, the higher the ESWL sessions required and even ESWL failure; the suitable stone size for ESWL was usually below 2 cm in kidney stone and 1 cm in ureteric stone ([Table 1]).
Table 1: Relation between stone size and extracorporeal shock wave lithotripsy success

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Our study shows that the smaller the density of the stone, the higher the success rate of ESWL, whereas the larger the density of urinary stone, the greater the hardness of the stone, thus requiring more ESWL sessions and even resulting in ESWL failure; the suitable stone density for ESWL was usually below 1000 HU ([Table 2]).
Table 2: Relation between stone density and extracorporeal shock wave lithotripsy success

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In our study, considering the location of stone, most of the kidney stones were located in the lower calyx and this showed the lowest success rate of ESWL (92.3%). However, in ureteric stones, most stones were located in the lower ureter and also showed a lowest success rate of ESWL (80%) ([Table 3]).
Table 3: Relation between stone location and extracorporeal shock wave lithotripsy success

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In our study, in terms of SSD, the failure rate of the first group (≤10 cm) was 6.1%, whereas that of the second group (>10 cm) was 14.3% ([Table 4]).
Table 4: Relation between skin to stone distance and extracorporeal shock wave lithotripsy success

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  Discussion Top


Many methods of treatment of urolithiasis are described, among which is ESWL [9]. ESWL offers several advantages over other modalities of stone treatment; it is a minimally invasive procedure, is an outpatient treatment, and most of the patients can resume their work within 2 days after the procedure [0]. Key factors in the management of renal stone patients remain the location, size, and chemical composition of the stone. Nowadays, non-contrast-enhanced MDCT is considered the most accurate method for detection of calculi in the urinary tract, with a reported sensitivity of 94% and a specificity of 97%; it has also been accepted as the imaging modality of choice to differentiate between urinary calculi and other pathologic processes [1].

Our study was carried out in the ESWL unit at Mansoura Health Insurance Hospital in the period between May 2013 and March 2014. ESWL was used as the primary treatment option for all patients. This study included 54 (32 men and 22 women) patients who presented with renal colic and hematuria; the age of the patients ranged from 19 to 65 years, with an average age at presentation of 33.7 years. All patients were subjected to 113 sessions of ESWL, with an average of 2.09 sessions/patient.

In this study, kidney stones ranged in size from 0.5 to 3.5 cm and were divided into three groups according to their size. The most frequently presented stone size ranged from 1 to 2 cm and this was found in 19 (35.2%) patients and the second most frequently presented stone size was less than 1 cm and this was found in seven (13%) patients; the third group had a stone size more than 2 cm and was found in five (9.2%) patients.

In the first group (size <1 cm), five patients (71.4%) showed ESWL success after the first session and two patients (28.6%) showed ESWL success after the second session, with an overall success rate of 100%.

In the second group (size between 1 and 2 cm), six patients (31.6%) showed ESWL success after the first session ([Figure 1]), 10 patients (52.6%) showed ESWL success after the second session, and three patients (15.8%) showed ESWL success after more than two sessions, with an overall success rate of 100%.
Figure 1: (a and b) Non contrast computed tomography (NCCT) of the abdomen and pelvis, axial and oblique views showing a hyperdense stone observed in the left renal pelvis. (c and d) After one session of extracorporeal shock wave lithotripsy (ESWL), axial and coronal views show complete clearance of the left renal pelvis stone

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In the third group (size >2 cm), three patients (60%) showed ESWL success after the second session and one patient (20%) showed ESWL success after more than two sessions, with an overall success rate of 80%. One patient (20%) showed failure of ESWL.

In addition, a high incidence of ESWL success occurred after the second session of ESWL in 26 cases (48.1%), followed by the first session in 15 cases (27.8%), with an overall success rate in 49 cases of 90.7%. Also, smaller size and density of urinary stones will increase the success rate of ESWL.

This result shows that ESWL remains a good option of treatment of urinary stones. Higher success rates of ESWL require selective criteria such as smaller size of kidney stones; however, larger size kidney stones will further increase the required sessions for success of ESWL and may even result in failure of ESWL. Kidney stones less than 2 cm in size are more suitable for ESWL and show good results; this is in agreement with Tanaka et al. [2], Hameed et al. [3], Azab and Osama [0], Nakamura et al. [4], and Wiesenthal et al. [5].

In our study, ureteric stones ranged in size from 0.4 to 2.0 cm and were divided according to the size into three groups. The most frequently presented stone size ranged from 0.6 to 1 cm and was found in 13 patients (24.1%), followed by stone size more than 1 cm found in seven patients (13%), and finally, stone size equal to or less than 5 mm was found in three patients (5.5%).

In the first group (≤5 mm), two patients (66.7%) showed ESWL success after the first session and one patient (33.3%) showed ESWL success after two sessions, with an overall success rate of 100%.

In the second group (0.6 and 1 cm), two patients (15.4%) showed ESWL success after the first session and eight patients (61.5%) showed ESWL success after the second session; two patients (15.4%) showed ESWL success after more than two sessions, with an overall success rate of 92.3%, and one patient (7.7%) showed ESWL failure.

In the third group (>1 cm), two patients (28.6%) showed ESWL success after the second session and two patients (28.6%) showed ESWL success after more than two sessions, with an overall success rate of 57.2%. Three patients (42.8%) showed ESWL failure.

This result indicates that larger size ureteric stones will further increase the required sessions for ESWL success and may even result in the failure of ESWL. Ureteric stones less than 1 cm in size are more suitable for ESWL and yield good results; this is in agreement with Mohamed et al. [6], Tanaka et al. [2], Choi et al. [7], Nakamura et al. [4], and Wiesenthal et al. [5].

In our study, all patients were divided according to the density of stones into three groups. The most frequently presented stone density ranged from 500 to 1000 HU and was found in 30 patients (55.6%), followed by stone density less than 500 HU, found in 15 patients (27.8%), followed by stone density more than 1000 HU, found in nine patients (16.6%).

In the first group (density <500 HU), 13 patients (86.7%) showed ESWL success after the first session and two patients (13.3%) showed ESWL success after the second session, with an overall success rate of 100%.

In the second group (density between 500 and 1000 HU), two patients (6.6%) showed ESWL success after the first session, 23 patients (76.8%) showed ESWL success after the second session, and four patients (13.3%) showed ESWL success after more than two sessions, with an overall success rate of 96.7%. One patient (3.3%) showed failure of ESWL and required another procedure.

In the third group (density >1000 HU), one patient (11.2%) showed ESWL success after the second session and four patients (44.4%) showed ESWL success after more than two sessions, with an overall success rate of 55.6%. Four patients (44.4%) showed failure of ESWL and required another procedure.

This result indicates that smaller density of the stone will increase the success rate of ESWL, whereas larger density of renal stone will increase the hardness of the stone and thus require more ESWL sessions and may even result in ESWL failure. The suitable stone density for ESWL is usually below 1000 HU; patients with stone density less than 500 usually require one session, whereas those with stone density ranging from 500 to 1000 HU usually require two sessions. This is in agreement with Massoud et al. [7], Hameed et al. [3], Choi et al. [7], Wiesenthal et al. [5], Ng et al. [8], and Bandi et al. [8]. However, Pareek et al. [9] and Patel and Kozakowski [0] reported that density of the stone is not a predicting factor for ESWL success. For example, Patel and Kozakowski reported that the mean HU for patients with residual fragments was slightly higher than those of stone-free patients (738 vs. 779); it was not found to be a significant predictor of ESWL success [0]. The difference may be attributed to the large number of patients in Patel's study than in our study.

In our study, in terms of the location of stones, most kidney stones were observed in the lower calyx stones, 13 patients (24.0%), followed by renal pelvis stones, 11 patients (20.4%), followed by middle calyx stones, five patients (9.3%); upper calyx stones were found in only two patients (3.7%). The increased ratio of lower calyx stones was because of the effect of gravity, which prevented stone spontaneous clearance; this is in agreement with Massoud et al. [7] and Hameed et al. [3].

The upper, middle calyxes, and renal pelvis showed the highest success rate (100%) ([Figure 2]), whereas the lower calyx showed the lowest success rate, in 12 patients (92.3%); in one patient (7.7%), it failed. This result is in agreement with that of Choi et al. [7] and Ouzaid et al. [1].
Figure 2: (a and b) NCCT of the abdomen and pelvis show axial and coronal views showing a hyperdense stone observed in the middle calyx. (c and d) After the first session of extracorporeal shock wave lithotripsy (ESWL), axial and coronal views show a residual small stone observed in the middle calyx. (e and f) After the second session of ESWL, axial and coronal views show complete clearance of the left middle calyx stone

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Clearance of lower calyx stones depends on other additional factors such as pelvicalyceal height, infundibulopelvic angle, and diameter and height of the infundibulum [10],[22], which will require more research using precontrast and postcontrast MDCT.

Considering ureteric stones, the middle third of the ureter showed the highest success rate (100%) of ESWL. In the upper third of the ureter, four patients (80%) showed success and one patient showed ESWL failure. The failed upper ureteric stone was not related to stone location alone but also the increased stone size (maximum diameter 14 mm) and density (1092 HU in density). In the lower ureter, 12 patients (80%) showed ESWL success and three patients (20%) showed ESWL failure.

This result indicates that the location of a stone in the urinary tract plays a role, but in combination with other factors in predicting the outcome of ESWL, and this is in agreement with Choi et al. [7] and Wiesenthal et al. [5].

In our study, patients were divided according to SSD into two groups: first group (SSD ≤ 10 cm) included 33 patients (61.1%) and the second group (SSD >10 cm) included 21 patients (38.9%).

In the first group (SSD ≤ 10 cm), the overall success rate was 93.9% and the failure rate was 6.1%. In the second group (SSD >10 cm), the overall success rate was 85.7% and the failure rate was 14.3%.

This result indicates that SSD alone cannot be considered as a key factor for ESWL success and a combination of SSD and other factors may be useful in predicting the outcome of ESWL. This is in agreement with Tanaka et al. [2], Choi et al. [7], and Wiesenthal et al. [5].


  Conclusion Top


Smaller size stones will increase the success rate of ESWL. Kidney stones less than 2 cm and ureteric stones less than 1 cm in size are more suitable for ESWL and yield good results. In terms of density, smaller density stones will increase the success rate of ESWL. The suitable stone density for ESWL is usually below 1000 HU; stone densities less than 500 usually require one session, whereas stone densities ranging from 500 to 1000 HU usually require two sessions.

Stone location plays a role, but in combination with other factors, in predicting the outcome of ESWL.

MDCT provides accurate size and density of the stone in addition to accurate anatomical details of vital structures, providing valuable data for management decisions and predicting the outcome of ESWL.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Kambadakone AR, Eisner BH, Catalano OA, Sahani, DV. New and evolving concepts in the imaging and management of urolithiasis: urologists' perspective. Radiographics 2010; 30:603–623.  Back to cited text no. 1
    
2.
Pearle MS, Calhoun EA, Curhan GC. Urologic diseases in America project: urolithiasis. J Urol 2005; 173:848–857.  Back to cited text no. 2
    
3.
Cheng PM, Moin P, Dunn MD, Boswell, WD, Duddalwar, VA. What the radiologist needs to know about urolithiasis: part 1-pathogenesis, types, assessment, and variant anatomy. Am J Roentgenol 2012; 198:W540–W547.  Back to cited text no. 3
    
4.
Eisner BH, McQuaid JW, Hyams E, Matlaga, BR. Nephrolithiasis: what surgeons need to know. Am J Roentgenol 2011; 196:1274–1278.  Back to cited text no. 4
    
5.
Gupta NP, Ansari MS, Kesarvani P, Kapoor, A, Mukhopadhyay, S. Role of computed tomography with no contrast medium enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi. BJU Int, 2005; 95:1285–1288.  Back to cited text no. 5
    
6.
Chaussy C, Brendel W, Schniedt E. Extracorporeally induced destruction of kidney stones by shock waves. Lancet 1980; 2:1265–1282.  Back to cited text no. 6
    
7.
Choi JW, Song PH, Kim HT. Predictive factors of the outcome of extracorporeal shockwave lithotripsy for ureteral stones. Korean J Urol 2012; 53:424–430.  Back to cited text no. 7
    
8.
Bandi G, Meiners RJ, Pickhardt PJ, Nakada SY. Stone measurement by volumetric three-dimensional computed tomography for predicting the outcome after extracorporeal shock wave lithotripsy. BJU Int 2009; 103:524–528.  Back to cited text no. 8
    
9.
Ceban E. The treatment of the reno-ureteral calculi by extracorporeal shockwave lithotripsy (ESWL). J Med Life 2012; 5:133–138.  Back to cited text no. 9
    
10.
10Azab, S, Osama, A. Factors affecting lower calyceal stone clearance after extracorporeal shock wave lithotripsy. Afr J Urol 2013; 19:13-17.  Back to cited text no. 10
    
11.
11Grosjean R, Daudon M, Chammas MF, Claudon M, Eschwege P, Felblinger J, et al. Pitfalls in urinary stone identification using CT attenuation values: are we getting the same information on different scanner models? Eur J Radiol 2013; 82:1201–1206.  Back to cited text no. 11
    
12.
12Tanaka M, Yokota E, Toyonaga Y, Shimizu F, Ishii Y, Fujime M, et al. Stone attenuation value and cross-sectional area on computed tomography predict the success of shock wave lithotripsy. Korean J Urol 2013; 54:454–459.  Back to cited text no. 12
    
13.
13Hameed DA, Elgammal MA, ElGanainy EO, Hageb A, Mohammed K, El-Taher A, et al. Comparing non contrast computerized tomography criteria versus dual X-ray absorptiometry as predictors of radio-opaque upper urinary tract stone fragmentation after electromagnetic shockwave lithotripsy. Urolithiasis 2013; 41:511–515.  Back to cited text no. 13
    
14.
14Nakamura K, Tobiume M, Narushima M, Yoshizawa T, Nishikawa G, Kato Y, et al. Treatment of upper urinary tract stones with extracorporeal shock wave lithotripsy (ESWL) Sonolith vision. BMC Urol 2011; 11:26.  Back to cited text no. 14
    
15.
15Wiesenthal JD, Ghiculete D, Honey RJ, Pace KT. Evaluating the importance of mean stone density and skin-to-stone distance in predicting successful shock wave lithotripsy of renal and ureteric calculi. Urol Res 2010; 38:307–313.  Back to cited text no. 15
    
16.
16Mohamed E, Gamal MAM, Mansour B, Sheri S, Hussein G, Cervando O-V. Management of lower ureteric stones: a prospective study. Cent European J Urol 2013; 66:456–462.  Back to cited text no. 16
    
17.
17Massoud AM, Abdelbary AM, Al-Dessoukey AA, Moussa AS, Zayed AS, Mahmmoud O. The success of extracorporeal shock-wave lithotripsy based on the stone-attenuation value from non-contrast computed tomography. Arab J Urol 2014. (In press).  Back to cited text no. 17
    
18.
Ng CF, Siu DYW, Wong A, Goggins W, Chan, ES, Wong KT. Development of a scoring system from noncontrast computerized tomography measurements to improve the selection of upper ureteral stone for extracorporeal shock wave lithotripsy. J Urol 2009; 181:1151–1157.  Back to cited text no. 18
    
19.
19Pareek G, Hedican SP, Lee FT, Nakada SY. Shock wave lithotripsy success determined by skin-to-stone distance on computed tomography. Urology 2005; 66:941–944.  Back to cited text no. 19
    
20.
20Patel T, Kozakowski K. Skin to stone distance is an independent predictor of stone-free status following shockwave lithotripsy. J Endourol 2009; 23:1383–1385.  Back to cited text no. 20
    
21.
21Ouzaid I, Al-qahtani S, Dominique S, Hupertan V, Fernandez P, Hermieu J-F, et al. A 970 Hounsfield units (HU) threshold of kidney stone density on non-contrast computed tomography (NCCT) improves patients' selection for extracorporeal shockwave lithotripsy (ESWL): evidence from a prospective study. BJU Int 2012; 110:E438–E442.  Back to cited text no. 21
    
22.
22Symes A, Shaw G, Corry D, Choong S. Pelvi-calyceal height, a predictor of success when treating lower pole stones with extracorporeal shockwave lithotripsy. Urol Res 2005; 33:297–300.  Back to cited text no. 22
    


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