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ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 4  |  Page : 1352-1357

Predictive factors of renal and ureteric stone disintegration by the extracorporeal shock wave lithotripsy


1 Department of Urology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Urology at Ministry of Health, Shebin El-Kom, Menoufia, Egypt

Date of Submission29-Apr-2020
Date of Decision24-Jun-2020
Date of Acceptance26-Jun-2020
Date of Web Publication24-Dec-2020

Correspondence Address:
Mohamed G Elmarakbey
MBBCh, Berket El-Sabae, Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_122_20

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  Abstract 


Objective
The objective of this work was to evaluate possible predictive variables for the outcome of shock wave lithotripsy of renal and ureteric stones.
Background
Nephrolithiasis is a common disease affecting the population with a peak incidence at around the third to fourth decade of life. The prevalence of stone disease is increasing with increasing annual expenditure. Extracorporeal shock wave lithotripsy (ESWL) is the preferred treatment for renal and several ureteral calculi owing to its noninvasive characteristic and its favorable clinical outcome.
Patients and methods
This study was carried out on 100 patients who are supposed to be treated with ESWL and diagnosed with renal or ureteric stone. All cases were evaluated before, during, and after the procedure as follows: full medical history, clinical examination, laboratory investigations, and radiological investigations.
Results
A total of 91 of the studied patients were males. Age of the studied patients ranged from 24 to 58 years, with a mean of 38.72 years. There is a significant relation between need for second session and presence of tenderness, hypertension and stone site, international normalized ratio, operation duration, complaint duration, stone size, and Hounsfield unit. Presence of renal stone significantly protects from that risk. There are significant relations between postoperative complications and smoking, BMI, urine analysis, hypertension, and past history of stone. There are significant relations between postoperative complications and need for second session, serum creatinine, operation duration, and stone size.
Conclusion
ESWL is an effective and reasonable initial therapy in the management of ureteral stones 2 cm or less at all levels of the ureter.

Keywords: extracorporeal shock wave lithotripsy, kidney, renal stone, ureter, ureteric stone, urinary tract stone, urinary tract


How to cite this article:
Elserfy FA, Abd-AlBaky TM, El Sherif EA, Elmarakbey MG. Predictive factors of renal and ureteric stone disintegration by the extracorporeal shock wave lithotripsy. Menoufia Med J 2020;33:1352-7

How to cite this URL:
Elserfy FA, Abd-AlBaky TM, El Sherif EA, Elmarakbey MG. Predictive factors of renal and ureteric stone disintegration by the extracorporeal shock wave lithotripsy. Menoufia Med J [serial online] 2020 [cited 2021 Apr 19];33:1352-7. Available from: http://www.mmj.eg.net/text.asp?2020/33/4/1352/304480




  Introduction Top


Nephrolithiasis is a common disease affecting the population, with a peak incidence at around the third to fourth decade of life. The lifetime risk of urolithiasis in the general population is approximately three times higher in men as compared with women[1].

The prevalence of stone disease is increasing with increasing annual expenditure. Socioeconomic status, environmental factors, genetic predisposition, and certain metabolic disorders are some of the known risk factors of this disease[2].

Various factors such as size of calculi, severity of symptoms, degree of obstruction, renal function, location of stone, and the presence or the absence of associated infection influence the choice of one type of intervention over the others[3].

Before the 1980s, open surgery represented the treatment of choice for most renal and ureteral stones. Meanwhile, open surgery for stones nearly vanished by the continuous refinement of minimal invasive surgical procedures such as ureterorenoscopy and percutaneous nephrolitholapaxy as well as by the introduction of extracorporeal shock wave lithotripsy (ESWL). Facing these various options of stone therapy, ESWL has been established as the preferred treatment for renal and several ureteral calculi owing to its noninvasive character and its favorable clinical outcome. Generally, ESWL is characterized by a low complication rate and only by a few absolute contraindications[4].

Modern stone therapy should ensure high effectiveness combined with a low complication rate by maneuvers that avoid patient discomfort and engender minimal disability. However, ESWL may not always meet these criteria. An accurate estimation of the individual's probability of stone clearance may be essential for proper treatment selection to determine who will experience maximum benefit from ESWL. The identification of prognostic factors compromising the clinical outcome of ESWL-treated calculi might be crucial to the option for the most appropriate maneuver[5].

Complex stone formation such as staghorn calculi or a high stone mass is cumbersome for ESWL. Usually, an increased stone burden is directly related to the retreatment rate. To this end, an upper size of 2 cm is regarded as a rational limit for calculi amenable for ESWL. Beside the stone size, obesity has also been identified as a delimitating factor for the success of ESWL treatment[6].

Stones of varying composition respond differently to shock wave fragmentation. Subsequently, fragility of calculi is also recognized to represent an essential factor for the success rate of ESWL[7].

Disintegration is lessened in stones composed of cystine, brushite, and calcium oxalate monohydrate, whereas calculi made up of calcium oxalate dehydrate and uric acid are much more susceptible to ESWL. The preoperative knowledge about stone composition might be useful to estimate ESWL outcome and helpful for selecting the preferred treatment option. Unenhanced helical computed tomography (CT) scanning has been established as an attractive contrast-free alternative imaging technique to intravenous pyelography for the diagnosis of renal as well as ureteral calculi. Possible advantages are a rapid determination of stone location as well as the detection of alternative diagnoses. Unenhanced helical CT also allows the possibility of predicting the stone composition by the determination of Hounsfield unit (Hu)[8].

The aim of this study was to evaluate possible predictive variables for the outcome of ESWL of renal and ureteric stones.


  Patients and methods Top


This prospective study was carried out on 100 patients who are supposed to be treated with ESWL and diagnosed with renal or ureteric stone.

All cases were evaluated after approval of the Ethical Committee of the Faculty of Medicine, Menoufia University, in the period between January 2018 to January 2020.

Inclusion criteria

The inclusion criteria were patients with renal and upper ureteric stones detected by imaging (Kidney, Ureter, and Bladder X-ray (KUB), ultrasound, or CT) indicated for ESWL as a primary management, stone size less than 4 mm, and stones that are solitary and radiopaque on the pretreatment plain radiography.

Exclusion criteria

Patients with skin disease or hypersensitivity, patients with elevated serum creatinine level more than 2 mg/dl, patients with bleeding disorders, patients more than 120 kg body weight, patients with incisional lumbar hernia, patients with active urinary tract infection or urosepsis, and patients with ureteral stricture, neurogenic bladder, or polycystic kidney were the exclusion criteria.

Methods

Patients were evaluated before, during, and after the procedure as follows: full medical history; clinical examination; laboratory investigations, including complete urine analysis when indicated, urine culture in cases with pyuria, serum creatinine, complete blood picture, random blood sugar, and electrolytes (Na and K).

Radiological investigations

Plain KUB was done for all patients. Abdominopelvic ultrasonography was done for all patients. Abdominopelvic search results featured snippets from the web. CT without contrast was done for all patients to measure stone density in HU.

Intraoperative evaluation

It included operative time, fragmentation time, and stone size (determined by measuring the longest diameter on preoperative radiological investigation).

Postoperative evaluation

It included hospital stay, analgesic requirements, need for secondary session postoperatively, and postoperative complications.

Follow-up

All patients were evaluated after each ESWL session with plain KUB, pelviabdominal ultrasound for radiolucent stones, or may be noncontrast abdominopelvic CT if any of them is not conclusive. If inadequate stone fragmentation is present and there is significant residual fragment, another session of ESWL is indicated.

Residual fragments are considered significant if it is 4 mm or more. So, less than 4 mm fragments are considered clinically insignificant stone fragments. Chemical analysis of the stone fragmented may be considered especially for recurrent cases and also for children by collecting urine in containers or micturating through a sheet of gauze.


  Results Top


A total of 91 of the studied patients were males, and 44% were from urban areas, the same percentage worked as professionals (doctor, engineer, and teacher), whereas 8% were nonworker. Eighty five percent was married and 48% were smokers. Age of the studied patients ranged from 24 to 58 years, with mean of 38.72 years [Table 1].
Table 1: Distribution of the studied patients according to demographic characteristics

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Three-quarters of the patients needed second session [Figure 1]. Eight patients (20.5% of complicated patients) had fever. Of them, 51.3, 17.9, and 10.3% had hematuria, steinstrasse stone, and subcapsular hematoma, respectively [Figure 2].
Figure 1: Pie chart showing distribution of the studied patients according to need for second admission.

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Figure 2: Pie chart showing distribution of the studied patients according to type of postoperative complications.

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There is a significant relation between need for second session and presence of hypertension. On the contrary, there is a nonsignificant relation between need for second session and past history of other diseases, surgery, or scar [Table 2].
Table 2: Relation between need for second need and laboratory parameters, duration of complaint, duration of operation, and stone characteristics

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There is a significant relation between need for second session and all of international normalized ratio (INR), operation duration, complaint duration, stone size and HU. Nonsignificant relation was present between it and hemoglobin, skin stone distance (SSD), serum creatinine, or total leukocytic count (TLC) [Table 3].
Table 3: Logistic regression for variables independently associated with increased risk of need for second session

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  Discussion Top


ESWL is an attractive treatment modality offering a minimally invasive and convenient treatment option, delivered in an outpatient setting and resulting in low complication rates. Several factors determining the success of ESWL treatment of ureteric stones have been studied. These include the stone site, size, crystal type, degree of obstruction, stone impaction, and function of the renal unit. The success rate is influenced by stone factors (stone size, location, composition, and degree of obstruction), clinical factors (symptom severity, patient's expectations, associated infection, solitary kidney, and abnormal ureteral anatomy), and technical factors (available equipment and cost)[9].

However, it is not certain which factors influence the outcome of ESWL. Thus, this study was carried out on 100 patients who are supposed to be treated with ESWL and diagnosed with renal or ureteric stone to evaluate possible predictive variables for the outcome of ESWL of renal and ureteric stones.

All cases was evaluated before, during, and after the procedure as follows: full medical history, clinical examination, laboratory investigations (including complete urine analysis, urine culture, serum creatinine, complete blood picture, and random blood sugar) and radiological investigations (including plain KUB, abdominopelvic ultrasonography, and abdominopelvic CT without contrast).

Our study showed that 91 of the studied patients were males, 44% were from urban areas, the same percentage worked as professionals (doctor, engineer, and teacher), whereas 8% were nonworker. Eighty five percent was married and 48% were smokers. Age of the studied patients ranged from 24 to 58 years, with mean of 38.72 years.

Choi et al.[10] investigated predictive factors for failure of ESWL for treating ureteral stones. A total of 153 patients who underwent ESWL for ureteral stones diagnosed by non-enhanced spiral CT were divided into two groups: group A, with stone size less than or equal to 10 mm, and group B, with stone size more than 10 mm. The patients' mean age was 54.5 ± 11.78 years (range: 34–74 years) in group A and 55.5 ± 13.28 years (range: 32–79 years) in group B.

Regarding complaints, 51% had left loin pain and 60% had tenderness. Patients complained for 1–4 weeks, with mean duration of 2.52 weeks. Larger percentage of our patients had irrelevant past history or surgery. One-fifth had diabetes and the same percentage had hypertension. Overall, 20% had scar. Serum creatinine ranged from 0.7 to 1.8 mg/dl, with a mean of 1.12 mg/dl. INR ranged from 1 to 1.25, with a mean of 1.03. Hemoglobin ranged from 11.2 to 16 g/dl, with a mean of 13.91 g/dl. Total leukocytic count ranged from 4.6 to 11.4 (103/mm3), with a mean of 7.36 (103/mm3). Overall, 36% had pyuria. Choi et al.[10] found that 25 patients with remnants after ESWL underwent ureteroscopic removal of stone and one patient underwent open ureterolithotomy.

The attenuation value of stones on axial CT images has been studied as a predictor of fragmentation efficiency. However, because these values differ according to the size of the ROI and portion in the same stone, the use of these values in the management of renal and ureteral stones is still problematic[11]. According to stone characteristics by CT in our study, 40% had renal stone by CTUT and 60% had ureteric stone, and of them, eight patients had middle ureteric stone. Overall, 51% had stone on the left side.

In our study, the size of stone ranged from 5 to 13 mm, with a mean of 7.982 mm. HU ranged from 513 to 1455, with a mean of 945.92. Hatiboglu et al.[12] have shown that stone size is an independent predictor of the stone-free rate after ESWL. It has been reported that patients with stones more than 10 mm more frequently fail to be rendered stone free by ESWL.

In the 2007 American Urological Association/European Association of Urology guideline, ureteral stones were classified as either less than or greater than 10 mm. At all locations in the ureter, the treatment outcome for stones less than 10 mm was superior to that for stones greater than 10 mm. Specifically, for stones in the distal ureter, the stone-free rate for stones less than 10 mm treated by SWL was 86%, compared with a 74% stone-free rate for those greater than 10 mm[9]. Choi et al.[10] found that the mean stone size was 6.1 ± 1.36 mm (range: 4.1–10.0 mm) and 14.3 ± 4.65 mm (range: 10.1–22.0 mm) in each group.

In our study, three-quarters of patients needed second session. Overall, 47% had postoperative complications. Eight patients (20.5% of complicated patients) had fever. Of them, 51.3, 17.9, and 10.3% had hematuria, steinstrasse stone, and subcapsular hematoma, respectively.

Apparently, there were some existing risk factors for the development of hematoma. Choi et al.[10] observed a complication rate of 3.2% (n = 5), including acute pyelonephritis (n = 3, 1.9%), which was successfully treated by percutaneous nephrostomy catheterization with antibiotics and a subcapsular hematoma (n = 2, 1.3%) that resolved spontaneously. A static steinstrasse was observed in three patients and analgesics were required in five patients for 1 day for post-ESWL pain.

In our study, there is a significant relation between need for second session and residence. Patients from rural areas showed increased risk by 3.78 folds. There is a nonsignificant relation between need for second session and age, sex, marital status, BMI, occupation, or smoking. Being single, not working, and nonsmoker nonsignificantly increased risk by 4.57, 1.37 and one fold, respectively. Male sex nonsignificantly the decreased risk.

Moreover, there is a significant relation between need for second session and presence of tenderness, hypertension, and stone site, INR, operation duration, complaint duration, stone size, and HU. Patients with no tenderness or with renal stone had lower risk for second session. Free urine analysis nonsignificantly increased risk by 1.96 folds. Right loin pain nonsignificantly decreased risk. On the contrary, there are nonignificant relations between need for second session and past history of other diseases, surgery, scar, side of stone, hemoglobin, SSD, serum creatinine, or TLC.

The utility of BMI in predicting successful ESWL is variable. Pareek et al.[11] found BMI to be a significant predictor of success. Conversely, in another study, BMI failed to predict successful ESWL outcomes, whereas SSD remained a significant predictor[13].

In our study, univariate analysis showed that presence of renal stone significantly protects from that risk (OR = 0). Having job (regardless what is) was a nonignificant protective factor. Increasing stone size and HU significantly increased the risk by 36.183 and 1.046 folds, respectively.

In a clinical retrospective review, patients with calculi more than 750 HU were 10.5 times as likely to need greater than or equal to 3 SWL sessions as were those with calculi of less than or equal to 750 HU. ESWL is more likely to fail for patients with renal calculi greater than 750 to 1000 HU, and these patients should be considered for other treatment modalities[14].

In our study, there are significant relations between presence of postoperative complications and smoking, BMI, result of urine analysis, presence of hypertension, and past history of stone. There are nonsignificant relations between presence of postoperative complications and other demographic characteristics, loin pain, tenderness, past history of other diseases, surgery, scar, stone site, or side. Male sex, living rural areas, and being single nonsignificantly protected with respect to postoperative complications.

Chien et al.[15] determined whether SWL led to the development of hypertension, with controls matched for age, sex, obesity, diabetes mellitus, and hyperlipidemia. They concluded that SWL is a safe procedure for properly managed patients with nephrolithiasis.

In our study, there are significant relations between postoperative complications and need for second session, serum creatinine, operation duration, and stone size. Non-significant relations were present between it and either hemoglobin, complaint duration, TLC, INR, SSD, or HU. Univariate analysis showed that increasing stone size and serum creatinine level increased risk of postoperative complications by 1.952 and 10.814 folds, respectively. On the contrary, normotensive decreased the risk. Many investigators have reported that SSD is a significant predictor in ureteral stones.

Wiesenthal et al.[16] suggested that SSD was a significant predictor of lithotripsy success for ureteral stones. In the multivariate analysis, SSD more than 110 mm was a significant predictor of outcome. Choi et al.[10] used univariate analysis to individually assess the association between the various factors and outcomes. Age, sex, BMI, laterality, location, and HU were not significantly different in terms of outcome of ESWL. The mean stone size in the success and failure groups, was 5.9 ± 1.27 vs 7.5 ± 1.43 mm, respectively, in group A (P < 0.001) and 12.2 ± 2.15 mm vs 19.1 ± 4.15 mm, respectively, in group B (P < 0.001). The mean SSD in the success and failure groups was 102.4 ± 12.88 vs 110.8 ± 5.66 mm, respectively, in group A (P = 0.043) and 97.8 ± 12.97 vs 107.9 ± 13.02 mm, respectively, in group B (P = 0.013). All the secondary signs showed statistically significant differences in terms of outcome of ESWL. In the multivariate logistic regression, stone size was an independent predictive factor for failure of ESWL in group A. Perinephric fat standing and stone size were independent predictive factors in group B. They concluded that stone size is an independent predictive factor influencing failure of ESWL for treating ureteral stones. In larger ureteral stones (>10 mm), the presence of perinephric fat stranding is also an independent predictive factor.

Khalil[17] stated that both URSL and ESWL enable an effective and safe primary treatment option for the impacted stone in the proximal ureter. The URSL has a significant higher initial stone-free rate; however, after three months of follow-up, the stone-free rate of ESWL has been further increased, and the difference between the two procedures becomes insignificant. Although ESWL has a significantly higher re-treatment rate and lower initial stone-free rate, it has the advantage of being non-invasive and outpatient procedure with absence of anesthesia.

Nguyen et al.[18] compared ESWL efficacy at 60 vs 90 pulses per minute using the modified HM-3 lithotripter for solitary ureteral stones. They concluded that optimizing the ESWL delivery rate can achieve excellent results for ureteral stones.

Chen et al.[19] analyzed the prognostic factors that influenced SFR. They suggested that SFR after SWL was independently affected by BMI, stone length, stone width, and stone location. They built a logistic regression formula to predict SFR and to help urologists select the patients who would benefit the most from SWL.


  Conclusion Top


ESWL is an effective and reasonable initial therapy in the management of ureteral stones 2 cm or less at all levels of the ureter. Stone size is an independent predictive factor influencing failure of ESWL in the treatment of renal and ureteral stones.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Tiselius HG, Ackermann D, Alken P, Buck C, Conort P, Gallucci M. Working party on lithiasis: European Association of Urology Guidelines on urolithiasis. Eur Urol 2001; 40:362–371.  Back to cited text no. 5
    
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Choi JW, Song PH, Kim HT. Predictive factors of the outcome of extracorporeal shockwave lithotriopsy for ureteral stones. Korean J Urol 2012; 53:424–430.  Back to cited text no. 10
    
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Hatiboglu G, Popeneciu V, Kurosch M, Huber J, Pahernik S, Pfitzenmaier J, et al. Prognostic variables for shockwave lithotripsy [SWL] treatment success: no impact of body mass index [BMI] using a third generation lithotripter. BJU Int 2011; 108:1192–1197.  Back to cited text no. 12
    
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Ng CF, Siu DY, 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. 13
    
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Gupta NP, Ansari MS, Kesarvani P. Role of computedtomography with no contrast medium enhancement inpredicting the outcome of extracorporeal shockwave lithotripsy for urinary calculi. Br J Urol 2005; 95:1285–1288.  Back to cited text no. 14
    
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Chien T, Lu Y, Chou Y, Wu W, Huang C. Shockwave lithotripsy for renal stones is not associated with development of hypertension in Taiwan's Chinese population. Urol Sci 2017; 28:219–222.  Back to cited text no. 15
    
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Khalil M. Management of impacted proximal ureteral stone: Extracorporeal shock wave lithotripsy vs ureteroscopy with holmium: YAG laser lithotripsy. Urol Ann 2013; 5:88–92.  Back to cited text no. 17
    
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Nguyen DP, Hnilicka S, Kiss B. Optimization of extracorporeal shock wave lithotripsy delivery rates achieves excellent outcomes for ureteral stones: Results of a prospective randomized trial. J Urol 2015; 194:418–423.  Back to cited text no. 18
    
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