The Ideal Time Interval Between Repeated Shock Wave Lithotripsy Sessions For Renal Stones: A Randomized Controlled Trial

There is no consensus about the required time intervals between repeated SWL sessions applied for renal stones with some centers waiting for 3 days, others for one week and others up to one month to repeat lithotripsy. In the 2019 EUA guidelines stated that "There are no conclusive data on the intervals required between repeated SWL sessions. However, clinical experience indicates that repeat sessions are feasible (within 1 day for ureteral stones).

The intense use of ESWL currently, the lack of knowledge about acute lesions caused by re-treatment within a short time interval and the empirical way by which treatment is conducted, stimulated us to search for a precise answers to the question What the ideal time interval between SWL sessions in the treatment of renal stone patients should be.

This randomized controlled trial will be conducted at Urology and Nephrology Center in Mansoura, Egypt. Patients more than 18 years old with single primary renal stone fulfilling inclusion criteria will be randomly allocated to 3 groups (50 patients each).Group 1 will undergo SWL with 3 days between each session. Group 2 will undergo SWL with 7 days between each session and Group 3 will undergo SWL with 14 days between each session.

Study parameters will be renal damage including the following items:

* Tubular damage will be assessed through estimation of changes in urinary excretion of renal tubular enzyme kidney injury molecule 1(KIM-1).
* Glomerular damage will be assessed by estimation of proteinuria and changes in GFR calculated by renal isotope scan.
* Renal morphological and haemodynamic changes.
* Treatment success is defined as clinically insignificant residual fragments less than 4 mm size.

STUDY DESIGN:

Randomized Trial

STUDY SETTING/LOCATION:

The study will be conducted in a single tertiary center, Urology and Nephrology Centre in Mansoura, Egypt.

STUDY POPULATION:

Adults (\>18years) with primary single renal stone amenable for SWL according to EUA guidelines (C. TÜRK, 2019) .

Inclusion criteria Adult patient with ≤ 2 cm single calyceal renal stone in a normal functioning kidney.

Exclusion criteria:

1. Contraindications to ESWL:

   * Uncontrolled Hypertension
   * Renal insufficiency
   * Diabetic patient
   * Coagulopathy
   * Morbid obesity
   * Upper urinary tract obstruction
   * Active urinary tract infection
2. Previous surgical or SWL treatment of renal stones.
3. Congenital renal anomalies and solitary kidney
4. Pediatric patients (age \<18 years). STUDY GROUPS Patient fulfilling the study criteria will be randomly allocated to one of three groups (50 Patient in each): Group 1 will undergo SWL with 3 days between each session. Group 2 will undergo SWL with 7 days between each session and Group 3 will undergo SWL with 14 days between each session.

Each patient will serve as internal control through comparing both pre-ESWL and post-ESWL values of our study parameters. / Candidates Potential participants will be invited to participate in this study after signing an informed consent. Potential participants will be given enough information, in a way they will understand, about the potential risks and benefits of being involved in this clinical study.

Baseline evaluation (Before ESWL) (S0):

Complete history and physical examination. Laboratory Investigations

Blood Samples:

Blood sample will be withdrawn Pre-ESWL (B.S0) for:

* CBC
* Serum creatinine
* Prothrombin concentration

Urine Samples:

* Samples of urine will be obtained before ESWL session(U.S0) for Urine analysis \&estimation of KIM-1
* Urine culture will be obtained in cases of pyuria

Radiological investigation:

* NCCT will be performed. Stone criteria will be identified as regard to volumes, site, location, stone density and associated hydronephrosis.
* I.V.P (intravenous pyelography) will be performed if needed to exclude the presence of narrow neck calyx or stones in closed calyces.
* Dynamic renal scintigraphic scanning using technetium-99m Diethylene Triamine Pentaacetic Acid (TC-99m DTPA). The renal uptake, percentage of uptake from the injected dose, split function, ERPF, corrected glomerular filtration rate (GFR), time to peak clearance (T max), and half-time clearance will be calculated, because these parameters are helpful indicators in the evaluation of renal function.
* Functional MRI assessment to evaluate the renal tissue oxygenation using Blood-Oxygen Level Dependent (BOLD) and possible anatomical changes

Randomization Randomization will be performed using computer generated, sequentially numbered method.

Procedure technique:

The following protocol will be applied for all patients in study groups. SWL will be performed using the Dornier Gemini lithotripter (Dornier MedTech, Wessling, Germany) . A total of 3 000 shocks will be delivered at 80 shocks/min. The patient will receive 1 mg/kg pethidine i.v. for analgesia. Treatment will begin at machine power step 1, which will deliver 49 MPa focal pressure and 0.35 mJ/mm2. Power will be gradually increased by one step for each 200 shocks up to step 4, which deliver 70 MPa and 0.7 mJ/mm2. The maximum session number will be 3 session. Patient treated with \<2 sessions will be excluded from the analysis.

After 1st ESWL session:

* Urine sample will be obtained 2to 4 hours after the end of the first session (U.S1) for estimation of urinary proteinuria and estimation of KIM-1
* Visual analogue scale will be compared between the study groups
* Non contrast spiral CT (low dose) will be performed before 2nd session to detect residual fragments, presence of obstruction and the need for re-treatment.
* Functional MRI assessment to evaluate the renal tissue oxygenation.

After 2nd ESWL session:

* Urine sample will be obtained after 2 to 4 hours after the second session (U.S2) for proteinuria and estimation of KIM-1.
* Visual analogue scale.
* Non contrast spiral CT (low dose will be performed before 3rd session to detect residual fragments, presence of obstruction and the need for re-treatment.
* Functional MRI assessment to evaluate the renal tissue oxygenation.

After 3 months of the treatment :

* Samples of urine will be obtained after 3 month from the start of treatment U.S3 for Urine analysis \& estimation of urinary proteinuria and estimation of KIM-1
* Blood sample will be withdrawn (B.S3) for:

  * CBC
  * Serum creatinine and calculation of eGFR values
* NCCT will be done after 3 months of the last session of ESWL for detection of the stone free rate.
* Dynamic renal scintigraphic scanning using TC-99m DTPA as described before.
* Functional MRI assessment to evaluate the renal tissue oxygenation Statistical analysis Analysis of data will be performed with Statistical Package for Social Science (SPSS) software. Continuous data will be presented as mean ± SD when normally distributed and as medium and range when non-normally distributed. Categorical data will be presented as frequency and percentage. Comparison between mean ± SD between the three groups will be carried out by ANOVA test. Comparison between the median and range between the 3 groups will be performed by Kruskal -Wallis test. Comparison between categorical variables between groups will be performed using Chi-square or Fisher Exact test as appropriate. Regression analysis to estimate the best model which can predict the related kidney injury. In all comparison, a P.value \< 0.05 will be considered significant.

Eligibility Criteria:
Inclusion criteria Adult patient with ≤ 2 cm single calyceal renal stone in a normal functioning kidney.

Exclusion criteria:

1. Contraindications to ESWL:

   * Uncontrolled Hypertension
   * Renal insufficiency
   * Diabetic patient
   * Coagulopathy
   * Morbid obesity
   * Upper urinary tract obstruction
   * Active urinary tract infection
2. Previous surgical or SWL treatment of renal stones.
3. Congenital renal anomalies and solitary kidney
4. Pediatric patients (age \<18 years).