Effects of Extracorporeal Shock-wave Lithotripsy onIntrarenal Resistive IndexHasan Nazaroglu1, A. Ferruh Akay2, Yasar Bukte1, Hayrettin Sahin2, Zeki Akkus3 and Aslan Bilici1

From the Departments of 1Radiology, 2Urology, 3Biostatistics, Faculty of Medicine, Dicle University, Diyarbakir, Turkey

(Submitted November 20, 2002. Accepted for publication February 24, 2003)

Scand J Urol Nephrol 37: 408–412; 2003

Objective: This prospective study was performed to determine whether extracorporeal shock-wave lithotripsy (ESWL),widely used for treating renal and ureteral stones, affects the kidney interlobar artery resistive index (RI).Material and Methods: A total of 43 patients (30 with renal and 13 with ureteral stones) underwent color Doppler examinationbefore and 30 min and 3 h after ESWL. Seventeen patients with renal and nine with ureteral stones underwent Dopplerexamination 2 weeks later. Measurements were made near the stones (nearby region), at least 2 cm from the stones (remoteregion) and in the contralateral kidney for renal stones, and in the ipsilateral and contralateral kidneys for ureteral stones.Results: In patients with renal stones, the RI was increased 30 min and 3 h after ESWL in the nearby and remote regions, andmore markedly in the former. In the contralateral kidney, there was an increase in RI only at 3 h, which was less than that inthe ipsilateral kidney. The RI at 2 weeks post-ESWL in the nearby region and contralateral kidney did not differ from the pre-ESWL values. ESWL performed for ureteral stones caused no increase in RI in the ipsilateral kidney.Conclusion: Patients with renal stones had a temporary increase in RI in the hours following ESWL in both the ipsilateral andcontralateral kidneys, which was highest in the region near the stones and lowest in the contralateral kidney. Two weeks later,the RI in both areas had returned to pre-ESWL levels.

Key words: lithotripsy, renal Doppler, resistive index, stone.

Hasan Nazaroglu, MD, Department of Radiology, Faculty of Medicine, University of Dicle, TR-21280 Diyarbakir, Turkey.Tel: �90 412 2488158. Fax: �90 412 2488466. E-mail: hnazarog@dicle.edu.tr

At present, extracorporeal shock-wave lithotripsy(ESWL) is used in the treatment of�90% of all renaland ureteral stones (1). Although its reliability andefficacy have been demonstrated, there are a number ofstudies concerning post-ESWL complications (2–5).However, major life-threatening complications are rarein either the early or late phase (6). Many techniqueshave been used to investigate the effects of ESWL onthe kidneys, one of which involves measurement of theresistive index (RI) in the renal interlobar arteries usingDoppler, a non-invasive diagnostic technique.

In this study, color Doppler ultrasonography wasused to determine whether interlobar RI values wereaffected in patients treated with ESWL for renal andureteral stones.

MATERIAL AND METHODS

The study group comprised 43 patients (27 males, 16females), 30 with renal and 13 with ureteral stones,who underwent ESWL between April 2001 and May2002. Their ages ranged from 18 to 61 years, with meanages of 33 and 35 years in the renal and ureteral stones

groups, respectively. Stone diameter ranged from 6 to18 mm (mean 10 mm).

Stones were diagnosed by means of i.v. urography(IVU), X-ray and ultrasonography. Patients withnormal kidney function on IVU and normal parench-ymal echo on ultrasonography were included in thestudy. Patients with diabetes mellitus, renal parenchy-mal disease or urinary system infections were ex-cluded. Patients with hypertension (diastolic bloodpressure�90 mmHg and/or systolic blood pressure�140 mmHg) and patients receiving hypertensivetherapy were also excluded. Among patients with renalstones (calyceal and pelvis renalis stones), those withectasia in the collecting system were excluded. Amongpatients with ureteral stones, those with mild ectasiawere not excluded, although those with marked ectasiaor decreased cortical thickness were excluded.

ESWL was performed using a Nova (Direx MedicalSystems, Pedach Tikva, Israel) lithotripter. The aver-age number of shock waves per patient was 2420(range 1500–3000). The mean maximum voltage was21.6 kV (range 19–22 kV). Patients received 50 mg ofpethidine hydrochloride prior to ESWL with inter-mittent fluoroscopy.

2003 Taylor & Francis.ISSN 0036–5599DOI 10.1080/00365590310006354 Scand J Urol Nephrol 37

ORIGINAL ARTICLE

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Color Doppler examinations were performed on aToshiba Model SSH 140A instrument (Toshiba Cor-poration Medical Systems Division, Tokyo, Japan)using a 3.75-MHz convex transducer. In the studygroup, measurements were made in the renal interlobararteries prior to and 30 min and 3 h after ESWL. Inaddition, 17 patients with renal stones and nine withureteral stones underwent color Doppler examination 2weeks after ESWL. For renal stones, measurementswere made in the vicinity of the stones (nearby region),at a distance of at least 2 cm from the stones (remoteregion) and in the contralateral kidney. For ureteralstones, measurements were made in the ipsilateral andcontralateral kidneys. Measurements were made whenthree similar waves were registered sequentially.Measurements were repeated three times for eachregion, and the RI value recorded for each region wasthe arithmetic mean of these three measurements.

The pairedt-test, a parametric test, was used tocompare RI values at 30 min and 3 h post-ESWL withpre-ESWL values in the renal stones group. The pairedt-test was also used to compare RI values in the nearbyand remote regions with those in the contralateralkidney for the pre-ESWL measurement and both post-ESWL measurements. The Mann–Whitney U-test wasused to compare the RI values for the two renal stonessubgroups: calyceal and pelvis renalis stones. Wil-coxon’s signed ranks test, a non-parametric test, wasused for comparison of the other subgroup.

RESULTS

Mean blood pressure in patients with renal stones was113/71 mmHg before and 115/74 mmHg after ESWL.Mean blood pressure in patients with ureteral stoneswas 117/74 mmHg before and 116/75 mmHg afterESWL. No significant changes were found betweenpre- and post-ESWL mean blood pressures for eithergroup. No correlation was found between mean maxi-

mum voltage or average number of shock waves andchanges in RI at 30 min and 3 h post-ESWL.

In patients with renal stones, RI (mean� SD) in thenearby region was 0.59� 0.05 before ESWL, increas-ing to 0.62� 0.06 at 30 min and to 0.63� 0.04 at 3 hpost-ESWL. Both post-ESWL values were signifi-cantly different from the pre-ESWL values (p =0.001). In the remote region, the pre-ESWL and 30-min and 3-h post-ESWL RI values were 0.58�0.05, 0.61� 0.05 and 0.61� 0.05, respectively; bothpost-ESWL values were significantly higher thanthe pre-ESWL value (p = 0.003 and 0.001, respec-tively). In the contralateral kidney, RI values beforeand 30 min and 3 h after ESWL were 0.58� 0.05,0.59� 0.05 and 0.60� 0.04, respectively. There wasan increase in RI after ESWL in the contralateralkidney; this difference was not significant at 30 min(p > 0.05) but was significant at 3 h after ESWL(p = 0.036). Differences between pre- and post-ESWLvalues in the nearby and remote regions and in thecontralateral kidney are shown in Fig. 1. There were nosignificant differences between RI in the nearby orremote regions and in the contralateral kidney beforeESWL (p > 0.05); there were, however, significantdifferences 30 min after ESWL (p = 0.001 and 0.042,respectively). There was also a significant difference3 h after ESWL between RI values in the nearby regionand contralateral kidney (p = 0.001), although notbetween those in the remote region and contralateralkidney (p > 0.05). There was a significant difference3 h post-ESWL between RI in the nearby and remoteregions (p = 0.002).

RI was measured in 17 patients with renal stones 2weeks later (Table I). There were no statisticallysignificant differences between RI values in the nearbyor remote regions and those in the contralateral kidneyeither before or 2 weeks after ESWL (p > 0.05). RIvalues in the nearby region and contralateral kidney 2weeks after ESWL did not differ significantly from

Fig. 1. Changes in renal RIvalues in patients with renalstones before ESWL and30 min and 3 h after.

Scand J Urol Nephrol 37

Effect of ESWL on intrarenal resistive index 409

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those before ESWL (p > 0.05). However, valuesrecorded in the remote region 2 weeks after ESWLwere significantly higher than those recorded beforeESWL (p = 0.016).

Mean RI values for the calyceal and pelvis renalissubgroups of the renal stones group are presented inTables II and III; there were no statistically significantdifferences between the calyceal and pelvis renalissubgroups in terms of pre- and post-ESWL RI values inthe nearby or remote regions and the contralateralkidney (p > 0.05).

In patients with ureteral stones, there was a slightincrease in RI values after ESWL in both the ipsilateraland contralateral kidneys (Table IV). There was nosignificant difference between pre-ESWL RI valuesand those 30 min and 3 h post-ESWL in the ipsilateralkidney in patients with ureteral stones (p > 0.05). Therewas also no statistically significant difference in thecontralateral kidney between pre-ESWL and 30-minpost-ESWL values (p > 0.05), but there was a sig-nificant difference between pre-ESWL and 3-h post-ESWL values (p = 0.027). No significant difference inRI values was determined in the ipsilateral and contra-lateral kidneys before and 30 min and 3 h after theprocedure in patients with ureteral stones (p > 0.05).

RI was measured in nine patients with ureteral stones2 weeks after ESWL (Table V); there was no statis-

tically significant difference between these values andpre-ESWL values in either the ipsilateral or contra-lateral kidney, and nor was there any significantdifference between ipsilateral and contralateral renalRI values, both before and 2 weeks after ESWL.

DISCUSSION

ESWL has been used since the 1980s for the treatmentof urolithiasis, and its efficacy and reliability have beenestablished. A number of methods have been used toinvestigate post-ESWL changes in the kidney, includ-ing IVU, ultrasonography, CT, MRI, radionucliderenography and serum and urine analyses (2–4, 7–9).Although complications necessitating surgery, such ashematoma, are rare (6), MRI studies have revealedpost-ESWL change rates as high as 74% (2).

In studies of the effects of ESWL on renal RI usingDoppler ultrasonography, a non-invasive method,measurements have been made at different timespost-ESWL (10–14). In the series of Derchi et al.(10) involving 20 patients with calyceal stones, RIvalues in the region near the stones were higher thanpre-ESWL values 1 h, but not 1 day, after ESWL.Beduk et al. (11) found no difference in RI values in theipsilateral kidney before ESWL and 24 h after. Aoki etal. (12) compared RI values in the region near the renal

Table I. RI values (mean � SD) measured in patients with renalstones before and 2 weeks after ESWL

Region Before ESWL 2 weeks after ESWL

Nearby 0.58� 0.06 0.59� 0.05Remote 0.57� 0.05 0.59� 0.05Contralateral kidney 0.58� 0.05 0.58� 0.05

Table II. RI values (mean � SD) measured in patients with calyceal stones before ESWL and 30 min and 3 h after

Region Before ESWL 30 min after ESWL 3 h after ESWL

Nearby 0.59� 0.04 0.63� 0.06 0.63� 0.04Remote 0.59� 0.05 0.62� 0.05 0.61� 0.05Contralateral kidney 0.58� 0.04 0.59� 0.05 0.60� 0.04

Table IV. Renal RI values (mean � SD) measured in patients with ureteral stones before ESWL and 30 min and 3 h after

Kidney Before ESWL 30 min after ESWL 3 h after ESWL

Ipsilateral 0.59� 0.03 0.60� 0.05 0.61� 0.05Contralateral 0.58� 0.03 0.59� 0.04 0.61� 0.05

Table III. RI values (mean � SD) measured in patients with pelvis renalis stones before ESWL and 30 min and 3 h after

Region Before ESWL 30 min after ESWL 3 h after ESWL

Nearby 0.58� 0.07 0.61� 0.05 0.63� 0.04Remote 0.58� 0.06 0.60� 0.05 0.61� 0.05Contralateral kidney 0.59� 0.06 0.60� 0.06 0.60� 0.04

Table V. Renal RI values (mean � SD) measured in patients withureteral stones before and 2 weeks after ESWL

Kidney Before ESWL 2 weeks after ESWL

Ipsilateral 0.59� 0.03 0.58� 0.02Contralateral 0.57� 0.04 0.57� 0.03

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stones before ESWL and 30 min and 1 week after,finding that they were significantly increased at 30 minbut had returned to pre-ESWL levels after 1 week. Weobtained similar results in the present study. Knapp etal. (13) found higher RI values in the nearby regionwithin 3 h after ESWL than before the procedure, andthere was also a positive linear correlation betweenpatient age and post-ESWL RI. Aoki et al. (12), on theother hand, found no correlation between patient ageand post-ESWL RI.

Janetschek et al. (14) divided their patients into threeage groups: <40 years, 40–59 years and�60 years;they found that RI values in the nearby region within3 h after ESWL were not significantly higher than pre-ESWL values in the first two groups, but that they weresignificantly higher in the third group. Despite the factthat our study group comprised younger patients, themean age of patients (n = 30) with renal stones being33 years (range 18–52 years), values in the nearbyregion at 30 min and 3 h post-ESWL were significantlyhigher than pre-ESWL values.

Derchi et al. (10) found slightly higher RI values3 cm from the calyceal stones at 1 h post-ESWL,although the difference was not statistically significant;1 day later, they had returned to pre-ESWL values. Inthe present study, we found increased RI values at least2 cm from the stones at 30 min and 3 h post-ESWL.Interestingly, although there was no difference betweenpre-ESWL and 2-weeks post-ESWL values in thenearby region and the contralateral kidney, there was astatistically significant difference in the remote region;we are unable to account for this.

Janetschek et al. (14) measured RI before ESWL andwithin 3 h and 26 months after and found no significantdifferences in RI values in treated and non-treatedregions of the ipsilateral kidney. However, in thepresent study, we found a significant difference at 3 hpost-ESWL between RI values in the nearby andremote regions, those in the former being higher.

Knapp et al. (13) found no difference in RI values inthe contralateral kidney before ESWL and within 3 hafter. Aoki et al. (12), on the other hand, found that RIlevels in the contralateral kidney were significantlyhigher 30 min after ESWL in patients aged >60 years,but found no such increase in younger patients.Although the mean age of our renal stones group waslower than that of Aoki et al., and there were nopatients aged >60 years in our group, RI values in thecontralateral kidney were significantly higher at 3 hpost-ESWL than before the procedure. Willis et al. (15)investigated the effects of ESWL on mini-pig kidneys,finding decreased renal plasma flow at 1 and 4 h in boththe ipsilateral and contralateral kidneys, the decreasebeing more marked in the kidney that underwentESWL. In the present study, RI was increased after

ESWL in the contralateral kidney, but this increase waslower than that in the nearby region of the ipsilateralkidney; this finding supports that of Willis et al.

Johansson et al. (16) measured the interlobarpulsatility index (PI), finding it to be significantlyincreased at 2 h post-ESWL in the ipsilateral kidney inpatients who had received a morphine analgesic(meperidine 50 mg) before the procedure. They alsodetermined a significant increase in the PI value in thecontralateral kidney. There was no significant differ-ence in patients who had not received meperidine.Because these researchers did not state the pre- andpost-ESWL RI values, it is not possible to determinewhether there was a significant change in RI values. Asall patients in the present study were given 50 mg ofpethidine hydrochloride before ESWL, we were unableto determine whether narcotic analgesic administrationaffected RI. Nonetheless, the absence of any change inRI on the ipsilateral side in patients undergoing ESWLfor ureteral stones shows that narcotic usage is not thecause of increased RI at 30 min and 3 h post-ESWL.

Hypertension occurring after ESWL is a subject ofdispute. Janetschek et al. (14) reported that RI wassignificantly increased within 3 h of ESWL in a groupof patients aged >60 years who were followed up for 26months, and that this increase was even more pro-nounced at 26 months post-ESWL in the group whodeveloped hypertension. Eight of the nine patients inthis group who developed hypertension had increasedRI values within 3 h of the procedure. In their secondgroup (patients aged 40–59 years), hypertensionoccurred in only one patient 26 months after ESWL.In a randomized, controlled clinical study (17), it wasreported that ESWL did not lead to changes in bloodpressure. Although there is an increase in RI values inthe first hours following ESWL, RI subsequentlyreturns to normal levels. We think that hypertensiondue to ESWL is less likely to develop in patients aged<60 years.

Urinary enzyme tests are used in the diagnosis andfollow-up of many types of renal damage. There is atemporary increase in urinary enzyme excretion afterESWL, which reaches its highest level at 1–3 days, andthen decreases, reaching normal levels by Day 28 (7).ESWL leads to a temporary increase in active reninconcentration. Strohmaier et al. (18) determined thatactive renin concentration was increased immediatelyand 1 day after ESWL, but that on Days 3 and 5 therewas no statistically significant difference compared topre-ESWL levels. They found no difference in endo-thelin concentrations before and after the procedure.

In conclusion, there is a temporary increase in RIvalues in the hours following ESWL in both theipsilateral and contralateral kidneys, which is mostmarked in the region near the renal stones and least

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marked in the contralateral kidney. RI values in thenearby region and contralateral kidney return to normalwithin 2 weeks.

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