Effects of Extracorporeal Shock Wave Lithotripsy to One Kidney on Bilateral Glomerular Filtration Rate and PAH Clearance in Minipigs:

The role of extracorporeal shockwave lithotripsy in an asymptomatic special patient group with small renal calculi

BACKGROUND AND PURPOSE

Data concerning extracorporeal shock wave lithotripsy (SWL) management of small (< or = 5 mm) asymptomatic renal caliceal stones are lacking in the literature. In this study, we aimed to determine the effectiveness of SWL in a special group of patients who had very small (< or = 5 mm) asymptomatic renal caliceal stones. The group of patients consisted of pilots, gendarmes, and soldiers, such as commandos, for whom treatment was obligatory and who had to be stone free because of their military duties.

PATIENTS AND METHODS

We retrospectively examined SWL data and retrieved information for 84 patients with small asymptomatic renal caliceal stones. The SWL sessions were performed with a Siemens Lithostar lithotriptor. The mean age of the patients was 34 +/- 13 years. The mean stone size was 4.8 +/- 0.4 mm. The mean numbers of shockwaves and energy used were 2707 +/- 1742 and 18 +/- 2 kV, respectively. The location of stones were: 11 right upper calix, 10 right middle calix, 17 right lower calix, 13 left upper calix, 16 left middle calyx, and 17 left lower calix. Eighty-four patients underwent 101 SWL sessions. Only eight patients had second and three patients had third SWL treatments. SWL was performed five times for only one patient. All mean values were realized with an SPSS 10.0 statistical program.

RESULTS

After the first, second, and third SWL sessions, the stone-free rate was calculated as 87%, 93% and 94%, respectively. Only five patients with lower renal caliceal stones were not stone free. The reported complications were macroscopic hematuria necessitating medical attention in four patients, skin ecchymosis in seven patients, severe colic pain in two patients, and urinary-tract infection in one patient. There was no need for hospitalization for these complications.

CONCLUSION

SWL is effective and safe in patients with very small (< or = 5 mm) asymptomatic renal caliceal stones in all locations.

In vitro evaluation of canine and feline calcium oxalate urolith fragility via shock wave lithotripsy

OBJECTIVE

To test the hypothesis that feline calcium oxalate uroliths are intrinsically more resistant to comminution via shock wave lithotripsy (SWL) than canine calcium oxalate uroliths through comparison of the fragility of canine and feline uroliths in a quantitative in vitro test system.

SAMPLE POPULATION

Calcium oxalate uroliths (previously obtained from dogs and cats) were matched by size and mineral composition to create 7 pairs of uroliths (1 canine and 1 feline urolith/pair).

PROCEDURE

Uroliths were treated in vitro with 100 shock waves (20 kV; 1 Hz) by use of an electrohydraulic lithotripter. Urolith fragmentation was quantitatively assessed via determination of the percentage increase in projected area (calculated from the digital image area of each urolith before and after SWL).

RESULTS

After SWL, canine uroliths (n = 7) fragmented to produce a mean +/- SD increase in image area of 238 +/- 104%, whereas feline uroliths (7) underwent significantly less fragmentation (mean image area increase of 78 +/- 97%). The post-SWL increase in fragment image area in 4 of 7 feline uroliths was < 50%, whereas it was > 150% in 6 of 7 canine uroliths.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that feline calcium oxalate uroliths are less susceptible to fragmentation via SWL than canine calcium oxalate uroliths. In some cats, SWL may not be efficacious for fragmentation of calcium oxalate nephroliths or ureteroliths because the high numbers of shock waves required to adequately fragment the uroliths may cause renal injury.

Shockwave lithotripsy: dose-related effects on renal structure, hemodynamics, and tubular function

BACKGROUND AND PURPOSE

Shockwave lithotripsy (SWL) predictably damages renal tissue and transiently reduces function in both kidneys. This study characterized the effects on renal function of a supraclinical dose of shockwaves (SWs) (8000) in porcine kidneys and tested the hypothesis that such excessive treatment would intensify and prolong the resulting renal impairment.

MATERIALS AND METHODS

Pigs aged 6 to 7 weeks were anesthetized and assigned to one of three groups. Groups 1 (N=8) and 2 (N=6) each received 8000 SWs at 24 kV (Dornier HM3) to the lower-pole calix of one kidney. Group 3 (7 pigs) received sham treatment. Renal function was monitored for the first 4 hours after SW treatment in Group 1 and for 24 hours in Group 2. Plasma renin activity was measured in Groups 2 and 3.

RESULTS

The renal lesions produced by 8000 SWs comprised 13.8%+/-1.4% of the renal mass. In the 4-hour protocol, this injury was associated with marked reduction of the glomerular filtration rate (GFR), renal plasma flow (RPF), and urinary sodium excretion in both kidneys, although fractional sodium excretion was reduced only in the shocked kidneys. In the 24-hour protocol, GFR and RPF remained below baseline in shocked kidneys at 24 hours. Evidence of progressive ischemic injury was noted in shocked tissue at 24 hours after SW treatment.

CONCLUSIONS

These findings support the hypothesis that the severity of the renal injury caused by SWL is related to the number of SWs administered and demonstrate the connection in this relation between renal structure and function.

Renal Nerves Mediate Changes in Contralateral Renal Blood Flow after Extracorporeal Shockwave Lithotripsy

Renal blood flow falls in both kidneys following delivery of a clinical dose of shockwaves (SW) (2000 SW, 24 kV, Dornier HM3) to only one kidney. The role of renal nerves in this response was examined in a porcine model of renal denervation. Six-week-old pigs underwent unilateral renal denervation. Nerves along the renal artery of one kidney were identified, sectioned and painted with 10% phenol. Two weeks later the pigs were anesthetized and baseline renal function was determined using inulin and PAH clearances. Animals then had either sham-shockwave lithotripsy (SWL) (group 1), SWL to the innervated kidney (group 2) or SWL to the denervated kidney (group 3). Bilateral renal function was again measured 1 and 4 h after SWL. Both kidneys were then removed for analysis of norepinephrine content to validate the denervation. Renal plasma (RPF) flow was significantly reduced in shocked innervated kidneys (group 2) and shocked denervated kidneys (group 3). RPF was not reduced in the unshocked denervated kidneys of group 2. These observations suggest that renal nerves play a pivotal role in modulating the vascular response of the contralateral unshocked kidney to SWL, but only a partial role, if any, in modulating that response in the shocked kidney.

Renal trauma and the risk of long-term complications in shock wave lithotripsy

Open surgery for removal of upper urinary tract stones has long been associated with a high morbidity and mortality. So when shock wave (SW) lithotripsy (SWL) was introduced in the early 1980s, the climate was right for acceptance of a noninvasive method for stone comminution. The growth in popularity of SWL was extremely rapid, based in part on the perception that it was entirely safe [1]. Now, after a decade of clinical SWL, experience tells us differently. SWL may be very effective at breaking kidney stones, but it can also cause severe renal trauma that can lead to irreversible long-term complications [2, 3].

Protective effect of aminophylline on renal perfusion changes induced by high-energy shockwaves identified by Gd-DTPA-enhanced first-pass perfusion MRI

PURPOSE

The purpose of this study was to evaluate regional renal hemodynamics in a noninvasive manner using gadolinium-DPTA magnetic resonance imaging (MRI) before and after extracorporeal shockwave lithotripsy (SWL). In addition, the renoprotective effect of intravenous aminophylline was evaluated on the perfusion on kidneys undergoing SWL.

PATIENTS AND METHODS

Ten randomly selected patients were evaluated for regional renal blood flow in the cortex and medulla with Gd-DTPA MRI studies within 2 weeks before and 4 hours after SWL. Five of these patients were treated with 500 mg of intravenous aminophylline 45 minutes prior to SWL. Renal hemodynamics were assessed utilizing relative perfusion indices (PI) calculated from signal intensity-v-time curves obtained from regions of interest (ROI). The ROI choice was based on the contrast-enhanced MRI images. Relative PIs of pre-SWL and post-SWL studies were compared in the first group of patients. Relative PIs of the treated kidney were compared with those of the contralateral kidney in the second group of patients, who received aminophylline.

RESULTS

In the group not treated with aminophylline, there was no significant difference in cortical perfusion before SWL (average PI -7+/-3%). However, after lithotripsy, there was a reduction of cortical flow (average PI 31+/-12%) in the treated kidney. In the group treated with aminophylline, renal hemodynamics study after SWL revealed no significant difference in relative perfusion (average PI -8+/-6%). Relative PIs of the medulla were small for all patients, but standard errors were large, indicating a wide range of values.

CONCLUSIONS

This study helps to establish reduced cortical flow after SWL and demonstrates that aminophylline attenuated this response in the kidneys subjected to lithotripsy. It appears that aminophylline administration causes no alteration in medullary blood flow.

Redistribution of renal blood flow after SWL evaluated by Gd-DTPA-enhanced magnetic resonance imaging

Extracorporeal shockwave lithotripsy (SWL) is currently accepted as an effective noninvasive treatment for a wide variety of urinary tract calculi. However, the bioeffects of high-energy shockwaves on renal parenchyma have yet to be fully elucidated. The objective of this study was to measure the acute changes in regional renal hemodynamics associated with SWL utilizing dynamic gadolinium-DTPA-enhanced magnetic resonance imaging (MRI). Seven patients who underwent SWL for renal calculi had an MRI study within 4 hours after the treatment. To assess renal hemodynamics, a bolus of Gd DTPA (0.03 mmol/kg) was administered, and dynamic contrast enhanced images was obtained. Regions of interest (ROI) were defined over the cortex and medulla to obtain signal intensity-v-time curves. The contralateral kidney in each patient was used as the control. The initial slope of the contrast-enhanced signal intensity-v-time curve was used as a measure of the perfusion index (PI). In six patients, perfusion imaging showed a consistent trend of decreased cortical flow (29+/-8%) and a concomitant increase in medullary flow (34+/-14%) in the region of the kidney that was targeted with SWL in six patients (86%). This study shows that renal hemodynamics are modified by SWL. We hypothesize that this change represents a shunting of flow from cortex to medulla in an attempt to prevent ischemia of the medulla.

The pig kidney as an endourologic model: anatomic contribution

We present detailed anatomic findings on collecting system anatomy and renal morphometry in the pig and compare these findings with previous findings in humans. We studied three-dimensional polyester resin corrosion endocasts of the pelviocaliceal system obtained from 100 kidneys (50 pigs). Eighty kidneys were evaluated morphometrically, considering length, cranial pole width, caudal pole width, thickness, and weight. The pig collecting system was classified into two major groups (A and B). Group A (40%) was composed of kidneys in which the mid-zone is drained by calices dependent on the cranial or the caudal caliceal group or both. Group B (60%) kidneys have the mid-zone drained by calices independent of the polar groups. Group B includes two subtypes (B-I and B-II). The pig collecting system showed only angles smaller than 90 degrees between the caudal (lower) infundibulum and the renal pelvis. Renal morphometric measurements revealed the following means: length 11.8 cm, cranial pole width 5.64 cm, caudal pole width 5.35 cm, thickness 2.76 cm, and weight 98 g. As in human kidneys, one may group the pig collecting system into two groups. Nevertheless, in pigs, we did not find a subdivision of Group A. The incidence of collecting systems in Groups A and B and the subtypes of Group B in pigs are different from those in humans. Also different from humans, in pigs, we found only angles smaller than 90 degrees between the caudal (lower) infundibulum and the renal pelvis. Except for the length, the means of the other morphometric measurements of the pig kidney are smaller than those of humans. From an anatomic standpoint, despite the differences pointed out, we conclude that the pig kidney is a good animal model for endourologic research and training.