Cynthia D. Johnson

Renal Functional Effects of Multiple-Tract Percutaneous Access

INTRODUCTION Percutaneous nephrolithotomy (PCNL) can involve establishing more than one access into the urinary collecting system. The present study examined whether multiple percutaneous accesses results in a more severe reduction in renal function than that after single-percutaneous access. METHODS Adult female pigs were anesthetized, and percutaneous access to the left urinary collecting system was achieved by puncturing the lower pole calyx (single-tract access, n = 16) or serially puncturing the lower pole, interpolar region, and upper pole calyces [multiple (three)-tract access, n = 11]. Renal function measurements included glomerular filtration rate and effective renal plasma flow, and were taken immediately before and 1.5 and 4.5 hours after percutaneous access. We also examined glomerular function in a group of adult patients with normal preoperative serum creatinine (Cr) levels (<or=1.4 mg/dL) who underwent either unilateral single-tract PCNL (23 patients) or unilateral multiple (two)-tract PCNL (10 patients). Access tracts were dilated to 30F with a NephroMax balloon dilator system in animal and human patients. RESULTS Single- and multiple-tract percutaneous access procedures in pigs resulted in a similar renal functional response; both glomerular filtration rate and effective renal plasma flow significantly declined by approximately 60% immediately after access and remained depressed throughout the experimental observation period. A retrospective analysis of patients with normal serum Crs (<or=1.4 mg/dL) who underwent single- or multiple-tract PCNL demonstrated that the procedures produced similar and significant increases in serum Cr on postoperative day 1 (0.33 +/- 0.09 [standard error of mean] mg/dL and 0.39 +/- 0.11 mg/dL, respectively) and day 2 (0.33 +/- 0.09 mg/dL and 0.25 +/- 0.09 mg/dL, respectively). CONCLUSIONS Multiple-tract access does not lead to a more severe reduction in renal function than single-tract access; that is, the acute renal hemodynamic response to PCNL appears independent of the number of access tracts.

Evaluation of shock wave lithotripsy injury in the pig using a narrow focal zone lithotriptor.

Whats known on the subject? and What does the study add?

Renal functional effects of simultaneous bilateral single‐tract percutaneous access in pigs

To present our findings of simultaneous bilateral percutaneous nephrolithotomy (sbPCNL) on bilateral renal haemodynamic and excretory function in an in vivo pig model, as despite sbPCNL being a treatment strategy for patients with bilateral renal stones, the functional response of both kidneys to such a procedure is unknown.

Using 300 Pretreatment Shock Waves in a Voltage Ramping Protocol Can Significantly Reduce Tissue Injury During Extracorporeal Shock Wave Lithotripsy

PURPOSE Pretreating a pig kidney with 500 low-energy shock waves (SWs) before delivering a clinical dose of SWs (2000 SWs, 24 kV, 120 SWs/min) has been shown to significantly reduce the size of the hemorrhagic lesion produced in that treated kidney, compared with a protocol without pretreatment. However, since the time available for patient care is limited, we wanted to determine if fewer pretreatment SWs could be used in this protocol. As such, we tested if pretreating with 300 SWs can initiate the same reduction in renal lesion size as has been observed with 500 SWs. MATERIALS AND METHODS Fifteen female farm pigs were placed in an unmodified Dornier HM-3 lithotripter, where the left kidney of each animal was targeted for lithotripsy treatment. The kidneys received 300 SWs at 12 kV (120 SWs/min) followed immediately by 2000 SWs at 24 kV (120 SWs/min) focused on the lower pole. These kidneys were compared with kidneys given a clinical dose of SWs with 500 SW pretreatment, and without pretreatment. Renal function was measured both before and after SW exposure, and lesion size analysis was performed to assess the volume of hemorrhagic tissue injury (% functional renal volume, FRV) created by the 300 SW pretreatment regimen. RESULTS Glomerular filtration rate fell significantly in the 300 SW pretreatment group by 1 hour after lithotripsy treatment. For most animals, low-energy pretreatment with 300 SWs significantly reduced the size of the hemorrhagic injury (to 0.8% ± 0.4%FRV) compared with the injury produced by a typical clinical dose of SWs. CONCLUSIONS The results suggest that 300 pretreatment SWs in a voltage ramping treatment regimen can initiate a protective response in the majority of treated kidneys and significantly reduce tissue injury in our model of lithotripsy injury.

Shock Wave Lithotripsy Does Not Impair Renal Function in a Swine Model of Metabolic Syndrome

PURPOSE To determine whether shock wave lithotripsy (SWL) may be a risk factor for renal functional impairment in a swine model of metabolic syndrome (MetS). MATERIALS AND METHODS Nine-month-old female Ossabaw pigs were fed an excess calorie atherogenic diet to induce MetS. At 15 months of age, the MetS pigs were treated with 2000 SWs or an overtreatment dose of 4000 SWs targeted at the upper pole calyx of the left kidney (24 kV at 120 SWs/min using the unmodified Dornier HM3 lithotripter; n=5-6 per treatment group). Serum creatinine (Cr) and blood urea nitrogen (BUN) levels were measured in conscious pigs before and ∼60 days after SWL to provide a qualitative assessment of how well both kidneys were filtering (glomerular filtration rate [GFR]). Bilateral renal function was assessed at ∼65 days post-SWL in anesthetized pigs with GFR and effective renal plasma flow (ERPF) quantified by the renal clearance of inulin and para-amino hippurate, respectively. RESULTS Cr and BUN values were within normal limits before SWL and remained unchanged after lithotripsy in both the 2000 SW- and 4000 SW-treated pigs. GFR and ERPF of kidneys treated with SWL at either SW dose were similar to the contralateral nontreated kidney. Chronic histological changes in the SW-treated pole of the kidney included interstitial fibrosis, sclerotic glomeruli, and dilated and atrophic tubules. CONCLUSIONS Our results are consistent with the view that a single SWL session does not result in renal impairment, even in the presence of MetS.

Percutaneous Renal Access: Surgical Factors Involved in the Acute Reduction of Renal Function.

INTRODUCTION AND OBJECTIVE Studies in patients and experimental animals have shown that percutaneous nephrolithotomy (PCNL) can acutely impair glomerular filtration and renal perfusion, but the factors contributing to this decline in renal function are unknown. The present study assessed the contribution of needle puncture of the kidney vs dilation of the needle tract to the acute decline in renal hemodynamic and tubular transport function associated with PCNL surgery. MATERIALS AND METHODS Acute experiments were performed in three groups of anesthetized adult farm pigs: sham-percutaneous access (PERC), that is, no surgical procedure (n = 7); a single-needle stick to access the renal collecting system (n = 8); expansion of the single-needle access tract with a 30F NephroMax balloon dilator and insertion of a nephrostomy sheath (n = 10). The glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and renal extraction of para-amino hippurate (EPAH, estimates tubular organic anion transporter [OAT] activity) were assessed before and 1 to 4.5 hours after sham-PERC or PERC surgical procedures. RESULTS Overall, GFR responses were similar in all three groups. Sham-treated PERC pigs showed no significant change in ERPF over the experimental observation period, whereas a single-needle stick to access the renal collecting system resulted in renal vasoconstriction (∼30% reduction in ERPF, p < 0.05). Dilation of the single-needle access tract to create the nephrostomy did not lead to a further decline in ERPF. PERC surgical procedure-mediated renal vasoconstriction was most evident at the 1-hour posttreatment time point. A reduction in EPAH was only observed in pig kidneys with a nephrostomy. CONCLUSIONS Needle puncture of the kidney for percutaneous access to the renal collecting system is the major driving force for the renal vasoconstriction observed after PCNL surgery, whereas creation of the nephrostomy appears to be largely responsible for decreasing tubular OAT activity.

Percutaneous Access: Acute Effects on Renal Function and Structure in a Porcine Model

Percutaneous nephrolithotomy (PCNL) involves gaining access into the urinary collecting system to remove kidney stones. Animal studies demonstrated that a reduction in renal filtration and perfusion in both kidneys, and a decline in tubular organic anion transport in the treated kidney characterizes the acute (hours) functional response to unilateral percutaneous access. The acute morphologic and histological changes in the treated kidney were consistent with blunt trauma and ischemia. Only tubular organic anion transport remained depressed during the late (3‐day) response to the access procedure. Human studies revealed an acute decline in glomerular function and bilateral renal vasoconstriction following unilateral PCNL. Therefore, percutaneous access is not a benign procedure, but is associated with acute functional and structural derangements.

Preliminary Report on Stone Breakage and Lesion Size Produced by a New Extracorporeal Electrohydraulic (Sparker Array) Discharge Device

OBJECTIVE To determine if an innovative extracorporeal electrohydraulic shock wave (SW) device (sparker array [SPA]) can effectively fracture artificial stones in vitro and in vivo, and if SPA treatment produces a renal lesion in our pig model of lithotripsy injury. Results of these experiments will be used to help evaluate the suitability of this device as a clinical lithotripter. MATERIALS AND METHODS Ultracal-30 artificial stones were placed in a holder at the focus of the SPA and treated with 600 SWs (21.6 kV, 60 shocks/min). Stone fragments were collected, dried, and weighed to determine stone breakage. In vivo stone breakage entailed implanting stones into pigs. These stones were treated with 600 or 1200 SWs and the fragments were collected for analysis. Lesion analysis consisted of treating the left kidney of pigs with 1200 or 2400 SWs and quantitating the hemorrhagic lesion. RESULTS In vitro, 71% ± 2% of each artificial stone was fractured to <2 mm in size. In vivo stone breakage averaged 63%. Renal injury analysis revealed that only 1 of 7 kidneys showed evidence of hemorrhagic injury in the treated area. CONCLUSION The SPA consistently comminuted artificial stones demonstrating its ability to fracture stones like other lithotripters. Also, the SPA caused little to no renal injury at the settings used in this study. These findings suggest further research is warranted to determine the potential of this device as a clinical lithotripter.

Exploring the limits of treatment used to invoke protection from extracorporeal shock wave lithotripsy induced injury

Previous studies with our juvenile pig model have shown that a clinical dose of 2000 shock waves (SWs) (Dornier HM-3, 24 kV, 120 SWs/min) produces a lesion ~3–5% of the functional renal volume (FRV) of the SW-treated kidney. This injury was significantly reduced (to ~0.4% FRV) when a priming dose of 500 low-energy SWs immediately preceded this clinical dose, but not when using a priming dose of 100 SWs [BJU Int. 110, E1041 (2012)]. The present study examined whether using only 300 priming dose SWs would initiate protection against injury. METHODS: Juvenile pigs were treated with 300 SW’s (12 kV) delivered to a lower pole calyx using a HM-3 lithotripter. After a pause of 10 s, 2000 SWs (24 kV) were delivered to that same kidney. The kidneys were then perfusion-fixed and processed to quantitate the size of the parenchymal lesion. RESULTS: Pigs (n = 9) treated using a protocol with 300 low-energy priming dose SWs had a lesion measuring 0.84±0.43% FRV (mean ± SE). This lesion was smaller than that seen with a...

Shock wave lithotripsy can alter urinary acid‐base pH regulation.

The renal papilla is particularly susceptible to injury by shock waves (SWs). Since the papilla is vital for urinary pH regulation, we hypothesized that shock wave lithotripsy (SWL)‐induced damage of papillae will alter the pH of the urine. Experiments were conducted in four female adult Gottingen minipigs. The HM3 lithotripter delivered a total of 8000 SWs (24 kV, 120 SWs/min) among all papillae of one kidney, while the untreated, opposite kidney was used as control. The pigs were allowed to recover and 5 weeks later they were anesthetized. Serial urine collections were obtained from the SW‐treated and untreated kidney. Urine was collected under mineral oil and immediately tested for its pH. Both kidneys were then perfusion fixed for histological analysis. Urinary pH was 0.17 units greater (P<0.05) in the SW‐treated kidney compared to the untreated kidney. Histology showed scarring in all regions of the SW‐treated kidney, with thick ascending limbs and collecting ducts having grossly abnormal morphologie...