Ultrasonic lithotripsy and soft tissue

Clearance of Metal Particles After Percutaneous Nephrolithotomy with Trilogy Lithotripter

Purpose: To evaluate the clearance of metal particles produced and released in the pelvicaliceal system (PCS) during percutaneous nephrolithotomy (PCNL) with the use of the Swiss Lithoclast^® Trilogy dual-energy (EMS Urology, Nyon, Switzerland) lithotripter. Methods: An experimental in vivo study and a clinical investigation of case series were conducted. An in vivo porcine model with two pigs for lithotripsy (after inserting artificial stones into the collecting system) and two pigs for submucosal injection of metal particles (provided by the manufacturer of Trilogy) was conducted. Porcine kidney histology analysis for metal leftovers was conducted immediately or 2 weeks after the surgery. A prospective observational study design included 10 consecutive patients treated with conventional 30F PCNL or with 22F mini-PCNL technique. Only the patients with the confirmed metal particles in the PCS during the initial PCNL and the need for additional retrograde intrarenal surgery over a period of 2-4 weeks were selected. The presence of metal particles was evaluated during the second endoscopic surgery. Results: The generated metal particles during PCNL and the submucosally injected particles were not found macroscopically 2 weeks postoperatively in porcine models. No pathologic changes such as foreign body granuloma or inflammation were found. Similarly, no metal particles were observed during the second look endoscopy (n = 10). Conclusion: Metal particles observed endoscopically using the Trilogy lithotripter are cleared with no pathologic evidence of tissue damage from the metal particles 2 weeks after the procedure. Thus, the intraoperative release of any particle by the Trilogy lithotripter should not raise any safety concerns.

Contrast-enhanced Ultrasound in Obstetrics and Gynecology

Ultrasonography is a well-established imaging modality for evaluation of gynecologic tumors. In recent years, more sophisticated technologies like the use of intravascular contrast agents led to an improvement in the ability of the practitioner to differentiate benign from malignant masses. When we consider the safety of contrast-enhanced ultrasonography in obstetrics and gynecology, we must discuss about the effect of ultrasound contrast media on embryo and fetus. The use of ultrasound contrast media in pregnant women always concerns in the obstetricians because of the principle of not exposing a fetus to any drug. Therefore, the literature was reviewed for information about those safety and efficacy because of the uncertainty about the use of contrast media during pregnancy. Based on the limited information available, mutagenic and teratogenic effects have not been described after administration of ultrasound contrast media. No effect on the fetus has been seen after contrast media. The small potential risk associated with the nonthermal bioeffects via acoustic cavitation may be considered to prohibit the use in first trimester pregnant women. In previous studies including human trials, no evidence of adverse effect was reported. Contrast-enhanced ultrasonography could prove a useful adjunct in multiple gestations and in evaluation of uteroplacental circulation. It appears to be very promising potential in obstetrics.

The effects of a soft tissue mimicking medium and increased power settings on the location and magnitude of lithotripter peak positive pressure

In vitro experiments showed that a tissue mimicking medium alters the peak positive pressure (p+), focal zone properties and frequency content of shockwaves compared with their behavior in water. The reduction in (p+) ranged from 5% at 10 kV. to 19% at 18.1 kV., when measured at the geometric focus with the tissue mimicking medium present. As power settings were increased, the relative gain in pressure was damped by attenuation. A 2 mm. shift in the acoustic focus was seen both axially and laterally with the tissue mimicking medium. While the former is probably not significant, the latter may be clinically significant given the narrow lateral beam width at the acoustic focus. These attenuation experiments suggest that clinical targeting through tissue may not be as precise or result in as high peak pressures as the clinician expects. Especially at high power settings, the depth of tissue traversed should be minimized to limit attenuation effects.

Hepatic cavitation. A marker of transient hepatocellular injury during biliary lithotripsy

Sonographically visible microbubbles attributable to cavitation effects have been observed in bile (within the gallbladder), in hepatic vessels, and within the liver of patients undergoing biliary lithotripsy. Cavitation effects are believed to contribute to stone fragmentation and possibly tissue injury during lithotripsy. To study the latter, the relationship between intraparenchymal hepatic cavitation and serum transaminase activity and clinical follow-up was analyzed in 81 patients undergoing 164 lithotripsy treatments. Seventy-one treatments (43%) resulted in sonographically evident microbubbles in the liver parenchyma during lithotripsy. A temporary, yet statistically significant (P < 0.01) rise in SGOT and SGPT was observed within 2 hr of completion of lithotripsy compared to those patients without hepatic microbubbles. All but one patient had a return to pretreatment baseline levels of SGOT and SGPT by two weeks after lithotripsy. In this patient, persistent elevation of transaminases was attributed to the delayed passage of fragments and not to any sequelae from hepatic cavitation effects. Ultrasound immediately after, two weeks after, and 3-12 months after lithotripsy showed no hepatic structural abnormalities. Ursodiol administration at the time of treatment did not predispose to hepatic cavitation or elevation of transaminase. Detection of hepatic microbubbles during lithotripsy is a marker of hepatocellular injury. Their correlation with transaminase elevation refutes the contention that transaminasemia results solely from fragment passage after lithotripsy. Although not associated with recognizable structural damage or long-term sequelae, cavitation effects and transaminasemia reiterate that shockwaves are not entirely benign as they traverse parenchymal organs.

A safe new procedure for high-risk patients with symptomatic gallstones

Cholecystectomy is associated with an appreciable mortality rate in elderly high-risk patients. Patients aged over 60 years with symptomatic gallstones, at high operative risk, underwent cholecystotomy under local anaesthesia through a 3-cm incision. Stones were removed and clearance was demonstrated endoscopically and by tube cholecystography. Catheter drainage was continued for 7 days until a further cholecystogram confirmed clearance. The procedure was attempted in 26 patients with concomitant cardiovascular, respiratory or malignant disease. Successful removal of all gallbladder stones was possible in 24 patients. Four patients had common bile duct stones demonstrated on cholecystography, all of which were successfully treated by endoscopic sphincterotomy. All patients are symptom-free at a mean follow-up of 36 weeks with no recurrent stones on ultrasonography.

Acoustic cavitation generated by an extracorporeal shockwave lithotripter

Evidence is presented of acoustic cavitation generated by a Dornier extracorporeal shockwave lithotripter. Using x-ray film, thin aluminum sheets, and relatively thick metal plates as targets, evidence of liquid jet impacts associated with cavitation bubble collapse was observed. The jet impact was violent enough to puncture thin foils and deform metal plates. Furthermore, numerous jet impacts were generated over a volume of greater than 200 cm3. It is likely that such violent cavitation will also occur in tissue, and observed biological effects (e.g. renal calculus disintegration and tissue trauma) may be related to cavitation damage.

Late sequelae of the management of ureteral calculi with the ureterorenoscope

We examined 42 patients 19 to 20 months after ureteral calculi had been removed with the ureterorenoscope. All 42 patients were asymptomatic and showed no evidence of an increased rate of urinary tract infection or hypertension. An excretory urogram in 38 patients demonstrated no abnormality related to the procedure, in particular no ureteral stenosis and renal scarring. Renal sonography in the remaining 4 patients likewise was normal. Reflux cystography revealed low grade (sterile) vesicoureteral reflux in 2 patients. In view of a 92 per cent success rate in 236 renoureteral units, with serious complications in only 2 per cent, the technique can be considered safe and effective.

Percutaneous coagulum nephrolithotripsy: a new approach

Intrarenal scatter of stone fragments during percutaneous nephrolithotripsy is a complication which may predispose to post-operative pain and further stone formation. The use of a coagulum to prevent such a complication has proved difficult when introduced percutaneously. This experimental study describes a new gelatine (Lithogel) which is introduced through the nephroscope to coat the renal calculus; it allows easy disintegration of the calculus within the gel, is safe to use and effectively prevents the scatter of fragments into inaccessible calices.