Pathophysiological aspects of ureterorenoscopic management of upper urinary tract calculi.

PURPOSE OF REVIEW: Indications for ureterorenoscopy are expanding without hard scientific evidence to support its efficacy. Therefore, it is extremely important to focus on potential harmful effects of the procedure itself. This review explores how physiology of the upper urinary tract reacts to ureterorenoscopy, potentially translating into harmful effects, and how such pathophysiological processes may be minimized. RECENT FINDINGS: Complications to ureterorenoscopy and postoperative pain seem to be related to intrarenal pressure and/or access. Mean intrarenal pressures in the range of 60-100 mmHg during ureterorenoscopy without access sheaths have been measured, thus by far exceeding the threshold for intrarenal backflow, potentially resulting in septic complications. Intrarenal pressure may be reduced by use of ureteral access sheaths, which, however, may cause ureteral damage due to the limited size of the ureter and strain-induced ureteral contractions (peristalsis). Different receptor types modulate this peristaltic activity. ß-receptor agonists have been investigated in animal and human trials for the purpose of relaxing the ureter. In randomized, placebo-controlled trials in pigs and humans, usage of the ß-receptor agonist isoproterenol in the irrigation fluid has shown a potential for reducing both intrarenal pressure and ureteral tone during ureterorenoscopy. SUMMARY: Upper urinary tract physiology has unique features that may be pushed into pathophysiological processes by the unique elements of ureterorenoscopy: access and irrigation. Pharmacological ureteral relaxation during ureterorenoscopy deserves further attention with regard to reducing complications and postoperative pain.

Endoluminal isoproterenol reduces renal pelvic pressure during semirigid ureterorenoscopy: a porcine model.

OBJECTIVE: To investigate the effects on the pressure-flow relation of renal pelvic pressure during semirigid ureterorenoscopy and endoluminal perfusion of isoproterenol (ISO) 0.1 microg/mL, with emphasis on local effects and cardiovascular side-effects, as topically administered ISO effectively and dose-dependently causes relaxation of the upper urinary tract in pigs with no concomitant cardiovascular side-effects. MATERIALS AND METHODS: In anaesthetized female pigs (60 kg), 16 macroscopically normal upper urinary tract systems were subjected to ureterorenoscopy. Via a subcostal incision a 6-F catheter was placed in the renal pelvis for pressure measurements, and a semirigid ureteroscope (7.8 F) was inserted retrogradely in the renal pelvis, through which the pelvis was perfused. The blood pressure and heart rate were recorded. The increase in renal pelvic pressure was examined with increasing flow rates (0, 4, 8, 12, 16, 25 and 33 mL/min) with saline alone or saline + ISO 0.1 microg/mL. Perfusion was initiated on the left side, with randomization for adding ISO or not. Thereafter perfusion was done on the right side as a control in each pig. The surgeons were unaware of whether ISO was added or not. RESULTS: The mean (sd) baseline pelvic pressures in the saline and ISO group were 28 (7.1) and 25 (9.8) mmHg, respectively, with no significant difference (P = 0.079). Endoluminal perfusion with ISO significantly inhibited the pelvic pressure increase to perfusion at all perfusion rates. The pressure-flow relation was linear; the maximum relaxation (27%) was obtained at 4 mL/min, from 52 to 38 mmHg during saline alone and ISO 0.1 microg/mL perfusion, respectively. The mean blood pressure did not change significantly (P = 0.330). The mean (sd) heart rate in the saline and ISO group were 109 (4.5) and 97 (2.1) beats/min, respectively (P < 0.001), i.e. a markedly greater rate in the saline than in the ISO group. CONCLUSION: The pressure-flow relation during semirigid ureterorenoscopy was linear. ISO 0.1 microg/mL in saline significantly reduced the pressure-flow relation during semirigid ureterorenoscopy in this porcine model. ISO might be a potential additive to the irrigation fluid during upper urinary tract endoscopic procedures, minimizing pressure increases due to irrigation and manipulation.

[Retrograde intrarenal stone surgery--a minimally invasive method for treatment of minor kidney stones]. / Retrograd intrarenal stenkirurgi--en minimalinvasiv metode til behandling af nyresten.

Retrograde intrarenal stone surgery (RIRS) is a safe and effective minimally invasive method for the treatment of minor (< 1.5 cm) kidney stones. This modality is the preferred treatment for minor ESWL-resistant kidney stones where resistance is due e.g. to anatomical abnormalities or stones of specific composition. The use of ureteric tone-modulating drugs in the irrigation fluid during the endoscopic procedure may prove to increase efficacy and safety of RIRS in the future.

Irrigation with isoproterenol during ureterorenoscopy causes no systemic side-effects.

OBJECTIVE: Ureterorenoscopy causes complications that may be related to high intrarenal pressures generated during irrigation. Endoluminal isoproterenol administration has been shown to reduce pelvic pressure in pigs. The objective of this study was to investigate possible systemic side-effects of isoproterenol irrigation during ureterorenoscopy in humans. MATERIAL AND METHODS: Seven patients undergoing ureterorenoscopy due to renal stone disease were included. A 5-Fr catheter was retrogradely placed in the renal pelvis for pressure measurements. Prior to irrigation with isoproterenol (0.1 microg/ml), ureterorenoscopy was performed with saline irrigation. Renal pelvic pressure, blood pressure and heart rate were measured before and after isoproterenol irrigation. Venous blood was drawn for isoproterenol measurements. RESULTS: Endoluminal isoproterenol irrigation produced no changes in mean heart rate (HR) or mean arterial pressure (MAP). MAP (+/- SEM) was 56 (2.7) mmHg during saline irrigation and 58 (+/- 2.4) mmHg during isoproterenol irrigation. HR was 60 (+/- 4) beats/min before and 61 (+/- 4) beats/min during isoproterenol irrigation. Neither the difference in MAP = 0.10) nor the difference in HR (p = 0.23) were significant. Pelvic pressure was significantly lower during isoproterenol irrigation [19 (+/- 3) mmHg] compared to saline irrigation [35 (+/- 2.6) mmHg] (p = 0.0006). Pelvic pressure reached very high levels (> 300 mmHg), especially during injection of contrast medium. CONCLUSION: Endoluminal isoproterenol irrigation during ureterorenoscopy causes no cardiovascular side-effects and the drug may reduce renal pelvic pressure.

Pharmacological effect on pyeloureteric dynamics with a clinical perspective: a review of the literature.

We searched to review experimental and clinical trials concerning the capabilities of impacting on the ureteric and pelvic activity by means of pharmacological stimulation. Ureteropyeloscopy may cause high renal pelvic pressure. The normal pressure is in the range of 5-15 mmHg whereas pressure of 410 mmHg has been measured during endoscopy. The threshold pressure for intrarenal reflux is about 35 mmHg. Studies in animals have revealed that high renal pelvic pressures may cause permanent damage to the renal parenchyma. Furthermore, it has been demonstrated that elevated pressures may entail an increased risk of several complications related to endourological procedures including bleeding, perforation and infection. In other words, means by which intrarenal pressure could be lowered during endourological procedures might be beneficial with respect to clinical outcomes. In vitro experiments support the existence of different receptors in the ureter and renal pelvis. The ureteric and pelvic responses to the corresponding neurotransmitters have been determined. It seems that alpha-adrenergic and cholinergic agents are stimulating whereas beta-adrenergic agents inhibit ureteric activity. The effect may depend on the mode of administration. Drugs exerting advantageous effects in the pyeloureter may cause undesirable systemic side effects when administered intravenously. In animal studies, renal pelvic pressure can be significantly lowered by topical administration of beta-adrenergic agonists without systemic side effects. In vivo human studies are necessary to clarify the exact dose-response relationship and the degree of urothelial absorption of a drug before clinical use may be adopted.