The fluid must be transparent, thin, sterile, warm, without debris, and chemically innocuous to the human tissue to be eligible for urinary endoscopy. As mentioned before in this chapter, during a ureteroscopy, fluid flow not only clears away blood, urine, and debris from the optical field but also distends the collecting system, permitting a thorough inspection of endoluminal structures [2].

Physiological saline encompasses all of the above-mentioned requisites, and it prevents electrolyte imbalance (hyponatremia) in the presence of mild to moderate fluid absorption, as in case of occasional pyelolymphatic/pyelovenous backflow during a high-pressure ureteroscopy. However, fluid overload, congestive heart failure, hypothermia, and hemolysis are associated with high fluid absorption seen in long operative times, sustained high intrarenal pressures or in advent of serious urothelial rupture with retroperitoneal extravasation, jeopardizing not only the endoscopic treatment success but also the patient’s well-being [10, 11]. Given the factual risks of clinically relevant adverse events related to the retrograde ureterorenoscopy, identifying adjunctive measures by which intrarenal pressure could be lowered may be protective for the patient.

For this reason, the use of pharmacological agents in the irrigation fluid has been postulated, based on the premise that the renal pelvis and ureter have adrenergic, cholinergic and muscarinic receptors that directly interact with endoluminal pressure [12–15]. It has been demonstrated in an “in vivo” study that the use of catecholamines relaxes the ureteral muscle. This relaxant effect was attributed to activation of beta 2 and 3 receptors in the ureteral segment immersed in a saline solution with catecholamines [13]. In another animal study, the endoluminal norepinephrine injection into the ureter inhibited peristalsis, resulting in a decrease of the smooth muscle tonus that in turn, eliminated the phasic pressure response to perfusion [12]. The most potent relaxing catecholamines were isoproterenol ­followed by epinephrine and norepinephrine subsequently [14]. These studies suggest it is possible to obtain a direct local response on endoluminal pressure by adding one of the above-mentioned ­catecholamines in the irrigation fluid without systemic adverse events [14–16].

Also aiming towards reducing smooth muscle peristalsis and therefore endoluminal ureteral pressure, there have been reports on the injection of calcium channel blockers, such as verapamil and theophylline, into the ureter with promising results. No side effects were cited and “in vivo” peristalsis was inhibited with success [17].

In conclusion, the endoluminal administration of pharmacological agents along with the irrigation fluid may, in a near future, be a viable and safe option for reducing the potential hazards of high intrarenal pressures during a retrograde urinary tract endoscopy.