Renal Pelvis Pressures During Ureteroscopy Predict Pyelovenous Absorption in a Porcine Model
Jeffrey K. Twum-Ampofo, MD1, Jennifer Saunders, MS2, Marle Franco, BS3, Brian H. Eisner, MD1.
1Massachusetts General Hospital, Boston, MA, 2Boston Scientific, Boston, MA, 3Boston Scientific, Marlborough, MA.
BACKGROUND: Renal pelvis pressures and pyelovenous backflow during ureteroscopy are hypothesized to play a role in the development of infection after ureterorenoscopy. However, there are few studies in the literature which investigate this phenomon and the relationship between renal pelvis pressure, operative time, and pyelovenous backflow is poorly understood. Herein we present a pilot study of ureteroscopy in a swine model designed to evaluate these relationships.
METHODS: In anesthetized pigs (n=9; female; ~60 kg each), ureteroscopy was performed as follows: cystoscopy was performed to position a 0.018” pressure sensor guidewire (Comet™, Boston Scientific, Marlborough, MA) and standard guidewire. A flexible ureteroscope was then introduced into the renal pelvis and the position of the ureteroscope and the pressure sensor wire were confirmed. Infusion of irrigation fluid (5% ethanol in saline) at target renal pelvic pressures (37-150 mmHg) was maintained for 60 minutes using a pressure bag and instantaneous feedback from the pressure-sensing guidewire. Venous blood sampling was performed every 10 minutes. Each trial started with blood EtOH of 0 mg/dL. Volume of irrigant absorbed was determined with established equations utilizing animal blood EtOH, weight, and irrigation concentration.
RESULTS: Fourteen (14) pig kidneys were used during the study. The average irrigation volume absorbed after 60 minutes of irrigation were 4.9, 7.9, 24.9, and 72.5 mL of fluid at renal pelvis pressures of 37, 55, 75, and 150 mm Hg, respectively (P = 0.07) . At renal pelvis pressures of 55 mm Hg and above, pyelovenous backflow occurred as early as 20 minutes. At renal pelvis pressures of 37 mm Hg, pyelovenous backflow was not measured until at least 40 minutes of procedure time. Increasing renal pelvis pressures were associated with increases in fluid absorption for all pressures tested [Figure 1].
CONCLUSIONS:
In this study of a swine model of ureteroscopy, increasing renal pelvis pressures during ureteroscopy were associated with increases in fluid absorption as well as more rapid fluid absorption. This model may be used in the future to better understand the relationship between renal pelvis pressure and pyelovenous backflow during ureteroscopy. 
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