STONE DISEASE

Fluid absorption during ureterorenoscopy
Cybulski P, Honey JD’A, Pace K
Division of Urology, St. Michael’s Hospital, Toronto, Ontario, Canada
J Endourol. 2004; 18: 739-42

• Background and Purpose: Ureterorenoscopy (URS) is a common minimally invasive diagnostic and therapeutic modality for ureteral and renal pathology. Fluid absorption during routine URS has not been studied prospectively, despite the fact that fluid absorption during other endoscopic urologic procedures can be substantial.
• Patients and Methods: During URS in 15 male and 8 female patients with a mean age of 54 years (range 19 - 81 years), volumetric balance was performed by measuring all fluids instilled into the urinary tract (irrigation fluid and contrast medium) and fluids collected from the urinary tract (irrigation fluid, contrast medium, and urine output) and by estimating urine output from creatinine concentration in the urine and in the fluids collected from the urinary tract. Fluids from the urinary tract were assessed by measuring drainage fluid and the preoperative and postoperative weights of the drapes and bedsheets. Of the procedures, 11 were right-sided and 12 were left-sided. The indications for URS were urolithiasis (N = 18) and diagnosis (hematuria in 2, ureteral or renal filling defect in 2, flank pain and hydronephrosis in 1).
• Results: The mean total operative time was 55 minutes (range 20 - 95 minutes), and the mean URS time was 37 minutes (range 8 - 83 minutes). The mean volume of irrigation fluid used was 2531 mL (range 552 - 5580 mL). The mean estimated urine output during the procedure was 62 mL (range 7 - 201 mL). The mean estimated systemic fluid absorption during URS was 54 mL (range 4 - 137 mL). There were two intraoperative complications (ureteral perforations) but no postoperative complications.
• Conclusions: Routine URS is associated with minimal systemic fluid absorption, even if ureteral perforation occurs. Estimated absorption of as much as 137 mL was seen; however, evaporative losses and unaccounted for losses of fluid likely account for a substantial portion of this fluid discrepancy. This result suggests that irrigation with fluids other than normal saline, such as sterile water, during URS is likely safe.
  
  
• Editorial Comment
  As ureteroscope design and instrumentation have improved, ureteroscopic procedures have become more ambitious; it is increasingly common to treat larger and more complex renal calculi with ureteroscopy, particularly as the limitations of shock wave lithotripsy have become better defined. However, with more complex ureteroscopic cases have come longer operative times and greater potential for complications. Among the potential problems with lengthy ureteroscopic cases are sepsis and systemic absorption of irrigation fluid similar to that seen in TURP syndrome and that reported in some PCNL cases.
  Cybulski and colleagues attempted to quantitate systemic fluid absorption during routine ureteroscopy (both diagnostic and therapeutic) by applying volumetric balance studies of input and outflow fluids, estimating urine output by creatinine concentration measurement of the urine and outflow fluid. Among 18 ureteroscopic cases with a mean ureteroscopy time of 37 minutes, mean systemic fluid absorption was only 54 cc, which correlated strongly with actual ureteroscopy time. Among 2 cases of ureteral perforation, fluid absorption was approximately twice the average. The authors concluded that fluid absorption during routine ureteroscopy is minimal and use of sterile water irrigation fluid may be safe, but deserves further study.
  This is an important study, the first of its kind to quantitate systemic fluid absorption during ureteroscopy and show that the risk of significant fluid absorption and the associated consequences are minimal during routine cases. However, it is important to keep in mind that the average ureteroscopy time in this series was quite short, only 37 minutes. Most of the more complex ureteroscopic procedures performed today (for stones as large as 2 cm or more), are associated with lengthier ureteroscopy times. It is not known if fluid absorption is a linear process, correlating directly with ureteroscopy time, or if the rate of absorption may accelerate with time. Second, in the current series, a ureteral access sheath was used in all cases. It has been shown in both a cadaver study (1) and in a clinical series (2) that use of a ureteral access sheath reduces intrarenal pressure, which in all likelihood will reduce the chance of fluid absorption from the collecting system. Whether fluid absorption is greater in cases performed without an access sheath remains to be seen, but the use of a ureteral access sheath may increase the margin of safety for lengthy ureteroscopic procedure for exactly this reason. Thus, although this important study shows that fluid absorption during routine ureteroscopic cases is minimal, extrapolation to longer more complex cases is not advisable, and the use of water should be discouraged. Having personally reviewed several medicolegal cases of deaths due to use of sterile water irrigation during prolonged ureteroscopic cases, I suggest that the advantage gained in visibility with the use of sterile water irrigation is not worth the risk.

References
1. Auge BK, Pietrow PK, Lallas CD, Raj GV, Santa-Cruz RW, Preminger GM: Ureteral access sheath provides protection against elevated renal pressures during routine flexible ureteroscopic stone manipulation. J Endourol. 2004; 18: 33-6.
2. Rehman J, Monga M, Landman J, Lee DI, Felfela T, Conradie MC, et al.: Characterization of intrapelvic pressure during ureteropyeloscopy with ureteral access sheaths. Urology. 2003; 61: 713-8.

Dr. Margaret S. Pearle
Associate Professor of Urology
University of Texas Southwestern Med Ctr
Dallas, Texas, USA