ENDOUROLOGY

Routine postoperative imaging is important after ureteroscopic stone manipulation
Weizer AZ, Auge BK, Silverstein AD, Delvecchio FC, Brizuela RM, Dahm P, Pietrow PK, Lewis BR, Albala DM, Preminger GM
From the Comprehensive Kidney Stone Center, Division of Urology, Department of Surgery, Duke University Medical Center, Durham, North Carolina
J Urol. 2002; 168:46-50

• Purpose: Improved fiber optics and advanced intracorporeal lithotripsy devices have significantly decreased the incidence of complications during ureteroscopic procedures. Despite recent reports suggesting that radiographic imaging may not be necessary in all individuals after routine ureteroscopy silent obstruction may develop in some, ultimately resulting in renal damage. We determined the incidence of postoperative silent obstruction at our institution and assessed the need for routine functional radiographic studies after ureteroscopy.
• Materials and Methods: We retrospectively reviewed the charts of 320 patients who underwent a total of 459 ureteroscopic procedures for renal or ureteral calculi in a 3-year period. Complete followup with imaging was available for 241 patients (75%). Average patient age was 47.2 years. The variables of interest reviewed included preoperative pain, preoperative obstruction, targeted calculus site, stone-free rate, postoperative pain and postoperative obstruction. Mean followup was 5.4 months (range 2 to 43).
• Results: A total of 241 patients with complete followup were identified in this analysis. Preoperative pain was present in 202 patients (84%) and 168 (70%) had preoperative obstruction. Overall targeted calculus clearance was successful in 73% of the patients and an additional 15.8% had residual fragments less than 4 mm. The renal, proximal or mid and distal ureteral stone-free rate was 32.1%, 81.9% and 90.5%, while in an additional 46.4%, 6.3% and 6.7% of cases, respectively, residual fragments were less than 4 mm. Of the 241 patients 30 (12.3%) had obstruction postoperatively due to residual stone in 25 (83.3%), stricture in 3 (10%), edema of the ureteral orifice in 1 (3.3%) and a retained encrusted stent in 1 (3.3%). Postoperatively obstruction correlated with postoperative pain in 23 of the 30 patients (76.7%). Pain was present postoperatively in 30 of the 211 patients (14%) without evidence of ureteral obstruction postoperatively. However, silent obstruction developed in 7 patients (23.3%) or 2.9% of the total cohort. All 7 patients underwent secondary ureteroscopy to alleviate obstruction. A single patient ultimately received chronic hemodialysis for renal failure, 1 was lost to followup and in 5 there was documented successful resolution of the cause of obstruction.
• Conclusions: Our analysis suggests that silent obstruction remains a potentially significant complication after stone management. Relying on postoperative pain to determine the necessity of postoperative imaging places patients at risk for progressive renal failure due to unrecognized obstruction. Therefore, we recommend that imaging of the collecting system should be performed by excretory urography, spiral computerized tomography or ultrasound within 3 months after routine ureteroscopic stone treatment to avoid the potential complications of unrecognized ureteral obstruction.
  
  
• Editorial Comment
  This article raises some disturbing issues for those of us who may have been lulled into security by the usual high success and lower complication rates of modern ureteroscopy. Among 241 ureteroscopic patients with complete follow-up, 30 were documented to have postoperative obstruction, usually due to residual calculi. Of these 30, there was no pain in 7 (23%), representing 2.9% of the total patient population. Earlier studies had suggested that in patients without postoperative pain, imaging to detect obstruction was not necessary. The authors of this paper contend that although the incidence of silent obstruction (obstruction without postoperative pain) is low, that the clinical significance of missing obstruction in these patients is considerable and that therefore routine imaging of all patients following ureteroscopy with a modality that would detect potential obstruction (IVP, CT scan, renal scan, or ultrasonography) is indicated. Of the 7 patients with silent obstruction, 2 did not have obstruction pre-operatively. Moreover, stone location or size did not consistently suggest patients at increased risk for so obstruction. Of note, however, the obstruction was due to calculi in 6 of 7 patients. The article did not provide data as to how many of these calculi were visible on plane radiography. I would like to think that most of these patients would have been detected to have residual calculi with plain radiography; such patients whom would be followed up with additional imaging that would have detected the obstruction. I would also like to think that very few patients without adverse risk factors (significant preoperative obstruction, postoperative pain, difficult or multiple stone procedures, residual calculi) would suffer silent obstruction. Nonetheless, the results of this study suggest that perhaps a more liberal application of postoperative imaging for obstruction should be applied to patients following ureteroscopy.

Dr. J. Stuart Wolf Jr.
Associate Professor of Urology
University of Michigan
Ann Arbor, Michigan, USA