Defining the Rate of Negative Ureteroscopy in the General Population Treated for Upper Tract Urinary Stone Disease: Beyond the Abstract

When performing ureteroscopy for upper tract urinary stone disease, the urologist may find that the stone has passed or is inaccessible. In this study, we sought to determine the rate at which a “negative ureteroscopy” occurs in the population of California and to determine if certain patient characteristics were associated with receipt of a negative procedure. 

We used the California Office of Statewide Health Planning and Development (OSHPD) database from 2010-2012 to evaluate all non-federal ambulatory surgeries performed in the state of California.  We identified all patients with a diagnosis code for upper tract urinary stone disease who also underwent ureteroscopy.  A negative ureteroscopy was defined as any case coded as a diagnostic ureteroscopy (CPT 52351) with a concomitant diagnosis of upper tract genitourinary stone.  A positive ureteroscopy was defined as those cases with a diagnosis of upper tract genitourinary stone who either had basketing of stone or laser lithotripsy (CPT 52352 or 52353).  In order to accurately define the true rate of initial negative ureteroscopy, we attempted to exclude conditions where a “negative ureteroscopy” might be expected. For example, we excluded patients undergoing a second ureteroscopy within 90 days of a prior procedure as “second look” procedures might be expected to have a higher rate of finding that the stone fragments had passed.

We also excluded persons with diagnosis or procedure codes associated with bladder cancer, upper tract urothelial cancer, ureteral stricture or ureteropelvic junction obstruction.  We further excluded cases where an initial case was a “negative ureteroscopy” but a second ureteroscopy with stone removal was performed within 30 days to avoid including cases where a stent was placed to prepare the ureter for subsequent procedures. We then constructed logistic regression models to evaluate patient factors associated with receipt of a negative ureteroscopy. 

During the years 2010-2012, we included 20,236 primary ureteroscopies performed for urinary stone disease.  The overall rate of negative ureteroscopy was 6.3% (1287 negative ureteroscopies and 19,039 positive ureteroscopies). Female gender was significantly associated with an increased odds of negative ureteroscopy (Odds Ratio [OR] 1.41, 95% confidence interval [CI] 1.25-1.58).  In addition, several insurance types were also significantly associated with increased odds of a negative ureteroscopy: Bluecross/Blueshield or other commercial insurance (OR 1.42, CI 1.19-1.70), Medicare Part A/B (OR 1.61, CI 1.32-1.96), and Medi-Cal (OR 1.58, CI 1.26-1.98).  Conversely patient classified as self-payers had decreased odds of negative ureteroscopy (OR 0.55, CI 0.33-0.91). 

Our findings in summary were:

  1. 6.3% of patients undergoing ureteroscopy for urinary stone disease had a negative ureteroscopy where stone was not removed or treated.
  2. Females were more likely to undergo a negative ureteroscopy than their male counterparts
  3. Self-pay individuals were less likely to undergo a negative ureteroscopy procedure
  4. The negative ureteroscopy rate was increased in patients with several insurance types 
If nearly 1 in 16 patient are undergoing an unnecessary procedure, it begs the question: is a negative ureteroscopy truly a “negative” event?  Should all patients receive a new CT scan just prior to surgery to help prevent unnecessary procedures? Additional imaging could dramatically increase costs  and associated radiation exposures, especially for patients where the lifetime risk of recurrent stone disease is significant. We hypothesize that there is likely an acceptable rate of a negative ureteroscopy event akin to the concept of a negative appendectomy (where an operation for appendicitis is undertaken only to find a normal appendix). Interestingly, implementation of appendicitis guidelines in the Netherlands decreased the negative appendectomy rate from 22.9% to 6.2% over a three year period1!  Perhaps future research and new guidelines could similarly help reduce rates of negative ureteroscopy.

In this study, we identified factors associated with negative ureteroscopy that can be used to help inform efforts to reduce unnecessary surgery. In some cases, patients may prefer to proceed with surgery in order to avoid radiation exposure. Similarly, patients may be driven by the fear of recurrent renal colic, such that a procedure performed even if uncertain of stone presence. It is also interesting to note that self-payers undergo ureteroscopy at a rate nearly half that of insured individuals and there was a significant difference based on different payer sources.  It is possible that perhaps some urologist may bias their decision (whether conscientiously or not) on the payer source.  In any case, this study provides knowledge to both the patient and the urologist in their discussion when deciding how to proceed in the treatment of an upper tract urinary stone.

It remains unclear if the current rate of 6.3% is too high or too low. To date there is only one prior study by Kreshover et al. in which he found a rate of 9.8% in his 256 consecutive procedures in his practice2.  Their study identified smaller stone size as independent predictors of a negative procedure.  Moving forward, stone size may be a criterion we use to help distinguish who receives repeat imaging prior to a procedure in order to prevent unnecessary surgery. In addition, with the advent of low dose CT scans and more sensitive ultrasound technology, when stone passage is in question, it may be prudent to obtain follow up imaging prior to procedure (as the most recent AUA guidelines recommend)3.  

As we strive to minimize "negative" procedures and deliver cost effective care we must remember that imaging is imperfect and urologists must often balance providing timely care, minimizing pain, and limiting the risks/costs of imaging studies. Future studies and guidelines aimed at minimizing costs, optimizing care, and decreasing radiation exposure may help reduce the rates of negative ureteroscopy.

Written by: Remy W Lamberts, Simon L Conti, John T Leppert, and Christopher S Elliott

1. Lahaye MJ, Lambregts DMJ, Mutsaers E, et al: Mandatory imaging cuts costs and reduces the rate of unnecessary surgeries in the diagnostic work-up of patients suspected of having appendicitis. Eur Radiol 2015; 25: 1464–1470.

2. Kreshover JE, Dickstein RJ, Rowe C, et al: Predictors for negative ureteroscopy in the management of upper urinary tract stone disease. Urology 2011; 78: 748–752.

3. Assimos D, Krambeck A, Miller NL, et al: Surgical Management of Stones: American Urological Association/Endourological Society Guideline, PART I. J. Urol. 2016; 196: 1153–1160.

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