AUA QI Summit 2017: Dose Optimization in Stone Evaluation: DOSE

Linthicum, Maryland ( Dr. Christopher Moore, an emergency medicine physician from Yale University, provided an important presentation at the AUA Quality Improvement Summit discussing imaging dose optimization in urinary stone evaluation. Urinary stone disease is common, affecting 1 in 11 people with an increasing incidence in the US and worldwide. Furthermore, more than 50% of patients will recur within 5 years. Stone disease is also a burden on the health care system, with more than 1 million stone diagnoses per year in the emergency department, and more than 2 million visits per year for renal colic at an annual cost of $10 billion. Since a 1996 report stated that unenhanced helical CT scan was the imaging modality of choice for examining patients with acute flank pain, the national trends in use of CT in the emergency department have skyrocketed.

In 2014, Dr. Moore and his research collaborators were involved with deriving and validating the STONE score – a clinical prediction rule for predicting uncomplicated ureteral stones [1]. The key components of the score (and score value) are as follows:

  • Gender: Male + 2
  • Timing of flank pain: <6 hr + 3; 6-24 hr +1
  • Race: Non-black + 3
  • Nausea: Alone + 1; With vomiting + 2
  • Hematuria: Any blood on urinalysis + 3

A STONE score of 0-5 (low) had a probability of 8-10% for having a ureteral stone, a score of 6-9 (moderate) a probability of ~50%, and a score of 10-13 (high) a probability of ~90% [1]. Dr. Moore’s group then developed an imaging algorithm based off of these results:

  • Low STONE score – ultrasound: without hydronephrosis, low likelihood of stone; with hydronephrosis, moderate likelihood of stone, consider low dose CT
  • Moderate STONE score – ultrasound: without hydronephrosis, moderate likelihood of stone, consider low dose CT; with hydronephrosis, ureteral stone very likely and could consider trial of passage without further imaging (low dose CT at physician discretion)
  • High STONE score - ureteral stone very likely and could consider trial of passage without further imaging (low dose CT at physician discretion)

Population-based studies assessing dose variation for renal colic CTs have demonstrated considerable variability and unfortunately only 2% of CT scans obtained were “low-dose” (<3 mSv) as of 2014. The D.ose O.ptimiation in S.tone E.valuation (DOSE) study is a 5-year AHRQ funded study working through the American College of Radiology (ACR) Dose-Index Registry and is a stratified delayed randomization trial at the institutional level. Certainly, we await the results of this study in an attempt to improve on dosing for renal colic CT scans.

The emergency perspective to acute renal colic is multifactorial. Emergency medicine personnel are (i) more concerned with time and with “bad things” according to Dr. Moore, as well as (ii) less concerned with the ultimate course as long as the patient can be discharged safely, (iii) fighting the cultural norm that “all first-time renal colic needs a CT scan, and (iv) would rather not deal with incidental findings. Several studies have estimated the prevalence of incidental findings at 12.7%, with 1 in 8 renal colic CT scans having an incidental finding with recommended follow-up imaging. Astutely stated for the detection of incidental findings is the acronym VOMIT: Victims Of Modern Imaging Technology...

Dr. Moore concluded that in the near future there will be the DOSE study findings, in addition to a collaborative Best Practice Guideline for Imaging consisting of representatives from ACEP, ACR, and the AUA.

Speaker(s): Christopher Moore, Yale University, New Haven, CT, USA

Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Twitter: @zklaassen_md, at the AUA Quality Improvement Summit - October 21, 2017- Linthicum, Maryland