Other imaging options for suspected stone disease include ultrasonography, plain abdominal films, low-dose CT scans, a combination of modalities, or no imaging. Certainly, based on data presented today by Dr. Rebecca Smith-Bindman and reported in the New England Journal of Medicine , there is a push in the US for ultrasonography as the initial imaging modality, as it is a safe approach and does not miss dangerous alternative diagnoses. Admittedly, Dr. Sternberg remarks that urologist’s historically dislike ultrasounds for assessing stone disease for several reasons: (i) we can’t see the ureter and may not find the stone, (ii) hydronephrosis is not always a reliable predictor of stone disease, (iii) it doesn’t give an accurate measurement of stone size, and (iv) provides more difficult counselling recommendations with patients when we don’t have the above information.
So, if ultrasound is the initial imaging modality of choice for a suspected stone, what happens in follow-up? Dr. Sternberg reviewed their institutional experience between 2009-2015, following patients for 90 days after their emergency department index visit (acute stone episode) . Among 10,680 episodes, 20% had an ultrasound as their initial imaging modality, with only 20% of these patients undergoing a CT scan in the subsequent 90 days. Overall, ~50% did not have a CT scan at their index visit and only 10% of these patients had a CT scan within 90 days. The average imaging cost was 183% higher if a CT scan was performed at the index visit compared to no CT, and the mean total radiation exposure was 8.1 mSv if a CT was obtained at the initial visit compared to 1.1 mSv if no CT scan was obtained at index visit. Dr. Sternberg and his colleagues concluded that of patients who underwent an initial ultrasound at their index visit, 80% of these patients avoided CT scanning in the subsequent 90 days resulting in reduced cost and radiation exposure.
One of the most significant concerns of urologists for patients that either receive no imaging or ultrasonography only, is the worry about long-term obstruction (which can be silent) and therefore we want to make sure there are no persistent stones in the ureter. Dr. Sternberg concludes that he feels the answer to this dilemma is multi-disciplinary guidelines/best practice statements to better standardize who gets what modality of imaging, and to educate all clinicians (urologists, radiologists and emergency physicians) to better understand each perspective and consider all aspects of these patient’s care.
Speaker(s): Kevan Sternberg, University of Vermont, Burlington, VT, 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
1. Smith-Bindman R, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med 2014;371(12):1100-1110.
2. Sternberg KM, et al. Trends in imaging use for the evaluation and followup of kidney stone disease: A single center experience. J Urol 2017 Feb 1 [Epub ahead of print].