STONE DISEASE

Plain radiography still is required in the planning of treatment for urolithiasis
Lamb AD, Wines MD, Mousa S, Tolley DA
The Scottish Lithotriptor Centre, Edinburgh, United Kingdom
J Endourol. 2008; 22: 2201-5

• Introduction: Nonenhanced computed tomography (NCT) is recognised as the most sensitive tool in diagnosis of renal tract calculi. However, its role as the sole imaging investigation, for decisions regarding management is less clear.
  Objective: To determine the proportion of new stone patient referrals in which management is altered by interpretation of a plain abdominal kidneys, ureters and bladder (KUB) radiograph in addition to NCT.
• Methods: One hundred consecutive new referrals to a national lithotripsy centre were considered prospectively for treatment of renal tract calculi.
• Results: A significant change in management was undertaken in 17 patients on the basis of KUB findings. Eleven patients had radio-lucent ureteric stones, for which Extracorporeal Shockwave Lithotripsy (ESWL) was consequently not possible and who required endoscopic management. There were six inaccuracies in measurement of size or positioning on NCT. In a further 43 patients it was not possible to confirm management until the KUB was reviewed, although in these cases ESWL or expectant management was still pursued. Thus additional imaging with a KUB was required in order to confirm optimum management in 60 patients.
• Conclusion: Additional plain radiography confers a significant advantage in the planning of treatment for urolithiasis once the diagnosis has been established by NCT because of information it provides regarding radio-opacity as well as stone size and visibility. This information cannot be delivered by NCT alone. We therefore recommend that KUB imaging is performed on all new stone patients referred for treatment.
  
  
• Editorial Comment
  The study population is a select group - patients referred to a well-established national lithotripsy service in Scotland under well-established protocol and guidelines. The study may therefore underestimate the value of KUB - it is feasible that other patients evaluated at the point of entry (local urologist) may have undergone KUB imaging and a decision was made not to proceed with referral for SWL. In addition, the authors do not report the time interval between CT scan imaging at the local urologist office and subsequent KUB imaging at the tertiary referral center. It is possible that the impact reported for KUB was reflective of movement of the stone over time rather than added clarity from additional imaging.
  The authors did not evaluate the utility of Hounsfield units to predict the radiolucent characteristic of the stone - it is possible that could negate the need for plain radiography. The authors did not have a PACS system that allowed them to directly measure stone size on the CT scan, nor did they have access to the full CT scan images - rather they relied on “select hard copies”. One would anticipate that the predictive value of CT scan imaging would increase were all the images available for review.
  The authors note that renal pelvic and lower pole anatomy is helpful to predict shockwave success, however they do not report how this was interpreted on plain radiography. Coronal reconstructions of the NCCT may have provided useful information in this regard. The authors do not report the number of observers who measured the stones on radiographic imaging, nor do they comment on the inter-observer reliability of such measurements on CT and KUB.

Dr. Manoj Monga
Professor, Department of Urology
University of Minnesota
Edina, Minnesota, USA
E-mail: endourol@yahoo.com