Juan HC et al, 2012: Abdominal fat distribution on computed tomography predicts ureteric calculus fragmentation by shock wave lithotripsy
Juan HC, Lin HY, Chou YH, Yang YH, Shih PM, Chuang SM, Shen JT, Juan YS
Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
Abstract
OBJECTIVES: To assess the effects of abdominal fat on shock wave lithotripsy (SWL). We used pre-SWL unenhanced computed tomography (CT) to evaluate the impact of abdominal fat distribution and calculus characteristics on the outcome of SWL.
METHODS: One hundred and eighty-five patients with a solitary ureteric calculus treated with SWL were retrospectively reviewed. Each patient underwent unenhanced CT within 1 month before SWL treatment. Treatment outcomes were evaluated 1 month later. Unenhanced CT parameters, including calculus surface area, Hounsfield unit (HU) density, abdominal fat area and skin to calculus distance (SSD) were analysed.
RESULTS: One hundred and twenty-eight of the 185 patients were found to be calculus-free following treatment. HU density, total fat area, visceral fat area and SSD were identified as significant variables on multivariate logistic regression analysis. The receiver-operating characteristic analyses showed that total fat area, para/perirenal fat area and visceral fat area were sensitive predictors of SWL outcomes.
CONCLUSION: This study revealed that higher quantities of abdominal fat, especially visceral fat, are associated with a lower calculus-free rate following SWL treatment. Unenhanced CT is a convenient technique for diagnosing the presence of a calculus, assessing the intra-abdominal fat distribution and thereby helping to predict the outcome of SWL.
KEY POINTS:
• Unenhanced CT is now widely used to assess ureteric calculi.
• The same CT protocol can provide measurements of abdominal fat distribution.
• Ureteric calculi are usually treated by shock wave lithotripsy (SWL).
• Greater intra-abdominal fat stores are generally associated with poorer SWL results.
Eur Radiol. 2012 Aug;22(8):1624-30. doi: 10.1007/s00330-012-2413-6. Epub 2012 Mar 14
PMID: 22415413 [PubMed - indexed for MEDLINE]
Comments 1
Statistics!
Correlation does not inevitably imply cause. The ROC curves do not look very impressive. “In the present study, increasing age was considered a significant predictive factor for the success rate of SWL. ”In fact looking at the ROC curves age is nearly as good a prognosticator of stone fragmentation as Hounsfield units. So who will say to the patient: “You do not need a CT, your age predicts no good success with ESWL anyway.” Prospective studies with good numbers on factors predicting stone free rates are needed.
Peter Alken