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.
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.
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.
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.
• 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]
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.