Hameed DA et al, 2013: Comparing non contrast computerized tomography criteria versus dual X-ray absorptiometry as predictors of radio-opaque upper urinary tract stone fragmentation after electromagnetic shockwave lithotripsy
Hameed DA, Elgammal MA, Elganainy EO, Hageb A, Mohammed K, El-Taher AM, Mostafa MM, Ahmed AI
Urology Department, Assiut University Hospital, Assiut, Egypt
Abstract
The objective of this study was to assess the value of dual X-ray absorptiometry (DXA) in comparison to non contrast computed tomography (NCCT) density as possible predictors of upper urinary tract stone disintegration by shock wave lithotripsy (SWL). This study included 100 consecutive patients, with solitary renal stone 0.5-2 cm or upper ureteral stone up to 1 cm. DXA to calculate stone mineral density (SMD) and stone mineral content (SMC) was done. NCCT was performed to measure Hounsfield units (HU). SWL was performed with an electromagnetic lithotripsy, plain X-ray documented disintegration after SWL. Successful treatment was defined as stone free or complete fragmentation after 1 or 2 sessions of SWL. The impact of patients age, sex, body mass index, stone laterality, location, volume, length, mean SMC and SMD, HU and Hounsfield density (HD), skin to stone distance (SSD) and number of shock waves were evaluated by univariate and multivariate analysis. Only 76 patients were available for follow-up. Success of disintegration was observed in 50 out of 76 patients (65.8 %). On multivariate analysis, SMC and number of shock wave were the significant independent factors affecting SWL outcome (p = 0.04 and p = 0.000, respectively). SMC as detected by DXA is a significant predictor of success of stone disintegration by SWL. SMC measured by DXA is more accurate than HU measured by CT. Patients with high stone mineral content (SMC greater than 0.65 g) should be directly offered another treatment option.
Urolithiasis. 2013 Nov;41(6):511-5. doi: 10.1007/s00240-013-0596-1. Epub 2013 Aug 3
PMID:23907170 [PubMed - in process]
Comments 1
By comparing x-ray absorptiometry (DXA) and CT-examinations to get measures of stone mineral content and Hounsfield units, the authors confirmed well established observations that stones with a high density are more difficult to disintegrate than those with a low density. In this regard they concluded that DXA was more useful than CT in predicting the outcome of SWL.
The clinical value of predicting the outcome of SWL by detailed pre-treatment studies is doubtful. In my own experience and with an efficient lithotripter also stones with a high density can usually be disintegrated although more shockwaves, higher power levels and repeated sessions might be necessary. It can be assumed that the patients in the report were treated with only one session, but the details on how SWL was carried out cannot be found. Neither can I find any information on the number of shockwaves despite the conclusion that this was a significant predictor. A relationship to stone composition was demonstrated in only 27 patients.
Hans-Göran Tiselius