COLANGIORESONANCIA (CPRM) VS ULTRASONIDO (US) FOCALIZADO EN PACIENTES CON ICTERICIA O SOSPECHA DE OBSTRUCCION DE LA VIA BILIAR: RESULTADOS PRELIMINARES

Abstract

Abstract: Between January and July, 2003, a singleblinded matched trial was done to assess focalizedbiliary ultrasound (US) and MR cholangiography(MRCP) compared with ERCP or surgery as referencestandard in patients with suspected biliary obstruction.Focalized US was performed 24 hrs before/afterMRCP. Patients were triage according symptoms,signs and laboratory in high, intermediate and lowrisk for obstruction. Radiologists sonographers weredivided in low and highly experienced. None of theradiologist who reported either US or MRCP wasaware to the other test results. Sensitivity, Specificity,PPV and NPV, (LR) Likelihood Ratios and pre andpost-test odds for positive and negative test wereestimated. We analized 64 out of 76 sampled patients, theprevalence of obstruction was 37 % (24 out of 64patients). US found biliary tree dilated in 50% andMRCP in 48% of the patients. Main cause ofobstruction was common bile duct stones in (16) 25%.and tumors were the second more common cause.US shown a Sensitivity (S) 58.3% when a nonexperienced radiologist perform the exam, and 70%when an experienced radiologist doest it. Specificity(Sp) 82,5%, PPV 66.7% and NPV 76.7%. RMCPShown S 95.8%, Sp 87.5%, PPV 82.1%, NPV 97.2%For common bile duct stones US shown a PPV 53.3%and NPV 83.6% on the other hand MRCP a PPV 70%and NPV 95.4%. MRCP perform better than focalizedUS in overall patients with high risk of obstruction(37.5%), detecting the cause of obstruction but usingaditional sequences rising the examination time andcosts. With a positive ultrasound and LR(+) 3.3 pre-test odds rise from 0.37/37% to a post-test odds of0.55/55% and with negative test result and LR(-) 0.49pre-test odds 0.37/37% will decrease to post-test oddsof 0.2/20%. With MRCP a positive test with LR(+) 7.7initial pre-test odds 0.37/37.5% to post-test odds of0.8/ 80% and with a negative test result LR(-) 0.05pretest odds 0.37/37% will decrease to post-test oddsof 0.03%. Ultrasound performed by experiencedsonographers has a Specificity and NPV over 80%,and perform similar to MRCP for detecting biliarytree dilatation the best predictor of obstruction. Inpatients with low pre-test odds (low risk) of obstruction,to use focalized US and then MRCP, when the causeof obstruction is not diagnosed could be the more cost/efective initial alternative in this patients. This data mustbe confirmed with further studies with cost/effectivenesanalysis.Keywords: Bile ducts, Magnetic Resonance,Ultrasonography, RMCP, Sensitivity, Specificity,Predictive values.Resumen: Introduccion. Existe controversia en elalgoritmo de estudio de obstruccion de la via biliar