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COLANGIORESONANCIA (CPRM) VS ULTRASONIDO (US)
FOCALIZADO EN PACIENTES CON ICTERICIA O SOSPECHA
DE OBSTRUCCION DE LA VIA BILIAR. RESULTADOS
PRELIMINARES
Drs. David Busel M(1), Lizbeth Pérez M(2), Alejando Arroyo P(1), Dulia Ortega T(1), Juan Pablo Niedmann E(1),
Patricio Palavecino R(1), Paula Csendes G(1), Alejandra López P(1), Rolf Franz C(1), Jorge Díaz J(1), Pablo Soffia S(3),
RosaDomínguez O(4), TMs. Juan Maulen A(1), Cristián Garrido I(1), Sr. Jorge Rodríguez T(5).
1. Unidades de Cuerpo y Ultrasonido, Centro de Imagenología, Hospital Clínico de la U. de Chile.
2. Residente de Radiología, Centro de Imagenología, Hospital Clínico de la U. de Chile.
3. Radiólogo Asociado de Diagnóstico por Imágenes, Clínica Alemana de Santiago.
4. Profesor visitante Hospital Vall d’ Hebron,Barcelona, España.
5. Unidad de Bioestadística de la Escuela de Salud Pública de la U. de Chile.

Abstract: Between January and July, 2003, a single
blinded matched trial was done to assess focalized
biliary ultrasound (US) and MR cholangiography
(MRCP) compared with ERCP or surgery as reference
standard in patients with suspected biliary obstruction.
Focalized US was performed 24 hrsbefore/after
MRCP. Patients were triage according symptoms,
signs and laboratory in high, intermediate and low
risk for obstruction. Radiologists sonographers were
divided in low and highly experienced. None of the
radiologist who reported either US or MRCP was
aware to the other test results. Sensitivity, Specificity,
PPV and NPV, (LR) Likelihood Ratios and pre and
post-test odds for positiveand negative test were
estimated.
We analized 64 out of 76 sampled patients, the
prevalence of obstruction was 37 % (24 out of 64
patients). US found biliary tree dilated in 50% and
MRCP in 48% of the patients. Main cause of
obstruction 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 non
experienced radiologistperform the exam, and 70%
when an experienced radiologist doest it. Specificity

Busel D. y cols. Colangioresonancia (CPRM) vs ultrasonido (US) focalizado en pacientes con ictericia o sospecha de obstrucción de la vía biliar. Resultados preliminares. Rev Chil Radiol 2003; 9: 173-181.
Correspondencia: Dr. David Busel M.
Santos Dumont 999, Independencia, Santiago de Chile.
dbusel@hotmail.com(Sp) 82,5%, PPV 66.7% and NPV 76.7%. RMCP
Shown 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 focalized
US in overall patients with high risk of obstruction
(37.5%), detecting the cause of obstruction but using
aditional sequences rising the examination timeand
costs. With a positive ultrasound and LR(+) 3.3 pretest odds rise from 0.37/37% to a post-test odds of
0.55/55% and with negative test result and LR(-) 0.49
pre-test odds 0.37/37% will decrease to post-test odds
of 0.2/20%. With MRCP a positive test with LR(+) 7.7
initial pre-test odds 0.37/37.5% to post-test odds of
0.8/ 80% and with a negative test result LR(-) 0.05
pretest odds0.37/37% will decrease to post-test odds
of 0.03%.
Ultrasound performed by experienced
sonographers has a Specificity and NPV over 80%,
and perform similar to MRCP for detecting biliary
tree dilatation the best predictor of obstruction. In
patients with low pre-test odds (low risk) of obstruction,
to use focalized US and then MRCP, when the cause
of obstruction is not diagnosed could be the morecost/
efective initial alternative in this patients. This data must
be confirmed with further studies with cost/effectivenes
analysis.
Keywords: Bile ducts, Magnetic Resonance,
Ultrasonography, RMCP, Sensitivity, Specificity,
Predictive values.
Resumen: Introducción. Existe controversia en el
algoritmo de estudio de obstrucción de la vía biliar
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