This paper describes the participation of the EMSE team at the clinical decision support track of TREC 2015 (Task A). Our team submitted three automatic runs based only on the summary field. The baseline run uses the summary field as a query and the query likelihood retrieval model to match articles. Other runs explore different approaches to expand the summary field: RM3, LSI with pseudo relevant documents, semantic ressources of UMLS, and a hybrid approach called SMERA that combines LSI and UMLS based approaches. Only three of our runs were considered for the 2015 campaign: RM3, LSI and SMERA.