Nowadays, the need for well-structured ontologies in the medical domain is rising, especially due to the significant support these ontologies bring to a number of groundbreaking applications, such as intelligent medical diagnosis system and decision-support systems. Indeed, the considerable production of clinical data belonging to restricted subdomains has stressed the need for efficient methodologies to automatically process enormous amounts of unstructured, domain-specific information in order to make use of the knowledge these data provide. In this work, we propose a lexicon-grammar-based method for efficient information extraction and retrieval from unstructured medical records in order to enrich a simple ontology descriptive of such a kind of documents. We describe the NLP methodology for extracting RDF triples from unstructured medical records, and show how an existing ontology built by a domain expert can be populated with the set of triples and then enriched through its linking to external resources.