Patient medical records contain a large amount of information distributed in different kinds of documents: diagnosis, prescription, symptom observations or radiology analysis, etc. Document heterogeneity makes specific information retrieval difficult for medical staff. This paper shows how a semantic model of documents assists in handling information stored in these documents. It allows the definition of a generic semantic structure of a medical record: this structure expresses the implicit content of each document element by specifying what kind of information is required. Moreover, it permits a display of relevant information for a specific reader.