There are provided a medical assistance device, an operation method of a medical assistance device, a non-transitory computer-readable recording medium, and a medical assistance system allowing a user to use a diagnostic assistance program with confidence. A comparison determination unit compares a designated data range, which is designated as a range to be used for input data of a diagnostic assistance program, with a recommended data range, which is set for each diagnostic assistance program and is recommended as a range to be used for input data. The comparison determination unit outputs information regarding surplus data, which is data outside the recommended data range in the designated data range, and information regarding missing data, which is data outside the designated data range in the recommended data range. A difference information output unit outputs the information of the surplus data or the missing data as difference information.