Final answer:
In medical coding, when there are diseases that require two codes to completely describe the condition, a combination code is used.
Step-by-step explanation:
In medical coding, when there are diseases that require two codes to completely describe the condition because all of the facts of the disease are not expressed in one code, a combination code is used. This combination code includes the primary disease or condition code followed by a secondary code that provides additional information about the disease or condition. For example, in the ICD coding system, when coding for diabetes with chronic kidney disease, two codes are used: one for diabetes and another for chronic kidney disease.