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Diagnosis Coding: Using the ICD-10-CM

Combination Codes

Assign a combination code only when that code fully identifies the diagnostic conditions involved or when the Alphabetic Index directs.

Don’t use multiple coding when the classification gives a combination code that clearly identifies all elements documented in the diagnosis.

When the combination code lacks necessary specificity in describing the manifestation or complication, use an additional code as a secondary code.

This chart shows examples of combination codes for certain conditions.

Table 3. Examples of ICD-10-CM combination codes
ICD-10-CM CodeDescription
K57.21Diverticulitis of large intestine with perforation and abscess with bleeding
E11.3411Type 2 diabetes mellitus with severe nonproliferative diabetic retinopathy with macular edema, right eye
I25.110Atherosclerotic heart disease of native coronary artery with unstable angina pectoris