Orthopedic Coding Alert

Question: We have been getting denials when using a diagnosis code for underlying disease. For example, when coding for an amputation at the knee with a diagnosis of gangrene second to diabetes mellitus, we have been coding for the gangrene and then coding for the diabetes mellitus and getting denied. If we do not use the diabetes code, we have no problems with payment, but is that correct?

Carolyn, ORC subscriber and coder
San Diego, CA

Answer: According to the ICD-9-CM Diagnosis Coding Rules (American Hospital Association, as well as HCFA interpretation), the diabetes should be coded first and the gangrene second. When referencing code 785.4 (gangrene) in the ICD-9-CM tabular list, there is a statement that tells the coder to Code first any associated underlying condition: diabetes (250.7x). This may seem backwards because the condition treated is the gangrene. However, without the diabetes, the patient probably would not have developed gangrene. Therefore, assign the codes as follows: 250.7x, then 785.4

For the fifth digit on the 250 code, the selection is based on whether the patient is insulin dependent, if their diabetes controlled or uncontrolled, or if they are not specified as insulin dependent or controlled or uncontrolled. More information is required to know these options, but it greatly reduces your risk for denial when the disease is coded to the highest level of specificity.