THE WHOLE STORY You can use external cause codes to add more detail to your claims to accurately describe patient injuries.

Hidden within the elaborate ICD-10-CM coding system is a system of numerical shorthand that lets your coders tell the story behind a patient's injury or health condition. These add-on codes let you assign as many external cause codes as necessary to explain the patient's condition to the fullest extent possible. Though there is no national mandate requiring their use, certain payers and state-based organizations require external cause codes, arguing that they're helpful in terms of injury research and evaluation of injury prevention strategies.

There are 4 different types of external cause codes. Each code answers one of the following questions: How did the injury or condition happen? Where did it happen? What was the patient doing when it happened? Was it intentional or unintentional?

External cause codes are never sequenced as the first-listed or principal diagnosis — instead, these are listed in addition to the main injury code to provide more information about what caused the condition. If you're having trouble coding external causes, or need to provide enhanced claims for your payers or state regulators, here is your primer on how to use them.

The basics
You can add an external cause code to any diagnosis in the range of A00.0 through T88.9 in ICD-10, but they are primarily applicable to acute injuries from Chapter 19 (S00 to T88). Let's walk through an example: If a patient arrives with an acute right anterior cruciate ligament sprain, caused by a slip and fall, the injury and external cause would be reported with the following codes:

• S83.511A Sprain of anterior cruciate ligament of right knee, initial encounter
• W01.0XXA Fall on same level from slipping, tripping and stumbling without subsequent striking against object, initial encounter

If your physician includes the external cause in his documentation, start by recording the initial injury code and then assigning the appropriate action code from the V00-Y84 categories in Chapter 20. Note that these codes often have a 7th character requirement. There can be 3 options for this 7th character: A for initial encounter, D for subsequent encounter and S for sequela (complications or conditions that arise as a direct result of the injury, such as pain or scar formation).

While a few different providers may see the patient over the course of treatment for an injury, the assignment of the 7th character for the external cause should match the 7th character of the code assigned for the associated injury or condition. In the example above, the secondary action code has an A in the 7th spot, matching the A in principal injury code.

More options to consider
Keep in mind that you may report multiple external cause codes. After you assign the initial action code, you can then add place of occurrence codes, activity codes and external cause status codes that further describe the injury. These should only be used if they are described in the physician's notes and when applicable. They are listed on the claim after the initial external cause action code. Here's a quick rundown:

• Place of occurrence codes are found in category Y92 of the manual. These identify the location of the patient at the time of injury.
• Activity codes are found in category Y93. They are used to describe the patient's activity at the time of the injury.
• External cause status codes are found in category Y99. A code from category Y99 should be assigned with another external cause code except for codes signifying poisoning, adverse effect, misadventure or late effect.

There are questions as to why codes Y92.9 (unspecified place or not applicable), Y93.9 (activity, unspecified) and Y99.9 (unspecified external cause status) exist if ICD-10-CM guidelines specifically state not to use them. Think of these as "placeholder" codes in the event that their use becomes further clarified later on. These categories are only used at the initial encounter for treatment, so it is not necessary to report these additional codes on subsequent visits for the same injury.

Bringing it all together
We can now go back to our initial example of a patient slipping and falling, causing an acute right anterior cruciate ligament sprain. Imagine if this scenario had been further specified in the surgeon's notes, stating this is a workers' compensation case where the patient was constructing a building, slipped, fell and hit his knee on a belt sander, which caused the right anterior cruciate ligament sprain. The surgeon performs an arthroscopic repair of the right anterior cruciate ligament. In that circumstance, you could apply the following codes as seen in "External Cause Codes for an ACL Repair." OSM