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How to use Chapter 20 (External Cause of Morbidity) in ICD-10-CM

ICD-10 brought many changes to the medical coding scene. ICD-10 tries to capture as much information about a medical encounter as possible. This makes medical coding much more challenging, but hopefully improves outcomes.

More: View ICD-10-CM Chapters List

Most of ICD-10's new codes are found in Chapter 19 and 20.

• Chapter 19: Injury, poisoning and certain other consequences of external causes
• Chapter 20: External causes of morbidity

Codes in these chapters are used as complimentary codes which capture information about the situations surrounding an injury or illness, such as Fall Due to Ice and Snow, Chapter 20 (W00). Earlier ICD-10-CM chapters are for codes primary that represent an actual diagnosis like Stress facture (M84.3) or Listerial sepsis (A32.7).

Note: This article is referring to ICD-10-CM (Clinical Modification) when not otherwise specified.

Also See: How ICD-10-CM Chapter 19 Works

Chapter 20, External Causes of Morbidity (V00-V99, W00-W99, X00-X92, Y08-99)

Consisting of more than 7500 codes and 9% of the total volume of codes, this is the third largest chapter in ICD-10-CM. Codes in Chapter 20 report the cause of injury or health condition, the intent (unintentional/accidental or intentional such as suicide or assault), the place of injury, the activity of the patient at the time of injury, and the patient's status (military or civilian). These codes are never sequenced as first-listed or principal diagnosis. They are reported voluntarily by providers and provide data to research injuries and evaluate prevention strategies. There is no national requirement for mandatory reporting of external cause codes in ICD-10 reporting. Chapter 20 ICD-10 codes are, therefore, not required unless a provider is subject to state-based or payer-specified mandates.

An external cause code can be used with any code in the range of A00.0-T88.9, Z00-Z99 to designate a health condition due to an external cause, and in addition to injuries, can also be used for infections or diseases due to external sources or health conditions like a heart attack suffered due to strenuous physical activity like shoveling snow. Often, conditions are classifiable under Chapter 19, and codes from Chapter 20 provide additional information about the cause of the injury or condition. This rings true for conditions listed in Chapters 1-18 as well which may be caused by external causes. The appropriate seventh character is assigned to designate initial, subsequent, and sequela visits. Place, activity, and status codes are only used once at the initial encounter and are not applicable to poisonings, adverse effects, or late effects. Status codes indicate whether the injury or condition occurred during military activity, whether a non-military person was at work, and whether a student or volunteer was involved in the causal event.

Coding Guidelines:

• An external cause code can never be a first-listed principal diagnosis
• An external cause code is used secondary to a code from another chapter to provide further information about the nature of the injury or condition
• Multiple external cause codes should be assigned to completely describe and explain the injury or health condition
• Combination codes identify sequential events resulting in injury, such as fall resulting in striking against an object, with injury due to either event or both
• Selection of external cause codes is guided by the Alphabetic External Causes and Inclusion and Exclusion Notes in the Tabular List
• If the external cause and intent are already included in the code from another chapter, (for example, T36.0X2 - poisoning by penicillins, intentional self-harm), then an external cause code from Chapter 20 is not needed
• If the cause of injury is suspected, but not confirmed to be terrorism, then a code from category Y38 (terrorism) should not be used, and this should instead be classified as assault

Hierarchy of External Cause Codes:

If the format limits the number of external cause codes that can be assigned:

• Codes that are most related to the principal diagnosis should be reported first
• The cause should be reported before reporting the place, activity, or status. Place, activity, and status codes are assigned following all causal (intent) external cause codes
• The first-listed external cause codes should correspond to the cause of the most serious diagnosis
• External cause codes for child and adult abuse have first priority
• External cause codes for terrorist events (Y38) as identified by the Federal Government (FBI) and cataclysmic events have second priority
• External cause codes for transport accidents have third priority

External Cause Place, Activity, and Status Codes

External cause place, activity, and status codes provide more information about the injury or condition. A single code from category Y92, external cause place, is used to identify the place of occurrence of the external cause when applicable and known. The place of occurrence code is sequenced following the main external cause code(s). This code is assigned in conjunction with the activity code. A single code from category Y93, external cause activity, is assigned to indicate the activity at the time of injury or health condition (for example, walking, running, water sports, activities involving snow or ice, climbing, jumping, dancing, sports and athletics, activities involving computers and electronics, arts and crafts, caregiving, personal hygiene, cooking, roller coasters, musical instruments, animal care, or unspecified). A single code from category Y99, external cause status, is assigned to indicate the work status of the patient at the time of the injury. Several external cause codes may be assigned, but there can be only one place code, one activity code, and one status code assigned to an encounter. These external cause place, activity, and status codes are only used once at the initial encounter and are not applicable to poisonings, adverse effects, misadventures, or sequela (late effects).

Adult and Child Abuse

Adult and child abuse, neglect and maltreatment are classified as assault. Assault codes can indicate the external cause of injury for confirmed abuse, and a perpetrator code from category Y07 indicates the relationship between the victim and the perpetrator.

Coding Example: A college student is the victim of a random beating in a park. The care provider describes the injuries as a head injury with loss of consciousness for 40 minutes, with a negative MRI for fractures or internal bleeding. The appropriate diagnosis codes here would be S06.9X2A - unspecified intracranial injury with loss of consciousness of 31 minutes to 59 minutes, initial encounter; Y04.0XXA - assault by unarmed brawl or fight, initial encounter; and Y92.830 - public park as the place of occurrence of the external cause.

Transport Accidents

All transport accidents are assumed as accidental intent. If the intent is unknown in terms of unintentional (accidental) or intentional (self-harm or assault), then the intent should be coded as accidental by default. Undetermined intent is only used in external cause codes if the intent cannot be determined. A transport accident involves a moving or running vehicle. Land transport accident codes (V01-V89) reflect the mode of transport, and the vehicle is the most important component identified by the first two characters, because this information is needed to outline preventative measures.

Coding Example: A pizza delivery car collided with a pickup truck on the interstate highway and the driver confessed to using his cell phone when the collision occurred. The appropriate diagnosis codes here would be V43.53XA - car driver injured in collision with pick-up truck in traffic accident, initial encounter; Y92.411 - interstate highway as the place of occurrence of the external cause; Y93.C2 - activity, hand-held interactive electronic device; and Y99.0 - civilian activity done for income or pay.

External Cause Sequelae

Late effects or sequela of a previous injury are reported using the seventh character S. These external cause codes for sequela should not be used with related codes specifying the nature of the current injury. External cause codes for sequela should also not be used when no late effect is documented and the subsequent visit is for routine followup care to assess healing or receive rehabilitation.