Chapter 19 — Injury, Poisoning and Certain Other Consequences of External Causes
The 7th character, injury sequencing, traumatic fracture defaults and Gustilo characters, burns and corrosions, the four categories of drug toxicity, abuse coding and complications of care.
Chapter 19 turns on the 7th character, and the 7th character turns on one question: is active treatment being provided? Not whether this is the patient's first visit, not whether the provider has seen them before. A means active treatment; D means routine care during healing; S means a late effect.
Applying the 7th character#
| Character | Meaning | Rule |
|---|---|---|
A | Initial encounter | Used for each encounter where the patient is receiving active treatment for the condition. NEVER It does not mean the first visit. While the patient may be seen by a new or different provider over the course of treatment, assignment is based on whether the patient is undergoing active treatment |
D | Subsequent encounter | Used for encounters after the patient has completed active treatment and is receiving routine care during the healing or recovery phase |
S | Sequela | For complications or conditions that arise as a direct result of a condition, such as scar formation after a burn. Both the injury code that precipitated the sequela and the code for the sequela itself are used. The S is added only to the injury code, not to the sequela code. The specific type of sequela is sequenced first, followed by the injury code |
| Point | Detail |
|---|---|
| Complication codes and active treatment | For complication codes, active treatment refers to treatment for the condition described by the code, even though it may relate to an earlier precipitating problem. The guideline's example: T84.50XA is used when active treatment is provided for the infection, even though the condition relates to a prosthetic device placed at a previous encounter |
| Aftercare Z codes | NEVER Aftercare Z codes are not used for aftercare for injuries or poisonings where 7th characters identify subsequent care. For aftercare of an injury, assign the acute injury code with 7th character D |
| Fractures | Traumatic fracture categories have additional 7th character values beyond A, D and S |
Coding injuries#
| Rule | Detail |
|---|---|
| Separate codes | Assign separate codes for each injury unless a combination code is provided |
Category T07 unspecified multiple injuries | NEVER Not assigned in the inpatient setting unless information for a more specific code is not available |
| Surgical wounds | NEVER Traumatic injury codes S00–T14.9 are not used for normal, healing surgical wounds or to identify complications of surgical wounds |
| Sequencing | The code for the most serious injury, as determined by the provider and the focus of treatment, is sequenced first |
| Superficial injuries | NEVER Abrasions or contusions are not coded when associated with more severe injuries of the same site |
| Primary injury with minor damage to nerves or blood vessels | The primary injury is sequenced first, with additional codes for the nerve and spinal cord injuries (such as S04) and blood vessel injuries (such as S15) |
| Primary injury is to the blood vessels or nerves | That injury is sequenced first |
| Iatrogenic injuries | NEVER Chapter 19 injury codes are not assigned for injuries that occur during, or as a result of, a medical intervention. Assign the appropriate complication code(s) |
Traumatic fractures#
| Point | Rule |
|---|---|
| Default — open or closed | A fracture not indicated as open or closed is coded to closed |
| Default — displacement | A fracture not indicated as displaced or not displaced is coded to displaced |
| Multiple fracture sites | Fractures of specified sites are coded individually by site |
| Initial encounter characters | A, B, C for each encounter where the patient is receiving active treatment. Also assigned for a patient who delayed seeking treatment for the fracture or nonunion |
| Subsequent care | The appropriate 7th character for subsequent care after active treatment is complete |
| Nonunion | Subsequent care with nonunion — K, M, N |
| Malunion | Subsequent care with malunion — P, Q, R |
| Complications of surgical treatment for fracture repairs during healing or recovery | Coded with the appropriate complication codes |
| Open fracture designations — forearm, femur and lower leg including ankle | Based on the Gustilo open fracture classification. Where the Gustilo type is not specified, assign the 7th character for open fracture type I or II — B, E, H, M, Q |
| Multiple fractures sequencing | Sequenced in accordance with the severity of the fracture |
| Physeal fractures | Assign only the code identifying the type of physeal fracture. NEVER Do not assign a separate code to identify the specific bone fractured |
| Known osteoporosis | A code from M80, not a traumatic fracture code, for any patient with known osteoporosis who suffers a fracture — even after a minor fall that would not usually break a healthy bone |
| Aftercare | NEVER Aftercare Z codes are not used for traumatic fractures. Assign the acute fracture code with the appropriate 7th character |
Burns and corrosions#
| Rule | Detail |
|---|---|
| The distinction | Burns are thermal burns from a heat source such as a fire or hot appliance — except sunburns — and also burns from electricity and radiation. Corrosions are burns due to chemicals. The guidelines are the same for both |
| Classification | Current burns T20–T25 are classified by depth, extent and agent (X code). Depth: first degree (erythema), second degree (blistering), third degree (full-thickness). Burns of the eye and internal organs T26–T28 are classified by site but not by degree |
| Sequencing | Sequence first the code that reflects the highest degree of burn when more than one burn is present |
| Internal and external burns together | The circumstances of admission govern selection of the principal or first-listed diagnosis |
| Burns with smoke inhalation or respiratory failure | The circumstances of admission govern the selection |
| Same anatomic site, same side, different degrees | Classify to the subcategory identifying the highest degree recorded — for second and third degree burns of the right thigh, assign only T24.311- |
| Non-healing burns | Coded as acute burns. Necrosis of burned skin is coded as a non-healed burn |
| Infected burn site | ALWAYS Use an additional code for the infection |
| Separate sites | Assign separate codes for each burn site. T30 is extremely vague and should rarely be used. Codes for burns of multiple sites should only be assigned where the documentation does not specify the individual sites |
Extent of body surface — T31, T32 | For acute burns or corrosions when the site is not specified or when additional data is needed. Advisable as additional coding for evaluating burn mortality, and as an additional code when there is mention of a third-degree burn involving 20 percent or more of the body surface. NEVER Not used for sequelae of burns or corrosions |
| The rule of nines | Head and neck 9 percent, each arm 9 percent, each leg 18 percent, anterior trunk 18 percent, posterior trunk 18 percent, genitalia 1 percent. Providers may change these assignments for infants and children with proportionately larger heads, and for patients with large buttocks, thighs or abdomen involved in burns |
| Sequelae of burns | Encounters for treatment of late effects — scars, joint contractures — are coded with the burn or corrosion code with 7th character S |
| Current burn and sequela together | ALWAYS Both a current burn with 7th character A or D and a burn code with 7th character S may appear on the same record, because burns do not heal at the same rate |
| External cause | ALWAYS An external cause code identifies the source and intent of the burn, and the place where it occurred |
Adverse effects, poisoning, underdosing and toxic effects#
| Category | Sequence | Key points |
|---|---|---|
| Adverse effect — correctly prescribed and properly administered | 1the nature of the adverse effect2T36–T50 with 5th or 6th character 5 | Examples of the nature of an adverse effect: tachycardia, delirium, gastrointestinal haemorrhaging, vomiting, hypokalemia, hepatitis, renal failure, respiratory failure |
| Poisoning — improper use of a medication: overdose, wrong substance, wrong route | 1T36–T50 with the intent as the 5th or 6th character2additional code(s) for all manifestations | Intents: accidental, intentional self-harm, assault, undetermined. Intent unknown or unspecified → code as accidental. Undetermined is only for use where the record specifies that the intent cannot be determined. If abuse or dependence of the substance is also diagnosed, assign it as an additional code |
| Underdosing — taking less than prescribed, or discontinuing a prescribed medication on the patient's own initiative | T36–T50 with 5th or 6th character 6 | NEVER Never principal or first-listed. Documentation of a change in the patient's condition is not required. Add Z91.12-, Z91.13-, Z91.14-, Z91.A4- or Y63.6–Y63.9 to indicate intent, if known. If the patient relapses because of the reduced dose, code the medical condition itself |
| Toxic effect — a harmful substance ingested or contacted | 1T51–T65 first2codes for all associated manifestations | Toxic effect codes also carry an intent: accidental, intentional self-harm, assault, undetermined |
| General rules for T36–T65 | Detail |
|---|---|
| External cause codes | NEVER No additional external cause code is required for poisonings, toxic effects, adverse effects and underdosing — these are combination codes that include the substance and the intent |
| The Table of Drugs and Chemicals | NEVER Do not code directly from it. Always refer back to the Tabular List |
| How many codes | Use as many codes as necessary to describe completely all drugs, medicinal or biological substances |
| The same code twice | If the same code would describe the causative agent for more than one adverse reaction, poisoning, toxic effect or underdosing, assign the code only once |
| Two or more substances | Code each individually unless a combination code is listed in the Table of Drugs and Chemicals. If multiple unspecified drugs were taken, assign a code from T50.91 |
| Examples of poisoning | An error in drug prescription or administration by provider, nurse, patient or other person; an overdose intentionally taken; a nonprescribed drug taken with a correctly prescribed and properly administered drug; a reaction from the interaction of a drug and alcohol |
Abuse, neglect and other maltreatment#
| Situation | Codes |
|---|---|
| Confirmed abuse, neglect or maltreatment | 1T74.- sequenced first2any accompanying mental health or injury code(s)3an external cause code from the assault section X92–Y09 for physical injuries4a perpetrator code Y07 when the perpetrator is known |
| Suspected abuse, neglect or maltreatment | 1T76.- sequenced first2any accompanying mental health or injury code(s) |
| For suspected cases | NEVER Do not report an external cause or perpetrator code |
| Documentation test | If the record states abuse or neglect, it is coded as confirmed (T74.-). It is coded as suspected only if documented as suspected (T76.-) |
| Suspected physical abuse ruled out | Z04.71 adult, or Z04.72 child — NEVER not a code from T76 |
| Suspected rape or sexual abuse ruled out | Z04.41 adult, or Z04.42 child — NEVER not a code from T76 |
| Suspected forced sexual or forced labour exploitation ruled out | Z04.81 sexual exploitation, or Z04.82 labour exploitation — NEVER not a code from T76 |
Complications of care#
| Topic | Rule |
|---|---|
| General documentation rule | See Section I.B.16 — code assignment is based on the provider's documentation of the relationship between the condition and the care or procedure |
| Pain due to medical devices | Pain associated with devices, implants or grafts left in a surgical site — for example a painful hip prosthesis — is assigned to the appropriate Chapter 19 code, with additional codes from G89 (G89.18 or G89.28) to identify acute or chronic pain |
| Transplant complications other than kidney | Category T86 covers both complications and rejection. A transplant complication code is assigned only if the complication affects the function of the transplanted organ. Two codes are required: the T86 code and a secondary code identifying the complication. NEVER Pre-existing conditions, or conditions developing after the transplant, are not coded as complications unless they affect the function of the transplanted organ |
| Kidney transplant complications | T86.1- for documented complications such as transplant failure or rejection. NEVER T86.1- is not assigned for post kidney transplant patients who have CKD unless a complication is documented. Conditions other than CKD affecting the function of the transplanted kidney take T86.1- plus a secondary code. QUERY Query if the documentation is unclear |
| Complication codes that include the external cause | Some complications of care codes include the nature of the complication and the type of procedure that caused it. NEVER No external cause code indicating the type of procedure is necessary for these codes |
| Complications within the body system chapters | Intraoperative and postprocedural complication codes are found within the body system chapters. They are sequenced first, followed by a code for the specific complication if applicable. Body-system complication codes are assigned unless the complication is specifically indexed to a T code in Chapter 19 |
Practice questions#
Q1A patient with a closed tibial fracture is seen by a second orthopaedic surgeon for a new cast application. Active treatment is ongoing. Which 7th character is assigned?
- A
D, because a different provider is now managing the case - BThe appropriate initial-encounter character, because active treatment is ongoing
- C
S, because this is a subsequent visit - D
K, subsequent encounter with nonunion
Show answer & rationale
Correct answer: B. The appropriate initial-encounter character, because active treatment is ongoing
Rationale. Section I.C.19.a states that while the patient may be seen by a new or different provider over the course of treatment for an injury, assignment of the 7th character is based on whether the patient is undergoing active treatment and not whether the provider is seeing the patient for the first time, and that 7th character A initial encounter is used for each encounter where the patient is receiving active treatment. Section I.C.19.c.1 applies the same rule to fractures.
Q2A patient develops a haematoma during a surgical procedure, documented by the surgeon as occurring as a result of the intervention. What is assigned?
- AAn injury code from Chapter 19
- BThe appropriate complication code
- CBoth an injury code and a complication code
- DA symptom code only
Show answer & rationale
Correct answer: B. The appropriate complication code
Rationale. Section I.C.19.b.3 states that injury codes from Chapter 19 should not be assigned for injuries that occur during, or as a result of, a medical intervention, and that the appropriate complication code should be assigned. Section I.C.19.g.5 then directs where the complication code is found: intraoperative and postprocedural complication codes are in the body system chapters and are sequenced first.
Q3A patient has second and third degree burns of the right thigh. What is assigned?
- AA code for the second degree burn and a code for the third degree burn
- BOnly the code for the third degree burn of the right thigh
- CA code from
T30 - DOnly the code for the second degree burn
Show answer & rationale
Correct answer: B. Only the code for the third degree burn of the right thigh
Rationale. Section I.C.19.d.2 states that burns of the same anatomic site and on the same side but of different degrees are classified to the subcategory identifying the highest degree recorded in the diagnosis, and gives this exact example: for second and third degree burns of the right thigh, assign only code T24.311-. Section I.C.19.d.1 separately requires that the highest degree of burn be sequenced first where more than one burn is present.
Q4A patient takes half the prescribed dose of her antihypertensive because of cost, and is admitted with a hypertensive emergency. How is the underdosing reported?
- AThe underdosing code as the principal diagnosis
- BThe hypertensive emergency first, with the underdosing code
T46.-with 5th or 6th character 6 and aZ91.12-noncompliance code - COnly the noncompliance code
- DThe underdosing code and an external cause code for the drug
Show answer & rationale
Correct answer: B. The hypertensive emergency first, with the underdosing code T46.- with 5th or 6th character 6 and a Z91.12- noncompliance code
Rationale. Section I.C.19.e.5.c states that codes for underdosing should never be assigned as principal or first-listed codes, that if a patient has a relapse or exacerbation of the medical condition because of the reduction in dose the medical condition itself should be coded, and that noncompliance codes Z91.12-, Z91.13-, Z91.14- and Z91.A4- or complication of care codes Y63.6-Y63.9 are used with an underdosing code to indicate intent, if known. Section I.C.19.e confirms that no additional external cause code is required.
Q5A suspected case of child physical abuse is ruled out during the encounter. What is assigned?
- AA code from
T76 - B
Z04.72 - CA code from
T74 - D
Z04.42
Show answer & rationale
Correct answer: B. Z04.72
Rationale. Section I.C.19.f states that if a suspected case of abuse, neglect or mistreatment is ruled out during an encounter, code Z04.71 for alleged physical adult abuse ruled out or Z04.72 for alleged child physical abuse ruled out should be used, not a code from T76. Z04.42 is for alleged child rape, and Z04.81 and Z04.82 cover forced sexual and forced labour exploitation ruled out.
Scenarios#
A patient on long-term amiodarone, correctly prescribed and properly taken, is seen for new-onset hypothyroidism documented by the provider as an adverse effect of the amiodarone.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | E03.2 | Hypothyroidism due to medicaments and other exogenous substances — the nature of the adverse effect; first-listed |
| 2 | T46.2X5- | Adverse effect of other antidysrhythmic drugs, with the appropriate 7th character — verify in the Tabular List |
Rationale. Section I.C.19.e.5.a directs that when coding an adverse effect of a drug that has been correctly prescribed and properly administered, the appropriate code for the nature of the adverse effect is assigned first, followed by the appropriate code for the adverse effect of the drug from T36-T50 with 5th or 6th character 5. Section I.C.19.e confirms that no additional external cause code is required, because the T code already carries the substance and the intent. Section I.C.19.e.1 requires verification in the Tabular List rather than coding straight from the Table of Drugs and Chemicals.
Guideline: Section I.C.19.e, I.C.19.e.1, I.C.19.e.5.a
A patient is admitted after a house fire with third degree burns of the anterior trunk covering an estimated 25 percent of total body surface area, second degree burns of the left forearm, and smoke inhalation with acute respiratory failure. The circumstances of admission show that the respiratory failure drove the admission to the intensive care unit.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | J96.0- | Acute respiratory failure — principal diagnosis, because the circumstances of admission govern |
| 2 | T21.31X- | Burn of third degree of chest wall — verify the site code and 7th character in the Tabular List |
| 3 | T22.212- | Burn of second degree of left forearm — verify in the Tabular List |
| 4 | T31.20 | Burns involving 20-29% of body surface with 20-29% third degree burns |
| 5 | J70.5 / T59.- | The applicable code for smoke inhalation, as documented |
| 6 | External cause | X code for the source and intent of the burn, plus place of occurrence, activity and external cause status |
Rationale. Section I.C.19.d.1.c states that when a patient is admitted for burn injuries and other related conditions such as smoke inhalation or respiratory failure, the circumstances of admission govern the selection of the principal diagnosis. Section I.C.19.d.5 requires separate codes for each burn site, and I.C.19.d.6 advises using T31 as an additional code when there is mention of a third-degree burn involving 20 percent or more of the body surface. Section I.C.19.d.9 requires the external cause code for source, intent and place.
Guideline: Section I.C.19.d.1, I.C.19.d.5, I.C.19.d.6, I.C.19.d.9
A patient is seen for a scar contracture of the right hand from a burn sustained three years ago, and at the same visit for a new, healing second degree burn of the left forearm for which active treatment is complete.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | L90.5 | Scar conditions and fibrosis of skin — the nature of the sequela, sequenced first |
| 2 | T23.201S | Burn of second degree of right hand, sequela — verify in the Tabular List; the S goes on the injury code only |
| 3 | T22.212D | Burn of second degree of left forearm, subsequent encounter — verify in the Tabular List |
Rationale. Section I.C.19.a states that when using 7th character S it is necessary to use both the injury code that precipitated the sequela and the code for the sequela itself, that the S is added only to the injury code, and that the specific type of sequela is sequenced first. Section I.C.19.d.8 explicitly permits a current burn with 7th character A or D and a burn code with 7th character S on the same record, because burns do not heal at the same rate. Section I.B.10 supplies the general sequela rule.
Guideline: Section I.C.19.a, I.C.19.d.7, I.C.19.d.8, I.B.10
Primary sources#
- ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027CMS — the source document for every page on this site (effective 1 Oct 2026)
- NCHS ICD-10-CM files — Tabular List, Index, POA exempt listOfficial code files, addenda and the list of codes exempt from POA reporting
- ICD-10 Coordination and Maintenance CommitteeWhere code proposals are debated; agendas, summaries and meeting materials
- CMS ICD-10 homeCode sets, transition guidance and Medicare coding policy
- AHA Coding ClinicOfficial coding advice from the AHA Central Office — subscription required
- HHS OIG Work PlanActive audit topics — useful for prioritising internal coding audits
- MEDESUN Medical Coding AcademyTraining, credential preparation and audit services by the author