S21.451A — Open bite of right back wall of thorax with penetration into thoracic cavity, initial encounter
Is S21.451A billable?
Yes — S21.451A is billable for FY2027. S21.451A is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. S21.451A may be submitted for encounters from October 1, 2026 through September 30, 2027.
S21.451A at a glance
| Code | S21.451A |
|---|---|
| Description | Open bite of right back wall of thorax with penetration into thoracic cavity, initial encounter |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
| 7th character "A" | initial encounter |
What does the 7th character "A" mean in S21.451A?
In S21.451A, the 7th character A means initial encounter. The 7th character is required for S21.451A to be a valid, complete code.
Same condition, different episode of care — switch the 7th character:
Which MS-DRGs does S21.451A group to?
S21.451A sits in MDC 21 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 913Traumatic Injury with MCCmedical
- 914Traumatic Injury without MCCmedical
As a secondary diagnosis, S21.451A is a major complication or comorbidity (MCC), which can move a stay into a higher-paying DRG.
How is S21.451A listed in the Alphabetic Index?
The Alphabetic Index lists these routes under S21.45, the nearest indexed parent of S21.451A. Use them to find the family, then select the specific code.
- Bite › thorax, thoracic › back › with penetration into thoracic cavity (s) (animal) (human)
Excludes1 — never code together — inherited from S21
The conditions below can never be reported together with S21.451A on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- traumatic amputation (partial) of thorax (S28.1)
Excludes1 — never code together — inherited from S21.45
The conditions below can never be reported together with S21.451A on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
- superficial bite of back wall of thorax (S20.47)
Use additional code — inherited from Chapter 19
Report an additional code alongside S21.451A to fully describe the condition. S21.451A is sequenced first.
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes2 — not included here — inherited from Chapter 19
The conditions below are not part of S21.451A, but a patient may have both at the same time. When documentation supports it, S21.451A and the excluded code may both be reported.
Excludes2 — not included here — inherited from S20-S29
The conditions below are not part of S21.451A, but a patient may have both at the same time. When documentation supports it, S21.451A and the excluded code may both be reported.
- burns and corrosions (T20-T32)
- effects of foreign body in bronchus (T17.5)
- effects of foreign body in esophagus (T18.1)
- effects of foreign body in lung (T17.8)
- effects of foreign body in trachea (T17.4)
- frostbite (T33-T34)
- injuries of axilla
- injuries of clavicle
- injuries of scapular region
- injuries of shoulder
- insect bite or sting, venomous (T63.4)
Code also — inherited from S21
Two codes may be needed to describe the condition fully. Whether S21.451A is sequenced first depends on the reason for the encounter.
How long has S21.451A existed?
S21.451A has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.