S81.85 vs S81.851A
S81.85 (Open bite of lower leg) compared with S81.851A (Open bite, right lower leg, initial encounter), from the official CMS tabular data.
Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 20, 2026 · All releases and sources
Summary
These codes represent different levels of the same hierarchy: S81.85 is the non-billable header that contains S81.851A, so only S81.851A (or a sibling) is reported.
Registry fact- What is different?
Title wording and billing status.The titles share “Open bite”; S81.85 says “of lower leg” where S81.851A says “right lower leg, initial encounter”. S81.85 is a non-billable header; S81.851A is billable.
Registry fact
- Can these codes be reported together?
Not as a pair.S81.85 is the non-billable header that contains S81.851A. A header is not reported on a claim, so the choice is S81.851A or a sibling that matches the documentation.
Registry fact
- Is there an Excludes1 relationship?
None.Neither entry carries an Excludes1 note that names the other code. S81.85 carries 3 Excludes1 notes and S81.851A carries 3 Excludes1 notes covering other codes; the side-by-side table quotes them.
Official rule
- Is there an Excludes2 relationship?
None.Neither entry carries an Excludes2 note that names the other code. S81.85 carries 5 Excludes2 notes and S81.851A carries 5 Excludes2 notes covering other codes; the side-by-side table quotes them.
Official rule
- Is one more specific?
Yes.S81.851A is a subdivision of S81.85 in the tabular hierarchy, so it is the more specific of the two.
Registry fact
- Is one a parent or header code?
Yes.S81.85 is the non-billable header that contains S81.851A. A header stands for the whole family beneath it and is not reported on a claim.
Registry fact
- Are there sequencing instructions?
None.Neither entry carries a Code First or Use Additional Code note that names the other.
Official rule
- Are there other coding relationships?
None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.
MedCoder-derived
Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels
Can these codes be reported together?
Not as a pair — S81.85 is not reportable. S81.85 is the non-billable category that contains S81.851A.
A header stands for the whole family of codes beneath it and is not reported on a claim, so the choice is S81.851A or a sibling that matches the documentation. No Excludes1/Excludes2 relationship exists between these codes in the official tabular list.
Official guidance behind these answers
Section I.B.2 — Level of Detail in Coding · applies to: S81.85 and S81.851A
Diagnosis codes are to be used and reported at their highest number of characters available and to the highest level of specificity documented in the medical record. ICD-10-CM diagnosis codes are composed of codes with 3, 4, 5, 6 or 7 characters. Codes with three characters are included in ICD-10-CM as the heading of a category of codes that may be further subdivided by the use of fourth and/or fifth characters and/or sixth characters, which provide greater detail. A three-character code is to be used only if it is not further subdivided. A code is invalid if it has not been coded to the full number of characters required for that code, including the 7th character, if applicable.
ICD-10-CM Official Guidelines FY2027
Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum
Side by side
| S81.85Open bite of lower leg | S81.851AOpen bite, right lower leg, initial encounter | |
|---|---|---|
| Billing status | Non-billable header Report instead: S81.851A, S81.851D, S81.851S, S81.852A, S81.852D | Billable |
| Classification | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) |
| Definition | Open bite of lower leg is a non-billable ICD-10-CM category code (S81.85). | Open bite, right lower leg, initial encounter is a billable ICD-10-CM diagnosis code (S81.851A). |
| 7th character | The appropriate 7th character is to be added to each code from category S81 | The appropriate 7th character is to be added to each code from category S81 |
| Includes | Bite of lower leg NOS | — |
| Excludes1 | superficial bite of lower leg (S80.86-, S80.87-) open fracture of knee and lower leg (S82.-) traumatic amputation of lower leg (S88.-) | superficial bite of lower leg (S80.86-, S80.87-) open fracture of knee and lower leg (S82.-) traumatic amputation of lower leg (S88.-) |
| Excludes2 | open wound of ankle and foot (S91.-) burns and corrosions (T20-T32) frostbite (T33-T34) injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99) insect bite or sting, venomous (T63.4) | open wound of ankle and foot (S91.-) burns and corrosions (T20-T32) frostbite (T33-T34) injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99) insect bite or sting, venomous (T63.4) |
| Code also | any associated wound infection | any associated wound infection |
Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.
Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources