S00.442 ICD-10-CM Code: External constriction of left ear

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for S00.442 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on S00.442 itself; “inherited from” names the category or block whose note applies here.

7th Character Guide

"The appropriate 7th character is to be added to each code from category S00"

• A — initial encounter
• D — subsequent encounter
• S — sequela

How the encounter character is assigned. “Initial encounter” means the patient is receiving active treatment for the condition — it is not limited to the first visit, and a different or new provider giving active treatment still assigns it. “Subsequent encounter” covers care during the healing or recovery phase after active treatment. “Sequela” is for complications or conditions that arise as a direct result of the original condition.

ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.19.a (paraphrased by MedCoder).

Variant codes in this family

S00.442A, S00.442D, S00.442S

Character meanings are CMS's official 7th-character extensions for this family, as carried in each variant code's official description; variant codes are registry rows. The explanation of how the encounter character is assigned is MedCoder editorial, distinct from the official content above it.

Coder workflow for S00.442

MedCoder structured workflow — derived from this code’s own official record

Before you code S00.442

1. S00.442 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

   ReviewS00.442A, S00.442D, S00.442S

   See the relationships section · Guide: How to choose an ICD-10-CM code →

2. A 7th character is required in this family. Confirm the documented encounter: initial (active treatment), subsequent (healing or recovery phase), or sequela. S00.442 is not valid without one. “Initial” means active treatment, not the first visit (Guidelines I.C.19.a).

   See the 7th Character Guide · Guide: 7th characters: initial, subsequent, sequela →

3. Laterality is coded in this family. Confirm the side documented — right, left, or bilateral — and select the matching code (this page’s code: left). The unspecified-side code applies only when the record states no side. Laterality is assigned from the documented side; where a bilateral code exists and both sides are documented, it is used instead of two unilateral codes (Guidelines I.B.13).

   ReviewS00.441 · right, S00.449 · unspecified

   Guide: Laterality coding →

4. Confirm the injury type, the anatomical site at the most specific level documented, laterality where the family codes it, and the encounter for the 7th character. Each injury is coded separately unless the classification provides a combination code, and a superficial injury is not coded when a more severe injury of the same site is documented. Injury chapter guidelines (Guidelines I.C.19.b, I.C.19.b.1).

   Guide: 7th characters: initial, subsequent, sequela →

5. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with S00.442. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

   See the official tabular notes

Choose the right path

1. Does the documentation support one of the more specific codes beneath S00.442?
   Yes → Select that code and continue the checks below on its own page.
   No → S00.442 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewS00.442A, S00.442D, S00.442S

2. Does the documentation support a condition named in S00.442’s Excludes1 note?
   Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
   No → Continue.

   ReviewS06.2, S06.3, S05, S01

3. Is the side documented?
   Yes → Select the code for the documented side (or the bilateral code when both sides are documented and one exists).
   No → Use the unspecified-side code only when the record states no side; a query is the alternative.

   ReviewS00.441 · right, S00.449 · unspecified

4. Is the encounter phase documented — active treatment, healing or recovery, or a sequela?
   Yes → Assign the matching 7th character; the variant codes are in the 7th Character Guide.
   No → The code is invalid without its 7th character — query for the missing element.

Consider S00.442. Then review the Code Also note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Anatomical site

At the most specific level the record states; a site the classification separates cannot be assumed from a procedure or a measurement.

Laterality

Right, left or bilateral as documented; unspecified only when the record states no side (Guidelines I.B.13).

Encounter type

Active treatment, healing or recovery phase, or sequela — the basis of the 7th character (Guidelines I.C.19.a).

External cause, place and activity

For the external cause codes reported with the injury or poisoning, where documented (Guidelines I.C.20.a).

Official instructions as workflow

• Excludes1 — check before selecting S00.442(4 notes)

  Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with S00.442: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

  CompareS06.2, S06.3, S05, S01

  See the official tabular notes · Guidelines I.A.12.a

• Excludes2 — not part of S00.442(9 notes)

  Coding workflow: The conditions named in this note are not included in S00.442. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  CompareT16, T17.3, T18.0, T17.2, T15, T63.4

  See the official tabular notes · Guidelines I.A.12.b

• Code Also — related condition(1 note)

  Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

  See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse S00.442 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of S00.442 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• S06.2— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of diffuse cerebral contusion moves the case to S06.2; the two are not reported together unless documented as unrelated.

  Full comparison: S00.442 vs S06.2 →

• S06.3— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of focal cerebral contusion moves the case to S06.3; the two are not reported together unless documented as unrelated.

  Full comparison: S00.442 vs S06.3 →

• S05— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of injury of eye and orbit moves the case to S05; the two are not reported together unless documented as unrelated.

  Full comparison: S00.442 vs S05 →

• S01— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of open wound of head moves the case to S01; the two are not reported together unless documented as unrelated.

  Full comparison: S00.442 vs S01 →

• S00.449— Specificity relationship (Review)

  Overlapping diagnoses in the same category.

  Overlapping codes in the same category — the documentation decides which is the more specific fit.

  What moves you there: A record that documents no more than “External constriction of unspecified ear” takes S00.449; specificity in the record moves it back here.

  Full comparison: S00.442 vs S00.449 →

• S00.441— Laterality relationship (Review)

  Same condition; these differ only in which side is documented.

  The same condition on the other side; the documented side decides, and a bilateral code, where one exists, replaces the pair when both sides are documented.

  What moves you there: A documented right side moves the case to S00.441.

  Full comparison: S00.442 vs S00.441 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

1. A 7th character applies in this family. Confirm the documented encounter matches the character assigned. See the official 7th-character definitions and this code’s variants
2. Laterality is coded in this family. Confirm the documented side matches the code — the opposite-side siblings are in the relationships section. See the opposite-side sibling codes
3. 1 Code Also note — a second code may apply; the guidelines leave its sequencing to the circumstances of the encounter. See the Code Also notes
4. 4 Excludes1 entries — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
5. 9 Excludes2 entries — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

• Not billable as written — a more specific code is required: S00.442A, S00.442D, S00.442S.
• Requires a 7th character. "The appropriate 7th character is to be added to each code from category S00" Options: S00.442A, S00.442D, S00.442S

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name S00.442 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 2 Excludes2 notes: S05 — Injury of eye and orbit (via S00.-), S09.3 — Other specified and unspecified injury of middle and inner ear (via S00.4.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Referenced by 3 Code Also instructions: G96.00 — Cerebrospinal fluid leak, unspecified (via S00.-), G96.08 — Other cranial cerebrospinal fluid leak (via S00.-), G96.09 — Other spinal cerebrospinal fluid leak (via S00.-).

These codes suggest coding this condition alongside when both are present.

Related Codes

Same condition, opposite side

Same category and title, differing only in which side of the body is affected.

S00.441 — External constriction of right ear (right)Compare S00.442 vs S00.441 →, S00.449 — External constriction of unspecified ear (unspecified)Compare S00.442 vs S00.449 →

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Constriction”; these codes share that main term but sit in a different category of the Tabular List.

K22.2 — Esophageal obstruction (esophagus), K31.1 — Adult hypertrophic pyloric stenosis (pylorus), K31.5 — Obstruction of duodenum (duodenum), N13.5 — Crossing vessel and stricture of ureter without hydronephrosis (ureter), N13.6 — Pyonephrosis (ureter, with infection), N47.1 — Phimosis (prepuce), O62.4 — Hypertonic, incoordinate, and prolonged uterine contractions (ring dystocia), Q31.1 — Congenital subglottic stenosis (larynx, congenital, subglottic), Q31.8 — Other congenital malformations of larynx (larynx, congenital), Q40.0 — Congenital hypertrophic pyloric stenosis (pylorus, newborn), S10.14 — External constriction of part of throat (external, throat), S10.84 — External constriction of other specified part of neck (external, supraclavicular fossa), S10.94 — External constriction of unspecified part of neck (external, neck), S20.14 — External constriction of part of breast (external, breast), S20.34 — External constriction of front wall of thorax (external, thorax, thoracic, front), S20.349 — External constriction of unspecified front wall of thorax (external, sternal region), S20.44 — External constriction of back wall of thorax (external, thorax, thoracic, back), S20.449 — External constriction of unspecified back wall of thorax (external, interscapular region), S20.94 — External constriction of unspecified parts of thorax (external, thorax, thoracic), S30.840 — External constriction of lower back and pelvis (external, pelvis), +24 more

Contextual Map

Every relationship of S00.442 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run S00.442 with these 5 related codes in Claim Check

Hierarchy

• S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00-S09 — Injuries to the head[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes2 notes

• S05 — Injury of eye and orbit[Excludes2](via S00.-): “superficial injury of eyelid (S00.1-S00.2)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S09.3 — Other specified and unspecified injury of middle and inner ear[Excludes2](via S00.4.-): “injury to external ear (S00.4-, S01.3-, S08.1-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Code Also instructions

• G96.00 — Cerebrospinal fluid leak, unspecified[Code Also](via S00.-): “head injury (S00-S09)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• G96.08 — Other cranial cerebrospinal fluid leak[Code Also](via S00.-): “head injury (S00 - S09)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• G96.09 — Other spinal cerebrospinal fluid leak[Code Also](via S00.-): “head injury (S00 - S09)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Nearest codes (40)

• S00 — Superficial injury of head[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00.429D — Blister (nonthermal) of unspecified ear, subsequent encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00.429S — Blister (nonthermal) of unspecified ear, sequela[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00.43 — Contusion of ear[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00.431 — Contusion of right ear[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00.431A — Contusion of right ear, initial encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00.431D — Contusion of right ear, subsequent encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S00.431S — Contusion of right ear, sequela[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Common coding questions

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to S00.442 in its code family, with their registry titles.

• S00.44 — External constriction of ear
• S00.441 — External constriction of right ear
• S00.441A — External constriction of right ear, initial encounter
• S00.441D — External constriction of right ear, subsequent encounter
• S00.441S — External constriction of right ear, sequela
• S00.442A — External constriction of left ear, initial encounter
• S00.442D — External constriction of left ear, subsequent encounter
• S00.442S — External constriction of left ear, sequela
• S00.449 — External constriction of unspecified ear
• S00.449A — External constriction of unspecified ear, initial encounter

View all codes in the S00 family