Skip to main content

K35.3 ICD-10-CM Code: Acute appendicitis with localized peritonitis

Compare with another code for K35.3Check this code on a claim

Billing Status: NO. This is a non-billable ICD-10-CM code: report a more specific billable code beneath it.

Not billable · FY2027A non-billable heading in the tabular list: report a more specific code beneath it.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too, and is marked with where it comes from.

The tabular list publishes no instructional note for this code itself.

Where it sits Source: CMS/NCHS

Under:Chapter 11: Diseases of the Digestive SystemK35-K38 Diseases of appendixK35 Acute appendicitis

Codes under K35.3 (4)

  • K35.30Acute appendicitis with localized peritonitis, without perforation or gangreneBillable
  • K35.31Acute appendicitis with localized peritonitis and gangrene, without perforationBillable
  • K35.32Acute appendicitis with perforation, localized peritonitis, and gangrene, without abscessBillable
  • K35.33Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscessBillable

CompareCheck ClaimView Related Codes

Coder workflow for K35.3

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

Before you code K35.3

  1. K35.3 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).

    ReviewK35.30, K35.31, K35.32, K35.33

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

  2. K35.3’s title joins a condition with an associated condition or complication. Confirm each component is documented. Where the classification presumes the link through the “with” convention, only a provider statement that the conditions are unrelated defeats it. A combination code is assigned only when it fully identifies the documented conditions; a required second code for the stage, type or manifestation is still reported when the notes ask for it (Guidelines I.B.9, I.A.15).

    Guide: Combination codes →

Choose the right path

  1. Does the documentation support one of the more specific codes beneath K35.3?
    Yes → Select that code and continue the checks below on its own page.
    No → K35.3 cannot be reported as written. Where the codes beneath it include an unspecified code, that code applies when the record goes no further; otherwise query for the missing detail.

    ReviewK35.30, K35.31, K35.32, K35.33

Report the code beneath K35.3 that the documentation supports, not K35.3 itself. Then confirm that code is valid for the date of service on its own page.

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).
Acuity
Acute or chronic as documented; when both are documented and separate codes exist, both are reported with the acute code first (Guidelines I.B.8).
The associated condition or complication
Whether the associated condition the title names is documented; the “with” convention presumes some links, and a provider statement that the conditions are unrelated defeats it (Guidelines I.A.15).

Coding decision scenarios

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

Documentation: Only one of the components this code’s title joins is documented.

Coding question: Is the code beneath K35.3 supported?

Path: Review the code for the documented component on its own.

Reason: A combination code is assigned only when it fully identifies the documented conditions; otherwise the documented component takes its own code (Guidelines I.B.9).

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 K35.3 with…

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

The codes most likely to be picked instead of K35.3 — 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.

  • K35.8— 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 “Other and unspecified acute appendicitis” takes K35.8; specificity in the record moves it back here.

    Full comparison: K35.3 vs K35.8 →

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.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Acute appendicitis with localized peritonitis is a non-billable ICD-10-CM category code (K35.3). A more specific billable subcode must be selected for claims submission.

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

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-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name K35.3 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 Excludes1 notes: K37 — Unspecified appendicitis, K65 — Peritonitis (via K35.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 2 Excludes2 notes: K63.0 — Abscess of intestine, K63.1 — Perforation of intestine (nontraumatic).

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

Clinical classification (AHRQ CCSR):DIG009 — Appendicitis and other appendiceal conditions (default); DIG016 — Peritonitis and intra-abdominal abscess.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical categories (Appendicitis and other appendiceal conditions, Peritonitis and intra-abdominal abscess).

A74.81 — Chlamydial peritonitis, K35.2 — Acute appendicitis with generalized peritonitis, K35.20 — Acute appendicitis with generalized peritonitis, without abscess, K35.200 — Acute appendicitis with generalized peritonitis, without perforation or abscess, K35.201 — Acute appendicitis with generalized peritonitis, with perforation, without abscess, K35.209 — Acute appendicitis with generalized peritonitis, without abscess, unspecified as to perforation, K35.21 — Acute appendicitis with generalized peritonitis, with abscess, K35.210 — Acute appendicitis with generalized peritonitis, without perforation, with abscess, K35.211 — Acute appendicitis with generalized peritonitis, with perforation and abscess, K35.219 — Acute appendicitis with generalized peritonitis, with abscess, unspecified as to perforation, K35.30 — Acute appendicitis with localized peritonitis, without perforation or gangrene, K35.31 — Acute appendicitis with localized peritonitis and gangrene, without perforation, K35.32 — Acute appendicitis with perforation, localized peritonitis, and gangrene, without abscess, K35.33 — Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess, K35.80 — Unspecified acute appendicitis, K35.89 — Other acute appendicitis, K35.890 — Other acute appendicitis without perforation or gangrene, K35.891 — Other acute appendicitis without perforation, with gangrene, K36 — Other appendicitis, K37 — Unspecified appendicitis, +44 more

Contextual Map

Every relationship of K35.3 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 K35.3 with these 4 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

  • K37 — Unspecified appendicitis[Excludes1]: “unspecified appendicitis with peritonitis (K35.2-, K35.3-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027
  • K65 — Peritonitis[Excludes1](via K35.-): “peritonitis with or following appendicitis (K35.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027

Referenced by Excludes2 notes

Clinical classification (CCSR)

Nearest codes (19)

Change history (2)

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Common coding questions

MedCoder editorial

Can K35.3 be billed directly?

No. K35.3 (Acute appendicitis with localized peritonitis) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

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 FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 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-derived 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 editorial 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.

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 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "K35.3 — Acute appendicitis with localized peritonitis." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/k35.3-acute-appendicitis-with-localized-peritonitis

Change history

  • FY2019 — October 1, 2018
    Became a non-billable header
    FY2019 changes
  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Acute appendicitis with localized peritonitis

Nearest Codes in This Family

Official ICD-10-CM classifications closest to K35.3 in its code family, with their registry titles.

View all codes in the K35 family