K35.89 ICD-10-CM Code: Other acute appendicitis

Coder workflow for K35.89

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

Before you code K35.89

1. K35.89 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).

   ReviewK35.890, K35.891

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

2. “Other” (NEC) means the condition is specified in the record but no dedicated code captures it. Confirm the documented form is not one a sibling code names before settling on K35.89; if the record states no specifics at all, the unspecified sibling applies instead. “Other” codes are for documented conditions the classification gives no specific code; “unspecified” codes are for records lacking the detail (Guidelines I.A.9.a, I.A.9.b).

   See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

Choose the right path

1. Does the documentation support one of the more specific codes beneath K35.89?
   Yes → Select that code and continue the checks below on its own page.
   No → K35.89 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewK35.890, K35.891

Consider K35.89. Then 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).

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).

Any detail beyond this code’s title

What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

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 K35.89 with…

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

The codes most likely to be picked instead of K35.89 — 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.

• K35.80— 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 “Unspecified acute appendicitis” takes K35.80; specificity in the record moves it back here.

  Full comparison: K35.89 vs K35.80 →

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.

Verify Before Coding

• Not billable as written — a more specific code is required: K35.890, K35.891.

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 K35.89 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 1 Excludes1 note: K65 — Peritonitis (via K35.-).

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

Clinical classification (AHRQ CCSR):DIG009 — Appendicitis and other appendiceal conditions (default).

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 category (Appendicitis and other appendiceal conditions).

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, K35.3 — Acute appendicitis with localized peritonitis, 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, K35.890 — Other acute appendicitis without perforation or gangrene, K35.891 — Other acute appendicitis without perforation, with gangrene, K36 — Other appendicitis, K37 — Unspecified appendicitis, K38.0 — Hyperplasia of appendix, K38.1 — Appendicular concretions, K38.2 — Diverticulum of appendix, K38.3 — Fistula of appendix, K38.8 — Other specified diseases of appendix, K38.9 — Disease of appendix, unspecified, +5 more

Contextual Map

Every relationship of K35.89 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 K35.89 with this related code in Claim Check

Hierarchy

• K00-K95 — Chapter 11: Diseases of the Digestive System (K00-K95) (K00-K95)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35-K38 — Diseases of appendix[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes1 notes

• K65 — Peritonitis[Excludes1](via K35.-): “peritonitis with or following appendicitis (K35.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• DIG009 — Appendicitis and other appendiceal conditions[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

Nearest codes (19)

• K35 — Acute appendicitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35.2 — Acute appendicitis with generalized peritonitis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35.20 — Acute appendicitis with generalized peritonitis, without abscess[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35.200 — Acute appendicitis with generalized peritonitis, without perforation or abscess[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35.201 — Acute appendicitis with generalized peritonitis, with perforation, without abscess[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35.209 — Acute appendicitis with generalized peritonitis, without abscess, unspecified as to perforation[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35.21 — Acute appendicitis with generalized peritonitis, with abscess[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K35.210 — Acute appendicitis with generalized peritonitis, without perforation, with abscess[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 11 more

Change history (2)

• FY2019 — Became a non-billable header[Change history]— CMS release files (code change ledger) · icd10cm-fy2019
• and 1 more

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 K35.89 in its code family, with their registry titles.

• K35.219 — Acute appendicitis with generalized peritonitis, with abscess, unspecified as to perforation
• K35.3 — Acute appendicitis with localized peritonitis
• 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
• K35.8 — Other and unspecified acute appendicitis
• K35.80 — Unspecified acute appendicitis
• K35.890 — Other acute appendicitis without perforation or gangrene
• K35.891 — Other acute appendicitis without perforation, with gangrene

View all codes in the K35 family