K38.1 ICD-10-CM Code: Appendicular concretions

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for K38.1 in the official ICD-10-CM tabular list, quoted as published.

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

Indexed Clinical Terms (4)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

• Calculus, calculi, calculous, appendix
• Concretion, appendicular
• Fecalith (impaction), appendix
• Stercolith (impaction), appendix

Official Coding Guidelines

No excerpt in the ICD-10-CM Official Guidelines names this code specifically. Its chapter carries only this chapter-wide note:

Don’t confuse K38.1 with…

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

The codes most likely to be picked instead of K38.1 — 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.

• K38.9— 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 “Disease of appendix, unspecified” takes K38.9; specificity in the record moves it back here.

  Full comparison: K38.1 vs K38.9 →

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

• No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

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

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 393 (MDC 06), DRG 394 (MDC 06), DRG 395 (MDC 06).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

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, K35.89 — 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, K38.0 — Hyperplasia of appendix, 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

Same Index main term, other category

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

E79.82 — Hereditary xanthinuria (xanthine), H11.12 — Conjunctival concretions (conjunctiva), J34.89 — Other specified disorders of nose and nasal sinuses (nose), J35.8 — Other chronic diseases of tonsils and adenoids (tonsil), J98.09 — Other diseases of bronchus, not elsewhere classified (bronchus), J98.4 — Other disorders of lung (lung), K03.6 — Deposits [accretions] on teeth (dental), K11.5 — Sialolithiasis (salivary gland), K31.89 — Other diseases of stomach and duodenum (stomach), K56.41 — Fecal impaction, K56.49 — Other impaction of intestine (intestinal), K80.00 — Calculus of gallbladder with acute cholecystitis without obstruction (gallbladder, with, cholecystitis, acute), K80.01 — Calculus of gallbladder with acute cholecystitis with obstruction (gallbladder, with, cholecystitis, acute, with, obstruction), K80.10 — Calculus of gallbladder with chronic cholecystitis without obstruction (gallbladder, with, cholecystitis), K80.11 — Calculus of gallbladder with chronic cholecystitis with obstruction (gallbladder, with, cholecystitis, with obstruction), K80.12 — Calculus of gallbladder with acute and chronic cholecystitis without obstruction (gallbladder, with, cholecystitis, acute, with, chronic cholecystitis), K80.13 — Calculus of gallbladder with acute and chronic cholecystitis with obstruction (gallbladder, with, cholecystitis, chronic, with, acute cholecystitis, with obstruction), K80.18 — Calculus of gallbladder with other cholecystitis without obstruction (gallbladder, with, cholecystitis, specified NEC), K80.19 — Calculus of gallbladder with other cholecystitis with obstruction (gallbladder, with, cholecystitis, specified NEC, with obstruction), K80.20 — Calculus of gallbladder without cholecystitis without obstruction (gallbladder), +51 more

Contextual Map

Every relationship of K38.1 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.

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

Clinical classification (CCSR)

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

MS-DRG Grouper

• DRG 393 — OTHER DIGESTIVE SYSTEM DIAGNOSES WITH MCC[MS-DRG]: “OTHER DIGESTIVE SYSTEM DIAGNOSES WITH MCC (MDC 06)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 394 — OTHER DIGESTIVE SYSTEM DIAGNOSES WITH CC[MS-DRG]: “OTHER DIGESTIVE SYSTEM DIAGNOSES WITH CC (MDC 06)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 395 — OTHER DIGESTIVE SYSTEM DIAGNOSES WITHOUT CC/MCC[MS-DRG]: “OTHER DIGESTIVE SYSTEM DIAGNOSES WITHOUT CC/MCC (MDC 06)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 06 — Diseases and Disorders of the Digestive System[MDC crossing]: “Diseases and Disorders of the Digestive System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 5,744 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

• Calculus, calculi, calculous, appendix[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Concretion, appendicular[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Fecalith (impaction), appendix[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
• Stercolith (impaction), appendix[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

• K38 — Other diseases of appendix[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K38.0 — Hyperplasia of appendix[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K38.2 — Diverticulum of appendix[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K38.3 — Fistula of appendix[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K38.8 — Other specified diseases of appendix[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• K38.9 — Disease of appendix, unspecified[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Change history

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

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

Coding guidelines Official source data

ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section 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

Inpatient payment groups Official source data

CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 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 K38.1 in its code family, with their registry titles.

• K38 — Other diseases of appendix
• K38.0 — Hyperplasia of appendix
• K38.2 — Diverticulum of appendix
• K38.3 — Fistula of appendix
• K38.8 — Other specified diseases of appendix
• K38.9 — Disease of appendix, unspecified

View all codes in the K38 family