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K59.31 ICD-10-CM Code: Toxic megacolon

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
7 Excludes1 · 1 Excludes2 · 1 code-first instruction
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 33

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 393 — OTHER DIGESTIVE SYSTEM DIAGNOSES WITH MCC (MDC 06)
  • MS-DRG 394 — OTHER DIGESTIVE SYSTEM DIAGNOSES WITH CC (MDC 06)
  • MS-DRG 395 — OTHER DIGESTIVE SYSTEM DIAGNOSES WITHOUT CC/MCC (MDC 06)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 78 — Intestinal Obstruction/Perforation

Other models: CMS-HCC V22 HCC 33

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for K59.31 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 K59.31 itself; “inherited from” names the category or block whose note applies here.

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from K59

Code First

Underlying conditions that must be sequenced before this code.

  • Code first, if applicable (T51-T65) to identify toxic agent

Source: inherited from K59.3

Coder workflow for K59.31

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

Before you code K59.31

  1. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with K59.31. 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 a condition named in K59.31’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.

    ReviewQ43.1, B57.32, A04.7, R19.4, K90, F45.8

  2. Is the underlying (etiologic) condition the Code First note names documented?
    Yes → Sequence the underlying condition first, then K59.31.
    No → Continue; do not add an underlying condition the record does not document.

Consider K59.31. 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).
The underlying (etiologic) condition
Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).

Official instructions as workflow

  • Excludes1 — check before selecting K59.31(7 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with K59.31: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareQ43.1, B57.32, A04.7, R19.4, K90, F45.8

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

  • Excludes2 — not part of K59.31(1 note)

    Coding workflow: The conditions named in this note are not included in K59.31. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareK31

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

  • Code First — sequencing check(1 note)

    Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before K59.31. Do not add an underlying condition the record does not document.

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

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

Documentation: Both the condition K59.31 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewQ43.1, B57.32, A04.7, R19.4, K90, F45.8

Documentation: The underlying condition the Code First note names is documented alongside this condition.

Coding question: How are the two sequenced?

Path: Review the Code First note.

Reason: The underlying condition is sequenced first and the manifestation follows (Guidelines I.A.13).

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.

Code Overview

Toxic megacolon is a billable ICD-10-CM diagnosis code (K59.31).

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

Indexed Clinical Terms (2)

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.

Official Coding Guidelines

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

Chapter 11: Diseases of the Digestive System (K00-K95)

Reserved for future guideline expansion

Decision Points

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

  1. Sequencing: 1 Code First instruction — the underlying condition is sequenced before this code when present. See the Code First notes
  2. 7 Excludes1 entries — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
  3. 1 Excludes2 entry — 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

  • CC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

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 K59.31 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 4 Excludes1 notes: K50 — Crohn's disease [regional enteritis] (via K59.3.-), K50-K52 — Noninfective enteritis and colitis (K50-K52) (via K59.3.-), K51 — Ulcerative colitis (via K59.3.-), K52 — Other and unspecified noninfective gastroenteritis and colitis (via K59.3.-).

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

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: CC — Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 15 clinically related codes on its CMS exclusion list.

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):DIG025 — Other specified and unspecified gastrointestinal disorders (default); INJ030 — Drug induced or toxic related condition.

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 process (MS-DRG)

Acts as CC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

K58.0 — Irritable bowel syndrome with diarrhea, K58.1 — Irritable bowel syndrome with constipation, K58.2 — Mixed irritable bowel syndrome, K58.8 — Other irritable bowel syndrome, K58.9 — Irritable bowel syndrome, unspecified, K59.1 — Functional diarrhea, K59.2 — Neurogenic bowel, not elsewhere classified, K59.39 — Other megacolon, K59.4 — Anal spasm, K59.81 — Ogilvie syndrome, K59.89 — Other specified functional intestinal disorders, K59.9 — Functional intestinal disorder, unspecified, K91.0 — Vomiting following gastrointestinal surgery, K91.1 — Postgastric surgery syndromes

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Intestinal Obstruction/Perforation) for risk-adjusted payment.

K56.50 — Intestinal adhesions [bands], unspecified as to partial versus complete obstruction, K56.51 — Intestinal adhesions [bands], with partial obstruction, K56.52 — Intestinal adhesions [bands] with complete obstruction, K56.600 — Partial intestinal obstruction, unspecified as to cause, K56.601 — Complete intestinal obstruction, unspecified as to cause, K56.609 — Unspecified intestinal obstruction, unspecified as to partial versus complete obstruction, K56.690 — Other partial intestinal obstruction, K56.691 — Other complete intestinal obstruction, K56.699 — Other intestinal obstruction unspecified as to partial versus complete obstruction, K56.7 — Ileus, unspecified, K63.1 — Perforation of intestine (nontraumatic), K65.0 — Generalized (acute) peritonitis, K65.1 — Peritoneal abscess, K65.2 — Spontaneous bacterial peritonitis, K65.3 — Choleperitonitis, K65.4 — Sclerosing mesenteritis, K65.8 — Other peritonitis, K65.9 — Peritonitis, unspecified, K67 — Disorders of peritoneum in infectious diseases classified elsewhere, K68.12 — Psoas muscle abscess, +55 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Intestine Transplant Status/Complications

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical categories (Other specified and unspecified gastrointestinal disorders, Drug induced or toxic related condition).

K58.9 — Irritable bowel syndrome, unspecified, K59.00 — Constipation, unspecified, K59.01 — Slow transit constipation, K59.02 — Outlet dysfunction constipation, K59.03 — Drug induced constipation, K59.04 — Chronic idiopathic constipation, K59.09 — Other constipation, K59.1 — Functional diarrhea, K59.2 — Neurogenic bowel, not elsewhere classified, K59.3 — Megacolon, not elsewhere classified, K59.39 — Other megacolon, K59.8 — Other specified functional intestinal disorders, K59.81 — Ogilvie syndrome, K59.89 — Other specified functional intestinal disorders, K59.9 — Functional intestinal disorder, unspecified, K63.2 — Fistula of intestine, K63.3 — Ulcer of intestine, K63.4 — Enteroptosis, K63.81 — Dieulafoy lesion of intestine, K63.8211 — Small intestinal bacterial overgrowth, hydrogen-subtype, +310 more

Same Index main term, other category

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

I99.8 — Other disorder of circulatory system (blood vessel), J39.2 — Other diseases of pharynx (pharynx), J47.0 — Bronchiectasis with acute lower respiratory infection (bronchial, with, lower respiratory infection), J47.1 — Bronchiectasis with (acute) exacerbation (bronchial, with, exacerbation), J47.9 — Bronchiectasis, uncomplicated (bronchial), K11.8 — Other diseases of salivary glands (salivary gland), K22.0 — Achalasia of cardia (esophagus, due to achalasia), K22.89 — Other specified disease of esophagus (esophagus), K31.0 — Acute dilatation of stomach (stomach, acute), K31.89 — Other diseases of stomach and duodenum (stomach), K62.89 — Other specified diseases of anus and rectum (sphincter ani), K82.8 — Other specified diseases of gallbladder (gallbladder), K83.8 — Other specified diseases of biliary tract (common duct), K86.89 — Other specified diseases of pancreas (pancreatic duct), N13.4 — Hydroureter (ureter, due to obstruction), N28.82 — Megaloureter (ureter), N28.89 — Other specified disorders of kidney and ureter (calyx), N32.89 — Other specified disorders of bladder (bladder), N36.8 — Other specified disorders of urethra (urethra), N42.89 — Other specified disorders of prostate (prostate), +25 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Blood Glucose Test, Fecal Occult Blood Test (FOBT), Gamma-glutamyl Transferase (GGT) Test, Partial Thromboplastin Time (PTT) Test, Prothrombin Time Test and INR (PT/INR)

Contextual Map

Every relationship of K59.31 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 K59.31 with these 4 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 78 — Intestinal Obstruction/Perforation [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

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

  • Dilatation, colon, toxic[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Megacolon (acquired) (functional) (not Hirschsprung's disease) (in), toxic NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (17)

Change history

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
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release 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

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. "K59.31 — Toxic megacolon." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/k59.31-toxic-megacolon

Change history

  • FY2017 — October 1, 2016
    Added to the code set
    Toxic megacolon
    FY2017 changes

Nearest Codes in This Family

Official ICD-10-CM classifications closest to K59.31 in its code family, with their registry titles.

View all codes in the K59 family