DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

A09 diagnosis code · Billable category · FY2027

A09 Infectious gastroenteritis and colitis, unspecified

  • Billable
  • CC
  • POA reported

A09 ICD-10 code: a billable diagnosis code in FY2027; the category has no subdivisions.

Where it sits

  1. Chapter 1 Certain infectious and parasitic diseases (A00-B99)
  2. A00-A09 Intestinal infectious diseases (A00-A09)
  3. A09 Infectious gastroenteritis and colitis, unspecified
CC / MCC
CC
MS-DRG
391-392
HCC V28
–
POA
Reported
Code Editor
–
Index entries
19

Instructions

At A09

Inclusion terms

  • Infectious colitis NOS
  • Infectious enteritis NOS
  • Infectious gastroenteritis NOS

Excludes1

  • colitis NOS (K52.9) K52.9
  • diarrhea NOS (R19.7) R19.7
  • enteritis NOS (K52.9) K52.9
  • gastroenteritis NOS (K52.9) K52.9
  • noninfective gastroenteritis and colitis, unspecified (K52.9) K52.9

Notes that also apply

Chapter 1 instructions (Includes 1, Excludes2 5, Use additional code 1): printed on the chapter 1 page.

Index entries

  • Dysentery, dysenteric (catarrhal) (diarrhea) (epidemic) (hemorrhagic) (infectious) (sporadic) (tropical) → A09
  • Diarrhea, diarrheal (disease) (infantile) (inflammatory)dysenteric → A09
  • Diarrhea, diarrheal (disease) (infantile) (inflammatory)endemic → A09
  • Diarrhea, diarrheal (disease) (infantile) (inflammatory)epidemic → A09
  • Diarrhea, diarrheal (disease) (infantile) (inflammatory)infectious → A09
  • Disease, diseaseddiarrheal, infectious NEC → A09
  • Dysentery, dysenteric (catarrhal) (diarrhea) (epidemic) (hemorrhagic) (infectious) (sporadic) (tropical)arthritis → A09
  • Enteritis (acute) (diarrheal) (hemorrhagic) (noninfective)epidemic (infectious) → A09
  • Enteritis (acute) (diarrheal) (hemorrhagic) (noninfective)infectious NOS → A09
  • Enteritis (acute) (diarrheal) (hemorrhagic) (noninfective)septic → A09
  • Enterocolitisinfectious NEC → A09
  • Gastroenteritis (acute) (chronic) (noninfectious)epidemic (infectious) → A09
  • Gastroenteropathyinfectious → A09
  • Ileitis (chronic) (noninfectious)infectious → A09
  • Ileocolitisinfectious → A09
  • Sigmoiditisinfectious → A09
  • Ulcer, ulcerated, ulcerating, ulceration, ulcerativedysenteric → A09
  • Arthritis, arthritic (acute) (chronic) (nonpyogenic) (subacute)in (due to)enteritis, infectious NEC → A09
  • Colitis (acute) (catarrhal) (chronic) (noninfective) (hemorrhagic)regionalinfectious → A09

NCHS Alphabetic Index. Index first, then the Tabular List.

Medicare grouping and edits

CMS files for A09
CC / MCCCC
PDX exclusion list0017 (81 codes)
Appendix BMDC 06 Diseases and Disorders of the Digestive System, MS-DRG 391-392 (Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders with MCC…)
Code Editor–
POAReported
HCC V28–

CC as a secondary diagnosis, not when the principal diagnosis is on its PDX exclusion list.

CMS: MS-DRG v44 (Appendix B, C), MCE v44, POA list FY2027, 2027 Initial ICD-10-CM Mappings. What the rows mean.

Hierarchy