Infectious gastroenteritis and colitis, unspecified
In Intestinal infectious diseases (A00-A09), chapter 1: Certain Infectious and Parasitic Diseases
- A09 is an unspecified code: use it only when the record doesn't document anything more specific. If the record has more detail, check the other codes under A00-A09 below.
- As a secondary diagnosis it is a CC (complication or comorbidity), which can raise the MS-DRG payment. It doesn't count when the principal diagnosis is one of 81 closely related codes.
- Doesn't count toward a Medicare Advantage risk score (no HCC in V28).
- AHRQ's Chronic Condition Indicator classes it as not chronic (an acute or short-term condition).
- 3,008 US deaths in 2024 had an underlying cause in category A09, per the National Vital Statistics System on CDC WONDER. Death records use WHO ICD-10, so the count is for the whole category.
Also indexed as: Arthritis, in, enteritis, infectious NEC; Colitis, regional, infectious; Diarrhea, dysenteric; Diarrhea, endemic; Diarrhea, epidemic; Diarrhea, infectious; Disease, diarrheal, infectious NEC; Dysentery; Dysentery, arthritis; Enteritis, epidemic; Enteritis, infectious NOS; Enteritis, septic; Enterocolitis, infectious NEC; Gastroenteritis, epidemic; Gastroenteropathy, infectious; Ileitis, infectious; Ileocolitis, infectious; Sigmoiditis, infectious; Ulcer, dysenteric
Advertisements
Instructional notes
Includes: conditions that are coded here
- Infectious colitis NOS
- Infectious enteritis NOS
- Infectious gastroenteritis NOS
Official coding guidelines
From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.
Rules for coding infections and parasitic diseases, including HIV, organism and drug resistance codes, sepsis and septic shock, MRSA, Zika, and COVID-19.
- Human Immunodeficiency Virus (HIV) Infections (page 19)
- Infectious agents as the cause of diseases classified to other chapters (page 22)
- Infections resistant to antibiotics (page 22)
- Sepsis, Severe Sepsis, and Septic Shock (page 23)
- Methicillin Resistant Staphylococcus aureus (MRSA) Conditions (page 27)
- Zika virus infections (page 28)
- Coronavirus infections (page 28)
Other codes under A00-A09
Intestinal infectious diseases (A00-A09)
- A00Cholera
- A01Typhoid and paratyphoid fevers
- A02Other salmonella infections
- A03Shigellosis
- A04Other bacterial intestinal infections
- A05Other bacterial foodborne intoxications, not elsewhere classified
- A06Amebiasis
- A07Other protozoal intestinal diseases
- A08Viral and other specified intestinal infections
- A09Infectious gastroenteritis and colitis, unspecified(this code)
A09 MS-DRGs
As the principal diagnosis, A09 groups to MS-DRG 391 or 392 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.
Related conditions
Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.
A09 is in Intestinal infection (DIG001, its default category), with 56 codes. Others in it:
A09 is in Parasitic, other specified and unspecified infections (INF009), with 254 codes. Others in it:
Medicare coverage articles listing A09
These 6 Medicare billing and coding articles list A09 as a diagnosis that supports medical necessity for the services they cover. From the CMS Medicare Coverage Database; check your own contractor's article before billing.
- MolDX: Molecular Syndromic Panels for Infectious Disease Pathogen Identification Testing (4 contractors)
- Colonoscopy/Sigmoidoscopy/Proctosigmoidoscopy (2 contractors)
- Diagnostic Colonoscopy
- Colonoscopy and Sigmoidoscopy-Diagnostic
- Diagnostic Colonoscopy
- Multiplex Gastrointestinal Pathogen Panel (GPP) Tests for Acute Gastroenteritis (AGE)
Other codes that refer to A09
Notes on these codes point to A09.
About the condition
Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.
Gastroenteritis
Gastroenteritis is an inflammation of the lining of the stomach and intestines. The main symptoms include vomiting and diarrhea. It is usually not serious in healthy people, but it can sometimes lead to dehydration or cause severe symptoms.
Read more about gastroenteritis on MedlinePlusInfectious Diseases
Germs, or microbes, are found everywhere - in the air, soil, and water. There are also germs on your skin and in your body. Many of them are harmless, and some can even be helpful. But some of them can make you sick. Infectious diseases are diseases that are caused by germs.
Read more about infectious diseases on MedlinePlusCode history
Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.
ICD-9-CM equivalent
Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).
- 009.0 Infectious colitis, enteritis, and gastroenteritis (approximate)