ICD-10-CM Code A09

Infectious gastroenteritis and colitis, unspecified

Version 2020 Billable Code

Valid for Submission

A09 is a billable code used to specify a medical diagnosis of infectious gastroenteritis and colitis, unspecified. The code is valid for the year 2020 for the submission of HIPAA-covered transactions. The ICD-10-CM code A09 might also be used to specify conditions or terms like acute erosive gastritis, acute gastroenteritis, acute gastroenteritis, acute infectious nonbacterial gastroenteritis, acute infective gastroenteritis, acute ulcerative gastroenteritis complicating pneumonia, etc

Short Description:Infectious gastroenteritis and colitis, unspecified
Long Description:Infectious gastroenteritis and colitis, unspecified

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code A09:

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Infectious colitis NOS
  • Infectious enteritis NOS
  • Infectious gastroenteritis NOS

Type 1 Excludes

Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
  • colitis NOS K52.9
  • diarrhea NOS R19.7
  • enteritis NOS K52.9
  • gastroenteritis NOS K52.9
  • noninfective gastroenteritis and colitis, unspecified K52.9

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code A09 are found in the index:


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Acute erosive gastritis
  • Acute gastroenteritis
  • Acute gastroenteritis
  • Acute infectious nonbacterial gastroenteritis
  • Acute infective gastroenteritis
  • Acute ulcerative gastroenteritis complicating pneumonia
  • Catarrhal dysentery
  • Colitis presumed infectious
  • Colitis, enteritis and gastroenteritis presumed infectious
  • Diarrhea of presumed infectious origin
  • Disease of presumed infectious origin
  • Disease of presumed infectious origin
  • Disease of presumed infectious origin
  • Disease of presumed infectious origin
  • Disorder of gastrointestinal tract co-occurrent with human immunodeficiency virus infection
  • Dysenteric diarrhea
  • Enteritis presumed infectious
  • Epidemic diarrhea
  • Epidemic gastroenteritis
  • Erosive gastritis
  • Fungal gastrointestinal infection
  • Gastroenteritis presumed infectious
  • Gastrointestinal infection
  • Ill-defined infectious disease
  • Ill-defined infectious disease
  • Ill-defined intestinal infection
  • Ill-defined intestinal infection
  • Ill-defined intestinal infection associated with AIDS
  • Infection of digestive system
  • Infection of large intestine
  • Infectious colitis
  • Infectious diarrheal disease
  • Infectious disease of digestive tract
  • Infectious enteritis
  • Infectious gastroenteritis
  • Infectious gastroenteritis associated with AIDS
  • Infectious gastroenteritis co-occurrent with human immunodeficiency virus infection
  • Infective gastritis
  • Institution-acquired gastroenteritis
  • Institutional environment related disease
  • Intestinal infectious disease
  • Megacolon co-occurrent and due to infectious colitis
  • Megacolon, not Hirschsprung's
  • Phlegmonous enteritis
  • Pseudo-obstruction of colon
  • Purulent enteritis
  • Secondary megacolon - acquired
  • Suppurative gastritis
  • Toddler diarrhea

Diagnostic Related Groups

The ICD-10 code A09 is grouped in the following groups for version MS-DRG V37.0 What are Diagnostic Related Groups?
The Diagnostic Related Groups (DRGs) are a patient classification scheme which provides a means of relating the type of patients a hospital treats. The DRGs divides all possible principal diagnoses into mutually exclusive principal diagnosis areas referred to as Major Diagnostic Categories (MDC).
applicable from 10/01/2019 through 09/30/2020.


Convert A09 to ICD-9

  • 009.0 - Infectious enteritis NOS (Approximate Flag)

Code Classification

  • Certain infectious and parasitic diseases (A00–B99)
    • Intestinal infectious diseases (A00-A09)
      • Infectious gastroenteritis and colitis, unspecified (A09)

Code History

  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016
    (First year ICD-10-CM implemented into the HIPAA code set)
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

Information for Patients


Have you ever had the "stomach flu?" What you probably had was gastroenteritis - not a type of flu at all. Gastroenteritis is an inflammation of the lining of the intestines caused by a virus, bacteria, or parasites. Viral gastroenteritis is the second most common illness in the U.S. The cause is often a norovirus infection. It spreads through contaminated food or water or by contact with an infected person. The best prevention is frequent hand washing.

Symptoms of gastroenteritis include diarrhea, abdominal pain, vomiting, headache, fever, and chills. Most people recover with no treatment.

The most common problem with gastroenteritis is dehydration. This happens if you do not drink enough fluids to replace what you lose through vomiting and diarrhea. Dehydration is most common in babies, young children, older adults, and people with weak immune systems.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

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Infectious 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.

There are many different ways that you can get an infectious disease:

  • Through direct contact with a person who is sick. This includes kissing, touching, sneezing, coughing, and sexual contact. Pregnant mothers can also pass some germs along to their babies.
  • Through indirect contact, when you touch something that has germs on it. For example, you could get germs if someone who is sick touched a door handle, and then you touch it.
  • Through insect or animal bites
  • Through contaminated food, water, soil, or plants

There are four main kinds of germs:

  • Bacteria - one-celled germs that multiply quickly. They may give off toxins, which are harmful chemicals that can make you sick. Strep throat and urinary tract infections are common bacterial infections.
  • Viruses - tiny capsules that contain genetic material. They invade your cells so that they can multiply. This can kill, damage, or change the cells and make you sick. Viral infections include HIV/AIDS and the common cold.
  • Fungi - primitive plant-like organisms such as mushrooms, mold, mildew, and yeasts. Athlete's foot is a common fungal infection.
  • Parasites - animals or plants that survive by living on or in other living things. Malaria is an infection caused by a parasite.

Infectious diseases can cause many different symptoms. Some are so mild that you may not even notice any symptoms, while others can be life-threatening. There are treatments for some infectious diseases, but for others, such as some viruses, you can only treat your symptoms. You can take steps to prevent many infectious diseases:

  • Get vaccinated
  • Wash your hands often
  • Pay attention to food safety
  • Avoid contact with wild animals
  • Practice safe sex
  • Don't share items such as toothbrushes, combs, and straws

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