2027 ICD-10-CM Diagnosis Code A04.9Bacterial intestinal infection, unspecified
ICD-10-CM Codes›A00–B99›A00-A09›A04
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
A04.9 is a billable ICD-10-CM diagnosis code for bacterial intestinal infection, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 371 through 373. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 104 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Intestinal infection.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Bacterial dysentery
- Bacterial enteritis of intestine
- Bacterial gastroenteritis
- Bacterial gastrointestinal infectious disease
- Bacterial intestinal infectious disease
- Bacterial overgrowth syndrome
- Colitis caused by bacterium
- Dysenteric diarrhea
- Emphysematous gastritis
- Purulent enteritis
- Small bowel bacterial overgrowth syndrome
- Suppurative colitis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to A04.9: its own notes plus those printed at A04 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- diseases generally recognized as communicable or transmissible
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Bacterial enteritis NOS
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify resistance to antimicrobial drugs (Z16.-)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name A04.9, its category, or a range that includes it.
Excludes2 2
These codes carry an Excludes2 note naming A04.9: its condition is not part of those codes, and both may be reported when the patient has both.
- Block P35-P39 Infections specific to the perinatal period
- P37 Other congenital infectious and parasitic diseases
Code First 1
These codes say to code first a condition named in the note, and A04.9 is one of the conditions named.
- M49 Spondylopathies in diseases classified elsewhere
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Spondylitis (chronic) See Also: Spondylopathy, inflammatory;
enterobacteria See Also: subcategory M49.8; A04.9
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Bacterial Infections
Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.
The full article covers:
- What are bacteria?
- How do bacterial infections spread?
- What are the treatments for bacterial infections?
- Can bacterial infections be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert A04.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About A04.9Overview
What is the ICD-10 code for bacterial intestinal infection, unspecified?
The ICD-10-CM code for bacterial intestinal infection, unspecified is A04.9 (sometimes written as A049). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is A04.9 (Other bacterial intestinal infections) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report bacterial intestinal infection, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does A04.9 group to?
When bacterial intestinal infection, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 372, 371, 373, with relative weights from 0.6945 to 1.7087 depending on complications. Higher weights mean higher Medicare reimbursement.
Is A04.9 a CC or MCC?
CMS lists A04.9 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 104 closely related codes in its exclusion list.
Can A04.9 be reported with a code from A05?
Not as a rule. The Excludes1 note at A04, which applies to A04.9, lists "bacterial foodborne intoxications, NEC (A05.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
