2026 ICD-10-CM Diagnosis Code A18.39Retroperitoneal tuberculosis

ICD-10-CM Codes›A00–B99›A15-A19›A18

ICD-10-CM A18.39
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A18.39 is a billable ICD-10-CM diagnosis code for retroperitoneal tuberculosis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 371 through 373, 974 through 976. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Tuberculosis.

Code Identity

ICD-10-CM Code
A18.39
Billable Status
Yes — Valid for Submission
Code Describes
Retroperitoneal tuberculosis
Short Description
Retroperitoneal tuberculosis
Same as the full description in the CMS dataset.
Parent Code
A18.3
Tuberculosis of intestines, peritoneum and mesenteric glands

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA15-A19Tuberculosis
CategoryA18Tuberculosis of other organs
This CodeA18.39Retroperitoneal tuberculosis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Granulomatous peritonitis
  • Mesenteric lymphadenitis
  • Mycobacterial lymphadenitis
  • Retroperitoneal infection
  • Retroperitoneal lymphadenopathy
  • Serositis
  • Tuberculosis of intestines, peritoneum and mesenteric glands
  • Tuberculosis of retroperitoneal lymph nodes
  • Tuberculous adenitis
  • Tuberculous mesenteric adenitis
  • Tuberculous peritonitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Tuberculosis of mesenteric glands
  • Tuberculosis of retroperitoneal (lymph glands)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Lymphadenitis
      • mesenteric (acute) (chronic) (nonspecific) (subacute)
        • tuberculous
    • Tabes, tabetic
      • mesenterica
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • abdomen (lymph gland)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • lymph gland or node (peripheral)
        • abdomen
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • lymph gland or node (peripheral)
        • mesenteric
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • lymph gland or node (peripheral)
        • retroperitoneal
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • mesentery, mesenteric (gland or node)
    • Tuberculosis, tubercular, tuberculous(calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (degeneration) (fibrocaseous) (fistula) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative)
      • retroperitoneal (lymph gland or node)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF001
Tuberculosis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Serositis

    inflammation of a serous membrane.

  • Mesenteric Lymphadenitis

    inflammation of lymph nodes in the mesentery.

  • Mesenteric Lymphadenitis

    inflammation of the mesenteric lymph nodes.

Patient EducationClinical

Peritoneal Disorders

Your peritoneum is the tissue that lines your abdominal wall and covers most of the organs in your abdomen. A liquid, peritoneal fluid, lubricates the surface of this tissue.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A18.39 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
014.80 Intestinal TB NEC-unspec
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A18.39Overview

Is A18.39 (Tuberculosis of intestines, peritoneum and mesenteric glands) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report retroperitoneal tuberculosis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A18.39 group to?

When retroperitoneal tuberculosis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 371, 372, 373, 974, 975, 976, with relative weights from 0.7274 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A18.39?

Under the General Equivalence Mappings, retroperitoneal tuberculosis converts to ICD-9-CM 014.80 (intestinal TB NEC-unspec). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.