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ICD-10-CM 2027 diagnosis code

K31.6Fistula of stomach and duodenum

✓ Billable / specificCC — complication/comorbidity

K31.6 is a valid, billable ICD-10-CM code for fistula of stomach and duodenum. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Gastrocolic fistula.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About K31.6

K31.6 is the ICD-10-CM diagnosis code for fistula of stomach and duodenum. It belongs to category K31 (other diseases of stomach and duodenum), block K20-K31 (diseases of esophagus, stomach and duodenum) and chapter 11 (diseases of the digestive system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within K31 (other diseases of stomach and duodenum), K31.6 is specifically for fistula of stomach and duodenum. Related codes cover acute dilatation of stomach (K31.0), adult hypertrophic pyloric stenosis (K31.1), Hourglass stricture and stenosis of stomach (K31.2), Pylorospasm, not elsewhere classified (K31.3), gastric diverticulum (K31.4), obstruction of duodenum (K31.5), polyp of stomach and duodenum (K31.7), other specified diseases of stomach and duodenum (K31.8) and 3 more.

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 391 (Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders with MCC, relative weight 1.2392) and DRG 392 (Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders without MCC, relative weight 0.7645), in MDC 06 (Diseases and Disorders of the Digestive System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 537.4 (fistula of stomach or duodenum).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Gastrocolic fistula
  • Gastrojejunocolic fistula
Code alsoTwo codes may be needed; sequencing depends on circumstances
  • , if applicable, disruption of internal operation (surgical) wound (T81.32-)

Notes that apply from higher levels

Instructions written at a parent level also apply to K31.6.

› From K31 Other diseases of stomach and duodenum
Includes
  • functional disorders of stomach
Excludes2

Broader instructions also apply from K20-K31 Diseases of esophagus, stomach and duodenum and Chapter 11: Diseases of the digestive system.

Alphabetic index entries

8 entries

Terms in the official ICD-10-CM index that lead to K31.6.

Codes whose notes reference K31.6

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 537.4Fistula of stomach or duodenumexact

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about K31.6

Is K31.6 billable?

Yes. K31.6 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can K31.6 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict K31.6 as a principal diagnosis.

Is K31.6 a CC or MCC?

K31.6 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does K31.6 group to?

K31.6 is used in the MS-DRG v44.0 logic for MS-DRG 391 (Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders with MCC) and MS-DRG 392 (Esophagitis, Gastroenteritis and Miscellaneous Digestive Disorders without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for K31.6?

The CMS General Equivalence Mappings map K31.6 to ICD-9-CM 537.4.