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ICD-10-CM 2027 diagnosis code

K31.1Adult hypertrophic pyloric stenosis

✓ Billable / specificCC — complication/comorbidityAdult · age 15–124

K31.1 is a valid, billable ICD-10-CM code for adult hypertrophic pyloric stenosis. 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 Pylorus stenosis, ICD-10 code for Pylorus constriction, ICD-10 code for Pylorus hypertrophic stricture.

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 K31.1

K31.1 is the ICD-10-CM diagnosis code for adult hypertrophic pyloric stenosis. 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), K31.1 is specifically for adult hypertrophic pyloric stenosis. Related codes cover acute dilatation of stomach (K31.0), Hourglass stricture and stenosis of stomach (K31.2), Pylorospasm, not elsewhere classified (K31.3), gastric diverticulum (K31.4), obstruction of duodenum (K31.5), fistula of stomach and duodenum (K31.6), polyp of stomach and duodenum (K31.7), other specified diseases of stomach and duodenum (K31.8) and 3 more.

Don't report K31.1 together with the conditions in its Excludes1 note: congenital pyloric stenosis (Q40.0).

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 380 (Complicated Peptic Ulcer with MCC, relative weight 1.9245), DRG 381 (Complicated Peptic Ulcer with CC, relative weight 1.0838) and DRG 382 (Complicated Peptic Ulcer without CC/MCC, relative weight 0.7281), 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.

The Medicare Code Editor expects this diagnosis only for patients age 15 through 124.

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 537.0 (acquired hypertrophic pyloric stenosis).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Acquired hypertrophic pyloric stenosis
  • Adult pyloric stenosis
  • Pyloric stenosis NOS
Excludes1Not coded here — never report together with this code
  • congenital pyloric stenosis (Q40.0)

Notes that apply from higher levels

Instructions written at a parent level also apply to K31.1.

› 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

9 entries

Terms in the official ICD-10-CM index that lead to K31.1.

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 →
  • 537.0Acquired hypertrophic pyloric stenosisexact

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 K31.1

Is K31.1 billable?

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

Can K31.1 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict K31.1 as a principal diagnosis.

Is K31.1 a CC or MCC?

K31.1 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does K31.1 group to?

K31.1 is used in the MS-DRG v44.0 logic for MS-DRG 380 (Complicated Peptic Ulcer with MCC), MS-DRG 381 (Complicated Peptic Ulcer with CC) and MS-DRG 382 (Complicated Peptic Ulcer without CC/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 K31.1?

The CMS General Equivalence Mappings map K31.1 to ICD-9-CM 537.0.