2026 ICD-10-CM Diagnosis Code I81Portal vein thrombosis

ICD-10-CM Codes›I00–I99›I80-I89›I81

ICD-10-CM I81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I81 is a billable ICD-10-CM diagnosis code for portal vein thrombosis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 441 through 443. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acute phlebitis; thrombophlebitis and thromboembolism.

Code Identity

ICD-10-CM Code
I81
Billable Status
Yes — Valid for Submission
Code Describes
Portal vein thrombosis
Chapter
I80-I89
Diseases of veins, lymphatic vessels and lymph nodes, not elsewhere classified

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI80-I89Diseases of veins, lymphatic vessels and lymph nodes, not elsewhere classified
CategoryI81Portal vein thrombosis
This CodeI81Portal vein thrombosis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute GIT vascular insufficiency
  • Acute ischemia of colon due to thrombosis of mesenteric vein
  • Acute occlusion of mesenteric vein
  • Acute thrombosis of mesenteric vein
  • Acute vascular insufficiency of intestine
  • Acute visceral ischemia
  • Chronic thrombosis of mesenteric vein
  • Obstruction of visceral vein
  • Portal vein obstruction
  • Portal vein thrombosis
  • Thrombosis of mesenteric vein
  • Visceral ischemia

Tabular List NotesGuidance

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

Inclusion Terms

  • Portal (vein) obstruction

Type 2 Excludes

  • hepatic vein thrombosis I82.0
  • phlebitis of portal vein K75.1

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.

    • Block, blocked
      • portal (vein)
    • Embolism(multiple) (paradoxical)
      • portal (vein)
    • Obstruction, obstructed, obstructive
      • portal (circulation) (vein)
    • Pseudoangioma
    • Thrombosis, thrombotic(bland) (multiple) (progressive) (silent) (vessel)
      • liver (venous)
        • portal vein
    • Thrombosis, thrombotic(bland) (multiple) (progressive) (silent) (vessel)
      • portal

Clinical ClassificationClinical

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

CCSR CIR033
Acute phlebitis; thrombophlebitis and thromboembolism
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Deep Vein Thrombosis

Deep vein thrombosis, or DVT, is a blood clot that forms in a vein deep in the body. Most deep vein clots occur in the lower leg or thigh. If the vein swells, the condition is called thrombophlebitis. A deep vein thrombosis can break loose and cause a serious problem in the lung, called a pulmonary embolism.

Read the full article at MedlinePlus

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

Convert I81 to ICD-9-CMHistory

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

ICD-9-CM
452 Portal vein thrombosis
Exact Match The mapping is direct, with no qualifiers.

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 I81Overview

Is I81 (Portal vein thrombosis) a billable code?

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

What MS-DRG does I81 group to?

When portal vein thrombosis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 441, 442, 443, with relative weights from 0.6997 to 1.7947 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of I81?

Under the General Equivalence Mappings, portal vein thrombosis converts to ICD-9-CM 452 (portal vein thrombosis). The mapping is a direct match.

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.