2026 ICD-10-CM Diagnosis Code I81Portal vein thrombosis
ICD-10-CM Codes›I00–I99›I80-I89›I81
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Not Chronic
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. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 202 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acute phlebitis; thrombophlebitis and thromboembolism.
Code Identity
Code Classification
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
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Pseudoangioma I81
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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.
Code HistoryHistory
Questions About I81Overview
What is the ICD-10 code for portal vein thrombosis?
The ICD-10-CM code for portal vein thrombosis is I81. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
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.
Is I81 a CC or MCC?
CMS lists I81 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 202 closely related codes in its exclusion list.
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.
