ICD-10 Code I80.299 – Phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I80.299 – Phlebitis and thrombophlebitis of other deep vessels of unspecified lower extremity
What it is
This code identifies inflammation and clotting in a deep vein of the lower leg or thigh when the specific vessel is not named. Use it when documentation says deep venous thrombophlebitis of an unspecified lower extremity vein.
Clinical signs
Typical findings include unilateral leg pain, swelling, warmth, tenderness, and sometimes a palpable cord. Clinical features vary; refer to documentation and imaging or provider assessment when available.
When to use this code
Use I80.299 when the record documents phlebitis or thrombophlebitis in a deep vein of the lower extremity, but does not identify the exact vessel. It also fits when the site is described only as “other deep vessels” and laterality is unspecified. Check documentation if the note is unclear about superficial versus deep vein involvement.
Do not use for
Do not use this code for superficial thrombophlebitis or for deep vein thrombosis in a specified lower-extremity vein. If the provider names a different vein or laterality, select the more specific code.
Coding tip
Look for “deep” and “unspecified lower extremity” in the note before assigning I80.299.