Phlebitis is a medical term that refers to inflammation of a vein. It can occur in both superficial (near the skin) and deep (within the muscle) veins. 

Causes: 

• Blood clots (thrombosis)
• Injury to the vein
• Infection
• Varicose veins
• Certain medications
• Autoimmune disorders

Symptoms: 

• Redness and swelling of the affected vein
• Pain, tenderness, or warmth
• Hardened or cord-like feeling vein
• Possible fever or chills if there is an infection

Treatment:

Treatment depends on the underlying cause and severity of the phlebitis. It may include: 

• Anticoagulant medications (blood thinners)
• Antibiotics if there is an infection
• Compression stockings
• Elevation of the affected leg
• In some cases, surgery may be necessary to remove a blood clot or damaged vein

Complications: 

If left untreated, phlebitis can lead to complications such as: Deep vein thrombosis (DVT), Pulmonary embolism (a blood clot in the lungs), and Infection.