Final answer:
Sclerotherapy (option 3) is the procedure used to treat varicose veins by injecting a chemical irritant into the vein, causing it to collapse and be reabsorbed into the body.
Step-by-step explanation:
The procedure that involves the injection of a chemical irritant into a vein to treat varicose veins is known as sclerotherapy. This minimally invasive treatment can make varicose veins shrink. During sclerotherapy, a solution is injected into the affected veins, causing them to scar and forcing blood to reroute through healthier veins. The collapsed vein is eventually reabsorbed into local tissue and fades over time. It is different from chemotherapy, which involves the use of chemicals to kill cancer cells, or radiotherapy, which uses radiation to target cancerous tissue.
For less serious cases, conservative management such as wearing compression stockings and leg elevation might be recommended. But for more serious cases, besides sclerotherapy, other non-surgical options include endovenous thermal ablation. Surgical interventions might be considered for the most severe cases, potentially involving vein stripping or ambulatory phlebectomy.