Hematoma formation: This is a common complication following an angiogram, especially if the access site was not properly sealed or if the patient has a bleeding tendency. The swelling and pain could be due to a collection of blood outside the blood vessels.

Pseudoaneurysm formation: A possible complication of arterial puncture during the angiogram, where a false aneurysm forms at the site of the puncture, leading to swelling and pain.
Arteriovenous fistula (AVF): An abnormal connection between an artery and a vein that can occur as a complication of the angiogram, potentially causing swelling and pain due to altered blood flow.
Thrombophlebitis: Inflammation of the veins due to a blood clot, which can occur after an angiogram, especially if the catheter irritated the vein walls.

Compartment syndrome: A serious condition where increased pressure within a muscle compartment leads to inadequate blood supply to the tissues, which can result from severe swelling or hematoma. It's crucial to identify and treat promptly to avoid permanent damage.
Infection (e.g., abscess or cellulitis): Although less common, infection at the site of the angiogram can cause swelling and pain and needs to be considered, especially if there are signs of fever or purulent discharge.

Nerve injury: Direct trauma to nerves during the procedure can lead to pain and swelling, although this is less common.
Allergic reaction to contrast media: While rare, an allergic reaction to the contrast dye used during the angiogram could potentially cause swelling and pain, among other symptoms.
Vasculitis: Inflammation of the blood vessels, which could be a reaction to the procedure or the materials used, is a rare but possible cause of swelling and pain.