Subclavian vein obstruction without thrombosis. 
Unilateral arm swelling caused by subclavian vein obstruction without thrombosis is an uncommon form of venous thoracic outlet syndrome (TOS).  In 87 patients with venous TOS, only 21 patients had no thrombosis.  We describe the diagnosis and treatment of these patients.  Twenty-one patients with arm swelling, cyanosis, and venograms demonstrating partial subclavian vein obstruction were treated with transaxillary first rib resection and venolysis.  Eighteen (86%) of 21 patients had good-to-excellent improvement of symptoms.  There were two failures (9%).  Unilateral arm swelling without thrombosis, when not caused by lymphatic obstruction, may be due to subclavian vein compression at the costoclavicular ligament because of compression either by that ligament or the subclavius tendon most often because of congenital close proximity of the vein to the ligament.  Arm symptoms of neurogenic TOS, pain, and paresthesia often accompany venous TOS while neck pain and headache, other common symptoms of neurogenic TOS, are infrequent.  Diagnosis was made by dynamic venography.  First rib resection, which included the anterior portion of rib and cartilage plus division of the costoclavicular ligament and subclavius tendon, proved to be effective treatment.