BACKGROUND Adventitial cystic disease of the popliteal artery (PA) is an uncommon and unique entity characterized by a mucinous cyst located in the arterial adventitia. As the cyst enlarges, it provokes vascular compression with stenosis or occlusion, the first only during the knee flexion, and then in all leg position. Atkins and Key (1946) were the first who described this disease in the external iliac artery [1]. Eirup and Hiertonn (1956) described the disease in the PA, which is the place of its most common localization. The aim of the paper is the presentation of our 10 cases of PA adventitial cystic disease. METHODS Ten patients with PA adventitial cyst were treated at the Institute of Cardiovascular Diseases of the Serbian Clinical Centre in Belgrade, over the period between 1978 and 1997. There were 9 males and one female patient, average age 42.7 years (31-62). Two patients were smokers, while all other atherosclerotic risk factors, including heart disease, were absent. The diagnosis was established using Doppler ultrasonography and angiography. The postoperative histological examination revealed PA adventitial cyst in all patients (Figure 1). In Table 1 are presented our patients. The patients 3 and 4 were admitted for acute ischaemia of the leg. In patient 3 Doppler indexes were 0.0, and transfemoral arteriography revealed segmental occlusion of the PA. All other arteries were unchanged. These findings suggested an unusual disease of the PA. During the operation the posterior approach to the PA was used, and intraoperatively the adventitial cyst was found. In patient 4 the tibioperoneal trunk, posterior tibial artery and PA were occluded. Therefore, the medial approach to the PA was used. After thrombectomy of the crural vessels, the popliteo-popliteal bypass procedure was performed. The PA resection by this approach was not possible. The ringed 6 mm PTFE graft was used for reconstruction because of inadequate saphenous vein. The patients 1, 2, 5-10 were admitted with disabling claudication discomforts. In patients 1, 2, 5, 6, 8, 9 popliteal and pedal pulses were absent, and Doppler indexes decreased. In patients 7 and 10 pedal pulses were palpable and decreased during the normal knee position, while absent during the knee flexion. During some maneuvers Doppler indexes significantly decreased. Transfemoral arteriography in patients 1, 2, 5, 6, 8, 9 showed segmental stenosis or occlusion of the PA, and for this reason the posterior approach to the PA was used. The PA adventitial cyst was found in all cases (Figure 2). In patient 7 angiography revealed a "hourglass" deformity of the PA, while in patient 10 "scimitar" sign was found. Both angiographic findings are characteristic of PA adventitial cyst. The posterior approach was carried out in all patients. In patient 2 only cyst aspiration has been performed, while in patients 7, 8, 9 aspiration and resection of the changed PA adventitia (Figure 3a, figure 3b). In patients 1, 3, 5, 6, 10 an occluded arterial segment was resected. The restoration of the flow observed after the end-to-end anastomosis in patient 1, and after interposition of the saphenous graft in other patients. After the operation, the contralateral leg was examined using Doppler ultrasonography in all patients. The Doppler indexes were significantly decreased in patients 1 and 5 during the knee flexion, but the patients refused the angiographic examination. The control examination consisted of physical examination, Doppler ultrasonography and sometimes angiography; it was carried out after 1, 3, 6 and 12 months, and then every year after the operation. RESULTS There was no mortality among our patients in the early post-operative period. In patients in whom cyst aspiration was performed, claudication discomfort was decreased, and Doppler indexes were significantly increased. In patients with arterial resection and reconstruction (1, 3, 4, 5, 6, 10) the effect of the operation was simi