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Background: Venous aneurysms are long-term complications of arteriovenous fistula (AVF) for hemodialysis with an estimated incidence rate of around 5-6%. The purpose of our study is to investigate the role of immunosuppressive therapy in the development of AVF aneurysms in renal transplant patients, and to determine whether AVF closure following transplantation is necessary., Methods: Forty-six patients with symptomatic venous AVF aneurysms underwent ligation and resection of their fistulas between January 2013 and January 2020. Immunohistochemical expression of CD3, CD4, and CD8 was assessed on the surgical specimens to characterize lymphocytic infiltrate in the aneurysm wall. Patients were subdivided into "Group A"-kidney transplant patients undergoing immunosuppressive therapy which was comprised of 39 patients and "Group B"-patients who had not undergone kidney transplant which was comprised of 7 patients. The 2 groups did not significantly differ in age, sex nor risk factors for aneurysms., Results: Group A showed a significantly higher aneurysm diameter (P < 0.0001), mean flow (P < 0.0001) and required a longer duration of surgery (P = 0.0007). A CD3+ lymphocytic infiltrate was significantly more common in Group A than in the Group B (90% vs 29%; P < 0.001). No significant differences in localization (adventitia, media or intima) and type (CD4+ vs CD8+) of lymphocytes were found between the 2 groups., Conclusion: AVF venous aneurysms were significantly larger and with a more intense T-lymphocytic infiltrate in patients undergoing immunosuppressive therapy. This finding suggests that immunosuppressive therapy plays a role in aneurysm formation, supporting the need for AVF closure in patients with an estimated low risk of rejection., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Vein aneurysms represent a rare clinical entity with a wide range of clinical symptoms. We present a case of a 67-year-old male who presented with a large, bluish, easily compressible, soft tissue mass in the lateral side of his forearm, which was mildly tender and it had been worsening during the last year. A color duplex ultrasound revealed local venous dilatation of the cephalic vein, measuring 6.3 × 3.2 cm. The patient was operated under local anesthesia and the lesion was removed. Histology showed thinning of the inner and middle layers of the cephalic vein and incipient replacement of the outer layer by acellular fibrous tissue with progressive decrease of elastic, smooth muscle and collagen fibers of the inner and middle layers, compatible with an aneurysm of the cephalic vein. Large cephalic vein aneurysms might cause nerve compression and require surgical removal before permanent neurological defect occurs., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Hepatic artery aneurysm is rare, but appropriate treatment is mandatory. We report a 50-year-old woman with an asymptomatic large hepatic artery aneurysm. The aneurysm was found as a result of abdominal computed tomography (CT) performed as a part of the screening. An open surgery was performed due to the size of the aneurysm. Aneurysmectomy was achieved, and the proper hepatic artery was anastomosed with gastroduodenal artery for adequate blood flow to the liver. Adequate hepatic circulation was confirmed postoperatively by duplex ultrasonography and CT. The patient was discharged on the 9th postoperative day., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Subclavian artery aneurysms (SAAs) are rare and even more uncommon in patients with fibromuscular dysplasia (FMD). A 20-year-old man with a past medical history of moyamoya disease presented with an abnormal mass shadow in the apex of the right lung on chest X-ray. Based on computed tomography imaging, a diagnosis of right SAA was established, and an excision of the aneurysm was performed. Because the left vertebral artery is dominant, the proximal and distal right subclavian artery and right vertebral artery were clamped. Then, the aneurysm was excised, and resection anastomosis was performed. Histological findings revealed FMD. The postsurgical course has been uneventful after 2 years. Among treatment modalities, open surgery would be the first choice for SAAs with FMD, despite the current era of endovascular surgeries., (Copyright © 2018 Elsevier Inc. All rights reserved.)

We report herein the successful laparoscopic resection of an asymptomatic 3-cm middle colic artery aneurysm in a young woman. Endovascular treatment represents nowadays the first-line option facing visceral artery aneurysm, but in this case, embolization was excluded because of hostile anatomy. Advantages of laparoscopic approach were the safe resection of the aneurysm with immediate evaluation of the bowel tolerance and the possibility of a histological examination of the arterial wall, without the disadvantages of laparotomy., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: To investigate whether angiopoietin-1 (Ang-1) could regulate the endothelial progenitor cells (EPCs) survival and the effect of accelerating intra-aneurysmal organization and occlusion of the aneurysm neck., Methods: EPCs were isolated from Wistar rats. EPCs were cultured and transfected with lentivirus-Ang-1-endothelial progenitor cells (Ang-1-EPCs) and lentivirus-NC-endothelial progenitor cells (NC-EPCs). The effects of Ang-1 on viability and functioning of EPCs were explored via tube formation, migration, and MTT (3-[4,5-dimethylthiazolyl-2]-2,5-diphenyltetrazolium bromide) assays. Eighteen Wistar rats were randomly allocated into 3 groups. Eighteen bare coils were inserted into the ligated external carotid artery (ECA) sacs of rats. The ECA sacs were removed 2 weeks after the coils were implanted and examined by histology assay., Results: Ang-1 significantly promoted EPCs tube formation, migration, and proliferation ability in vitro. Histology analyses revealed that the organized areas in the ECA sacs in the Ang-1-EPCs group are higher than NC-EPCs group and control group at 2 weeks. Immunofluorescence revealed that organized tissues were characterized by an accumulation of cells positive for α-smooth muscle actin-positive cells in aneurysm sacs., Conclusions: Overexpression of Ang-1 enhanced the tube formation, migration, and proliferation ability of EPCs. Ang-1 gene-modified EPCs accelerated organization within the aneurysms and occlusion of aneurysm neck. Transplantation of Ang-1-transfected EPCs may be a new method for the treatment of aneurysm., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Intravascular papillary endothelial hyperplasia (IPEH) is a benign lesion of vascular origin characterized by excessive proliferation of endothelial cells in normal blood vessels or aneurysms. A 51-year-old woman presented with a hard pulsatile mass in the left antecubital fossa. Duplex scan imaging revealed a brachial artery aneurysm with intramural thrombus. At surgery, the aneurysm was resected, and the brachio-radio-ulnar artery was bypassed with a saphenous vein graft. Histopathologic examination revealed papillary endothelial hyperplasia with features of epithelioid hemangioma. We present the first reported case of IPEH associated with a brachial artery aneurysm., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: Multilayer stent has become a new endovascular strategy for visceral artery aneurysm repair. However, its use was not allowed in some areas, such as China. This study evaluates an alternative method: multiple overlapping bare stents for repairing visceral artery aneurysms., Methods: Twenty-four patients with celiac artery aneurysm (n = 2), splenic artery aneurysm (n = 8), hepatic artery aneurysm (n = 3), superior mesenteric artery aneurysm (n = 6), and renal artery aneurysm (n = 5) were treated with 2 to 4 overlapping bare stents. Long-term results, including clinical achievement ratio and target artery patency, were followed up with computed tomographic angiography., Results: Insertion of overlapping bare stents was successful in all patients. Five aneurysms (21%) were totally excluded 3 months after operation, increasing to 12 (50%) and 20 (83%) aneurysms with total isolation at 6 and 12 months' follow-up, respectively. The clinical achievement ratios of multiple overlapping bare stents on splenic artery aneurysms, hepatic artery aneurysms, renal artery aneurysms, celiac artery aneurysms, and superior mesenteric artery aneurysms were 75%, 100%, 80%, 50%, and 100%, respectively. All cases combined had 100% target artery patency., Conclusions: Preliminary experience showed that repair using multiple overlapping bare stents seemed to be a potential alternative strategy for treating visceral artery aneurysm, resulting in target artery patency. However, the exact mechanism requires further study and more cases should be involved., (Copyright © 2013 Elsevier Inc. All rights reserved.)

This report is the first to describe the clinical, radiographic, operative, and pathologic findings associated with large, bilateral dorsalis pedis artery true aneurysms in a single patient. A 61-year-old African American woman complained of difficulty in wearing shoes. She had a moderately firm, nontender, pulsatile mass on the dorsum of her right foot. Computed tomography and angiography confirmed dorsalis pedis artery aneurysm with sufficient collateralization. She underwent resection without reconstruction. Pathologic analysis revealed a true aneurysm (8 × 5.3 × 4.1 cm(3)) containing intralumenal thrombus. Treatment for small symptomatic and large dorsalis pedis artery aneurysms remains resection with or without reconstruction., (Copyright © 2012 Annals of Vascular Surgery Inc. Published by Elsevier Inc. All rights reserved.)

Background: Carotid aneurysm is a rare condition and mostly caused by atherosclerosis, trauma, or fibrodysplasia. Angiosarcoma is an unusual cause for large vessels' aneurysms and a rare malignant neoplasm that may occur in any region of the body, yet seldom originates in the large blood vessels. We report a rare case of an angiosarcoma in the wall of a recurrent carotid aneurysm., Method: We undertook a literature review, and only a few cases of vascular aneurysms are reported to be involving or be caused by angiosarcoma. The main aneurysms affected are those of aortic and popliteal arteries. We report the case of a 61-year-old man with an angiosarcoma of the carotid artery. Biopsy of the arterial wall confirmed angiosarcoma., Conclusion: From our study, we conclude that an unresolving or recurring aneurysm with equivocal radiological investigations should raise the suspicion of malignancy., (Copyright © 2011 Annals of Vascular Surgery Inc. Published by Elsevier Inc. All rights reserved.)

Colonic vascular ectasia is a condition characterized by dilated submucosal veins, venules, or capillaries found commonly in patients with lower gastrointestinal hemorrhage. We present a case of colorectal ectasia associated with ischemia and an inferior mesenteric artery aneurysm. These pathologic findings may be the result of the vascular ectasia and may add to the natural history of this condition., (Copyright © 2011 Annals of Vascular Surgery Inc. All rights reserved.)

A 44-year-old male presented to our vascular surgery unit with a partially thrombosed 22 mm popliteal aneurysm giving rise to progressive distal ischemia. Microscopy of embolus retrieved from the posterior tibial artery at bypass surgery revealed the unexpected finding of intravascular papillary endothelial hyperplasia (Masson's pseudoangiosarcoma)., (Copyright 2009 Annals of Vascular Surgery Inc. Published by Elsevier Inc. All rights reserved.)

We report a case of an asymptomatic popliteal aneurysm due to fibromuscular dysplasia (FMD), associated with suspected FMD of pedal artery on a 63-year-old woman. The popliteal aneurysm was resected. An in situ interposition of a short segment of hypogastric artery was performed to restore the arterial continuity. Popliteal FMD was confirmed by histological findings. Only 5 cases are reported in literature. FMD of pedal artery was suspected on the CT-scan aspect. FMD is a rare cause of popliteal aneurysm. To our knowledge, this is the first report of suspected fibrodysplastic dilatation of a foot artery.

Splenic artery aneurysms (SAAs) are relatively rare. Moreover, there has been only one previous report of fibromuscular dysplasia (FMD) affecting the splenic artery alone. We describe a 64-year-old man with long, segmental, large, and multiple SAAs in whom the splenic artery branched from the aorta. The patient underwent endoaneurysmorrhaphy and splenectomy, with ligation in the proximal segment of the splenic artery. Histopathological analyses of resected specimens showed characteristics compatible with FMD. To our knowledge, long, segmental, large, and multiple SAAs caused by FMD have not previously been reported.

Four cases (three women and one man) of embolization of visceral artery aneurysms are presented, of which two affected the splenic artery and two the renal artery. The two renal aneurysms were related to hypertension; one of the splenic aneurysms was diagnosed in the context of hypertension, and the other affected a woman of a fertile age. Microguides, microcatheters, and Guglielmi platinum coils, liberated by electrolysis, with different lengths and characteristics, were used. Also, one of the renal aneurysm cases was related to the placing of a stent due to the existence of a stenosis of the renal artery adjacent to the aneurysmatic neck. Immediate occlusion of the aneurysm was achieved in the four cases. Evaluation with nuclear magnetic resonance angiography carried out 3 months later confirmed the sealing of the aneurysm and the patency of the native artery. Currently available devices provide a good therapeutic option for the embolization of visceral aneurysms with low morbidity and mortality rates.

We evaluated outcomes of endovascular treatment of splenic artery aneurysms and pseudoaneurysms. From April 2002 to May 2007, 17 patients (mean age 55.2 years, range 17-82) with splenic artery aneurysms (n = 7) or pseudoaneurysms (n = 10) underwent endovascular treatment. Six patients were asymptomatic, three had symptomatic nonruptured aneurysms, and eight had ruptured aneurysms. Lesions were in the proximal splenic artery (n = 5), intermediate splenic artery (n = 3), splenic hilum (n = 6), or parenchyma (n = 3). Embolization was with microcoils by sac packing (n = 8), sandwich occlusion of the main splenic artery (n = 4), or cyanoacrylate glue into the feeding artery (n = 4). Computed angiotomography was done within the first month and magnetic resonance angiography after 6 and 12 months, then yearly. Mean follow-up was 29 months (range 1-62). Exclusion of the aneurysm was achieved in 16 (94.1%) patients. One patient with an intraparenchymal pseudoaneurysm underwent splenectomy after failed distal catheterization. No major complications occurred. Postembolization syndrome developed in four patients, who had radiographic evidence of splenic microinfarcts. Transcatheter embolization of splenic artery aneurysms/pseudoaneurysms is safe and effective and may induce less morbidity than open surgery, in particular by preserving the spleen. Coil artifacts may make magnetic resonance angiography preferable over computed tomography for follow-up.

Intravascular papillary endothelial hyperplasia (Masson's vegetant hemangioendothelioma) is a rare condition affecting the arteries. In the literature, we did not find any reference to this lesion involving the humeral artery. We present a case of asymptomatic humeral artery vascular tumor due to this abnormality. A 58-year-old woman was admitted to our hospital with an asymptomatic pulsatile humeral artery mass. Echography revealed an increase in size in the last year. The tumor was removed, and the vascular segment was replaced by a segment of inverted cephalic vein. The findings of the pathological examination were compatible with intravascular papillary endothelial hyperplasia. At follow-up examination 5 months after the operation, the patient had no tumor, remained asymptomatic, and had preserved upper limb artery patency. This rare vascular lesion may be clinically and histopathologically mistaken for a malignant tumor. As the Masson tumor can be cured by complete surgical resection, it is important to get a correct diagnosis.

Cephalic vein aneurysms are rare malformations that may develop in any part of the vascular system, and their history, presentation, and management vary depending on their site. The etiology of venous aneurysms remains unclear, although several theories have been elaborated. Venous aneurysms are unusual vascular malformations that occur equally between the sexes and are seen at any age; they can present as either a painful or a painless subcutaneous mass. No serious complications have been reported from upper extremity venous aneurysms. Surgical excision is the definitive management for most of these. The case reported here presented with a painless and mobile, soft, subcutaneous mass that caused only cosmetic concern.

Mesenteric arterial branch aneurysms are rare. Giant, multiple, mesenteric branch artery aneurysms are even more uncommon, and only a few reports exist in the literature. We describe a 73-year-old asymptomatic female found to have an abdominal bruit and subsequently diagnosed with multiple mesenteric branch artery aneurysms by computed tomography and angiography. In addition, the patient was found to have celiac artery occlusion at its origin. Risk factors include hypertension, hyperlipidemia, grandmultiparity, and tobacco dependence. She was treated successfully with open surgery including ligation of multiple branch aneurysms and vein bypass reconstruction to preserve hepatic and mesenteric artery flow. Our purpose is to review this uncommon entity in terms of diagnosis, etiology, treatment options, and literature review.

The neurofibromatoses are a heterogeneous set of genetic disorders having clinical manifestations that involve the skin, the nervous system, or both. In addition, the disease can be confounded by a broad spectrum of complications, such as various kinds of osseous lesion, vascular lesions, aqueduct stenosis, optic glioma, and learning disabilities. Neurofibromatosis results in vascular involvement in approximately 10% of cases. Stenotic lesions predominate, but aneurysms have been documented as well. Rarely noted, however, have been peripheral aneurysms. In this report, we discuss the case of a 66-year-old woman with type 1 neurofibromatosis and a popliteal artery aneurysm who was operated upon because of threatened limb ischemia. Histological findings confirmed neurofibromatous invasion of the vessel wall.

Although vein graft aneurysms have been described to be atherosclerotic in nature, it has been hypothesized that vein graft aneurysms may be a part of a systemic dilating process. In the case reported here, histopathologic examination of vein graft aneurysms demonstrates aneurysmal degeneration with no atherosclerotic changes and do support the hypothesis that vein graft aneurysms may be a manifestation of a systemic dilating process.

We report a case of a 69-year-old female patient diagnosed with an axillary-subclavian artery(ASA) aneurysm, 7 cm long and 4 cm in diameter. The aneurysm had recently developed during follow-up for aortic sinus dilation associated with Marfan syndrome, which had been diagnosed in 1987. The patient underwent corrective surgery for the ASA aneurysm, and the aneurysm was histologically diagnosed as a true type with cystic medionecrosis.

We operated upon an 18-year-old female presenting a spontaneous aneurysm of the axillary vein. Pathologic examination of the aneurysm showed an anomalous muscular layer. To our knowledge, this is the first case of nontraumatic axillary venous aneurysm.

Annuloaortic ectasia and dissection of the ascending aorta are common cardiovascular complications of Marfan's syndrome. True aneurysms of the subclavian arteries in these patients are rare. We present an unusual case of a 37-year-old woman who over the span of 10 years sequentially developed an aneurysm of the ascending aorta (annuloaortic ectasia), a right subclavian artery aneurysm, a left axillary-subclavian artery aneurysm, and a dissection of the aortic arch. Aside from the aortic dissection, the aneurysms produced no symptoms. All vascular complications were detected with computed tomography and managed successfully. This case emphasizes the need for close postoperative surveillance in patients with Marfan's syndrome who have had one cardiovascular complication of the disease.

Aneurysms of the inferior vena cava (IVC) include a diverse group of anomalies with distinct anatomic and clinical characteristics. We report a diverticular aneurysm of the suprarenal IVC in a 45-year-old man who presented with extensive IVC and unilateral lower extremity thrombosis. A CT scan revealed an 8 cm smooth-walled mass containing thrombus to the right of the IVC and behind the second portion of the duodenum. At laparotomy a connection between the mass and the suprarenal IVC was established. Biopsy of the wall of the mass revealed vascular smooth muscle, thus establishing the diagnosis of a diverticular IVC aneurysm. MR angiography further disclosed interruption of the infrahepatic vena cava and return of renal vein flow via the azygous and hemiazygous veins. Twelve additional cases of IVC aneurysm are reviewed. A proposed classification of these aneurysms into four types consistent with their anatomic and embryologic characteristics is presented.

Blunt trauma involving the innominate and carotid arteries is a rare occurrence that can be lethal or have serious neurologic sequelae. To our knowledge this is the first reported case in the international literature describing the association of posttraumatic innominate artery aneurysm with total occlusion and thrombosis of the common carotid artery at its origin by an intimal flap. The diagnostic problems created by this unusual injury are discussed. In this case the patency of the distal portion of the common and internal carotid arteries was demonstrated by magnetic resonance angiography (MRA), whereas color duplex and digital arteriographic studies were unsuccessful. This demonstration was crucial to patient management. Since no studies are available comparing color duplex imaging, conventional arteriography, and MRA in the evaluation of blunt carotid trauma, this case study is presented to demonstrate the utility of MRA in emergency situations. In addition, we analyze the possible pathogenesis and discuss the surgical treatment.

An 82-year-old man was admitted with a left hip fracture sustained in a fall. The fracture was surgically repaired. Ipsilateral leg swelling developed over the following 2 weeks. A lower extremity venous duplex scan demonstrated isolated dilatation of the popliteal veins in both lower extremities. Chronic thrombosis was noted in both popliteal veins at the level of this dilatation. Initial duplex scanning also revealed acute thrombus in the left popliteal, posterior tibial, and peroneal veins. A repeat scan 1 week later identified propagation of thrombus into the superficial femoral vein. Popliteal vein aneurysms, although rare, can cause significant morbidity and mortality. The literature is also reviewed.

We analyzed 52 surgically excised ePTFE grafts used as secondary vascular access in chronic hemodialysis patients, structurally and histopathologically. Pseudoaneurysm formation at the site of repeated venipuncture was the main cause of surgical removal later than two years after implantation. Repeated needle punctures, twice per treatment, two or three times a week may result in a perigraft fibrous tissue capsule directly above areas where the graft was punctured. The delicate microporous structure of the graft wall was shown to be disrupted by needle punctures. The needle puncture sites were filled by surrounding connective tissue, and in one case, capillary formation was observed within the puncture sites. Examination by both light and scanning electron microscopy demonstrated identical patterns of pseudointima on the luminal surface. A thin pannus of endothelium-like cells, confined to the vicinity of the anastomoses, was noted in only four cases. On other areas of the luminal surface without endothelium, a red coagulum incorporating blood cells and fibrin was observed. Histological evidence of acute infection was absent in 61% of the cases and only 27% were considered to be clinically infected. Careful needle puncture technique, systematic rotation of puncture sites, and the use of rigorous aseptic technique are essential in preserving the long-term structural integrity of the vascular access, despite the good mechanical properties and reasonable good resistance to infection of ePTFE grafts.

Arterial lesions in patients with neurofibromatosis are rarely described and in most cases are stenotic. The aneurysmal changes reported in the literature are usually characterized by multiple microaneurysms due to the dysplastic lesions of the artery. We report a case of a single aneurysm of the inferior hilar branch of the left renal artery of a young female with neurofibromatosis. The patient showed hypoperfusion of the renal pole fed by this branch and was hypertensive. The aneurysm had a diameter of 4 cm and showed the histological findings typical of dysplastic lesions of neurofibromatosis. The hypertension and the renal pole hypoperfusion recovered after surgical excision of the aneurysm and end-to-end anastomosis of the hilar branch stumps.

We report the case of a 62-year-old man with Behçet's disease revealed by double aneurysmal involvement of the posterior tibial and popliteal arteries. The diagnosis was suggested because of repeated phlebitis, buccal aphthous ulcerations, and results of human leukocyte antigen gene typing. The different arguments leading to the diagnosis of Behçet's disease and appropriate treatment are presented.

The authors report the case of a 37-year-old man with bilateral posterior tibial artery aneurysms and concomitant collagen vascular disease. The patient initially presented with pain and swelling of the calves. The diagnosis was made by duplex scan and confirmed with arteriography. Diagnostic studies later verified the presence of a lupus-like syndrome. To date, 10 patients with aneurysms of the infrapopliteal arteries have been reported in the literature; four of these have had associated systemic diseases. These reports are reviewed; their clinical manifestations are discussed, and a treatment plan for these uncommon lesions is presented.

We describe a single case of Kawasaki's disease (mucocutaneous lymph node syndrome) with the rare complication of a hepatic artery aneurysm which was surgically repaired. Unusual features include arterial aneurysmal formation in the hepatic arteries rather than in coronary arteries, the unusual morphology of the hepatic artery aneurysm, and the expansion of the aneurysm after corticosteroid therapy.

Venous aneurysms are extremely rare. They may be congenital or acquired in origin and occasionally related to arteriovenous communications. A 58-year-old man complained of dull left lower quadrant pain and constipation. On physical examination a soft deep mass was palpated. Ultrasonogram and CT scan revealed a cystic formation in the pelvic cavity. Angiograms disclosed an arteriovenous malformation (AVM) at the pelvic floor draining into a large cavity. The patient was successfully managed by intraoperative selective embolization of the AVM and partial resection of a 10.6 x 8 x 6.7 cm venous aneurysm. The histopathologic studies of the wall confirmed a venous structure. Venous dilatation has been reported in high flow vein grafts, blood access V fistulas and rarely, proximal to traumatic AV fistulas of the lower extremities. The etiology of the present case is probably congenital, being to the best of our knowledge, the first case affecting the hypogastric territory, reported in the English literature.

One of the early diamond crimped knitted polyester (Dacron) grafts was surgically excised after implantation for 25 years in the aorto-biiliac position because of false aneurysm formation at the three anastomotic sites. The sutures were no longer visible. While the areas around the false aneurysm were poorly incorporated, the graft limbs were well encapsulated with some endothelial-like cells on the luminal surface. The integrity of the graft was well preserved despite mild fraying and the disruption of one stitch.

During the follow-up of 130 patients with in-situ bypasses 11 patients were reoperated following the detection of degenerative changes. The lesions found included anastomotic aneurysms (1), diffuse dilatation (2), localized aneurysms (5), stenosis of valve sites (2), and diffuse narrowing (1). The mean interval for the onset of a lesion was eight months. Histologic findings showed fibrous thickening of the intima, replacements of myocytes by collagen in the media, and moderate adventitial fibrosis. With some quantitative differences these changes are similar to those reported in reversed vein bypasses. It is therefore concluded that devascularization of the adventitia, as happens in reversed bypasses, is not an important etiology in the development of degenerative changes. The better patency rate reported for in-situ bypasses is the result of hemodynamic factors, but not because in-situ bypasses are protected from degenerative changes by their intact adventitial supply.