Homologous Vein Grafts Research Articles

Portal vein wedge resection and patch venoplasty using autologous and homologous vein grafts during surgery for hepatobiliary malignancies.

Obtaining tumor-free resection margins is one of the most important factors for achieving favorable prognosis of patients undergoing resection for hepatobiliary malignancies. In this study, we present our experience of portal vein (PV) wedge resection and patch venoplasty using autologous or homologous vessel grafts for resecting perihilar cholangiocarcinoma, hepatocellular carcinoma, and distal bile duct cancer. Case 1 was 68-year-old male patient with type IV perihilar cholangiocarcinoma who underwent central bisectionectomy with caudate lobectomy and bile duct resection, and PV wedge resection and patch venoplasty with a cryopreserved iliac vein allograft patch. This patient survived 14 months after surgery. Case 2 was 77-year-old male patient with type IIIA perihilar cholangiocarcinoma who underwent left medial sectionectomy with caudate lobectomy, bile duct resection, and PV wedge resection and patch venoplasty with a cryopreserved iliac vein allograft patch. This patient survived 17 months after surgery. Case 3 was 54-year-old male patient with hepatitis B virus-associated liver cirrhosis and hepatocellular carcinoma with PV tumor thrombus who underwent left hepatectomy. The PV wall defect was repaired with an autologous greater saphenous vein patch. This patient survived 11 months after surgery. Case 4 was 65-year-old female patient with distal bile duct cancer who underwent pylorus-preserving pancreaticoduodenectomy, and main PV wedge resection and patch venoplasty with a cryopreserved iliac artery allograft patch. This patient survived 21 months after surgery. In conclusion, PV wedge resection and patch venoplasty can be used to facilitate complete tumor resection in patients undergoing various extents of surgical resection for hepatobiliary malignancies.

Portal vein wedge resection and patch venoplasty using autologous and homologous vein grafts during surgery for hepatobiliary malignancies

Obtainment of tumor-free resection margins is one of the most important factors for favorable prognosis of patients undergoing resection for hepatobiliary malignancies. In this study, we present our experience of portal vein (PV) wedge resection and patch venoplasty using autologous or homologous vessel grafts used in resection for perihilar cholangiocarcinoma, hepatocellular carcinoma and distal bile duct cancer. Case 1: A 68-year-old male patient with type IV perihilar cholangiocarcinoma underwent central bisectionectomy with caudate lobectomy and bile duct resection, and PV wedge resection and patch venoplasty with a cryopreserved iliac vein allograft patch. This patient survived 14 months after surgery. Case 2: A 77-year-old male patient with type IIIA perihilar cholangiocarcinoma underwent left medial sectionectomy with caudate lobectomy and bile duct resection, and PV wedge resection and patch venoplasty with a cryopreserved iliac vein allograft patch. This patient survived 16 months after surgery. Case 3: A 54-year-old male patient with hepatitis B virus-associated liver cirrhosis and hepatocellular carcinoma with PV tumor thrombus underwent left hepatectomy. The PV wall defect was repaired with an autologous greater saphenous vein patch. This patient survived 11 months after surgery. Case 4: A 65-year-old female patient with distal bile duct cancer underwent pylorus-preserving pancreaticoduodenectomy and main PV wedge resection and patch venoplasty with a cryopreserved iliac artery allograft patch. This patient survived 21 months after surgery. In conclusion, PV wedge resection and patch venoplasty provide a useful option to facilitate complete tumor resection in patients undergoing various extents of surgical resection for hepatobiliary malignancies.

In Situ Procurement of a Recipient's Portal Vein for a Right Lobe Liver Graft With Multiple Venous Orifices: A Case Report

Reconstruction of multiple venous orifices of a right lobe graft is a time-consuming and troublesome procedure in right lobe living-donor liver transplantation. In the current study, we present a new venous reconstruction technique for a right lobe graft with multiple and complex hepatic vein (HV) orifices, in which procurement of the recipient's left portal vein was performed in situ to keep the anhepatic period to a minimum. All of the HV orifices were reconstructed together at the back table, while maintaining patency of the recipient's systemic and splanchnic circulation. A homologous vein graft and veno-venous bypass were not necessary. All HVs were patent during the follow-up and the patient was free from complications. In conclusion, the present technique is readily available for reconstruction of complex and multiple HV tributaries, while avoiding a long anhepatic time and the use of veno-venous bypass.

Outflow Reconstruction Using Cryopreserved Homologous Venous Grafts in Living Donor Liver Transplantation

ObjectivesThe techniques and outcomes of outflow reconstruction in living donor liver transplantation (LDLT) using cryopreserved homologous veins at the University of Tokyo Hospital are presented. MethodsWe performed 540 LDLTs from January 1996 to March 2015. Graft types included right liver graft (n = 262), left liver graft (n = 196), left lateral sector graft (n = 53), and posterior sector graft (n = 28). We routinely use cryopreserved homologous vein grafts for the hepatic vein reconstructions to secure the large outflow of the graft. In addition to the presentation of our techniques, the cases with symptomatic outflow obstruction and the treatments were also investigated. ResultsThe 1-, 3-, and 5-year graft survival rates were 90.6%, 86.1%, and 83.5%, respectively. The incidence of severe complications (Clavien-Dindo grade IIIb and more) was 38%. The overall incidence of outflow obstruction requiring invasive treatment was 1.9% (10/540), including 3 left liver grafts (1.5%, 3/196) and 7 right liver grafts (2.7%, 7/262). Regarding the patency of the reconstructed veins, the left hepatic vein, middle hepatic vein, and right hepatic vein achieved nearly 100% patency. On the contrary, venous tributaries such as V5, V8, and inferior right hepatic vein were frequently occluded in the postoperative course. ConclusionsOutflow reconstruction is a key for the successful LDLT. Cryopreserved homologous vein graft is useful for the promising hepatic vein reconstruction.

Safety and efficacy of cryopreserved homologous veins for venous reconstruction in pancreatoduodenectomy

There are several techniques for reconstructing the portal vein-superior mesenteric veinduring pancreatoduodenectomy. The aim of the present study was to present our results with portalvein-superior mesenteric vein reconstruction using cryopreserved homologous veins during pancreatoduodenectomy for patients with pancreatic head cancer. Patients who underwent pancreatoduodenectomy for pancreatic head cancer were reviewed retrospectively. In patients with portal vein-superior mesenteric vein resection, the detailed method of reconstruction and clinical outcomes were reviewed. Clinical characteristics, patient survival, and portal vein-superior mesenteric vein patency were compared between those with and without homologous vein grafts. Factors affecting the patency of reconstructed veins were assessed by univariate analysis. Among 144 patients undergoing pancreatoduodenectomy, portal vein-superior mesenteric vein resection was performed in 36 patients (25%); 18 (50%) underwent reconstruction with homologous veins, and the other 18 (50%) underwent reconstruction without homologous veins. The extent of portal vein-superior mesenteric vein involvement, operative time, duration of clamping of portal vein-superior mesenteric vein, intraoperative blood loss, and length of the venous resection were greater (P≤.013 each) in those with homologous vein grafts. There was no significant difference in postoperative morbidity/mortality, patient survival, or portal vein-superior mesenteric vein patency. The 1- and 2-year overall patency of portal vein-superior mesenteric vein was 76% and 71%, respectively, while the 2-year patencies were 67% and 67% in those with homologous veins and 87% and 73% in those without homologous veins without difference between the groups. Circumferential resection and pathologic portal vein-superior mesenteric vein involvement were associated with the patency of the reconstructed vein (P=.002 and P=.028, resp). Use of homologous venous grafts for portal vein-superior mesenteric vein reconstruction are feasible alternatives during pancreatoduodenectomy for advanced pancreatic head cancer.

Portal Vein Interposition Using Homologous Iliac Vein Graft during Extensive Resection for Hilar Bile Duct Cancer

Although autologous vein grafts have been used for portal vein (PV) reconstruction after long-segment portal vein resection during surgery for hilar bile duct cancer, their procurement prolongs operation time and increases morbidity. Less is known regarding the use of homologous vein grafts. The feasibility of homografts for PV reconstruction was preliminarily evaluated in two patients who underwent curative resection for hilar cholangiocarcinoma. Both patients underwent left lobectomy, caudate lobectomy, bile duct resection, and segmental PV resection and interposition vein graft reconstruction. The iliac vein homografts were obtained from deceased organ donors and stored for 1–2 days in cold preservation solution without freezing. Neither immunosuppression nor anticoagulation was attempted. One patient has shown good PV patency for 27 months. The second patient, who had received adjuvant chemoradiotherapy, showed an asymptomatic waisting at the proximal PV anastomosis site after 4 months, which was relieved by percutaneous balloon dilatation, and has been doing well for 12 months. In conclusion, our preliminary experience with these two patients suggests that cold-stored iliac vein homografts can be considered as PV substitutes after long PV segment resection during extensive hepatobiliary surgery.

Reconstruction for renal artery aneurysm: operative techniques and long-term results.

Ninety-four patients (37 male, 57 female; mean age, 51.0 years) underwent reconstruction for renal artery aneurysm (RAA) between 1980 and 2001. RAAs were present in 52 patients in the right kidney, in 29 patients in the left kidney, and in 13 patients in both kidneys. Eighty-three aneurysms were located in the mainstem, 49 in a branch artery, and four in an accessory artery. Additional ipsilateral renal artery stenoses (RAS) occurred in 26 patients, bilateral RAS in 18, and contralateral RAS in six. The causes of RAA were fibromuscular dysplasia (n = 48), atherosclerosis (n = 28), dissection (n = 7), aortic coarctation (n = 5), arteritis (n = 3), giant cell arteritis (n = 1), Marfan's syndrome (n = 1), and trauma (n = 1). Seventy-five patients had hypertension, 14 were asymptomatic, and five had rupture. Indications for RAA repair concerned aneurysms with 1 cm or more diameter in combination with risk factors of hypertension, ipsilateral and contralateral stenosis, and childbearing age in women. Without risk factors, aneurysm size eligible for reconstruction was limited to 2 cm or more. Methods applied for reconstruction in 107 kidneys and 136 aneurysms included aneurysm resection with tailoring (n = 37), saphenous vein graft interposition (n = 40), tailoring and saphenous vein graft interposition (n = 7), resection and reanastomosis (n = 14), saphenous vein graft interposition and resection and reanastomosis (n = 3), polytetrafluoroethylene bypass (n = 5), and homologous vein graft interposition (n = 1). Four reconstructions had to be performed ex situ because of multiple branch involvement in three patients and rupture in one. In all patients, the concerned kidney was protected with hypothermic flush perfusion with addition of heparin and prostaglandin E1. The overall morbidity rate was 17%, including one early graft occlusion, one partial thrombosis of the renal artery that necessitated fibrinolytic therapy, and a branch artery stenosis after tailoring managed with aortorenal bypass. The mortality in elective cases was null; one patient died of myocardial infarction 2 days after an emergency operation for ruptured RAA. The technical primary success rate was 96.8%; the secondary success rate was 98.9%. After a follow-up period from 1 to 143 months (mean, 46 months) in 83 patients (88%), 67 (81%) had patent renal arteries free of stenoses. Among six patients with RAS, four underwent successful reoperation, five had mainstem occlusions, three had segmental artery occlusions, and two underwent nephrectomy. Concerning the patients who underwent reoperation, percutaneous transluminal angioplasty was considered seriously but assessed as inappropriate because of long extension of stenosis or involvement of branch arteries. Hypertension was cured in 19 patients (25%) and improved in 17 (22%). Surgical reconstruction of RAA is a safe procedure that provides good long-term results, prevents aneurysm rupture, cures or improves hypertension in about half of the cases, and can be achieved with autogenous reconstruction in 96%.

A comparison between PTFE and denatured homologous vein grafts for haemodialysis access: a prospective randomised multicentre trial

To compare patency and complication rates of polytetrafluoroethylene (PTFE) grafts and denatured homologous vein (DHV) grafts for long-term haemodialysis. A prospective randomised multicentre trial. One hundred and thirty-one patients were enrolled between September 1994 and April 1997. Sixty-three DHV grafts and 68 PTFE grafts were implanted in 60 meals and 71 females. Complications and interventions were monitored. Patency rates, complication rates, and intervention rates of PTFE and DHV were compared. The mean follow-up was 313 days for DHV (range 1-771) and 339 (3-909) days for PTFE. The total follow-up was 54.1 patient-years for DHV and 63.1 for PTFE. The 1-year primary patency rates were 30% and 40% for DHV and PTFE respectively. Secondary patency rate was 63% for both DHV and PTFE. Most frequent complication was thrombosis. A total of 75 thrombotic events (1.39 per patient-year) occurred in 35 (56%) DHV grafts and 78 (1.24 per py) in 36 (53%) PTFE grafts. A total of nine infections were seen in nine (14%) DHV grafts, whereas 21 infections in 20 (29%) PTFE grafts were seen (p = 0.08). All but one infected DHV graft could be salvaged with systemic antibiotics. In contrast, surgical intervention was necessary in nine PTFE grafts (p = 0.02). For aneurysms, eight DHV and two PTFE grafts needed revision (p = 0.03). Patency rates between DHV and PTFE were not different. More infections were seen in PTFE grafts, and significantly more PTFE grafts needed surgical revision or removal because of infection. Significantly more DHV grafts were surgically revised or removed because of aneurysms.

Vein graft-coated vascular stents: a feasibility study in a canine model.

To evaluate different vein grafts for luminal coating of endovascular stents in normal canine arteries. Twenty-four tantalum Strecker stents were coated with either autologous (n = 10), denatured heterologous (n = 11), or denatured homologous vein grafts (n = 3). The carotid artery (n = 11) and the iliac artery (n = 13) were stented using a transfemoral approach. Angiograms were performed at days 0, 7, and 21, and months 3, 6, and 9. All grafts underwent histological examination. Eight of 10 autologous vein grafts showed patency during the whole observation period of 9 months, without histological signs of inflammation. Denatured heterologous vein grafts revealed acute (n = 3), subacute (n = 5), or delayed (n = 3) vessel occlusion. Hyaloid transformation of the vein graft and lympho-plasmacellular formations were seen. Denatured homologous vein grafts showed acute vessel occlusion. Although significant inflammatory tissue response was seen, no host-versus-graft reaction was present. Autologous vein graft-coated stents showed good biocompatibility in canine arteries. Preparation was cumbersome and required surgical venae-sectio. Denatured vein grafts, however, were limited by inflammatory reactions.

PTFE Prosthesis Versus Homologous Vein Grafts as Arteriovenous Fistula for Hemodialysis

This chapter gives a surgical perspective on the use of polytetrafluoroethylene (PTFE) prostheses versus homologous venous grafts for hemodialysis. The article describes the specific surgical indications for the use of a vascular prosthesis in these patients and where to implant the prosthesis; (i.e., specifically where in the forearm or whether a femoral approach should be used). The authors describe their experience with the types of material used for vascular prostheses.

A Preliminary Experience with the Human Homologous Vein Graft for Vascular Access

In a preliminary study, 38 preserved human homologous saphenous vein grafts were used for secondary vascular access in 36 chronic hemodialysis patients. Cumulative oneyear patency was 67%. Twelve grafts failed, 10 owing to thrombosis and 2 owing to infection. Overall complication rate, morbidity, and patency were compatible with the other available graft materials. A prospective randomized trial of Varivas graft against PTFE has been instigated.

The results of denatured homologous vein grafts as conduits for secondary haemodialysis access surgery

To determine the value of denatured homologous vein grafts as a conduit for secondary haemodialysis access. Retrospective clinical study. 2 University Hospitals. One-hundred-and-twenty-five patients received 195 grafts over a period of five years. Fifty-six first grafts (45%) functioned without complications throughout the study period of 5.8 years. Primary patency was 57% after 1 year and 25% after 3 years of follow-up. Of the initial grafts, 69 (55%) needed 161 interventions, for thrombosis (n = 59), stenosis (n = 43), failure beyond repair (n = 40), aneurysm (n = 12), infection (n = 4), steal syndrome (n = 1), and other causes (n = 2). Secondary patency was 76% at 1 year and 52% at 3 years of follow-up. A major advantage of these grafts was the low rate (2.6%) of infection. Aneurysm formation occurred 17 times in 195 grafts (8.7%). Denatured homologous vein graft is a good alternative in secondary access surgery.

Major vascular lesions associated with orthopaedic injuries.

Seventeen patients, aged 11-67 years (mean, 32.6), with major vascular injuries associated with traumatic orthopaedic injuries, were treated operatively in the authors' institution over a 4-year period. The most common mechanism of trauma was a high-energy injury (70.8%), and the rate of open injuries was 88.2%; 64.9% of the injuries were located in the lower extremities. The treatment protocol consisted of aggressive resuscitation; Doppler imaging and, when necessary, angiography; stable bone fixation with subsequent vascular repair; and extended wound debridement. The vascular repair for arterial lacerations consisted of (a) end-to-end anastomosis (47.2%); (b) interpositional homologous vein graft (23.6%); (c) vascular decompression through fracture distraction in one patient (5.9%); (d) xenograft interposition (in one patient; 5.9%); (e) venous repair (in three patients; 17.7%); and (f) embolectomy (in all patients). Three vascular reoperations (17.7%) were necessary because of rupture of the anastomosis. The authors' preferred bone stabilization method was external fixation, which was used in 47.2% of cases. Amputation was performed in three cases (17.7%) as a salvage operation. Although six patients (35.4%) were admitted with delayed shock (mean duration, 73.6 +/- 27.8 min), this led to a lethal outcome due to shock lung in only one patient. Another patient developed massive lung embolism 3 months postoperatively and died. The authors believe that this well-organized approach, based on a specific treatment protocol, for patients with severe orthopaedic trauma and concomitant vascular injury, not only improves outcome but gives good to excellent functional results in the majority of patients.

Biological Grafts for Vascular Access in Patients with End-Stage Renal Failure

From 1981 until 1987, 52 vascular accesses were created in patients with end stage renal failure; 392 could be studied retrospectively. Of these, 112 were created by using a biological graft: 88 homologous saphenous vein grafts and 24 bovine heterografts. The overall permeability rate was 94% postoperatively, 62% at 1 year, 45% at 2 and 3 years. There was no statistical difference in the permeability between human saphenous vein grafts and bovine heterografts or between grafts implanted as first access or after failure of an anterior fistula. The main complication observed during the followup was secondary throm bosis, which occurred after an average duration of 8 months. Aneurysms, infec tions, and high flow were very rare. Compared with the results observed with fistulas using the native veins, biological grafts results are poor. Compared with those of other authors 1/m especially for homologous saphenous vein grafts 1/m the authors' results are poor at 1 year and quite good at 2 and 3 years, These data should lead to detection of early stenosis before the end of the first year, especially stenosis of venovenous anastomoses, which are probably responsible for late thrombosis in most cases.

A Survey of Vascular Access for Haemodialysis in The Netherlands

After nearly 30 years of access surgery for haemodialysis, a survey of vascular access in a large population seemed relevant in order to analyse the state of the art. On 1 January 1988, 2195 patients in 52 centres in The Netherlands (population 14,714,900) were on long-term haemodialysis and 588 on continuous ambulant peritoneal dialysis (CAPD) for renal insufficiency. A questionnaire was mailed out, to which there was 100% response. Of all the patients on long-term haemodialysis, 70% had a Cimino fistula, 22% a graft fistula, and 6% a more proximal arm fistula. The remaining 2% had a Scribner shunt. Of all the graft fistulae, the expanded polytetrafluoroethylene (ePTFE) graft was the one most used (58%), followed by the homologous vein graft (25%), the autologous vein graft (13%), and those made of other materials (4%). Preference for acute access was recorded; catheterisation of the subclavian vein was used almost exclusively in 17 centres, while in 24 centres it was chosen in more than 50% of the cases. The femoral vein was almost always the choice for acute access in 6 centres and it was selected in more than 50% of the cases in 17 centres. Another alternative, the Scribner shunt, was applied in selected cases in 22 of the 52 centres. Percutaneous transluminal angioplasty (PTA), as a method for treating stenoses in vessels used for vascular access, was applied routinely in 5 centres and occasionally in 19 centres.

Biogenic grafts in arterial surgery--long-term results (I. The homologous vein--II. The modified heterologous bovine carotid artery--III. The human umbilical vein).

This report summarizes the authors' experience with homologous vein grafts, modified heterologous bovine carotid artery grafts and human umbilical vein grafts in reconstructive vascular surgery. The homologous saphenous vein, taken from living donors, was implanted in 21 patients. The high percentage of early and late complications (28% and 38%, respectively), the difficult availability and the development of modern materials appear to suggest that these grafts, at least the type used in this study, should no longer be employed. The experience with 102 femoro-popliteal and femoro-tibial bypasses in 140 revascularization operations carried out with modified heterologous bovine carotid artery grafts (Solcograft) is presented. The cumulative patency rate was 43% after 5 years for the above-knee and 33% for the below-knee femoro-popliteal bypasses. The high early and late complication rates (37% and 35%) lead us to believe that this graft should also no longer be employed. The human umbilical cord vein (Meadox-Dardik-Biograft) was used in performing 68 femoro-popliteal and 15 femoro-crural bypasses in 60 limbs of 57 patients. The patency rates calculated according to the standard life table method was 36% for the above-knee (after 5 years) and 32% for the below-knee femoro-popliteal bypass (after 4 years) and 31% (after 3 years) for the femoro-tibial bypass, respectively. On the understanding that other materials should be preferred in the individual case, this material still seems to be recommendable as a graft of second or third choice.

Homologous veins as an arterial substitute: Long-term results

From 1968 through 1982, 129 homologous vein grafts were used in 91 patients in the following positions: 75 in the femoropopliteal, tibial, or peroneal artery; 38 in the aortocoronary artery; 13 in the aortopulmonary artery; and one each in the atrioventricular fistula, carotid-subclavian artery, and brachial-radial artery. In the lower extremity patency ranged from 0 to 121 months (mean 22.4 ± 4.4 months). All grafts were performed for limb salvage, and 75% of the patients had undergone previous operations. Cumulative patency by the life-table method showed that while 50% of grafts occluded by 1 year, 60% of the remaining grafts continued to be functional for more than 5 years. Fifty percent of the aortocoronary bypass grafts studied were occluded at 1 year. Eight of the 13 systemic pulmonary artery shunts were patent at time of death, revision, or total correction. Multiple revisions and thrombectomies are required to maintain patency of homograft veins. The outcome is variable and unpredictable. The inconsistency is due to the antigenicity of the graft. If one is committed to the necessary efforts required to ensure long-term patency, the homologous saphenous vein is a suitable substitute when autogenous tissue is unavailable.

Homologous veins as an arterial substitute: long-term results.

From 1968 through 1982, 129 homologous vein grafts were used in 91 patients in the following positions: 75 in the femoropopliteal, tibial, or peroneal artery; 38 in the aortocoronary artery; 13 in the aortopulmonary artery; and one each in the atrioventricular fistula, carotid-subclavian artery, and brachial-radial artery. In the lower extremity patency ranged from 0 to 121 months (mean 22.4 +/- 4.4 months). All grafts were performed for limb salvage, and 75% of the patients had undergone previous operations. Cumulative patency by the life-table method showed that while 50% of grafts occluded by 1 year, 60% of the remaining grafts continued to be functional for more than 5 years. Fifty percent of the aortocoronary bypass grafts studied were occluded at 1 year. Eight of the 13 systemic pulmonary artery shunts were patent at time of death, revision, or total correction. Multiple revisions and thrombectomies are required to maintain patency of homograft veins. The outcome is variable and unpredictable. The inconsistency is due to the antigenicity of the graft. If one is committed to the necessary efforts required to ensure long-term patency, the homologous saphenous vein is a suitable substitute when autogenous tissue is unavailable.

Definitive surgical treatment of anomalous origin of left coronary artery: A new technical approach used successfully in a seven-month-old male infant

Anomalous origin of left coronary artery from the pulmonary artery is a very rare cardiac anomaly. Most patients with this defect die in the first year of life. Reconstructive surgery of the left coronary artery is the only saving measure in the management of this disease. A radical operation was successfully carried out in a seven-month-old boy by interposing a homologous saphenous vein (from his mother) between the aorta and left coronary artery. The operation was performed by use of deep hypothermia with surface cooling combined with limited cardiopulmonary bypass. The postoperative clinical course was uneventful and the patient relatively asymptomatic. Postoperative coronary angiograms revealed that the interposed homologous vein graft was patent, although it was slightly stenotic. Following the operation the patient showed good development and growth and has now reached 2 years of age. The purpose of this paper is to present the case by discussing our new operative technique.

Neovascularization of pseudointima as found in the freeze-dried homologous vein graft for the peripheral arteries

In our previous studies on the freeze-dried homologous vein graft implanted to the canine femoral artery as a patch graft, complete patency (22/22) and satisfactory healing of the pseudointima were observed. In these studies, a fine vascular channel communicating directly with the arterial lumen and being lined with the endothelial-like cells was found in the pseudointima microscopically. It was considered that this vascular channel in the pseudointima must be a newly developed vessel to nourish the fibrously thickened pseudointima of the graft.In this study, the microscopic examination by serial section technique and transluminal Microfil infusion method were carried out in order to make distinct the process of development and extension of these vascular channels in the thickened pseudointima. The freezedried homologous vein grafts were implanted to the canine femoral arteries as a patch graft and ten grafts were examined at various intervals from 3 to 175 days after implantation.In early stage, that is 10 and 11 days after implantation, some clefts communicating directly with the arterial lumen and containing some red blood cells were found in the mural thrombi near the suture line. They seemed to be an earliest feature of the above mentioned vascular channel. In all specimens 21 days and more later after implantation vascular channels communicating directly with the arterial lumen were found in the fibrously thickened pseudointima near the suture line as well as the central portion of the grafts, these vascular channels were more often observed near the suture line than the central part of the graft. They were lined with endothelial-like cells completely. The vascular channels arose from the arterial lumen near the suture line extended into the deeper layers of the pseudointima branching off in tributaries and some reached to the adventitial layers penetrating through the fibrous tissues proliferated in the suture line. On the other hand, those from the arterial lumen near the central part of the graft were found to develop vertically into the pseudointima and the extension was confined within the pseudointima without penetrating the graft towards the adventitial layer. Same findings as mentioned above were observed in microscopic examination by transluminal infusion of Microfil.From the findings above mentioned, it seemed reasonable to presume that the vascular channels communicating directly with the arterial lumen were not extension of the vasa vasorum from the adventitial layers but newly developed vessels in order to nourish the pseudointima of the graft, and they were formed through the clefts which was formed in the mural thrombi in the course of their organization in early stage.