I n the studies by Hume el al.' on the functional survival of renal homotransplants in patients with chronic renal insufficiency, it was observed that the period of homotransplant function in 4 of 9 recipients ranged from 5 to 25weeks. The course of the renal homotransplant in the normal dog contrasts with this wide range and long duration of the period of functional survival of renal homotransplants in the uremic patient. Irrespective of the manner in which the donor and/or recipient have been modified, including procedures known to suppress antibody formation, functional survival of the renal homotransplant in the dog seldom exceeds 1 week. Since there has been no uniformly successful experimental counterpart of chronic renal insufficiency in the dog, no information is presently available on the renal homotransplant function in the dog under these circumstances. In man, when the recipient does not have a chronic renal insufficiency, as exemplified by the case of Michon et aE.,2 the renal homotransplant functions well for about 3 weeks and then ceases to function rather abruptly, with the homotransplant showing the same morphologic pattern of rejection seen in the dog. This pattern has been interpreted as a morphologic representation of an antigen-antibody reaction; the immune response of the recipient to the renal homotransplant is believed to be the basis for the rejection. A delayed rejection or prolonged acceptance, therefore, may well represent an impaired immune response. Homotransplantation studies by Dempster3 and Simonsen4 have established a close antigenic relationship between the kidney and the skin. Should this relationship apply in man, one would expect the uremic recipient, if the prolonged functional survival is a manifestation of an impaired immune response, likewise to show a prolonged survival of skin homografts. I t was on this basis that the study to be described was undertaken.The first group of patients studied had chronic renal insufficiency with uremia that ranged from 4 months to 6 years in duration (TABLE 1). It may be noted that a variety of chronic lesions is represented, with uremia a common denominator.Skin homografts were accompanied by skin autografts in each case. The grafts were approximately square with an area of 3 to 4 sq. cm. The bed of the recipient site was subcutaneous tissue, and the grafts were full thickness. Biopsies from the homograft and the autograft were obtained simultaneously. Tissues were fixed in buffered 10-per cent formalin and processed through a modified Bouin solution. Hematoxylin and eosin, periodic acid-Schiff, Verhoeff-van Gieson, reticulum, and Feulgen stains were used.TABLE 2 summarizes the data on the recipient, donor type of homograft, the time interval to biopsy, and the estimate of the degree of homograft survival. "Pure" refers to grafts obtained from normal donors, "cortisone" to grafts from 967The upper arm was used as the site for the skin grafts.

Retrospective analysis of the authors' experience with 109 primary femoropopliteal bypass vein grafts that failed allows description of three distinct modes of failure. Within 30 days of surgery, failure resulted primarily from technical or judgmental errors. The development of stenotic lesions within the vein graft caused a second group of failures during the first year after bypass. The third group most commonly failed due to progression of peripheral atherosclerosis a year or more following original bypass. No correlation was found, however, between the mode of failure and results of secondary femoropopliteal-tibial reconstruction, which yielded an overall 50% five-year cumulative limb salvage rate. The results indicate that this salvage rate can be anticipated regardless of the number of secondary operations required. The highest long-term patency rate was achieved when frequent postoperative follow-up examinations allowed recognition of graft failure prior to total occlusion. Under such circumstances a simple vein patch of stenotic lesions yielded an 85% five-year graft patency. Following actual thrombosis, however, the highest five-year patency rate was achieved when reconstruction was performed using a new vein graft; saphenous vein and arm vein were equally effective. When prosthetic material was used, no secondary graft remained patent beyond three years. Finally, when a proximal or distal portion of the original vein graft proved adequate in caliber following thrombectomy, it could be successfully incorporated in a secondary reconstruction with the expectation of a 50% five-year limb salvage rate. No statistically significant difference was found in salvage rates among each of the patient groups representing the three common modes of graft failure. This finding, coupled with an acceptable 2.5% operative mortality rate, provides justification for an aggressive approach toward secondary femoropopliteal reconstruction.

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Polytetrafluoroethylene grafts have been used extensively for infrainguinal vascular reconstruction either as the conduit of choice or as a substitute when saphenous vein is unavailable. Although numerous studies have shown satisfactory early patency rates, the long-term efficacy of these grafts in a large number of patients for specific indications and in various positions has been less well defined. From 1977 to 1987 we used four PTFE grafts from three different manufacturers to perform 300 infrainguinal reconstructions on 240 patients on our vascular service. The indications for surgery were disabling claudication in 28% and limb salvage in 72%. The 30-day operative mortality of 1% was not different from the 1.4% associated with infrainguinal autogenous vein grafting. The 5-year cumulative patency rate achieved with all infrainguinal polytetrafluoroethylene grafts was 35%, significantly higher for grafts placed for claudication (57%) than those placed for limb salvage (24%). There were no significant differences between the above-knee and below-knee locations for distal anastomoses regardless of indication, but femoropopliteal grafts provided significantly higher 5-year patency (37%) than infrapopliteal grafts (12%). Comparison of the 5-year patency rates among the three manufacturers of polytetrafluoroethylene grafts showed no significant differences. Fifty-four polytetrafluoroethylene grafts that failed underwent 67 revisions after catheter thrombectomy or thrombolysis, which resulted in a minimal 11% 5-year patency rate. Based on this experience, it is concluded that infrainguinal polytetrafluoroethylene prostheses provide significantly inferior results when compared with autogenous reconstruction.