Warm ischemia time does not correlate with recipient graft function in laparoscopic donor nephrectomy.

BACKGROUND: Laparoscopic donor nephrectomy (LDN) has been shown to be a safe and effective option for renal procurement. Studies comparing open nephrectomy and hand-assisted laparoscopy have emphasized decreased warm ischemia time when compared with "pure" laparoscopic retrieval. However, no data exist that define exactly what constitutes a prolonged warm ischemia time in terms of recipient graft function. The aim of this study was to use a large, single-institution experience with LDN to determine if warm ischemia time correlates with recipient graft function as measured by serum creatinine levels. METHODS: A total of 640 LDNs were performed from March 1996 to August 2001. Warm ischemia times were prospectively collected and were defined as the time from renal artery occlusion to immersion in iced saline. Serial recipient creatinine levels were measured at 1 week and 1, 3, 6, and 12 months (when possible) from the transplant. Data were analyzed using Pearson correlation analysis at a confidence interval of 95%. RESULTS: Mean warm ischemia time was 151 s with a standard error of 3.4 s and ranged from 35 to 720 s. Recipient creatinine mean at 1 week was 1.94 mg/dl with a standard error of 0.06 mg/dl and ranged from 0.5 to 10.5 mg/dl. Recipient creatinine mean at 1 month was 1.68 mg/dl with a standard error of 0.06 mg/dl and ranged from 0.6 to 8.5 mg/dl. Recipient creatinine mean at 3 months was 1.60 mg/dl with a standard error of 0.04 mg/dl and ranged from 0.6 to 8.8 mg/dl. Recipient creatinine mean at 6 months was 1.63 mg/dl with a standard error of 0.06 mg/dl and ranged from 0.7 to 13.5 mg/dl. Recipient creatinine mean at 12 months was 1.70 mg/dl with a standard error of 0.07 mg/dl and ranged from 0.5 to 14.5 mg/dl. No correlation was found between warm ischemia time and recipient creatinine levels at 1 week (p = 0.4737), 1 month (p = 0.9180), 3 months (p = 0.6227), 6 months (p = 0.8349), or 12 months (p = 0.2835). CONCLUSIONS: Warm ischemia time does not correlate with recipient graft function in LDN within the range of times studied. Shorter warm ischemia time associated with open donor nephrectomy and hand-assisted LDN does not necessarily offer a measurable advantage in recipient graft function. During extraction of the kidney, expediency to minimize warm ischemia time should not supersede controlled and safe maneuvers in renal vessel division and extraction of the kidney.

Superiority of portal venous drainage over systemic venous drainage in pancreas transplantation: a retrospective study.

OBJECTIVE: To compare portal and systemic venous drainage of pancreas transplants and demonstrate an immunologic and survival superiority of portal venous drainage. SUMMARY BACKGROUND DATA: Traditionally, solitary pancreas transplants have been performed using systemic venous and bladder drainage, but more recently, the advantages of enteric drainage have been well documented. Although physiologic benefits for portal venous drainage have been described, the impact of portal venous drainage, especially with solitary pancreas transplants, has yet to be determined. METHODS: Since August 1995, 280 pancreas transplants with enteric duct drainage were analyzed. One hundred and seventeen were simultaneous pancreas and kidney (SPK), 63 with systemic venous drainage (SV) and 54 with portal venous drainage (PV). The remainder were solitary transplants; 97 pancreas after kidney (PAK; 42 SV and 55 PV) and 66 transplants alone (PTA; 26 SV and 40 PV). Immunosuppressive therapy was equivalent for both groups. RESULTS: The groups were similar with respect to recipient characteristics and HLA matching. Thirty-six month graft survival for all transplants was 79% for PV and 65% for SV (P =.008). By category, SPK graft survival was 74% for PV and 76% for SV, PAK graft survival was 70% for PV and 56% for SV, and PTA graft survival was 84% for PV and 50% for SV. The rate of at least one rejection episode was also significantly higher in the SV group. At 36 months, for all pancreas transplants, the rejection rate was 21% for PV and 52% for SV (P <.0001). For SPK, rejection rates were 9% for PV and 45% for SV. For PAK, rejection rates were 16% for PV and 65% for SV, and for PTA 36% for PV and 51% for SV. The rejection rates for kidneys following SPK were also lower in the PV group (26% versus 43% for SV). Furthermore, the grades of rejection were milder in PV for all transplants (P =.017). By multivariate analysis, portal venous drainage was the only parameter that significantly affected rejection. CONCLUSION: Graft survival and rejection is superior for PV. These clinical findings are consistent with published reports of experimentally induced portal tolerance and strongly argue that PV drainage should be the procedure of choice for pancreas transplantation.

Laparoscopic right donor nephrectomy: technique and comparison with left nephrectomy.

BACKGROUND: Laparoscopic donor nephrectomy (LDN) preferentially involves the left kidney to optimize vessel length, but occasionally, right nephrectomy is preferred. Right LDN differs markedly in anatomic relations and the need for a fourth port. This retrospective study compares donor outcomes and graft function of right and left LDN and describes the technique. METHODS: Consecutive patients undergoing right LDN from March 26, 1996 to December 31, 2000 were compared with those undergoing left LDN. Age, height, weight, body mass index, creatinine, creatinine clearance, operative time, warm ischemia time, analgesic requirements, serial postoperative creatinine, time to diet resumption, and hospital stay were compared. A second cohort matched for age, gender, race, and temporal left LDN also were compared with the group undergoing right LDN. RESULTS: No significant differences were found for any of the parameters measured. CONCLUSION: This study demonstrates that despite substantial differences in the procedures, donor outcome and graft survival are similar for right and left LDN.

A high panel-reactive antibody rescue protocol for cross-match-positive live donor kidney transplants.

BACKGROUND: Alloimmunization can present a virtually insurmountable barrier to kidney transplantation. Past protocols to desensitize patients using plasmapheresis and cyclophosphamide have not been broadly applied because of the fear of complications, including high rates of immunologic failure. METHODS: Fifteen patients with a positive donor-recipient cross-match were desensitized with plasmapheresis to permit live donor (LD) transplantation under newer maintenance immunosuppressants. Pretransplant the patients received plasmapheresis three times weekly for a planned maximum of six treatments, plus intravenous hyperimmune globulin, tacrolimus, mycophenolate mofetil, and prednisone. Patients who were successfully desensitized and received transplants were given 10 days of OKT3 postoperatively. RESULTS: Eleven of the 15 patients became anti-human globulin cross-match-negative after one to five plasmapheresis treatments and underwent LD transplantation. Relatively low initial titers of donor-specific antibody were predictive of successful attainment of a negative cross-match. Few side effects and rejection episodes were observed. All transplant patients remain dialysis-free after 3-26 months of follow-up. CONCLUSION: A positive cross-match is not necessarily a contraindication to LD transplantation, especially for patients with low donor-specific alloantibody titers.

Simultaneous cadaver pancreas living-donor kidney transplantation: a new approach for the type 1 diabetic uremic patient.

OBJECTIVE: To review the authors' experience with a new approach for type I diabetic uremic patients: simultaneous cadaver-donor pancreas and living-donor kidney transplant (SPLK). SUMMARY BACKGROUND DATA: Simultaneous cadaver kidney and pancreas transplantation (SPK) and living-donor kidney transplantation alone followed by a solitary cadaver-donor pancreas transplant (PAK) have been the transplant options for type I diabetic uremic patients. SPK pancreas graft survival has historically exceeded that of solitary pancreas transplantation. Recent improvement in solitary pancreas transplant survival rates has narrowed the advantage seen with SPK. PAK, however, requires sequential transplant operations. In contrast to PAK and SPK, SPLK is a single operation that offers the potential benefits of living kidney donation: shorter waiting time, expansion of the organ donor pool, and improved short-term and long-term renal graft function. METHODS: Between May 1998 and September 1999, the authors performed 30 SPLK procedures, coordinating the cadaver pancreas transplant with simultaneous transplantation of a laparoscopically removed living-donor kidney. Of the 30 SPLKs, 28 (93%) were portally and enterically drained. During the same period, the authors also performed 19 primary SPK and 17 primary PAK transplants. RESULTS: One-year pancreas, kidney, and patient survival rates were 88%, 95%, and 95% for SPLK recipients. One-year pancreas graft survival rates in SPK and PAK recipients were 84% and 71%. Of 30 SPLK transplants, 29 (97%) had immediate renal graft function, whereas 79% of SPK kidneys had immediate function. Reoperative rates, early readmission to the hospital, and initial length of stay were similar between SPLK and SPK recipients. SPLK recipients had a shorter wait time for transplantation. CONCLUSIONS: Early pancreas, kidney, and patient survival rates after SPLK are similar to those for SPK. Waiting time was significantly shortened. SPLK recipients had lower rates of delayed renal graft function than SPK recipients. Combining cadaver pancreas transplantation with living-donor kidney transplantation does not harm renal graft outcome. Given the advantages of living-donor kidney transplant, SPLK should be considered for all uremic type I diabetic patients with living donors.

Laparoscopic live donor nephrectomy: the University of Maryland 3-year experience.

PURPOSE: We determined whether laparoscopic living donor nephrectomy decreases the morbidity of renal donation for the donor, while providing a renal allograft of a quality comparable to that of open donor nephrectomy. MATERIALS AND METHODS: In a 3-year period laparoscopic donor nephrectomy was performed via the transperitoneal approach. We evaluated donor and recipient medical records for preoperative donor characteristics, intraoperative parameters and complications, and postoperative recovery and complications. RESULTS: Of the 320 laparoscopic donor nephrectomies performed the left kidney was removed in 97.5%. Intraoperative complications, which developed in 10.4% of cases, tended to occur early in the experience and required conversion to open nephrectomy in 5. Average operative time was 31/2 hours and warm ischemia time was 21/2 minutes. As the series progressed, blood loss as well as laparoscopic port size and number decreased but extraction site size remained constant at 7 cm. Urinary retention, prolonged ileus, thigh numbness and incisional hernia were the most common postoperative complications. Postoperative analgesic requirements were low and average hospitalization was 66 hours. CONCLUSIONS: Laparoscopic donor nephrectomy appears to be safe and decreases morbidity in the renal donor. Allograft function is comparable to that in open nephrectomy series. The availability of laparoscopic harvesting may be increasing the living donor volunteer pool.

Increased rates of donation with laparoscopic donor nephrectomy.

OBJECTIVE: To examine the impact of laparoscopic nephrectomy and recipient education on the proportion of kidney recipients who could identify a potential live donor, and on the live donor (LD) transplantation rate. SUMMARY BACKGROUND DATA: Laparoscopic donor nephrectomy (LDN) results in less postoperative surgical pain, a shorter hospital stay, and quicker recovery than the standard open donor nephrectomy (ODN). The authors hypothesized that the availability of this less invasive surgical technique would enhance the willingness of family and friends to donate. METHODS: The study population consisted of 3,298 end-stage renal disease patients referred for kidney transplant evaluation between November 1991 and February 2000, divided into three groups. The first group received no formal LD education and had only ODN available. The second group received formal education about the LD process and had only ODN available. The third group had both formal LD education and LDN available. Records were examined to determine what proportion of each group had any potential donors tissue-typed, and the rate at which they received an LD transplant. RESULTS: Before LDN availability and formal LD education, only 35.1% of referrals found a potential donor, and only 12.2% received an LD transplant within 3 years. Institution of a formal education program increased the volunteer rate to 39.0%, and 16.5% received an LD transplant. When LDN became available, 50% of patients were able to find at least one potential donor, and within 3 years 24.7% received an LD transplant. Regression analysis indicated that availability of LDN was independently associated with a 1.9 relative risk of receiving an LD transplant. Kaplan-Meier death-censored 1- and 3-year graft survival rates for ODN transplants were 95.8% and 90.6%, versus 97.5% and 94. 8% for LDN. CONCLUSIONS: The availability of LDN and an LD family education program has doubled the live donor transplantation rate, and outcomes remain excellent.

Erythropoietin response to post-liver transplantation anemia.

Anemia frequently accompanies end-stage liver disease. Erythropoietin has recently been shown to be of benefit in a number of diseases complicated by anemia. We studied erythropoietin levels before and after orthotopic liver transplantation (OLT) and correlated these with the degree of anemia. Twenty-seven patients with end-stage cirrhosis who underwent OLT had preoperative and weekly postoperative serum erythropoietin levels determined by a highly sensitive radioimmunoassay. The relation of erythropoietin level to the values for hematocrit, serum creatinine, and cyclosporine and other biochemical test results was evaluated. Before transplantation, 23 patients were anemic; erythropoietin levels were appropriately elevated (72.7 +/- 37 mU/mL; normal, 10 to 15 mU/mL) for the degree of anemia (hematocrit, 33.1% +/- 1%) in 16 patients (70%). A blunted erythropoietin response to anemia was found in 7 of the anemic patients with cirrhosis (30%). After OLT, the hematocrit decreased to 29.5% +/- 0.6% at 4 weeks, with a reciprocal increase in serum erythropoietin levels to 36 +/- 5 mU/mL. Erythropoietin response appeared appropriate to the degree of anemia in 82% of the liver transplant recipients and blunted in 18%. We conclude that the ability to secrete erythropoietin in response to anemia is defective in many patients with end-stage liver disease, and a normal response may be restored after OLT. The results suggest that exogenous erythropoietin administration may be beneficial in anemic patients with cirrhosis and liver transplant recipients who have inappropriately low serum erythropoietin levels.

Laparoscopic nephrectomy in the markedly obese living renal donor.

OBJECTIVES: To determine whether laparoscopic living donor nephrectomy is safe and efficacious in markedly obese renal donors. METHODS: From 1996 to 1999, 431 laparoscopic living donor nephrectomies were performed. The markedly obese group consisted of 41 patients with a body mass index (BMI) greater than 35. Forty-one controls with a BMI less than 30 were matched to the obese donors by sex, age, race, and date of surgery. RESULTS: The markedly obese and control groups were closely matched in sex, race, age, serum creatinine level, creatinine clearance, HLA match to recipient, side of donated kidney, and experience level of the surgeons. The obese patients had a BMI range of 35.2 to 53.9 (mean 39.3), and the control patients had a BMI range of 18.4 to 29.0 (mean 24.3). Donor operations in the markedly obese were significantly longer by an average of 40 minutes. The greater intraoperative blood loss and longer extraction incision length seen in the markedly obese did not reach statistical significance. More and larger laparoscopic ports were used in the markedly obese. Obese donors were more likely to require conversion from laparoscopic nephrectomy to open nephrectomy than ideal-sized donors. The postoperative recovery of the gastrointestinal tract, hospitalization time, analgesic requirements, and total complications were equal in the two groups, although the obese donors' complications tended to be cardiopulmonary problems. The recipient graft function was equivalent between the two groups. CONCLUSIONS: Laparoscopic living donor nephrectomy is more difficult to perform in the markedly obese but is associated with an equivalent donor morbidity and recipient renal outcome.

Simultaneous pancreas-kidney (SPK) and pancreas living-donor kidney (SPLK) transplantation at the University of Maryland.

The evolution of enteric and portal venous drainage, better immunosuppression, and better patient care has elevated pancreas transplantation with dramatically improved results. At our center, long-term graft survival and rejection has significantly improved with portal venous drainage, which has become our gold standard. This improvement is exemplified by the excellent one-year patient and graft survival rates for SPLK transplants. SPLK has proven to be an ideal approach in uremic Type 1 diabetic patients with living donors and should become the procedure of choice for that population. Moreover, the improved monitoring of rejection has allowed a similar success of pancreas transplantation alone in non-uremic patients with brittle diabetes. The treatment of diabetes mellitus has room for great improvement, however, and there is no question that islet transplantation, xenotransplantation, and the pursuit of immunologic tolerance will play an extremely important role in that endeavor.

The shrinking renal replacement therapy "break-even" point.

BACKGROUND: This study examines the current cost of live donor (LD) transplantation at our institution, and compares it with that of dialysis. METHODS: The study population consisted of 184 consecutive adult recipients of laparoscopically procured LD kidney transplants. Cost-containment measures instituted during this series included elimination of routine postoperative antilymphocyte induction and an accelerated discharge clinical pathway with planned discharge of the recipient on postoperative day (POD) 2. Costs of the transplants to Medicare were estimated from hospital charges, readmission rates, and immunosuppressant usage. These were compared with published costs of dialysis to Medicare in terms of a fiscal transplant-dialysis break-even point. RESULTS: Kaplan-Meier patient and graft survival rates at 1 year were 97 and 93%, respectively. Among patients followed for at least 90 days and treated with no induction and either cyclosporine-mycophenolate mofetil or tacrolimus-mycophenolate mofetil, acute rejection rates were low (27.6 and 13.9%, respectively). In the last 124 patients, 32.3% were discharged by POD 3 and 71.8% by POD 6, with corresponding mean transplant hospital charges (excluding organ acquisition) of $11,873 and $17,350, respectively. The 30-day readmission rate for patients discharged on the accelerated pathway by POD 3 was only 16%. The least expensive subgroup in the present study (30% of patients) was that of patients discharged by POD 6 and not readmitted during the first year; the break-even point with dialysis costs was calculated as 1.7 years after the transplant. CONCLUSIONS: The cost of LD transplants can be safely reduced by elimination of routine postoperative anti-lymphocyte immune induction and by an early discharge clinical pathway. Uncomplicated LD kidney transplants, meaning those with a short length of stay in the hospital after transplantation and no need for readmission within the first year, accrue savings over dialysis within 2 years.

Kidney transplantation at the University of Maryland.

1. The number of kidney transplants performed at the University of Maryland increased yearly from 51 in 1991 to 285 in 1998. Over the past 3 years, the increase in the number of kidney transplants can be ascribed almost exclusively to a marked increase in living donor transplants, from 49 cases in 1995 to 130 cases in 1998; a 160% increase. The increase in our frequency of living-donor kidney transplantation can be attributed to a formal family education program and the availability of the laparoscopic technique for kidney removal. 2. In addition to the availability of the laparoscopic technique, a number of special programs has allowed an increased number of living donor kidney transplants. This includes a special protocol for transplantation of Epstein-Barr virus negative recipients, a protocol for transplantation of patients who have a positive crossmatch with a living donor, as well as, the simultaneous living donor kidney/cadaver pancreas "SPK(LRD/PTA)" program. 3. The one-year graft and patient survival for the entire program was 87.0% and 94.5%, respectively. However, the more recent graft survival rates have markedly increased; Since August 1995, the one-year graft and patient survival was 89.8% and 95.8%, respectively. 4. Improvement in immunosuppression has lead to dramatic improvement in the success rates in living-donor kidney transplants. Despite the omission of antibody-based induction therapy, the one-year graft survival rate using a mycophenolate mofetil/tacrolimus-based immunosuppression protocol was 96.4%. The one-year rejection rate was 8% in Caucasian patients and 14% in African-American patients in this subgroup of living-donor kidney transplant recipients. 5. The data demonstrate that the use of the living-donor transplant option is grossly underutilized. Estimates are presented that more than 11,000 living-donor kidney transplants should be possible in the US yearly.

National Transplantation Pregnancy Registry: analysis of pregnancy outcomes in female liver transplant recipients.

Outcomes from 48 pregnancies in 34 female liver transplant recipients were analyzed. Data were collected via interviews, questionnaires, and hospital records. All recipients were treated with cyclosporine-based immunosuppression except 2 patients treated with FK506 and 2 treated with no immunosuppression. The age at conception was 26.1 +/- 5.9 years (mean +/- SD) with a transplant interval (time from transplantation to conception) of 2.9 +/- 2.5 years. There were 49 outcomes (1 set of twins): miscarriage 9 (18%), therapeutic abortion 4 (8%), and live birth 36 (74%). No stillbirths or ectopic pregnancies were reported. Of the 36 live births, the gestational age was 36.9 +/- 3.5 weeks, the birthweight was 2,604 +/- 698 grams, 39% were premature (< 37 weeks), and 31% had low birthweight (< 2,500 grams). No birth defects or neonatal deaths (< 28 days) were reported. The newborn complication rate was 17% (n = 6), 5% in premature infants. The incidence of drug-treated hypertension was 46%; pre-eclampsia 21%; infectious complications 26%; and Caesarean section 47%. Recipients with hypertension had a higher proportion of premature infants (71%) than normotensive patients (38%) (P = .04 by Fisher's exact test). Acute rejection was diagnosed in 6 pregnancies, 2 of which were ended by therapeutic abortion. Four recipients who continued their pregnancies were treated with increased immunosuppression for rejection, and all delivered livebirths. There were two grafts lost within 6 months of pregnancy. The only maternal death occurred in a patient who required retransplantation for recurrent C hepatitis 3 months afte therapeutic abortion and died 6 months later. The other recipient with graft loss was successfully retransplanted for chronic rejection 6 months after delivery. We draw the following conclusions: (1) female liver transplant recipients can safely undergo pregnancy, although there is a high rate of premature and low birthweight infants; (2) pregnancies in this population should be considered high-risk and require close monitoring of liver function; and (3) altered graft function during pregnancy should be thoroughly investigated.

Collagenase lot selection and purification for adipose tissue digestion.

Crude Clostridial collagenase (CCC) remains the most widely used enzyme for the digestion of tissues prior to cell isolation and culture. CCC contains numerous components in addition to specific collagenases and proteases. A chronic problem associated with CCC is significant lot variability which occurs with respect to the ability of different lots of CCC to digest tissue. We have evaluated numerous commercially available samples of CCC for their ability to digest human liposuction-derived SC fat. Digestion capacity was evaluated as the ability to release endothelial cells from fat as well as the ability of isolated cells to adhere to tissue culture plastic. A significant variation in digestion efficacy between lots of collagenase was observed. We subsequently purified CCC using a partial purification method with dialysis and centrifugation as well as a complete purification, using liquid chromatography, to remove all nonspecific proteases. While partially purified collagenase retained digestion capacity, pure collagenase exhibited reduced digestion capacity. Maximum digestion was achieved with pure collagenase when trypsin was added. The use of completely purified collagenase with trypsin is advantageous where all components in the enzyme digestion mixture must be known.

Variables affecting birthweight and graft survival in 197 pregnancies in cyclosporine-treated female kidney transplant recipients.

Outcomes from 197 pregnancies in 141 female kidney transplant recipients were analyzed from data collected via questionnaires, hospital records, and phone interviews. All recipients were maintained on cyclosporine (CsA) before and during pregnancy. Of the livebirths, 54% were premature (< 37 wk) and 50% were low-birthweight (LBW) (< 2500 g). The incidence of recipient drug-treated hypertension (HTN) was 56%; preeclampsia, 29%; infections and complications 22%; and rejection during pregnancy and up to 3 mo. post delivery (rej.), 11%. Graft loss within 2 years of delivery occurred in 9% of recipients (GrL < 2). No recipients reported a pregnancy after a postpregnancy graft loss. Mean serum creatinine was reported before, during, and after pregnancy. Mean cyclosporine doses were similar in recipients during and after pregnancy. Data were analyzed by logistic regression using SAS. Outcomes included prematurity, LBW, rej., and GrL < 2. In a case-controlled study comparing a recipient group with graft dysfunction during pregnancy vs. a group with good graft function, there was a trend toward lower mean prepregnancy CsA doses (in mg/kg) in the graft dysfunction group. A decline in recipient graft function during pregnancy is associated with lower newborn birthweights and lower maternal graft survival in cyclosporine treated female kidney recipients. Pregnancy-related infections and complications are associated with rejection and graft loss in this population. Close monitoring of CsA dosing and serum creatinine levels during pregnancy and immediately postpartum is recommended as CsA dosage adjustment may be required.

Endothelial cell transplantation onto polymeric arteriovenous grafts evaluated using a canine model.

Prosthetic arteriovenous grafts (AVG) placed for hemodialysis access fail in humans due to the thrombogenicity of the flow surface and development of cellular intimal hyperplasia, particularly at the venous anastomosis. The poor patency rates of prosthetic AVG result in significant morbidity and mortality in dialysis patients. Consequently, investigators have been evaluating methods to improve the patency of prosthetic grafts by examining endothelial cell transplantation as a means of creating an antithrombogenic lining on artificial polymers. A canine model was developed to study the effects of cell transplantation of autologous, fat-derived microvessel endothelial cells (MVEC) onto the luminal surface of expanded polytetrafluoroethylene (ePTFE) grafts. Microvessel endothelial cells were isolated from falciform ligament fat, with each dog receiving its own endothelial cells. Isolated cells were subsequently placed into the lumen of the graft (4 mm by 20 cm ePTFE). The graft lumen was pressurized to 5 pounds per square inch (psi) resulting in the partial denucleation of the graft, due to the flow of buffer into the interstices of the graft, and the forced deposition of cells onto the luminal surface. Animals were maintained on aspirin and persantine during the implant phase. During the implant phase, grafts were evaluated by both duplex ultrasound and magnetic resonance angiography (MRA). At explant, gross observation of the sodded grafts revealed a glistening white flow surface with no evidence of thrombosis. Morphologic and scanning electron microscopic evaluations revealed the presence of a cellular lining on the luminal flow surface that exhibited characteristics of antithrombogenic endothelial cells. Midgraft samples were evaluated by immunocytochemistry and indicated that cells on the luminal surface react positively with antibodies to von Willebrand factor. Results from this study demonstrate that the canine model provides an excellent method of studying the effects of MVEC sodding on the thrombogenicity and hyperplastic response of prosthetic arteriovenous graft.