Does kidney transplantation with a standard or expanded criteria donor improve patient survival? Results from a Belgian cohort

BACKGROUND

Changes in recipient and donor factors have reopened the question of survival benefits of kidney transplantation versus dialysis.

METHODS

We analysed survival among 3808 adult Belgian patients waitlisted for a first deceased donor kidney transplant from 2000 to 2012. The primary outcome was mortality during the median waiting time plus 3 years of follow-up after transplantation or with continued dialysis. Outcomes were analysed separately for standard criteria donor (SCD) and expanded criteria donor (ECD) kidney transplants. We adjusted survival analyses for recipient age (20-44, 45-64 and ≥65 years), sex and diabetes as the primary renal disease.

RESULTS

Among patients ≥65 years of age, only SCD transplantation provided a significant survival benefit compared with dialysis, with a mortality of 16.3% [95% confidence interval (CI) 13.2-19.9] with SCD transplantation, 20.5% (95% CI 16.1-24.6) with ECD transplantation and 24.6% (95% CI 19.4-29.5) with continued dialysis. Relative mortality risk was increased in the first months after transplantation compared with dialysis, with equivalent risk levels reached earlier with SCD than ECD transplantation in all age groups.

CONCLUSIONS

The results of this study suggest that older patients might gain a survival benefit with SCD transplantation versus dialysis, but any survival benefit with ECD transplantation versus dialysis may be small.

P1630IS THERE ALWAYS A SURVIVAL BENEFIT WITH KIDNEY TRANSPLANTATION? RESULTS FROM A BELGIAN COHORT

Background and Aims

Older studies have shown a survival benefit with kidney transplantation compared to dialysis, even for patients older than 60 years. However, due to important evolutions such as older recipient age and the use of less-than-optimal quality donors, it is unclear if the survival benefit with transplantation still holds true nowadays.

Method

Patient survival was analyzed for 3808 Belgian patients waitlisted for a first deceased donor kidney transplant between 2000 to 2012. Patients were divided into age categories (20-44y, 45-64y, ≥65y). Primary outcome was the comparison of mortality during median waiting time plus 3 years follow-up, either after transplantation or when remaining on dialysis. Outcomes were analyzed separately for those receiving a standard criteria donor (SCD) or an expanded criteria donor (ECD) transplant. The survival analyses were adjusted for age, sex and primary renal disease.

Results

Among patients ≥ 65 years old, only SCD transplantation provided a significant survival benefit compared to dialysis: mortality was 16.3 % (95 % CI: 13.2–19.9 %) with SCD transplantation, 20.5 % (16.1–24.6 %) with ECD transplantation, and 24.6 % (19.5–29.5 %) when remaining on dialysis. Relative mortality risk was increased in the first months after transplantation compared to dialysis, with equal risk levels being reached earlier for SCD than ECD transplantations in all age groups.

Conclusion

This study suggests that older patients have a survival benefit with SCD transplantation versus dialysis, but the survival benefit with ECD transplantation versus dialysis may be small or non-existent.

Effect of donor nephrectomy time during circulatory-dead donor kidney retrieval on transplant graft failure

Background

When the blood supply ceases in a deceased organ donor, ischaemic injury starts. Kidneys are cooled to reduce cellular metabolism and minimize ischaemic injury. This cooling is slow and kidneys are lukewarm during nephrectomy. Smaller single-centre studies have shown that prolonged donor nephrectomy time decreases early kidney transplant function, but the effect on long-term outcome has never been investigated in large multicentre cohort studies.

Methods

The relationship between donor nephrectomy time and death-censored graft survival was evaluated in recipients of single adult-to-adult, first-time deceased-donor kidneys transplanted in the Eurotransplant region between 2004 and 2013.

Results

A total of 13 914 recipients were included. Median donor nephrectomy time was 51 (i.q.r. 39–65) min. Kidneys donated after circulatory death had longer nephrectomy times than those from brain-dead donors: median 57 (43–78) versus 50 (39–64) min respectively (P < 0·001). Donor nephrectomy time was independently associated with graft loss when kidneys were donated after circulatory death: adjusted hazard ratio (HR) 1·05 (95 per cent c.i. 1·01 to 1·09) per 10-min increase (P = 0·026). The magnitude of this effect was comparable to the effect of each hour of additional cold ischaemia: HR 1·04 (1·01 to 1·07) per h (P = 0·004). For kidneys donated after brain death, there was no effect of nephrectomy time on graft survival: adjusted HR 1·01 (0·98 to 1·04) per 10 min (P = 0·464).

Conclusion

Prolonged donor nephrectomy time impairs graft outcome in kidneys donated after circulatory death. Keeping this short, together with efficient cooling during nephrectomy, might improve outcome.

Family overrule of registered refusal to donate organs

It is well known that families frequently overrule the wishes of dying patients who had previously expressed a wish to donate their organs. Various strategies have been suggested to reduce the frequency of these 'family overrules'. However, the possibility of families overruling a patient's registered decision not to donate has not been discussed in the medical literature, although it is legally possible in some countries. In this article, we provide an ethical analysis of family overrule of a relative's refusal to donate, using the different jurisdictions of the UK, Switzerland, Germany and the Netherlands to provide some context. Despite some asymmetries between overruling consent and overruling refusal, there are some cases in which donation should proceed despite a recorded refusal to do so.

Optimizing the Use of Geriatric Livers for Transplantation in the Eurotransplant Region

Acceptance criteria for liver allografts are ever more expanding because of a persisting wait-list mortality. Older livers are therefore offered and used more frequently for transplantation. This study aims to analyze the use and longterm outcome of these transplantations. Data were included on 17,811 first liver transplantations (LTs) and information on livers that were reported for allocation but not transplanted from 2000 to 2015 in the Eurotransplant (ET) region. Graft survival was defined as the period between transplantation and date of retransplantation or date of recipient death. In the study period, 2394 (13%) transplantations were performed with livers ≥70 years old. Graft survival was 74%, 57%, and 41% at 1-, 5-, and 10-year follow-up, respectively. A history of diabetes mellitus in the donor (hazard ratio [HR], 1.3; P = 0.01) and positive hepatitis C virus antibody in the recipient (HR, 1.5; P < 0.001) are specific risk factors for transplantations with livers ≥70 years old. Although donor age is associated with a linearly increasing risk of graft loss between 25 and 80 years old, no difference in graft survival could be observed when "preferred" recipients were transplanted with a liver <70 or ≥70 years old (HR 1.1; CI 0.92-1.23, P = 0.40) or with a donor <40 or ≥70 years old (HR 1.2; CI 0.96-1.37, P = 0.13). Utilization of reported livers ≥70 years old increased from 42% in 2000-2003 to 76% in 2013-2015 without a decrease in graft survival (P = 0.45). In conclusion, an important proportion of LTs in the ET region are performed with livers ≥70 years old. The risk of donor age on graft loss increases linearly between 25 and 80 years old. Livers ≥70 years old can, however, be transplanted safely in preferred patients and are to be used more frequently to further reduce wait-list mortality.

Association between donor age and risk of graft failure after liver transplantation: an analysis of the Eurotransplant database

Grafts from elderly donors are increasingly used for liver transplantation. As of yet there is no published systematic data to guide the use of specific age cutoffs the effect of elderly donors on patient outcomes must be clarified. This study analyzed the Eurotransplant database (01/01/2000-31/07/2014; N = 26 294) out of whom 8341 liver transplantations were filtered to identify for this analysis. 2162 of the grafts came from donors >60 including 203 from octogenarians ≥80 years. Primary outcome was the risk of graft failure according to donor age using a confounder adjusted Cox-Regression model with frailty terms (or random effects). The proportion of elderly grafts increased during the study period [i.e., octogenarians 0.1% (n = 1) in 2000 to 3.4% (n = 45) in 2013]. Kaplan-Meier and Cox-analyses revealed a reduced survival and a higher risk for graft failure with increasing donor age. Although the age effect was allowed to vary non-linearly, a linear association hazard ratio (HR = 1.1 for a 10 year increase in donor age) was evident. The linearity of the association suggests that there is no particular age at which the effect increases more rapidly, providing no evidence for a cutoff age. In clinical practice, the combination of high donor age with HU-transplantations, hepatitis C, high MELD-scores and long cold ischemic time should be avoided.

Heart re-transplantation in Eurotransplant

Internationally 3% of the donor hearts are distributed to re-transplant patients. In Eurotransplant, only patients with a primary graft dysfunction (PGD) within 1 week after heart transplantation (HTX) are indicated for high urgency listing. The aim of this study is to provide evidence for the discussion on whether these patients should still be allocated with priority. All consecutive HTX performed in the period 1981-2015 were included. Multivariate Cox' model was built including: donor and recipient age and gender, ischaemia time, recipient diagnose, urgency status and era. The study population included 18 490 HTX, of these 463 (2.6%) were repeat transplants. The major indications for re-HTX were cardiac allograft vasculopathy (CAV) (50%), PGD (26%) and acute rejection (21%). In a multivariate model, compared with first HTX hazards ratio and 95% confidence interval for repeat HTX were 2.27 (1.83-2.82) for PGD, 2.24 (1.76-2.85) for acute rejection and 1.22 (1.00-1.48) for CAV (P < 0.0001). Outcome after cardiac re-HTX strongly depends on the indication for re-HTX with acceptable outcomes for CAV. In contrast, just 47.5% of all hearts transplanted in patients who were re-transplanted for PGD still functioned at 1-month post-transplant. Alternative options like VA-ECMO should be first offered before opting for acute re-transplantation.

The duration of asystolic ischemia determines the risk of graft failure after circulatory-dead donor kidney transplantation: A Eurotransplant cohort study

Circulatory death donor (DCD) kidney transplantations are steadily increasing. Consensus reports recommend limiting donor warm ischemia time (DWIT) in DCD donation, although an independent effect on graft outcome has not been demonstrated. We investigated death-censored graft survival in 18 065 recipients of deceased-donor kidney transplants in the Eurotransplant region: 1059 DCD and 17 006 brain-dead donor (DBD) kidney recipients. DWIT was defined as time from circulatory arrest until cold flush. DCD donation was an independent risk factor for graft failure (adjusted hazard ratio [HR] 1.28, 95% CI 1.10-1.46), due to an increased risk of primary nonfunction (62/1059 vs 560/17 006; P < .0001). With DWIT in the model, DCD donation was no longer a risk factor, demonstrating that DWIT explains the inferior graft survival of DCD kidneys. Indeed, DCD transplants with short DWIT have graft survival comparable to that of standard-criteria DBD transplants (P = .59). DWIT also associated with graft failure in DCDs (adjusted HR 1.20 per 10-minute increase, 95% CI 1.03-1.42). At 5 years after transplantation, graft failure occurred in 14 of 133 recipients (10.5%) with DWIT <10 minutes, 139 of 555 recipients (25.0%) with DWIT between 10 and 19 minutes, and 117 of 371 recipients (31.5%) with DWIT ≥20 minutes. These findings support the expert opinion-based guidelines to limit DWIT.

Reconditioning by end-ischemic hypothermic in-house machine perfusion: A promising strategy to improve outcome in expanded criteria donors kidney transplantation

This clinical study evaluates end-ischemic hypothermic machine perfusion (eHMP) in expanded criteria donors (ECD) kidneys. eHMP was initiated upon arrival of the kidney in our center and continued until transplantation. Between 11/2011 and 8/2014 eHMP was performed in 66 ECD kidneys for 369 (98-912) minutes after 863 (364-1567) minutes of cold storage (CS). In 49 of 66 cases, the contralateral kidney from the same donor was preserved by static CS only and accepted by another Eurotransplant (ET) center. Five (10.2%) of these kidneys were ultimately judged as "not transplantable" by the accepting center and discarded. After exclusion of early unrelated graft losses, 43 kidney pairs from the same donor were eligible for direct comparison of eHMP vs CS only: primary non-function and delayed graft function (DGF) were 0% vs 9.3% (P=.04) and 11.6% vs 20.9% (P=.24). There was no statistically significant difference in 1-year graft survival (eHMP vs CS only: 97.7% vs 88.4%, P=.089). In a multivariate analysis, eHMP was an independent factor for prevention of DGF (OR: 0.28, P=.041). Development of DGF was the strongest risk factor for 1-year graft failure (Renal resistance: 38.2, P<.001). In summary, eHMP is a promising reconditioning technique to improve the quality and acceptance rate of suboptimal grafts.

Higher retransplantation rate following extended right split-liver transplantation: An analysis from the eurotransplant liver follow-up registry

Split-liver transplantation has been perceived as an important strategy to increase the supply of liver grafts by creating 2 transplants from 1 allograft. The Eurotransplant Liver Allocation System (ELAS) envisages that the extended right lobes (ERLs) after splitting (usually in the pediatric center) are almost exclusively shipped to a second center. Whether the ELAS policy impacts the graft and patient survival of extended right lobe transplantation (ERLT) in comparison to whole liver transplantation (WLT) recipients remains unclear. Data on all liver transplantations performed between 2007 and 2013 were retrieved from the Eurotransplant Liver Follow-up Registry (n = 5351). Of these, 5013 (269 ERL, 4744 whole liver) could be included. The impact of the transplant type on patient and graft survival was evaluated using univariate and multivariate proportional hazard models adjusting for demographics of donors and recipients. Cold ischemia times were significantly prolonged for ERLTs (P < 0.001). Patient survival was not different between ERLT and WLT. In the univariate analysis, ERLT had a significantly higher risk for retransplantation (P = 0.02). For WLT, the risk for death gradually and significantly increased with laboratory Model for End-Stage Liver Disease (MELD) scores of >20. For ERLT, this effect was seen already with laboratory MELD scores of >14. These results mandate a discussion on how to refine the splitting policy to avoid excess retransplant rates in ERL recipients and to further improve transplant outcomes of these otherwise optimal donor organs. Liver Transplantation 24 26-34 2018 AASLD.

Conscientious objection to deceased organ donation by healthcare professionals

In this article, we analyse the potential benefits and disadvantages of permitting healthcare professionals to invoke conscientious objection to deceased organ donation. There is some evidence that permitting doctors and nurses to register objections can ultimately lead to attitudinal change and acceptance of organ donation. However, while there may be grounds for conscientious objection in other cases such as abortion and euthanasia, the life-saving nature of donation and transplantation renders objection in this context more difficult to justify. In general, dialogue between healthcare professionals is a more appropriate solution, and any objections must be justified with a strong rationale in hospitals where such policies are put in place.

The Impact of Anastomosis Time During Kidney Transplantation on Graft Loss: A Eurotransplant Cohort Study

Recent studies raised the concern that warm ischemia during completion of vascular anastomoses in kidney implantation harms the transplant, but its precise impact on outcome and its interaction with other risk factors remain to be established. We investigated the relationship between anastomosis time and graft survival at 5 years after transplantation in 13 964 recipients of deceased donor solitary kidney transplants in the Eurotransplant region. Anastomosis time was independently associated with graft loss after adjusting for other risk factors (adjusted hazard ratio [HR] 1.10 for every 10-min increase, 95% confidence interval [CI] 1.06-1.14; p < 0.0001), whereas it did not influence recipient survival (HR 1.00, 95% CI 0.97-1.02). Kidneys from donation after circulatory death (DCD) were less tolerant of prolonged anastomosis time than kidneys from donation after brain death (p = 0.02 for interaction). The additive effect of anastomosis time with donor warm ischemia time (WIT) explains this observation because DCD status was no longer associated with graft survival when adjusted for this summed WIT, and there was no interaction between DCD status and summed WIT. Time to create the vascular anastomoses in kidney transplantation is associated with inferior transplant outcome, especially in recipients of DCD kidneys.

Longterm results of liver transplantation from donation after circulatory death

Donation after circulatory death (DCD) liver transplantation (LT) may imply a risk for decreased graft survival, caused by posttransplantation complications such as primary nonfunction or ischemic-type biliary lesions. However, similar survival rates for DCD and donation after brain death (DBD) LT have been reported. The objective of this study is to determine the longterm outcome of DCD LT in the Eurotransplant region corrected for the Eurotransplant donor risk index (ET-DRI). Transplants performed in Belgium and the Netherlands (January 1, 2003 to December 31, 2007) in adult recipients were included. Graft failure was defined as either the date of recipient death or retransplantation whichever occurred first (death-uncensored graft survival). Mean follow-up was 7.2 years. In total, 126 DCD and 1264 DBD LTs were performed. Kaplan-Meier survival analyses showed different graft survival for DBD and DCD at 1 year (77.7% versus 74.8%, respectively; P = 0.71), 5 years (65.6% versus 54.4%, respectively; P = 0.02), and 10 years (47.3% versus 44.2%, respectively; P = 0.55; log-rank P = 0.038). Although there was an overall significant difference, the survival curves almost reach each other after 10 years, which is most likely caused by other risk factors being less in DCD livers. Patient survival was not significantly different (P = 0.59). Multivariate Cox regression analysis showed a hazard ratio of 1.7 (P < 0.001) for DCD (corrected for ET-DRI and recipient factors). First warm ischemia time (WIT), which is the time from the end of circulation until aortic cold perfusion, over 25 minutes was associated with a lower graft survival in univariate analysis of all DCD transplants (P = 0.002). In conclusion, DCD LT has an increased risk for diminished graft survival compared to DBD. There was no significant difference in patient survival. DCD allografts with a first WIT > 25 minutes have an increased risk for a decrease in graft survival. Liver Transplantation 22 1107-1114 2016 AASLD.

Donor risk indices in pancreas allocation in the Eurotransplant region

Pancreas donor selection and recognition are important to cope with increasing organ shortage. We aim to show that the PDRI is more useful than the P-PASS to predict acceptance and should thus be preferred over P-PASS. Eurotransplant donors from 2004 until 2014 were included in this study. PDRI logistical factors were set to reference to purely reflect donor quality (PDRI donor ). PDRI and P-PASS association with allocation outcome was studied using area under the receiver operating characteristic curve (AUROC). Regional differences in donor quality were also investigated. Of the 10 444 pancreata that were reported, 6090 (58.3%) were accepted and 2947 (28.2%) were transplanted. We found that P-PASS was inferior to PDRIdonor in its ability to predict organ reporting, acceptance, and transplantation: AUC 0.63, 0.67 and 0.73 for P-PASS vs. 0.78, 0.79 and 0.84 for PDRIdonor , respectively. Furthermore, there were significant differences in donor quality among different Eurotransplant countries, both in reported donors and in transplanted organs. PDRI is a powerful predictor of allocation outcome and should be preferred over P-PASS. Proper donor selection and recognition, and possibly a more liberal approach toward inferior quality donors, may increase donation and transplant rates.

Regulatory aspects of VCA in Eurotransplant

Vascularized composite allografts (VCAs) are a growing field within the area of transplantation. In 2014, the birth of a healthy baby after a successful uterus transplant from a living donor was reported in Sweden. VCAs are not specifically mentioned in any of the transplant acts of the Eurotransplant (ET) member states, which all belong to the European Union (EU). The Competent Authorities (CA) of the EU decided in 2012 that VCAs are to be regarded as organs. At the moment, there are no general guidelines in the ET area concerning wait list registration, allocation, procurement and transplantation, and also no regulations concerning reimbursement. To further develop this aspect, common policies and guidelines within the ET member states have to be developed.

Combined effect of donor and recipient risk on outcome after liver transplantation: Research of the Eurotransplant database

Recently the Eurotransplant donor risk index (ET-DRI) was published, a model based on data from the Eurotransplant database that can be used for risk indication of liver donors within the Eurotransplant region. Because outcome after liver transplantation (LT) depends both on donor and recipient risk factors, a combined donor-recipient model (DRM) would give a more complete picture of the overall risk involved. All liver transplants in adult recipients from January 1, 2008 to December 31, 2010 in the Eurotransplant region were included. Risk factors in donors and recipients for failure-free (retransplant free) survival were analyzed in univariate and multivariate analyses. A simplified recipient risk index (sRRI) was constructed using all available recipient factors. A total of 4466 liver transplants were analyzed. Median donor risk index and ET-DRI were 1.78 and 1.91, respectively. The ET-DRI was validated in this new cohort (P < 0.001; concordance index [c-index], 0.59). After construction of a simplified recipient risk index of significant recipient factors, Cox regression analysis showed that the combination ET-DRI and sRRI into a new DRM gave the highest predictive value (P < 0.001; c-index, 0.62). The combined model of ET-DRI and sRRI gave a significant prediction of outcome after orthotopic LT in the Eurotransplant region, better than the ET-DRI alone. This DRM has potential in comparing data in the literature and correcting for sickness/physical condition of transplant recipients. It is a first step toward benchmarking of graft survival in the Eurotransplant region.

Integrating data from multiple sources for data completeness in a web-based registry for pediatric renal transplantation--the CERTAIN Registry

Patient registries are a useful tool to measure outcomes and compare the effectiveness of therapies in a specific patient population. High data quality and completeness are therefore advantageous for registry analysis. Data integration from multiple sources may increase completeness of the data. The pediatric renal transplantation registry CERTAIN identified Eurotransplant (ET) and the Collaborative Transplant Study (CTS) as possible partners for data exchange. Import and export interfaces with CTS and ET were implemented. All parties reached their projected goals and benefit from the exchange.

Comparative analysis of assays for detection of cell-mediated immunity toward cytomegalovirus and M. tuberculosis in samples from deceased organ donors

Cell-mediated immunity assays could be valuable for risk assessment of organ donors, but no data exist on their feasibility in deceased donors. In this study, 105 deceased donors (52.3 ± 16.9 years) were screened at the time of organ procurement. Pathogen-specific stimulation was performed using a cytomegalovirus (CMV) lysate, tuberculin (purified protein derivative [PPD]) and soluble Mycobacterium tuberculosis-specific ESAT-6/CFP-10 proteins in combination with an in-house fluorescence-activated cell sorting (FACS) assay or commercial assay formats (QuantiFERON-CMV/TB for ELISA, T-SPOT.TB for ELISPOT). CMV-IgG antibody titers were determined as gold standard for CMV infection; 51.4% of samples were CMV seropositive. Indeterminate results were observed in 47.6% of ELISA, 12.5% of FACS and 0% of ELISPOT assays. Agreement with serology was highest for FACS (95.6%, κ = 0.91), followed by ELISPOT (84.0%, κ = 0.68) and ELISA (80.0%, κ = 0.60). Agreement between ELISA and serology increased if the CMV lysate was used as stimulus (96.7%, κ = 0.92). Among the T cell assays, agreement between ELISPOT and FACS was highest (κ = 0.70). PPD-positive results among valid samples differed between assays (26.5% for ELISA, 23.1% for FACS and 50.5% for ELISPOT); 2.0% were QuantiFERON-TB positive, 3.3% were ESAT-6/CFP-10-positive in FACS and 13.4% were positive in the T-SPOT.TB assay. In conclusion, cellular immunity may be analyzed from samples of deceased donors, although the assays differ in the rate of positivity and indeterminate results.

[Organ procurement in Germany: a regional survey among students]

BACKGROUND AND OBJECTIVE

In Germany the extent of organ donation is still low and not sufficent to duly address all patients on the waiting lists. It is likely that a lack of information and a consecutive uncertainty in the adult population relate to this imbalance. Virtually no data exist about teenagers' knowledge of the facts of organ donation.

METHODS

4000 questionnaires were distributed in secondary schools in the state capital city Mainz, Germany. The students were asked to respond to 12 questions. The survey was voluntary and performed in class, without the students using any information sources.

RESULTS

Data from 1155 questionnaires were analysed. Overall 11.3 % of the teenagers carried an organ donor card. 48.9 % of the students had spoken about organ donation and brain death in their families. 37.0 % of the students declined organ donation. Of these, 72.4 % named a lack of education and informations as the primary reason for this statement. More non-German than German pupils declined organ donation (43.4 % vs. 36.2 %).

CONCLUSIONS

More than half of the pupils between 14 years and 20 years of age support the concept of organ transplantation as therapeutic option. Nevertheless the proportion of organ card holders is small among these students. These regional results identify an information deficit in young people in Germany as one of the main causes for inadequate acceptance of organ donation. Therefore, information and structured education should be intensified in German schools as possible measure to increase the number of future organ donor card holders in Germany.

Prevention of catheter-related infections: the potential of a new nano-silver impregnated catheter

Contaminated or infected catheters are a major source of nosocomial infections responsible for >40% of all episodes of nosocomial sepsis in acute-care hospitals. Antibiotics as well as surface modifications with, for example, hydrogels proved to be of little value in preventing the contamination of indwelling catheters. The even distribution of 10(12-13) activated silver nanoparticles per gram in various polymers, e.g. polyurethane and silicone, results in an excellent antimicrobial activity against a broad spectrum of organisms in vitro. Substantial reduction of incrustation of these catheters was also observed. These preliminary experimental data warrant clinical studies.

Gap junctions are found between iris sphincter smooth muscle cells but not in the ciliary muscle of human and monkey eyes

Physiological studies indicate that in primate ciliary muscle there is little or no spread of electrical activity from cell to cell. To clarify to what extent primate intraocular smooth muscles express the structural correlate of electrical coupling, the localization of gap junctions in the ciliary and the iris sphincter muscle of human and monkey (Macaca fascicularis) eyes was analysed using electronmicroscopy and connexin43 immunocytochemistry. With both methods, numerous gap junctions were identified in the iris sphincter of both species, while no such junctions were observed between individual smooth muscle cells in the ciliary muscle. Both ciliary and iris sphincter smooth muscle cells were connected by numerous adherens-type junctions. These results further underline that primate ciliary muscle is an atypical smooth muscle which shares many common features with striated skeletal muscle.