Objectives: With limited deceased donor availability, living kidney donor transplantation remains the primary source of grafts in Tunisia. Strict donor selection criteria are essential to ensure donor safety and optimize recipient outcomes. We investigated the acceptance rate of living donor kidney transplant among eligible recipients and potential donors, enumerated the primary causes of donation discontinuation, and characterized the donor evaluation process at a single Tunisian transplant center.
Materials and Methods: We conducted a retrospective review of 70 patients with end-stage renal disease referred for living donor kidney transplant evaluation and 82 potential related living donors assessed between January 2020 and December 2024. Donor assessments adhered to Kidney Disease: Improving Global Outcomes clinical practice guidelines. The acceptance rate was defined as the proportion of recipient-donor pairs that proceeded to donor nephrectomy and allograft transplant. We computed descriptive statistics with SPSS version 26 software.
Results: Among 82 evaluated donors, 11 (13.4%) completed nephrectomy and transplant, 35 (42.7%) required supplementary diagnostic investigations, and 36 (43.9%) were excluded after multidisciplinary committee review. The median number (range) of donors assessed per recipient was 1 (1-2). In the 11 successful transplants, 8 recipients (72.7%) received transplants from the initial donor candidate, whereas 3 recipients (27.3%) required sequential evaluation of 2 or more candidates. The mean duration from initial donor workup to transplant was 526.9 ± 192.0 days. Among 36 discontinued cases, donor-related factors accounted for 26 instances (72.2%), immunological barriers for 8 instances (22.2%), and recipient-related factors for 1 instance (2.8%). After discontinuation, 1 of 36 recipients (2.8%) underwent deceased-donor transplant and 11 recipients (30.5%) remained on the national deceased-donor waiting list.
Conclusions: The observed acceptance rate of 13.4% reflects substantial barriers, predominantly donor-related contraindications identified during rigorous evaluation. Targeted interventions are needed to expand the donor pool in resource-constrained environments.

Key words : Donor evaluation, Donor-related discontinuation, Organ shortage

Introduction
Living kidney donor transplant (LKDT) constitutes the optimal renal replacement modality for patients with end-stage renal disease (ESRD), conferring improved graft longevity, patient survival, and quality of life compared with deceased-donor transplant or dialysis.^1,2 In settings characterized by constrained deceased donor organ availability, such as Tunisia, LKDT serves as the predominant graft source as a result of the persistent shortage of deceased donors.^3,4 However, contemporary donor selection protocols, as delineated in the 2017 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline,² require comprehensive medical, immunological, psychosocial, and anatomical assessments to ensure donor welfare while optimizing recipient outcomes.⁵ Despite these protective measures, strict donor selection criteria frequently lead to elevated exclusion rates and extended evaluation timelines.^6,7 In this study, we aimed to assess the objective acceptance rate of LKDT, elucidate the reasons of donation discontinuation, and report the timeline of the evaluation process within a single Tunisian transplant center over a 5-year interval.

Materials and Methods
This retrospective observational study was performed at the nephrology day-care unit. We systematically reviewed electronic and paper-based medical records of 70 consecutive ESRD patients referred for LKDT assessment and their corresponding 82 potential related living donors evaluated from January 1, 2020, to December 31, 2024. The study was approved by the institutional ethics and conducted in accordance with the 1975 Declaration of Helsinki (revised 2013). Informed consent was waived due to the retrospective nature and use of anonymized data. Donor evaluation followed KDIGO guidelines and institutional protocols² and included comprehensive medical history and physical examination, laboratory tests (serum creatinine, estimated glomerular filtration rate via the CKD-EPI equation, urinalysis, infectious serologies, immunological profiling), structural imaging (computed tomography angiography or magnetic resonance angiography), psychosocial assessment by a dedicated psychiatrist, and final multidisciplinary transplant committee approval. The acceptance rate was operationally defined as the percentage of recipient-donor pairs that ultimately proceeded to laparoscopic donor nephrectomy and subsequent allograft implantation. Causes of discontinuation were prospectively classified as donor-related (medical contraindications or anatomical unsuitability), immunological (ABO blood group incompatibility, elevated panel-reactive antibody levels, or positive complement-dependent cytotoxicity crossmatch), and recipient-related (clinical deterioration or contraindications to transplant). We used SPSS statistical software version 26 for all data extraction and analyses. We expressed continuous variables as mean ± SD or median (interquartile range or full range) and categorical variables as absolute frequencies and percentages. No inferential statistics were applied due to the descriptive nature of the study.

Results
During the observation period, 82 potential living kidney donors underwent formal evaluation on behalf of 70 recipients with ESRD (Table 1).

Outcomes of donor evaluation
Eleven donors (13.4%) successfully completed the evaluation process and proceeded to donor nephrectomy with immediate transplant to the intended recipient. Thirty-five donors (42.7%) required supplementary diagnostic investigations or specialist consultations to clarify eligibility. Thirty-six donors (43.9%) were permanently excluded after formal multidisciplinary transplant committee review. The distribution of these outcomes is presented in Figure 1.

Number of donors per recipient
The median number of potential donors subjected to at least partial evaluation per recipient was 1 (interquartile range, 1-2), with a maximum of 5 donors evaluated in 1 recipient. Within the subgroup of recipients who ultimately received a living donor allograft (n = 11), 8 recipients (72.7%) were transplanted using the first evaluated donor, whereas 3 recipients (27.3%) required further evaluation and workup of 2 or more potential donors before a suitable pair was identified.

Time to transplant
Among the 11 successful living donor transplants, the mean interval from initiation of the first donor’s evaluation workup to the date of transplant was 526.9 ± 192.0 days. The maximum time to surgery was 849 days.

Reasons for donation discontinuation
Donation was discontinued in 36 cases. The principal causes were categorized as follows: donor-related factors in 26 cases (72.2%), immunological incompatibilities in 8 cases (22.2%), recipient-related factors in 1 case (2.8%), and withdrawal of consent in 1 case (2.8%) (Table 2).

Trajectories after discontinuation
Among the 36 cases with discontinuation of the living donor pathway, 1 recipient (2.8%) subsequently received a deceased donor kidney transplant, and 11 recipients (30.5%) remained actively listed on the national deceased donor kidney transplant wait list at the end of the observation period. No perioperative or immediate postoperative complications were reported in the 11 donors who underwent nephrectomy or in the corresponding recipients (detailed long-term graft and patient outcomes are beyond the scope of this descriptive analysis).

Discussion
This single-center analysis highlighted a modest LKDT acceptance rate of 13.4%, with a notably considerable donor exclusion proportion of 43.9%. These findings aligned with contemporary single-center reports in which rigorous, guideline-directed evaluation protocols uncovered previously unrecognized medical comorbidities (hypertension, impaired glucose regulation, renal parenchymal anomalies) that led to exclusion rates ranging from 20% to over 50%.^6-12 Donor-related contraindications predominated as the foremost reason for discontinuation (72.2%), concordant with prior investigations that underscored medical and surgical impediments as principal barriers to donation.⁶ For example, a Swiss 15-year cohort attributed 32.7% of declines primarily to kidney-specific medical issues, with immunological factors comprising 21.1%.⁵ Similarly, a German single-center series documented donor medical contraindications in 50.7% of disqualified pairs.⁷ Immunological obstacles, although less frequent in our cohort (22.2%), remained significant, as seen in other reports where ABO incompatibility or crossmatch positivity contributed substantially.^2,8,13 Recipient-related issues remained rare (2.8%), consistent with extant literature, wherein such factors assumed secondary importance.¹¹ In our study, the median number of donors assessed per recipient was 1 (interquartile range, 1-2), with a maximum of 5 potential donors, consistent with most single-center and multicenter reports where the median is typically 1 to 2 (1.30 ± 0.66 donors per recipient in a large Korean series,¹³ 67% to 75% of recipients with only 1 candidate in a US study¹⁴). The Stanford experience similarly showed 61% of recipients with a single prospective donor, reflecting the common limitation in donor availability.¹² The necessity for multiple donor evaluations in 27.3% of successful transplantations, coupled with an extended mean interval to transplant (~28 months), suggest logistical challenges that may discourage potential donors or delay access, a common issue in settings with resource constraints.^6,11 Among the 36 cases with discontinuation of donors, only 11 patients (30.6%) were wait-listed for a deceased donor transplant, and just 1 patient received such a graft. The other 25 recipients (69.4%) were not wait-listed; these patients continued searching for a new donor or were lost to follow-up. This pattern was consistent with the literature, in which limited transition to deceased donor lists after living donor failure was shown but with different reasons; these reasons were mainly due to successful alternative living donation, recipient deterioration, withdrawal, or lost to follow-up.^5,13 Our findings underscore the value of living donor programs in reducing reliance on deceased donor waiting lists, while highlighting the need for improved postevaluation follow-up to optimize access to deceased donor transplant when needed. Compared with international data, the acceptance rate shown in our study was inferior to averages reported in multicenter registries (36% to 50%) or in select high-volume centers (15% in certain US programs, up to 24.7% in South Africa, and 28.4% in Switzerland).^5,11,13-15 The incidental detection of occult chronic conditions during donor assessment conferred a salutary benefit by facilitating early therapeutic intervention for the donor candidate, although at the expense of diminished acceptance rates. Principal limitations of this study included its retrospective design, single-center nature, and modest cohort size, thereby limiting generalizability. Prospective multicenter studies, particularly within similar deceased-donor shortage contexts, could provide broader insights and help identify modifiable barriers to improve LKDT use in Tunisia.

Conclusions
In this single-center retrospective analysis, the acceptance rate for living kidney donor transplantation was 13.4%, reflecting strict donor evaluation criteria that resulted in a high exclusion rate (43.9%). Donor-related factors constituted the predominant cause of discontinuation (72.2%), frequently revealing previously unrecognized medical conditions that prioritize donor safety but limit transplant opportunities. Immunological barriers accounted for 22.2% of discontinuations, and barrier to donation as a result of recipient-related factors was low (2.8%). Among recipients whose living donor pathway was discontinued, 1 patient subsequently underwent deceased-donor kidney transplant; the remaining 11 patients remained active on the national deceased-donor waiting list. These findings underscored the challenges of living donor utilization in a resource-constrained setting and emphasized the need for targeted strategies to enhance donor screening efficiency, address modifiable barriers, and improve access to transplant while maintaining rigorous safety standards for both donors and recipients.