Objectives: We evaluated the long-term outcomes of kidney transplants performed using grafts that contain simple renal cysts, to determine whether these cysts constitute a barrier to kidney donation or transplant.
Materials and Methods: All kidney transplants performed by our team from February 2012 to May 2025 were retrospectively reviewed. Cases in which the graft contained at least 1 simple renal cyst were included. Demographic characteristics, cyst size, perioperative complications, postoperative renal function, and cyst size during follow-up ultrasonography were recorded. Postoperative serum creatinine levels were analyzed on day 1, week 1, month 1, and year 1. Changes in cyst size and the need for intervention were assessed.
Results: A total of 66 kidney transplants involving grafts with simple cysts were included. The mean age of recipients was 50.2 years, and 38 were female recipients. The mean cyst diameter was 14.5 ± 8.3 mm. Eight (12.1%) grafts contained cysts smaller than 5 mm, 18 (27.3%)grafts had cysts between 5 and 10 mm, and 40 (60.6%) grafts had cysts larger than 10 mm. No intraoperative complications occurred in donors or recipients. Early postoperative urinary tract infection developed in 9 patients but resolved completely with intravenous antibiotic therapy. At postoperative month 6, 44 patients demonstrated a decrease in cyst size, whereas 15 patients showed an increase. Only 1 patient required surgical excision due to cyst enlargement exceeding 5 cm. Mean serum creatinine levels on postoperative day 1, week 1, month 1, and year 1 were 2.48, 1.42, 1.23, 1.42 mg/dL, respectively.
Conclusions: Simple cysts in kidney grafts do not constitute a contraindication to kidney donation or transplant. When managed in experienced transplant centers and followed regularly, grafts containing simple renal cysts demonstrate favorable outcomes with low complication rates.

Key words : Graft function, Kidney transplantation, Living donor evaluation

Introduction
Living kidney donor candidates undergo a comprehensive evaluation before donation to minimize postoperative morbidity and long-term renal impairment. With the routine use of computed tomography angiography in donor assessment, incidental anatomic findings have become increasingly common, among which simple renal cysts are one of the most frequently encountered abnormalities. Simple (Bosniak category I) renal cysts are highly prevalent in the general population, increase with age, and are generally considered benign with minimal malignant potential.^1-3 Although simple renal cysts are often regarded as clinically insignificant, some studies have suggested that the presence of simple renal cysts may be associated with early markers of renal injury, including reduced estimated glomerular filtration rate, microalbuminuria, or hypertension.^4-6 In contrast, other investigations have demonstrated no meaningful association between simple cysts and renal function, suggesting that these findings may represent benign, age-related structural changes without clinical consequence.^7-9 As a result, the true clinical effect of simple renal cysts on donor selection and transplant outcomes remains uncertain. The influence of donor renal cysts on posttransplant outcomes has not been fully clarified. Recent studies evaluating living kidney donors have reported that simple cysts do not independently impair donor renal recovery or adversely affect allograft survival in recipients.^10,11 However, available data remain limited, long-term cyst behavior after transplant is not well characterized, and donor management practices vary among transplant centers. Consequently, concerns persist regarding the potential enlargement of cysts, parenchymal compression, or later complications in grafts containing simple cysts. In this study, we aimed to evaluate postoperative outcomes, longitudinal cyst changes, and graft function in kidney transplant recipients who had received grafts containing simple renal cysts. Our goal was to address existing uncertainties and contribute evidence regarding the safety and long-term behavior of cyst-bearing donor kidneys in clinical practice.

Materials and Methods
This retrospective study included kidney transplants performed at Başkent University Transplantation Center from February 2012 to May 2025. Only transplant recipients who received grafts containing simple renal cysts were evaluated. Donor and recipient demographic characteristics, cyst size and number, perioperative findings, postoperative renal function, complications, and ultrasonography follow-up of cyst dimensions were collected from institutional medical records. The study was approved by the Institutional Ethics Committee of Başkent University, and all procedures conformed to the principles of the 1975 Declaration of Helsinki and its later revisions. Because of the retrospective design, additional informed consent was waived; however, all patient data were anonymized before analysis. Kidney grafts were included only if the cysts were radiologically classified as simple (Bosniak category I) on preoperative ultrasonography or computed tomography (Figure 1). Cases with complex cysts, polycystic kidney disease, malignancy suspicion, or incomplete data were excluded. This classification was performed according to established definitions of simple renal cysts. For each donor, the age, sex, donor type, laterality of nephrectomy, cyst characteristics, and preoperative imaging findings were recorded. Recipient variables included age, sex, etiology of end-stage renal disease, preoperative serum creatinine, and postoperative serum creatinine values measured on postoperative day 1, week 1, month 1, and year 1. Early postoperative complications, particularly urinary tract infections, were also documented. Follow-up ultrasonography at postoperative month 6 was evaluated to determine changes in cyst size, regression or progression of cysts, and the need for intervention. Simple renal cysts generally did not undergo intraoperative manipulation. Donor nephrectomies were performed according to the standard technique of our center, and cyst excision or fenestration was not routinely performed except at the surgeon’s discretion for significantly enlarged cysts. In this cohort, only 1 cyst larger than 5 cm required excision; all other cysts were managed conservatively. We used SPSS software for statistical analyses. We expressed continuous variables as mean values (±SD) or median values (with interquartile range) and categorical variables as frequencies (with percentage). Group comparisons were conducted using the Student t test, Mann-Whitney U test, or the χ2 test, as appropriate. P < .⁰⁵ was considered statistically significant.

Results
A total of 66 living donor kidney transplant recipients with grafts containing simple renal cysts were included in the study. The mean age of the recipients was 50.3 ± 10.6 years, and 38 (57.6%) were female participants. All grafts contained at least 1 simple cortical cyst. Among the 27 donors for whom precise measurements were available, the mean cyst diameter was 14.5 ± 8.3 mm (range, 3-37 mm). When categorized by size, 8 grafts (12.1%) had cysts <5 mm, 18 grafts (27.3%) had cysts between 5 and 10 mm, and 40 grafts (60.6%) had cysts larger than 10 mm (Table 1). No intraoperative complications occurred in either donors or recipients (Figure 2). In the early postoperative period, 55 patients (83.3%) had no complications. Urinary tract infection developed in 9 recipients (13.6%), and macroscopic hematuria was observed in 1 patient (1.5%). All infections resolved with intravenous antibiotic therapy, and none required surgical intervention. Ultrasonography evaluation at postoperative month 6 was available in 60 patients. A reduction in cyst size was observed in 44 recipients (73.3%), no change in 1 recipient (1.7%), and an increase in 15 recipients (25.0%). Among the patients with cyst enlargement, only 1 patient (1.5% of the entire cohort) exhibited cyst growth to >5 cm, and cyst excision was performed. All other cyst enlargements were managed conservatively without further intervention. Renal function demonstrated steady improvement and stabilization over time. Mean serum creatinine levels were 2.48 ± 1.24 mg/dL on postoperative day 1, 1.42 ± 0.83 mg/dL at week 1, 1.23 ± 0.54 mg/dL at month 1, 1.38 ± 0.70 mg/dL at month 3, and 1.43 ± 0.70 mg/dL at 1 year. Comparison of 1-year creatinine levels across cyst-size groups (<5 mm, 5-10 mm, >10 mm) revealed no significant difference (Kruskal-Wallis, P = .³⁰¹). Likewise, no significant difference was found between patients with cyst regression and patients with cyst progression at 6 months (Mann-Whitney U test, P = .⁷³⁸). During the study period, no graft loss occurred, and graft function remained stable in all patients.

Discussion
In this study, we evaluated the clinical outcomes of living donor kidney transplants using grafts that contained simple cortical renal cysts. Our results demonstrated that transplant of kidneys with simple cysts is safe, with low postoperative complication rates and stable allograft function throughout follow-up. Notably, most cysts decreased in size after transplant, and only 1 patient required surgical intervention due to cyst enlargement, which supports the clinical acceptability of these grafts. Simple renal cysts are common, particularly in older individuals, and are generally considered benign findings with minimal clinical significance. Large cohort studies have confirmed that the prevalence of simple cysts increases with age and does not necessarily indicate underlying kidney disease.^12,13 Prior work has also suggested that simple cysts rarely undergo malignant transformation and are classified as low-risk lesions according to established radiology criteria.⁷ The findings of our study align with recently published data that have previously addressed the effect of donor kidney cysts on transplant outcomes. Emmons and colleagues evaluated 860 living donor kidney transplants and reported that the presence of renal cysts, whether on the donated or retained kidney, was not associated with inferior donor renal recovery or with worse allograft survival in recipients.¹⁴ Similarly, Waldram and colleagues assessed long-term renal function among 454 living kidney donors and found no significant difference in estimated glomerular filtration rate trajectories between donors with and without simple renal cysts over a median of 7.8 years of follow-up.¹¹ Our results are consistent with these findings, further supporting the notion that simple renal cysts should not be considered contraindications to live kidney donation. In the present study, cyst size categories (<5 mm, 5-10 mm, >10 mm) showed no significant correlation with 1-year serum creatinine levels, and patients with cyst enlargement at 6 months had similar renal function compared with patients who experienced cyst regression. These findings are supported by studies demonstrating that simple cysts may grow slowly over time but generally do not impair renal architecture or function.¹⁵ Moreover, the observed tendency for cyst regression after transplant may reflect improvements in renal perfusion and hemodynamic stability in the grafted kidney. Postoperative complications in our cohort were minimal and comparable with standard living donor transplant outcomes previously reported in the literature. Importantly, there were no cases of graft loss, underscoring the notion that the presence of simple cysts does not compromise graft viability or early function. These results align with previous data that have demonstrated excellent short-term and mid-term outcomes in recipients who received kidneys with incidental cysts.¹⁶ Our study had certain limitations. Its retrospective design may introduce selection bias. In addition, the follow-up period does not capture long-term cyst behavior beyond 1 year. Nevertheless, the consistency of our findings with large, high-quality external cohorts enhances the robustness and generalizability of the conclusions. In summary, our findings indicated that simple cortical cysts in living donor kidneys do not adversely affect transplant outcomes. When evaluated appropriately and transplanted in experienced centers, kidneys with simple cysts provide excellent graft survival and stable renal function. These results support the broader utilization of grafts with simple renal cysts and may help expand the living donor pool without compromising safety.

Conclusions
Our study demonstrated that simple cortical renal cysts in living donor kidneys do not adversely affect short-term or mid-term transplant outcomes. Renal function remained stable, postoperative complications were minimal, and no graft losses occurred during follow-up. Most cysts regressed after transplant, and cyst enlargement rarely required intervention. These findings support the notion that simple renal cysts should not be considered a contraindication for living kidney donation. With careful preoperative evaluation and appropriate postoperative monitoring, kidneys with simple cysts can be safely utilized and thereby contribute to expansion of the living donor pool.