Abstract
Background/Aim: Lower urinary tract symptoms (LUTS) are common symptoms after kidney transplantation (KT). This study investigated the factors affecting the quality of life (QOL) of patients with LUTS after KT.
Patients and Methods: We enrolled 46 patients with LUTS who visited our institution after KT between 2020 and 2021. In addition to clinical information obtained from medical charts [patient age, sex, body mass index, duration of dialysis, and Charlson Comorbidity Index (CCI) before KT, information related to LUTS was collected, including International Prostate Symptom Score (IPSS), IPSS-QOL score, nocturia-QOL (N-QOL) score, uroflowmetry, and bladder diary. The patients were divided into groups according to IPSS score (≥8 and <8, respectively).
Results: The median age in both groups was 55 years. Charlson comorbidity index (CCI) ≥2 or duration of dialysis did not differ significantly between groups (p=0.27 and 0.91, respectively). The total N-QOL score and daytime and nighttime urinary frequency were significantly higher in the IPSS ≥8 group compared with the IPSS <8 group (p=0.034, 0.048, and 0.021, respectively). In multivariate analysis, CCI 32 was an independent prognostic factor for severe IPSS-QOL score and total IPSS (p=0.040 and p=0.030, respectively), N-QOL score <80 was an independent prognostic factor for severe IPSS-QOL score (p=0.039), while nocturia was an independent prognostic factor for moderate or severe total IPSS (p=0.046).
Conclusion: Preoperative interventions for complications may lead to improved QOL in patients undergoing KT. The risk factors for LUTS after KT are nocturia and low N-QOL scores. Finally, treatment of nocturia can improve LUTS.
Introduction
Kidney transplantation (KT) is a renal replacement therapy for patients with end-stage renal disease (ESRD), with outcomes that have improved owing to advances in immunosuppressant therapy. Although patients with end-stage renal disease (ESRD) experience decreased bladder capacity and compliance as the dialysis period increases, they adapt to changes in urine volume and recover storage and voiding functions after KT (1, 2). Lower urinary tract symptoms (LUTS) are common in patients after KT (3). Approximately 40% of patients experience urinary frequency, and approximately 60% experience nocturia (3). Tsaur et al. reported a high incidence of urinary dysfunction among older male patients after KT (4). With the aging KT recipient population, the incidence of LUTS is expected to increase. Mitsui et al. reported that risk factors for LUTS after KT were diabetes mellitus and older age (5). While the presence or absence of LUTS did not affect patient quality of life (QOL), nocturnal polyuria was associated with reduced QOL. Moreover, we previously demonstrated that nocturnal polyuria, poor sleep quality, and aging may lead to poor QOL in patients with nocturia after KT (6). In contrast, an investigation of LUTS among 150 patients after KT showed that 87% had more than six voids/day, while 93% showed nocturia (7). However, most of the patients were satisfied with their post-KT QOL. Thus, the risk factors for LUTS remain controversial. Therefore, the present study investigated factors affecting the QOL of patients with LUTS after KT.
Patients and Methods
Patient selection and data collection. This study was approved by the Ethics Review Board of Nara Medical University Hospital (approval number: 3986). Written informed consent was obtained from all participants after they had received an explanation of the study objectives and protocol. Between January 2002 and December 2021, 198 patients underwent KT at our institute, almost all of whom were followed up. During the study registration period (September 2020 to December 2021), 47 patients were enrolled. Of these 47 patients, one was excluded due to a lack of data. Finally, we analyzed data from the remaining 46 patients. Clinical information was obtained from medical charts, including age, sex, body mass index, duration of dialysis, and Charlson Comorbidity Index (CCI) before KT. The following information related to LUTS was obtained: International Prostate Symptom Score (IPSS), IPSS-QOL score, nocturia-QOL score (N-QOL), uroflowmetry, and a bladder diary.
Assessment of questionnaires, uroflowmetry, and bladder diary. IPSS was classified as mild (score 0-7), moderate (8-19), or severe (≥20). The IPSS-QOL was classified as mild (score 0-1), moderate (2-4), or severe (5-6). The N-QOL was composed of sleep/energy, bother/concern, and global QOL questions. The total score was calculated on a scale of 0-100, where 100 indicated the highest QOL. The bladder diary included 24-h urine volume, daytime and nighttime urinary frequency, and nocturnal urine volume data. The nocturnal polyuria index (NPi) was defined as nocturnal urine volume/24-h urine volume. Nocturnal polyuria was defined as NPi >0.20 in patients aged ≤65 years and NPi >0.33 in patients >65 years. Uroflowmetry was used to assess voiding function based on the maximum flow rate (Qmax), voided volume, and post-void residual.
Statistical analysis. All data were recorded in Microsoft Excel. Continuous variables are presented as medians and interquartile ranges, while categorical variables are presented as numbers and percentages. We compared various parameters between groups of patients with IPSS ≥8 and <8 by using the Mann-Whitney U or Fisher’s exact tests. Multivariate logistic regression analysis was performed to evaluate preoperative and postoperative prognostic factors for poor IPSS and IPSS-QOL. All statistical tests were two-sided, with p<0.05 considered statistically significant. All data were analyzed using EZR version 1.55 (Saitama Medical Center, Jichi Medical University, Saitama, Japan).
Results
Comparison between the IPSS ≥8 and IPSS <8 groups. Table I shows a comparison of clinical information between patients with IPSS ≥8 (n=20) and IPSS <8 (n=26). The median age in both groups was 55 years (p=0.33). The IPSS ≥8 group consisted of 12 men and 8 women and the IPSS <8 group included 18 men and 8 women (p=0.55). The proportion of patients with CCI ≥2, duration of dialysis, and preemptive KT did not differ significantly between groups (p=0.27, 0.91, and 1.0, respectively). The total N-QOL score and daytime and nighttime urinary frequencies were significantly higher in the IPSS ≥8 group than those in the IPSS <8 group (p=0.034, 0.048, and 0.021, respectively). However, the 24 h urine volume, Qmax, PVR, and NPi did not differ significantly between groups (p=0.49, 0.46, 0.26, and 0.85, respectively).
Comparison of patient characteristics between the group with International Prostate Symptom Score (IPSS) ≥8 and <8.
Prognostic preoperative factors associated with severe symptoms according to IPSS-QOL score and IPSS. Table II shows the results of the multivariate analysis of preoperative prognostic factors for severe symptoms according to IPSS-QOL score and total IPSS. CCI 32 was an independent prognostic factor for severe IPSS-QOL score and total IPSS [odds ratio (OR)=10.20, 95% confidence interval (CI)=1.11-92.90, p=0.040, and OR=18.60, 95%CI=1.34-259.00, p=0.030, respectively]. Table III shows the results of the multivariate analysis of postoperative prognostic factors for severe symptoms according to IPSS-QOL score, in which N-QOL score <80 was an independent prognostic factor for severe IPSS-QOL score (OR=14.70, 95%CI=1.14-190.00, p=0.039). Table IV summarizes the results of the multivariate analysis of postoperative prognostic factors for moderate to severe symptoms according to IPSS, in which nocturia was an independent prognostic factor for moderate or severe total IPSS (OR=7.04, 95%CI=1.04-47.80, p=0.046).
Multivariate analyses for preoperative factors associated with severe symptoms according to International Prostate Symptom Score (IPSS)-quality of life (QOL) score and IPSS.
Multivariate analyses for postoperative factors associated with severe symptoms according to International Prostate Symptom Score (IPSS)-quality of life (QOL).
Multivariate analyses for postoperative factors associated with moderate to severe symptoms according to International Prostate Symptom Score (IPSS).
Table V shows the incidence of complications among patients. Myocardial infarction and congestive heart failure were observed in four and two patients, respectively. Diabetes mellitus was the most common comorbidity (n=10).
Complications.
Discussion
The results of the present study demonstrated lower N-QOL scores and higher daytime and night-time urinary frequencies among patients with moderate to severe IPSS than those with mild IPSS. Increased daytime frequency and nocturia are the main LUTS after KT (7). Nakamura et al. suggested that improving nocturia-specific QOL may contribute to better overall QOL in patients after KT (8). Multivariate analysis revealed that comorbidities were associated with severe IPSS-QOL score and IPSS. Tsunoyama et al. reported decreased maximum cystometric capacity and compliance with increasing dialysis period (9). However, dialysis period and preemptive kidney transplantation (PEKT), which are related to cystometric capacity, were not risk factors for LUTS in the present study. A population-based cohort study identified LUTS as a marker of increased risks of diabetes mellitus and heart disease among obese men and women (10). Ponholzer et al. suggested that vascular risk factors, such as diabetes mellitus, hypertension, hyperlipidemia, and smoking, play a role in the development of LUTS in both sexes (11). Preoperative interventions for lifestyle diseases and comorbidities can improve LUTS after KT. Since diabetes mellitus and heart disease were prevalent in our study, treatment is important to improve LUTS.
Multivariate analysis revealed the associations of low N-QOL scores with severe IPSS-QOL, and nocturia with moderate-to-severe IPSS. Several reasons may explain the high incidence of nocturia in patients after KT, including increased food intake after transplantation, changes in circadian urine production in the transplanted kidneys, and comorbidities (7). Almost 50% of patients in the present study complained of frequency, and 62% of nocturia after KT, and they tended to accept high frequency and nocturia more readily than the general population (3). However, our findings suggest that nocturia may cause decreased QOL; therefore, interventions for nocturia are warranted. A prospective cohort study of community-dwelling individuals aged ≥65 years reported that three or more nocturia episodes were associated with increased fall risk [relative risk (RR)=1.28] (12). Falls can cause hip and head injuries, as well as increased mortality (13). Thus, improving nocturia can not only improve QOL but can also reduce the risk of falls, injuries, and mortality. The causes of nocturia include overactive bladder, low bladder capacity, excessive water intake, and sleep disorders (14). Zermann et al. reported daily urinary volumes of >2,000 ml and 3,000 ml after KT in 79% and 18% of patients, respectively (7). Patients are typically instructed to increase their water intake after KT, which may lead to nocturia. In the present study, nocturnal polyuria was observed in 86% of patients. Although we were unable to assess daily water intake, some patients may have had excessive water consumption. Yamanaga et al. suggested an optimal range of daily water intake for patients after KT of 1,000-2,000 ml (15). Therefore, medical staff should instruct patients to avoid excessive water intake. Furthermore, nocturia is associated with lifestyle-related diseases such as diabetes mellitus, hypertension, heart disease, and obesity (16-20). Interventions for lifestyle diseases and comorbidities can improve LUTS and nocturia after KT. Since diabetes mellitus and heart disease were prevalent in our study, preoperative glycemic control and assessment of cardiovascular risk may be useful interventions. A review of cardiovascular management in patients with ESRD reported that all KT candidates should undergo echocardiography, and those with left ventricular systolic dysfunction should begin medical treatment (21).
Study limitations. For instance, the sample size was small and was conducted at a single institution; therefore, raising the possibility of selection bias. Moreover, owing to the cross-sectional design, the period of investigation after KT varied among patients. Additionally, preoperative urinary function could not be evaluated, making it unclear whether urinary dysfunction existed before KT.
Conclusion
The results of the present study suggest that preoperative treatment of complications in KT recipients may lead to improved QOL in patients with LUTS. The risk factors for LUTS after KT are nocturia and low N-QOL scores, and treating nocturia can improve LUTS.
Acknowledgements
The Authors would like to thank all patients who participated in this study for their important contributions. The Authors would also like to thank Mariko Yoshimura (Department of Urology, Nara Medical University, Nara, Japan) for invaluable help with obtaining and summarizing the data used in this study.
Footnotes
Authors’ Contributions
SH, AT, DG and KF contributed to conception and design, acquisition of patient data and analysis and interpretation of data. SH, TY, KI and MT performed the treatment. KO and YM contributed to acquisition and interpretation of data. YN, MM and NT contributed to the analysis and interpretation of data. All Authors have been involved in drafting the manuscript and revising it critically for important intellectual content and approved the version to be published. All Authors have participated sufficiently in this work to take public responsibility for appropriate portions of the content.
Conflicts of Interest
The Authors declare no conflicts of interest in relation to this study.
Funding
No funding was obtained for the present study.
Artificial Intelligence (AI) Disclosure
No artificial intelligence (AI) tools, including large language models or machine learning software, were used in the preparation, analysis, or presentation of this manuscript.
- Received December 10, 2025.
- Revision received December 22, 2025.
- Accepted December 29, 2025.
- Copyright © 2026 The Author(s). Published by the International Institute of Anticancer Research.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).
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