European Journal of Cardiovascular Medicine

Recurrent urinary tract infection (rUTI) is a frequently encountered clinical entity among adult women and contributes substantially to outpatient consultations, microbiology testing, and antibiotic exposure. rUTI is commonly defined as ≥2 symptomatic infections within six months or ≥3 infections within one year, with each episode supported by compatible symptoms and bacteriological evidence [1,2]. The condition has a multifactorial basis involving behavioral factors, host susceptibility, uropathogen virulence, and alterations in the urogenital microbiome. Uropathogenic Escherichia coli remains the predominant pathogen and demonstrates specialized adhesins and immune evasion strategies that facilitate persistence and recurrence [3,4].

Although uncomplicated cystitis is generally considered a localized infection with excellent short-term outcomes, recurrent or frequent infections can create a sustained inflammatory state affecting the lower and, in some patients, the upper urinary tract. Repeated episodes can be associated with tubular injury, interstitial inflammation, and microvascular stress, particularly when infections ascend or remain untreated for prolonged durations [3,5]. In adult women, the impact of repeated infection on renal function is less commonly quantified than in paediatric populations, and subtle changes in filtration indices can remain clinically silent for years.

The kidney is central to blood pressure regulation through sodium handling, pressure natriuresis, and modulation of the renin–angiotensin–aldosterone and sympathetic nervous systems. Even mild parenchymal injury can be accompanied by endothelial dysfunction and impaired autoregulation, potentially contributing to elevated blood pressure and early hypertensive phenotypes [6,7]. Prior work has also demonstrated higher ambulatory blood pressure indices in women with infection-associated renal damage despite preserved global renal function, supporting a plausible link between recurrent infection, renal injury, and altered blood pressure profiles [8,9].

In routine clinical practice, management of rUTI often emphasizes acute infection control and strategies for recurrence prevention, whereas assessment of renal functional markers and blood pressure status is not consistently undertaken unless overt kidney disease is suspected. The present study was conducted in the Department of Microbiology, Government Siddhartha Medical College, Vijayawada, Andhra Pradesh, India, to evaluate renal function parameters and blood pressure regulation in adult women with rUTI compared with age-matched controls. The objectives of this study were to (i) compare serum creatinine, blood urea, eGFR, and UACR between groups, (ii) assess differences in systolic and diastolic blood pressure and hypertension prevalence, and (iii) examine the relationship between rUTI burden, albuminuria, and blood pressure indices.

Study design and setting

This hospital-based comparative study was conducted from November 2023 to March 2024 in the Department of Microbiology, Government Siddhartha Medical College, Vijayawada, Andhra Pradesh, India. The study compared adult women with rUTI and age-matched women without a history of rUTI (controls) using standardized clinical and laboratory measurements.

Study population and sample size

A total sample of 100 adult women was included. The rUTI group comprised 50 participants with a documented history of recurrent symptomatic UTI, whereas 50 women without a history of recurrent UTI served as controls. Participants were recruited from outpatient and inpatient services, and enrolment was continued until the planned sample size for each group was achieved.

Operational definitions

Recurrent UTI was defined as ≥2 symptomatic episodes in the preceding 6 months or ≥3 symptomatic episodes in the preceding 12 months, supported by prior clinical documentation and/or culture reports in accordance with widely used criteria [1,2]. Microalbuminuria was defined as a UACR of 30–300 mg/g and nephrotic-range albuminuria as UACR >300 mg/g [6]. Estimated glomerular filtration rate (eGFR) was calculated using a creatinine-based equation and expressed as mL/min/1.73 m².

Inclusion and exclusion criteria

Adult women aged ≥18 years were eligible. For the rUTI group, participants had a confirmed history of recurrent symptomatic UTI. Controls were age-matched women without a history of rUTI. Exclusion criteria included pregnancy, known chronic kidney disease diagnosed before enrolment, known structural renal abnormalities, current menstruation at the time of urine sampling, and acute systemic illnesses likely to affect renal function measurements.

Clinical assessment and blood pressure measurement

Demographic data and relevant clinical history were recorded, including diabetes status, smoking, and family history of hypertension. Anthropometry was performed to calculate body mass index (BMI). Blood pressure was measured in a seated position after rest using a calibrated sphygmomanometer. Three readings were obtained at 2–3 minute intervals and the mean of the last two readings was

used for analysis. Hypertension was defined as systolic BP ≥140 mmHg and/or diastolic BP ≥90 mmHg or current antihypertensive therapy [7].

Laboratory procedures

Blood samples were collected under aseptic precautions for serum creatinine and blood urea analysis. A clean-catch midstream urine specimen was collected for quantification of urinary albumin and creatinine, and the urine albumin–creatinine ratio (UACR) was calculated (mg/g). Participants were counselled on clean-catch collection to reduce contamination. Laboratory estimations were performed as per institutional standard operating procedures.

Statistical analysis

Data were entered and analyzed using standard statistical software. Continuous variables were summarized as mean ± standard deviation or median (interquartile range) based on distribution, and categorical variables as frequency and percentage. Between-group comparisons used Student’s t-test or Mann–Whitney U test for continuous variables and chi-square/Fisher’s exact test for categorical variables. Correlations were assessed using Pearson’s r or Spearman’s rho as appropriate. Multivariable linear regression was used to evaluate independent associations of rUTI status with eGFR and systolic BP after adjustment for age, BMI, and diabetes. Logistic regression was used to estimate adjusted odds for microalbuminuria. A p value <0.05 was considered statistically significant.

Ethical considerations

The study protocol was conducted in accordance with ethical principles for human research. Written informed consent was obtained from all participants prior to enrolment, and confidentiality of participant information was maintained.

A total of 100 adult women were included and analysed. Fifty participants had recurrent urinary tract infections (rUTI group, n = 50) and 50 age-matched women without rUTI served as controls (control group, n = 50). The mean age was comparable between groups (rUTI: 39.6 ± 9.8 years; controls: 38.9 ± 10.1 years; p = 0.74). The median duration of rUTI history was 3.0 (IQR 2.0–5.0) years, and the median number of UTI episodes in the preceding 12 months was 4 (IQR 3–5). Baseline demographic and clinical characteristics are shown in Table 1.

Table 1. Baseline demographic and clinical characteristics (N = 100)

Women with rUTI demonstrated significantly altered renal function parameters compared with controls. Serum creatinine and blood urea were higher, while eGFR was significantly lower in the rUTI group. Urinary albumin excretion was increased, reflected by higher UACR values and a greater prevalence of microalbuminuria. The distribution of renal indices is summarized in Table 2 & Figure 1.

Table 2. Renal function parameters in rUTI and control groups

Figure 1: Renal function and renal risk markers in rUTI group(Percent Change vs Controls)

Both systolic and diastolic blood pressure were significantly higher in women with rUTI. Hypertension prevalence was numerically higher in the rUTI group, although the difference did not reach statistical significance. Blood pressure outcomes are presented in Table 3.

Table 3. Blood pressure profile of study participants

Within the rUTI group, increasing annual frequency of UTI episodes was associated with higher UACR and serum creatinine and with lower eGFR. Systolic blood pressure correlated positively with UACR, and participants with microalbuminuria had higher mean systolic BP than those without microalbuminuria. After adjusting for age, BMI, and diabetes, rUTI status remained independently associated with lower eGFR and higher systolic BP, and it was associated with a higher odds of microalbuminuria. These associations are summarized in Table 4.

Table 4. Correlation and multivariable analysis of rUTI with renal and BP parameters

In this comparative study of 100 adult women, rUTI was associated with measurable differences in renal function indices and blood pressure parameters. Women with rUTI demonstrated higher serum creatinine and urea, lower eGFR, and greater urinary albumin excretion compared with controls. These findings suggest that recurrent infections, even in the absence of overt kidney disease, can coincide with subclinical renal functional stress, consistent with prior clinical observations that repeated UTI episodes contribute to cumulative inflammatory burden [3,5].

Albuminuria emerged as a sensitive marker in the present cohort. UACR values were significantly higher in the rUTI group, and microalbuminuria prevalence was four-fold higher than in controls. Albuminuria reflects endothelial dysfunction and glomerular–tubular injury and is also an established predictor of cardiovascular and renal risk [6]. Importantly, transient increases in urinary albumin can occur during active urinary infections; therefore, standardized timing of sampling and clinical stability are important in interpretation [10]. The absence of nephrotic-range albuminuria in our cohort supports a pattern of low-grade injury rather than advanced glomerular disease.

Blood pressure regulation also differed between groups. Both systolic and diastolic blood pressure were significantly higher in the rUTI group, and hypertension prevalence was numerically higher. These results align with evidence that infection-associated renal injury can be accompanied by elevated ambulatory blood pressure indices and early hypertensive patterns in adult women, even when overall filtration capacity is maintained [8,9]. Potential mechanistic pathways include renal microvascular dysfunction, impaired pressure natriuresis, low-grade activation of the renin–angiotensin system, and augmented sympathetic drive following recurrent inflammatory insults [7,11].

The observed associations between rUTI burden and renal indices provide additional biological plausibility. Annual UTI episode frequency correlated positively with UACR and serum creatinine and negatively with eGFR, indicating a dose–response relationship within the rUTI group. Furthermore, systolic BP correlated with UACR, and participants with microalbuminuria demonstrated higher systolic BP, supporting an integrated cardio–renal phenotype in which endothelial injury and albumin leak coincide with rising pressure load [6,12]. In multivariable models adjusted for major confounders, rUTI status remained independently associated with lower eGFR, higher systolic BP, and increased odds of microalbuminuria. These findings highlight that rUTI itself can be an important clinical signal rather than an isolated recurrent infection event.

From a clinical perspective, women presenting with rUTI represent a group that could benefit from a broader evaluation strategy beyond acute antimicrobial therapy and recurrence prevention. Incorporating periodic monitoring of renal function and UACR alongside structured BP assessment can assist in early detection of high-risk individuals and prompt targeted interventions such as optimizing glycemic control, lifestyle modification, and timely nephrology referral when indicated [2,6]. Such an approach also supports rational antibiotic stewardship and individualized prophylaxis strategies to reduce recurrence, antimicrobial exposure, and downstream complications [2,13].

Limitations

This single-centre study used a comparative design over five months, limiting generalizability to other settings. Imaging for renal scarring and structural abnormalities was not performed, restricting anatomical correlation with functional markers. Urine sampling was based on spot UACR rather than repeated measurements, and ambulatory blood pressure monitoring was not undertaken. Residual confounding from unmeasured factors such as analgesic use, dietary sodium intake, and prior antibiotic exposure remained possible.

Adult women with recurrent urinary tract infections showed significant differences in renal function parameters and blood pressure regulation compared with controls. The rUTI group had higher serum creatinine and urea levels, lower eGFR, and increased urinary albumin excretion with a higher prevalence of microalbuminuria. Systolic and diastolic blood pressure values were also higher, and the infection burden correlated with worsening renal indices and albuminuria. After adjustment for key clinical confounders, rUTI remained an independent predictor of reduced eGFR, elevated systolic blood pressure, and microalbuminuria. Periodic renal function assessment and structured blood pressure monitoring should be considered in women with rUTI to support early risk stratification and prevention.

Acknowledgement

The authors thank the participants for their cooperation and the staff of the Department of Microbiology, Government Siddhartha Medical College, Vijayawada, for logistical and laboratory support throughout the study period. The contribution of the clinical teams involved in participant identification and data collection is also gratefully acknowledged. We appreciate the assistance of the institutional laboratory personnel in maintaining quality control during biochemical and urinary estimations and in supporting timely processing of samples.

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