1. Introduction
Obesity is a major risk factor in the development of benign prostatic hyperplasia (BPH) and associated lower urinary tract symptoms (LUTSs), a highly prevalent condition that affects over 80% of men 70 years old and older [
1,
2]. Studies have shown that elevated body mass index (BMI), a common calculation from height and mass used to classify body weight categories, increases likelihood of more intense and rapidly onsetting LUTS [
3]. A variety of etiological explanations exist, including elevated intra-abdominal pressures increasing bladder pressure, an endocrine-hypogonadal dysfunction, and increased sympathetic activation and inflammation [
3]. Since the global obesity epidemic, more patients are presenting with concomitant LUTS and elevated BMI. The literature suggests that obese patients are less likely to experience significant benefits from pharmaceutical therapy alone, and with further progression of symptoms, obese patients are often more inclined to receive surgical intervention for definitive treatment [
4].
Patients with obesity who receive surgical treatment options have nuanced background profiles compared to other patients with BPH. In a study by Chen et al., patients with obesity undergoing Greenlight photo-vaporization of the prostate (PVP) were found to be younger with larger transition zones and total prostate volume [
5]. However, this was not correlated to discrepancies in either surgical parameters or complications. When reviewing patients who received prostatectomies via either transhow resection of the prostate (TURP) or Greenlight laser selective PVP, surgical complications, such as retention of urine, bladder stones and diverticula formation, were not significantly different for overweight and obese patients [
6]. Similar observations were noted for thulium laser vapoenucleation [
7]. These studies, however, notably did not control for several other comorbidities which are also significantly more prevalent in patients with obesity. Thus, the many associated patient characteristics in patients with obesity and LUTS must be sufficiently accounted for when assessing BMI’s influence. Obesity commonly coexists with metabolic syndromes, particularly diabetes and neurologic diseases, which independently influence bladder function, LUTS, and recovery. Prior studies therefore often capture combined effects rather than BMI alone. Excluding these conditions can isolate BMI’s influence, enabling more precise, personalized risk stratification and interpretation.
Holmium laser enucleation of the prostate (HoLEP) is an American Urological Association (AUA)-recommended treatment option for LUTS and BPH, independent of prostate and gland size [
8]. It has been employed in patients with elevated BMIs, who also typically have larger prostate volumes [
9]. Obesity significance testing with post-operative complications has proven difficult, due to HoLEP’s low complication rate, but obesity has been correlated to longer operation times in prior studies [
10]. One complication of note was higher incidence of open conversion for patients with elevated BMIs receiving HoLEP due to their body habitus and difficulty with scope manipulation [
11]. However, the current body of literature has failed to control for colinear patient characteristics and has been performed on too small of a sample pool to aptly capture surgical complications and adverse events. We sought to address this gap by investigating the influence of BMI on an array of surgical characteristics and outcomes related to HoLEP.
2. Materials and Methods
Following IRB approval, we conducted a retrospective review of a prospectively maintained database of patients undergoing HoLEP surgery for BPH at our institution between January 2021 and August 2025. All HoLEP procedures were performed by one of two surgeons using high-powered pulse-modulated holmium laser technology. Exclusion criteria included patients with history of diabetes, neurological disease, urinary tract infections, prostatitis, urethral stricture, or radiation therapy. Diabetes and neurologic diseases have been previously correlated with worse surgical outcomes following HoLEP, and, given their higher prevalence in obese patients, were excluded (
n = 342) [
12]. Patients with intra-operative complications or receiving hemi-HoLEP (partial/half gland removal) totaled
n = 81 and
n = 8 respectively and were also excluded. Surgeries with intra-operative complications were removed given that this investigation studied outcome courses, all of which would be influenced by the complication itself instead of BMI alone. Post-operative survey responses, patient demographics, baseline health status, symptom scores, and urinary function; operative characteristics; immediate post-operative details; functional outcomes; and adverse event incidences were all collected for each participant in our study. Patients missing greater than 25% of this information were also excluded.
Analysis was performed with a set of six confounding variables. Patient’s age, pre-operative prostate volume, prostate-specific antigen level, American Society of Anesthesiologists (ASA) physical status classification, occurrence of a prior BPH surgery, and history of anticoagulation use at time of surgery. These potential confounders are all indicated to potentially influence peri- and post-operative characteristics and outcomes, and all could have been correlated to a patient’s BMI. To analyze patient BMI as the independent variable, while also accounting for clinical relevance of standard BMI categories, two series of statistics were performed in parallel. First, BMI was treated as a continuous variable. Subsequently, a BMI category of underweight, normal weight, overweight, and obese was assigned to each patient: buckets were under 18.5, 18.5 to 24.9, 25 to 29.9, and 30 or greater kg/m2, respectively. For categorical analyses, BMI was modeled using indicator (dummy) variables with the healthy BMI range as the reference category, allowing estimation of category-specific effects while preserving within-group variability. The underweight group was excluded from categorical analysis due to insufficient sample size (n = 2) for stable inference.
For continuous outcome variables, linear regressions were fit, accounting for confounders, between patient BMI and the outcome, and β values for the regression coefficient were recorded. For categorical variables, such as for the occurrence of an event, logistic regressions, also accounting for confounding variables, were employed, with odds ratios (ORs) calculated. For all outcome analyses, sample size varied by endpoint based on data availability. General statistics utilized all available data for each variable. In contrast, multivariable analyses were conducted using complete-case samples, such that the analytic denominator for each model includes only patients with non-missing BMI, covariates, and the outcome of interest. Accordingly, sample sizes differ across outcomes and models. For both β and OR, 95% confidence intervals (CIs) and p-values were derived. All analyses were conducted using Python 3.0 (Python Software Foundation, Wilmington, DE, USA). Statistical significance was defined as p < 0.05. Due to the exploratory nature of this work, p-value adjustments, such as a Bonferroni correction, were not employed.
4. Discussion
Results from our investigation suggest that BMI is not an independent predictor of perioperative, short-term follow-up, or patient-reported outcomes following HoLEP. This is following statistical control of clinically relevant confounders. This work mirrors findings from other prostate resection surgical techniques for BPH. In the Greenlight PVP literature, Chen et al. and Pierce et al. studied similar surgical outcomes, also noting BMI’s lack of influence [
5,
13]. Previous characterizations of obesity’s deleterious effect in BPH treatment have centered on increased waist circumference or BMI in the setting of metabolic syndrome [
14]. These studies proceed to associate obesity with persistent storage LUTS following open prostatectomies and TURP; however, this contextually skews results, due to other metabolic syndrome comorbidities like diabetes or hypertension. Alternatively, we chose confounding variables based on their collinearity with obesity itself, to better segregate BMI’s effect. Further, we excluded neurological diseases and diabetes mellitus, often considered a large confounding comorbid condition in urology studies involving obesity [
15]. While this limits the generalizability of the true clinical effect of an elevated BMI, omitting common sequalae, the purpose of this study was to investigate the influence of the BMI metric in isolation at risk stratification, necessitating removal of as much confounding as possible.
Three of our outcome variables were significantly correlated to BMI following confounder control: enucleation time, dysuria, and AUASS change. While we elected not to perform
p-value adjustments due to this investigation’s exploratory nature, given we performed 20 comparisons, this is an inherent limitation. Particularly for AUASS change, which had a
p-value of 0.0334, more caution is required when generalizing results. The significant difference in enucleation time is likely a reflection of larger prostates or more challenging tissue planes, which would result in longer time for enucleation. This has been similarly shown in the literature where Tamalunas et al. noted a twelve-minute increase in enucleation time from 31 to 43 min in patients with obesity (
p < 0.01) [
10]. Chen et al. similarly noted larger prostate sizes (
p < 0.001) and transition zone volumes (
p = 0.017) with BMI for patients receiving Greenlight PVP [
5]. While our result was also significant (
p = 0.0132), this would likely not remain following
p-value adjustment, suggesting a small effect size or a side effect of our large sample cohort and high number of significance tests performed.
Dysuria was also significantly more common as patient BMI category increased (OR: 1.084;
p-value < 0.001). This may be a factor of the patient’s BPH itself, where obesity and an elevated BMI have previously been correlated to increased LUTSs, including dysuria specifically [
16]. In Greenlight PVP, Pierce et al. found that obese patients required higher energy utilization compared to normal BMI patients [
13]. Higher energy utilization can lead to increased mucosal irritation and transient dysuria. In our study, we did not find high total energy utilization with increased BMI. However, other mechanistic explanations include delayed epithelial healing in metabolic disease, altered nociceptive signaling, and undiagnosed prediabetes/diabetes. Diabetes mellitus has been shown to significantly correlate to dysuria symptoms in men, due to diabetic autonomic neuropathy causing genitourinary disturbances [
17,
18]. While we excluded any patient with a diabetes diagnosis, given that it will be more prevalent in patients with obesity, this cohort is more likely to be prediabetic or have undiagnosed diabetes. This could explain the higher dysuria rate with increasing BMI category. Baseline hemoglobin A1c (HbA1c) was not available for these patients, preventing any subsequent analysis on its correlation. Lacking this or any other indication of prediabetes or uncontrolled glucose levels limits substantiating this assumption. While our study did not directly quantify prediabetes or HbA1c, a prior HoLEP study found no differences in outcomes after stratifying patients based on HbA1c levels [
12].
It is worth noting that larger body habitus can make HoLEP technically challenging to perform, causing some surgeons to abort cases or convert to TURP and/or open surgery [
19]. In our cohort, we were able to successfully perform HoLEPs on patients with BMIs up to 49.66 kg/m
2 with zero conversions or case abortions. This success may be due, in part, to an adaptive surgical strategy that modifies our traditional “bottom-up” approach as needed. Specifically, if we are unable to enter the bladder neck initially, we create a posterior incision distally starting at the verumontanum and move proximally toward the bladder neck. The anterior plane of the prostate is generally shorter than the posterior plane, allowing for easier entry into the bladder. Once bladder entry is obtained through the anterior plane, the lateral margins of the bladder neck are opened dissected in a top-down approach. The high-powered holmium laser offers excellent hemostasis which minimizes bleeding risks that are otherwise amplified in obesity, making HoLEP an excellent choice for obese patients with LUTS [
20,
21]. The low complication rate of HoLEP may be a limitation in itself, due to sparse events limiting reliability of logistic regressions for subgroups. This is countered by our large sample size (
n = 1445 patients), but generalizability concerns persist given how rare several of these events are.
Our study consists of several limitations due to its retrospective single-center nature. This includes establishing only correlations instead of causation, a low frequency of adverse events limiting the power of significance tests, and a lack of randomization. Although patients depicted a wide distribution of BMI values, other demographic variables may be more homogeneous given that they all received care from the same institution. These limitations are countered by our large overall sample size of 1445 patients, our uniform procedural, data collection, and statistical techniques, and our robust confounder control. Further, studying multiple outcomes from different temporal domains offered a broader, more inclusive depiction of surgical outcomes from HoLEP.
Our investigation suggests that patient BMI does not meaningfully influence surgical safety, functional recovery, or patient-perceived benefit following HoLEP, and thus should not be used as a sole determinant in clinical decision-making. Albeit via a retrospective investigation with clinically relevant exclusion criteria, this study suggests that specifically BMI may lack clinical utility. Given the lack of statistical correlation, patient BMI alone does not appear to be a deterrent for surgical operation, nor could it act as a surrogate for surgical risk. Categorizing patients as underweight, normal weight, overweight, or obese, albeit contributory to developing BPH in the first place, fails to establish insight into their surgical outcomes. Other patient demographics or comorbidities may contribute to a more complete characterization of HoLEP efficacy, but this research dissuades reliance on BMI alone. Suitability of this surgical procedure remains reliant on the shared decision-making and discretion of the urologist and patient.