Abstract
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Purpose
- This study aimed to explore the incidence of postoperative urinary retention (POUR) and the associated risk factors in patients with benign anorectal diseases.
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Methods
- A retrospective analysis was conducted using data from patients who underwent surgery for benign anorectal diseases between June 2020 and October 2023. Patients were categorized into the POUR group and the non-POUR group according to the occurrence of postoperative urinary retention. Univariate analysis and multivariate logistic regression analyses were performed to identify risk factors.
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Results
- The incidence of POUR following surgery for benign anorectal diseases was 9.4%. Female sex (P<0.001), being married (P<0.001), age over 60 years (P=0.013), preoperative diabetes (P<0.001), benign prostatic hyperplasia in men (P=0.001), elevated preoperative serum creatinine levels (P=0.015), mixed hemorrhoids (P=0.001), subarachnoid anesthesia (P<0.001), and general anesthesia (P<0.001) were identified as independent risk factors for POUR in patients with benign anorectal diseases. In addition, the POUR group demonstrated a significantly longer length of hospital stay compared with the non-POUR group (P<0.05).
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Conclusion
- POUR results from the combined effects of multiple factors. Through the identification and analysis of POUR-related risk factors, interventions such as regulating perioperative glycemic control, optimizing renal function, and selecting appropriate anesthesia techniques may further reduce its incidence.
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Trial registration
- Chinese Clinical Trial Register identifier: ChiCTR2500097230.
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Keywords: Benign anorectal diseases; Sacral canal block; Postoperative urinary retention; Comorbidity; Risk factors
INTRODUCTION
Benign anorectal disorders comprise a diverse spectrum of conditions with varied etiologies, including both congenital and acquired origins. These disorders may manifest as inflammatory or tumor-related entities [1]. However, in previous research, benign anorectal diseases have received significantly less attention than malignant tumors. In recent years, with continuous improvements in living standards and dietary patterns, there has been a notable increase in the number of patients seeking medical care and hospitalization for benign anorectal disorders. According to a health survey report in the United States, approximately 20% of residents suffer from hemorrhoids, including 13% of adults [2]. As reported by Smith et al. [3], the annual incidence of perianal abscess is approximately 40 cases per 100,000 adults. The incidence of anal fistula is about 2 cases per 10,000 people per year, with a higher prevalence in men than in women [4]. Surgery remains the primary treatment modality for benign anorectal diseases, and urinary retention, a major postoperative complication, has an incidence of approximately 15% [5]. Urinary retention can induce significant postoperative stress responses and may lead to complications such as urinary tract infections (UTIs), urinary obstruction, difficulty in urination, and pain, which can result in prolonged hospital stays and increased treatment costs. In severe cases, postoperative urinary retention (POUR) may cause irreversible bladder damage, detrusor muscle injury, and acute renal failure [6]. Therefore, reducing or preventing the occurrence of POUR represents a critical research focus and an emerging trend in anesthesiology and anorectal surgery.
The pathogenesis of POUR may be explained, in part, by the shared neural origins of the nerves controlling the urethral and anal sphincters. Surgical trauma, postoperative pain, and other stimuli can activate the adrenergic system. In addition, internal urethral sphincter spasm, obstruction secondary to anal canal packing, and pain have been implicated as potential contributing mechanisms of POUR [7]. Currently, 3 primary approaches are used to diagnose POUR [8]: (1) medical history and physical examination; (2) assessment of the need for urinary catheterization; and (3) ultrasound evaluation. To date, no universally accepted standard exists regarding the postoperative use of indwelling urinary catheters. In clinical practice, decisions regarding postoperative catheter placement are primarily based on the patient’s clinical condition, type of surgery, and medical history [9, 10].
With the introduction of Enhanced Recovery After Surgery (ERAS) protocols and multimodal analgesia strategies, the clinical application of regional anesthesia techniques, including ultrasound-guided pudendal nerve block, caudal anesthesia, and patient-controlled analgesia via caudal catheterization, has expanded. Consequently, risk factors for POUR have attracted renewed clinical and research interest. In this retrospective study, we collected clinical data from consecutive patients with benign anorectal diseases who underwent surgery in the anorectal department. The aim of this study was to identify risk factors associated with POUR and to provide clinical evidence to support strategies for its prevention and reduction.
METHODS
Ethics statement
This study was approved by the Ethics Committee of Chongqing Traditional Chinese Medicine Hospital (No. 2024-IIT-KS-12) and registered with the Chinese Clinical Trial Register (identifier: ChiCTR2500097230). Informed consent was waived due to the use of deidentified data and the retrospective nature of the study. All study procedures were conducted in accordance with the ethical principles outlined in the Declaration of Helsinki.
Study subjects
Patients who underwent surgery for benign anorectal diseases at our hospital between June 2020 and October 2023 were consecutively enrolled. Inclusion criteria were as follows: patients aged ≥18 years; patients who underwent surgery for benign anorectal diseases, including hemorrhoids, anal fistula, perianal abscess, and anal fissure, at our hospital; and patients with complete surgical and medical records. Exclusion criteria included the following: patients who had a urinary catheter inserted before surgery; patients with urinary system diseases such as prostate cancer or uremia; patients with severe dysfunction of vital organs, including the liver, kidneys, heart, or brain, that precluded surgical tolerance; patients with pilonidal sinus or colitis who underwent colonoscopy; and patients who required immediate urinary catheterization within 4 hours after surgery by an experienced surgeon in accordance with the surgical protocol.
Definition of POUR
The diagnostic criteria for POUR included the inability to urinate spontaneously within 4 hours after surgery, accompanied by symptoms such as lower abdominal distension and pain, urinary urgency, and discomfort [11]. Physical examination findings included marked tenderness on palpation of the bladder above the pubic symphysis and dullness on bladder percussion. Patients who required urinary catheterization based on these diagnostic criteria were also classified as having POUR.
Grouping
Based on the occurrence of POUR, the enrolled patients were divided into 2 groups: the POUR group and the non-POUR group. The incidence and risk factors of POUR were subsequently analyzed using statistical methods.
Anesthesia management
Before surgery, patients were informed about the anesthesia plan, which included ultrasound-guided sacral canal block, general anesthesia with tracheal intubation, epidural anesthesia, subarachnoid anesthesia, and local anesthesia. In our hospital, most patients selected ultrasound-guided sacral canal block. In cases of ineffective sacral anesthesia or technical failure, such as vascular puncture or local anesthetic toxicity, the procedure was discontinued, and alternative strategies (including reattempting sacral anesthesia, switching to subarachnoid anesthesia, or selecting local anesthesia) were considered according to the clinical situation. If patients continued to experience pain during surgery, intravenous sufentanil (National Medical Product Approval No. H20054171, Yichang Renfu Pharmaceutical) was administered for analgesia, along with propofol (National Medical Product Approval No. H20030114, Sichuan Guorui Pharmaceutical) for sedation. Local infiltration anesthesia consisted of the injection of 10 mL of lidocaine (National Medical Product Approval No. H31021868, Shanghai Xudong Haipu Pharmaceutical) around the anus, as determined by the surgeon based on clinical requirements. Depending on the patient’s condition, intravenous sufentanil at a dose of 0.1 μg/kg and midazolam (National Medical Product Approval No. H19990027, Jiangsu Enhua Pharmaceutical) at a dose of 0.02 mg/kg were administered. General anesthesia included intubated general anesthesia as the preferred modality, general anesthesia following failed sacral canal block, and nonintubated general anesthesia.
There were 3 postoperative analgesia options available for patients to choose from: patient-controlled intravenous analgesia (PCIA), nonsteroidal anti-inflammatory drugs (NSAIDs), and PCIA combined with NSAIDs. The PCIA regimen consisted of 200 mg flurbiprofen axetil injection, 5 mg butorphanol tartrate injection, and 100 mL normal saline. The infusion rate was set at 2 mL/hr, with a bolus dose of 0.5 mL per activation and a lockout interval of 15 minutes. NSAIDs referred to a single postoperative dose administered either intravenously, such as 50 mg parecoxib sodium for injection, or orally, such as 0.1 g diclofenac sodium sustained-release tablets. PCIA plus NSAIDs indicated postoperative pain control using PCIA in combination with systemic NSAIDs administered orally or intravenously.
Surgical team and technique
The anorectal department of our institution has a large and experienced medical team consisting of 60 healthcare professionals. The department is led by senior chief physicians with extensive clinical expertise. All surgeons involved in the procedures were attending physicians or above and possessed the required qualifications and clinical competence. Surgical interventions were uniformly performed in strict accordance with established clinical pathways and standardized protocols. In addition, several team members have participated in the development of authoritative national and international clinical guidelines.
Data collection
Clinical data were obtained from the electronic medical record and anesthesia information systems. Baseline information collected included patient age, sex, smoking history, and drinking history. Comorbidities included diabetes, hypertension, coronary heart disease, hyperlipidemia, kidney disease, prostate disease, and malignant tumors. Surgical and anesthesia-related variables included anesthetic technique, type of postoperative analgesia, surgical procedure, disease type, length of hospital stay, and laboratory indicators measured on admission, including white blood cell count, hemoglobin level, serum creatinine level, and blood urea nitrogen level. Postoperative complications, including urethral injury and urinary tract infection following indwelling catheterization, were also recorded.
Sample size calculation
We identified 19 potential risk factors for POUR, and previous studies reported an incidence of approximately 15% after anorectal surgery for benign anorectal diseases [5]. The allowable error (δ) was set at 5%, and the significance level (α) was set at 0.05. Based on these parameters, the estimated minimum sample size was 822 cases. A larger sample size was considered necessary to ensure the reliability of multivariate logistic regression analysis. Ultimately, a consecutive cohort of 7,550 patients treated at our institution between June 2020 and October 2023 was included.
Statistical analysis
Statistical analyses were performed using IBM SPSS ver. 23.0 (IBM Corp). The Shapiro-Wilk test was applied to assess the normality of continuous variables. Measurement data conforming to a normal distribution were analyzed using independent-samples t-tests and are presented as mean±standard deviation. Non-normally distributed measurement data were analyzed using the Mann-Whitney U-test [12] and are presented as median (interquartile range, IQR). Categorical variables were analyzed using the chi-square test or the Fisher exact test and are expressed as number and percentages. Univariate comparisons were conducted to identify risk factors associated with urinary retention. Variables with P-values of <0.05 in the univariate analysis were entered into multivariate logistic regression models to determine independent risk factors for postoperative urinary retention. All statistical tests were 2-sided, and P<0.05 was considered statistically significant. For comparison of hospital length of stay among different anesthesia groups, the Kruskal-Wallis H test was used, followed by Dunn's post hoc pairwise comparisons with Bonferroni correction.
RESULTS
From June 2020 to October 2023, a total of 7,550 consecutive patients with benign anorectal diseases were admitted to our hospital. During retrospective screening, 1,266 patients were excluded for the following reasons: 981 patients underwent colonoscopic treatment for colorectal polyps, 63 patients underwent surgical intervention for pilonidal sinus, 170 patients with colitis were admitted for conservative treatment, 33 patients had preoperative catheterization or required catheterization within 4 hours postoperatively, and 19 patients were younger than 18 years. Ultimately, a total of 6,284 patients were included in the final analysis. The study inclusion process is illustrated in Fig. 1.
Baseline characteristics
Among the 6,284 patients included, 3,896 (62.0%) were male and 2,388 (38.0%) were female. The mean age was 42.02±5.50 years (range, 18–89 years). Disease distribution included 1,104 cases (17.6%) of perianal abscess, 3,512 cases (55.9%) of mixed hemorrhoids, 1,525 cases (24.3%) of anal fistula, and 143 cases (2.3%) of anal fissure. Overall, 592 patients (9.4%) developed POUR. In the POUR group, there were 63 patients (10.6%) with perianal abscess, 455 (76.9%) with mixed hemorrhoids, 68 (11.5%) with anal fistula, and 6 (1.0%) with anal fissure. The mean time to onset of POUR was 1 day after surgery. The incidence of POUR according to disease type is summarized in Table 1.
Univariate comparisons and multivariate logistic regression analysis of risk factors for POUR after anorectal surgery for benign anorectal diseases
The results of the univariate analysis comparing general characteristics, surgical variables, and anesthesia methods between the groups are shown in Fig. 2. Findings from the univariate analysis of laboratory parameters are presented in Table 2. No statistically significant differences were observed between the groups with respect to smoking history, drinking history, coronary heart disease, hyperlipidemia, kidney disease, malignant tumors, preoperative neutrophil percentage, serum urea level, or type of postoperative analgesia (all P>0.05). In contrast, significant differences were identified between the groups in sex (P<0.001), age (P<0.001), marital status (P<0.001), diabetes (P<0.001), benign prostatic hyperplasia (BPH) in men (P<0.001), intraoperative infusion volume (P=0.026), anesthesia method (P<0.001), disease type (P<0.001), white blood cell count, hemoglobin level, and serum creatinine level (P<0.001).
Variables with P<0.05 in the univariate analysis were subsequently entered into a multivariate logistic regression model. The results demonstrated that female sex (adjusted odds ratio [aOR], 3.106; P<0.001), marital status (aOR, 1.715; P<0.001), age over 60 years (aOR, 1.417; P=0.013), preoperative diabetes (aOR, 2.463; P<0.001), BPH in men (aOR, 4.772; P=0.001), anesthesia method (P<0.001), disease type (P<0.001), and elevated preoperative serum creatinine (aOR, 1.008; P=0.015) were independent risk factors for POUR in patients with benign anorectal diseases. With respect to anesthesia method, subarachnoid anesthesia and intubated general anesthesia were associated with 5.3- and 10.6-fold higher risks of POUR, respectively, compared with sacral canal anesthesia (both P<0.001). In contrast, local anesthesia was associated with a significantly lower incidence of POUR than sacral canal anesthesia (P=0.005). These findings are illustrated in Fig. 3.
The impact of anesthesia methods on POUR
The median length of hospital stay was 15 days (IQR, 12–15 days) in the POUR group and 7 days (IQR, 7–8 days) in the non-POUR group. A significant difference in hospital length of stay was observed between the groups (z=36.634, P<0.001).
There was a significant difference in the length of hospital stay among patients receiving different anesthesia methods (P<0.001). Pairwise comparisons showed that patients who received subarachnoid anesthesia had significantly longer hospital stays than those who received sacral canal anesthesia or local anesthesia (P<0.05). In addition, patients who received sacral canal anesthesia had significantly longer hospital stays than those who received local anesthesia (P<0.05). Patients who received general anesthesia had longer hospital stays than those who received sacral canal anesthesia, local anesthesia, or epidural anesthesia, and these differences were statistically significant (P<0.05). Given that the majority of patients with benign anorectal diseases at our hospital underwent sacral canal anesthesia, patients who received epidural, local, or general anesthesia were excluded to further evaluate the impact of sacral canal anesthesia versus subarachnoid anesthesia on POUR. The results showed that the incidence of postoperative catheterization was significantly higher in patients who received subarachnoid anesthesia than in those who received sacral canal anesthesia (P<0.05). In addition, the duration of catheter indwelling was significantly longer in the subarachnoid anesthesia group (3.03±1.09 days vs. 2.45±1.03 days, P<0.001). Only 5 patients with POUR developed UTIs during hospitalization, and no patients experienced urethral injury following catheterization (Table 3).
DISCUSSION
Urinary retention is a common postoperative complication, with reported incidence varying widely according to the type of surgery and anesthesia. Previous studies reported an incidence of approximately 3.8% in general surgery patients, whereas the incidence following inguinal hernia repair ranged from 5.9% to 38% [13, 14]. The highest reported incidence of POUR has been observed in patients undergoing joint replacement surgery, ranging from 10.7% to 84% [15, 16]. The overall incidence of POUR following spinal surgery was reported to be 15.1% [17]. According to a randomized controlled trial by Lau and Lam [14], the incidence of POUR after anorectal surgery ranged from 1% to 52%. In the present study, the incidence of POUR in patients with benign anorectal diseases was 9.4%, which is lower than many previously reported rates. These discrepancies may be attributable to differences in anesthesia techniques, perioperative fluid management strategies, and diagnostic criteria.
Injury to the pelvic nerves and reflex-mediated internal sphincter tension are considered major contributors to the high incidence of POUR in patients undergoing anorectal surgery. Pain stimulation resulting from bladder overdistension may trigger a range of adverse physiological responses, including vomiting, bradycardia, hypotension, hypertension, arrhythmia, and even cardiac arrest. Persistent urinary retention may also lead to complications such as UTIs, urethral injury, and bladder dysfunction. These complications can further exacerbate patient discomfort, negatively affect quality of life and postoperative recovery, and prolong hospital stays [18]. Akhtar et al. [19] reported that 21% of women with preoperative indwelling catheters developed UTIs within 6 days after surgery. Platt et al. [20] demonstrated a significant increase in mortality among hospitalized patients with indwelling catheters and hospital-acquired UTIs. The development of POUR is multifactorial and is often associated with surgical factors, anesthetic techniques, and patient-related characteristics. Identifying high-risk populations, clarifying relevant risk factors, guiding treatment strategies, and implementing timely nursing interventions therefore represent key research priorities for anesthesiologists and anorectal surgeons.
This study identified age over 60 years as an independent risk factor for POUR. Previous studies have demonstrated that the incidence of POUR increases with advancing age, with patients older than 50 years exhibiting a 2.4-fold higher risk [13, 14, 21]. One possible explanation is age-related progressive neuronal degeneration, which may impair bladder function by disrupting neural regulation of bladder sensation and the micturition reflex [21]. In older individuals, age-associated reductions in muscle mass and increased susceptibility to fatigue contribute to decreased detrusor muscle contractility and bladder wall fibrosis. These physiological changes increase vulnerability to the inhibitory effects of anesthetic and analgesic agents after surgery, thereby predisposing patients to urinary dysfunction [22]. In addition, elderly patients often experience reduced nutritional intake, resulting in compromised nutritional status and a higher incidence of postoperative complications [23].
Patients with a history of BPH often present with varying degrees of bladder outlet obstruction before surgery, and their detrusor muscle contractile function is typically weaker than that of individuals without BPH [24]. Surgical trauma and anesthesia may further impair detrusor muscle activity, aggravate obstructive symptoms, and lead to bladder voiding dysfunction, ultimately resulting in urinary retention. A meta-analysis encompassing 570 studies reported that lower urinary tract symptoms secondary to BPH were significant risk factors for POUR (OR, 2.83; P<0.05) [25]. In the present study, multivariate analysis demonstrated that a preoperative history of BPH was an independent risk factor for POUR (aOR, 4.772; P=0.001). These findings indicate that male patients with BPH should be prioritized for preventive strategies and receive standardized and timely perioperative interventions.
Whether sex is an independent risk factor for POUR remains a subject of debate. Some studies have reported a higher incidence of POUR in men than in women [13, 18, 26], whereas a retrospective study by Liu et al. [27] observed a higher incidence among female patients. In the present study, the incidence of POUR was higher in women, and female sex emerged as an independent risk factor. Several factors may explain this finding. First, the female urethra is anatomically shorter and straighter than the male urethra, and its proximity to the anus may increase susceptibility to external stimulation. Second, women generally experience less discomfort during catheterization and may be more willing to accept catheter placement. In addition, environmental constraints in shared ward settings may delay voluntary voiding, particularly among patients requiring sitz baths for perineal wound care, which may further disrupt normal micturition patterns.
Our study also revealed that being married was an independent risk factor for POUR. We found that the mean age of unmarried patients (30.10±5.95 years) was significantly lower than that of married patients (45.16±12.15 years). According to previous literature, age is a well-established risk factor for POUR. Therefore, we adjusted for this potential confounding variable in the multivariate logistic regression model. The results demonstrated that, even after full adjustment, marital status remained significantly associated with POUR (P<0.001), with an aOR of 1.715 (95% confidence interval [CI], 1.287–2.285). This finding suggests that being married is an independent risk factor for POUR among patients with benign anorectal diseases, independent of age. These results prompted us to consider that marital status, as a sociodemographic factor, may exert its influence primarily through behavioral and psychological mechanisms rather than through direct biological pathways. For example, married patients may subconsciously rely more on spousal support and thus be less inclined to attempt early postoperative ambulation and spontaneous urination. In addition, they may feel reluctant to display vulnerable conditions, such as urinary incontinence or dependence on bedpans, in the presence of their spouse, which could induce psychological stress and subsequently inhibit the micturition reflex. The specific mechanisms linking marital status and POUR remain unclear and warrant further investigation to elucidate causal relationships and potential mediating factors.
In recent years, numerous studies have reported a significant association between diabetes and POUR following various surgical procedures [28, 29]. Toyonaga et al. [30] demonstrated that diabetes is an independent risk factor for POUR after surgery for benign anorectal diseases. Similarly, Drissi et al. [29] concluded that diabetes is an independent risk factor for urinary retention following inguinal hernia repair. Consistent with these findings, our study showed that preoperative diabetes was an independent risk factor for POUR in patients with benign anorectal diseases. Diabetes may contribute to urinary retention through multiple mechanisms, including diabetes-related bladder dysfunction, promotion of BPH, and increased susceptibility to UTIs. The primary manifestations of diabetes-related bladder dysfunction include reduced bladder sensation, increased bladder capacity, impaired detrusor muscle contraction, and elevated post-void residual urine volume [31, 32]. In addition, diabetes may contribute to the development of overactive bladder syndrome and associated bladder pain [6].
After analyzing the relationship between disease type and POUR, we found that the incidence of POUR following surgery for mixed hemorrhoids was the highest, at 13.0%, whereas the incidence following anal fissure surgery was the lowest, at 4.2%. Multivariate logistic regression analysis demonstrated that mixed hemorrhoids were an independent risk factor for POUR (aOR, 1.598; P=0.001). This difference may be attributed to the extensive nature of mixed hemorrhoidal lesions, the greater number of surgical resection quadrants, longer operative duration, and potential nerve injury caused by tissue traction during the procedure [33]. In contrast, our study did not identify a significant association between anal fistula or anal fissure and POUR, which may be related to the relatively small sample sizes of these subgroups.
In this study, analysis of anesthesia methods showed that the risk of POUR was significantly higher following subarachnoid anesthesia than following sacral canal anesthesia (aOR, 5.322; P<0.001), and similarly higher after general anesthesia than after sacral canal anesthesia (aOR, 10.600; P<0.001). These findings are consistent with those reported by Brouwer et al. [34], who identified spinal anesthesia as an independent risk factor for POUR. Potential mechanisms include the injection of local anesthetics into the subarachnoid space, which blocks action potential transmission between the bladder and sacral spinal cord segments (S2–S4) via nerve fibers, leading to weakened bladder contraction, detrusor muscle relaxation, and reflexive spasm of the bladder outlet and urethral sphincter [7]. Our study also demonstrated a relatively high incidence of POUR following general anesthesia. Possible explanations include greater disease severity among patients requiring general anesthesia, longer operative and anesthesia durations, increased perioperative fluid administration, and disruption of autonomic nervous system regulation by general anesthetics, all of which may impair bladder contractility. Experimental studies in rats and dogs have shown that sedative-hypnotics and volatile anesthetics can suppress the micturition reflex [35, 36]. Specifically, diazepam and propofol reduce detrusor muscle contraction, whereas isoflurane, methoxyflurane, and halothane inhibit detrusor contractility, with halothane additionally increasing bladder capacity [35]. Previous studies have also suggested that local infiltration anesthesia may reduce postoperative analgesic requirements and lower the risk of POUR in anorectal surgery [36]. A prospective study by Fleischer et al. [37] reported a lower incidence of urinary retention in patients undergoing anorectal surgery under local anesthesia compared with those receiving subarachnoid anesthesia, findings consistent with our results. Possible reasons include the absence of motor block, which allows long-acting local anesthetics to promote early postoperative activity, active contraction of abdominal muscles, and early ambulation, thereby facilitating bladder emptying. Notably, the aORs and 95% CIs for subarachnoid anesthesia and general anesthesia in our study were relatively wide; for example, the aOR for general anesthesia was 10.600 (95% CI, 3.489–32.210). This variability may be attributable to heterogeneity between groups and represents a limitation related to the retrospective study design. Furthermore, our study showed that the incidence of POUR following sacral canal anesthesia was significantly lower than that observed after general or subarachnoid anesthesia. This may be related to the use of ultrasound guidance and the minimum effective dose of ropivacaine during sacral canal anesthesia, which could help preserve bladder function and reduce the risk of POUR.
Our study also demonstrated that patients with POUR had a longer length of hospital stay compared with those without POUR. Different anesthesia methods exert differential effects on hospital stay duration. Specifically, subarachnoid anesthesia was associated with longer hospital stays than sacral canal anesthesia and local anesthesia. General anesthesia was also associated with prolonged hospital stays compared with sacral canal anesthesia, local anesthesia, and epidural anesthesia. POUR delays patient discharge, increases medical costs, and imposes an additional economic burden on patients. To mitigate these adverse outcomes, high-level intraspinal anesthesia and analgesia, as well as high-dose systemic opioid administration, should be avoided whenever possible. Instead, ultrasound-guided sacral canal block and local anesthesia, among other regional anesthetic techniques, should be preferentially selected to further reduce the incidence of POUR.
Furthermore, several studies have shown that prolonged operation time is associated with an increased risk of POUR. Extended surgical duration often leads to greater intraoperative intravenous fluid administration. Increased fluid intake is an important contributor to urinary retention [30]. Excessive fluid infusion can cause bladder overdistension, potentially resulting in irreversible detrusor dysfunction [38]. Bailey and Ferguson [39] reported that restricting intravenous and oral fluid intake reduced the incidence of POUR from 15% to 4%. However, whether the higher incidence of POUR observed with prolonged surgery is directly attributable to increased intraoperative fluid infusion remains a matter of debate [33]. In our study, no significant association was identified between POUR and either operative duration or intraoperative fluid volume. This finding may be explained by the relatively short operative times and comparatively low intraoperative fluid volumes in our cohort, which were typically below 1,000 mL. Future studies should further explore the relationship between perioperative restrictive fluid strategies and the development of POUR.
During surgery, traction, sharp dissection, or thermal injury to the perianal, rectal, and perineal regions may damage muscles, blood vessels, and nerves, resulting in local inflammation and pain [40]. Pain stimulation increases sympathetic nervous system activity, leading to reflex muscle spasm in the perineum, prostate, and bladder neck, which can impair voiding and cause urinary retention. Effective postoperative analgesia has been associated with a reduction in postoperative complications, including a lower incidence of POUR. Existing evidence suggests that intravenous or intramuscular opioid administration may directly affect bladder function by inhibiting acetylcholine release from sacral parasympathetic neurons that regulate detrusor muscle contraction, thereby contributing to the development of POUR [41]. Unfortunately, our retrospective analysis did not include systematic assessment of postoperative pain using standardized instruments such as the visual analog scale or numerical rating scale. Analysis of postoperative analgesic regimens showed no significant difference in the incidence of POUR between patients receiving postoperative PCIA and those treated with nonsteroidal anti-inflammatory drugs. This result may be related to the relatively small proportion of patients who underwent PCIA after surgery.
Creatinine in the human body is derived from both endogenous and exogenous sources. Its serum concentration is influenced by multiple factors, including age, sex, race, muscle mass, and protein catabolism rate [42]. Our study demonstrated that elevated preoperative serum creatinine was an independent risk factor for POUR. Several potential explanations may account for this finding. First, diabetes was identified as a risk factor for POUR in our study, and poorly controlled diabetes can cause renal and bladder damage, leading to elevated creatinine levels [43]. Second, patients with a history of urinary tract obstruction may present with increased preoperative creatinine levels; such patients often have a prior history of catheterization and may be more likely to require postoperative catheterization. Third, patients with perianal abscesses, particularly those complicated by infection, frequently exhibit elevated serum creatinine levels. Urinary retention is a multifactorial process. Whether elevated serum creatinine directly affects pelvic autonomic nerves, resulting in reduced bladder tone and muscle relaxation, or indirectly influences bladder reflexes through associated comorbidities remains unclear and warrants further investigation through basic and prospective clinical studies.
To prevent and manage POUR, in addition to conventional postoperative measures such as analgesia, hot compresses, and early ambulation, traditional Chinese medicine may offer complementary therapeutic benefits. These include syndrome differentiation–based herbal prescriptions, auricular point pressing, acupoint application, massage, traditional Chinese medicine sitz baths, acupuncture, and moxibustion [44]. Furthermore, additional research aimed at determining the minimum effective volume and concentration of ropivacaine for ultrasound-guided sacral canal anesthesia, as well as evaluating continuous sacral catheter–based patient-controlled analgesia, may help establish a balanced strategy that achieves effective postoperative pain control while minimizing the risk of POUR [45].
In this study, we analyzed clinical data from 6,284 patients treated at our institution. Using univariate comparisons and multivariate regression analyses, we identified independent risk factors for POUR in patients with benign anorectal diseases. The large sample size strengthens the reliability of our findings. Notably, elevated preoperative serum creatinine levels and marital status emerged as risk factors for POUR, findings that have not been previously reported. These results suggest that effective clinical risk assessment for POUR should integrate both physiological and sociopsychological factors to allow more comprehensive and accurate identification of high-risk patient populations.
Limitations
This study has several limitations. First, this study was a single-center, retrospective case-control investigation and is therefore subject to potential confounding. For example, unmeasured variables not included in the analysis may have influenced the risk of POUR, and surgical procedures were not performed by a single surgeon. Second, study data were derived from clinical records and charts. The diagnosis of POUR was primarily based on clinical symptoms and physical examination findings, without routine ultrasound measurement of post-void residual bladder volume. This limitation may have reduced diagnostic precision. Third, as a retrospective study, this analysis can identify associations but cannot establish causality. Future research should include prospective, multicenter studies and randomized controlled trials to confirm risk factors, identify high-risk populations early, and reduce the incidence of POUR. Lastly, this investigation represents a retrospective observational analysis. Although a broad range of potential confounders was incorporated to reduce bias, substantial differences in sample size among subgroups remain a limitation. Further validation through prospective randomized controlled trials is needed.
Conclusions
POUR following benign anorectal surgery results from the combined effects of multiple interacting factors. Independent risk factors for POUR in patients with benign anorectal diseases include female sex, age over 60 years, marital status, subarachnoid anesthesia, general anesthesia, BPH in men, preoperative diabetes, and elevated preoperative serum creatinine levels. Local anesthesia was associated with a reduced incidence of POUR. To further prevent urinary retention, careful assessment of perioperative risk factors and implementation of targeted interventions are essential. These strategies include evaluating baseline glycemic control, incorporating indicators such as hemoglobin A1c, adopting restrictive perioperative fluid management, preferentially selecting ultrasound-guided sacral canal block or local anesthesia, applying multimodal or preemptive analgesia, and integrating both traditional Chinese medicine and Western medical approaches during postoperative care. Such a comprehensive strategy may help minimize the occurrence of POUR.
ARTICLE INFORMATION
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Conflict of interest
No potential conflict of interest was reported.
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Funding
This study was supported by the Chongqing Medical Scientific Research Project (No. 2024MSXM134), a joint project of Chongqing Health Commission and the Chinese Ministry of Science and Technology.
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Author contributions
Conceptualization: all authors; Data curation: HZ; Formal analysis: HZ; Funding acquisition: LZ; Methodology: all authors; Writing–original draft: HZ; Writing–review & editing: all authors. All authors read and approved the final manuscript.
Fig. 1.Study flowchart.
Fig. 2.Univariate analysis of postoperative urinary retention (POUR) in patients with benign anal diseases. Bar graph showing log 10-transformed values. The y-axis shows the log 10-transformed raw values. BPH, benign prostatic hyperplasia; PCIA, patient-controlled intravenous analgesia; NSAID, nonsteroidal anti-inflammatory drug. aType of postoperative analgesia. bType of disease. *P<0.05.
Fig. 3.Forest plot of the multivariate analysis of postoperative urinary retention in patients with benign anorectal diseases. aOR, adjusted odds ratio; CI, confidence interval; WBC, white blood cell.
Table 1.The incidence of urinary retention in different types of disease
|
Type of disease |
Total (n=6,284) |
Non-POUR group (n=5,692) |
POUR group (n=592) |
|
Perianal abscess |
1,104 (17.6) |
1,041 (18.3) |
63 (10.6) |
|
Mixed hemorrhoids |
3,512 (55.9) |
3,057 (53.7) |
455 (76.9) |
|
Anal fistula |
1,525 (24.3) |
1,457 (25.6) |
68 (11.5) |
|
Anal fissure |
143 (2.3) |
137 (2.4) |
6 (1.0) |
Table 2.Univariate analysis of POUR in patients with benign anorectal diseases
|
Factor |
Non-POUR group |
POUR group |
Test statistic |
P-value |
|
Neutrophil (%) |
64.66±9.35 |
64.35±9.58 |
0.785 |
0.432 |
|
WBC count (109/L) |
5.99±2.48 |
5.58±2.01 |
–4.726 |
<0.001 |
|
Hemoglobin (g/L) |
146.0±24.0 |
136.5±21.0 |
–10.562 |
<0.001 |
|
Creatinine (μmol/L) |
70.0±21.0 |
82.0±20.0 |
–8.266 |
<0.001 |
|
Urea (mmol/L) |
4.79±1.71 |
4.73±1.85 |
–0.519 |
0.604 |
Table 3.Pairwise comparison of the length of hospital stay among patients receiving different anesthesia methods
|
Type of anesthesia |
Mean rank (hospital stay) |
Local anesthesia |
Epidural anesthesia |
Sacral canal anesthesia |
Subarachnoid anesthesia |
|
General anesthesia |
4,405 |
1,085*
|
1,331*
|
1,296*
|
659 |
|
Subarachnoid anesthesia |
3,746 |
1,146*
|
672 |
638*
|
|
|
Sacral canal anesthesia |
3,108 |
508*
|
34 |
|
|
|
Epidural anesthesia |
3,074 |
474 |
|
|
|
|
Local anesthesia |
2,600 |
|
|
|
|
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