Introduction

Inguinal hernia repair is a commonly performed surgery, with more than 20 million patients undergoing inguinal hernia repair worldwide each year [1]. Postoperative urinary retention (POUR) is a common complication after inguinal hernia repair, with a reported incidence of up to 27% [2,3,4,5,6,7,8,9,10,11,12]. POUR is defined as the need for urinary catheterization due to the inability to void the bladder spontaneously after surgery. Besides patient discomfort, it can lead to a higher incidence of urinary tract infection and injury and a longer hospital stay, and thus, higher overall costs [13]. Risk factors for POUR after open, laparoscopic, and endoscopic inguinal hernia repair have been studied, but the results vary. Most of these studies are retrospective small series with a heterogeneous study population that usually includes a mixture of open, laparoscopic, and endoscopic inguinal hernia repairs. Suggested risk factors comprise advanced age, history of benign prostatic hypertrophy, high intraoperative fluid administration, opioid use, diabetes mellitus, spinal anesthesia, and bilateral repair [2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Because there is no strategy to reduce POUR in high-risk patients and inguinal hernia repairs are increasingly performed in an outpatient setting, it is even more important to identify patients who are at risk of POUR to adapt clinical management, reduce readmission, and thus, reduce health-care costs.

Therefore, the objective of this study was to assess the incidence of POUR and determine its risk factors after inguinal hernia repair exclusively using an endoscopic total extraperitoneal (TEP) approach.

Materials and methods

Population

Since July 1, 2012, all patients undergoing a hernia repair at the Cantonal hospital of Baden, Switzerland who provided written informed consent for data documentation and analysis were prospectively registered in an international database, the HerniaMed Registry. A retrospective analysis of 1570 patients who underwent a TEP inguinal hernia repair between July 2012 and May 2018 was performed. Inclusion criteria were all elective or emergency TEP inguinal hernia repairs performed between July 2012 and May 2018. Exclusion criteria were patients who underwent a transurethral or suprapubic urinary catheter preoperatively, those without a urinary bladder, < 18 years old, and did not sign an informed consent form.

Surgical technique

The 1570 TEP inguinal hernia repairs were performed by or under supervision of 14 different experienced hernia surgeons, who all employed the same technique. Experienced hernia surgeons were defined as surgeons with more than 500 hernia surgeries performed, as defined by the German Society of Surgery DGAV [16]. Briefly, under general anesthesia, an infraumbilical 10-mm camera trocar was inserted into the preperitoneal space, which was dissected telescopically and inflated with CO2 at a pressure of 12 mmHg. The intervention was performed using two additional 5-mm trocars, either one in the midline and one lateral or both in the midline. The hernia sac was reduced but not resected or ligated. A mesh was used to cover all hernia orifices in all patients. Unilateral TEP inguinal hernia repairs were normally performed without, and bilateral TEP inguinal hernia repairs with, an indwelling urinary catheter, which was inserted immediately before surgery under general anesthesia. The urinary catheter was removed on postoperative day 1.

Mesh fixation and closed suction drain placement in the preperitoneal space were performed at the surgeon’s discretion. Traumatic mesh fixation was defined as fixation using a tacker or stitches, and atraumatic mesh fixation was defined as fixation with glue. Closed suction drain placement in the preperitoneal space was normally performed when there was expected postoperative hematoma, such as in patients with anticoagulation or difficulties during surgery or very large hernia sacks with expected postoperative seroma.

Study endpoints

The primary endpoint was to assess the incidence of POUR after TEP. POUR was defined as the inability to void the bladder spontaneously after surgery, requiring in-hospital urinary catheterization. Demographic data including preoperative and postoperative variables were identified to determine the risk factors that contributed to the incidence of POUR. Additionally, the influence of POUR on the length of stay and postoperative pain was analyzed. Demographic data and preoperative and postoperative variables were extracted from the HerniaMed Registry, in which all data are prospectively documented.

Statistical analysis

Statistical analysis was performed with the statistical software package R, [17] using two-sided statistical tests and confidence intervals with standard significance and confidence levels of α = 5% and (100% − α) = 95%, respectively. There were no missing data. Categorical data (gender, preoperative pain, previous prostate surgery, laterality, urgency of surgery, mesh fixation, and drain placement were nominal data and ASA class was ordinal data) are presented as the frequency and percentage, while continuous numerical variables (age, body mass index [BMI], and operative duration) are presented as the median and interquartile range (IQR). Univariable logistic regressions were used to separately examine the effects of age, sex, BMI, ASA classification, preoperative pain, previous prostate surgery, urgency of operation, laterality, operative duration, drain placement, and mesh fixation on the primary endpoint. Several studies [5, 10] identified > 50 years of age as a risk factor of POUR, and age was divided into two groups: 18–50 years and > 50 years. The impact of under- and overweight on POUR was investigated, and BMI was divided into three groups: < 19 kg/m2, 19–25 kg/m2, and > 25 kg/m2. Previous studies reported a median operative duration between 73 and 93 min [4, 10, 11]. Therefore, and according to the experience of our surgeons, operative duration was divided into three categories: < 60 min, 60–120 min, and > 120 min.

The effect of POUR on postoperative pain was analyzed using logistic regression. The effect of POUR on the length of stay was examined using negative binominal regression. Multivariable regressions with all the variables were performed as sensitivity analyses. The Holm–Bonferroni method was used to control the family-wise error rate (probability of type I errors when performing multiple hypothesis tests).

Results

Patient demographics

Among the 1570 included patients, 1416 (90.2%) were men and 154 (9.8%) were women. The median age was 57 (IQR 46–68) years, and the median BMI was 25.1 (IQR 22.9–27.4) kg/m2. Forty-six (2.9%) patients underwent previous prostate surgery.

Operative demographics

The median operative duration was 60 (IQR 45–75) minutes. In 868 (55.3%) patients, a unilateral inguinal hernia repair was performed, and 702 (44.7%) patients underwent a bilateral repair. Unilateral TEP repair was performed without routine placement of a urinary catheter, and bilateral TEP repair was performed routinely with a urinary catheter. Ultrapro™ Ethicon (lightweight, large-pore polypropylene with poliglecaprone) was used in 78%, Vypro II™ Ethicon (large-pore-sized multifilamentous polypropylene mesh with polyglactin) was used in 13%, 3DMax™ Lightweight Bard (three-dimensional polypropylene mesh) was used in 6%, and other meshes were implanted in 3% of patients. No mesh fixation was performed in 284 patients (18.1%). An atraumatic or traumatic mesh fixation was performed in 90 (5.7%) or 1196 (76.2%) patients, respectively. Intraoperative drain placement in the preperitoneal space was performed in 1140 (72.6%) patients.

POUR incidence and risk factors

Sixty-five patients (4.1%) developed POUR. Univariable logistic regression (Table 1) showed that age (p < 0.001), unilateral versus bilateral repair (p < 0.001), ASA class (p < 0.001), drain placement (p = 0.01), and previous prostate surgery (p = 0.031) were associated with POUR. After multivariable logistic regression (Table 2), age (p < 0.001), unilateral versus bilateral repair (p < 0.001), drain placement (p = 0.006), gender (p = 0.01), and preoperative pain (p = 0.04) remained associated with a significantly higher incidence of POUR. Only age and unilateral versus bilateral repair were associated with a significantly higher incidence of POUR after the Holm–Bonferroni correction for multiple testing, each increasing the odds of POUR. POUR was observed in 1.6% of patients 18–50 years old, 5.5% of patients > 50 years old, and 6.8% of patients > 60 old, which corresponds to an odds ratio of 1.05 for each additional year over 18 years of age.

Table 1 Univariate analysis of demographic, preoperative, and operative predictors of POUR
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Table 2 Multivariate regression of demographic, preoperative, and operative predictors of POUR
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Patients who underwent a unilateral compared to bilateral inguinal hernia repair had an over three-times higher risk of developing POUR. POUR was observed in 6.0% of patients who underwent unilateral inguinal hernia repair compared to 1.9% with bilateral inguinal hernia repair.

Postoperative outcome

The median length of stay was 2 (IQR 2–2) days. There was no effect of POUR on postoperative pain (p = 0.67) or length of stay (p = 0.11) in the univariable logistic regression.

Discussion

To the best of our knowledge, this is the largest study that has been conducted to date that investigated POUR after TEP inguinal hernia repair. We found an increased incidence of POUR in older patients and in patients with unilateral inguinal hernia repair. To obtain robust results, we applied a clear and easily measurable definition of POUR, which was the primary endpoint, thus preventing possible investigator-dependent variation. Furthermore, we chose to exclusively analyze TEP inguinal hernia repair to exclude the heterogeneity related to different surgical techniques.

To date, the reported incidence of POUR ranges from 0.8 to 27%. [2,3,4,5,6,7,8,9,10,11,12] The variation in the range of the reported incidence may result from the inconsistent definition and diagnosis of POUR, inclusion of different surgical and anesthetic techniques, and inclusion of outpatient and inpatient cases. Compared with our results, many previously published studies have described a higher incidence of POUR, as follows: 27% POUR in patients with preoperative urogenital symptoms [12]; 22% POUR when including both open and minimal invasive repairs [8]; and between 11 and 13% POUR despite inguinal hernia repair using an intraoperative urinary catheter [7,8,9,10,11]. However, a recently published study [2] found the incidence of POUR to be 0.8%. This study was performed using a selected group of expert surgeons, and it combined open and minimally invasive repairs. A possible bias for the low incidence could be that the international database that was used had an 18% exclusion rate due to missing data. Other studies [4, 5, 10] found an 8–11% incidence of POUR. In contrast to our study, these studies had different definitions of POUR and smaller study populations, and they included different surgical techniques.

To date, the most common risk factors for POUR after inguinal hernia repair have been advanced age [4, 5, 10, 11, 18], history of benign prostatic hypertrophy [4, 5], high intraoperative fluid administration [8], and opioid use [8, 10]. In our multivariable logistic regression analysis, we found that older age, male gender, preoperative pain, unilateral repair, and drain placement were significant. After correction for multiple testing, advanced age and unilateral inguinal hernia repair remained the only two risk factors for POUR.

With advancing age, various neurogenic and myogenic changes are seen in the detrusor muscle, which leads to diminished detrusor contractility and muscle strength [18]. Furthermore, older age can reduce anesthetic agent metabolism and correlate with an increased incidence of benign prostate hyperplasia, all of which favor the development of POUR [18]. In our population, we found that advancing age was associated with a significantly higher incidence of POUR, with an odds ratio of 1.05 for each additional year over the age of 18 years. Therefore, the risk of developing POUR is over 1.5-fold higher with each increasing decade of age. For example, a patient who is over 60 years old has an over four-times higher risk of developing POUR compared to a patient between 18 and 50 years of age. Older age is a clear risk factor for POUR, and this finding should be specifically considered in the perioperative treatment of older patients who are scheduled for inguinal hernia repair.

In our population, patients who underwent unilateral inguinal hernia repair showed a significantly higher incidence of POUR compared to patients who underwent bilateral repair. The most plausible explanation for this finding is that in contrast to bilateral hernia repair, we do not routinely place a urinary catheter during unilateral operations. By placing a urinary catheter in bilateral inguinal hernia repairs and leaving it until the postoperative day 1, we are most probably pre-emptively treating POUR in these patients. In the literature, bilateral inguinal hernia repair was found to be associated with a significantly higher incidence of POUR in two studies [5, 7], while other studies showed no significant association [4, 10, 11]. For routine intraoperative urinary catheterization, one study [11] showed intraoperative urinary catheterization to have no impact on the incidence of POUR. However, during the study, the protocol was changed from routine intraoperative urinary catheterization to catheterization at the surgeon’s discretion, and confounding factors were not systematically assessed. Another study showed a higher incidence of POUR, with an odds ratio of 2.5 in patients > 50 years of age, who underwent surgery without an intraoperative catheter [5]. The International Hernia Guidelines do not recommend a standard intraoperative urinary catheterization [1]. However, this recommendation is graded as “weak” due to moderate to low evidence on the subject. After analysis of our data, intraoperative catheterization seems to probably decrease the risk of developing POUR. Thus, intraoperative catheterization should be considered in high-risk patients. However, prophylactic urinary catheterization is also accompanied by potential complications, such as injury and urinary tract infection [11, 13]. Better prophylaxis for POUR would refrain from using invasive devices. A possible protective measurement may be the administration of an alpha-blocker. Alpha-blockers are being used to treat men with micturition disturbances such as diminished urinary stream in benign prostate obstruction syndrome by interacting with alpha receptors and reducing the alpha-adrenergic effect, resulting in muscle relaxation. The international guidelines for groin hernia management state that this medication may be effective in preventing urinary retention [1]. This is based on a few small pilot studies [19,20,21] that have shown a positive effect of Tamsulosin on POUR, but larger, well designed studies on this subject are required. Therefore, we are currently performing a randomized, quadruple-blind, placebo-controlled, multi-center trial, investigating prophylactic Tamsulosin to prevent POUR in older men after TEP inguinal hernia repair at our institution (Bieri et al., submitted BMJ Open). Because the risk of POUR is 1.5-fold higher with each increased decade of age and noninvasive prophylactic solutions for POUR are lacking, we will apply a tailored approach for intraoperative urinary catheterization in our clinic for older patients who are undergoing TEP inguinal hernia repair.

Patients who developed POUR did not stay significantly longer in the hospital compared to patients without POUR. In Switzerland, until January 2019, inguinal hernia repair was not routinely performed in an outpatient setting. Compared to other centers in other countries, the hospital stay in our study may, therefore, be longer. Most patients who developed POUR were successfully treated via urinary catheterization a few hours after surgery or on postoperative day 1, and the catheter was removed the following day, which did not exceed our standard of hospitalization of 2 days.

Correction for multiple testing is a strength of our study, and it may explain the higher number of significant results in the regular multivariate analysis (age, gender, preoperative pain, unilateral side, drain placement) compared to the final significant results after the Holm–Bonferroni testing (age and unilateral side). Other strengths are the use of a high-volume prospective database and a single surgical technique. Limitations are that previously identified risk factors, such as narcotic analgesia, fluid administration, and history of benign prostatic hyperplasia, were not included. The HerniaMed Registry did not provide any information about intraoperative fluid administration, history of benign prostatic hyperplasia, or use of narcotic analgesia, and therefore, no analysis of their impact on POUR could be performed.

Conclusion

After TEP inguinal repair, we found an increased incidence of POUR in older patients and patients undergoing unilateral repair, possibly due to a lack of perioperative urinary catheterization. Prospective studies to find noninvasive methods to prevent POUR in high-risk patients are required.