Acute urinary retention (AUR) is a common urological emergency in men and is defined as a sudden and painful inability to pass urine voluntarily [1]. It is estimated that 10% of men in their 70s and a third of men in their 80s will experience AUR within the next 5 years [2]. As a primary treatment of AUR caused by benign prostatic hyperplasia (BPH), early transurethral prostatectomy (TUR-P) has been frequently performed because it is known to bring about prominent improvement in lower urinary tract symptoms (LUTS) [3]. However, one should not overlook the complications and risks of TUR-P, which can be problems on their own [4]. Murray et al. [5] reported that 23% of study subjects did not require prostatectomy as the result of a urodynamic study performed in patients with AUR. In another study, Pickard et al. [6] reported that about 9.2% of patients who had undergone TUR-P could not perform self-voiding after the surgery so that urethral catheterization and clean intermittent catheterization had to be conducted. Of these patients, 0.9% had to undergo permanent urethral catheterization. Pickard et al. [6] also reported that prostatectomy in patients with a history of AUR had a large risk of postoperative complications.

Management of AUR consists of immediate bladder decompression by catheterization, which is usually followed by BPH-related surgery [7]. Surgical intervention in the presence of a urinary catheter can also lead to an increased risk of sepsis, which potentially contributes to the observed increase in operative morbidity, especially in older patients [8,9]. These findings led to the increasing use of trial without catheter (TWOC) [7]. Recently, TWOC, which is a therapeutic method to induce self-voiding after a certain period of urethral catheterization, is being attempted in many patients with AUR. However, there is no consensus on the optimal management of AUR in terms of type and duration of catheterization or postcatheterization management. Therefore, this study analyzed the type of AUR and evaluated the treatment methods of AUR.

AUR is a common urological emergency in men and is defined as a sudden and painful inability to pass urine voluntarily. AUR represents the most common indication for BPH-related surgery, but its management is still not standardized because of a lack of existing guidelines [10]. Manikandan et al. [11] administered a questionnaire survey to 264 urologists in the United Kingdom on early treatments for BPH-caused AUR and reported that 98% of respondents used urethral catheterization and 70.5% used α-blockers concurrently with urethral catheterization.

Also, Taube and Gajraj [12] and Kumar et al. [13] reported in their studies that urethral catheterization was used as the initial treatment of AUR and that when patients were successful in self-voiding, the AUR recurred only in a small number of patients. They suggested that when patients with AUR have successful posturethral catheterization self-voiding, surgical treatment of BPH can be delayed or even avoided. A number of therapeutic options are available for AUR, ranging from medical therapy (usually α-blockers) to positioning of an indwelling catheter (or intermittent catheterization) and surgery. However, owing to the urgent nature of the problem and the need for fast and definitive treatment, immediate catheterization is often the first approach taken by urologists [14]. By analyzing clinical prognosis when urethral catheterization is used in patients with AUR, it will be possible to identify the appropriateness of TWOC as a primary treatment of AUR. In this study, compared with the patients in group P, the patients in group S were more likely to be treated by surgery, either immediately or after prolonged catheterization. Furthermore, the success rate of TWOC was more than 70% for any type of AUR. TWOC is therefore recommended in the treatment of AUR.

Fitzpatrick et al.'s study [10] identified factors predicting failure of TWOC in patients who had been treated for AUR with the use of an indwelling catheter. In this worldwide survey of 6,074 men aged over 70 years, prostate mass >50 g was shown to be a predictor of TWOC failure, and those patients required either further catheterization or surgery. The size of the prostate is a known risk factor for AUR [2,15]. McNeill et al. [16] reported that when the size of the prostate is larger, AUR continues or has a high probability of requiring surgical treatment even after self-voiding has been achieved. When the size of prostate was rather small, they suggested that the AUR likely originated from other underlying causes, and in such cases, no surgical treatment is required. Daly et al. [17] reported that patients with elevated PSA (>2.9 ng/ml), a large prostate size shown on a digital rectal examination (DRE), and a volume drained at the time of catheterization of >1,000 ml are best managed by surgical intervention, whereas patients with volumes drained at the time of catheterization of <1,000 ml, a PSA≤2.9 ng/ml, and moderate to small prostates on a DRE may be managed medically. In this study, compared with the patients in group S, the patients in group P were characterized by a smaller prostate on TRUS and a lower PSA level. We analyzed the success rate of TWOC in the aspects of age, prostate size (TRUS), and PSA level regardless of type of AUR. Patients with AUR who were older than 70 years, had an enlarged prostate ≥50 ml, and had a higher PSA level (≥3 ng/ml) were shown to have a lower success rate of TWOC. In this study, we focused on the presence or absence of AUR-triggering factors regardless of the size of the prostate. Also, we identified that the presence of AUR-triggering factors increased the overall success rate of TWOC.

Taube and Gajraj [12] reported that when the urinary retention volume was ≥900 ml, it was highly probable that TWOC would fail in patients with AUR. Likewise, Djavan et al. [18] reported that when the urinary retention volume was ≤1,000 ml, there was likely a higher probability of self-voiding to succeed, whereas when urinary retention volume was ≥1,300 ml, the duration of catheterization should be extended. Fitzpatrick et al. [10] reported that a drained volume at catheterization of ≥1,000 ml influenced the success rate of TWOC, whereas catheterization for >3 days did not influence TWOC success but was associated with increased morbidity and prolonged hospitalization for adverse events. In the present study, the success rate of TWOC in patients with a drained volume at catheterization of ≥1,000 ml was lower than the success rate of TWOC in others. Patients with a catheterization time of ≥3 days were very small in number (n=28). Thus, we divided the patients into those with catheterization ≥5 days and those with catheterization <5 days. There was no significant difference in the success rate of TWOC in patients with catheterization ≥5 days and the success rate of TWOC in others.

BPH-induced AUR is considered to result by the sudden stimulation of the α₁-adrenergic receptor that enhances contraction of the smooth muscle located between the prostate and the prostatic capsule, which leads to an increase in resistance of the bladder outlet [19,20]. Although it is known that α-blockers can delay BPH-induced AUR but cannot reduce the risk of cumulative incidence [21], several reports have suggested that the post-AUR use of α₁-blockers prevents the recurrence of AUR and increases the success rate of self-voiding [9,18,22,23]. α₁-Blockers are known to increase the maximal urinary flow and to reduce intravesical pressure, urethral opening pressure, and maximal intravesical pressure, thereby helping to start urination and its maintenance by lowering the intravesical pressure required for urination [24]. Fitzpatrick et al. [10] reported that most men (86%) received an α₁-blocker (mainly alfuzosin) before catheter removal with consistently higher TWOC success rates, regardless of age and type of AUR, and multivariate regression analysis confirmed that the use of an α₁-blocker before TWOC doubled the chances of success (odds ratio, 1.92; 95% confidence interval, 1.52 to 2.42; p<0.001).

This study was conducted as a retrospective, multi-center study with various α₁-blockers being used by each institution. Most of the patients' records did not record the previous intake history of α₁-blockers or the duration of such intake. Thus, we could not analyze the influence of α₁-blocker use before TWOC on the success rate of TWOC.

The potential limitations of our study are as follows: 1) the subject number was insufficient because patients from a multi-center hospital participated in this study. 2) Because this study was a retrospective, multi-center study, we checked out the medical records of the patients but we could not get information on variables such as the history of use of α₁-blockers before TWOC, symptoms of LUTS, etc.

A further large-scale, prospective study is required to investigate the multiple factors that can influence the success rate of TWOC. Such a study will help to identify the predictors of successful TWOC. Also, the success rate of TWOC depending on the kinds of α-blockers used and previous intake history should be examined in further studies.

Among the AUR patients studied, the group with spontaneous AUR (54%) was somewhat larger than the group with precipitated AUR (46%). The success rate of TWOC was more than 70% regardless of the type of AUR. Although TWOC is recommended primarily in the treatment of AUR, early surgical intervention should be considered if a patient has an enlarged prostate (≥50 ml) or a large drained volume at the time of catheterization (≥1,000 ml).