Urinary retention, the incomplete elimination of urine from the bladder, can cause severe post-renal kidney failure and urinary tract infections, both of which can have lethal consequences. In women, detrusor underactivity (DUA) is commonly believed to be the main cause for urinary retention. 
Trial catheter removal seems to be a good option for women as a less invasive and low-cost procedure, however, the efficacy of trial catheter removal for urinary retention in women has not been studied and real clinical evidence remains to be accumulated.
This study aimed to investigate the outcome of trial catheter removal for women with acute urinary retention and determine the predictors for the success of trial catheter removal. This study also evaluated the efficacy of oral alpha blockers and parasympathomimetics on trial catheter removal for women.

Consecutive patients who underwent trial catheter removal between July 2009 and July 2019 were enrolled and retrospectively analyzed in this study. The study was conducted in accordance with the principles set out in the Declaration of Helsinki and all local regulations.
In this study, urinary retention was defined as a post-void residual urine volume (PVR) >250 ml measured by ultrasound or computed tomography imaging with/without overflow incontinence. After diagnosis of urinary retention, a transurethral catheter was inserted to drain the residual urine from the bladder. Following at least one week of urethral catheter use, trial catheter removal was performed. 
Prior to catheter removal, drug treatment with alpha blocker alone or a combination of alpha blocker and parasympathomimetics (bethanechol or distigmine bromide) were used to facilitate spontaneous voiding in some cases, as determined by physicians. After instillation of warm saline (200-300ml or until the first desire to void), the urinary catheter was removed and residual urine was measured after the first void or 6 hours later. The trial was defined as non-success if the PVR was >150 mL or the patient experienced difficulty emptying their bladder with abdominal discomfort or pain, and a transurethral catheter was reinserted.
The patients’ characteristics including age, ECOG performance status (PS), body mass index (BMI), blood test parameters and comorbidity, were retrospectively compared according to the outcome of trial catheter removal. Multivariate regression models were used to find the predictors of successful trial outcome and evaluate the impact of any medication on trial outcome.

Fifty-nine of 104 (56.7%) women with urinary retention were catheter free post-trial. There was no significant difference between successful and non-successful trial in: average age (P=0.392), median PS (P=0.374), diabetes mellitus (P=0.842), dementia (P=0.801), or previous history of cerebrovascular events (P=0.592), or intra-pelvic surgery (P=0.800). Oral medications were administered for 39/59 (66.1%) in the success group and 30/45 (66.7%) patients in the non-success groups (P=0.598).
Blood tests showed that the serum albumin (3.2 ± 0.7 and 2.8 ± 0.8, P=0.039) and total protein values (6.5 ± 0.8 and 6.0 ± 1.0, P=0.038), were higher in the success group than the non-success group, respectively. There were no significant differences in serum values including creatinine, white blood cell, neutrophil, hemoglobin or platelet count between the success and non-success groups.
Multivariate logistic regression found that a serum albumin >3 g/dL was an independent predictor of successful trial catheter removal for women with urinary retention [P=0.030, odds ratio (OR) 3.3, 95% confidence interval (C.I.) of OR 1.1 – 9.9)] (Table). Age <70 years-old was a likely predictor of successful trial catheter removal (P=0.066, OR 4.8, 95% C.I. of OR 0.9 – 25.0).

Albumin is major of serum protein and usually represents the patient’s whole nutrition status and liver function. Hypoalbuminemia in adults is defined as an intravascular albumin level <3.5 g/dL. Potential mechanisms for hypoalbuminemia include decreased synthesis (liver disease, protein malnutrition), increased tissue catabolism (sepsis), renal loss (nephrotic syndrome), gastrointestinal loss (protein-losing enteropathy), or a change in distribution (sequestration). Hypoalbuminemia was reported to be associated with overactive bladder in patients with liver cirrhosis. Also, hypoalbuminemia is a well-known risk factor for mortality and other poor outcomes in various clinical settings, including wellness promotion, admission to hospital and even treatment of coronavirus disease 2019. Similar observations have been made in the surgical patient population, where hypoalbuminemia has been predictive of the need for reoperation, a prolonged hospital stay, wound complications, renal failure, gastrointestinal dysfunction, and mortality. However, the pathophysiology behind these relationship remains to be elucidated. Albumin might serve as a nutritional marker, such that hypoalbuminemia represents poor nutritional status in patients who go on to experience poor clinical outcomes. Also, albumin is known to be a negative acute phase protein, and as such hypoalbuminemia might represent increased inflammatory status for the patient, which potentially leads to poor outcomes. This study demonstrated the relationship between hypoalbuminemia and the outcome of trial catheter removal and suggested that catheter removal trial should be performed for women with a serum albumin value >3 mg/dL. 

Meanwhile, we hypothesized that aging, PS, diabetes mellitus, dementia (as these patients have a higher risk of neurogenic bladder than the general population) and previous cerebrovascular events were possible candidates to predict the outcome of trial catheter removal. Indeed, a previous study investigating urinary retention elderly women undergoing rehabilitation found that diabetes mellitus and poor PS were prognostic factors for recovery failure from urinary retention. Surprisingly, contradicting our hypotheses and the previous study, none of the factors we suggested had an effect on the outcome of trial catheter removal. Those findings suggested that even low PS and potential neurogenic bladder may not be preclude for trial catheter removal at least in patients with serum albumin value >3 mg/dL and age <70 years.

The parasympathomimetic agents, bethanechol and carbachol, have previously demonstrated variable effects on DUA. A previous study indicated that bethanecol enhanced bladder wall stiffness and sensory perception. Another study demonstrated that bethanechol reduced the bladder sensory threshold in women with DUA. Given the questionable efficacy of parasympathomimetic agents in treating DUA and dose-dependent systemic adverse events, including fatal overdose, the use of those drugs is limited. This study found that parasympathomimetics showed no beneficial effects on achieving catheter free status.

Alpha-adrenoreceptor antagonists are another agent which may be beneficial for women with DUA as they may reduce bladder outlet obstruction via alpha receptors in the bladder neck and proximal urethra. A recent meta-analysis found that alpha1-blocker therapy was more effective than placebo in reducing LUTS, but there were no beneficial effects of alpha-1 blockers in maximum uroflow rate or PVR when compared to placebo. Our findings suggest that alpha-1 blocker therapy in women with LUTS may not improve the outcome of catheter removal trial.

This is the first study to investigate the predictors of catheter free status after trial catheter removal for women with urinary retention. We found that a serum Albumin value >3 mg/dL was a significant independent predictor of catheter free status after trial catheter removal. Although an age <70 years was also a possible contributor (without reaching statistical significance), PS, diabetes mellitus, dementia and previous cerebrovascular events or intra-pelvic surgery had no influence on the outcome of trial catheter removal. The secondary outcome for this study aimed to assess the efficacy of oral medications, for the treatment of urinary retention. We found no evidence to demonstrate that these medications were beneficial in this regard.