Description of the condition
Postoperative urinary retention (POUR) is the inability to pass urine following surgery despite a full bladder (painful, palpable or percussible). Although POUR is usually transitory, in some cases it can be prolonged, especially if not identified and managed appropriately.
The incidence of POUR appears to vary between surgical populations and prevalence estimates are affected by varying diagnostic standards. What seems clear, however, is that it is not an uncommon postoperative complication, as the following evidence indicates.
On discharge from the recovery room, POUR plus an ultrasonically measured bladder content of more than 500 ml was recorded in 23.7% of patients and POUR plus a bladder content of more than 600 ml was recorded in 16% of patients following mixed elective surgeries (Keita 2005; Lamonerie 2004).
POUR plus a bladder content of more than 500 ml resulted in the catheterisation of 69% of men and 39% of women amongst older patients, with a median age of 69 years, following primary total hip or knee arthroplasty (Sarasin 2006).
Twenty-four hours after surgery, POUR, defined as a palpable or distended bladder and a need for catheterisation following failed attempts to void, was present in 16.7% of patients following surgery for benign anorectal disease under spinal anaesthesia. Incidence was 21.9% for haemorrhoidectomy and 29.2% for rectal prolapse surgery (Toyonaga 2006).
POUR was detected ultrasonically in 9.2% of gynaecological surgery patients 24 hours after their operation. Prevalence varied according to type of operation: laparotomy (excluding hysterectomy) 55.6% (5/9); abdominal hysterectomy 13.7% (17/124); laparoscopically assisted vaginal hysterectomy 8.3% (2/24); laparoscopy 1.2% (1/83); genital prolapse 3.4% (1/29) (Bodker 2003).
POUR was present in 5.5% of patients four to seven days after open resection for colorectal cancer: prevalence was 9.1% and 1.7% amongst patients with rectal and colon cancer, respectively (Changchien 2007).
The wide range of POUR rates reflects its varied and often multifactorial etiology, with increased risk associated with surgical, anaesthesiological and patient factors. The increased risk of POUR observed after pelvic surgery may relate to damage to the innervation of the lower urinary tract, and spasm of the pelvic floor muscle and sphincter due to pain. Some of the drugs administered during anaesthesia and surgery, such as anticholinergics, sympathomimetics, and beta-adrenergic blockers, interfere with bladder function. Anticholinergics, such as atropine, and beta-adrenergic blockers inhibit detrusor contractions and cause bladder relaxation; sympathomimetics, such as adrenaline (epinephrine) and clonidine, increase urethral sphincter contraction. Longer surgeries and high volumes of intravenous fluids administered during surgery, which can result in bladder overdistention and inhibited detrusor function, have also been found to influence the development of POUR (Baldini 2009). Patient characteristics such as age and diabetes mellitus have also been associated with increased risk of POUR (Keita 2005; Lamonerie 2004; Sarasin 2006; Toyonaga 2006).
While normal voiding is re-established, the management of POUR has two main aims: (i) emptying the bladder to prevent discomfort and urinary tract infection caused by stasis; (ii) avoiding over-distension of the bladder, which can result in long-term bladder dysfunction, especially in the elderly. Prolonged POUR that is left untreated can result in hydronephrosis and the possibility of kidney damage leading to chronic kidney disease.
Postoperative urinary retention is most commonly managed by catheterisation. However, catheterisation of any kind can cause discomfort and distress to the patient and all forms of catheterisation are associated with some risks. Intermittent catheterisation is an effective management option for POUR but may not be feasible or acceptable for all patients. Indwelling urethral or suprapubic catheters are also effective but can cause discomfort and distress to the patient. Catheterisation of any kind is associated with a risk of urinary tract infections and other complications such as detrusor overactivity (Niel-Weise 2005; Phipps 2006).
Even when managed appropriately, POUR can lead to delayed discharge from hospital, which can result in inconvenience for the patient, increased care costs and reduced hospital bed availability. A separate Cochrane review is available covering drugs for the treatment of postoperative urinary retention (Buckley 2010).
Thus, the prevention of POUR is desirable where possible, yet there is little consensus on what pharmacological options may be effective as prophylaxis.
Description of the intervention
Several drugs have been used in an effort to prevent POUR. These include:
(1) cholinergic agents such as bethanechol, carbachol, physostigmine and neostigmine;
(2) alpha-adrenergic blockers such as tamsulosin, alfuzosin, terazosin and doxazosin; and
(3) prostaglandins such as PGD2, PFGE2, PGF2, PGI2 and thromboxane A2.
How the intervention might work
It is believed that POUR may be prevented by these agents by either enhancing bladder contraction or decreasing bladder outlet resistance when administered during the perioperative period.
Cholinergic agents facilitate detrusor smooth muscle contraction by either mimicking the effect of acetylcholine or by blocking the acetylcholinesterase enzyme allowing the sustained effect of acetylcholine. Acetylcholine is the principal neurotransmitter that stimulates the contraction of the bladder smooth muscles.
Alpha-adrenergic blockers cause relaxation of the smooth muscles of the bladder neck and urethral sphincter. Such relaxation decreases the resistance of the bladder outlet, allowing a stronger flow or stream of urine out of the bladder.
Prostaglandins are believed to have an excitatory effect on urinary bladder function via modulation of the afferent pathways. Several findings also suggest that prostaglandin directly stimulates detrusor contraction (Park 1999).
Why it is important to do this review
The evidence base for the use of these drugs for POUR prevention is questionable. A systematic review of existing evidence and resultant guidance on the effectiveness of pharmacological treatments for the prevention of POUR will help clinicians and patients to best decide whether such management is appropriate and effective.
This review will assess all current eligible trial-based evidence for the effectiveness of all relevant drugs in the prevention of POUR, with the intention of informing best practice.