Diagnostic challenges in the evaluation of persistent or recurrent urinary incontinence after artificial urinary sphincter (AUS) implantation in patients after prostatectomy
Department of Urology, Princess Alexandra Hospital, Brisbane, QLD, Australia
Pelvic Medicine Centre, St Andrew's War Memorial Hospital, Brisbane, QLD, Australia
Department of Surgery, University of Queensland, Brisbane, QLD, Australia
Correspondence: Eric Chung, Department of Urology, Princess Alexandra Hospital, Brisbane, QLD 4103, Australia; and St Andrew's Pelvic Medicine Centre, St Andrew's War Memorial Hospital, Spring Hill, QLD, Australia.
There is a lack of information pertaining to the postoperative evaluation in patients with artificial urinary sphincter (AUS) implants who complain and continue to have urinary incontinence (UI). Two types of UI can occur after the activation of an AUS device these are: early or initial (persistent) UI, and delayed (recurrent) UI. There are many causes of persistent and/or recurrent UI and these can sometimes overlap. The potential causes include improper and/or accidental operation of the pump-control unit, overactive bladder, cuff atrophy, cuff erosion, improper cuff size and pressure-regulating balloon unit, as well as device malfunctions. The diagnostic evaluation in men with persistent and/or recurrent UI after AUS implantation requires sufficient understanding of the AUS mechanics and is a step-wise and logical process with careful history and thorough clinical evaluation. Once a diagnosis is made, patients should be counselled and appropriate treatment instituted.
The incidence of men with post-prostatectomy urinary incontinence (UI) remains high despite advances in surgical technologies and techniques. Although most post-prostatectomy UI resolves within months after conservative measures with pelvic floor muscle exercise, some 5–10% of men continue to experience bothersome UI 12 months after prostatectomy and therefore more invasive treatment options must be explored .
The artificial urinary sphincter (AUS) is considered by many to be the standard of care for men with severe UI and/or post-prostate cancer radiotherapy-related UI . The hydraulically controlled AMS 800TM (American Medical Systems, Minnetonka, MN, USA) is the most commercially successful and effective AUS device on the market. This ingenious device consists of three components; a control pump, an inflatable cuff, and a pressure-regulating balloon (PRB), which serves dual functions, both as a pressure regulator and also as a fluid reservoir. While the long-term effectiveness, safety, and durability of the current model of the AMS 800 are well documented, it is not without its limitations and complications .
Presently, there is an abundance of literature on patient selection, surgical techniques and clinical outcomes in AUS implantation [3-7]. However, there is a lack of information pertaining to the postoperative evaluation and management in patients with AUS implant who complain and continue to have UI. Mechanical and non-mechanical failures of AUS are not uncommon and the presence of UI after AUS implantation can be devastating to patients and disappointing to the surgeon. The two types of UI that can occur following the activation of an AUS device are early or initial (persistent) UI, and delayed (recurrent) UI . In cases of persistent UI, these men never regain urinary continence after activation of the AUS device and experience leakage, often in a manner similar to that experienced before implantation and during the period of deactivation. On the other hand, delayed or recurrence of UI usually occur after several months or years after AUS implantation.
The following article explores the postoperative diagnostic evaluation of men with an AUS implant who have persistent UI, or the subsequent delayed recurrence of UI after a period of continence.
There are many causes of persistent and/or recurrent UI and these can sometimes overlap. The potential causes include improper and/or accidental operation of the pump control unit, UTI with detrusor overactivity, de novo overactive bladder, urethral cuff atrophy, urethral cuff erosion, improper cuff size and PRB unit, development (recurrence) of urethral or bladder neck stricture, as well as device malfunctions from fluid loss and occlusion of the control unit [7-9]. Fortunately, a careful history and thorough clinical evaluation can often reveal the problem.
Persistent (or Early) UI after Activation of AUS
Improper operation of AUS device
Improper operation of the AUS device is the commonest cause of immediate post-activation UI and is a result of failure to deflate the urinary cuff completely. Inadequate cuff deflation and/or inadvertent activation of the locking mechanism can lead to incomplete bladder emptying and subsequent overflow incontinence. Fortunately, failure of the sphincteric cuff to inflate and deflate on activation of AUS device in the early postoperative period is extremely rare [2, 3, 8, 9]. A poorly placed control pump in the scrotum can be accidentally compressed and cause unintentional cuff deflation and UI. To diagnose this problem, a history of UI with certain body positions should be noted or careful evaluation of control-pump techniques should be undertaken. Patients should be taught how to completely deflate the cuff and understand that bladder emptying takes time and repeated recycling of the AUS device may be necessary.
De novo overactive bladder or overactive bladder secondary to UTI
De novo overactive bladder is not common in patients after radical prostatectomy compared with patients with an enlarged and obstructive prostate gland . Most men with BPH develop a degree of overactive bladder secondary to chronic bladder adaptive changes. A trial of anti-cholinergic medication should be prescribed as part of first-line management for men with UI after prostatectomy to exclude a component of overactive bladder. Detrusor overactivity may occur in association with UTI. A simple urinary microscopy and culture will ascertain the presence of UTI and if present an appropriate course of oral antibiotic should be prescribed.
Incorrect cuff and/or PRB size
Another cause of early UI after AUS implantation is a loose-fitting or oversized cuff as well as incorrect PRB size. The usual measurement for a bulbar sphincteric cuff circumference is 4–4.5 cm (±0.5 cm). Of course this problem can be avoided in the first place by avoiding extensive peri-urethral tissue dissection during cuff placement, proper intraoperative cuff sizing and urethroscopic evaluation to ensure adequate mucosal coaptation once the cuff is in place and fully inflated. If the patient never achieves continence after AUS activation, the most common problem is either too large a cuff or too small a PRB. The diagnosis of a loose fitting cuff is made by clinical review of the surgical notes, urethral pressure profilometry and urethroscopic evaluation. Urethral pressure profile study is a non-radiological test of sphincter function. A normal closing urethral pressure differential of 40–50 cmH2O should provide effective urethral compression.
Early AUS cuff erosion
One of the most feared complications after AUS implantation is cuff erosion. Cuff erosion can be classified as early or late. Early postoperative cuff erosion usually occurs from unrecognised and/or inadvertent injury to the bulbar urethra during posterior dissection. The presence of peri-catheter blood at the time of urethral dissection is a tell-tale sign of urethral injury. Urethral cuff placement should be abandoned in the presence of bulbous urethral injury and re-implantation of the AUS cuff can be carried out after 6–8 weeks of urethral catheterisation. The presence of haematuria after the removal of urinary catheter is another sign of early cuff erosion. The diagnosis of cuff erosion is best confirmed with urethroscopy.
Recurrent (or Delayed) UI
A common cause of recurrent or delayed UI after AUS implantation is tissue atrophy. In fact, tissue atrophy is probably the most common cause of non-mechanical failure and also the most common cause for AUS revision [4, 7, 9]. Since 1987, the incidence of tissue atrophy has decreased considerably with the introduction of a narrow-backed cuff [2, 3]. Tissue atrophy results in loss of urethral compression and luminal occlusion. Patients who were initially continent with the device complain of gradually increasing UI over months or even years and report having to squeeze the pump more often to deflate the cuff and void. If the cuff inflates and deflates normally but the patient remains incontinent, tissue atrophy should be suspected. If the number of pump cycles required for voiding increases, tissue atrophy should also be suspected. Withdrawal urethral pressure profile can be conducted with the cuff in inflated and deflated modes. Minimal pressure change between the two modes suggests either cuff–periurethral tissue atrophy or sphincteric malfunction. Urethroscopic evaluation will show ischaemic changes to the bulbar urethra and poor mucosal coaptation when the cuff is fully inflated.
Late AUS cuff erosion
As discussed in the previous section, most cuff erosions usually occur around 3–6 months after implantation and invariably results in prosthesis infection . Later causes of erosion are frequently related to urinary catheterisation with a non-deflated cuff, but erosion may also occur from excessive cuff-urethral pressure necrosis. The risk factors for cuff erosion include pelvic radiation, excessive cuff pressure, undersized cuff, and retrograde instrumentation without deactivating the AUS device properly [5, 7]. A history of recent instrumentation, e.g. urethral catheterisation, without prior deactivation of the device is likely to herald cuff erosion. Early clinical signs of possible cuff erosion include the onset of bloody discharge or gross haematuria, and presence of irritative urinary symptoms, e.g. dysuria, frequency and urgency. When cuff erosion occurs as a delayed UI, signs of urinary extravasation are not common due to the fact a well-formed pseudocapsule around the cuff contains and restricts soft tissue extravasation of urine. The diagnosis of cuff erosion is again best confirmed with urethroscopy. The eroding cuff should be removed and urethral catheterisation undertaken. Small urethral defects usually heal spontaneously after 2–3 weeks of catheterisation without the need for surgical closure. The intraoperative finding of signs suggestive of infection, e.g. purulent discharge or inflamed tissue, indicates the need to remove the remainder of the device. In the presence of an infected prosthesis, secondary implantation of a new device should be deferred for 3–6 months. Previous cuff erosion is not an absolute contraindication to subsequent cuff replacement around the bulbar urethra but is associated with increased risk of future erosion compared with virgin cases [11, 12].
Device malfunctions, e.g. fluid loss and/or inability to recycle the AUS device, can present with recurrent UI. Potential sources of fluid loss include the inflatable cuff, disruption in tubing and tubing connections, leak in PRB or control-pump unit, while those with control-pump malfunction are kinking in the tubing or occlusion of the control assembly from particulate matter. The introduction of a fluoro-silicone layer between the two cuff leaflets and kink-resistant tubing has minimised the majority of the fluid leaks [2, 3]. However, disruption near the tubing connections remains an issue. Simple plain abdominal radiography can exclude loss of fluid from the PRB if contrast solution is used as a filling medium. Inflate-and-deflate radiographs allow for assessment of sphincteric cuff fluid. When the cuff is open, the pump and PRB should contain some fluid, and the cuff should have none. When the cuff is closed, a ‘doughnut-like’ circumferential ring of contrast should be visible at the cuff site. If the radiographic contrast is absent, a leak has occurred. If isotonic solution, e.g. sodium chloride, is used as the fluid medium, a lower abdominal ultrasonography or non-contrast CT abdomen and pelvis can assist to assess the volume in the PRB and diagnose fluid loss. In situ examination of the cuff for leakage is best done with electrical testing. Electrical conductance testing (using an ohmmeter) can be useful in identifying the faulty component and site of the leak at the time of operation. Leaks at connector sites, cuff and PRB can be measured by connecting the tubing to a pressure transducer or by aspirating and measuring the volume in the balloon. The PRB integrity can be tested easily by filling this component with 20 mL saline before measuring the instilled volume after 10–15 min. However, hydraulic testing may be misleading and reveal false negative findings if the leak is minimal.
The current AMS 800 AUS device has restored the quality of life to thousands of patients plagued by severe stress UI . Presently, it is still considered by many as the standard of care for men with UI after prostatectomy and is associated with excellent social continence rates [1, 2]. The improvement in AMS 800 design and product materials over the last 40 years has made this device highly effective, durable and safe. Nonetheless, like any mechanical device, it has its own limitations and complication rates. Therefore strict patient selection criteria and adherence of sound surgical principles and fastidious postoperative care are paramount to ensure an optimal clinical outcome.
The diagnostic evaluation in men with persistent or recurrent UI after AUS implantation requires sufficient understanding of the AUS mechanics and is a step-wise and logical process. Once a diagnosis is made, patients should be adequately counselled and appropriate treatment should be instituted. Future management strategies undoubtedly will vary with improvement in the current AMS 800 device, as well as emergence of other novel devices.