A national health disservice? Improving catheters

Materials World magazine
1 Mar 2014

Long-term catheterisation causes significant damage and infection – perhaps not surprising when you consider that the current catheter design was developed more than 50 years ago. Emeritus consultant urologist Professor Roger Feneley examines the issues surrounding catheter design, and calls on the biomaterials sector to help improve quality of life for an ageing population. 

Over the majority of medical fields, quality of life for millions of the elderly is being transformed worldwide with the advent of a new generation of medical implants such as artificial joints, heart valves and cataracts. But the lack of a safe, reliable urine collection system presents an urgent and unmet healthcare need. Incontinence pads provide an alternative but, unless regularly changed, can lead to pressure sores. If healthcare priorities are selected by clinical need, a safe and reliable urine collection system should be placed high on this agenda. Currently, the long-term indwelling urinary catheter connected to a urine collection bag provides the world’s only implantable device to aid the palliative management of bladder dysfunction.

Bladder drainage has long been performed to relieve the pain and distress of a bladder that fails to empty, by passing a catheter through the urethra. The catheter evolved more by serendipity than applied science, through a protracted gestation that still leaves critical challenges to be resolved. Ancient manuscripts describe the use of reeds, a bronze catheter was discovered in the ruins at Pompeii, and by the 16th Century, the malleability and antiseptic properties of silver were attracting attention. The discovery of rubber eventually led to gum-elastic and latex, and now synthetic biomedical materials are providing catheters with the necessary tensile strength, flexibility, rigidity and lubricity.

Bladder function involves both storage and evacuation of urine, but inability to store causes humiliating incontinence. Historically this was considered a moral problem – in the 19th Century, French physician Armand Trousseau advised doctors to threaten chastisement for children and shame on the adult. In the 1950s, urinary incontinence did not appear on the medical curriculum because the subject possessed no scientific basis for study, but that changed dramatically with the birth of urodynamic studies, when pressure/flow measurements were introduced. Urine leaks from the bladder when the intravesical pressure overcomes the urethral closure pressure, and that objective approach generated a revolution in the diagnosis and pathophysiology of functional bladder disorders.

By intermittently filling and emptying, the bladder controls the constant diurnal flow of one to one-and-a-half litres of urine that pass through its cavity from the kidneys. This cycle is co-ordinated by interaction between the bladder and urethral sphincter mechanism. As the bladder muscle relaxes to enable the bladder to fill with urine (to a capacity of around 350–500ml), the urethral sphincter contracts to close its lumen. By voluntary relaxation of the sphincter, the urethra opens, triggering reflex contraction of the bladder muscle that is maintained until all the urine has been evacuated. This coordinated reciprocal activity between bladder and urethra is controlled through the complex neurological pathways between the brain and organs. Any pathological damage to the organs’ anatomical structure or nerve pathways can seriously disturb this co-ordination, causing dysfunction to storage and/or emptying of urine.

An age-old solution
Intermittent self-catheterisation (ISC) is considered the optimal method of draining urine from a bladder that fails to empty. Advocated by Everard Home in 1806, men suffering urine retention would carry a catheter in their top hats or walking sticks, a practice that continued until the turn of the 20th Century when prostatic surgery allowed removal of the obstruction at the bladder neck. The management of bladder dysfunction arising from spinal cord injuries during the world wars provoked considerable debate until intermittent catheterisation was reintroduced in 1966, by German-born British neurologist Professor Sir Ludwig Guttman at Stoke Mandeville hospital, Buckinghamshire. Shortly after, in 1972, urology specialist Dr Jack Lapides prescribed intermittent self-catheterisation for patients who failed to empty their bladders because of neurological conditions such as multiple sclerosis, warning that overdistension caused reduced blood supply to the bladder wall and increased vulnerability to infection. ISC continues to provide the gold standard – performed at regular intervals four to five times a day, it mimics normal bladder function, avoiding the accumulation of residual urine and overdistension of the bladder wall. However, because ISC requires the patient to possess sufficient mobility, manual dexterity and cognitive ability, its application is restricted.

Designing a catheter that could be retained in the bladder for continuous drainage has presented, and still presents, a major challenge. Continuous catheterisation of the bladder introduced serious complications from urinary tract infections. To reduce this risk, in 1925, physician and pathologist Sir Cuthbert Dukes stressed the importance of connecting the catheter to a sterile container, introducing the concept of a closed drainage system that is still considered an important prophylactic measure today. At the same time, his colleague John Percy Lockhart-Mummery emphasised the need to avoid accumulation of residual urine in the bladder. But it was not until Ashton Miller et al re-emphasised the need for closed aseptic drainage in 1958 that this became routine practice.

The first reliable indwelling urinary catheter was designed by American urologist Dr Frederic Foley, who developed the hemostatic bag catheter to provide simultaneous drainage of the bladder and hemostasis following transurethral resection of the prostate. The original catheter was assembled by cementing together the constituent parts – the catheter, bag and bag distension duct – but it became possible to construct the whole device as a one-piece, integral catheter using the new latex method, in which Foley noted that the urethra tolerated latex better than red rubber. When presented to the American Urological Association in 1935, he described the result as ‘the finally perfected catheter’, and in his 1937 publication considered that the finished product ‘leaves little or nothing to be desired’. The design of the Foley catheter (left) has not fundamentally changed and today, with up to 25% of patients in hospital, 23% in chronic care and 4% in community care undergoing catheterisation, millions are used worldwide.

Growing health hazard
Unfortunately, long-term catheterisation (LTC) of the bladder with Foley’s design is associated with high morbidity from catheter-associated urinary tract infections (CAUTI) and, as such, international guidelines recommend that the practice is only considered as a last resort. Urinary tract infections account for more than 30% of all healthcareassociated infections and of these, about 70% are related to the use of the catheter. CAUTI places heavy demands on healthcare resources, and subsequent treatment with antibiotics raises serious concerns regarding the development of antibiotic resistance.

As a conduit, the catheter enables bacteria to enter the bladder following drainage, which it rapidly colonises at a rate of about 3–8% a day. After just one month, virtually all patients will be passing bacteria in the urine, a condition termed bacteriuria. Suprapubic catheterisation provides an alternative route for bladder drainage. By possessing a lower microbial population than the perineum, suprapubic insertion can delay the onset of bacteriuria – a route that many patients find more comfortable and easier to manage.

Bacterial infection has long been recognised as the cause of the high morbidity of long-term catheterisation, with multiple reports over many years. In 1958, Beeson warned that the catheter was capable of producing a serious disease that was difficult to treat. Infection with urease-producing bacteria such as Proteus mirabilis is a major cause for catheter blockage and urine bypassing around the catheter. Urease hydrolyses urea in the urine to form ammonium salts, causing urinary pH to rise, and resulting in the formation of crystalline deposits of struvite and hydroxyapatite within the lumen of the catheter, which obstruct the flow of urine.

Studies have shown that up to 50% of patients managed by LTC experience recurrent blockages that arise at unscheduled times at day or night, causing a heavy burden on community nursing services. For nearly 50 years, attempts have been made to reduce the incidence of CAUTI by coating the catheter with antiseptic or antimicrobial coatings, but this approach has produced no convincing benefits. Increasing criticism has been directed towards the design of the Foley catheter, which fails to drain the bladder completely and leaves a substantial volume of residual urine stagnating in the bladder. Furthermore, the tip of the catheter ulcerates and can even penetrate the cells lining the bladder, providing direct access for bacteria into the bladder wall.

Attention is currently focused on the design specifications for a new safe, reliable urine collection system that will alleviate the misery of LTC for disabled and older patients and their carers.

Such a system should:

  • be securely retained to drain the bladder without injury to the urothelial lining
  • allow the bladder to fill and empty completely include an automatic or remote mechanism for intermittent drainage of the bladder

In an ageing population, loss of bladder control is a common, distressing condition and its management is not only fundamental to their care, but should be used to fully appraise the standard of that care. In those over 65, urinary incontinence affects up to 20% of women and 10% of men living at home and becomes a reason for many to seek residential care. Once admitted to long-stay care, the prevalence rises sharply. Despite its morbidity, LTC is used for the most disabled, debilitated and vulnerable with intractable urinary incontinence, particularly those with neurological conditions and those unfit for surgery.

What can be done?
Formidable obstacles face anyone who attempts to raise interest in new device developments in a clinical field, especially those demanding an interdisciplinary approach where profound questions are raised as to how compassion can be introduced to patient care. The conservative management of bladder dysfunction is invariably delegated to nursing staff, but while the majority are committed to providing care, few have any experience of R&D or interdisciplinary collaboration. If commercial interest is to be maintained, the introduction of innovative designs immediately raises the need for protection of the intellectual property, which can become an expensive exercise. Clinical equipment requires patient involvement and, therefore, protection has to be obtained before a design can be made public. Furthermore, applications for Research Council funding are time-consuming to prepare and finally considered in responsive mode by committees for their scientific contribution in a highly competitive market.

While the subject presents a huge challenge in clinical management, it is attracting insufficient interest among senior clinicians, academics and industrial officers. With the industry producing millions of cheap catheters each year and the ancillary equipment raising a considerable market, there are few incentives to spend money to improve patient care. In this environment, academia can envisage no prestige behind the efforts of the sector. Who will step up to the plate and take on this challenge?