Urinary catheters: history, current status, adverse events and research agenda

Abstract

For more than 3500 years, urinary catheters have been used to drain the bladder when it fails to empty. For people with impaired bladder function and for whom the method is feasible, clean intermittent self-catheterization is the optimal procedure. For those who require an indwelling catheter, whether short- or long-term, the self-retaining Foley catheter is invariably used, as it has been since its introduction nearly 80 years ago, despite the fact that this catheter can cause bacterial colonization, recurrent and chronic infections, bladder stones and septicaemia, damage to the kidneys, the bladder and the urethra, and contribute to the development of antibiotic resistance. In terms of medical, social and economic resources, the burden of urinary retention and incontinence, aggravated by the use of the Foley catheter, is huge. In the UK, the harm resulting from the use of the Foley catheter costs the National Health Service between £1.0-2.5 billion and accounts for ∼2100 deaths per year. Therefore, there is an urgent need for the development of an alternative indwelling catheter system. The research agenda is for the new catheter to be easy and safe to insert, either urethrally or suprapubically, to be retained reliably in the bladder and to be withdrawn easily and safely when necessary, to mimic natural physiology by filling at low pressure and emptying completely without damage to the bladder, and to have control mechanisms appropriate for all users.

Keywords: Urinary catheters; adverse events; biomaterials; infection; research agenda.

Figure 1.

Tubular silver catheters devised by Ambroise Paré (1510–1590), with long gentle curves (they are known as coudé catheters) to permit easier insertion [8].

Figure 2.

Urinary catheterization in the middle ages [17].

Figure 3.

The urinary tract.

Figure 4.

A typical Foley catheter. This catheter is size 16 Fr. Its overall length is ∼400 mm and the volume of the fully-inflated balloon is ∼10 ml. The catheter has two channels. When the catheter has been inserted, the retaining balloon is inflated with sterile water from a syringe via the inflation connector and one of the channels. The inflation connector incorporates a valve to prevent the sterile water from escaping when the syringe is detached. The other channel allows the free flow of urine from the drainage eye to the drainage funnel. To remove the catheter, the retaining balloon is first deflated by withdrawing the water from it with a syringe, which opens the valve in the inflation connector when it is attached.

Figure 5.

The Foley catheter, introduced (a) Urethrally and (b) Suprapubically. In both cases, the bladder is shown to be draining continuously into a urine collection bag attached to the leg: this bag can be emptied when necessary by opening a valve. Alternatively, the bladder can be drained intermittently if a catheter valve is inserted into the drainage funnel of the catheter.

Figure 6.

A section through a Foley catheter that has become blocked during use by the formation of struvite. The smaller patent lumen is the channel for the inflation and deflation of the retaining balloon. The length of the scale bar is 1 mm.

Figure 7.

A catheter incorporating some of the concepts in the research agenda. The catheter is retained by wings which spring open after insertion through the suprapubic tract to the bladder: this traps less urine than the balloon of a Foley catheter and the catheter can be withdrawn transurethrally after cutting through it at the external suprapubic port. Multiple drainage eyes in the section of the catheter within the bladder minimize the risk of the formation of pseudopolyps, and this risk is further reduced by a collapsible section (shown stippled) of the catheter situated close to the external meatus of the urethra. The elastic reservoir at the suprapubic end of the catheter and strapped to the abdominal wall expands to accommodate urine from the bladder during spasmodic bladder contraction and returns it to the bladder when it relaxes after the spasm, thus minimizing the possibility of kidney damage. Periodic drainage of the bladder into a leg bag is actuated by a pinch valve beyond the collapsible section of the catheter, under manual or timed automatic control.