Reducing the Neonatal risk of knotting in fine bore drainage tubes.

Catheterisation of neonates and babies is common and due to the size of the urethra feeding tubes (sizes 4ch to 6ch) are often used which can lead to potential complications such as spontaneous knotting of the tube within the bladder. Although uncommon, 0.2 cases per 100,000¹ catheterisations reported, it is important to understand the factors which are believed to contribute to the risk of knotting and ensure steps are taken to minimize this happening.

Babies born with disorders such as myelomeningocele or other congenital cord lesions such as sacral agenesis will often present with a neuropathic bladder. Pre 1950’s babies born with such disorders often died until shunting devices were developed but it wasn’t until the 1960s and 1970s that the ‘neuropathic bladder’ was identified as a complication of these disorders and surgery such as a vesicostomy, ileal conduit or ureterostomy were performed to protect the upper tracts and kidneys. Renal impairment had been reported within 6 months of age and as prevention of renal damage is a priority management of the neuropathic bladder must start at birth with an aim to replicate, where possible, normal bladder function. Clean intermittent catheterisation combined with an anticholinergic has been identified as an effective initial form of management, however, this may lead to potentially more cases of spontaneous knotting from ‘catheterising’ being reported if people are not aware of the complication.

The first reported case of knotting following transurethral catheterisation was reported in 1976² with further cases being reported, more commonly in neonates and children and mostly boys with almost all cases reporting the use of a feeding tube having been used.

Feeding tubes are often used as are they are available in smaller sizes than catheters with 4Fr/Ch and 6Fr/Ch being commonly used. However, feeding tubes tend to be much longer than catheters with lengths of up to 125cm, encouraging clinicians to insert more tubing than necessary into the bladder.

Feeding tubes and catheters sizes 6Fr/Ch and under are very fine and flexible, when excessive tubing has been introduced into the bladder it can form a loop, then as the bladder decompresses, the tubing can become knotted or entangled. When it comes to removal of the tubing, the loop/knot may tighten as it meets resistance on withdrawal making removal of the catheter urethrally traumatic or impossible requiring surgical intervention.

Most reported cases felt the risk of knotting could be avoided or prevented with a better understanding of the urethral anatomy in neonates and young children and selecting a more suitable catheter.^3,4,5

A new-born male urethra measures approximately 5cm and increases to about 8cm by the age of 3. The female urethra is much shorter and has a slower development time measuring approximately 2.18cm at birth, increasing to around 2.54cm by the age of 5. It is therefore recommended that no more than 6cm of length should be inserted into a male new-born and 5cm in a female and in babies with very low birth weight <750 grams, <5cm should be inserted in boys and <2.5cm in girls.³

In addition, clinicians should be encouraged to pass a catheter until urine starts to flow and then introduce the catheter approximately another centimetre to ensure the catheter is positioned in the bladder without excess.

Where possible the catheter should be passed, the urine allowed to drain and the catheter removed, however, there are incidences when the bladder may need to be on continuous drainage. When left in situ it is important to secure the catheter effectively to prevent inadvertent advancement of the catheter into the bladder.⁴

Wymedical have launched a size 5Fr/Ch catheter, at the request of a Paediatric nurse, which is 25cm in length to try to overcome the temptation of introducing an excessive length of tubing into the bladder and therefore reduce the risk of knotting and licensed for purpose. The Wycath uncoated catheter, WUP05, is DEHP free and is available on prescription enabling parents of new-born babies to be able to undertake intermittent catheterisation from birth and reduce the risk of damage to the upper tracts. The families can be discharged from hospital and managed at home under a close eye of a urology team until further surgery is required.

References

1.       Foster H, Ritchey M. Bloom D. Adventitious knots in urethral catheters: report of 5 cases. J Urol 1992; 48 1496-8

2.       Harris VJ, Ramilo J. Guide wire manipulation of knot in catheter used for cysto-urethrography. JUrol 1976; 116 529

3.       Carlson D, Mowery B. Standards to prevent complications of urinary catheterisation in children: should and should knots. J Soc Pediatric NUrs 1997; 2:37-41

4.       Arena B, McGillivary D, Dougherty G. Urethral catheter knotting: be aware and minimise risk. Canadian Journal of Emergency Medicine 2002; 4(2): 108-110

5.       Sarin YK.Spontaneous intravesical knotting of urethral catheter. APSP J Case Rep 2011; 2:21