URINARY RETENTION

URINARY RETENTION

By Dr Clarence Lei Chang Moh, FRCS Urol, FEBU

Consultant Urologist

Adjunct Professor, Universiti Malaysia Sarawak

URINARY RETENTION can be defined as inability to empty urine from the bladder:

It may be acute (usually painful) or chronic (usually painless). This must be differentiated from oliguria or anuria when the patient does not pass urine because there is no urine in the bladder.  The 10 year cumulative risk  of a 60 year old male having acute urinary retention is 13.7% [J Urol 2001; 58 (S6A).5]. This is almost double the risk of stroke and triple the risk of hip fracture or myocardial infarction. 

Normal voiding involves the anatomical structures of the urinary bladder detrusor muscle, urethra (prostatic, posterior and penile) and sphincter mechanisms (proximal at bladder neck and DSM, distal sphincter mechanism). The anatomical structures only work in proper coordination if the nerves concerned, namely, the parasympathetic cholinergic nerves for bladder contraction is in synergistic relaxation of the external sphincters, usually function of the sympathetic adrenergic system.  The penis itself consists of two main cylinders (“twin towers”, the corpora cavernosa). The urethra runs through the corpus spongiosum on the ventral aspect of the penis. The peripheral nerves are coordinated in the sacral canal centres S2, 3, 4, sending messages to the centres in the brain stem and brain. 

CAUSES OF URINARY RETENTION:

Accordingly, the causes of urinary retention may be related to bladder outlet obstruction especially by the prostate in men above the age of 50.  Other common causes include post traumatic urethral strictures and occasionally by an impacted urethral stone.  It is often not appreciated that an important cause of urinary retention is that of an underactive detrusor bladder, UAB muscle, the commonest underlying aetiologies being that of aging and diabetes mellitus.  When the nerve supply to the voiding mechanism is disrupted, e.g. in spinal cord injury or in central nervous system disorders (in particular, Parkinsonism), voiding difficulty is a common part of the neurological symptoms.  Voiding disorder can also occur in the absence of neurological disease and there is just a detrusor sphincter dyssynergia, DSD, sometimes precipitated by pain, stress or constipation.

CLINICAL ASSESSMENT:

A history of the above aetiological factors is obviously important. A patient should also be examined, especially as to whether the palpable bladder is tender.  The penis should be examined for phimosis, urethral scarring or urethral stones. Rectal examination is essential to assess the anal tone, prostatic abnormalities, other tumours and constipation.  The lower limb neurology is also assessed.

INVESTIGATIONS OF URINARY RETENTION:

The aetiology of the urinary retention can often be ascertained from the clinical assessment. Complicated pelvic fracture not only causes injury to the urethra but also to the vascular and nerve supply to the voiding mechanism and the penis. Nevertheless, investigations are important to confirm the diagnosis as well as to formulate a plan of management.  Investigations can consist of the following:

(1)       Urinalysis and urine culture.

(2)       Ultrasound of the bladder, prostate and kidneys. In particular, one should look for bladder stones, intraprostatic protrusion of the prostate and prostatic size. If there is bilateral hydronephrosis, this should be noted.

(3)       KUB x-ray to look for urinary stones, constipation, any other bony abnormalities including osteosclerosis from any cancer of the prostate.

(4)       Baseline blood tests including blood glucose, renal function test and a PSA, prostatic specific antigen.

(5)       If there has been a history of any  difficulty of catheterisation, a useful investigation is that of injecting radiocontrast retrograde up the urethra (i.e. a retrograde urethrogram), to confirm the site and extent of the urethral stricture. 

URETHRAL CATHETERISATION:

This is the urgent treatment of urinary retention, especially if it is painful.  The indication for urethral catheterisation should be explained properly to the patient and consent obtained.  The urethra can be anaesthetised with an instillation of 5 to 10 cc of pure Lignocaine gel for a few minutes. An appropriate size catheter (usually 16 Fr Foley’s balloon catheter) can be gently inserted, in the absence of a urethral stricture. Aseptic technique should be practised so as not to introduce infection into the urinary tract.  The foreskin should also be properly replaced after the catheterisation to reduce the risk of paraphimosis causing ischaemia to the glans penis.  The urethral balloon should only be inflated when it is possible to pass the catheter easily into the bladder (all the way) and draining clear urine. 10 mls of Normal Saline or water is sufficient to inflate the Foley’s balloon catheter.  Any use of force in the urethral catheterisation can cause damage to the urethra especially the bulbous and prostatic urethra. Inflating the balloon while the catheter is still in the urethra will add further rupture to the urethra.  The urethra being a tubular organ also heal by fibrosis, causing a stricture.  Other damage by subsequent instrumentation will cause more scarring. Hence, “once a stricture, always a stricture”. 

Urethral catheter should only be inserted on proper indication: usually to relieve  urinary retention or to monitor the urine output in an intensive care situation. If the bladder is not obviously palpable, an ultrasound or bladder scan is an important part of the assessment before catheterisation. Once the catheter is no longer needed, it should be removed; it should be  changed every 2 weeks to reduce the risk of CAUTI, catheter associated urinary tract infection.  If there is a risk of urethral injury (e.g. in post trauma patients), the catheter should be left insitu for at least a week to allow any trauma to heal.  If there is a possibility of a bladder injury, the urethral catheter is usually left insitu for 10 days.

WHAT IF THERE IS DIFFICULTY IN CATHETERISATION?

If a urologist is available, he will often give another attempt gently at the urethral catheterisation, probably using more Lignocaine gel and cooperation with the patient.  An alternative is to pass a glide wire. If the glide wire can enter the bladder with ease, this can be followed with urethral dilatation in a gentle fashion (using the Seldinger technique). A Foley’s can then be passed over the guidewire.

WHAT ABOUT SPC, SUPRAPUBIC CATHETER?

If one fails to insert a urethral catheter and the patient has an obviously distended bladder, the next step is usually insertion of a suprapubic catheter percutaneously. The bladder must be obviously palpable; in obese patients, ultrasound guided puncture is necessary. The site of insertion is in the midline and about 3 cm from the symphysis pubis.  After aspirating urine from the bladder with a 21G needle, the area is then infiltrated with 2% Lignocaine (usually about 5 cc).  After a stab incision, the suprapubic catheter can then be inserted in a gentle controlled manner. There are 2 types of SPCs commonly used in Malaysia, namely, the Cytofix or the Bard SPC.  The Cytofix is a small 10 to 12 Fr catheter for emergency drainage, usually for a few weeks only. It has to be anchored safely, usually with Silk sutures. As the catheter is small, the tract is also too small to be used for subsequent drainage. A Bard SPC is a 16 Fr balloon catheter and therefore, technically more difficult and risky to insert, usually done by a specialist. When the catheter is inserted, the Foley’s balloon is filled with 5 cc of Normal Saline and anchored by pulling the bladder against the abdominal wall with a Silk suture.  After 2 weeks, the tract will be well formed and the catheter can be easily changed.

WHAT ABOUT 3-WAY CATHETERS?

For patients who have haematuria, a 3-way catheter may be inserted such that Normal Saline can be infused to irrigate the bladder to prevent the formation of clots until the bleeding stops.  3-way catheters are usually larger, usually 22 Fr.  A common problem faced by junior doctors in the surgical ward is that of post prostatic surgery (commonly a TURP, transurethral resection of the prostate) haematuria and clot retention.  As there is a fresh surgical prostatic cavity, it is best that such catheters be changed by a urologist who often use a urethral catheter introducer as well. To wash out debris and blood clots from the bladder, a bladder syringe with a wide nozzle can be used. 

WHAT ABOUT CHRONIC RETENTION?

Chronic retention is often painless and may not require urgent catheterisation.  However, if there is back pressure, there is associated bilateral hydronephrosis, a condition known as HPCR, high pressure chronic retention.  If the patient is not catheterised, he will go into progressive obstructive uropathy although this condition occurs in less than 1% of patients with BPH, benign prostatic hyperplasia. However, if a catheter is introduced, they often go into post obstructive diuresis. Such patients with HPCR should ideally be admitted for intravenous fluid replacement and monitoring of the blood pressure and heart rate.  Other indications for admission include haematuria and fever.

For other patients with chronic retention, the optimal treatment is to do CISC (clean intermittent self catheterisation) or CIC (clean intermittent catheterisation). CIC is performed when the patient himself or the child is unable to self-catheter.  This is a clean technique done by the patient or the carer. There are special single channel reusable catheters for the purpose of CISC or CIC. CIC or CISC is done when the bladder capacity is optimal, usually 3 to 4 times a day. This is considered one of the biggest breakthroughs in urology, especially to preserve the bladder and kidney function. 

By Dr Clarence Lei Chang Moh, FRCS Urol, FEBU

clarencelei@gmail.com

6^th July 2017.