VOL: 101, ISSUE: 18, PAGE NO: 61
Jane Gosling, MSc, RGN, is urology consultant nurse, Department of Urology, Derriford Hospital, Plymouth
Acute retention of urine is usually a painful condition; anyone experiencing it is likely to seek help quickly.
However, it can also be painless, and although people may be aware they have not passed urine, they may not realise that they actually have a full bladder. Patients with chronic urinary retention may not be aware there is a problem, or may attribute associated urinary symptoms such as frequency to the ageing process. Urinary retention with overflow occurs when the bladder is full and the patient passes small amounts of urine frequently (25-50ml) (Getliffe and Dolman, 2003).
Physiology of normal voiding
It is important to understand the anatomy and physiology of normal voiding in order to understand why urinary retention occurs (Figs 1 and 2). The bladder is able to distend and contract. When empty it collapses, its bladder wall measuring 5-8cm, and is thick and folded. As urine enters the bladder the detrusor muscle of the bladder wall stretches and thins as the cells in the mucosal lining (transitional cells) slide over one another. The wall of the bladder thus becomes thinner and its volume increases.
Painful acute urinary retention
Classically, acute urinary retention affects men with prostatic hypertrophy (enlarged prostate), and when obstruction occurs the patient will experience pain and may become agitated. Inserting a urinary catheter into the bladder will relieve the symptoms.
Causes of painful acute urinary retention
Constipation - An impacted sigmoid colon or rectum can exert pressure on the lower urinary tract to the extent that the bladder is unable to empty. The nurse or doctor will need to drain the urine from the bladder with a catheter, and once the patient is comfortable it is important to ask about bowel function and perform a rectal examination to check for faecal impaction.
If there is evidence of constipation, enemas and laxatives should be given and when the constipation is resolved the catheter can be removed. The patient should be given advice on diet and fluid intake and regular laxatives should be considered to prevent the problem recurring.
Bladder outflow obstruction - In men, an enlarged prostate can lead to bladder outflow obstruction, as the enlarged gland can occlude the urethra. The man may report problems with the flow of urine; symptoms include increased frequency, nocturia, hesitancy, urgency and a poor flow. Acute painful urinary retention can occur when a man with these problems has a large amount to drink or refrains from emptying his bladder for a longer period than usual. In this case the detrusor muscle becomes stretched, and it is the combination of poor detrusor muscle function and outflow obstruction that may lead to acute urinary retention.
Prescribing an alpha-blocker, such as alfuzosin or tamsulosin, with or without a 5 alpha-reductase inhibitor, such as finasteride, for two weeks before removing the catheter may be helpful in shrinking the size of the prostate gland in some men (McNeill et al, 1995).
However, if the patient had a large residual volume of urine in the bladder when he was catheterised, surgery to resect the prostate gland may be a preferred option.
Infection - Infection causes acute inflammation and oedema of the bladder mucosa. This ‘thickening’ can lead to urinary retention. This should resolve once the infection is treated with antibiotics.
Recent surgery or immobility - Anaesthetics paralyse the detrusor muscle and it may take some time for it to recover, especially if it has been overstretched as a result of any of the problems identified in Box 1. It is therefore important to monitor the urine output of all patients after they have had anaesthesia.
Urethral strictures - Urethral strictures can occur spontaneously or after trauma, surgery or infection. A patient with a stricture usually complains of an intermittent, poor stream of urine and may need to strain to push urine through the narrowed urethra. If the stricture becomes tighter, urinary retention may occur. In this situation it can be difficult, or even impossible, to pass a urethral catheter and a suprapubic catheter will need to be inserted.
A flexible cystoscope is used to confirm the presence of a stricture, but a rigid cystoscope is used by the surgeon to incise through the dense tissue of the stricture (optical urethrotomy). Following the incision, a urethral catheter is passed, which acts as a stent, keeping the new passage open.
The patient may go home with two catheters: the urethral catheter draining urine and the suprapubic catheter. About a week later, depending on the density of the stricture, the urethral catheter is removed. The suprapubic catheter remains in place in case the patient does not void via the urethra. It can be removed from the bladder when a good urethral flow of urine has been established.
Most patients who have experienced urinary retention because of a urethral stricture will need to learn self-dilatation using an intermittent catheter so as to prevent a recurrence.
Haematuria - There are many causes of haematuria (blood in urine), one of them being for bladder cancer. Blood clots in the bladder can inhibit the flow of urine, causing clot retention, and the patient may need to be catheterised with a three-way catheter. This allows the bladder to be irrigated continuously, thereby preventing an accumulation of blood and consequent clot formation.
Painless acute retention - Acute painless urinary retention is usually due to an underlying neurological condition. A catheter can relieve the retention, but an urgent neurological opinion should be sought if there is no known explanation for the condition.
This can be divided into two categories: high pressure chronic retention and low pressure chronic retention.
High-pressure chronic retention
High-pressure chronic retention can occur as a result of a long-term obstruction, for example, prostatic hypertrophy. The detrusor muscle will attempt to push more strongly in order to overcome the obstruction, which leads to thickening of the bladder wall.
The layers of the detrusor muscle are arranged in a fretwork pattern (rather like a string bag), and as the muscle over-exercises, bands of fibrous tissue form. These become coarser and thicker (trabeculae) and eventually the softer mucosal lining of the bladder is forced out between them forming a saccule. This then enlarges to form a diverticulum.
The detrusor eventually fails to overcome the original obstruction and the resistance of the new fibrous bands, causing high pressures in the bladder. This can occur suddenly, resulting in acute on chronic urinary retention or slowly lead to chronic retention.
When chronic retention occurs, patients may not be aware of their urinary problems, as the process happens over a long period of time. A deterioration in their urinary flow occurs gradually, and symptoms are often attributed to the ageing process or are not recognised at all. Some patients can retain volumes of a litre or more in their bladders without experiencing any pain. One of the first signs of a problem may be night-time frequency (nocturia) or incontinence at night (nocturnal enuresis). During sleep the urethral pressure is relaxed slightly and the high pressure in the bladder forces urine out (Weiss, 2001).
Other symptoms of high pressure chronic retention include:
- Recurrent infections, due to the stasis of urine in the bladder;
- Hesitancy (needing to wait for urination to start) as the bladder takes time to overcome the high pressure created by the obstruction;
- Poor flow of urine;
- Terminal dribbling.
Patients may also complain that they do not empty their bladders properly and need to return to the toilet frequently.
A diverticulum in the bladder can result in poor bladder emptying and the patient may have the urge to micturate shortly after passing urine. As the bladder empties, some urine, instead of exiting via the urethra, is pushed into the diverticulum. Once the bladder relaxes after urination, this urine empties back into the bladder, and 10 minutes or so after going to the toilet the patient has the urge to pass urine again.
Management of high-pressure chronic retention - High-pressure chronic retention needs to be treated to correct bothersome symptoms and reduce the long-term risk of kidney damage.
The high pressure within the bladder means the ureters are unable to empty and the kidneys become distended. Thickening of the bladder wall can occlude the end of one or both of the ureters, preventing drainage of urine from the kidneys. This in turn leads to distension of the kidney (hydronephrosis) and eventual kidney failure. An ultrasound scan of the kidneys may identify hydronephrosis, and blood tests, including those for urea and creatinine levels, will assist in the assessment of renal function.
Passing a urinary catheter into the bladder relieves the occlusion of the ureters, following which the flow of urine from the kidney is quickly re-established. However, a post-drainage diuresis (increase in urine produced by the kidneys) can occur when the obstruction is relieved. Excess water and sodium retained in the kidneys during the period of obstruction is then excreted. This is beneficial, but if the volumes are large patients may need intravenous fluids in order to maintain their fluid balance. Most patients need about 200ml of fluid an hour for the first 12 hours (Weiss, 2001). In the past, a method of slow decompression was used but there is no evidence to support this.
Following drainage of urine from the bladder, haematuria (blood in the urine) may occur. This is due to small vessels in the bladder bleeding as the pressure on the bladder wall is released, or it may be due to trauma caused by the catheter. If blood clots are present it is important to check that the catheter is draining and does not block.
Future management - Once an episode of chronic urinary retention has been resolved, the patient, doctor and nurse will need to decide on future management. One option may be to relieve the obstruction; for example, by performing a transurethral resection of the prostate.
Following prostate surgery the patient may not be able to void urine as the detrusor muscle has been overstretched and chronic retention of urine may develop slowly once the catheter is removed. Delaying removal of the catheter for two weeks can give the detrusor more time to recover, and pelvic floor exercises can help, but these will take time to be effective (Shah and Leach, 1998). Clean intermittent self-catheterisation is also an option.
If the patient does not want, or is not fit for surgery, either intermittent self-catheterisation or a permanent indwelling catheter are options. Nurses have a role to play both in helping their patients and their families make a choice and in teaching and supporting them to regain independence.
Low-pressure chronic retention
Low-pressure chronic retention is caused by primary failure of the detrusor muscle and is associated with conditions such as multiple sclerosis and stroke disease. Although the detrusor fails to squeeze in these conditions, it remains compliant in stretching to hold urine, and the pressure in the bladder remains low. Low-pressure chronic retention can sometimes be discovered during the course of an examination for another complaint, as many patients with the condition have few bothersome symptoms. However, some patients may complain of having to pass urine frequently because their bladder never completely empties. Patients may also suffer from recurrent urinary tract infections owing to stasis of urine in the bladder.
As the pressure in the bladder remains low, there is no back pressure that can result in kidney damage. An ultrasound scan can exclude hydronephrosis, and a blood test for urea and creatinine can be used to check renal function.
Management of low-pressure chronic retention - If a patient has no symptoms and the ultrasound scan and blood test are normal, there is no need to do anything except monitor the situation. But if the patient complains of frequency or nocturia, or is having recurrent urinary infections, intermittent self-catheterisation is an option.
Most patients are daunted by the thought of having to self-catheterise, therefore nurses play a vital part in patients’ care in the following ways:
- Assessing patients both physically and psychologically to ensure they will cope;
- Explaining the technique;
- Supervising their first attempts.
Urinary retention can occur for several reasons, and is present in different ways. Patients and their families will appreciate the support of anyone who is able to help them to resolve this problem.