Retention of urine is the inability to pass urine voluntarily when the bladder is not empty. It is classified as acute or chronic retention of urine and the difference is important both in terms of presentation and management.

As the bladder enlarges the tension in the walls required to empty it rises in keeping with La Place’s law so that if the bladder becomes over-distended it is difficult or impossible to empty it naturally. The risk is greatest when production of urine is high at a time when sensation is impaired. Examples include anaesthesia, when left ventricular failure is treated with a potent diuretic and morphine or diamorphine, or after drinking a large amount of alcohol, especially beer as the volume is very high.

Epidemiology: There were 32,162 hospital consultant episodes for retention of urine in England in the year 2002-03. This represents 0.25% of all episodes. 83% required admission to hospital with a mean length of stay of 5.3 days, median 5 days. 7% were single day episodes. 86% of patients were men and 14% women. The mean age of those admitted was 69 but 18% were aged 15 to 59 whilst 48% were over 75.

Risk factors: The epidemiology shows a typical patient as an elderly man. This is commensurate with the commonest contributing factor being prostatic disease but there may be a number of features working together. Diuresis, impaired sensation, drugs and confinement to bed may all be involved. Risks are usually multifactorial and can be predicted. For example, men with a high IPPS score are more likely to have acute retention after orthopaedic surgery.

•Benign prostatic hyperplasia or carcinoma of prostate
• Neurological disease including stroke or multiple sclerosis. It has been reported with sacral shingles and it may occur as a feature of cauda equina compression as described in sinister causes of back pain
•Drugs, especially anticholinergic drugs like tricyclic antidepressants but potent analgaesics or anaesthesia may allow the bladder to become distended by impairing sensation. Antihistamines and illicit drugs like ecstacy (MDMA) may also be involved
•Pressure or anatomical distortion, usually from faecal impaction or utero-vaginal prolapse. Pelvic tumors, benign or malignant, may be responsible. A retroverted, incarcerated uterus is a rare but well known cause. It has been suggested that the association with faecal impaction is not causative but both are associated with immobility
•It can occur during labor due to physical pressure or possibly neural block with an epidural. A full bladder may obstruct labor and can be damaged by instrumental delivery
•Urinary tract obstruction may affect the outflow and can include strictures of the urethra, bladder cancer, stones and clot
•Alcohol can lead to acute retention by producing a diuresis and also impairing sensation so that the bladder becomes over-distended
•Traumatic rupture of the urethra
•Severe pain in the rectum

History: With both acute and chronic retention there may be a history of difficulty passing urine but this is not invariable. Acute retention is rapid in onset over a matter of hours whilst chronic retention has a much more protracted course. The most important point in differentiation is that acute retention of urine is very painful whilst chronic retention of urine is painless. In the former the patient complains of inability to pass urine and is very uncomfortable.

Acute retention may present at a time of high risk as after an operation or after admission for myocardial infarction or stroke. It can be also present in the community, usually as a culmination of increasing difficulty with micturition. Note drugs.

The patient with chronic retention may be passing some urine. There is often retention with overflow so that the complaint is one of urinary frequency rather than inability to void. Small volumes are passed often. Painful bladder is not a complaint. It needs to be differentiated from polyuria or the complaint may be of nocturia although there will be frequency by day too.

Examination: The bladder may be visible and should be palpable, often up to the umbilicus in acute retention but in chronic retention it can be even higher. Examination of the abdomen will show a mass arising from the pelvis. It is impossible to get below it. Palpation can be difficult in the obese or in pregnancy. Percussion may show dullness to distinguish it from bowel. A large bladder should be part of the differential diagnosis of abdominal masses and abdominal distension.

In acute retention the bladder is tender. In chronic retention it is not painful.

Differential diagnosis: Even if the patient is passing urine, if there is a large, palpable bladder there is retention of urine. If the bladder is large, palpable and tender whilst the patient complains of pain with an urge to void that cannot be fulfilled, the diagnosis is clear. If there is a mass that is not painful it may be a bladder in chronic retention but other considerations include a large uterus from fibroids, pregnancy, ovarian cysts or ovarian carcinoma. It is also imperative to ascertain that failure to pass urine is not due to failure to produce urine as in acute renal failure.

Management: The essential feature of management is passing a catheter to let down the bladder. The technique is described in the relevant article. A urethral catheter should pass easily. If it does not, then seek help from one with appropriate expertise. Introducers should be used only by those who are trained to use them. A suprapubic catheter may be required. Ascertain that there is free flow or urine before inflating the balloon.

In acute retention the catheter can be left to drain freely, producing a very grateful patient. In chronic retention there is dilatation of blood vessels that can bleed profusely if deflation is too fast. In chronic retention the bladder must be drained slowly. Authorities differ as to the exact speed but the larger the bladder the slower it must be drained.

There is considerable difference of opinion, and not a great deal of evidence, with regard to how long to leave a catheter in situ acute retention. Some people recommend simple drainage and removal of the catheter whilst others suggest that 24 to 49 hours of drainage allows the bladder to regain its tone. Probably each case needs to be considered on its merits. In postoperative retention it is often safe to drain the bladder and remove the catheter immediately. Sometimes mild bleeding occurs as acute retention is relieved but it rarely causes problems. Other reports after drainage include a reflex diuresis and hypotension but neither tends to be severe.

If a catheter is removed in the late afternoon the patient may fail to pass urine and it needs to be replaced late at night. Therefore it is more usual to remove it in the early morning. There is evidence that removal at midnight, in a hospital setting, gives the best results. The bladder may fill normally overnight and the patient should void normally in the morning.

Investigation: After relief of retention of urine it is important to ascertain the reason why it occurred.

•It is rare in children and if it occurs a neurological condition should be sought
•In men the prostate needs investigation. Treatment may be required to prevent recurrence.

Acute retention of urine is the presenting feature in 50% of men with benign prostatic hyperplasia. A high level of PSA is a good predictor of bladder outlet obstruction whilst a low level is reassuring.

•If drugs increase the risk then consideration should be given to an alternative.
•In neurological disease medication may be helpful to reduce the risk of recurrence. Emptying the bladder by the clock instead of waiting of sensation may prevent over-distention. An indwelling catheter is a last resort.
•Especially if there has been chronic retention it is important to assess renal function. A high pressure in the bladder can cause hydronephrosis and damage the kidneys.

Prevention: In the elderly, especially male population routine enquiry into problems of micturition may be regarded as a normal feature of aging, can permit treatment of the underlying cause before retention of urine occurs.

At high risk times like after operations or on a coronary care unit, encouragement of the patient to pass urine may prevent over-distension and retention. Urine charts and awareness of failure to pass urine are essential. Try to avoid drugs like tricyclic antidepressants in elderly men.

Retention of urine is the inability to pass urine voluntarily when the bladder is full. It can come on abruptly (Acute Retention) or can develop slowly over months (Chronic Retention). This is different and distinct from when the kidneys fail to produce urine, (kidney failure). In retention, the urinary bladder is distended with urine, but the passage from the bladder, (the urethra) is blocked either from within (as in the case of urethral stricture), or from without (as in the case of an enlargement of the prostate gland).

The difference between the two is important both in terms of presentation and management.

As the bladder distends to accommodate the urine from both kidneys, pressure in the bladder required to empty it rises so that if the bladder becomes over distended it is difficult or impossible to empty the bladder completely. The risk is greatest when production of urine is high at a time when sensation is impaired. Examples include when patients are under anesthesia and at the same time when the left side of the heart goes into failure. At times treatment includes diuretic (mediation that makes you pass more urine) and therefore increases your urine out-put. Again, after drinking a large quantity of alcohol, especially beer, urine output is increased.

Risk factors: Studies all over the years show a typical patient as an elderly man (over 50 years). This is commensurate with the commonest contributing factor being prostatic disease, but there may be a number of features working together. Diuresis (excessive production of urine by the kidneys), impaired sensation of bladder fullness, certain drugs for high blood pressure and some heart diseases, and confinement to bed may all be involved. Risks are usually multifactorial and can be predicted. For example, men are more likely to have acute retention of urine after orthopedic surgery.

 Benign Prostate hyperplasia or carcinoma of the prostate
 Neurological disease including stroke or multiple sclerosis. It has been reported with sacral shingles and it may occur as a feature of cauda equine compression described in sinister causes of back pain.
 Drugs, especially anticholinergic drugs like tricyclic antidepressants but potent analgesics or anesthesia may allow the bladder to become distended impairing sensation. Antihistamines and illicit drugs like ectacy may also be involved.
 Pressure or anatomical distortion, usually from faecal impaction or utero-vaginal prolapse. Pelvic tumors, benign or malignant, may be responsible. A retroverted, incarcerated uterus is a rare but well known cause. It has been suggested that the association with faecal impaction is not causative but both are associated with immobility.
 It can occur during labor due to physical pressure or possibly neural block with an epidural. A full bladder may obstruct labor and can be damaged by instrumental delivery.
 Urinary tract obstruction may affect the outflow and can include strictures or the urethra, bladder cancer, stones and clot.
 Alcohol can lead to acute retention by producing a dieresis and also impairing sensation so that the bladder becomes over-distended.
 Traumatic rupture of the urethra like happens in a fall from the palm or coconut tree
 Severe pain in the rectum

History
With both acute and chronic retention there may be a history of difficulty passing urine but this is not invariable. Acute retention is of rapid in onset over a matter of hours whilst chronic retention has a much more protracted course. The most important differentiation is that acute retention of urine is very painful whilst chronic retention of urine is painless. In the former the patient complains of inability to pass urine and is very uncomfortable. Acute retention may present at a time of high risk as after an operation or after admission for myocardial infarction (heart attack) or stroke. It can also present in the community, usually as a culmination of increasing difficulty with micturation.

The patient with chronic retention may be passing some urine. There is often retention with overflow so that the complaint is one of urinary frequency rather than inability to void. Small volumes are passed often. Painful bladder is not a complaint. It needs to be differentiated from Polyuria or the complaint may be nocturia (frequent urination at night) although there could be frequency of urination also during the day.

Examination
The bladder may be visible and should be palpable, often up to the umbilicus in acute retention but in chronic retention it can even be higher. Examination of the abdomen will show a mass arising from the pelvis. It is impossible to get below it. Palpation can be difficult in the obese or in pregnancy. Percussion may show dullness to distinguish it from bowel. A large bladder should be part of the differential diagnosis of abdominal masses and abdominal distention.

In acute retention the bladder is tender. In chronic retention it is not tender to the touc

Differential Diagnosis
Even if the patient is passing urine, if there is a large, palpable bladder there is retention of urine. If the bladder is large, palpable and tender whilst the patient complains of pain with an urge to void (urinate) that cannot be fulfilled, the diagnosis is clear. If there is a mass that is not painful it may be a bladder in chronic retention but other considerate include a large uterus from fibroids, pregnancy, ovarian cysts or ovarian carcinoma. It is also imperative to ascertain that failure to pass urine is not due to failure to produce urine as in acute renal failure.

Management
The essential feature of management is passing a catheter to empty the bladder. A urethral Foley catheter should pass easily. If it does not, then seek help from one with appropriate expertise. A catheter introducer can guide the catheter into the urinary bladder by those who are trained to use it. A suprapubic catheter may be required. Ascertain that there is free flow of urine before inflating the balloon of the catheter.

Copyright Liberian Observer
By:
Dr. Lily Sanvee
http://www.liberianobserver.com