Author: Andrew Parfitt, Peter Jaye / Editor: Andrew Parfitt, Peter Jaye / Reviewer: Jason Kendall, Amanda King / Codes: C3AP9, ACCS LO 2, SLO1, UP3 / Published: 13/07/2022
This session covers the common presentations of urinary retention and its management in the emergency department. It also covers the common problems that can occur in patients who have in-dwelling catheters.
Acute urinary retention (AUR) is a common emergency presentation, and has an incidence of 3/1000 patients each year(3). In 32,162 hospital episodes of AUR, 86% were in men and only 14% in females(3). The acute management is essentially similar between the sexes. 10% of men will have an episode of acute urinary retention between the ages of 70 and 75 years(3).
Debate continues regarding which of the three options of emergency admission and prostatectomy, discharge and elective prostatectomy or trial without catheter (TWOC) are the most effective(14).
Chronic urinary retention is painless retention, associated with an increased volume of residual urine.
Patients with urinary retention can present with complete lack of voiding, incomplete emptying, or overflow. Complications include infection and renal failure.
There are four mechanisms of AUR(5).
- Increased resistance to flow: this may be at the bladder neck smooth muscle, which results in a dynamic outflow obstruction or a mechanical obstruction such as urethral stricture or prostatic enlargement
- Inappropriate detrusor muscle innervation resulting from neurological causes such as stroke, spinal cord lesions or diabetic neuropathy
- Bladder over-distension such as occurs with postoperative pain and alcohol; inability to void leads to bladder distension
- Drugs: anti-muscarinic and alpha adrenergic medications
The prostate is rich in adrenergic receptors. In AUR, the maximal pressure rise is in the prostatic urethra, the bladder neck is not tightly closed and the tone of the external sphincter is inhibited. 5a Reductase drugs such as finasteride decrease symptoms of benign prostatic hypertrophy (BPH) and thus the incidence of AUR when taken long term(12). However, significant side effects such as impotence and decreased libido may occur.
There are many causes of urinary retention. These do not need to be learnt by rote, but what is important is to always consider neurological causes.
Acute urinary retention aetiology
- Urethral stricture
- Acute prostatic haematoma
- Prostate cancer
- Bladder neck contracture
- Urethral stone
- Foreign body
- Iatrogenic e.g. urinary stent occlusion
- Neurogenic: neurogenic bladder
- Neurological disease: MS, Parkinsons, DESD, Detrusor-external sphincter dyssynergia, Tabes Dorsalis, Alzheimers
- Spinal cord injury including Cauda Equina Syndrome
- Abdominoperineal resection
- Spinal anaesthesia
- Lower tract instrumentation
- Traumatic pain
- Alcohol toxicity
- Acute prostatitis, E.coli, proteus
Drugs that cause AUR
- Decongestants: phenylephrine, pseudoephedrine
- Antihistamines: diphenhydramine, phenergan
- Beta agonists: atropine, isoprenaline, isoproterenol
- Tricyclic antidepressants
Female specific causes
- Organ prolapse
- Pelvic mass
- Gravid uterus
- Herpes simplex
A detailed history will point to a likely cause for the AUR. Most commonly, this will be the progression of benign prostatic hypertrophy (BPH). Careful enquiry may elucidate a history of gradual deterioration of lower urinary symptoms such as urge, hesitancy, frequency and post micturition dribbling.
A full drug history must be taken including recreational drugs.
Constipation, UTI and excess alcohol can precipitate AUR and should be specifically screened for. It is especially important to treat such precipitants. A detailed enquiry of associated urinary symptoms is essential, especially haematuria, which, if present, will influence further investigation and management.
Neurological symptoms must be screened for by direct questioning. This is particularly important in women.
Direct enquiry should also be made for urogenital conditions such as herpes that can cause AUR through discomfort.
Urinary tract sepsis and constipation should be treated before attempting trial without catheter.
Examination of a Patient with Retention
A distended bladder arises from the pelvis and one is unable to get below it unlike other abdominal masses. It is usually midline fixed and dull to percussion. Huge bladders may rise above the umbilicus although this is unusual. A careful inspection of the external genitalia for phimosis, trauma blood or vesicles.
Digital rectal examination (DRE) is of great importance not only to assess the prostate, but also anal sphincter tone. It should be performed after catheterisation with patient consent and with a chaperone present. The size, consistency and contour of the prostate gland should be documented.
Do not forget to examine and document perianal sensation and tone to exclude cauda equina syndrome.
Bladder scanning is increasingly available not only in the emergency department, but also on medical wards. These scanners allow staff to follow simple instructions, and an algorithm calculates bladder volume. Increasingly ultrasound (US) is a prerequisite in the placement of a catheter and decreases the dangers inherent in catheterisation where the diagnosis of retention is in doubt.
Any impairment of renal function must be sought by measuring urea and electrolytes (U and E) and creatinine.
A full blood count (FBC) should be obtained as a screening test and a urine sample should also be sent for microscopy.
An ultrasound scan (US) of the renal tract should be considered if any renal impairment is present. Prostate specific antigen (PSA) measurement can be falsely elevated after DRE or urethral catheterisation and should be taken prior to either of these interventions. It may not affect acute management, but can be useful if immediate referral for a urological assessment is required.
PSA in this setting gives a high false positive rate and should be deferred by 2 weeks(20).
Urethral catheterisation is the usual method employed in the UK(6). Suprapubic catheterisation (SPC) is usually reserved for when this fails. Suprapubic catheterisation is possible using several techniques(6). US guidance is an extremely useful adjunct to utilising either Bonanno catheters or the more conventional balloon catheter.
Unguided SPCs are contraindicated when there is a past history of bladder cancer, a history of haematuria or a suspicion of clot retention. These are the red flags of bladder cancer and one would wish to avoid seeding and spreading along the track that is used to insert the catheter.
Its important to document post catheterisation residual volume (RV), features of prostate examination, renal function, catheter type and gauge (14 or 16 French gauge) and ease of introduction in the case notes, as they assist in determining further management. Consent should be recorded in the notes.
Post obstructive diuresis can be a problem after relief of retention. Most commonly accepted definitions are a urine output of greater than 200mL/hr for two consecutive hours or greater than three litres over a 24-hour period. Some patients can pass as much as 8-20 L/day. Cardiac failure or renal insufficiency patients, especially if they have marked peripheral oedema, are at high risk. Severe dehydration and postural hypotension can occur. Hourly urine outputs must be recorded and should be less than 200 ml/h as a general rule. High risk patients for this condition are often found to have a RV>1000 ml and impaired renal function. Careful fluid balance assessment, electrolyte monitoring and judicious fluid replacement (preferentially via oral route) is used to manage post obstruction diuresis, which should settle within 24-48 hours.
Up to 70% of men will have recurrent retention within one week if the bladder is simply drained(18).
AUR secondary to constipation, UTI with no previous urinary tract symptoms and postoperative pain does not need follow up. Trial without catheter (TWOC) may be attempted.
Although the role of early TWOC is debated, in these conditions it may be feasible with a residual volume of less than one litre(8). Referral to a urology clinic with a catheter in situ is advised for most patients.
BPH features may be an indication to prescribe alpha blockers(12)although this is often determined by local protocols.
Types of Catheter
A Cochrane review(16)has found that patients requiring catheterisation for fourteen days had less bacteruria, discomfort and decreased need for recatheterisation when supapubic catheters (SPCs) were used. Another Cochrane review found in patients requiring catheterisation for 14 days or less that silver alloy impregnated catheters have been associated with decreased rates of UTI(19). In both cases, practical considerations have made their usage infrequent (Level 1A).
When to Remove Catheter
Another Cochrane review found there is suggestive, but inconclusive, evidence of a benefit from midnight removal of the in-dwelling urethral catheter. The evidence also suggests shorter hospital stay after early rather than delayed catheter removal, but the effects on other outcomes are unclear. There is little evidence on which to judge other aspects of management such as catheter clamping (Level 2A).
In another Systematic review, it was found that finasteride significantly reduced the risk of acute urinary retention and prostatectomy compared with placebo (urinary retention: 6.6% with placebo v.2.8% with finasteride; NNT 26, 95% CI 22 to 38; prostatectomy: 8.3% with placebo v.4.2% with finasteride; NNT 24, 95% CI 19 to 37)(12). It also found that finasteride significantly reduced the risks of acute urinary retention and the need for invasive therapy compared with placebo (risk reduction for acute urinary retention: 68%; P = 0.009; risk reduction for invasive therapy: 64%; P<0.001).
Urology referral is appropriate in the majority of cases of acute urinary retention, as this group of patients are likely to need surgical intervention in the future.
SPCs offer easier TWOC, lower rates of UTIs(9) and fewer urethral strictures(13) in comparison to urethral catheters, but practical considerations have made their usage infrequent.
The Bonanno technique uses a small calibre catheter with a needle for puncture within the lumen.
The other technique of suprapubic catheterisation utilises the ‘Bard’ trocar model.
Essentially the techniques are similar. Ensure there is adequate filling of the bladder, confirm by ultrasound, and utilise direct puncture behind the pubic bone angled downwards with the Bonanno or utilise a skin nick with blade contained in the kit and the trocar. Local anaesthesia is essential in both cases.
‘Bard’ Trocar model
Removal of a Non Deflating Catheter
Encountering difficulty when removing a catheter is a common problem. Several solutions have been described to deflate the balloon. Cutting the catheter itself only works when the valve flap that retains fluid is in the external segment. Overinflation may require up to 200 mls of fluid and always leaves retained balloon pieces that unless removed endoscopically, will act as a nidus for infection or stone formation(10).
Retention of catheter fragments is also common when corrosive substances such as ether and acetone are used. As these substances can cause a chemical cystitis they should not be used.
Ultrasound guidance may be used to rupture the balloon transabdominally. Sliding a central line guidewire down the balloon channel to release the retaining valve can also be effective. Again, in all cases, the balloon must be inspected to determine whether cystoscopy is necessary to remove fragments.
Remember the prostate is a heart shaped organ with the apex located distally. There is debate regarding prostate examination raising prostate specific antigen (PSA) and contaminating mid stream urine (MSU) collection.
Try and distinguish tenderness of the gland from the expected discomfort of a normal examination. A normal prostate can be said to feel like the end of a nose in consistency whereas cancerous nodules are said to feel more like the bony area of the chin.
Most cancer arises in the lateral areas of the gland. The severity of prostatic hypertrophy is more accurately determined by the severity of symptoms and size of residual volume than the actual size on rectal examination.
Common Problems with Catheters
- If there is phimosis and the opening is adequate, try to pass the catheter blind. If the opening is too narrow, try a smaller catheter. If in doubt, seek more expert help
- If the catheter will not pass the prostate, try a catheter with a larger diameter. The urethra at the site of the prostate is not narrow, but it is pushed flat by the surrounding prostate. A larger catheter pushes the prostate lobes back to the side to allow passage. Another option is to try a silicone catheter, as it is more rigid than a silicon latex catheter
- If the catheter does not pass the bladder neck, try a smaller size
Significant renal impairment +/- complications, significant post obstruction diuresis, sepsis, dehydration, and inability to manage at home e.g. dementia(6).
Female acute urinary retention (AUR) is relatively uncommon and often poorly managed. There are several common precipitants.
The underlying abnormality is often detrusor failure, not outlet obstruction. Investigations should focus on identifying serious or reversible causes and should include a detailed history and physical examination, urine dipstick, culture and pelvic ultrasound.
Pelvic examination, neurological assessment, urine culture and pelvic ultrasound should be performed on all females with AUR. Patients should be catheterised and reversible causes should be treated. Patients with apparently idiopathic retention should be referred to a urologist with an interest in bladder dysfunction for consideration of urodynamics.
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