Urinary retention describes an inability to completely empty the bladder. It is a relatively common complication in the post-surgical patient, so a clear understanding of its diagnosis, assessment and management is important.
The most common diagnostic signs or symptoms of acute urinary retention are:
- Little or no urine passed in the post-operative period
- A sensation of needing to void, without being able to micturate
- The retention of urine may be painless in patients with previous long-term urinary retention
- A suprapubic mass that is dull to percussion.
Patients presenting with urinary retention should be assessed for any neurological causes. In the immediate post-operative period, any neurological deficit is usually because the spinal or epidural anaesthetic has not yet worn off, but other more potentially serious neurological causes should be considered*.
*Spinal/epidural abscesses and haematomas are a very rare but important cause of post-operative urinary retention; if there is any suspicion of this, inform your senior immediately.
There are several risk factors for post-operative urinary retention:
- Age >50yrs
- Type of surgery
- Including pelvic surgery or arthroplasty, anorectal surgery, hernia repair and transurethral procedures
- Anaesthetic type (spinal or epidural)
- Neurological co-morbidities
- Drugs (antimuscarinics, alpha-antagonists, opiates)
Together with a thorough clinical assessment, the most important investigation is the ultrasonic bladder scan to identify the residual urine volume. Additional tests that may be required are:
- Routine bloods (U&Es) to monitor renal function (if the retention does not settle rapidly)
- Spinal MRI if spinal pathology suspected
A conservative approach may be taken in many patients; the majority of post-operative urinary retention will resolve spontaneously given time and withdrawal of any causative agents.
If the patient has a bladder volume >600ml, they will probably need catheterisation. In ambulatory patients, do this as an “in-out” procedure (used for drainage then immediate removal), otherwise it is advised to leave the catheter in overnight and try removing it the following morning.
If the patient remains in retention following in-out catheter, then they will need to be referred to the urologists for a Trial Without Catheter (TWOC) as an outpatient (usually in 6 weeks).