Nursing care
Postoperative Urinary Retention nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Postoperative urinary retention is the inability to void adequately after surgery, most often from anaesthetic and opioid effects on bladder tone. If a patient has not voided within six to eight hours postoperatively, perform a bladder scan; a residual volume over 400 mL warrants catheterisation. Early recognition prevents bladder overdistension and detrusor injury.
What it is and why it happens
Postoperative urinary retention is the failure to empty the bladder adequately after surgery, distinct from a low urine output caused by poor renal perfusion. The bladder fills normally but the patient cannot initiate or sustain a void, or voids only a small fraction of what has accumulated.
The mechanism is pharmacologic and physiologic, not structural, in most postoperative cases. General and spinal anaesthetics suppress detrusor muscle contractility and blunt the urge to void. Opioids used for pain control increase urethral sphincter tone and reduce bladder sensation, compounding the effect. Pelvic, spinal, and lower abdominal procedures add direct nerve or bladder-adjacent trauma on top of the pharmacologic cause, which is why retention risk is higher after those surgeries than after, say, upper limb procedures.
How it presents — what you will actually see
The patient often reports a full or pressured feeling in the lower abdomen but is unable to void, or voids a small, dribbling amount that provides no relief. Suprapubic distension is frequently palpable and sometimes visible, particularly in a patient of lower body habitus.
Restlessness and agitation can appear, and in a postoperative patient this is sometimes mistaken for pain from the surgical site itself rather than bladder distension. Some patients report no sensation of fullness at all, especially with residual spinal anaesthesia or high-dose opioids, so the absence of a complaint does not rule out retention. Overflow incontinence, small frequent leakage without full emptying, can also be the presenting sign rather than complete inability to void.
Nursing assessment priorities
Track time since last void against the six to eight hour postoperative window rather than relying on the patient volunteering a complaint. Palpate and percuss the suprapubic area for distension, and correlate with intake and output records, since a patient who has received significant intravenous fluid intraoperatively is at higher risk.
A bladder scan is the assessment of choice once six to eight hours have passed without voiding, and it is non-invasive, quick, and considerably more reliable than palpation alone in an obese or edematous patient. Document the scanned volume precisely rather than describing it as 'full' or 'distended', since the exact figure determines the next intervention.
Interventions and what to do first
If the patient has not voided within six to eight hours of surgery, bladder scan first before assuming catheterisation is required. Encourage ambulation as soon as it is permitted, position the patient upright rather than supine for attempts to void, run water, and provide privacy, since simple measures often resolve mild retention.
A scanned residual over 400 mL is the threshold for catheterisation, either intermittent or indwelling depending on the anticipated duration of retention and facility protocol. Straight catheterisation is generally preferred for a single episode expected to resolve as anaesthetic and opioid effects wear off, reserving an indwelling catheter for recurrent or higher-volume retention. Notify the surgical or anaesthesia team if retention persists beyond the expected recovery window for the anaesthetic used.
Complications to watch for
Prolonged overdistension can injure the detrusor muscle itself, leading to a bladder that loses contractile function even after the precipitating anaesthetic or opioid has cleared. This is the reason retention is treated proactively rather than left to resolve on its own over many hours.
Urinary tract infection risk rises with any catheterisation, and rises further with repeated intermittent catheterisation or a prolonged indwelling catheter. Overflow incontinence can be mistaken for resolved retention when in fact the bladder remains significantly distended, so a normal-looking output on the bed pad does not confirm adequate emptying without a follow-up scan.
Patient teaching before discharge
Teach the patient to recognise a full or pressured bladder sensation returning as anaesthetic effects fully resolve, and to attempt to void at regular intervals even without a strong urge in the first day or two after surgery. Explain that opioid pain medication can continue to affect bladder emptying at home, so the same risk applies for as long as opioids are being taken.
Advise the patient to report any inability to void, a weak or dribbling stream, or lower abdominal distension after discharge rather than waiting to see if it resolves. If they are discharged with a catheter, teaching covers catheter care, signs of infection, and the plan and timeline for removal or a voiding trial.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our reduction of risk potential practice questions are the closest set to what this page covers.
One question from the reduction of risk potential set
Four hours after a cardiac catheterization via the right femoral artery, the nurse notes the client's right dorsalis pedis pulse is now faint and the foot is cool and pale. What is the nurse's priority action?
Rationale
A pulse that was present and is now faint, with a cool, pale extremity distal to the puncture site, is arterial occlusion until proven otherwise — a limb-threatening complication that needs the provider now. Documenting and rechecking wastes the window, warming treats the symptom and masks the change, and asking the client to move the ankle neither restores flow nor gives you new information.
Answer: C
Common questions
How long after surgery should a patient void before it's a concern?
A patient should be expected to void within six to eight hours of surgery. If that window passes without a void, a bladder scan is the next step rather than waiting further, since prolonged distension risks injury to the bladder muscle itself.
What bladder scan volume requires catheterisation?
A residual volume over 400 mL on bladder scan is the threshold that warrants catheterisation. Volumes below that may be managed with conservative measures such as ambulation and positioning, with reassessment if the patient still cannot void.
Why do opioids cause urinary retention after surgery?
Opioids increase urethral sphincter tone and reduce the sensation of bladder fullness, both of which interfere with normal voiding. This effect is separate from the anaesthetic's suppression of detrusor contractility, and the two combine to significantly raise retention risk in the postoperative period.
Is a straight catheter or an indwelling catheter used for postoperative retention?
A straight, intermittent catheter is generally preferred for a single expected episode of retention that should resolve as medication effects wear off. An indwelling catheter is reserved for recurrent retention or when ongoing high residual volumes are expected over a longer period.
More on reduction of risk potential