Correct interpretation at 8 hours
The protocol has two separate limits: catheterize if a bladder scan shows more than 500 mL, or if the volume left in the bladder after voiding is more than 200 mL. At 8 hours she voided only 90 mL, and a scan right after voiding showed 380 mL. Because this is a post-void residual, the 200-mL limit applies, so she has urinary retention even though 380 mL is below the 500-mL limit that applies before voiding. The nurse catheterizes as the protocol directs.
Applying the right limit to the right measurement
A pre-void scan measures how full the bladder is before the client tries to void; a large volume suggests she cannot start voiding effectively. A post-void residual (PVR) measures how much remains after she has voided; it tells the nurse whether the bladder is emptying. At 4 hours, the scan of 420 mL was before voiding and was below 500 mL, and she then voided a good 300 mL, so no action was needed. At 8 hours, the small void of 90 mL followed by 380 mL remaining shows incomplete emptying. The common error is comparing the post-void number with the pre-void limit.
| Time | Measurement | Limit that applies | Result |
|---|
| 4 hours | Scan 420 mL before voiding; voided 300 mL | Pre-void: more than 500 mL | No retention |
| 8 hours | Voided 90 mL; residual 380 mL | Post-void: more than 200 mL | Retention |
Why retention is common after groin surgery
Urinary retention after inguinal or femoral hernia repair is common. Contributing factors include anesthesia, opioid analgesia, pain and spasm near the operative site, older age, and IV fluids that fill the bladder quickly. An overdistended bladder can stretch the detrusor muscle and make later voiding harder, so timely catheterization matters.
Why the distractors are wrong
No retention applies the wrong limit. Bladder injury would typically cause hematuria or painful urination, and her urine is clear yellow. A fluid deficit is unlikely because the kidneys are clearly producing urine; 380 mL is sitting in the bladder. A small voided volume with a large residual means poor emptying, not low production.
Exam takeaway
Watch out In protocol questions, first identify whether each number is a pre-void scan or a post-void residual, then apply the matching limit.