Final answer:
A patient receiving epidural analgesia should be monitored for urinary retention as it affects the nerves that control bladder function. The correct option is C.
Step-by-step explanation:
The patient receiving epidural analgesia should be monitored for the side effect of urinary retention. This occurs due to the effect of the analgesia on the nerves that control bladder function, often leading to a reduced ability to sense a full bladder or initiate urination.
While the antiduresis effect of increased aldosterone secretion could lead to a decrease in urine output, it is not directly related to epidural analgesia, making urinary retention the correct answer.