Final answer:
A distended bladder is an adverse effect of oxybutynin, the medication taken by a client with renal calculi for pain management.
Step-by-step explanation:
A nurse caring for a client with renal calculi who is taking oxybutynin for pain should be aware of the drug's potential side effects. Among the listed options, a distended bladder should be identified as an adverse effect, as oxybutynin is an antispasmodic medication that can lead to urinary retention. The medication is used for bladder muscle dysfunction and works by relaxing the muscles to help decrease problems of urgency and frequent urination. However, it may cause the inability of the bladder to empty completely, leading to distension.
Conversely, increased salivation, bradycardia, and tinnitus are not typical adverse effects of oxybutynin. Anticholinergic drugs like oxybutynin are more likely to cause decreased salivation, and while cardiovascular effects such as tachycardia may occur, bradycardia is not commonly associated with this medication. Tinnitus is not a recognized side effect of this drug class.