ATI Practical Nurse (PN) Comprehensive Exit Practice Exam 2026 - Free PN Exam Questions and Study Guide

The client at risk for urinary retention is the school-age child taking diphenhydramine. Diphenhydramine is an antihistamine commonly used to relieve symptoms of allergy, hay fever, and the common cold. One of the side effects of antihistamines like diphenhydramine is anticholinergic effects, which can include difficulty in urination or urinary retention. This occurs due to its action of blocking acetylcholine, a neurotransmitter that is involved in the contraction of the bladder muscles, thus potentially leading to retention.

In contrast, the other options represent situations that are less likely to induce urinary retention. A toddler with a respiratory infection may experience increased urinary output due to fever or fluid intake, a teenager with a urinary tract infection may experience urgency and frequency, making retention less likely in the context of the irritation caused by the infection, and an elderly client with hypertension, while perhaps at risk for various urinary issues, does not have a direct link to urinary retention through the provided context. Therefore, the child taking diphenhydramine is the most appropriately identified as being at risk for urinary retention due to the pharmacological effects of the medication.