Which of the following is a common sign of urinary retention in postoperative patients?

A distended bladder is recognized as a common sign of urinary retention in postoperative patients. After surgery, particularly surgeries involving the pelvis, abdomen, or those that may impact the nervous system, patients often experience difficulty with urination. This can result from factors such as anesthesia effects, pain management, and decreased mobility. A distended bladder occurs when urine accumulates in the bladder, leading to abdominal discomfort and an increased urge to void. Medical staff can assess for this condition by palpating the abdomen or using ultrasound to visualize bladder distention, indicating that the patient's bladder is unable to empty fully.

The other options reflect conditions that are atypical for urinary retention. Decreased serum creatinine suggests improved kidney function, while frequent urination and increased urine output would indicate the bladder is functioning effectively and not retaining urine. Thus, a distended bladder stands out as the primary indicator of urinary retention in postoperative patients.