Which symptom is commonly associated with acute epididymitis?

Acute epididymitis is characterized by inflammation of the epididymis, which often manifests through several hallmark symptoms. One of the primary symptoms is scrotal edema, where there is swelling of the scrotum due to increased blood flow and inflammatory response associated with the condition. This swelling is often accompanied by tenderness and significant pain in the affected area.

The other symptoms listed, while they may occur in various urological or systemic conditions, are not typically associated with acute epididymitis itself. For example, flank pain is more characteristic of renal issues, groin stiffness might suggest musculoskeletal problems, and foul-smelling urine can indicate a urinary tract infection but does not directly correlate with epididymitis. Thus, scrotal edema is the symptom most commonly recognized in cases of acute epididymitis, making it the best answer to the question.