Hydrocele: This condition, characterized by the accumulation of fluid around a testicle, is common in older men and can cause testicular swelling. The age of the patient and the nature of the swelling make hydrocele a plausible initial consideration.

Epididymitis: Inflammation of the epididymis, which can be caused by infection, is a possible cause of testicular swelling. Although more common in younger men, it can occur in older adults, especially if there's an underlying urinary tract issue.
Testicular Torsion: Although less common in older men, testicular torsion is a significant consideration due to its urgency. However, it typically presents with acute pain, which may not be explicitly mentioned here.
Varicocele: An enlargement of the veins within the scrotum, varicocele can cause swelling and is more common on the left side, which aligns with the patient's symptoms.

Testicular Cancer: While not the most common cause of testicular swelling, testicular cancer is critical to rule out due to its potential severity and the importance of early detection. It can present with a painless testicular mass or swelling.
Acute Epididymo-Orchitis: This condition involves inflammation of both the epididymis and testis, often due to bacterial infection. It's crucial to identify and treat promptly to prevent complications.

Spermatocele: A cystic structure filled with sperm, which can cause swelling but is typically painless and less common.
Cystic Dysplasia of the Testis: A rare congenital anomaly that can cause testicular swelling, though it would be unusual to present for the first time in an elderly man.
Filariasis: In endemic areas, filariasis can cause hydrocele and testicular swelling due to parasitic infection. However, this would be rare in most clinical settings outside of specific geographic locations.