Urinary Tract Infection (UTI): This is the most common cause of dysuria in men, especially at the age of 50. Bacterial infections, such as those caused by E. coli, are typical and can be effectively treated with antibiotics.

Prostatitis: Inflammation of the prostate gland can cause dysuria, and it's more common in men of this age group. It can be acute or chronic and is often caused by bacterial infection.
Urethritis: Inflammation of the urethra, often due to sexually transmitted infections (STIs) like gonorrhea or chlamydia, can cause dysuria. Although less common in older men, it remains a consideration, especially with a history of unprotected sex.
Benign Prostatic Hyperplasia (BPH): While not an infection, BPH can cause urinary symptoms including dysuria due to obstruction of the urethra by the enlarged prostate.

Kidney Stones: Although not always presenting with infection, kidney stones can cause severe pain and dysuria. Missing this diagnosis could lead to severe complications, including obstruction and kidney damage.
Tuberculosis of the Urinary Tract: A less common but serious condition that can present with dysuria among other symptoms. It's crucial not to miss this diagnosis due to its potential for severe consequences if left untreated.
Cancer of the Urinary Tract: Including prostate, bladder, or kidney cancer, which can present with dysuria. Early detection is critical for effective treatment and survival.

Interstitial Cystitis: A chronic condition causing bladder pressure, bladder pain, and sometimes pelvic pain. The symptoms can resemble those of a UTI but without the presence of an infection.
Schistosomiasis: A parasitic infection that can affect the urinary tract, more common in certain parts of the world. It can cause dysuria and hematuria but is rare in areas without endemic disease.
Reiter's Syndrome: A form of reactive arthritis that can occur after certain bacterial infections, leading to symptoms including dysuria. It's part of a group of conditions known as spondyloarthritis.