Differential Diagnosis for Urinary Retention in a 53-year-old Male

Single most likely diagnosis

• Benign Prostatic Hyperplasia (BPH): The patient's symptoms of suprapubic pain, slow stream, feeling of incomplete bladder emptying, and a significantly enlarged prostate (41g) on pelvic sonogram are highly suggestive of BPH. The presence of bilateral calcifications and slightly thick bladder walls further supports this diagnosis.

Other Likely diagnoses

• Urethral Stricture: Given the patient's history of STDs and symptoms such as occasional splitting of the urinary stream, urethral stricture is a plausible cause of urinary retention. The patient's inability to perform uroflowmetry due to urinary retention also points towards a possible urethral stricture.
• Prostate Cancer: Although less likely than BPH, prostate cancer could cause urinary retention, especially in the presence of a heterogeneous prostate on sonogram. However, the normal digital rectal examination (DRE) reduces the likelihood of this diagnosis.
• Bladder Outlet Obstruction (BOO) due to Bladder Diverticulum: The presence of a bladder diverticulum could potentially cause BOO, leading to urinary retention. However, this would be less common compared to BPH or urethral stricture.

Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

• Neurogenic Bladder: Although less common, neurogenic bladder due to conditions like spinal cord injury, multiple sclerosis, or diabetes could cause urinary retention. It's crucial to rule out neurogenic causes, as they require specific management.
• Bladder Cancer: Although the pelvic sonogram did not show internal bladder lesions, bladder cancer could cause urinary retention, especially if there's a large tumor obstructing the bladder outlet.

Rare diagnoses

• Prostatic Abscess: A prostatic abscess could cause urinary retention, especially if it's large enough to obstruct the urethra. However, this would typically be accompanied by significant pain, fever, and other systemic symptoms.
• Urethral Cancer: Urethral cancer is a rare cause of urinary retention but should be considered, especially if there's a history of STDs or other risk factors.
• Foreign Body in the Urethra or Bladder: Although rare, a foreign body could cause urinary retention. This would typically be accompanied by a history of instrumentation or insertion of objects into the urethra.