Differential Diagnosis for Left Testicular Pain with Normal Ultrasound

Single Most Likely Diagnosis

• Epididymitis: This is the most common cause of acute testicular pain and can have a normal ultrasound if the inflammation is not severe enough to cause significant changes in testicular or epididymal size or echotexture. The pain is often accompanied by other symptoms such as swelling, redness, and increased temperature of the scrotum.

Other Likely Diagnoses

• Testicular Torsion (early stages): Although ultrasound can be normal, this condition is a medical emergency. Early stages might not show significant changes on ultrasound, but clinical suspicion remains high if the pain is severe and sudden.
• Orchitis: Inflammation of the testis, which can be viral or bacterial, might present with pain and have a normal ultrasound if the changes are not pronounced.
• Varicocele: A varicocele can cause a dull, aching pain, especially if it becomes large enough to put pressure on the testicle or surrounding structures. Ultrasound might be normal if the varicocele is small or not well visualized.

Do Not Miss Diagnoses

• Testicular Cancer: Although less common, testicular cancer can present with pain and a normal ultrasound, especially if the tumor is small or not significantly altering the testicular architecture.
• Appendix Testis Torsion: A condition where the small appendage attached to the testis twists, cutting off its blood supply. It's less common than testicular torsion but can present similarly and is a surgical emergency.
• Intratesticular Hematoma or Spermatic Cord Injury: These conditions might not always be visible on ultrasound, especially if they are small or the patient is imaged early after the injury.

Rare Diagnoses

• Spermatocele or Epididymal Cyst: These are benign cysts that can cause discomfort or pain, especially if they become large or rupture.
• Henoch-Schönlein Purpura (HSP): A systemic vasculitis that can cause testicular pain among other symptoms, including skin rash, joint pain, and gastrointestinal symptoms.
• Polyarteritis Nodosa (PAN): A systemic vasculitis that can affect multiple organs, including the testes, causing pain and potentially other systemic symptoms.

Each of these diagnoses has a different level of urgency and treatment approach, emphasizing the importance of a thorough clinical evaluation and potentially further diagnostic testing beyond ultrasound.