Epididymitis: This is the most common cause of acute scrotal pain in young men, often associated with urinary symptoms and microscopic hematuria. The presence of pain, especially if it's accompanied by symptoms like dysuria or frequency, points towards an inflammatory process such as epididymitis.

Orchitis: Inflammation of the testicle, which can occur alone or in conjunction with epididymitis (epididymo-orchitis). It's a common cause of scrotal pain and can be associated with microscopic hematuria if there's an infectious or inflammatory process affecting the urinary tract.
Testicular Torsion: Although more commonly associated with sudden, severe pain and a hordeolum (blue dot sign), testicular torsion can sometimes present with less severe pain and may have associated microscopic hematuria due to the interruption of blood supply causing tissue damage.
Urethritis: Inflammation of the urethra, often due to infection, can cause dysuria, frequency, and microscopic hematuria, which might be associated with referred scrotal pain.

Testicular Tumor with Hemorrhage: Although rare, testicular tumors can cause scrotal pain and, if there's hemorrhage into the tumor, microscopic hematuria might be present. Missing this diagnosis could have severe consequences.
Kidney Stone: A small kidney stone passing through the ureter can cause severe pain (renal colic) and microscopic hematuria. The pain can sometimes be referred to the scrotum, especially if the stone is in the distal ureter.
Intrascrotal Hematoma: Bleeding into the scrotum can cause pain and swelling. If the hematoma is large enough, it might cause pressure on the urethra or bladder, leading to urinary symptoms including microscopic hematuria.

Henoch-Schönlein Purpura (HSP): A systemic vasculitis that can cause scrotal pain, hematuria, and other symptoms like purpura and joint pain. It's rare but should be considered in the differential diagnosis of scrotal pain with hematuria.
Sarcoidosis: A systemic disease that can affect multiple organs, including the testes and kidneys, leading to scrotal pain and hematuria. It's a rare cause but should be considered in patients with other systemic symptoms.
Polyarteritis Nodosa (PAN): A vasculitis that can affect various organs, including the kidneys and testes, potentially causing scrotal pain and hematuria. It's a rare condition but important to diagnose due to its potential for serious complications.