What is the differential diagnosis for a patient presenting with a left swollen testicle?

Differential Diagnosis for Left Swollen Testicle

The differential diagnosis for a left swollen testicle must prioritize testicular torsion as the most critical diagnosis to exclude, followed by epididymitis/epididymo-orchitis, torsion of testicular appendage, trauma-related pathology, inguinal hernia, testicular tumor, and segmental testicular infarction. 1, 2

Immediate Life-of-Testis Threatening Condition

Testicular Torsion (Surgical Emergency)

• This is the most critical diagnosis that must be ruled out first, as testicular viability is compromised if not treated within 6-8 hours of symptom onset. 1, 2, 3
• Presents with sudden onset of severe scrotal pain developing within minutes, often accompanied by nausea and vomiting 1, 3, 4
• Physical examination reveals a high-riding, tender, swollen, and firm testis with a negative Prehn sign (pain NOT relieved with testicular elevation) 1, 2, 3, 5
• Normal urinalysis does not exclude testicular torsion 1, 3
• More common in adolescents with bimodal distribution (neonates and postpubertal boys), but can occur at any age 1, 4
• Up to 50% of patients report previous similar episodes of pain 5

Most Common Causes by Age

Epididymitis/Epididymo-Orchitis (Most Common in Adults)

• Overwhelmingly the most common cause of testicular pain in adults, representing approximately 600,000 cases annually in the United States 1
• Characterized by gradual onset of pain over hours to days, distinguishing it from torsion 1, 3
• May have abnormal urinalysis showing pyuria or bacteriuria, though normal urinalysis does not exclude the diagnosis 1, 3
• Physical examination shows enlarged, tender epididymis with possible scrotal wall thickening 1, 2
• Ultrasound demonstrates enlarged epididymis with increased blood flow on color Doppler 1, 2
• Up to 20% have concomitant orchitis 1

Torsion of Testicular Appendage (Most Common in Prepubertal Boys)

• The most common cause of testicular pain in prepubertal boys 1, 3
• The "blue dot sign" is pathognomonic but only seen in 21% of cases 1
• Ultrasound shows normal testicular perfusion with localized hyperemia near the appendage 1
• Generally less severe presentation than testicular torsion 1

Additional Important Differential Diagnoses

Incarcerated/Strangulated Inguinal Hernia

• Can present as acute scrotal swelling and pain 6
• Physical examination may reveal a mass that extends into the inguinal canal 6
• Requires urgent surgical evaluation if strangulated 6

Testicular Trauma/Hematoma/Rupture

• History of trauma is key, though progressive worsening pain with a firm, tender testicle after trauma suggests torsion rather than simple injury 3
• Ultrasound can identify testicular rupture, which requires immediate surgical exploration with debridement and tunical closure 2
• Traumatic hematoma may present similarly but without the time-sensitive urgency of torsion 4

Segmental Testicular Infarction

• Presents with a classic wedge-shaped avascular area on ultrasound, though may also appear as round lesions with variable Doppler flow 1, 2
• Median age of presentation is 37-38 years 1
• Can mimic testicular torsion or tumor clinically 1

Testicular Tumor

• Typically presents as painless scrotal mass, but can present with pain if there is rapid growth or hemorrhage 4
• Requires ultrasound evaluation and tumor marker assessment if suspected 1

Acute Idiopathic Scrotal Edema

• Rare, self-limiting condition primarily affecting prepubertal boys but can occur in adults 1, 2
• Usually painless or minimally painful with marked scrotal wall thickening 1, 2
• Ultrasound shows heterogeneous striated appearance of scrotal wall with increased peritesticular blood flow but normal testicular vascularity 1
• Diagnosis of exclusion 1

Fournier's Gangrene

• Life-threatening necrotizing fasciitis of the perineum and scrotum 6
• Presents with severe pain, systemic toxicity, crepitus, and rapidly progressive scrotal swelling 6
• Requires emergency surgical debridement 6

Critical Clinical Pitfalls

• There is significant overlap in clinical presentation between different causes of acute scrotal pain, making definitive clinical diagnosis challenging without imaging 1, 3
• Never delay surgical consultation for imaging or analgesia when testicular torsion is suspected, as pain relief may mask worsening ischemia 3
• Color Doppler ultrasound has false-negative rates of up to 30%, particularly with partial torsion or spontaneous detorsion 1, 2
• Normal urinalysis does not exclude either testicular torsion or epididymitis 1, 3
• Starting antibiotics empirically without ruling out torsion delays correct diagnosis and treatment 3
• In prepubertal boys, normally reduced intratesticular blood flow can mimic torsion on Doppler, leading to false-positive evaluations 1, 2