What is the differential diagnosis for a 40-year-old male presenting with left testicular pain, stable vital signs, and urinary frequency without urgency, hematuria, or penile discharge?

Differential Diagnosis for Left Testicular Pain in a 40-Year-Old Male

In this 40-year-old male with isolated left testicular pain, urinary frequency, stable vital signs, and no signs of acute inflammation or torsion, the most likely diagnosis is epididymitis, which represents approximately 600,000 cases annually in the United States and is overwhelmingly the most common cause of testicular pain in adults. 1

Primary Differential Diagnoses

Epididymitis/Epididymo-orchitis (Most Likely)

• This is the leading diagnosis given the patient's age, as epididymitis is the most common cause of testicular pain in adults over 25 years 1
• Characterized by gradual onset of pain (though can be acute) and may present with urinary frequency as seen in this patient 1
• Normal urinalysis does not exclude epididymitis 1
• Ultrasound findings would show enlarged epididymis with increased blood flow on Doppler 1
• Common causes in adults include urinary tract infection or prostatitis 2

Testicular Torsion (Less Likely but Critical to Exclude)

• Must be ruled out urgently despite being rare in patients over 35 years of age 1
• Typically presents with abrupt onset of severe scrotal pain, which differs from this patient's presentation 1
• The absence of testicular swelling or discoloration makes this less likely, but torsion can present with variable findings 1
• Negative Prehn sign (pain not relieved with testicular elevation) is a key distinguishing feature 1
• Requires surgical intervention within 6-8 hours to prevent testicular loss 1, 3

Testicular Malignancy

• Testicular cancer is the most common malignancy in men 20-35 years of age, though this patient is slightly older 4
• Typically presents as a painless testicular mass rather than acute pain 4
• Risk factors include cryptorchidism, family history, infertility, tobacco use, and white race 4
• Germ cell testicular tumors constitute approximately 95% of all testicular tumors 5

Segmental Testicular Infarction

• Presents with a classic wedge-shaped avascular area on ultrasound 1
• May also present as round lesions with variable Doppler flow 1
• Less common but should be considered in the differential

Torsion of Testicular Appendage

• Most common cause of testicular pain in prepubertal boys, making it unlikely in this 40-year-old 1
• "Blue dot sign" is pathognomonic but only seen in 21% of cases 1

Diagnostic Approach

Immediate Clinical Assessment

• Determine the exact timing and onset of pain: abrupt onset suggests torsion, while gradual onset suggests epididymitis 1
• Assess for Prehn sign: pain relief with testicular elevation suggests epididymitis rather than torsion 1
• Evaluate for systemic signs: fever may accompany both conditions, creating diagnostic overlap 2

Laboratory Testing

• Urinalysis is essential despite the patient denying urgency or hematuria, as it may reveal pyuria or bacteriuria supporting epididymitis 1, 2
• Normal urinalysis does not exclude either epididymitis or testicular torsion 1

Imaging Studies

• Duplex Doppler ultrasound of the scrotum is the first-line imaging modality 1
• For epididymitis: expect enlarged epididymis with increased blood flow on Doppler 1
• For torsion: expect decreased or absent blood flow, possible "whirlpool sign" of twisted spermatic cord 1
• Ultrasound sensitivity for torsion ranges from 69-96.8% with specificity of 87-100% 1
• Power Doppler is particularly useful for detecting low-flow states 1

Critical Clinical Pitfalls

Overlapping Presentations

• Significant overlap exists in clinical presentation between different causes of acute scrotal pain, making diagnosis challenging 1
• Both epididymitis and testicular torsion can present with scrotal pain, swelling, fever, and pyuria 2
• False-negative Doppler evaluations occur in 30% or more of cases, particularly with partial torsion or spontaneous detorsion 1

Age-Related Considerations

• While testicular torsion is rare over age 35, it cannot be completely excluded based on age alone 1
• The patient's history of urinary frequency without other urinary symptoms is more consistent with epididymitis 1

Urgent Surgical Consultation

• If clinical suspicion for torsion remains despite imaging, immediate urological consultation is mandatory 1
• Surgical exploration should never be delayed when clinical suspicion is high, even with equivocal imaging 1

Management Algorithm

1. Obtain detailed pain history: onset (sudden vs. gradual), duration, severity, and associated symptoms 1
2. Perform focused physical examination: assess for Prehn sign, testicular position, swelling, and tenderness 1
3. Order urinalysis to evaluate for infection or inflammation 1, 2
4. Obtain urgent Duplex Doppler ultrasound to differentiate between diagnoses 1
5. If torsion suspected clinically: immediate urological consultation regardless of imaging results 1
6. If epididymitis confirmed: initiate appropriate antibiotic therapy, bed rest, scrotal elevation, and analgesics 1