What are the differential diagnoses for a patient with acute onset of right-sided lower back pain and right testicular inflammation, without a history of trauma, and is undergoing a Doppler ultrasound of the scrotum?

Differential Diagnoses for Right-Sided Lower Back Pain with Right Testicular Inflammation

Primary Differential Diagnosis

The most critical diagnosis to exclude immediately is testicular torsion, despite the provider's reassurance, because testicular viability is compromised if not treated within 6-8 hours of symptom onset. 1 The Doppler ultrasound being performed is the correct next step and should not be delayed. 1

Key Differentials in Order of Clinical Priority:

1. Testicular Torsion (Surgical Emergency)

• Must be ruled out first despite absence of trauma history, as it can occur spontaneously 1
• Typically presents with abrupt onset of severe scrotal pain, though presentation can vary 1
• The provider's assessment that "it's not torsion" should be confirmed with imaging, as clinical examination alone has significant limitations 1
• Critical timeframe: Surgical intervention must occur within 6-8 hours to prevent permanent testicular loss 1
• Color Doppler findings that confirm torsion include:
  • Decreased or absent blood flow to the affected testicle 1
  • "Whirlpool sign" of twisted spermatic cord (96% sensitivity) 1
  • Enlarged heterogeneous testis appearing hypoechoic 1
• Important caveat: False-negative Doppler evaluations occur in 30% or more of cases, particularly with partial torsion or early presentation 1

2. Epididymitis/Epididymo-orchitis (Most Common in Adults)

• This is 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 (unlike the acute presentation described) 1
• Doppler ultrasound findings include:
  • Enlarged epididymis with increased blood flow on color Doppler 1
  • Scrotal wall thickening and possible hydrocele 1
  • Up to 20% concomitant orchitis rate 1
• May have abnormal urinalysis, though normal urinalysis does not exclude the diagnosis 1

3. Renal/Ureteral Stone with Referred Pain

• The provider's suggestion of kidney stone is reasonable given the right-sided lower back pain component
• Ureteral stones can cause referred pain to the ipsilateral testicle via shared nerve pathways
• However, this would not typically cause testicular inflammation/swelling
• Key distinguishing feature: Stone pain is typically colicky and wave-like, often with hematuria

4. Segmental Testicular Infarction

• Presents with wedge-shaped avascular area on ultrasound 1
• Can also appear as round lesions with variable Doppler flow 1
• Median age of presentation is 37-38 years 1

5. Torsion of Testicular Appendage

• Most common in prepubertal boys, but can occur in adults 1
• Shows normal testicular perfusion with localized hyperemia near the appendage 1
• "Blue dot sign" is pathognomonic but only seen in 21% of cases 1

Critical Clinical Considerations

Why the Doppler Ultrasound is Essential:

The ordered Doppler ultrasound has excellent diagnostic accuracy but is not perfect:

• Sensitivity ranges from 69-96.8% for testicular torsion 1, 2
• Specificity ranges from 87-100% 1, 2
• Power Doppler is particularly useful for detecting low-flow states and should be included in the examination 1

Key Ultrasound Protocol Should Include:

• Grayscale examination to assess testicular homogeneity and identify the "whirlpool sign" 1
• Color Doppler assessment comparing perfusion to the contralateral testicle (used as internal control) 1
• Power Doppler for increased sensitivity to slow-flow states 1
• Spectral Doppler analysis of upper, mid, and lower poles of each testicle 1

Management Algorithm Based on Doppler Results:

If Doppler Shows Decreased/Absent Flow:

• Immediate urological consultation and surgical exploration regardless of other findings 1
• Do not delay for additional imaging or testing 1
• Complete torsion (>450 degrees) shows absent arterial and venous flow 1

If Doppler Shows Increased Flow:

• Consistent with epididymitis/epididymo-orchitis 1
• Management includes bed rest, scrotal elevation, analgesics, and appropriate antibiotic therapy 1
• Consider urinalysis and urine culture if not already obtained 1

If Doppler is Normal but Clinical Suspicion Remains High:

• Do not be falsely reassured - false-negative evaluations occur in up to 30% of cases 1
• Partial torsion can show diminished arterial velocity and decreased diastolic flow rather than complete absence 1
• Immediate urological consultation is still warranted if clinical suspicion for torsion remains high 1

Common Pitfalls to Avoid:

• Never assume absence of trauma excludes torsion - most cases occur spontaneously 1
• Age is not protective - while torsion is more common in adolescents, it can occur in adults 1
• Normal urinalysis does not exclude torsion 1
• Significant overlap exists in clinical presentation between different causes of acute scrotal pain 1
• Clinical examination alone is insufficient - imaging is essential 2, 3

Regarding the Kidney Stone Hypothesis:

While the provider's suggestion of a kidney stone is plausible for the back pain component, testicular inflammation/swelling is not typically caused by renal stones alone. If a stone is present, it may be a concurrent finding rather than the sole explanation for the testicular symptoms. The Doppler ultrasound will help clarify whether the testicular inflammation represents a separate acute scrotal pathology requiring different management.