From the Guidelines
Ultrasound, specifically US duplex Doppler scrotum and US scrotum, is the recommended initial imaging modality for evaluating testicular pain, as it provides excellent visualization of testicular structures without radiation exposure and helps distinguish between inflammatory conditions and torsion. According to the American College of Radiology Appropriateness Criteria 1, US duplex Doppler scrotum and US scrotum are equivalent alternatives and are usually appropriate as the initial imaging for the acute onset of scrotal pain without trauma or antecedent mass in an adult or child.
The use of ultrasound in this context is supported by its high sensitivity and specificity for detecting common causes of testicular pain, such as epididymitis, orchitis, torsion, trauma, and masses 1. Color Doppler ultrasound is particularly valuable as it assesses blood flow, helping distinguish between inflammatory conditions (increased flow) and torsion (decreased or absent flow). Key ultrasound findings in testicular torsion include an enlarged heterogeneous testis, ipsilateral hydrocele, skin thickening, and no color Doppler flow in the testis or spermatic cord 1.
In contrast, MRI may occasionally be used as a second-line option when ultrasound findings are inconclusive or to better characterize complex masses, but it should not delay treatment in emergency situations 1. CT scans are generally not indicated for isolated testicular pain unless there is concern for associated abdominal pathology or trauma. Prompt imaging is essential, as testicular torsion represents a true urologic emergency with potential for testicular loss if not addressed within 4-6 hours of symptom onset.
Some key points to consider when using ultrasound for testicular pain include:
- The sensitivity and specificity of color Doppler US for the detection of testicular torsion can be variable, with reports ranging from 69% to 96.8% and 87% to 100%, respectively 1
- False-negative Doppler evaluations can occur in the setting of partial torsion and spontaneous detorsion, while false-positive Doppler evaluation can be seen in infants and young boys who often have normally reduced intratesticular blood flow 1
- The contralateral asymptomatic testicle should be used as an internal control to help interpret ultrasound findings 1
- US findings in patients with epididymitis include an enlarged and hypoechoic epididymis due to edema, reactive hydroceles, and scrotal wall thickening, with color Doppler imaging showing increased blood flow corresponding to hyperemia 1.
From the Research
Imaging Modalities for Testicular Pain
- Ultrasonography is the ideal noninvasive imaging modality for evaluation of scrotal abnormalities, including testicular pain 2, 3, 4.
- Scrotal ultrasound can detect, locate, and characterize both intratesticular and extratesticular masses and other abnormalities 2.
- A 12-17 MHz high frequency linear array transducer provides excellent anatomic detail of the testicles and surrounding structures 2.
- Color and spectral Doppler analysis can be used to assess vascular perfusion 2, 5.
Specific Conditions
- Testicular torsion: scrotal ultrasound can be misleading in cases of subacute testicular torsion and should not be used as the sole diagnostic tool 6.
- Epididymitis: ultrasonography can differentiate epididymitis from testicular torsion and other causes of scrotal pain 2, 4.
- Testicular rupture and Fournier gangrene: ultrasound is useful in diagnosing these acute urologic emergencies 3, 4.
Diagnostic Accuracy and Safety
- Doppler ultrasonography (DUS) has a sensitivity of 85.2% and specificity of 52.7% in diagnosing testicular torsion 5.
- DUS receipt was not significantly associated with orchidectomy, but the delay to surgery was 1 hour longer 5.
- Ultrasound scan of the scrotum before surgery for patients with suspected testicular torsion is safe, feasible, and useful in selected cases, but should not delay or replace surgery in cases with a strong clinical suspicion 5.