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Scrotal Doppler Ultrasound Scanning Protocol
1. Introduction
Scrotal Doppler ultrasound is a non-invasive imaging technique used to assess the testes, epididymis, spermatic cord, and scrotal blood flow. It is commonly performed for acute scrotal pain, testicular masses, trauma, and infertility evaluation.
2. Patient Preparation
- Position:
- The patient should lie supine with legs slightly abducted.
- A towel can be placed under the scrotum for support.
- Gel Application:
- Apply warm ultrasound gel to prevent scrotal contraction.
- Transducer Selection:
- Use a high-frequency linear probe (7.5–15 MHz) for optimal resolution.
- Patient Instructions:
- Instruct the patient to remain still during the exam.
- Valsalva maneuver may be requested if evaluating for varicocele.
3. Scanning Technique
A. Gray-Scale (B-Mode) Imaging
➤ Evaluate Scrotal Structures
- Testes: Assess for size, shape, echotexture, and masses.
- Epididymis: Check for enlargement, cysts, or inflammation.
- Scrotal Wall: Look for thickening, edema, or fluid collections.
- Tunica Vaginalis: Assess for hydrocele or hematocele.
➤ Key Measurements
- Testicular Length: 3.5–5 cm
- Testicular Width: 2–3 cm
- Testicular Volume: 12–25 mL (calculated as L × W × H × 0.52)
- Epididymal Head: <1 cm (normal size)
B. Color Doppler Imaging
➤ Assess Vascularity
- Compare intrinsic testicular blood flow bilaterally.
- Look for hyperemia (increased flow in infection) or vascular absence (suggestive of torsion).
➤ Techniques
- Gain Settings: Optimize color Doppler sensitivity to detect low-flow signals.
- Box Size: Adjust to fit the testis for better visualization.
- Power Doppler: Used in low-flow states (e.g., torsion).
C. Spectral Doppler Analysis
➤ Evaluate Arterial and Venous Flow
- Arterial Flow: Low-resistance waveform
- Venous Flow: Continuous, non-pulsatile
➤ Testicular Arterial Assessment
| Artery | Normal Findings |
|---|---|
| Testicular Artery | Low-resistance flow (RI: 0.5–0.7) |
| Capsular & Centripetal Arteries | Continuous diastolic flow |
| Cremasteric & Deferential Arteries | Variable flow |
➤ Venous System Assessment
- Normal pampiniform plexus veins are <3 mm in diameter.
- Valsalva Maneuver: Performed to assess for venous reflux (varicocele diagnosis).
4. Special Maneuvers in Scrotal Doppler
➤ Valsalva Maneuver
- Used to evaluate varicocele (dilated pampiniform veins >3 mm).
- Reflux lasting >1 second confirms varicocele.
➤ Comparison with Contralateral Testis
- Always compare vascular flow bilaterally to detect abnormalities.
➤ Angle Correction for Spectral Doppler
- Angle should be ≤60° for accurate velocity measurements.
5. Interpretation of Doppler Findings
A. Normal Doppler Parameters
| Parameter | Normal Range |
|---|---|
| Peak Systolic Velocity (PSV) | 5–15 cm/s |
| End-Diastolic Velocity (EDV) | 2–5 cm/s |
| Resistive Index (RI) | 0.5–0.7 |
| Venous Diameter | <3 mm |
B. Abnormal Doppler Findings
| Condition | Doppler Findings |
|---|---|
| Testicular Torsion (Emergency) | Absent/reduced flow, high RI (>0.7), reversed diastolic flow |
| Epididymitis/Orchitis | Increased blood flow (hyperemia), RI <0.5 |
| Varicocele | Venous reflux >1 sec with Valsalva, vein diameter >3 mm |
| Testicular Tumor | Hypervascular mass with low RI (<0.5) |
| Scrotal Trauma | Hematoma (avascular), testicular rupture (disrupted flow) |
6. Summary of Scrotal Doppler Scanning Protocol
🔹 Patient Positioning: Supine with scrotal support
🔹 Transducer: High-frequency (7.5–15 MHz) linear probe
🔹 Gray-Scale Imaging: Evaluate size, echotexture, and masses
🔹 Color Doppler: Compare blood flow bilaterally
🔹 Spectral Doppler: Measure arterial and venous parameters
🔹 Valsalva Maneuver: Used to diagnose varicocele
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