Scrotal ultrasound: torsion, epididymitis and masses
- Finding
Sound-wave scanning of the scrotum shows if the testicle has blood flow, if it is inflamed, or if a lump is inside or outside the testicle.
What it is
Scrotal ultrasound is the imaging test for scrotal pain, swelling and lumps. It uses a high-frequency linear probe with greyscale and colour Doppler, always comparing the painful side with the normal one. In acute pain it separates torsion (reduced or absent blood flow to the testis) from epididymitis or orchitis (increased flow). In a lump, the key question is whether it lies inside the testis, which is presumed malignant until proven otherwise, or outside it, where most masses are benign. Ultrasound must never delay surgery when torsion is clinically likely: testicular salvage falls steeply after about six hours.
What it looks like
- Torsion: absent or clearly reduced colour flow in the testis compared with the other side; the testis may be enlarged and darker or patchy if seen late.
- Whirlpool sign: the twisted spermatic cord seen as a spiral of tissue and vessels above the testis; it is the most specific sign of torsion.
- Epididymitis: a large, darker (hypoechoic) epididymis with increased colour flow; orchitis adds increased flow within the testis; a reactive hydrocele and thick scrotal wall are common.
- Torsion of the appendix testis: a small nodule without flow near the upper pole, with normal flow in the testis itself.
- Intratesticular solid mass: presume cancer; seminoma tends to be uniformly dark, non-seminomatous tumours more mixed with cysts or calcification.
- Extratesticular lesions are mostly benign: hydrocele (fluid around the testis), epididymal cyst or spermatocele, and varicocele (dilated veins that swell with Valsalva).
Why it looks that way
- Twisting the cord first blocks low-pressure venous outflow, then arterial inflow, so the testis swells and then loses flow; partial twists can still show some flow.
- Inflammation dilates vessels, so infection shows more Doppler flow than the normal side, the opposite of torsion.
Differential and pitfalls
- Normal-looking flow does not exclude torsion: partial or intermittent torsion can keep some flow; a high clinical suspicion still goes to surgery.
- Torsion peaks in adolescence and in newborns; epididymitis is more common in sexually active men and older men with urinary infection.
- Doppler settings must be set for slow flow, and the normal side scanned first, or low flow in a small prepubertal testis can be missed.
- Never biopsy a testicular mass through the scrotum; suspected cancer is removed through the groin (inguinal orchiectomy).
- After scrotal trauma, a break in the bright outer capsule (tunica albuginea) with irregular testis means rupture and needs surgery.
Next step
- Sudden severe testicular pain in a boy or young man: call urology at once; scan only if it does not delay surgery.
- Increased flow in epididymis or testis: treat as infection, test urine and for sexually transmitted infection, and re-examine if pain worsens.
- Solid mass inside the testis: tumour markers (AFP, beta-hCG, LDH) and urgent urology referral.
- Benign extratesticular finding: reassure; re-scan or refer if it grows, hurts or the report is uncertain.
Test yourself
Think of the answer, then tap the question to see it.
What Doppler finding separates torsion from epididymitis?
Torsion shows reduced or absent flow in the testis compared with the other side; epididymitis shows increased flow in the epididymis.
Does preserved flow on Doppler rule out testicular torsion?
No. Partial or intermittent torsion can keep some flow; if clinical suspicion is high, the patient still needs urgent surgical exploration.
What is the whirlpool sign?
The twisted spermatic cord seen as a spiral of tissue and vessels just above the testis; it is the most specific ultrasound sign of torsion.
Why is a solid lump inside the testis managed differently from one outside it?
Solid intratesticular masses are presumed malignant and need markers and urgent urology; extratesticular masses are usually benign cysts, fluid or veins.
Elsewhere in DurgiPedia
Connections
Educational content; it does not replace a radiologist's report and is not a clinical instruction. Each study is ordered on the patient's assessment and your institution's protocols.
Sources: Testicular Torsion (StatPearls (NCBI Bookshelf), 2023); Epididymitis (StatPearls (NCBI Bookshelf), 2023).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.