Scrotal Pathology on Ultrasound: Orchitis, Varicocele, Hydrocele, and Epididymitis

Scrotal ultrasound is one of the most common emergency and outpatient studies sonographers perform. Beyond normal measurements (covered in a separate article), you need to recognize the major pathologies quickly and accurately. Here are the ones you'll see most often.

Epididymitis and Epididymo-Orchitis

Epididymitis (inflammation of the epididymis) is the most common cause of acute scrotal pain in adults. It's usually infectious (STI in young men, E. coli/gram-negative in older men with urinary tract pathology).

Sonographic Findings

Epididymis:

• Enlarged epididymis — particularly the head (epididymal head normally < 12 mm)
• Heterogeneous, decreased echogenicity (edema)
• Hyperemia on color Doppler — increased vascularity compared to the contralateral side
• This is the most sensitive finding: marked hyperemia of the epididymis

Testis (if orchitis has developed):

• Testicular enlargement
• Decreased echogenicity (edema)
• Markedly increased testicular blood flow — the testis is hypervascular
• Compare both testes on Doppler at the same scale setting

Reactive hydrocele: Small amount of fluid around the testis is a common accompaniment.

Scrotal wall thickening: In severe cases, the scrotal skin and dartos muscle are thickened.

Orchitis Alone

Isolated orchitis (without epididymitis) is less common. Viral orchitis (mumps) is the classic cause — often bilateral, the testis is diffusely enlarged and heterogeneous with increased flow.

Distinguishing Epididymo-Orchitis from Torsion

This is the critical clinical question — both present with acute scrotal pain.

Feature	Epididymo-orchitis	Torsion
Onset	Gradual (hours–days)	Sudden
Doppler flow	Increased (hypervascular)	Absent or markedly decreased
Epididymis	Enlarged, hyperemic	May be enlarged, flow variable
Fever	Common	Less common
Urinalysis	Often abnormal	Usually normal

The key Doppler finding in torsion is absent or markedly reduced testicular flow. But — as with ovarian torsion — some flow can persist in incomplete or early torsion. Always correlate clinically.

Testicular Torsion

Testicular torsion is the surgical emergency of scrotal ultrasound. The spermatic cord twists, cutting off blood supply. Salvage rates: > 90% if detorsed within 6 hours, < 10% after 24 hours.

Sonographic findings:

• Absent or markedly decreased testicular blood flow on color and power Doppler — this is the key finding
• Enlarged testis (early)
• Heterogeneous testis (late — indicates infarction)
• Whirlpool sign of the spermatic cord (twisted cord adjacent to the testis)
• High position of the testis or horizontal lie
• Reactive hydrocele

Intermittent torsion: The testis may have some Doppler flow if there has been spontaneous partial detorsion. The clinical history (severe sudden pain that may have partially improved) is critical context.

If in doubt — call the radiologist immediately. Do not delay for a "better" study.

Hydrocele

A hydrocele is a collection of serous fluid between the two layers of the tunica vaginalis surrounding the testis.

Sonographic appearance:

• Anechoic fluid surrounding the testis (usually anterolateral)
• Simple hydrocele: completely anechoic, no internal debris
• Complex hydrocele: internal echoes, septations (suggests inflammation, trauma, or tumor)
• Usually incidental; small hydroceles are common

Measure: Document the size (largest AP dimension or three dimensions).

Congenital hydrocele: Communicating hydrocele in infants — connects with peritoneal fluid through a patent processus vaginalis. May change size (larger when infant cries, smaller at rest).

Varicocele

A varicocele is abnormal dilatation of the pampiniform venous plexus of the spermatic cord. Most common on the left (90%) because the left gonadal vein drains at a right angle into the left renal vein (higher resistance than the right, which drains obliquely into the IVC).

Sonographic appearance:

• Multiple serpentine, tubular anechoic structures in the pampiniform plexus, superior and posterior to the testis
• Diagnostic diameter: ≥ 3 mm at rest (some use ≥ 2.5 mm)
• Valsalva: Veins dilate and flow reverses on Doppler — reflux is confirmed
• The varicocele enlarges (sometimes dramatically) with Valsalva

Clinical significance:

• Most common correctable cause of male infertility
• Associated with mild testicular hypotrophy on the affected side (compare both testicular volumes)
• Grade 1: Visible only on Valsalva; Grade 2: Palpable; Grade 3: Visible on inspection

Measure the largest vein in the pampiniform plexus in the supine position at rest and during Valsalva.

Bilateral varicocele or right-sided varicocele: May suggest a secondary cause (retroperitoneal mass obstructing the gonadal vein — renal cell carcinoma is the classic concern). Evaluate the kidneys.

Spermatocele and Epididymal Cyst

Spermatocele: Cystic dilation of the epididymal tubules containing spermatozoa. Located in the epididymal head (supratesticular).

Epididymal cyst: Similar but does not contain sperm — usually indistinguishable sonographically.

Appearance:

• Anechoic, well-defined cyst in the epididymal head
• May contain fine internal echoes (spermatocele — dead spermatozoa)
• Usually small and incidental; can be large
• Benign — no intervention needed unless symptomatic

Document: Size, location (head/body/tail of epididymis), internal contents.

Testicular Microlithiasis

Testicular microlithiasis (TM) is defined as ≥ 5 echogenic foci per transducer field per testis, without posterior shadowing.

Sonographic appearance:

• Tiny (1–3 mm) punctate echogenic foci scattered throughout the testicular parenchyma
• No posterior shadowing (distinguishes from macrocalcifications)
• May be unilateral or bilateral

Clinical significance: Formerly thought to significantly increase testicular cancer risk — current evidence suggests the risk elevation is modest when TM is an isolated finding in a low-risk patient. The current recommendation varies by society, but most guidelines suggest annual self-examination and clinical follow-up rather than routine annual ultrasound for isolated TM in average-risk patients.

Document: Presence, bilateral or unilateral, associated findings (atrophy, mass).

Reporting Template

For each testis document:

• Size (length × width × height)
• Echogenicity (homogeneous / heterogeneous)
• Doppler vascularity (symmetric / increased / decreased / absent)
• Epididymis: head, body, tail size and echogenicity
• Any focal lesion: size, echogenicity, vascularity, location
• Extratesticular: hydrocele, varicocele, spermatocele

Urgent language for torsion: "Absent Doppler flow identified within the right testis with preserved flow in the left. Right testis is enlarged and heterogeneous. Findings are highly suspicious for right testicular torsion. Immediate urological consultation recommended."

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SonoBuddy's testicular normal values are in the Measurements section. Scrotal pathologies including torsion and epididymo-orchitis are in the Pathologies section.