Scrotal Swelling: What Could Be Causing It

Why Scrotal Swelling Has So Many Possible Causes

The scrotum contains multiple anatomical structures, and pathology in any one of them can produce visible or palpable enlargement. Swelling may originate from the testicle itself, the epididymis, the spermatic cord, the tunica vaginalis, or even from abdominal contents descending through the inguinal canal.

A 2018 review in American Family Physician organized the differential into three practical categories: painful acute, painful subacute-to-chronic, and painless 1. Painful acute causes include testicular torsion and incarcerated inguinal hernia. Painful subacute presentations point toward epididymitis, orchitis, or trauma-related hematocele. Painless swelling is most often a hydrocele, varicocele, spermatocele, or, in a small but significant fraction, testicular neoplasm.

Age matters. In neonates and infants, communicating hydroceles and testicular torsion dominate. Adolescents and young adults are at peak risk for both torsion and germ cell tumors. Men over 40 develop epididymitis more frequently, often from urinary pathogens rather than sexually transmitted organisms 2. Understanding which diagnoses cluster in each age group narrows the workup quickly.

Hydrocele: The Most Common Painless Cause

A hydrocele is a collection of serous fluid between the visceral and parietal layers of the tunica vaginalis, and it is the single most frequent reason for painless scrotal enlargement in adult men. The swelling transilluminates on physical exam. It is smooth, nontender, and surrounds the testicle.

Hydroceles are classified as communicating or noncommunicating. Communicating hydroceles connect to the peritoneal cavity through a patent processus vaginalis; they fluctuate in size throughout the day and are most common in children under 2 years 3. Noncommunicating (or "adult") hydroceles arise from imbalanced fluid secretion and absorption within the tunica. Reactive hydroceles can form secondary to epididymitis, torsion, or tumor, so ultrasound should confirm a normal underlying testicle before the clinician reassures the patient.

Small, asymptomatic hydroceles require no treatment. Surgery (hydrocelectomy) is indicated when the hydrocele causes discomfort, interferes with daily activities, or reaches a size that makes testicular examination unreliable. Aspiration with sclerotherapy is an alternative in men who are poor surgical candidates, though recurrence rates are higher 4.

Varicocele: A Left-Sided Predominance

Varicoceles, defined as abnormal dilation of the pampiniform venous plexus, affect roughly 15% of the general male population and up to 35% to 40% of men evaluated for primary infertility 5. The left side is involved in about 80% to 90% of cases because the left gonadal vein drains into the left renal vein at a right angle, creating higher hydrostatic pressure.

On examination, a varicocele feels like a "bag of worms" superior and posterior to the testicle. It becomes more prominent with Valsalva and decompresses in the supine position. Grading follows the Dubin-Amelar system: Grade I is palpable only with Valsalva, Grade II is palpable at rest, and Grade III is visible through scrotal skin.

The American Urological Association and the American Society for Reproductive Medicine recommend varicocele repair when all three conditions are present: palpable varicocele, abnormal semen parameters, and an otherwise unexplained couple infertility lasting 12 months or more 6. A meta-analysis of 10 randomized controlled trials (N=894) found that varicocelectomy improved spontaneous pregnancy rates compared with observation (OR 2.39 to 95% CI 1.56 to 3.66) 7. Adolescents with varicocele and ipsilateral testicular hypotrophy of 2 mL or more also warrant surgical discussion.

An isolated right-sided varicocele in an older man, especially one that does not decompress when supine, should raise suspicion for retroperitoneal pathology compressing the gonadal vein. Abdominal imaging is appropriate in that scenario.

Epididymitis and Epididymo-Orchitis

Epididymitis is the most common cause of acute scrotal pain in adults, accounting for an estimated 600,000 outpatient visits annually in the United States 8. The epididymis becomes swollen, warm, and tender, typically starting posteriorly and sometimes spreading to involve the adjacent testicle (epididymo-orchitis).

In men under 35, the predominant pathogens are Chlamydia trachomatis and Neisseria gonorrhoeae. CDC sexually transmitted infection treatment guidelines (2021) recommend ceftriaxone 500 mg IM once plus doxycycline 100 mg orally twice daily for 10 days for this population 9. In men over 35 or those who practice insertive anal intercourse, enteric gram-negative organisms (especially E. coli) are more likely, and a fluoroquinolone such as levofloxacin 500 mg daily for 10 days is the recommended regimen.

Prehn sign (relief of pain with elevation of the affected testicle) has historically been taught as a way to distinguish epididymitis from torsion, but its sensitivity and specificity are too low for reliable clinical use 10. Color Doppler ultrasound showing increased blood flow to the epididymis confirms the diagnosis much more dependably. Supportive measures, including scrotal elevation, ice application, and NSAIDs, complement antibiotic therapy.

Testicular Torsion: The Time-Sensitive Emergency

Testicular torsion occurs when the spermatic cord twists on its axis, cutting off arterial inflow and venous drainage. The result is ischemia that progresses to infarction. This is a surgical emergency.

Testicular salvage rates depend directly on the duration of ischemia. Data from a retrospective series of 670 patients published in the Journal of Urology showed a salvage rate of approximately 90% when detorsion occurred within 6 hours, dropping to roughly 50% between 6 and 12 hours, and falling below 10% after 24 hours 11. Peak incidence falls in two age groups: neonates and boys aged 12 to 18.

The classic presentation is sudden, severe, unilateral scrotal pain that may radiate to the lower abdomen, accompanied by nausea or vomiting. The affected testicle often sits higher than normal (high-riding) and in a horizontal orientation ("bell-clapper" deformity). The cremasteric reflex is usually absent on the affected side. A systematic review found that absence of the cremasteric reflex had a sensitivity of 99% for torsion in pediatric patients 12.

Color Doppler ultrasound demonstrating absent or reduced intratesticular blood flow supports the diagnosis, but imaging should never delay surgical exploration when clinical suspicion is high. The definitive treatment is bilateral orchiopexy: the affected testicle is detorsed and fixed to the dartos fascia, and the contralateral testicle is fixed prophylactically because the bell-clapper anatomy is often bilateral.

Inguinal Hernia Presenting as Scrotal Swelling

An indirect inguinal hernia can extend through the external inguinal ring and descend into the scrotum, producing a scrotal mass that mimics primary scrotal pathology. The telltale finding is that the swelling increases with standing, coughing, or straining and can often be reduced back into the abdomen with gentle pressure while the patient is supine.

The lifetime risk of inguinal hernia is approximately 27% for men and 3% for women 13. Most inguinoscrotal hernias are indirect and follow the path of the processus vaginalis. In adults, elective surgical repair is recommended for symptomatic hernias to prevent incarceration or strangulation. An incarcerated hernia that cannot be reduced is a surgical emergency because bowel ischemia and perforation can follow within hours.

The distinction between a hernia and a hydrocele is usually straightforward on examination: hernias do not transilluminate (bowel content is opaque), they have a palpable impulse with cough, and their upper border cannot be "gotten above" on palpation. Ultrasound with dynamic maneuvers or CT of the abdomen and pelvis can resolve ambiguous cases.

Testicular Cancer: The Painless Mass That Demands Urgent Workup

Testicular cancer accounts for roughly 1% of all male malignancies but is the most common solid tumor in men aged 15 to 35. The American Cancer Society estimated 9,190 new cases and 470 deaths in the United States for 2023 14. The five-year survival exceeds 95% across all stages, largely due to the exquisite chemosensitivity of germ cell tumors.

The typical presentation is a painless, firm, nontender testicular mass that does not transilluminate. About 10% of patients present with acute pain due to intratumoral hemorrhage, which can mimic torsion or epididymitis 15. Risk factors include a history of cryptorchidism (3- to 8-fold increased risk), a contralateral or family history of testicular cancer, and Klinefelter syndrome.

Scrotal ultrasound is the initial study of choice and has a sensitivity above 95% for intratesticular lesions. Serum tumor markers (alpha-fetoprotein, beta-hCG, and LDH) should be drawn before any intervention. Radical inguinal orchiectomy is both diagnostic and therapeutic; trans-scrotal biopsy is contraindicated because it disrupts lymphatic drainage patterns and can upstage the disease. Staging CT of the chest, abdomen, and pelvis follows orchiectomy 16.

The European Association of Urology guidelines (2024) classify stage I seminoma management into three options after orchiectomy: active surveillance (preferred for most patients), single-agent carboplatin (AUC 7, one cycle), or adjuvant radiotherapy (20 Gy in 10 fractions to the para-aortic nodes) 17. Active surveillance detects relapse in about 15% to 20% of patients, nearly all of whom are cured with salvage treatment.

Less Common Causes Worth Knowing

Several additional conditions can produce scrotal swelling and occasionally generate diagnostic confusion.

Spermatocele. A cystic collection of spermatozoa-containing fluid arising from the head of the epididymis. Spermatoceles are almost always incidental findings, palpable as smooth, freely mobile, transilluminating masses distinct from the testicle. They rarely require surgery unless they grow large enough to cause discomfort 18.

Fournier gangrene. A necrotizing fasciitis of the perineum and scrotum. This is a life-threatening condition characterized by rapidly spreading erythema, crepitus, and systemic sepsis. Mortality ranges from 20% to 40% even with aggressive surgical debridement and broad-spectrum antibiotics 19. Risk factors include diabetes, immunosuppression, and perianal pathology.

Scrotal edema from systemic causes. Bilateral, pitting scrotal edema without a discrete mass suggests a systemic process: heart failure, nephrotic syndrome, or hepatic cirrhosis. The swelling is dependent, symmetric, and associated with lower-extremity edema. Treatment targets the underlying condition.

Henoch-Schönlein purpura (IgA vasculitis). In boys aged 2 to 11, this vasculitis can cause acute scrotal swelling and pain that mimics torsion. The presence of palpable purpura on the lower extremities, abdominal pain, and joint involvement points to the diagnosis and usually prevents unnecessary surgical exploration 20.

Diagnostic Approach: History, Exam, and Imaging

The evaluation of scrotal swelling begins with two questions that set the pace of the entire workup: Is the onset acute or gradual? Is the swelling painful or painless?

Acute pain plus swelling in a patient under 25 is testicular torsion until proven otherwise. The clinician should note the onset time (critical for salvage calculations), presence of nausea or vomiting, prior episodes of intermittent torsion-detorsion, and recent trauma. Gradual, painless swelling in an older adult shifts the differential toward hydrocele, varicocele, or hernia.

Physical examination should assess both sides, with the patient standing and supine. Key maneuvers include transillumination (positive in hydrocele and spermatocele, negative in solid masses and hernia), Valsalva (augments varicocele and hernia), and the cremasteric reflex (absent in torsion). The examiner should determine whether the mass is separate from the testicle (extratesticular, usually benign) or arises from within it (intratesticular, malignant until proven otherwise).

High-resolution scrotal ultrasound with color Doppler is the first-line imaging study. A meta-analysis in Radiology reported a pooled sensitivity of 97.3% and specificity of 99.8% for differentiating intratesticular from extratesticular lesions 21. Doppler flow assessment differentiates torsion (reduced or absent flow) from epididymitis (hyperemia). MRI is reserved for indeterminate ultrasound findings.

Laboratory tests are guided by clinical suspicion. Urinalysis and urine culture support epididymitis evaluation. Tumor markers (AFP, beta-hCG, LDH) are drawn when malignancy is a consideration. A CBC with differential and CRP may help quantify the infectious or inflammatory burden.

Treatment Principles by Diagnosis

Management depends entirely on the underlying cause. A quick reference:

Hydrocele. Observation for small, asymptomatic collections. Hydrocelectomy for symptomatic cases. Aspiration is a temporizing option.

Varicocele. Observation if fertility is not a concern. Microsurgical subinguinal varicocelectomy when fertility criteria are met, with a recurrence rate of approximately 1% to 2% 22.

Epididymitis. Empiric antibiotics based on likely pathogen profile (STI vs. enteric). Supportive care with scrotal support, ice, and analgesics. Follow-up imaging if symptoms persist beyond 3 weeks.

Testicular torsion. Emergency surgical exploration, detorsion, and bilateral orchiopexy. Orchiectomy if the testicle is nonviable.

Inguinal hernia. Elective surgical repair for symptomatic cases. Emergency surgery for incarceration or strangulation.

Testicular cancer. Radical inguinal orchiectomy followed by stage-directed adjuvant therapy or surveillance.