Hydrocele
A hydrocele is fluid collection around the testicle causing painless scrotal swelling -- the most common cause of that presentation, affecting roughly 1% of adult men, per AAFP review.
Symptoms
Painless scrotal swelling that can range from barely noticeable to large and uncomfortable from sheer size; it typically doesn't hurt unless it's very large or rapidly enlarging.
Causes and risk
Most adult hydroceles are idiopathic (no clear cause); they can also follow infection, trauma, or testicular surgery.
How it is evaluated
Ultrasound is first-line to confirm the diagnosis and rule out an underlying testicular mass; transillumination (light passing through the fluid) is a supportive bedside finding, per ACR Appropriateness Criteria.
Treatment
Observation is reasonable for small, asymptomatic hydroceles. Surgery has a lower recurrence rate than aspiration or sclerotherapy, per a Cochrane review, and is generally preferred when treatment is needed.
When to seek care
Sudden pain with the swelling suggests torsion or a strangulated hernia rather than a simple hydrocele, and needs emergency evaluation within the torsion window of about 6 hours.