Scrotal Swelling: Causes and When It Is an Emergency

Start with pain: painful vs painless swelling

Whether the swelling hurts, and how fast it appeared, is the most useful first clue.

Emergency causes

Testicular torsion

Testicular torsion happens when the testicle twists on its cord, cutting off its blood supply. It is most common between ages 12 and 18 but can occur at any age, including newborns. Pain is sudden, severe and often wakes the person; nausea and vomiting are common, and the testicle may lie high and horizontally. Surgery within about 6 hours usually saves the testicle. Do not wait to see if it settles.

Strangulated inguinal hernia

An inguinal hernia is a loop of bowel or fat pushing through the groin into the scrotum. Usually painless and reducible, it becomes an emergency if it becomes tense, tender and stuck, especially with vomiting.

Fournier gangrene

A rare, rapidly spreading flesh-eating infection of the genitals and perineum, mainly in people with diabetes. Severe pain, swelling, dusky skin and fever need emergency surgery.

Common non-emergency causes

• Epididymitis: infection of the coiled tube behind the testicle. Pain and swelling build over a day or two, often with burning urination. In men under 35 it is commonly caused by chlamydia or gonorrhea; in older men by urinary bacteria.
• Orchitis: infection of the testicle itself, often with epididymitis or with mumps.
• Hydrocele: fluid around the testicle, causing a smooth, painless swelling that glows when a light is shone through it. Common in newborns and older men.
• Varicocele: enlarged veins above the testicle, usually on the left, feeling like a "bag of worms," more obvious when standing. Can cause dull aching and affect fertility.
• Epididymal cyst or spermatocele: a smooth, painless lump above and behind the testicle, separate from it.
• Scrotal edema: both sides swollen from fluid retention, as with heart failure, liver or kidney disease, after surgery, or with prolonged immobility.
• Skin causes: cellulitis, insect bites, allergic reactions and idiopathic scrotal edema in boys (painless red swelling that settles in a few days).

Testicular cancer

Testicular cancer is the most common cancer in men aged 15 to 35. It usually feels like a painless lump or hardness on the front or side of a testicle, or a testicle that becomes larger or heavier. A dull ache in the lower belly or groin may occur. It is highly curable, even when it has spread, so a painless testicular lump should be examined within 2 weeks.

How doctors diagnose scrotal swelling

• History: onset, pain, fever, urinary symptoms, sexual history, injury, mumps.
• Examination: position and feel of each testicle, whether the lump is separate from the testicle, transillumination with a light, the cremasteric reflex (absent in torsion), checking for a hernia while standing and coughing.
• Scrotal ultrasound with Doppler: the key test. It shows blood flow (reduced in torsion), fluid, cysts, varicoceles and solid masses.
• Urine tests and STI testing for infection.
• Tumor marker blood tests (AFP, hCG, LDH) if cancer is suspected.

If torsion is likely, surgeons may operate without waiting for an ultrasound.

Treatment and home care

Treatment depends on the cause; details are on our page about scrotal swelling as a condition. While you wait to be seen for a non-emergency cause:

• wear supportive underwear or an athletic supporter
• use ice packs wrapped in a cloth for 15 to 20 minutes at a time
• take acetaminophen (paracetamol) or ibuprofen for pain, following the label dose
• rest with the scrotum raised on a folded towel
• avoid sex until an infection has been ruled out or treated

Frequently asked questions

What causes a swollen scrotum?

Common causes include epididymitis (infection), hydrocele (fluid), varicocele (enlarged veins), inguinal hernia, epididymal cysts and fluid retention. Emergency causes include testicular torsion, strangulated hernia and injury. A firm lump on the testicle may be testicular cancer.

Is a swollen scrotum with no pain serious?

Usually it is a hydrocele, varicocele, cyst or hernia, which are not dangerous. But a painless firm lump on the testicle itself can be testicular cancer, which is very treatable when caught early. Any new painless swelling should be checked by a doctor within 2 weeks.

What does it mean if one testicle is swollen?

One-sided swelling may be epididymitis, a hydrocele, a hernia, a cyst, a varicocele, or less commonly a tumor. If it came on suddenly with severe pain, it may be testicular torsion and needs emergency care. Gradual painful swelling with fever suggests infection.

When is scrotal swelling an emergency?

Go to the ER for sudden severe testicular pain and swelling, swelling with vomiting, a tender groin bulge that will not go back in, rapidly spreading redness or dark skin with fever, or swelling after a significant injury. Testicular torsion needs surgery within hours to save the testicle.

Can an STI cause scrotal swelling?

Yes. In sexually active men under 35, epididymitis is often caused by chlamydia or gonorrhea, causing painful swelling, sometimes with discharge or burning when peeing. Both partners need testing and treatment with antibiotics.