Possible causes of one testicle being bigger than the other include epididymitis, epididymal cysts, a hydrocele, testicular torsion, and more. Treatment depends on the cause. Self-exams can help detect changes.

If a testicle changes size or shape, a person should contact their doctor as soon as possible. While some causes do not require treatment, it is important to receive an accurate diagnosis and advice on medications where necessary.

Read on to learn more about what can cause one testicle to be bigger than the other, the treatment options, and how to perform a self-exam.

Epididymitis occurs when the epididymis becomes inflamed. The epididymis is a duct behind the testes.

Epididymitis usually results from infection. This condition can be a sign of the sexually transmitted infections (STIs) chlamydia and gonorrhea.

It can cause symptoms such as:

  • pain when urinating
  • discharge from the penis
  • inflammation in the testicle

Treatments

A doctor may prescribe a course of antibiotics to treat the infection

They may also recommend elevating the scrotum to reduce swelling.

Orchitis happens when an infection causes inflammation in the testicle. It may occur after a person has the mumps virus.

If an individual experiences testicular pain and suspects that orchitis is the cause, they should contact a doctor. This condition can damage the testicles.

Treatments

If an STI is causing orchitis, a doctor will usually prescribe medication to address the infection. Common medications include ceftriaxone (Rocephin) and azithromycin (Zithromax).

Pain relief medication and an ice pack may help relieve pain and discomfort.

Epididymal cysts may occur when there is excess fluid in the duct. They may also form while the epididymis is developing.

These cysts are usually painless.

Treatments

In most cases, epididymal cysts do not require treatment.

If epididymal cysts cause discomfort, however, a doctor may recommend removing them surgically.

A hydrocele refers to a sac that forms around the testicles and fills with fluid. They are common in newborns.

Treatments

While it usually does not require treatment in newborns, it may be necessary to surgically remove a hydrocele if it does not go away or if it develops in older children or adults.

When the veins within the scrotum become enlarged, this is called a varicocele. The exact cause is unclear.

It usually does not require treatment if there are no additional symptoms, but a varicocele can cause a low sperm count.

Treatments

If the condition causes pain or discomfort, doctors may recommend analgesics or surgery for the treatment of varicocele.

Testicular torsion occurs when the testicle rotates and the spermatic cord is twisted.

This can cause severe and lasting testicular pain. If this pain follows an injury, it may subside then suddenly return.

Testicular torsion is a medical emergency. The twisting of the cord can reduce or block blood flow to the testicle, and without treatment it may be necessary to remove the testicle.

Treatments

Testicular torsion requires immediate treatment.

A doctor may be able to untwist the testicle, in a procedure called manual detorsion, but surgery is often necessary to prevent reoccurrence.

A delay in treatment increases the likelihood that the twisted testicle will require removal.

Cancerous cells can appear and multiply in the testicle. A doctor should investigate lumps or new growths in the area as soon as possible.

According to the American Cancer Society, testicular cancer is uncommon, developing in about 1 in 250 males. It is most prevalent in young and middle-aged people, and treatment is typically successful.

Treatments

A doctor may recommend removing the testicle where the cancer is present.

Radiation therapy, chemotherapy, or a combination may help to reduce or destroy cancer cells.

If the cancer has spread, or if it originated in another part of the body, additional treatments and surgeries may be necessary.

Several signs and symptoms can indicate an underlying problem with testicular health.

If any of the following symptoms occur with an enlarged testicle, seek medical attention as soon as possible:

  • a sharp pain or ache in or around the testicles
  • swelling of the testicles
  • redness or discoloration
  • discharge from the penis
  • trouble passing urine
  • pain in the back or lower abdomen

A doctor will help to identify the underlying cause by examining the scrotum and testicles for lumps or abnormalities. If they suspect testicular cancer, they will take a blood test and ask about family history.

Other tests a doctor may recommend include:

  • a urine test to check for infections and kidney problems
  • an ultrasound to look for growths and check blood flow
  • a CT scan to look for testicular abnormalities

It is very important to monitor the size and shape of testicles to detect any changes as early as possible.

Perform a self-examination at least once a month. Be on the lookout for lumps, growths, pain, swelling, and other changes.

Lumps or abnormal protrusions should be investigated by a doctor right away.

To perform a testicular self-exam:

  • Ensure that the scrotum is loose before beginning.
  • Carefully and slowly roll the testicle between the fingers and thumb.
  • Thoroughly check the surface of each testicle, looking for lumps, areas that feel tender or sore, protrusions, swelling, or changes in size.
  • Feel along the bottom of the scrotum, reaching the epididymis, which should feel like several grouped tubes.

One testicle can become larger than the other due to causes such as epididymitis, orchitis, a hydrocele, a varicocele, testicular torsion, and testicular cancer.

If other symptoms are present, such as pain, lumps, or swelling, seek medical attention right away. Depending on the cause, medical treatment may be necessary. Some causes, such as testicular torsion, are a medical emergency.