Swelling of the scrotum (the sac that surrounds and protects the testes) on one or both sides may be a symptom of a urinary tract disorder Overview of Urinary Tract Symptoms Kidney and urinary tract disorders can involve one or both kidneys, one or both ureters, the bladder, or the urethra, and in men, the prostate, one or both testes, or the epididymis. Problems... read more . Swelling can be small and detectable only by carefully feeling the scrotum, or it may be very large and easily visible. Some disorders that cause swelling of the scrotum also cause scrotal pain Scrotal Pain Pain in the scrotum (the sac that surrounds and protects the testes) can occur in males of any age, from newborns to older men. The testes are very sensitive, so even minor injuries may cause... read more .
Causes of Scrotal Swelling
Painless swelling of the scrotum can be caused by generally harmless conditions or can be a sign of cancer. There are several causes.
Common causes
The most common causes are
A collection of fluid in the scrotum (hydrocele)
Widening of the veins that carry blood from a testis (varicocele)
A hydrocele is a disorder in which fluid collects between layers of tissue that surround the testis. Hydrocele and inguinal hernia are the most common causes among boys. Up to 20% of men have a varicocele, which can cause infertility.
Less common causes
Less common causes include
A cyst in the epididymis (spermatocele)
A collection of blood in the scrotum (hematocele)
Accumulation of excess fluid in the body (edema)
Cancer of a testis
Cancer of a testis is the most concerning cause of painless scrotal swelling. Most often swelling does not turn out to be cancer. But cancer of a testis is the most common solid cancer in men younger than 40 years and it also can occur in younger and older men, so any testicular swelling or lump should be checked by a doctor.
Evaluation of Scrotal Swelling
The following information can help men know how quickly to see a doctor and what to expect during the evaluation.
Warning signs
In men with a lump in the scrotum, the most concerning signs are
A solid lump that is attached to or part of the testis
A balloon-like bulge that extends from the abdomen into the scrotum and cannot be pushed back
When to see a doctor
Men who have a balloon-like swelling that extends from the abdomen into the scrotum and cannot be pushed back could have an inguinal hernia that has become trapped (incarcerated). They should see a doctor right away. If a painless swelling suddenly becomes painful, men should also see a doctor right away because the cause may be an inguinal hernia that has become trapped and the blood supply shut off (strangulated hernia Inguinal Hernia An inguinal hernia is a protrusion of a piece of intestine or another abdominal organ through an opening in the abdominal wall in the groin. People have a bulge in the groin or scrotum, which... read more 
). Other men should see a doctor when an office appointment is available. A delay of a week or so is not harmful.
What the doctor does
Doctors first ask questions about the man's symptoms and then do a physical examination. What they find during the history and physical examination often suggests a cause of the swelling and the tests that may need to be done (see table Some Causes and Features of Scrotal Swelling Some Causes and Features of Scrotal Swelling 
).
Doctors ask how long the swelling has been present and whether there is any change in the swelling when the man stands up or lies down or when abdominal pressure increases (such as with coughing or straining to lift something). Doctors also ask about the man's medical history because disorders in other parts of the body (for example, edema related to heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more 
or liver failure Liver Failure Liver failure is severe deterioration in liver function. Liver failure is caused by a disorder or substance that damages the liver. Most people have jaundice (yellow skin and eyes), feel tired... read more ) may contribute to scrotal swelling.
The physical examination is done with the man standing and lying down. The doctor carefully feels the testis, epididymis, and spermatic cord to detect the exact location of the swelling or lump, and whether the swelling is tender. Sometimes the doctor shines a bright light behind the scrotum to see if light passes through (transillumination). Light can often pass through a collection of fluid (such as a hydrocele) but not through a solid lump (such as a cancer).
Testing
Sometimes the doctor can determine the cause of the swelling based on the symptoms and the results of the physical examination. If the symptoms and physical examination do not reveal the cause, testing is usually needed. Often the first test is ultrasonography. Ultrasonography is done when
Doctors are unsure of the diagnosis
Doctors detect a hydrocele during the examination (ultrasonography may show the source of the fluid)
Transillumination does not show fluid in the area of swelling
Depending on the results of ultrasonography, further testing may be done for cancer of a testis. Testing for testicular cancer includes blood tests and sometimes computed tomography (CT) of the abdomen, pelvis, and chest.
Treatment of Scrotal Swelling
The best way to treat scrotal swelling is to treat the cause of the swelling. Treatment is not always needed. Sometimes doctors try to reduce an inguinal hernia by pushing gently against the protruding intestine and forcing it back into place.
Key Points
Men and boys with scrotal swelling, even if it does not cause pain, should see a doctor.
Cancer of a testis is a concern in all boys and men, especially those who are younger than 40.
The diagnosis is usually evident from the symptoms, physical examination findings, and ultrasonography.
