When should I worry about swollen testicles?

My right testicle swells when I stand up and becomes small when I lie down. Although I do not feel any pain, I am worried it may be cancer. Please advise. Paul

Dear Paul,
Cancer may manifest as a lump, the reason cancer is suspected when a person develops a swelling on any part of the body. However, in most cases, the swellings are not due to cancer. 

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The right side of the scrotum may swell because of what is referred to as an inguinal-scrotal hernia. A hernia here results from abdominal contents which are usually under pressure, given the limited space in the abdomen passing through (in case of men) the space left in the abdominal muscles by testes as they descend from the abdomen where they develop to the scrotum. Fortunately, the contents are held by the abdominal skin resulting in a groin bulge.

Any increase in abdominal pressure such as due to obesity, fluid in the abdomen, constipation and chronic cough risks men an inguinal scrotal hernia.

When one stands up, gravity increases pressure in the abdomen leading to appearance of the hernia, which temporarily disappears on lying down because of less effect of gravity on the abdominal contents to force them towards the groin.

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Also, some types of hydroceles (a type of swelling in the scrotum, the pouch of skin that holds the testicles) that connect with the abdomen may swell on standing and disappear when one lies down.
Visit your doctor, who may suggest surgery if the problem is a hernia or a hydrocele.