A hydrocele (HI-dro-seel) is a collection of fluid around the testicle within the scrotum. More to Know Before a boy is born, his testicles develop in the abdomen and then travel through a tube into the scrotum. Normally, this tube then closes. When this tube doesn't close properly, fluid can leak into the scrotum. This results in a hydrocele. If the tube remains open (called a "communicating hydrocele"), fluid from the abdomen can travel up and down the open tube, making the hydrocele change size. If the opening in the tube is large enough, a hernia also can develop (when some of the intestines travel into the scrotum through the tube). When the tube closes, trapping the fluid in the scrotum, it creates a "non-communicating hydrocele." This type of hydrocele also can be caused by fluid that comes from the tissues around the testicle due to trauma, infections, or other causes. Hydroceles are common in newborn babies, especially premature babies, but can also happen in older boys and men. Keep in Mind Treatment depends on the type of hydrocele, the patient's age, and whether he has any symptoms (pain or discomfort). A hydrocele in a baby usually goes away by the first birthday. If it doesn't, or if the hydrocele develops after the first year of life or is associated with a hernia, surgery is often needed. This is a simple surgery and results are usually very good. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles Looking at Your Newborn: What's Normal When you first meet your newborn, you may be surprised by what you see. Here's what to expect. Read More Male Reproductive System What makes up a guy's reproductive system and how does it develop? Find the answers to these questions and more. Read More Male Reproductive System Understanding the male reproductive system and what it does can help you better understand your son's reproductive health. Read More Ultrasound: Scrotum Doctors order a scrotal ultrasound when they're concerned about symptoms such as scrotal pain or swelling. Read More Hernias Hernias are fairly common in kids, and hernia repair is one of the most common pediatric surgeries. Read More Hernias A hernia is an opening or weakness in the wall of a muscle, tissue, or membrane that normally holds an organ in place. Learning to prevent hernias isn't hard to do - check out these tips. Read More Undescended Testicles Shortly before birth, a boy's testicles usually descend into the scrotum. When a testicle doesn't make the move, this is called cryptorchidism, or undescended testicles. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.