Inside the tummy (abdomen), there is a membrane called the peritoneum. It has two layers. One layer lines the tummy wall and the other layer covers the organs inside the abdominal cavity. The peritoneum produces a fluid that acts as a lubricant and allows the organs to glide smoothly over one another. Sometimes too much fluid can build up between the two layers, and this is called ascites.

Ascites is a symptom of many types of cancer. It can also be caused by some other conditions, such as advanced liver disease and heart failure.

The types of cancer that are more likely to cause ascites are cancers of the breast, lung, large bowel (colon), stomach, pancreas, ovary, womb (endometrium) and the peritoneum.

There may be several reasons for ascites:

• If cancer cells have spread to the lining of the tummy, they can irritate it and cause fluid to build up.
• If the liver is affected by cancer cells, this may block the circulation of blood through the liver. This can lead to a build-up of fluid in the tummy.
• If the liver is damaged, it may produce less blood protein. This may upset the body's fluid balance, which causes fluid to build up in the body tissues, including the tummy.
• Cancer cells can block the lymphatic system. This is a network of fine channels that run throughout the body. The lymphatic system drains off excess fluid from the body. If some of the lymphatic channels are blocked, fluid can build up.

The main symptom of ascites is a swollen tummy. Other symptoms include:

• pain and discomfort in the tummy
• feeling sick (nausea)
• reduced appetite
• indigestion
• feeling full
• tiredness
• feeling breathless

Ascites can make it difficult for you to get comfortable, sit up or walk.

The main treatment of ascites is to drain the fluid by putting a tube into the tummy. This is called paracentesis. Draining the fluid will relieve the symptoms and help you feel more comfortable.

A doctor will usually put in the tube at the hospital. Sometimes they use an ultrasound scan to help them position the tube.

Once you are lying down comfortably, the doctor will clean the skin on your tummy. They will give you an injection of local anaesthetic to numb the area.

They will make a small cut in the skin of your tummy and insert a thin tube. The fluid drains out of your tummy and collects in a drainage bag. The tube is covered with a dressing. Sometimes, the doctor may use a couple of stitches to hold it in place.

How long the tube needs to stay in place depends on how much fluid needs to be drained. While the tube is in place, a nurse will check how much fluid is draining. If there is just a small amount of fluid, you may have it drained off in an outpatient clinic. If there is a large amount of fluid, you may need to have a short stay in hospital. The drain may stay in place for up to 24 hours, but sometimes it may stay in longer.

Fluid can build up again, so you may need to have it drained more than once.

If the fluid builds up again quickly, your doctor may insert a tube called a catheter into your tummy. The catheter can stay in place for several months. When the fluid builds up, a drainage bottle is attached to the catheter and drains fluid from your tummy. The catheter is covered by a dressing when it is not being used. Your doctor or nurse can tell you more about this and show you how to look after it.

Usually the fluid will be drained off slowly. Your blood pressure may drop if it is drained off too quickly. A litre of fluid may be drained safely as soon as the drain has been inserted. After this, it will usually be done more slowly. Your nurse will check your blood pressure as the fluid drains.

The tube can become blocked. Changing your position or sitting upright may help clear it but sometimes the tube may need to be replaced.

The drain can sometimes become infected. Your temperature will be checked regularly, as a high temperature can be a sign of infection.

Once the drain is removed, there may be a bit of leakage from the drain site until the hole heals. The hole is stitched together and you will have a dressing or drainage bag over the area until the leakage has stopped. Usually the stitches are taken out after about a week. Your doctor and nurse will be able to tell you more about this.

Drug treatments

The doctor may give you a water tablet (diuretic) called spironolactone (Aldactone^®). It can help to slow down the build-up of the ascitic fluid. It usually makes you want to pass more urine than normal. You may have blood tests to check how well your kidneys are working during this treatment.

Placing an internal tube (shunt)

Occasionally a tube called a shunt may be used. This is a plastic or silicone rubber tube that is placed into your tummy. It drains the ascitic fluid directly into a large vein. Doctors call this a peritoneo-venous shunt.

The shunt is placed during an operation and you usually need a general anaesthetic. You will need a short stay in hospital while the hospital staff check that the shunt is working properly. The shunt stays in permanently. Your doctor and nurse will be able to give you more information about this.