Drainage or aspiration of fluid

This leaflet explains about the procedure to drain or aspirate fluid from the body, what it involves and what to expect when your child comes into the Interventional Radiology (IR) department at Great Ormond Street Hospital (GOSH) for treatment.

Fluid can build up inside the body for many reasons, for example because of infection. As the body is fighting off an infection, the white blood cells form fluid (pus). Pus is a liquid mixture of dead cells and exhausted white blood cells. It is usually a yellow or green colour. Pus can collect in the area of infection making your child feel unwell and in pain.

Sometimes other fluids can build up inside the body, for example, lymph fluid, which is part of the immune system. Fluid can build up in the abdomen or chest, putting pressure on the internal organs. Blood can collect inside the body following surgery, or as a result of trauma. The joints in the body can become swollen with excess fluid called synovial fluid which surrounds the bone surfaces reducing friction as the joint moves.

Small amounts of this fluid can be drawn off using a needle and syringe. This is called aspiration. Larger amounts or thicker liquid will need to be drained over a period of time using a thin plastic tube. This is called drainage.

Often drainage or aspiration happens while your child is still in the hospital. The doctors will explain the procedure in more detail, discuss any worries you may have and ask you to sign a consent form giving permission for your child to have the test. If your child has any medical problems, particularly allergies, please tell the doctors.

The person bringing your child to the procedure should have ‘parental responsibility’ for them. Parental responsibility refers to the individual who has legal rights, responsibilities, duties, power and authority to make decisions for a child. If the person bringing your child does not have parental responsibility, we may have to cancel the procedure.

An anaesthetist will visit you to talk about the anaesthetic including risks involved.

Many of the procedures we perform involve the use of X-rays. Legally, we are obliged to ask anyone over the age of 12 whether there is any chance they might be pregnant, and we will also ask for the first date of their last period (if started). This is to protect babies in the womb from receiving unnecessary radiation.

Aspiration

If only a small amount of fluid needs to be drained, the doctor may suggest that it is done while your child is awake. However, depending on the area to be drained and your child’s age, they may suggest a short general anaesthetic.

Drainage

If a larger amount of fluid needs to be removed or the fluid is too thick to be removed through aspiration, the doctor may suggest drainage instead. The drainage procedure is usually carried out while the child is under general anaesthetic.

You will already have received information about how to prepare your child for the procedure in your admission letter. You may need to come to GOSH before the procedure so that your child can have a pre-admission assessment to check that they are well enough. This appointment may involve taking blood samples and other tests.

This test can be performed under local or general anaesthetic, your admission letter will specify which type you need to prepare for. For local anaesthetic there is no fasting required. For general anaesthetic please follow the below instructions.

Your child needs to be fasted for the procedure for the general anaesthetic. If your child takes regular medication, please speak to your child’s team about when to stop these before the procedure.

As a general rule:

Food and milk:

Water:

It is equally important to keep giving your child food and drink until those times to ensure they remain well-hydrated and get adequate nutrition. This may involve waking your child in the night to give them a drink which we recommend.

Please follow these instructions carefully, otherwise your child’s procedure may be delayed or even cancelled.

Aspiration

The area to be drained will be numbed with local anaesthetic before a needle is inserted through the skin. The doctor will use an ultrasound scan to locate the correct place to insert the needle. The needle is then connected to a syringe to draw off a small sample of the fluid.

Drainage

Once your child is under general anaesthetic, the doctor will use a variety of imaging techniques, such as ultrasound or X-rays, to guide them. Occasionally, a CT scan will be needed. Some local anaesthetic will be injected into the skin first, to make the area numb for a few hours. Once the correct position has been confirmed, they will make a small incision (cut) through the skin and insert a thin plastic drainage tube. The free end of the tube is connected to a drainage bag to collect the fluid removed. The cut is closed around the tube with a small stitch to hold it in place and the area is covered with a large dressing.

If your child is having the procedure under general anaesthetic, every anaesthetic carries a risk, but this is extremely small.

Aspiration or drainage of fluid is unlikely to cause any problems with bleeding or infection. There is a small risk of bleeding when the small incision is made. Very occasionally, the structures near to the area of fluid collection can be damaged during the procedure, although using ultrasound to plan the position of the drainage tube reduces this risk greatly. There is a chance that the drainage tube could move or fall out, although the design of the tube is intended to minimise this risk.

The procedure may involve the use of X-rays. The levels that are used are low dose and therefore low risk. If you have any concerns regarding the use of radiation, please discuss this with the person performing your procedure beforehand.

This is usually the most effective way of removing excess fluid from the body so that it does not cause any further problems. Using drainage or aspiration speeds up the body’s natural processes of dealing with fluid collection. Sometimes the fluid may need to be removed in a surgical operation under general anaesthetic.

Your child will return to the ward after they have recovered from the general anaesthetic if they have had one. Some children feel sick and vomit after a general anaesthetic. Your child may have a headache or sore throat or feel dizzy, but these side effects are usually short-lived and not severe. Your child can start eating and drinking as normal once they feel like it.

The drainage bag will be changed, as needed, by the nurses on the ward. Occasionally, the drainage tube becomes blocked, but this can usually be cleared by flushing it with a saltwater solution (saline). The doctor may check the amount of fluid left in the body with an ultrasound scan or an X-ray. When most of the fluid has drained, the tube will be removed. This happens on the ward but is not painful. Your child may be offered a mixture of gas and air (Entonox) to deal with any discomfort. The nurses will cover the small incision with a dressing.

Your child will be able to go home once the tube has been removed and the area has been covered with a dressing. You should keep the dressing dry for the next two days.

You should call the hospital – or go to A&E out of hours – if:

• The area continues to drain a lot of fluid
• The dressing begins to smell
• The area looks red, swollen and feels hotter than the surrounding skin
• Your child is in a lot of pain and pain relief does not seem to help
• Your child has a temperature of 38 degrees or higher.

You can contact the ward by calling the GOSH switchboard on 020 7405 9200 and asking for the ward your child was discharged from.

Written by: Interventional Radiology

Reference number: 0226PAT0044

Last reviewed: February 2026

Next review due: February 2030