This information from Great Ormond Street Hospital (GOSH) is on chylothorax – a condition where fluid called chyle builds up in the pleural space. Chyle is a milky fluid that is made when the body digests fat.

The lungs and inside of the chest cavity have a smooth covering called the pleura that lets the lungs expand without rubbing on the inside of the chest. The two layers of pleura are usually in close contact with only a small space in between (pleural space) filled with a small amount of pleural fluid acting as lubrication.

Chyle is a milky fluid that is made when the body digests fat. It is absorbed by the intestines and drains into the lymphatic system. The lymphatic system forms part of the immune system that identifies and fights off invaders, such as bacteria and viruses. There is a network of vessels within the body through which lymph circulates. The lymph drains into the blood through the thoracic duct in the chest.

What causes chylothorax?

There are various causes of chylothorax. It can be present at birth or most commonly, it can occur after damage to the thorax, for example after an accident or following heart or thoracic surgery. The lymphatic thoracic duct may be damaged causing the fluid to leak into the surrounding area, collecting in the pleural space. 

What are the signs and symptoms of chylothorax?

The main sign of chylothorax is breathing difficulties, caused by the build-up of fluid in the pleural space. This stops the lungs inflating completely, causing increasing breathing difficulties. Children usually show symptoms of being generally unwell with a high temperature. They may find breathing harder than normal, struggling to catch a breath. Their heart rate may also be higher than usual. Some children may describe pain in their chest when breathing. 

How is chylothorax diagnosed?

If chylothorax is suspected, a chest x-ray may be the first test suggested to confirm or rule out the diagnosis. Chest x-rays will show white areas that suggest fluid. If fluid is located, it will be necessary to insert a chest drain. The fluid will be tested in the laboratory to identify its composition as chyle. Other imaging scans may be needed to identify the area of the lymphatic system affected.

How is chylothorax treated?

If there is a lot of chyle in the pleural space, it will need to be drained. Most children at GOSH have chest drains inserted under anaesthetic. Extra oxygen and fluids may be needed if they are having breathing problems. They will have regular analgesia while the chest drain is in place.

In addition to a chest drain, children will also need a special 'fat free' diet for a period of time up to two months and you will meet the Dietetic team. Your child may need medication to reduce the amount of chyle forming. Octreotide is one medication that may be suggested – this works by reducing the amount of chyle produced.

What happens next?

Children who have had chylothorax will need regular monitoring, not only to check that chyle is not building up again but also to make sure that the fat-free diet is not causing any problems. They will also need regular follow-up clinic appointments, usually involving a chest x-ray, to check that the pleura is healing properly without any problems. The outlook for children with a simple chylothorax and no underlying lung disease is usually good once it has been diagnosed and treated.

Compiled by: 
The Respiratory Medicine team in collaboration with the Child and Family Information Group
Last review date: 
January 2015