Chyle

Chyle is a milky bodily fluid that forms in the small intestine during digestion and is a component of lymph. It consists largely of emulsified fats absorbed from the diet, along with lymph and other components of the lymphatic system. The milky appearance is due to a high content of chylomicrons, lipoprotein particles formed in enterocytes.

Formation and transport occur after dietary fats are broken down and reassembled into triglycerides within intestinal epithelial cells. These triglycerides are packaged into chylomicrons and released into the intestinal lacteals, the lymphatic vessels of the gut. Chyle then travels through the lymphatic system to the cisterna chyli, ascends via the thoracic duct, and drains into the venous circulation at the left subclavian vein.

Compositionally, chyle contains triglycerides, cholesterol, phospholipids, and proteins, as well as lymphocytes and other immune cells. It differs from ordinary lymph by its high lipid content and the presence of chylomicrons.

Clinical significance includes chyle leaks, which can occur due to trauma, surgical injury, or obstruction from malignancy. This can cause chylothorax (chyle in the pleural space) or chylous ascites (in the peritoneal cavity). Diagnostically, chylous effusions are typically milky and have elevated triglycerides (often above about 110 mg/dL) with detectable chylomicrons.

Management focuses on correcting the underlying cause and nutritional strategies, such as dietary modification with medium-chain triglycerides, which are absorbed directly into the portal vein, or total parenteral nutrition. In persistent cases, procedures to repair or bypass the thoracic duct may be considered.