The cisterna chyli is an irregularly shaped chamber about 6½ cm (2½ in) long and about 2½ cm (1 in) wide, which lies on the rear wall of the abdominal cavity. The intestinal lymph trunk, which carries the lymph from the intestines, and the left and right lumbar trunks, which carry lymph from the lower limbs and the pelvis, lead into it. At its upper end the cisterna chyli narrows to form the lower end of the thoracic duct.