Perirectal injection of imaging materials for computed tomographic lymphography and near infrared fluorescent thoracoscopy in cats

摘要

For the treatment of chylothorax, the most common procedure is a thoracic duct ligation; however,recurrence of the issue is often common, generally due to the incomplete ligation of all thoracic duct tributaries.Therefore, accurate localisation of the thoracic duct tributaries is required to determine the ligation sites in eachpatient. The concept of the perirectal injection of the imaging materials, which provides a simple and minimallyinvasive approach, is investigated for computed tomographic (CT) lymphography and near infrared fluorescentthoracoscopy in cats. Three clinically healthy cats were used for the CT lymphography, and two clinically healthycats were used for the near infrared fluorescent thoracoscopy. Iodine contrast agent for the CT or indocyaninegreen for the thoracoscopy was injected subcutaneously into the peri-anal tissue. The injection site was massagedfor 5 min post-injection. However, in the indirect injection of the imaging materials, in three iohexol-administeredcats, the abdominal lymphatics, cisterna chyle, and thoracic duct could be depicted by the CT lymphography;and in both indocyanine green-administered cats, the thoracic duct was depicted running alongside the aortaby the near infrared fluorescent thoracoscopy. The ideal imaging procedure for the thoracic duct ligation involvesthe pre-operative CT lymphography of the entire pathway of the lymphatic vessels in advance, followed by the directvisualisation using a thoracoscopy. A combined CT lymphography and thoracoscopy could be a reliable methodfor successful surgeries. Crucially, the subcutaneous peri-anal injection of a contrast/dye provides a simple andminimally invasive method for the pre-operative and intra-operative depiction of the lymphatic pathways.