The anatomy and physiology of the terminal thoracic duct and ostial valve in health and disease: potential implications for intervention

The thoracic duct (TD) transports lymph drained from the body to the venous system in the neck via the lymphovenous junction. There has been increased interest in the TD lymph (including gut lymph) because of its putative role in the promotion of systemic inflammation and organ dysfunction during acute and critical illness. Minimally invasive TD cannulation has recently been described as a potential method to access TD lymph for investigation. However, marked anatomical variability exists in the terminal segment and the physiology regarding the ostial valve and terminal TD is poorly understood. A systematic review was conducted using three databases from 1909 until May 2017. Human and animal studies were included and data from surgical, radiological and cadaveric studies were retrieved. Sixty-three articles from the last 108 years were included in the analysis. The terminal TD exists as a single duct in its terminal course in 72% of cases and 13% have multiple terminations: double (8.5%), triple (1.8%) and quadruple (2.2%). The ostial valve functions to regulate flow in relation to the respiratory cycle. The patency of this valve found at the lymphovenous junction opening, is determined by venous wall tension. During inspiration, central venous pressure (CVP) falls and the valve cusps collapse to allow antegrade flow of lymph into the vein. During early expiration when CVP and venous wall tension rises, the ostial valve leaflets cover the opening of the lymphovenous junction preventing antegrade lymph flow. During chronic disease states associated with an elevated mean CVP (e.g. in heart failure or cirrhosis), there is a limitation of flow across the lymphovenous junction. Although lymph production is increased in both heart failure and cirrhosis, TD lymph outflow across the lymphovenous junction is unable to compensate for this increase. In conclusion the terminal TD shows marked anatomical variability and TD lymph flow is controlled at the ostial valve, which responds to changes in CVP. This information is relevant to techniques for cannulating the TD, with the aid of minimally invasive methods and high resolution ultrasonography, to enable longitudinal physiology and lymph composition studies in awake patients with both acute and chronic disease.

Visualização linfocintigráfica da desembocadura do ducto torácico

OBJETIVO: Avaliar a sensibilidade da linfocintigrafia intersticial na visualização da desembocadura do ducto torácico. MÉTODO: Foram analisados 535 exames linfocintigráficos realizados no Serviço de Medicina Nuclear do Hospital das Clínicas, Universidade Federal de Pernambuco (UFPE), no período de 1993 a 1999. Todas as linfocintigrafias foram realizadas através da injeção subcutânea, no primeiro espaço interdigital de cada pé, de 1 ml da solução de Dextran 500 marcado com Tecnécio-99 metaestável. RESULTADOS: A desembocadura do ducto torácico foi visualizada em 424 pacientes, que representam 79,3% das linfocintigrafias realizadas. Na avaliação por sexo, a desembocadura do ducto torácico foi visualizada em 191 pacientes do sexo feminino, representando 77% dos casos. Nos pacientes do sexo masculino, a desembocadura foi visualizada em 233 casos (80,9%). CONCLUSÃO: O presente estudo confirma a importância da linfocintigrafia como método de escolha na avaliação da circulação linfática e demonstra que esse exame apresenta uma alta sensibilidade para a visualização da desembocadura do ducto torácico.

Lymphatics of the diaphragm in the dog

Lymphography of the diaphragm was performed in 35 dogs. A main diaphragmatic duct passed in a postero-anterior direction, receiving several branches from the diaphragm. It passed to a double mammary internal channel ending at the upper end of the sternum, where a group of nodes were constantly present, and beyond this a lymphatic plexus was filled.