Pulmonary lymphatic vessels

It has been suggested that sharp fibres in the lungs penetrate the pulmonary pleura during respiration and pass directly into the parietal layer, possibly causing traumatic microhemarrhages and fibrin deposition (Heard and Williams 1961, Thomson 1970). Taskinen et al. (1973) discussed lymphogenic metastasis of dusts to the intercostal lymphatic vessels. 

At CXR, pulmonary congestion might be combined with infiltration. CT demonstrates a thickening of the lymphatic vessels, which corresponds to the well-known Kerley lines (Fig. 27.16). 

Hi-receptors mainly mediate the constriction of large and relaxation of small blood vessels, contractions of the bronchial, intestinal and uterine smooth muscle and contractions of vascular endothelial cells with the result of an increased capillary permeability. The lymphatic flow is augmented by Hi-receptor stimulation. H2-receptor stimulation induce a dilatation of pulmonary arteries, a positive inotropic and chronotropic effect on the heart and an increased glandular secretion, especially in the mucosa of the stomach. 

As in humans filariasis has high prevalence in domestic animals. The microfilariae live in the peritoneal blood and skin while the adult filariids reside in the blood vessels, lymphatic system, subcutaneous tissues and body cavities. In addition, the heartworm of the dog, Dirofilaria immitis, is found in the right ventricle and adjacent pulmonary arteries of carnivorous animals. 

The reactive pulmonary lymphoid lesions are a group of inflammatory processes of diverse etiology characterized by the accumulation of numerous lymphocytes (as well as other chronic inflammatory cells such as plasma cells) within the lung. Often the lymphoid aggregates appear with germinal centers and proliferate along lymphatic routes or vessels. These lesions must be distinguished from lymphomas. 

As noted above, LIP is part of a spectrum of pulmonary lymphoid proliferations, ranging from follicular bronchitis-bronchiolitis to low-grade malignant lymphoma, patterns which may be difficult to distinguish from each other (5). When reactive lymphoid nodules are centered in a lymphatic distribution about airways, vessels, and interlobular septa, the disease is termed follicular bronchitis/ bronchiolitis [or pulmonary lymphoid hyperplasia (PLH)] in the pediatric AIDS literature) (60). As the disease becomes more florid and the reactive lymphoid infiltrate extends into the lung interstitium, then the process is termed LIP (3). 

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