Most clinical pictures with a main “gravitational reflux” component are due to lymphatic and chyliferous vessel dysplasia, with wall-valvular and/or lymph node insufficiency. Sometimes, these diseases may be iatrogenic, for example due to the ligature of the thoracic duct or to lesions of retroperitoneal lymphatic and chyliferous vessels. These complex clinical conditions, that may present with chyloperitoneum, chyledema of the lower limbs or of external genitalia, chyluria, chylothorax, chylometrorrhea, chylous effusion in a joint, in various mutual associations, often require complex diagnostic and therapeutical processes.