When lymphatic filariasis causes inflammation of the lymphatic vessels and thickens the walls of the vessels, the lymphatic vessels from the intestinal trunk to the thoracic duct are dilated, the valves in the vessels are not fully closed, resulting in a dynamic obstruction and a blockage of the lymphatic fluid, which increases the pressure in the lymphatic vessels and ruptures at the weakest point. The common site of rupture is at the fornix of the renal pelvis, and a pelvic-lymphatic fistula may result. Examination: 1. Leukocyte count and classification: In patients with early allergic reactions, total leukocyte count and eosinophils increase, with the former mostly between (10-20) × 109/L and the latter above 20%. 2.Discovery of blood microfilariae: The confirmation of filariasis depends on the discovery of microfilariae, usually by examination of peripheral blood, mostly from 10:00 pm to 2:00 am the next morning microfilariae are most easily found, if the blood exceeds 150 articles/60 μl at night, they can also be found during the day. (1) Fresh blood method: 20μl of earlobe blood is aspirated with a hemoglobinometer pipette and microfilariae are found under a low magnification microscope. Positive cases can be seen with microfilariae swinging freely, curling back and forth and quite active. (2) Smear method: Three big drops of blood from the earlobe (about equal to 60μl) are placed in the center of the slide and coated into a rectangular or oval thick blood film with even thickness and neat edges, about 2cm×3cm in size, since the 1980s, it is also unified to 120μl, that is, six big drops of double film method, staining can be used for magenta blue or borax methylene blue staining method, if there is difficulty in identifying the worm species, Jimsa or hematoxylin staining can be used. In the 1980s, the method was standardized to 120 μl, that is, six drops of double slices.