Objective: To investigate the application value of CT lymphangiography in diagnosis and grading in patients with primary chyluria. Methods: Clinical and CTL imaging data of 79 patients diagnosed with primary chyluria were collected retrospectively. For CTL, the indexs were (1) Involved kidney and distribution of abnormal lymphatic vessels in the kidney: unilateral or bilateral kidney,renal sinus, renal parenchymal, suprahilar area and subhilar area; (2) Distribution of perirenal and retroperitoneal abnormal lymphatic vessels: retroperitoneal area,lumbar trunk area, renal perivascular area, fatty capsule area, adrenal area, etc; (3) Distribution of dilated lymphatic vessels and lymphatic reflux in chest, abdomen and pelvis; (4) Other abnormal manifestations: lymphatic-related abnormal changes in the chest, abdomen, pelvic cavity and bone; (5) Imaging grading: the imaging grading was carried out according to the range of retroperitoneal involvement, and the retroperitoneal area was divided into 10 areas, including left and right suprahilar area, subhilar area, perirenal area, renal perivascular area and lumbar trunk area, involvement of five or fewer areas were graded as mild, while involvement of six or more were graded as severe. In addition, clinical grading was carried out according to clinical manifestations. The clinical characteristics and CTL signs of patients with primary chyluria were statistically described by the composition ratio of classification variables, and the consistency of imaging grade and clinical grade of patients with primary chyluria was evaluated by Kappa test. Results: CTL showed abnormal lipiodol deposition in kidney in 74 cases (93.7%), unilateral kidney in 55 cases (69.6%), bilateral kidneys in 19 cases (24.1%), renal sinus in 74 cases (93.7%), renal parenchyma in 37 cases (46.8%); suprahilar area in 61 cases (77.2%), 52 cases (65.8%) were unilateral and 9 cases (11.4%) were bilateral; subhilar area in 61 cases (77.2%), 47 cases (59.5%) were unilateral and 14 cases (17.7%) were bilateral; retroperitoneal area in 78 cases (98.7%); lumbar trunk area in 76 cases (96.2%), 20 cases (25.3%) were unilateral and 56 cases (70.9%) were bilateral; perivascular area in 72 cases (91.1%), 45 cases (57.0%) were unilateral and 27 cases (34.2%) were bilateral; fatty capsule in 14 cases (17.7%), 13 cases (16.5%) were unilateral and 1 case (1.3%) was bilateral; adrenal area in 12 cases (15.2%); bladder in 31 cases (39.2%), perivesical area in 12 cases (15.2%), iliac perivascular area in 73 cases (92.4%), abdominal and pelvic wall in 14 cases (17.7%), perineal area in 12 cases (15.2%), perirectal area in 14 cases (17.7%), mesentery in 26 cases (32.9%), intestinal wall in 11 cases (13.9%), intestinal canal in 5 cases (6.3%), peripancreatic area in 15 cases (18.9%), perisplenic area in 2 cases (2.5%), perihepatic area in 7 cases (8.8%), hilus of the lung in 1 case (1.3%), mediastinum in 14 cases (17.7%), pericardium in 1 case (1.3%), extrapleural area in 25 cases (31.6%), chest wall in 2 cases (2.5%), skeleton in 2 cases (2.5%), end of thoracic duct in 70 cases (88.6%). Among the 79 patients with primary chyluria, according to clinical classification, 27 cases were mild and 52 cases were severe; according to imaging classification, 40 cases were mild and 39 cases were severe. The consistency of the two grades was moderate. Conclusion: CTL can evaluate the distribution and range of intrarenal, perirenal and retroperitoneal dilated lymphatic vessels accurately, and evaluate the abnormal lymphatic vessels in the chest, abdomen and pelvis and thoracic duct in patients with primary chyluria.It can provide image basis for the diagnosis, grading and treatment of primary chyluria.