Objective To investigate the clinical guiding significance of lymphoscintigraphy with 99mTc-DX for radical lateral lymph node dissection with pelvic autonomic nerve preservation(PANP) in lower rectal cancer.Methods In 67 patients with pathologically proven lower rectal cancer,37MBq/0.8ml 99mTc-DX was injected into submucosa of the rectum through rectal endoscopy.At 0.5h,1h,2h,3h,4h,6h,12h,and 24h after the injection,the patients underwent pelvic and lower abdominal lymphoscintigraphy. The operative method was determined according to the imaging results,and the results of lymphoscintigrams were correlated with postoperative lateral node histologic examination.Results The scintigrams were postive in 37 cases,and all were unilateral.The positive patients underwent PANP.The image results were compared with histological lymph node examination in all patients operated upon for rectal cancer.Histologically,the cases in conformity were 26(70.3 %),false positive in 11 cases(29.7 %),and 2 of 30 false positive patients who demonstrated metastases to lateral node were operated by PANP,while the others underwent only PANP(type Ⅰ) without lateral lymph nodes dissection.The percentage of good sexual function of the two groups of cases after operation was 74.4 % and 71.4 % respentively.The percentages of mild dysuria and good function of urination were both 100 %.Conclusions Lymphoscintigraphy with 99mTC-DX has particular guiding significance in selection of PANP for lower rectal cancer.