Objective  To analyze the characteristics of 360° intrarectal ultrasound images of rare rectal tumors to improve diagnostic accuracy.

  Methods  Twelve patients with rare rectal tumors who underwent 360° intrarectal ultrasound examination or surgical treatment at Shaanxi Provincial People’s Hospital from September 2012 to September 2018 were continuously included in this study. Ultrasound and pathological results were retrospectively analyzed to find out the characteristic manifestations of the lesions.

  Results  A total of 16 lesions were detected in 14 cases. The diagnostic coincidence of preoperative ultrasonography was 57.1% in 8 cases. The accurate staging rate was 78.5%, including 4 cases of rectal neuroendocrine tumors (28.6%), out of which 3 cases (75.0%) were accurately staged. Out of 3 cases (21.4%) of rectal and anal canal melanoma, 2 cases (66.6%) were accurately staged. All 6 cases (42.9%) of rectal stromal tumors were accurately staged (100.0%). One case (7.0%) of rectal lymphoma was misdiagnosed as rectal cancer using ultrasound. Thirteen patients underwent surgical treatment, and one received chemotherapy.

  Conclusions  There are many types of rare tumors in the rectal and anal canal. 360° intrarectal ultrasound is of great value in the clinical diagnosis and preoperative staging of rare tumors in the rectal and anal canal.