直肠病学

例句：

1. 1. The doctor performed a rectal exam to check for any abnormalities.
   医生进行了直肠检查，以检查任何异常。
2. 2.He was diagnosed with rectal cancer and required surgery.
   他被诊断出患有直肠癌，需要手术。
3. 3. The patient had difficulty defecating due to rectal bleeding.
   患者由于直肠出血而排便困难。