出口梗阻型便秘（outlet obstructive constipation OOC）是慢性便秘最常见的原因，是影像诊断的难点，也是外科治疗的基础。目前认为X线排粪造影仍然是诊断OOC的金标准；核磁共振（MR）排粪造影存在检查费用高、非生理姿势排便的缺点，但有广阔的应用前景，未来可能作为慢性便秘的常规影像检查；超声检查较少应用于OOC疾病的诊断，确切作用尚待评价。

Imaging diagnosis of outlet obstructive constipation                   SHEN Hui, WANG Wei-xing, TIAN Bing, et al. Department of Medical Imaging, Changhai Hospital, the Second Military Medical University, Shanghai 200433, China
Corresponding author：HAO Qiang，E-mail: haoqiang@189.cn
Abstract    Outlet obstructive constipation (OOC) is the most popular reasons of chronic constipation, and also hardly diagnosed by imaging. Defecography is the major modality for constipation, and its images are still the evidence of surgery.  X-rays defecography is the gold standard for evaluating OOC. On the contrary, MR-defecography is expensive nowadays and has an unphysiological defecation way, but it will be an extensive examination and has broad prospects in the future. Ultrasound defecography is seldom applied for diagnosing OOC, and its exact role remains to be evaluated.