人坐骨肛管横隔CT的解剖学特点

目的　探讨坐骨肛管横隔的CT表现。 　方法　回顾性分析172例非肛区疾患就诊者盆部CT图像，行1．5 mm薄层重建，利用多平面重建技术，在合适的窗技术下观察坐骨肛管横隔及其邻近脂肪组织的CT表现。 　结果　坐骨肛管横隔上方脂肪组织密度低于下方，两者间CT值差异具有统计学意义（P<0．05）。与女性比较，男性的下方肛管皮下间隙脂肪组织密度更高，导致上、下方脂肪组织密度差异肉眼可辨识的比例（88．37%）高于女性（38．37%），该性别间差异均具有统计学意义（P<0．05）。坐骨肛管横隔CT直接显影率约23．26%，呈较对称线型全程、线型部分或分枝型软组织密度影，由肛门外括约肌皮下部和浅部之间发出，走向坐骨结节。统计直接显影者的最大厚径，左、右侧均值分别为（2．50±0．46）mm、（2．89±0．78）mm，其中男性与女性双侧厚度均值分别为（2．71±0．43）mm、（2．69±0．44）mm。 　结论　依据CT图像上坐骨肛管横隔上方坐骨直肠间隙与下方肛区皮下间隙脂肪密度差异，可以判定其位置，部分人可在CT上直接显影。

Multislice spiral CT imaging anatomical study of the Milligan’s septum

Objective　To study the CT manifestations of Milligan’s septum(MS). 　Methods　The pelvic CT images of 172 patients with non-anal disorders were retrospectively analyzed, based on the 1.5 mm thin-slice reconstruction. The CT manifestations of their MS and adjacent fat tissue were observed using multiplanar reconstruction and appropriate window technique. 　Results　The density of upper fat tissue adjacent to MS was lower than that of lower fat tissue, and the difference in CT values between them was statistically significant (P<0.05). Compared with females, the density of fat tissue in the lower anal subcutaneous space was much higher in males (38．37% vs 88．37%), even to the extent that the difference between upper and lower fat tissues could be visually identified; the difference between genders was a statistically significant (P<0.05). The CT direct visualization rate of MS was about 23．26%; the soft tissue density shadows, which could be divided into the relatively symmetrically whole－course linear type, partially linear type and branched type, started from the junction of the subcutaneous and superficial parts of external anal sphincter and travelled to the ischial tuberosity. According to the statistical result of the maximum thickness collected from those showing direct visualization, the average values of left and right sides were（2.50±0.46）mm and（2.89±0.78）mm, and the average values of both sides in males and females were（2.71±0.43）mm and（2.69 ±0.44）mm, respectively. 　Conclusion　Milligan’s septum can be located according to the density difference between the fat tissues in the upper ischiorectal space and the lower anal subcutaneous space, while it can also be directly visualized on CT images in some cases.