Schäfer A, Enck P, Fürst G, Kahn T, Frieling T, Lübke H J
Department of Gastroenterology, Heinrich Heine Universität, Düsseldorf, Germany.
Dis Colon Rectum. 1994 Aug;37(8):777-81. doi: 10.1007/BF02050142.
A recent application of endosonography in the evaluation of anal sphincter morphology has led to controversy about the possibility of precisely assessing the diameter of external and internal anal sphincter muscles. On the other hand, magnetic resonance imaging (MRI) has been proposed to allow a more detailed view of the anatomy of the pelvic floor. However, both techniques have not yet been compared directly.
Eight healthy volunteers (age range, 25-40 years; 5:3, male:female) participated. Anal ultrasound was performed using a 7.5-MHz rectal transducer which produced a transversal panorama display of 360 degrees, allowing an image perpendicular to the anal canal. Imaging of the diameter of the internal and external anal sphincter muscles was performed with the transducer placed in the midanal canal, and measurement was always performed by the same investigator in dorsal projection. MRI was performed using a 1.5 Tesla Magnetom (Siemens, Erlangen, Germany) to obtain sagittal and angled axial (perpendicular to the anal canal) planes for consecutive 3-mm slices which were evaluated by four independent raters.
Muscle thickness of the sphincter muscles in dorsal projection was 1.96 +/- 0.61 mm for the internal sphincter and 6.35 +/- 1.07 mm for the external sphincter using ultrasound. It was 1.72 +/- 0.13 mm and 3.99 +/- 0.99 mm, respectively, using MRI. When both measures were compared, only the internal sphincter data correlated significantly (r = 0.818, P = 0.0023) between both measures. Sagittal resonance imaging of the anal canal did not allow for differentiation of both muscles at all. Differentiation among mucosa, submucosa, and internal anal sphincter is not possible with MRI but may well be performed with high-resolution ultrasound.
Anal ultrasound carries the potential of becoming a routine clinical procedure for evaluation of the anal anatomy and morphology in defecation disorders, but current MRI assessment of the anal anatomy is elaborate, costly, and does not provide any further insights.
近期内镜超声在评估肛门括约肌形态方面的应用引发了关于能否精确评估肛门外括约肌和内括约肌直径的争议。另一方面，有人提出磁共振成像（MRI）可以更详细地观察盆底解剖结构。然而，这两种技术尚未直接进行比较。
八名健康志愿者（年龄范围25 - 40岁；男性5名，女性3名）参与研究。使用7.5兆赫的直肠探头进行肛门超声检查，该探头可产生360度的横向全景显示，从而获得垂直于肛管的图像。将探头置于肛管中部，对肛门内括约肌和外括约肌的直径进行成像，测量始终由同一名研究人员在背侧投影下进行。使用1.5特斯拉的Magnetom（西门子，德国埃尔朗根）进行MRI检查，以获取矢状面和倾斜的轴向（垂直于肛管）平面的连续3毫米切片，由四名独立评估人员进行评估。
使用超声检查时，背侧投影下内括约肌的肌肉厚度为1.96±0.61毫米，外括约肌为6.35±1.07毫米。使用MRI时，分别为1.72±0.13毫米和3.99±0.99毫米。当对两种测量方法进行比较时，只有内括约肌的数据在两种测量之间具有显著相关性（r = 0.818，P = 0.0023）。肛管的矢状面磁共振成像根本无法区分这两块肌肉。MRI无法区分黏膜、黏膜下层和肛门内括约肌，但高分辨率超声很可能可以做到。
肛门超声有潜力成为评估排便障碍中肛门解剖结构和形态的常规临床检查方法，但目前MRI对肛门解剖结构的评估复杂、昂贵，且无法提供更多有价值的信息。
