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Anatomy of the anal canal and perianal structures as defined by phased-array magnetic resonance imaging
Department of General Surgery, University of Maastricht, Maastricht, The Netherlands.
Department of Radiology, University of Maastricht, Maastricht, The Netherlands.
Department of Radiology, University of Maastricht, Maastricht, The Netherlands.
2001 (English)In: British Journal of Surgery, ISSN 0007-1323, E-ISSN 1365-2168, Vol. 88, no 11, 1506-1512 p.Article in journal (Refereed) Published
Abstract [en]

Background:

The anatomy of the anal canal and perianal structures has been imaged using endoluminal magnetic resonance imaging (MRI). Phased-array MRI avoids the use of an endoluminal coil that may distort anatomy. The aim of this study was to describe the anatomy of the anal canal and perianal structures using phased-array MRI.

Methods:

Imaging was performed in 14 men and 19 nulliparous women. The dimensions of the anal canal, puborectalis, external anal sphincter, perineal body, superficial transverse perineal muscle, bulbospongiosus, ischiocavernosus and anococcygeal body were measured in different planes, and sex differences were calculated.

Results:

The lateral canal was significantly longer than its anterior and posterior part (P < 0·001). The anterior external anal sphincter was shorter in women than in men (P = 0·01) and occupied, respectively, 30 and 38 per cent of the anal canal length (P = 0·001). The caudal ends of the external anal sphincter formed a double layer. The perineal body was thicker in women than in men (P < 0·001) and easier to define. The superficial transverse muscles had a lateral and caudal extension to the ischiopubic bones. The bulbospongiosus was thicker in men than in women (P < 0·001). The ischiocavernosus and anococcygeal body had the same dimensions in both sexes.

Conclusion:

Phased-array MRI is a non-invasive technique that allows an accurate description of the normal anatomy of the anal canal and perianal structures.

Place, publisher, year, edition, pages
2001. Vol. 88, no 11, 1506-1512 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-81477DOI: 10.1046/j.0007-1323.2001.01919.xOAI: oai:DiVA.org:liu-81477DiVA: diva2:552858
Available from: 2012-09-17 Created: 2012-09-17 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Anatomical and physiological aspects of anorectal dysfunction
Open this publication in new window or tab >>Anatomical and physiological aspects of anorectal dysfunction
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Objective: To analyse the results of anal-sphincter repair; to examine the feasibility of motor latency measurements of the anal sphincter after magnetic sacral stimulation in healthy subjects, patients with a spinal cord injury and patients with faecal incontinence, using a new recording technique; to study, in the same 3 groups, the effects ofphasic magnetic sacral root stimulation on the anal sphincter and rectum; to describe normal, undisturbed anatomy of the anal canal and perianal structures in both men and nulliparous women using high-resolution phased array magnetic resonance imaging; to study pelvic floor movements in healthy volunteers of both sexes using a new instrument.

Methods: Latencies were recorded with an intraanal, bipolar sponge electrode and an intrarectal ground electrode. Rectal volume changes were measured with a barostat. Highresolution magnetic resonance images were obtained without an endoanal coil. Pelvic floor movements where measured with the subject seated, using a magnet attached to a rectal balloon.

Results: After a median period of 40 months, 31/55 female patients rated the result of analsphincter repair as excellent or good. Age>50 years, and post-operative urgency and loose stools were associated with poor outcome. Eight patients became fully continent for stool. 17% of the latency measurements failed. There were no significant differences between leftand right-sided stimulation. Faecal incontinence patients had prolonged pudendal nerve terminal motor latencies and prolonged latencies after left-sided magnetic stimulation. Phasic magnetic stimulation increased anal pressure in 100% of the 14 healthy subjects, 86% of the 14 spinal cord injury patients and 73% of the 18 faecal incontinence patients. A decrease in rectal volume was provoked in respectively 72 %, 79 % and 50 %. In all 33 volunteers, anal and perianal structures could be well defined by magnetic resonance imaging. The mid-anal canal was significantly longer than its anterior and posterior part. The female anterior sphincter was shorter than the male and occupied 30 % of the anal canal length. The female perineal body was thicker and easier to define than the male. The median pelvic floor lift and descent measured in 28 healthy volunteers, were 2 cm and 1.8 cm respectively. Day-to-day and inter-observer reproducibility were good. 20/28 subjects were able to expel the rectal balloon.

Conclusions: Anal-sphincter repair does not restore complete continence but leads to a satisfactory result in more than half of the patients. Additional bowel symptoms are common at follow-up. Latency measurements after magnetic stimulation are minimally invasive and have a low failure rate. They may be used to test the integrity of the distal motor pathway in patients who may benefit from continuous sacral root stimulation. Magnetic sacral root stimulation produces an increase in anal and rectal pressure and a decrease in rectal volume. Phased array magnetic resonance imaging is non-invasive and allows an accurate description of the normal anatomy of the anal canal and perianal structures. The new developed instrument measures cranial and caudal movement of the pelvic floor with minimal discomfort and good reproducibility.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2002. 96 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 721
Keyword
Anal canal, Anal-sphincter repair, Audit, Magnetic resonance imaging, Magnetic stimulation, Latency, Pelvic floor, Sacral roots
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25693 (URN)10069 (Local ID)91-7373-163-3 (ISBN)10069 (Archive number)10069 (OAI)
Public defence
2002-03-22, Berzeliussalen, Universitetssjukhuset, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-17Bibliographically approved

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