Normal Anal Canal Research Articles

Endosonographic Anatomy of the Normal Anal Canal Compared with Endocoil Magnetic Resonance Imaging

This study was designed to clarify the sonographic anatomy of the normal anal canal by comparison with endoanal magnetic resonance imaging, to determine agreement between these imaging modalities and interobserver error in measuring layer thickness. Three-dimensional endosonographic and endocoil magnetic resonance images of the anal canal were obtained in four males and five nulliparous females aged 22 to 34 years. Images were analyzed at similar levels throughout the canal using a graphics-overlay technique to compare sonographic with magnetic resonance images. Measurements were taken at one level for agreement analysis between modalities and for interobserver variability in the measurement of the thickness of the main anal canal layers. The muscularis submucosae ani, muscle bundles in the longitudinal muscle layer, and puboanalis were identified on sonography. The outer border of the external sphincter was demarcated by an interface reflection with ischioanal fat. Clarification of the external sphincter anatomy allowed excellent correlation (Ri = 0.96) for the assessment of thickness. There was excellent correlation for the interobserver measurement of the external and internal sphincters and the submucosal width on endosonography, but there was poor correlation for the longitudinal muscle (0.12). The overlay technique has improved endosonographic interpretation, and measurement of external sphincter thickness has been validated both by comparison with magnetic resonance and on interobserver agreement.

Multiplanar anal endosonography--normal anal canal anatomy.

Volume acquisition during anal ultrasound enables multiplanar imaging of the anal canal. The normal ultrasonic multiplanar appearance of the anal canal is described and gender differences in canal anatomy are highlighted. Ten male and 12 female normal volunteers (mean ages 31.5 years (s.d. 5.9) and 31.2 (s.d. 6.7)) had three-dimensional anal endosonography (3-D AES). Each volume dataset was seeded in the axial plane facilitating multiplanar identification of known anatomical structures. The anterior external anal sphincter (EAS) was significantly longer in men than women 30.1 mm (3.9) vs 16.9 mm (7.4) (P < 0.001). There was no difference in the length of the puborectalis 24.7 mm (6.4) vs 24 mm (5) (P=0.78) in men compared with women. The cranial extent of the anterior EAS was tilted forward in both sexes. The angle formed by the anterior EAS and the longitudinal axis of the anal canal was more acute in men than in women (11.1 degrees vs 18.6 degrees; P=0.007). Dataset volume seeding of familiar structures in the axial plane allowed the multiplanar endosonographic anatomy to be described. Multiplanar AES has enabled detailed longitudinal measurement of the components of the anal canal and has revealed important gender differences. The multiplanar ultrasonic appearance of the normal anal canal has been described for the first time.

Endoanal ultrasound (Normal and abnormal)

This article presents a full description of the indications for and the technique of endoanal ultrasound. The background to the procedure is reviewed in brief before a fully illustrated description of the endosonographic appearance of the normal anal canal is given. Gender differences are highlighted and common variations in normal anatomy are explained. The appearances of common pathological conditions are then detailed.

Fecal incontinence with normal anal canal pressures: where is the pitfall?

OBJECTIVE: One third of subjects who suffer from fecal incontinence are found to have values within the normal range when anal manometry is performed. For these patients, one hypothesis is that impaired rectal adaptation to distension may occur. The aim of our study was to analyze anorectal responses to rectal isobaric distension in this population. METHODS: This was a prospective study conducted in 51 consecutive incontinent patients (45 female, six male) divided into two groups according to their functional anal state: absence (19 patients aged 55 ± 6 yr) or presence of manometric anal weakness (32 patients aged 59 ± 2 yr). The subjects were submitted to two randomized modes of rectal isobaric distension (tonic, phasic) with an electronic barostat. Anal pressures, perception, and volumes of the rectum were recorded at six different preselected pressures. RESULTS: As compared with those having anal weakness, patients with no anal weakness retained higher mean pressures at both upper (36.9 ± 2.2 vs 22.9 ± 1.4 mm Hg; p = 0.01) and lower parts (41.0 ± 2.0 vs 23.3 ± 1.4 mm Hg; p = 0.002) of the anal canal, similar perception scores, but much lower rectal volumes (68.5 ± 5.5 vs 121.8 ± 7.0 ml; p = 0.008) in response to rectal isobaric distension. CONCLUSION: A decrease in rectal adaptation could be involved in fecal leakage in patients with no anal manometric weakness.

Elevated density and plasticity of nerve fibres in anal fissures.

Neural proliferative processes are regarded as a contributing factor in chronic inflammatory diseases and chronic pain. To elucidate whether neural proliferations occur in tissues surrounding chronic anal fissures and in the normal anal canal, the nerve fibre density was examined with the pan-neural marker protein gene product 9.5 (PGP) and the neural proliferative marker growth-associated protein 43 (GAP) by immunohistochemistry. GAP-immunoreactive nerve fibres in the uninflamed anal canal were distributed region specifically. The proportion of GAP-immunoreactive nerves in relation to the PGP-immunoreactive innervation exhibited regional differences. In tissue sections of chronic anal fissures, a marked increase in the density of PGP- and GAP-immunoreactive nerve fibres was noted, and PGP- and GAP-immunopositive nerve fibres displayed a neuroma-like appearance. Image analysis revealed that PGP- and GAP-immunoreactive innervation represented an area fraction of 0.5% (0.49 +/- 0.052; mean and SEM) and 0.1% (0.11 +/- 0.013) in the normal anal canal, respectively. In tissue sections of chronic anal fissures, PGP- and GAP-immunostained nerve fibres represented area fractions of 1.3% (1.32 +/- 0.12) and 0.6% (0.56 +/- 0.15), respectively. The increases in PGP- and GAP-immunopositive area fractions were highly significant (P > 0.01). The mean ratio of GAP to PGP immunoreactivities was not significantly increased in chronic anal fissures. The increase in pan-neural innervation and neuronal GAP immunoreactivity in tissues of anal fissures may imply that neuronal proliferation is involved in the pathogenesis of anal fissures. Neuronal proliferations may also be responsible for pruritus and severe pain in chronic anal fissures.

An unusual variant of rectal atresia with rectovestibular fistula

Isolated rectal atresia in the girl with a normal anal canal is extremely rare, and its association with a fistula has not been reported in the literature. A 6-year-old girl who had a unique combination of rectal atresia and rectovestibular fistula was treated successfully by a posterior sagittal approach.

The anterior sagittal approach for high imperforate anus: A simplification of the mollard approach

High imperforate anus is a complex anomaly that requires a combination of careful preservation of native structures and precise anatomic reconstruction for optimal results. Previously the authors used an anterior perineal approach derived from the technique described by Mollard, with generally satisfactory results. The present report describes the authors' refinement of the technique to avoid skin flaps and to construct a shorter, more normal anal canal. The perineal approach, via an anterior sagittal incision, usually is combined with a transverse suprapubic laparotomy. The technique includes division of the external sphincter and longitudinal muscle fibers anteriorly, simple dilatation of the puborectalis, and division of the fistula close to the urethra, with preservation of the internal sphincter. The rectal pouch is brought down to the level of the puborectalis, without tapering, and the anoderm is brought up to the level of the rectal pouch to construct a shorter anal canal with a normal anorectal angle. This technique maximally preserves internal sphincter function, preserves specialized anoderm for the anal canal, and avoids extensive pelvic dissection and division of the levator sling. It also facilitates repair in the neonatal period, which may be optimal for long-term continence. The authors have used this technique in five patients, with good anatomic and short-term functional results. The authors believe that the technique provides optimal preservation of native tissues; only minimal destruction and dissection are required for reconstruction.

Keratin expression in the normal anal canal

The pattern of epithelial keratin expression in the normal anal canal has not been extensively defined and is a necessary prerequisite to the interpretation of alterations in these intermediate filaments in pathological anal epithelial lesions. Thirty-five frozen tissue specimens of resected haemorrhoids were investigated immunohistologically for expression of 14 individual keratins (K) using a panel of 17 monoclonal antibodies. Perianal skin showed basal expression of keratinocyte Ks 5, 14 and 17, and suprabasal expression of keratinocyte Ks 14, 10, 1 and 16. Anal squamous epithelium showed persistent basal K5 and 17, basal and suprabasal K4, 13 and 16 positivity, with sporadic expression of K1 and 10. The expression of simple epithelial keratins in squamous epithelium adjacent to the anal transitional zone varied with basal expression of K7, K8, K18 and K19 and sporadic suprabasal expression of K7 and K19. The anal transitional zone (ATZ) expressed K19, as found in transitional epithelia elsewhere. The full thickness of epithelium was positive for the simple epithelial Ks 7, 8 18 and 19. Marked heterogeneity of keratinocyte keratin expression was seen. Basal layers expressed Ks 4, 13, 14 and 17 and variably K16, while suprabasal layers expressed Ks 4 and 13, 14 and 17 and variably K16, while suprabasal layers expressed Ks 4 and 13 and variably K14, 16 and 17. This anomalous expression of keratinocyte K4 and 13 has also been documented in transitional epithelium of the bladder. The anal glands and ducts showed a keratin distribution similar to the transition zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Endoanal ultrasonography in the follow-up of anal carcinoma.

As the modern treatment for anal carcinoma is either radiotherapy alone or combined radiochemotherapy, an exact histological staging is impossible. Therefore we have to depend on an accurate preoperative staging method. Endoanal ultrasonography enables imaging of the normal anal canal and its pathologies. In a prospective investigation we were able to confirm the histological proven diagnosis of an anal epidermoid carcinoma in 12 patients with a 10-MHz transducer covered with a sonolucent plastic cone. The depth of infiltration can be determined in relation to the normal layers of the anal canal. Six patients treated with radiotherapy alone or combined radiochemotherapy were followed and the success or failure of the treatment was documented. Endosonography of the anal canal allows an exact staging of a primary anal carcinoma and the follow-up in irradiated carcinomas. Besides digital palpation and proctoscopy with biopsy, endosonography complements the preoperative staging of anal carcinomas.

Anal colposcopy and the diagnosis of anal intraepithelial neoplasia in high-risk gynecologic patients.

The objective of this study was to define the colposcopic features of the normal anal canal and of anal human papillomavirus (HPV)-associated lesions, including anal intraepithelial neoplasia (AIN), and to correlate the colposcopic impression with the final histopathologic diagnosis. A controled colposcopic screening study of women considered at risk for HPV-associated anal epithelial abnormalities was carried out. All colposcopic assessments included a biopsy with matching histopathologic diagnosis. The study group consisted of 213 women who were considered at risk of anal HPV infection and AIN. A further group of 50 women, who had no previous history of ano-genital HPV infection or AIN and whose recent cervical smear was negative were recruited as controls. Informed consent was obtained from all patients, and the study was approved by the local ethical committee. In the control group of 50 women no AIN was detected. Normal histology was obtained in 45/50 (90%) biopsies where normality had been predicted on colposcopy. Histologic diagnosis in the at-risk group was normal in 143 (67%), subclinical papillomarvirus infection (SPI) in 24 (11%), and AIN of all grades (including three cases of early invasive squamous cancer in a field change of AIN III) in 46 (22%) patients. Nineteen of 24 (79%) cases of SPI were incorrectly predicted as normal on colposcopy, and another one (4%) as AIN I-II. Only four (17%) cases of SPI were correctly predicted at colposcopy. Of the 46 cases of histologically proven AIN, 26 (56%) were AIN I-II, and 20 (44%) were AIN III. Some 50% of AIN I-II were incorrectly predicted as SPI on colposcopy. Of the 20 AIN III lesions, 15 (75%) were correctly predicted by colposcopy. Three (20%) of these lesions contained foci of early invasion, of which in only one case (33.3%) was invasive disease suspected at colposcopy. Some 25% (5/20) of AIN III lesions were incorrectly diagnosed as AIN I-II at colposcopy. As is the experience with colposcopic assessment of the cervix, anal colposcopy predictions correlated well with the final histologic diagnosis, at the normal and high-grade AIN ends of the spectrum. The colposcopic predictive distinction between SPI and low-grade AIN (I-II) was less accurate. It was difficult to distinguish early invasive lesions within a field change of AIN III, from pure AIN III. In these studies there were three cases of early anal squamous carcinoma arising in AIN III lesions, two of which were unsuspected clinically.

Endoluminal ultrasound defines anatomy of the anal canal and pelvic floor.

The aims of this study were to determine whether endoluminal ultrasound (ELUS) could identify various layers of the normal anal canal and to evaluate whether a 10-MHz probe provided better image resolution than a 7-MHz probe. Sonographic anatomy of the anal canal on ELUS was directly correlated with anatomic dissection of various layers (mucosa-submucosa, internal anal sphincter, and external anal sphincter) in cadavers. Sonographic appearance of the anal sphincters was further evaluated in patients by "tagging" various layers using sonodense needles. A higher frequency 10-MHz ultrasound probe (focal length, 1-4 cm) provides improved sonographic images of the anal canal, compared with the 7-MHz probe (focal length, 2-5 cm). ELUS can also successfully identify various structures of the pelvic floor including the puborectalis, urethral sphincter, vagina, and outlines of the pelvis and ischiorectal fossae. Its role in the evaluation of anorectal disorders appears promising.

The rectourogenital connection in anorectal malformations is an ectopic anal canal

Histological investigation of the rectal blind pouch and rectourogenital or rectoperineal connection was performed in 10 patients with high of intermediate anorectal malformations. Nine of the patients underwent postoperative manometric evaluation. In nine of the 10 patients, transitional epithelium typical of the normal anal canal could be found in the distal rectum or rectal end of the fistulous connection. The zone of transitional epithelium was aganglionic and showed abnormally strong acetylcholinesterase reaction. A positive rectoanal inhibitory reflex was found manometrically in all cases in which the distal rectal pouch was utilized in the reconstruction of the anal canal. The slow pressure wave activity of the reconstructed anal canal was characteristic of a normal anal canal. The manometric evidence strongly suggests that there is a functional internal sphincter in high and intermediate anorectal malformations. The present study shows that in anorectal malformations the distal rectal pouch with the fistulous connection is actually an ectopic anal canal.

Anal canal pressure profile: a reappraisal as determined by rapid pullthrough technique.

Previous station pull through techniques of anal canal pressure measurement have not truly represented the differences among individuals and between sexes in the length and pressure profile of the anal canal. Furthermore, the techniques commonly used in anal canal pressure determination have not been adequately compared or standardised. Therefore, a mechanised rapid pull through technique using an 8-lumen, 4-quadrant, continuously perfused catheter was evaluated and used to define the anal canal pressure profile. For measurement of the resting anal canal pressures, this technique was compared with the more usual station pull through technique in 12 subjects. There were no differences in resting pressure recorded by either technique with infusion rates ranging from 0.5 to 1.2 cc/min/orifice and over a range of catheter withdrawal rates of 0.19 to 0.48 cm/sec. Twenty two subjects (12 men/10 women) had their anal canal pressure profiles assessed using the rapid pull through technique. Anal canal length representing the mean of four axes differed between the sexes (p less than 0.005) and the difference was largely accounted for by a decrease in length of the anterior axis in women. A standardisation technique was used to account for between subject variation and for a more accurate between sex comparison of the pressure profiles. Significant differences in radial symmetry were found between the sexes. In the anterior axis the pressure was higher distally in women, while in the anterior and lateral axes the pressure was higher proximally in men. Anteriorly in women the highest pressures were exerted over a much shorter canal length than in men. We conclude that the usual station pull through technique can give reliable resting pressure measurements in the anal canal. The rapid pull through technique described herein, however, used a flexible catheter system which follows the normal anal canal and rectal contours, allows a more appropriate assessment of the anal sphincter profile, and provides findings that are consistent with the known local anatomy.

Results after posterior sagittal anorectoplasty: A new approach to high imperforate anus

Six patients, 3 to 12 months of age have undergone posterior sagittal anorectoplasty for high imperforate anus. A rectourethral fistula was present in all patients. The operative procedure performed was the method of de Vries and Pena, utilizing electrostimulation and identification of the external sphincter muscles. One patient required an abdominal operation as well as the perineal approach. There were no complications. Serial assessment was carried out over a period of 4 months to 2 1/2 years. Normal continence was achieved in three patients. Anorectal manometry was performed in five patients. Four of five patients had normal rectal sensation and normal mean anal canal pressures. These results suggest that this procedure is applicable to the young infant with high imperforate anus, and a satisfactory result can be anticipated.

Anal sphincteric pressure in fissure-in-ano before and after lateral internal sphincterotomy.

Resting anal canal pressure was measured in 15 patients with anal fissure before and after lateral internal sphincterotomy. This pressure was found to be significantly higher in these subjects (mean 95 +/- 23.08 mm HG) than in the control group (mean 66.10 +/- 14.28 mm Hg) before surgery (P less than 0.005). After surgery, a normal anal canal pressure was produced. The authors maintain that anal canal spasm is responsible for chronicity of anal fissures.

Ganglion cell distribution in the normal rectum and anal canal A basis for the diagnosis of Hirschsprung's disease by anorectal biopsy

The normal distribution of ganglia and ganglion cells in the anal canals and lower rectums of 22 babies and children has been plotted and enumerated. Ganglion cells were distributed in three separate plexuses, the myenteric, the deep submucous, and the superficial submucous plexuses. A “hypoganglionic” zone has been defined and found to extend an average of 4 mm. in the myenteric plexus, 7 mm. in the deep submucous plexus, and 10 mm. in the superificial submucous plexus from and cranial to the anal valves or pectinate line of the anal canal. Any biopsy which includes the plexus above the theoretical upper limit of the hypoganglionic zone should be adequate for the diagnosis of Hirschsprung's disease. In particular, mucosal buttons obtained by suction capsule provide the pathologist with suitable material for the detection of ganglion cells in the superficial submucous ganglion cell layer provided the sections are stained with hematoxylin and eosin after paraffin processing. These ganglion cells are extremely difficult to identify by frozen section and this method is not suitable for these small specimens. Presence of ganglion cells in specimens obtained from the hypoganglionic zone or a point 3 cm. inside the anal valves excludes the diagnosis of Hirschsprung's disease. Absence of ganglion cells in the hypoganglionic zone does not exclude Hirschsprung's disease, but absence at the point 3 cm. inside the anal canal is diagnostic of this disease.

The microscopic anatomy of the terminal intestinal canal in ectopic vulval anus

The deformity to which this paper refers is also termed the ectopic vestibular anus, the female anterior anus or type III imperforate anus with rectoperineal fistula. It is that deformity in which there is a separate terminal opening for the rectum situated on the surface within the posterior confines of the vulva immediately adjacent and posterior to the vaginal orifice. This investigation was undertaken in order to determine whether in this deformity the terminal intestinal canal possesses any of the microscopic anatomical features of a normal anal canal.