How reproducible are measures of the anal sphincter muscle diameter by endoanal ultrasound?

Anal endosonography is an imaging technique for the anal sphincter system and offers analysis of its muscular integrity. It is generally assumed that measurement of the thickness of muscle layers is provided by sonography; however, reproducibility of such measurements have not yet been investigated. METHODS: Study 1: In 10 healthy volunteers, endoanal ultrasound was performed independently by two experienced investigators with two different ultrasound machines, and thickness of the muscle layers of the internal and external anal sphincter was assessed in the position of the intermediate dorsal anal canal in a randomized cross-over fashion. Study 2: In a study of similar design, sonography was performed in nine healthy volunteers by two investigators independently using a single ultrasound machine in three standardized positions (proximal/intermediate/distal anal canal) and the sphincter layers assessed in the left, right, and dorsal segment. RESULTS: Study 1: Both the same investigator with different ultrasound scanners and different investigators with the same machine failed to obtain reproducible results with respect to internal and external anal sphincter muscle layer diameter (four bivariate correlations, all with p > 0.05). Study 2: Standardization of the probe position did not improve the agreement (2 x 9 bivariate correlations, all but two p > 0.05). CONCLUSION: At present, therefore, endoanal ultrasound does not provide reliable morphometric data on anal sphincter muscle diameter. This could explain previously conflicting observations of associations between anal sphincter morphometry and function.     

Interstitial cells of Cajal mediate inhibitory neurotransmission in the stomach

The structural relationships between interstitial cells of Cajal (ICC), varicose nerve fibers, and smooth muscle cells in the gastrointestinal tract have led to the suggestion that ICC may be involved in or mediate enteric neurotransmission. We characterized the distribution of ICC in the murine stomach and found two distinct classes on the basis of morphology and immunoreactivity to antibodies against c-Kit receptors. ICC with multiple processes formed a network in the myenteric plexus region from corpus to pylorus. Spindle-shaped ICC were found within the circular and longitudinal muscle layers (IC-IM) throughout the stomach. The density of these cells was greatest in the proximal stomach. IC-IM ran along nerve fibers and were closely associated with nerve terminals and adjacent smooth muscle cells. IC-IM failed to develop in mice with mutations in c-kit. Therefore, we used W/W(V) mutants to test whether IC-IM mediate neural inputs in muscles of the gastric fundus. The distribution of inhibitory nerves in the stomachs of c-kit mutants was normal, but NO-dependent inhibitory neuro-regulation was greatly reduced. Smooth muscle tissues of W/W(V) mutants relaxed in response to exogenous sodium nitroprusside, but the membrane potential effects of sodium nitroprusside were attenuated. These data suggest that IC-IM play a critical serial role in NO-dependent neurotransmission: the cellular mechanism(s) responsible for transducing NO into electrical responses may be expressed in IC-IM. Loss of these cells causes loss of electrical responsiveness and greatly reduces responses to nitrergic nerve stimulation.     

Comparative study of sensitive and vegetative innervation of external and internal anal sphincter muscles in different mammals

Proprioceptive innervation of the external anal sphincter muscle and the organization of the vegetative and sensitive nerve components of the internal and sphincter muscle have been studied in different mammals. The findings of typical muscle spindles in the external anal sphincter muscle were constant in the pig, frequent in the goat and cow, rare in the sheep and horse and absent in the roe and rabbit. In the pig, muscle spindles were observed in the entire extension of the muscle, while in the sheep, goat, cow and horse, the receptors were found only in the cranial portion of the muscle. In all the species studied, the internal anal sphincter muscle had numerous ganglion cells, isolated or grouped, and rare Pacinian, Pacinian-like, and Golgi-Mazzoni corpuscles. Their functional role has been hypothesized.     

Colocalization of NADPH-diaphorase staining and VIP immunoreactivity in neurons in opossum internal anal sphincter

Nitric oxide and vasoactive intestinal polypeptide (VIP) are important inhibitory neurotransmitters mediating relaxation of the internal anal sphincter. The location and coexistence of these two neurotransmitters in the internal anal sphincter has not been examined. We performed a double-labeling study to examine the coexistence of nitric oxide synthase and VIP in the opossum internal anal sphincter using the NADPH-diaphorase technique which is a histochemical stain for nitric oxide synthase. In perfusion-fixed, frozen-sectioned tissue, VIP-immunoreactive neurons were labeled using immunofluorescence histochemistry. After photographing the VIP-immunoreactive neurons, nitric oxide synthase was labeled using the NADPH-diaphorase technique. Ganglia containing neuronal cell bodies were present in the myenteric plexus for the entire extent of the internal anal sphincter. VIP-immunoreactive and NADPH-diaphorase-positive neurons were present in ganglia in the myenteric as well as the submucosal plexuses. Most of the VIP-immunoreactive neurons were also NADPH-diaphorase positive. VIP and nitric oxide synthase are present and frequently coexist in neurons in the internal anal sphincter of the opossum. These neurons may be an important source of inhibitory innervation mediating the rectoanal reflex-induced relaxation of the sphincter. The demonstration of the coexistence of these two neurotransmitters will be of fundamental importance in unraveling their relationship and interaction in the internal anal sphincter as well as other systems.     

Familial recurrent facial paresis: four generations

BACKGROUND: Chronic idiopathic intestinal pseudoobstruction (CIIPO) is a rare syndrome with an obscure pathogenesis. The proto-oncogene c-kit encodes a transmembrane tyrosine kinase receptor C-KIT that is critical for the development of the interstitial cells of Cajal, cells that are regarded as being the pacemaker cells of the gut. Thus, C-KIT immunopositive (C-KIT-) cells in the muscle layers of the bowel are considered to be intestinal pacemaker cells. METHODS: In this study, the distribution of intestinal pacemaker cells was examined for the first time using C-KIT immunohistochemistry in an infant with CIIPO. RESULTS: C-KIT+ cells were found lying on either side of the border between the two muscle layers (longitudinal and circular) of the bowel and dispersed unevenly throughout both muscle layers. Myenteric plexuses were not demarcated by C-KIT+ cells. In contrast, in controls, C-KIT+ cells were located distinctly between the two muscle layers of the small bowel and dispersed evenly throughout the muscle layers of the colon. Myenteric plexuses were clearly demarcated by C-KIT+ cells. CONCLUSIONS: This case demonstrates for the first time that there is abnormal distribution of intestinal pacemaker cells in CIIPO and provides new evidence that abnormal c-kit gene expression may be responsible for autonomic gut dysmotility. C-KIT immunohistochemistry may be an indispensable tool for diagnosing CIIPO.     

Regulation of prostaglandin endoperoxide H2 synthase in term human gestational tissues

The distribution in the chicken intestine of neuropeptide-immunoreactive (IR) ganglion cells and nerve fibres was investigated immunohistochemically. There were four kinds of ganglion cells: vasoactive intestinal polypeptide (VIP)-, substance P (SP)-, galanin (GAL)- and somatostatin (SOM)-IR cells in the submucous plexus (SMP) of the whole intestine and in the myenteric plexus (MYP) in the small intestine excluding VIP-IR ones. These peptide-containing fibres were found consistently but their distribution was variable in the mean areas in different regions of the intestinal wall. They seemed to be intrinsic. Comparing the jejunum and rectum in density and variation, the characteristics of innervation were as follows: villi in both intestines received more VIP-IR fibres than the other three which showed no significant difference. Crypts were surrounded with SP-IR fibres; these were denser than the other three in the jejunum compared with the rectum. The mean areas of SOM- and GAL-IR fibres were four and six times larger than those in the rectum, respectively. The SMP was supplied with the six kinds of neuropeptide-IR fibres, and VIP-IR fibres were dominant in both sides. Areas of VIP-, SP- and SOM-IR fibres were about two times greater than in the jejunum. The area of VIP-IR fibres in the circular muscle was significantly larger than that of the other four in both intestines; their density in the rectum was bout two times higher than in the jejunum. The mean area of SP-IR fibres in jejunal circular muscle was 14 times larger than that in the rectum. The MYP was supplied with seven kinds of neuropeptide-IR fibres except that methionine enkephalin-IR was absent from the rectum. Of these seven fibres, SP- and VIP-IR fibres in the jejunum had the largest areas. However, GAL-IR fibres in the jejunum were about four times denser than in the rectum. We conclude that the jejunum is characterized by the dense distribution of neuropeptide-IR fibres in crypts and MYP whereas in the rectum they occur in SMP and circular muscle. Fig. 15 summarizes the connections described in the present study.     

Changes in muscularis externa of rat small intestine after myenteric ablation with benzalkonium chloride: electron microscopic and morphometric study

The influence of the intrinsic innervation on the muscularis externa of the rat small intestine was studied by chemical ablation of the myenteric plexus with benzalkonium chloride (BAC). The resulting severe hypertrophy (cell hypertrophy of 96-133% and hyperplasia) differs from working hypertrophy by the distribution and degree of muscle thickening and by characteristics of the extracellular matrix: narrowing of muscle interspaces of 43%; lack of increased collagen; changes in the ratio of interstitial cells of Cajal (ICCs) to fibroblasts from 1.6:1 to 0.8:1 with no numerical decrease in either type of cell; decreased interconnections of ICCs to muscles and nerves due to deformed ICCs; a 197% increase in vascularization (capillaries, venules) and lymphatics in both muscle layers and in the myenteric plexus cleft, possibly initiated by release of fibroblast growth factor from myelin fragmentation after nerve damage; and increased macrophages, plasma cells, monocytes and mast cells in the myenteric plexus cleft. These all signify the neural influence on the morphodifferentiation of the muscularis externa in concert with the extracellular matrix components.     

Problems and results of Arthroplasty of the Knee Joint

The postnatal development of the adrenergic innervation pattern in the rat portal vein has been studied with the histochemical fluorescence method of Hillarp and Falck. Stretch preparations and transverse freeze-dried sections of intact portal veins were studied from rats during the first 5 weeks of life and from adult rats. Orientation of undifferentiated smooth muscle cells into two layers was observed at 4 days of age. Dominance of the thick outer longitudinal muscle layer was apparent at two weeks of age. A terminal adrenergic nerve plexus with some varicosities was restricted outside the media at the end of the first week. Ingrowth of penetrating non-terminal adrenergic nerve fibers through the longitudinal muscle layer occurred during the second week of age when the main terminal nerve plexus was developing between the two muscle layers. After 3 weeks of age the adult pattern of a two-dimensional adrenergic plexus between the muscle was established. In the adult rat pharmacological treatment with nialamide and noradrenaline revealed the thin, penetrating non-terminal adrenergic nerve fibers in the longitudinal muscle layer which were poorly visible otherwise. The present observations strongly indicate that the main adrenergic plexus between the two muscle layers emanates directly from the outer axonal plexus. These findings are discussed regarding possible trophic interactions between ingrowing sympathetic adrenergic vasomotor nerves and maturing vascular smooth muscle.     

Interstitial cells of Cajal mediate enteric inhibitory neurotransmission in the lower esophageal and pyloric sphincters

BACKGROUND & AIMS: Previous studies have suggested that a specific class of interstitial cells of Cajal (ICC) act as mediators in nitrergic inhibitory neurotransmission. The aim of this investigation was to examine the role of intramuscular ICC (IC-IM) in neurotransmission in the murine lower esophageal (LES) and pyloric sphincters (PS). METHODS: Immunohistochemistry and electrophysiology were used to study the distribution and role of IC-IM. RESULTS: The LES and PS contain spindle-shaped IC-IM, which form close relationships with nitric oxide synthase-containing nerve fibers. The PS contains ICC within the myenteric plexus and c-Kit immunopositive cells along the submucosal surface of the circular muscle. IC-IM were absent in the LES and PS of c-kit (W/Wv) mutant mice. Using these mutants, we tested whether IC-IM mediate neural inputs in the LES and PS. Although the distribution of inhibitory nerves was normal in W/Wv animals, NO-dependent inhibitory neurotransmission was reduced. Hyperpolarizations to sodium nitroprusside were also attenuated in W/Wv animals. CONCLUSIONS: The data suggest that IC-IM play an important role in NO-dependent neurotransmission in the LES and PS. IC-IM may be the effectors that transduce NO signals into hyperpolarizing responses. Loss of IC-IM may interfere with relaxations and normal motility in these sphincters.     

Comparison of the amnesic effects of propofol and isoflurane anesthesia

Networks of interstitial cells of Cajal embedded in the musculature of the gastrointestinal tract are involved in the generation of electrical pacemaker activity for gastrointestinal motility. This pacemaker activity manifests itself as rhythmic slow waves in membrane potential, and controls the frequency and propagation characteristics of gut contractile activity. Mice that lack a functional Kit receptor fail to develop the network of interstitial cells of Cajal associated with Auerbach's plexus in the mouse small intestine and do not generate slow wave activity. These cells could provide an essential component of slow wave activity (for example, a biochemical trigger that would be transferred to smooth muscle cells), or provide an actual pacemaker current that could initiate slow waves. Here we provide direct evidence that a single cell, identified as an interstitial cell of Cajal by light microscopy, electron microscopy and expression of Kit mRNA, generates spontaneous contractions and a rhythmic inward current that is insensitive to L-type calcium channel blockers. Identification of the pacemaker of gut motility will aid in the elucidation of the pathophysiology of intestinal motor disorders, and provide a target cell for pharmacological treatment.     

Prospectively evaluating anal sphincter function after ileal pouch-anal canal anastomosis

The decreased anal sphincter pressure that occurs after ileal pouch-anal canal anastomosis (IPAA) has usually been attributed to damage of the internal and sphincter. We hypothesized that the operation damages both the internal and the external anal sphincter. Resting pressure in the anal canal (a function of internal and external sphincters), anal squeeze pressure (a function of external sphincter only), and the rectal-anal inhibitory reflex (involving the internal sphincter) were measured manometrically in 10 patients with ulcerative colitis (4 women and 6 men; mean age, 33 years; range: 20 to 49 years). The patients were studied while awake before IPAA, under general anesthesia with striated muscle blockade just before incision, awake 2 months later before ileostomy takedown, and again under anesthesia with blockade just before takedown. The operation decreased maximum resting anal pressure while awake and during anesthesia with blockade. The decrease was detected in the proximal anal canal but not in the distal anal canal. In addition, the operation impaired anal squeeze pressure and abolished the rectal-anal inhibitory reflex. We conclude that IPAA damages both the internal and the external anal sphincter.     

Internal and external anal sphincter anatomy as it relates to midline obstetric lacerations

OBJECTIVE: To examine the anatomy of the internal and external anal sphincters in the area of midline obstetric lacerations, to gain insight into sphincter damage and repair. METHODS: The length, craniocaudal extent, and overlap of the internal and external anal sphincters in the perineal body were measured in 17 cadavers. Further anatomic observations were made in four sets of whole pelvis cross-sections taken in the sagittal, coronal, and transverse planes. During the repair of 20 acute fourth-degree lacerations, observations were made to determine the internal sphincter visibility following birth. RESULTS: The external and internal and sphincters overlap by 17.0 mm (standard deviation [SD] 6.9), with the internal sphincter lying between the external sphincter and the anal canal. The internal sphincter extends an additional 12.2 mm (SD 5.9) cranial to the proximal extent of the external sphincter, whereas the caudal margin of the internal sphincter lies 3.7 mm (SD 7.2) cranial to the distal margin of the external sphincter. In pregnant women who sustained a fourth-degree laceration, we found that the internal sphincter can be identified as a rubbery white layer adjacent to the anal submucosa lying between the external sphincter and the anal canal. CONCLUSION: The internal anal sphincter lies between the anal mucosa and the external anal sphincter and extends more than a centimeter above the cranial margin of the external sphincter, a region where it is disrupted when a fourth-degree obstetric laceration has occurred.     

Insulin-stimulated cell growth in insulin receptor substrate-1-deficient ZR-75-1 cells is mediated by a phosphatidylinositol-3-kinase-independent pathway

The projections of enteric neurons to the circular muscle of the guinea pig gastric corpus were investigated systematically by using the retrogradely transported fluorescent carbocyanine dye 1,1'-didodecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (DiI), applied to the muscle layer or myenteric plexus in vitro. DiI-labeled motor neuron cell bodies were located up to 6.3 mm aboral, 17 mm oral, and up to 20 mm circumferential to the DiI application site. Labeled nerve fibers ran for long distances from the DiI application site toward the greater and lesser curvatures, where they coursed parallel to the bundles of the "gastric sling" muscle. The majority of labeled cells were located toward the lesser curvature of the stomach. Nerve cell bodies that were aboral to the DiI application site were usually small, immunoreactive for choline acetyltransferase, and, thus, were likely to be excitatory motor neurons. Neurons that were located orally were larger, fewer in number, and immunoreactive for nitric oxide synthase and, thus, were likely to be inhibitory motor neurons. Application of DiI directly to the myenteric plexus filled neurons up to 15 mm aborally and up to 21 mm orally but labeled few neurons circumferentially. All nerve cells that were filled from either the circular muscle or the myenteric plexus had Dogiel type I morphological features. These results demonstrate a clear polarity of projection of inhibitory and excitatory motor neurons and a functionally continuous innervation of the circular and gastric sling muscle layers. Nonmotor neurons in the myenteric plexus were demonstrated, but neurons with Dogiel type II morphological features are apparently absent.     

Clonazepam in the treatment of panic disorder: a double-blind, placebo-controlled trial investigating the correlation between clonazepam concentrations in plasma and clinical response

The aim of this study was to investigate the possibility of neuromuscular dysfunction in patients with faecal incontinence by measuring interference patterns in the external anal sphincter and puborectalis muscles with quantitative electromyography. The design was an open study including 20 patients with faecal incontinence; in 14 the aetiology was idiopathic and 6 had rupture of the external anal sphincter. Electromyographic interference patterns (turns/amplitude analysis) measured at rest and during maximum voluntary contraction in all patients were recorded together with fibre density measured by single fibre electromyography (n = 10) and anal pressure measured at rest and at maximum contraction (n = 17). A comparison was made with results of a previously published series of reference values taken from normal volunteers. The density of the interference pattern on maximum contraction of the puborectalis muscle was significantly lower among the patients with idiopathic faecal incontinence than among the reference group (137 compared with 241 turns/second, p < 0.01). There was also a significant difference on maximum contraction of the anal sphincter muscle among the group in whom it was ruptured compared with the reference group (76 compared with 165 turns/second, p < 0.05). Fibre density increased with age and was significantly higher among those with idiopathic incontinence (1.64 (0.2) compared with 1.33 (0.1) in the reference group, p < 0.01). There were no significant differences in anal manometry measurements between the groups. In conclusion, in patients with faecal incontinence the role of central activation of the perineal muscles is important, though other factors may play a part.     

The longitudinal muscle of the anal canal

The longitudinal muscle (LM) represents a strong muscular structure of the anal canal situated between the internal (IAS) and the external anal sphincter (EAS). Terminal fibres of this muscle insert at the submucosa of the anal canal, representing the m. canalis ani. Others cross the subcutaneous part of the EAS to become the m. corrugator ani. Thus, the LM connects the visceral and somatic parts of the anal sphincter complex. Histologically ganglionic cells and as Vater-Pacinian corpuscles can be identified inside the LM. Morphology, topography and histology of the LM suggest that this muscle participates in maintaining anorectal continence. It is mandatory that the exact functions of this muscular structure be to elaborated upon, if we are to understand the mechanism of anorectal continence.     

Dynamic anal manometry in the assessment of patients with obstructed defecation

Patients with obstructed defecation show no consistent abnormalities when assessed by standard anorectal physiologic methods. With a recently developed technique for dynamic anal manometry, we studied 13 female patients with obstructed defecation and 20 healthy volunteers. Seven parameters of anal function were measured. There were no differences between the median values for the two groups. Seven patients (54 percent; 95 percent confidence limits, 25-81 percent) had anal compliance below the normal range, either during opening or closing of the sphincter at rest (five patients), during squeeze (one patient), or both (one patient). Opening and closing pressures of the sphincter at rest, maximal closing pressure during squeeze, and anal hysteresis were normal. Standard anal manometry did not show any differences between patients and controls. Rectal compliance was lower in patients with obstructed defecation, median difference 5 ml/cm H2O (95 percent confidence limits, 1-9 ml/cm H2O). In conclusion, the more detailed method of dynamic anal manometry shows that some patients with obstructed defecation have a less compliant anal sphincter and a less compliant rectum, but in many patients no abnormal findings can be made.     

Anal sphincter defects. Correlation between endoanal ultrasound and surgery

OBJECTIVE: This study was performed to (1) correlate and sphincter defects, identified by endoanal ultrasound with operative findings, and (2) define the appearance of such sphincter defects as seen at operation. SUMMARY BACKGROUND DATA: Endoanal ultrasonography is a minimally invasive method of imaging the anal sphincter complex and enables identification of anal sphincter defects. Little is known about the accuracy and limitations of endoanal ultrasound in identifying such defects. Furthermore, there are no data about the appearances of these endosonic sphincter defects as seen at operation. METHODS: Forty-four patients (40 women; age range, 26 to 80 years; mean age, 56 years) with fecal incontinence, undergoing pelvic floor repair, were investigated by endoanal ultrasound before operation. Endosonic findings were correlated with the appearances of external anal sphincter, internal anal sphincter, and intersphincteric space, at operation. Diagnosis of the site and type of defect was made by macroscopic appearances. Uncertainty about the type of sphincter defect was resolved by obtaining muscle biopsies for histology. RESULTS: All external sphincter defects seen by endoanal ultrasound (n = 23) were confirmed at operation. Twenty-one of 22 internal sphincter defects identified by endosonography also were confirmed at operation. In ten patients with a neuropathic anal sphincter complex, the morphology was normal on endosonography, and this was confirmed at operation. (Sensitivity and specificity of 100% for external anal sphincter; 100% and 95.5%, respectively, for internal and sphincter) CONCLUSIONS: These data show that endoanal ultrasound is an accurate method of identifying anal sphincter defects.     

Projections of pelvic autonomic neurons within the lower bowel of the male rat: an anterograde labelling study

The tissues of the large intestine which receive an innervation by neurons of the major pelvic ganglia were identified following in vivo and in vitro anterograde labelling with the lipophilic tracer 1,1'didodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate in the male rat. The primary target in the gut of major pelvic ganglion neurons is the myenteric plexus of the distal colon and the rectum. The serosal ganglia, on the surface of the most distal region of the rectum and the circular muscle of the distal colon and rectum were less densely innervated. The pelvic ganglia do not innervate the longitudinal muscle, submucosal blood vessels, submucosal plexus, or mucosa. The pelvic supply reaches the bowel via two groups of rectal nerves and branches of the penile nerves. All of these connections also carry the axons of viscerofugal neurons from the bowel, some of which have terminal axons in the major pelvic ganglia. Finally, the different nerves supplied different targets. In particular, while the rectal nerves carried pelvic axons supplying the myenteric plexus, circular muscle, and serosal ganglia, the penile nerves only innervated the serosal ganglia. In addition, the two groups of rectal nerves innervated slightly different regions of the bowel and provided different projection patterns. However, successful in vivo labelling was achieved in only 6/12 animals and while all in vitro experiments resulted in successful labelling, it was clear that only a proportion of pelvic projections in any given nerve were labelled. These studies have shown that the major pelvic ganglia are primarily involved in the control of motility, but not of vascular and secretomotor functions. Thus pelvic neurons do not innervate the same range of target tissues within the bowel as the prevertebral ganglia. This study has also shown that the different pathways to the gut from the major pelvic ganglia innervate different tissues, suggesting that the autonomic innervation of the gut is not homogeneous along its length.     

Low anterior resection with a long posterior anorectal myectomy and sphincterectomy for Hirschsprung's disease

Nine patients with the severe form of Hirschhsprung's Disease (HD) underwent low anterior resection with posterior anal myectomy and sphincterectomy. Good results were achieved in six patients. Three patients had bouts of enterocolitis following the surgical treatment which was attributed to residual spasm of the aganglionic rectum and the internal anal sphincter. Myectomy had to be redone in two patients. One patient developed constipation which responded to toilet training. One patient died at home of an unknown cause, and one patient was lost to follow-up. The different methods of treatment of HD are discussed with emphasis on the role of the internal anal sphincter. The relatively high complication rate in this small group of patients does not justify its use in the severe form of HD.