Interstitial cells of Cajal modulate the tone of the human internal anal sphincter in vitro.

BACKGROUND: Interstitial cells of Cajal, expressing the proto-oncogene c-kit, have been shown to regulate the spontaneous activity of the gastrointestinal tract. They have been described in the human internal anal sphincter; however, their function is still unclear. OBJECTIVE: We examined the effects of the c-kit tyrosine kinase inhibitor imatinib mesylate on sphincter strips to investigate the function of the interstitial cells. DESIGN: This was a case series study. SETTIGS: This was a single-center study conducted at the University of Oxford. PATIENTS: Internal anal sphincter strips were collected from 10 patients undergoing abdominoperineal resection or proctectomy and mounted in organ bath. Responses to electrical field stimulation and chemical agents were monitored in the absence of drugs and after the administration of increasing doses of imatinib mesylate. Immunohistochemistry was performed to identify interstitial cells. MAIN OUTCOME MEASURES: The role of the interstitial cells in the internal anal sphincter was assessed. RESULTS: Imatinib mesylate significantly reduced the tone and the spontaneous activity of the strips. In the absence of drugs, the tone generated was 147.7 ± 33.0 mg/mg of tissue. Administration of ≥5 µM of imatinib mesylate caused a dose-dependent reduction in the tone. Strips exhibited spontaneous activity characterized by intermittent low-amplitude contractions superimposed on basal tone (135.6 ± 4.6 contractions in 10 minutes). Imatinib mesylate significantly reduced the number of contractions at concentration >5 µM. No differences were observed in the responses to electrical field stimulation, carbachol, or phenylephrine. Immunohistochemistry showed c-kit-positive cells. LIMITATIONS: This study was limited by the relatively small number of patients enrolled and thus the difficulty of finding human tissue for laboratory studies. CONCLUSIONS: Our results suggest that the interstitial cells modulate the tone and the spontaneous activity of the internal anal sphincter. This provides a foundation for new approaches to preclinical and clinical research. Moreover, these cells may represent a target for drugs inhibiting the c-kit receptor and provide a new approach for treating anorectal diseases.

Digital rectal examination of sphincter pressures in chronic anal fissure is unreliable.

PURPOSE: Chronic anal fissure is said to be associated with internal sphincter hypertonia. However, an unknown proportion of fissures may be associated with normal or even low resting pressures and may subsequently be resistant to pharmacological treatments or at risk from surgical treatments, both of which aim to reduce sphincter hypertonia. This study investigated the ability of surgeons to detect low or normal pressure fissures by digital rectal examination. METHODS: Patients with chronic anal fissure were assessed prospectively. The results of anal manometry performed on these patients were compared with digital rectal assessment of sphincter tone undertaken by a surgeon blinded to the manometry results. RESULTS: Forty consecutive patients (21 male) with chronic anal fissure were studied. Twenty-two (55 percent) had normal maximum resting pressure and a further 3 (8 percent) had low pressures on anal manometry. On clinical assessment, only five (13 percent) patients were evaluated as having no anal hypertonia. Clinical assessment of anal tone correctly identified 14 of 15 patients with high manometric maximum resting pressure (sensitivity, 93 percent), yet detected only 4 of 25 patients with normal or low pressures (specificity, 16 percent). The positive predictive value of clinical assessment of anal tone was 40 percent and the negative predictive value, 80 percent. CONCLUSIONS: The incidence of patients with chronic anal fissure without high manometric maximum resting pressure is higher than previously reported. The ability of surgeons to identify this group clinically was poor. It is reasonable to treat all patients primarily medically, and then selectively investigate by manometry those patients who fail medical therapy before considering lateral sphincterotomy.

Fissurectomy-botulinum toxin: a novel sphincter-sparing procedure for medically resistant chronic anal fissure.

BACKGROUND: Botulinum toxin heals only approximately one-half of glyceryl trinitrate-resistant chronic anal fissures, perhaps because chemical sphincterotomy alone treats internal sphincter spasm but not chronic fissure fibrosis. We aimed to assess whether a novel procedure, fissurectomy-botulinum toxin, improves the healing rate of medically resistant fissures over that achieved with botulinum toxin alone. METHODS: A prospective pilot study of chronic fissure patients failing medical therapy was undertaken. Fissurectomy was performed, with excision of the fibrotic fissure edges, curetting of the fissure base, and excision of the sentinel pile if present. Twenty-five units of botulinum toxin (Botox) were injected into the internal sphincter. The primary end point was fissure healing, and secondary end points were improvement in symptoms, need for lateral internal sphincterotomy, and side effects. RESULTS: Thirty patients underwent fissurectomy-botulinum toxin (57 percent female; median age, 39 years). Nineteen patients had failed glyceryl trinitrate, whereas 11 had failure of both glyceryl trinitrate and botulinum toxin. At a median of 16.4 weeks follow-up, 28 fissures (93 percent) were healed. Two fissures (7 percent) remained unhealed but were symptomatically better and avoided lateral internal sphincterotomy. Two patients (7 percent) experienced transitory flatus incontinence. CONCLUSION: Fissurectomy-botulinum toxin heals over 90 percent of fissures resistant to medical therapy. Fissurectomy-botulinum toxin allows patients with medically resistant fissures to achieve a high rate of healing while avoiding the risk of incontinence associated with lateral internal sphincterotomy.

Multiple rare variants in different genes account for multifactorial inherited susceptibility to colorectal adenomas.

Clear-cut inherited Mendelian traits, such as familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer, account for <4% of colorectal cancers. Another 20% of all colorectal cancers are thought to occur in individuals with a significant inherited multifactorial susceptibility to colorectal cancer that is not obviously familial. Incompletely penetrant, comparatively rare missense variants in the adenomatous polyposis coli gene, which is responsible for familial adenomatous polyposis, have been described in patients with multiple colorectal adenomas. These variants represent a category of variation that has been suggested, quite generally, to account for a substantial fraction of such multifactorial inherited susceptibility. The aim of this study was to explore this rare variant hypothesis for multifactorial inheritance by using multiple colorectal adenomas as the model. Patients with multiple adenomas were screened for germ-line variants in a panel of candidate genes. Germ-line DNA was obtained from 124 patients with between 3 and 100 histologically proven synchronous or metachronous adenomatous polyps. All patients were tested for the adenomatous polyposis coli variants I1307K and E1317Q, and variants were also sought in AXIN1 (axin), CTNNB1 (beta-catenin), and the mismatch repair genes hMLH1 and hMSH2. The control group consisted of 483 random controls. Thirty of 124 (24.9%) patients carried potentially pathogenic germ-line variants as compared with 55 ( approximately 12%) of the controls. This overall difference is highly significant, suggesting that many rare variants collectively contribute to the inherited susceptibility to colorectal adenomas.

Role of nitric oxide in anorectal function of normal and neuronal nitric oxide synthase knockout mice: a novel approach to anorectal disease.

PURPOSE: In vitro data suggest that nitric oxide is an important inhibitory neurotransmitter in the internal anal sphincter, and morphologic evidence implies that it mediates the rectoanal inhibitory reflex. This study examined the anatomy, physiology, and pharmacology of the internal sphincter in control and neuronal nitric oxide synthase knockout mice. METHODS: Neuronal nitric oxide synthase, nicotinamide adenosine triphosphate dinucleotide phosphate diaphorase histochemistry, and PGP 9.5 immunohistochemistry were compared between knockout and sibling control mice. Anorectal manometry was performed with a balloon-tipped water-perfused catheter. In vitro studies were performed on both whole internal anal sphincter rings and strips. RESULTS: Staining of the myenteric plexus and nerves traversing the internal anal sphincter in sibling control mice demonstrated the presence of neuronal nitric oxide synthase and nicotinamide adenine dinucleotide phosphate diaphorase at these sites. These markers were absent in knockout mice. Maximum anal resting pressure was similar in control and knockout mice (15.6 +/- 2.6 cm H(2)O (n = 4) vs. 14.0 +/- 2.3 cm H(2)O (n = 7)). The rectoanal inhibitory reflex was present in all control mice (n = 4) but in only four of seven knockout mice. Field stimulation with parameters designed to activate inhibitory nerves produced relaxation of internal sphincter tissue from both control and knockout mice, which was partially attenuated in control mice only by pretreatment with the nitric oxide synthase inhibitor N omega-nitro-L-arginine. Further inhibition of nerve-induced relaxation in control mice was achieved with antagonists of vasoactive intestinal peptide, adenosine triphosphate, and heme oxygenase. CONCLUSIONS: Although in the normal mouse, nitric oxide is an inhibitory neurotransmitter in the internal sphincter, other transmitters may play a role in the rectoanal inhibitory reflex. These other inhibitory neurotransmitters can apparently compensate for the absence of nitric oxide synthase in knockout mice to maintain approximately normal function.

Clinical features and differential diagnosis of diverticular disease.

Colonic diverticulosis occurs in the majority of Western populations with age, but only a small proportion of people experience symptoms. Diverticular disease usually presents with either haemorrhage or diverticulitis. A quarter of patients with diverticulitis will develop complications including perforation, fistulation, obstruction or stricture. This chapter deals with the natural history, risk factors, clinical features and differential diagnoses of symptomatic diverticular disease.

Recurrence after abdominal surgery for Crohn's disease: relationship to disease site and surgical procedure.

PURPOSE: We investigated the hypothesis that there is an "aggressive" subtype of Crohn's disease characterized by early recurrence and that disease location and surgical procedure are associated with differing patterns of recurrence. METHODS: We analyzed 280 patient records totaling 482 major abdominal operations from a prospectively compiled Crohn's disease database. Patterns of recurrence, as defined by reoperation, were analyzed by Kaplan-Meier plots and log-rank tests for the group as a whole, as well as according to disease location and operation performed using log-rank and Cox regression analysis. RESULTS: The overall survival curve followed a simple curve with no apparent early rise in recurrence. There was a significantly higher recurrence rate for ileal disease than for ileocolic or colic disease (median reoperation-free survival, 37.8 vs. 47.8 and 54.7 months, respectively; log-rank test = 13.6; P = 0.001), and there was a significantly shorter reoperation-free survival for those patients treated by strictureplasty alone or stricture-plasty combined with resection than for those treated by resection alone (41.7 and 48.6 vs. 51 months, respectively; log-rank test = 12; P = 0.002), but only disease site was confirmed as an independent risk factor for recurrence by multiple regression analysis. CONCLUSIONS: These data suggest that there is no evidence for the existence of a separate, early recurring, aggressive disease type. Shorter reoperation-free survival after strictureplasty may reflect patterns of recurrence in ileal disease.

The physiology, pharmacology and therapeutic manipulation of the internal anal sphincter.

Recent research into the physiology and pharmacology of the internal anal sphincter has elucidated the importance of this structure in health and disease. Its pharmacological manipulation for therapeutic gain has focused mainly on agents to reduce internal anal sphincter tone, a 'chemical sphincterotomy' that might heal chronic anal fissure. However, drugs to increase sphincter tone, and augment intermittent and appropriate relaxation are also being evaluated. The initial results with this medical approach to anorectal disease have often been disappointing, failing to match the results achievable with surgery, and many of these drugs have a high rate of side effects in the short term. However, clinical trials have yet to establish the optimum doses, dose intervals and routes of administration for many of these therapies. Furthermore, it is uncertain whether this medical approach should be applied to all patients or just to an as yet undefined subgroup. Certainly, even in the current environment of uncertainty, there is little reason not to try medical manipulation of the internal sphincter as first-line treatment. Surgery remains an option for treatment failures; patients responding to pharmacological manipulation of the internal anal sphincter are spared the long term risks of continence that are inherent in many surgical procedures on the anorectum.