The mucosal lining of the intramural common bile duct as a determinant of ductal opening pressure

A Randomized Trial of Topical Epinephrine and Rectal Indomethacin for Preventing Post-Endoscopic Retrograde Cholangiopancreatography Pancreatitis in High-Risk Patients

INTRODUCTION

Rectal indomethacin and topical spray of epinephrine have separately shown efficacy in the prevention of post-endoscopic retrograde cholangiopancreatography pancreatitis (PEP) in randomized controlled trials. We hypothesized that the combination of indomethacin and topical spray of epinephrine on the duodenal papillae would further reduce PEP than when indomethacin was used alone.

METHODS

We conducted a comparative effectiveness, multicenter, double-blinded, randomized trial of rectal indomethacin alone vs a combination of rectal indomethacin and topical spray of epinephrine for the prevention of PEP in high-risk patients. The primary outcome was the incidence of PEP and the secondary outcome was the severity of PEP. A 2-tailed Fisher's exact test was used to analyze the difference in the proportion of patients with PEP in the indomethacin alone vs the combination group.

RESULTS

A total of 960 patients (mean age 52.33 ± 14.96 years; 551 [57.4%] females) were randomized and 959 completed follow-up. The baseline demographic and clinical characteristics were similar between the 2 groups. Women <50 years of age (25.4%) and difficult cannulation (84.9%) were the most common PEP risk factors. The incidence of PEP was 6.4% in the indomethacin alone group (n = 482) compared to 6.7% in the combination group (n = 477; P = 0.87). Severe PEP was found in 5 (12%) and 7 (16%) patients in the indomethacin alone and combination groups, respectively (P = 0.88). The overall mortality was 0.6%, which was unrelated to the primary outcome.

CONCLUSIONS

The combination of rectal indomethacin and topical spray of epinephrine does not reduce the incidence of PEP compared to rectal indomethacin alone in high-risk patients; https://clinicaltrials.gov/ct2/show/NCT02116309.

The mucosal folds at the pancreaticobiliary junction

PURPOSE

The structure and function of the mucosal folds in the terminal bile and pancreatic ducts and hepatopancreatic ampulla are poorly characterised. The distribution, muscularity, and innervation of these folds were investigated.

METHODS

The pancreaticobiliary junction was excised from ten cadavers (five male, 66-90 years) and examined histologically by serially sectioning (4-μm thickness) along the length of the terminal bile and pancreatic ducts from the tip of the major duodenal papilla. Three surgical specimens (two male, 63-72 years) were also evaluated. Sections were stained with haematoxylin and eosin, anti-actin (smooth muscle), anti-S100 (innervation), and anti-cholecystokinin (CCK)-A receptor antibodies. ImageJ software was used to compare relative radial fold projection and semi-quantitatively assess the smooth muscle and nerve content. In one additional cadaver specimen, folds were examined by scanning electron microscopy.

RESULTS

Mucosal folds in the terminal bile duct were arranged circumferentially in a lattice-like arrangement and were distributed over an average distance of 7.3 mm along the terminal bile duct compared to 4.2 mm along the pancreatic duct (P = 0.001), projected further into the lumen, and were more densely innervated than those in the terminal pancreatic duct. Folds in both ducts contained smooth muscle which was more prominent in folds nearest to the major duodenal papilla. Mucosal folds in cadaver and surgical specimens showed no evidence of CCK-A receptor immunoreactivity.

CONCLUSIONS

This study demonstrates that the mucosal folds of the terminal bile and pancreatic ducts contain muscle and nerve fibres, suggesting an active rather than purely passive function.

A series of six cases of sphincter of Oddi pathology in the cat (2008–2009)

The sphincter of Oddi (SO) is located within the wall of the duodenum as the terminal part of the common bile duct. Six cats are reported with obstructive processes within their SO. Three of them may have had some form of sphincter dysfunction associated with the pre-existing complex known as ‘inflammatory bowel disease’ (IBD), two may have had the equivalent of the infant human condition known as ‘bile plug syndrome’ and the sixth had sphincter dysfunction associated with a tumour at the confluence of the common and right hepatic duct. In all six cases, the sphincter obstructions were surgically managed. The outcomes for 4/6 were favourable but 1/6 was euthanased intraoperatively, and 1/6 had a metastatic neoplasia and was euthanased 2 months postoperatively.

Galanin modulates sphincter of Oddi function in the Australian brush-tailed possum

The neuropeptide galantin (GAL) is found in neurons in the biliary tract of several species. We mapped the distribution of GAL-like immunoreactive nerve (GAL-LI) fibers in the sphincter of Oddi of the Australian brush-tailed possum by immunohistochemistry. The pharmacological effects of GAL in vitro and in vivo were studied by measuring sphincter of Oddi muscle strip contractility and transsphincteric flow, respectively. Muscle layers, and ganglionated and perivascular plexuses, contained GAL-LI nerve fibers. Exogenous GAL caused a concentration-dependent (10(9)-10(-6)M) increase in the spontaneous longitudinal but not circular muscle contractions. At 10(-6) M GAL, contractile activity was elevated two- to fourfold. This response was tetrodotoxin insensitive but competitively inhibited by galantide (10(-8)-10(-7) M). In vivo, intra-arterial bolus injections of GAL (1001000 ng/kg), decreased transsphincteric flow, with a maximum reduction to 80.2 +/- 6.8% of control. In conclusion, GAL appears to selectively stimulate longitudinally oriented sphincter of Oddi smooth muscle via a direct mechanism, which results in a modest reduction in transsphincteric flow.

Anatomy of the bilioduodenal junction of the opossum

Prevention of reflux is a major function of the terminal biliary duct system at its junction with the duodenum. We examined this area via scanning electron microscopy and light microscopy to explore anatomic features that might play such a role in the Virginia opossum, a species with a highly developed sphincter of Oddi (SO). The terminal apparatus, most of which consists of a dilated extramural ampulla, has a lumen with abundant folds. Mucus is produced by the lining epithelium and by a plethora of glands. Three muscle layers constitute the SO: an inner longitudinal, an outer circular, and a less consistent outermost longitudinal. The terminal apparatus forms an acute angle and narrows as it enters the duodenum; at this point, the SO becomes continuous with the muscularis externa of the intestine. Four anatomical features with potential antireflux properties may be identified: mucus production, luminal folds, and the narrow opening and oblique course of the intramural duct.

Biliary tract motor dysfunction

Gallbladder and sphincter of Oddi motility regulates the flow of bile from the liver to the duodenum. During the interdigestive period most secreted bile is diverted into the gallbladder where it is concentrated, but a significant minority of the biliary secretion passes directly into the duodenum. Regulation of this flow is mainly via the phasic contractions of the sphincter of Oddi and the sphincter basal tone. The phasic contractions expel small volumes of fluid into the duodenum, but most of the flow occurs between the contractions and is therefore not dependent on peristaltic pumping, but rather on a small pressure gradient. During fasting, just prior to duodenal phase III activity, the gallbladder expels up to 40% of its volume and the sphincter phasic contractions increase. Following a meal, the gallbladder empties its contents, and the sphincter of Oddi resistance is reduced via a fall in basal pressure and inhibition of the amplitude of phasic contractions. Control of this activity is via an interplay of both neuronal and hormonal factors which together have an effect on both gallbladder and sphincter of Oddi motility. Abnormalities in motility are recognized for both the gallbladder and the sphincter of Oddi. Gallbladder dyskinesia is objectively diagnosed using the radionuclide GBEF. In patients with a GBEF less than 40% cholecystectomy results in relief of symptoms. In postcholecystectomy patients sphincter of Oddi dysfunction presents as either biliary-like pain or idiopathic recurrent pancreatitis. Endoscopic sphincter of Oddi manometry provides the most objective diagnostic information. In patients with a sphincter of Oddi stenosis, characterized manometrically as an elevated basal pressure, division of the sphincter results in relief of symptoms. For patients with biliary-like pain, division is performed as an endoscopic sphincterotomy, whereas for patients with idiopathic recurrent pancreatitis, a sphincteroplasty and pancreatic duct septectomy are required.

Innervation of the sphincter of Oddi: physiology and considerations of pharmacological intervention in biliary dyskinesia

The sphincter of Oddi is a small sphincter which is strategically placed at the junction of the bile duct and pancreatic duct with the duodenum. It regulates the flow of bile and pancreatic juice into the duodenum and prevents reflux of duodenal contents into the ducts. The structure of the sphincter of Oddi differs from species to species and consequently its physiological action varies in different species. Anatomical and immunohistochemical investigations have demonstrated that the sphincter of Oddi is richly innervated by cholinergic, adrenergic and peptidergic neurons. In addition, neural connections exist between the sphincter, gallbladder and proximal gastrointestinal tract. These nerves in addition to hormones are important in the control of sphincter of Oddi motility and function. The normal human sphincter of Oddi is characterized by prominent phasic contractions which are superimposed on a modest basal pressure. These contractions are present throughout the interdigestive period. The contractions and basal pressure are inhibited by ingestion of a meal or infusion of cholecystokinin octapeptide, thus enhancing the flow of bile and pancreatic juice into the duodenum. Sphincter of Oddi dysfunction has been described in patients who present with recurrent biliary type pain and no evidence of a structural cause for the pain. Motility disorders characterized as an elevated basal pressure, rapid contraction frequency, paradoxical response to cholecystokinin octapeptide or excess of retrograde contractions have been identified. A number of pharmacologically active substances have been used in an attempt to treat these patients. Such pharmaceuticals include nitrites, Ca2+ channel blockers and smooth muscle relaxants. Their effect is transient and side effects relating to cardiovascular actions preclude their longterm use. Division of the sphincter either endoscopically or by open operation has been demonstrated by prospective clinical trials to be the most efficacious treatment for patients with a stenosed sphincter manometrically demonstrated by a high basal pressure. Improved understanding of the controlling mechanisms of sphincter of Oddi motility and the pathophysiology of sphincter of Oddi dysfunction should assist in the development of effective pharmacotherapy for these disorders.

Percutaneous antegrade electropapillotomy. Study in dogs

Antegrade electropapillotomy using the percutaneous transcystic approach was successfully performed in 11 of 16 dogs. When the intervention was effective, the pressure gradient between common bile duct and duodenum decreased from 6 to 1.3 mm Hg on average and returned to gradients slightly below the initial values after 4 weeks, owing to reactivation of the sphincter mechanism. Ineffective cutting, however, resulted in a temporary pressure rise. In one dog a papillary stenosis developed and was relieved by antegrade electrocutting. Irrespective of the success of the papillotomy, rises in levels of serum glutamine oxaloacetic and pyruvic transaminase, alkaline phosphatase, serum amylase and leukocytes were seen. Although the method is technically feasible, its clinical significance is not so much for antegrade papillotomy but rather for transhepatic incision of stenoses after hepaticojejunostomy.

A hydraulic behavior of the mucosal structure of the intramural common bile duct. An experimental study

In the intramural portion of the common bile duct in the dog, the lumen is occluded by the mucosal folds which are pointed to the direction of the ductal orifice. Luminal occlusion by the folds becomes more marked from the halfway of the portion as judged from the duodenal muscle layers. A pressure study using the pressure ramp apparatus suggested that the mucosal structure plays some role in generating the passage resistance to bile floow and in the prevention of regurgitation of duodenal content.

Radiology of papilla of Vater stenosis

The radiographic characteristics of the terminal pancreatic and biliary ducts were analyzed by endoscopic retrograde cholangiopancreatography in 25 patients with documented benign stenosis of the papilla of Vater. Demonstration of marked hypertrophy of the distal sphincter, mucosal hyperplasia or mucosal redundancy of the distal common bile duct, dilatation of the ducts, and prolonged retention of contrast media suggest papillary stenosis. The diagnosis of benign papillary stenosis, however, ultimately depends on physiologic measurements and response to therapy.

A functional description of the canine choledochoduodenal flutter valve

Forward- and reverse-opening pressures of the choledochoduodenal junction were measured in anesthetized, vagotomized dogs. Mean reverse-opening pressures were found to be significantly greater in most cases including those following the intraductal administration of vasoactive agents which are known to significantly influence mean forward-opening pressures. The polypeptides CCK-PZ and CCK-C8 were ineffective in reducing mean forward-opening pressures regardless of the route of administration. Previously published observations have indicated that mean forward-opening pressures are also unaffected by nervous activity. It is concluded that the canine choledochoduodenal junction possesses the physical and functional properties of a passive flutter valve during duodenal relaxation.