Wednesday, August 1, 2007

Pancreas and Biliary Tree

Digestive Organs
Pancreas & Biliary Tree
The pancreas and bile duct (biliary) systems together form an important part of the digestive system. The pancreas and liver produce juices (pancreatic juice and bile) which help in the process of digestion – i.e. the breakdown of foods into parts which can be absorbed easily and used by the body).

The pancreas is about the same size and shape as a small banana, and lies in the upper abdomen, towards the back, near the spine. The pancreas is solid (the acinar tissues), and contains drainage tubes (the pancreatic ductal system). The pancreatic juices are made in the acinar tissues, and passed by secretion into the tubes (ducts) for transport into the second part of the upper small intestine (duodenum). The exit hole into the duodenum is called the papilla of Vater.

The biliary juices (bile) are made in the tissues of the liver (hepatic parenchyma), and then pass into the biliary ductal system (picture). Like a river, these ducts gradually join together to form one stream in the main bile duct, which exits (along with the pancreatic duct) into the duodenum at the "papilla of Vater." The gallbladder is a storage chamber for bile, joined to the side of the bile duct by another small tube – the cystic duct.

Anatomy

The anatomy (design) of the biliary and pancreatic ducts is not the same in every person. Variations can be important; some can cause medical problems, others may make treatment more difficult or complicated.




  • Papilla of Vater and Minor (Accessory) Papilla



    The main papilla of Vater (named after an Italian) is a small nipple-like structure on the wall of the duodenum, in its "second part." The duodenum is the upper part of the small intestine, into which food flows from the stomach.

    The papilla forms the main exit hole for the bile and pancreatic juices which flow down the bile duct and pancreatic duct. Rarely there are two separate holes close together within the same papillary nipple. The papilla remains closed at rest, because of the activity of a muscular valve (sphincter). The sphincter (of Oddi, another Italian) surrounds the exit of the bile duct and pancreatic duct. It opens by reflex action when foods enter the stomach, so that juices can be released to help in their digestion.

    In most people there is a second smaller (minor, or accessory) papilla, situated about 2 cm (3/4 inch) above the main papilla, and slightly to its right. This is the exit hole for Santorini's duct. The minor papilla acts as a useful safety valve when the main papilla is not able to function correctly, but becomes the main site of drainage for pancreatic juices in the rare congential disease of pancreas divisum.




  • Bile Duct System and Gallbladder

    The bile duct (biliary) system provides the channels through which bile is transported from the liver to the duodenum (through the papilla of Vater).

  • The liver is found in the right upper corner of the abdomen, immediately below the diaphragm. In health it weighs 3-4 pounds. It is divided into right and left lobes, and each of these have several segments. The bile ducts start as tiny tubes called sinusoids which lie between rows of liver cells called hepatocytes.

    These liver cells make bile, and pass it into the tiny canals (cannaliculi). The small ducts join together like branches to form the main biliary tree, with one trunk which is formed just outside the surface of the liver. This is called the common hepatic duct.

  • The gallbladder is a collection sac for bile, which enters and leaves through a narrow tube called the cystic duct. The gallbladder is about the size of an egg when full. The bile duct below the cystic duct is usually called the common bile duct. The common bile duct and the common hepatic duct together constitute the main bile duct. The lower end of the bile duct sweeps around behind the duodenum and the head of the pancreas before joining the pancreatic duct at the main papilla (of Vater).

  • Pancreatic Duct System

    There is a main pancreatic duct (named after Wirsung, another Italian) which collects juices from all the branches of the pancreatic stream, and exits at the main papilla of Vater. The pattern of these branches varies considerably, but this this does not matter. However, there is often another important duct (named after Santorini – yet another Italian). This connects the main pancreatic duct to another small papilla (the minor or accessory papilla) which is found about 2 cm (3/4 inch) above the main papilla of Vater in the duodenum.






    This (normal) arrangement comes about as a result of complex reorganization during fetal development. Early in the development of the embryo, the pancreas is in two parts (dorsal and ventral elements). These parts usually join together to form one pancreas between six and eight weeks of pregnancy. The duct systems of the two elements (dorsal and ventral) also join together for the "normal" anatomy. However, this fusion (joining) does not happen in about one in twelve people (at least in western populations). Then the pancreas remains divided (so called "pancreas divisum").

    The largest (dorsal) part of the pancreas drains through Santorini's duct and the minor papilla, while only a small part (the ventral pancreas) drains through the usual (major) papilla. The importance of this is that the minor papilla may be too small to allow easy passage of the pancreatic juices; and some patients with pancreas divisum can develop attacks of pain and pancreatitis as a result due to this relative narrowing.

    An unobstructive duct is still important even when the anatomy is normal and pancreas divisum does not exist. Thus, the patient who develops a problem at the main papilla (like a stone or tumor) may not develop any symptoms of pancreatic obstruction if Santorini's duct and the minor papilla are open, and can take over the drainage function.

    There are other rarer variations of pancreatic anatomy. Annular pancreas describes a congenital condition in which one of the branches of the pancreas swings all around the duodenum; this can narrow the duodenum sufficiently to cause obstruction and require operation. This condition usually presents in infancy (for obvious reasons), but can be discovered only later in life if the narrowing is not so tight, and sometimes when attacks of pancreatitis are associated with it. Other anomalies of pancreas development produce interesting pictures, but are not of clinical importance.

  • Function & Control

    The tissues of the pancreas (acinar cells) produce a clear digestive fluid made up of bicarbonate, and enzymes. Bicarbonate is alkaline, and helps digestion by neutralizing the stomach acid containing the food as it passes into the duodenum. The enzymes are more important. These are designed to help breakdown (digest) complex carbohydrates (sugars), proteins, and fats in the food. The main enzymes are called amylase, proteases (trypsin, chymotrypsin), and lipase. The enzyme and bicarbonate secretions together are called the "exocrine" function of the pancreas.

    The bile ducts function as a drainage system for the liver. Bile is a bitter dark fluid, composed of bile acids, bile pigments, bilirubin, cholesterol and other fats, water and electrolytes. Some of these constituents are useful for digestion, others are simply waste products (i.e. cholesterol).

    The gallbladder acts to store bile, and make it more concentrated by removing water. Although thin, the gallbladder wall has muscle tissue, so that it can contract and empty when necessary.

    Production of the bile and pancreas juices and their release into the duodenum through the papilla of Vater are controlled by abdominal nerves and also specific messengers (hormones) which pass to their targets through the bloodstream. These systems also control contractions of the gallbladder, and relaxation of the sphincter of Oddi (the muscular valve protecting the papilla of Vater). Together these insure that the juices are produced and released into the duodenum only when they are needed, that is when food arrives from the stomach ready for final digestion, and subsequent absorption.

    The pancreas also has an "endocrine" function – the production of insulin and other important hormones. These are produced in separate tissues within the pancreas (islets of Langerhans), and passed directly into the blood stream (rather than into the pancreatic duct). Insulin is very important for control of sugar levels in the blood; lack of insulin results in diabetes. The pancreas produces many other enzymes (such as somatostatin, pancreatic polypeptide, glucagon, etc.), the functions of which are of less immediate importance.

  • Dysfunction & Symptoms

    Pancreatic juices may not reach the duodenum if the duct or papilla is blocked, or if the pancreas is so damaged by disease that it cannot produce adequate bicarbonate and enzymes. Lack of pancreatic juices results in inadequate digestion. Clinically this is noteworthy by the passage of large bowel movements, which a strong odor and are difficult to flush down the toilet because of their high content of fat. Indeed, sometimes patients with pancreatic insufficiency may note an "oil slick" on the toilet water. Excessive fat in the stools is called "steatorrhea." Because food is not absorbed properly patients usually lose weight.

    These pancreatic enzymes can be replaced, at least to a certain extent, by giving them in the form of a medicine by mouth – so called pancreatic enzyme supplements. It is not usually necessary to replace the missing bicarbonate output.

    Lack of bile also interferes with digestion (particularly of fats) and can also result in steatorrhea. Lack of bile in the duodenum is usually due to blockage of the main bile duct, or papilla. The liver continues to produce bile, which then spills backwards into the blood stream. Eventually this causes yellow discoloration of the body (jaundice), first noticeable in the whites of the eyes. If bile does not enter the duodenum, bowel movements lose their usual color, and look like putty. When the bile ducts are blocked, retention of bile salts in the blood can result also in considerable itching (pruritus). Blockage of the bile ducts or pancreatic ducts can cause pain due to overdistention.

    Lack of insulin secretion by the pancreas results in diabetes. It is also possible to have too much insulin when the islets of Langohans overact, or become tumorous. This results in the blood sugar falling below normal levels, resulting in faintness and eventually coma. Lack or excess of other pancreatic hormones (such as somatostatin, vasoinhibitory peptide, glucagon, etc.) can cause unusual symptoms very rarely.

Page last updated February 8, 2007 .


http://www.ddc.musc.edu/ddc_pub/digestiveOrgans/pancBiliary.htm
Digestive Diseases - Public Information Site

Pancreas & Biliary Tree
The pancreas and bile duct (biliary) systems together form an important part of the digestive system. The pancreas and liver produce juices (pancreatic juice and bile) which help in the process of digestion – i.e. the breakdown of foods into parts which can be absorbed easily and used by the body).

The pancreas is about the same size and shape as a small banana, and lies in the upper abdomen, towards the back, near the spine. The pancreas is solid (the acinar tissues), and contains drainage tubes (the pancreatic ductal system). The pancreatic juices are made in the acinar tissues, and passed by secretion into the tubes (ducts) for transport into the second part of the upper small intestine (duodenum). The exit hole into the duodenum is called the papilla of Vater.

The biliary juices (bile) are made in the tissues of the liver (hepatic parenchyma), and then pass into the biliary ductal system (picture). Like a river, these ducts gradually join together to form one stream in the main bile duct, which exits (along with the pancreatic duct) into the duodenum at the "papilla of Vater." The gallbladder is a storage chamber for bile, joined to the side of the bile duct by another small tube – the cystic duct.

Anatomy
The anatomy (design) of the biliary and pancreatic ducts is not the same in every person. Variations can be important; some can cause medical problems, others may make treatment more difficult or complicated.

Papilla of Vater and Minor (Accessory) Papilla
The main papilla of Vater (named after an Italian) is a small nipple-like structure on the wall of the duodenum, in its "second part." The duodenum is the upper part of the small intestine, into which food flows from the stomach.

The papilla forms the main exit hole for the bile and pancreatic juices which flow down the bile duct and pancreatic duct. Rarely there are two separate holes close together within the same papillary nipple. The papilla remains closed at rest, because of the activity of a muscular valve (sphincter). The sphincter (of Oddi, another Italian) surrounds the exit of the bile duct and pancreatic duct. It opens by reflex action when foods enter the stomach, so that juices can be released to help in their digestion.

In most people there is a second smaller (minor, or accessory) papilla, situated about 2 cm (3/4 inch) above the main papilla, and slightly to its right. This is the exit hole for Santorini's duct. The minor papilla acts as a useful safety valve when the main papilla is not able to function correctly, but becomes the main site of drainage for pancreatic juices in the rare congential disease of pancreas divisum.

Bile Duct System and Gallbladder

The bile duct (biliary) system provides the channels through which bile is transported from the liver to the duodenum (through the papilla of Vater).

The liver is found in the right upper corner of the abdomen, immediately below the diaphragm. In health it weighs 3-4 pounds. It is divided into right and left lobes, and each of these have several segments. The bile ducts start as tiny tubes called sinusoids which lie between rows of liver cells called hepatocytes.

These liver cells make bile, and pass it into the tiny canals (cannaliculi). The small ducts join together like branches to form the main biliary tree, with one trunk which is formed just outside the surface of the liver. This is called the common hepatic duct.

The gallbladder is a collection sac for bile, which enters and leaves through a narrow tube called the cystic duct. The gallbladder is about the size of an egg when full. The bile duct below the cystic duct is usually called the common bile duct. The common bile duct and the common hepatic duct together constitute the main bile duct. The lower end of the bile duct sweeps around behind the duodenum and the head of the pancreas before joining the pancreatic duct at the main papilla (of Vater).

Pancreatic Duct System
There is a main pancreatic duct (named after Wirsung, another Italian) which collects juices from all the branches of the pancreatic stream, and exits at the main papilla of Vater. The pattern of these branches varies considerably, but this this does not matter. However, there is often another important duct (named after Santorini – yet another Italian). This connects the main pancreatic duct to another small papilla (the minor or accessory papilla) which is found about 2 cm (3/4 inch) above the main papilla of Vater in the duodenum. This (normal) arrangement comes about as a result of complex reorganization during fetal development. Early in the development of the embryo, the pancreas is in two parts (dorsal and ventral elements). These parts usually join together to form one pancreas between six and eight weeks of pregnancy. The duct systems of the two elements (dorsal and ventral) also join together for the "normal" anatomy. However, this fusion (joining) does not happen in about one in twelve people (at least in western populations). Then the pancreas remains divided (so called "pancreas divisum").

The largest (dorsal) part of the pancreas drains through Santorini's duct and the minor papilla, while only a small part (the ventral pancreas) drains through the usual (major) papilla. The importance of this is that the minor papilla may be too small to allow easy passage of the pancreatic juices; and some patients with pancreas divisum can develop attacks of pain and pancreatitis as a result due to this relative narrowing.

An unobstructive duct is still important even when the anatomy is normal and pancreas divisum does not exist. Thus, the patient who develops a problem at the main papilla (like a stone or tumor) may not develop any symptoms of pancreatic obstruction if Santorini's duct and the minor papilla are open, and can take over the drainage function.

There are other rarer variations of pancreatic anatomy. Annular pancreas describes a congenital condition in which one of the branches of the pancreas swings all around the duodenum; this can narrow the duodenum sufficiently to cause obstruction and require operation. This condition usually presents in infancy (for obvious reasons), but can be discovered only later in life if the narrowing is not so tight, and sometimes when attacks of pancreatitis are associated with it. Other anomalies of pancreas development produce interesting pictures, but are not of clinical importance.

Function & Control
The tissues of the pancreas (acinar cells) produce a clear digestive fluid made up of bicarbonate, and enzymes. Bicarbonate is alkaline, and helps digestion by neutralizing the stomach acid containing the food as it passes into the duodenum. The enzymes are more important. These are designed to help breakdown (digest) complex carbohydrates (sugars), proteins, and fats in the food. The main enzymes are called amylase, proteases (trypsin, chymotrypsin), and lipase. The enzyme and bicarbonate secretions together are called the "exocrine" function of the pancreas.

The bile ducts function as a drainage system for the liver. Bile is a bitter dark fluid, composed of bile acids, bile pigments, bilirubin, cholesterol and other fats, water and electrolytes. Some of these constituents are useful for digestion, others are simply waste products (i.e. cholesterol).

The gallbladder acts to store bile, and make it more concentrated by removing water. Although thin, the gallbladder wall has muscle tissue, so that it can contract and empty when necessary.

Production of the bile and pancreas juices and their release into the duodenum through the papilla of Vater are controlled by abdominal nerves and also specific messengers (hormones) which pass to their targets through the bloodstream. These systems also control contractions of the gallbladder, and relaxation of the sphincter of Oddi (the muscular valve protecting the papilla of Vater). Together these insure that the juices are produced and released into the duodenum only when they are needed, that is when food arrives from the stomach ready for final digestion, and subsequent absorption.

The pancreas also has an "endocrine" function – the production of insulin and other important hormones. These are produced in separate tissues within the pancreas (islets of Langerhans), and passed directly into the blood stream (rather than into the pancreatic duct). Insulin is very important for control of sugar levels in the blood; lack of insulin results in diabetes. The pancreas produces many other enzymes (such as somatostatin, pancreatic polypeptide, glucagon, etc.), the functions of which are of less immediate importance.

Dysfunction & Symptoms
Pancreatic juices may not reach the duodenum if the duct or papilla is blocked, or if the pancreas is so damaged by disease that it cannot produce adequate bicarbonate and enzymes. Lack of pancreatic juices results in inadequate digestion. Clinically this is noteworthy by the passage of large bowel movements, which a strong odor and are difficult to flush down the toilet because of their high content of fat. Indeed, sometimes patients with pancreatic insufficiency may note an "oil slick" on the toilet water. Excessive fat in the stools is called "steatorrhea." Because food is not absorbed properly patients usually lose weight.

These pancreatic enzymes can be replaced, at least to a certain extent, by giving them in the form of a medicine by mouth – so called pancreatic enzyme supplements. It is not usually necessary to replace the missing bicarbonate output.

Lack of bile also interferes with digestion (particularly of fats) and can also result in steatorrhea. Lack of bile in the duodenum is usually due to blockage of the main bile duct, or papilla. The liver continues to produce bile, which then spills backwards into the blood stream. Eventually this causes yellow discoloration of the body (jaundice), first noticeable in the whites of the eyes. If bile does not enter the duodenum, bowel movements lose their usual color, and look like putty. When the bile ducts are blocked, retention of bile salts in the blood can result also in considerable itching (pruritus). Blockage of the bile ducts or pancreatic ducts can cause pain due to overdistention.

Lack of insulin secretion by the pancreas results in diabetes. It is also possible to have too much insulin when the islets of Langohans overact, or become tumorous. This results in the blood sugar falling below normal levels, resulting in faintness and eventually coma. Lack or excess of other pancreatic hormones (such as somatostatin, vasoinhibitory peptide, glucagon, etc.) can cause unusual symptoms very rarely.


Disclaimer
The information contained within the MUSC's Digestive Disease Center web site is intended solely for general educational purposes. This site is not intended or implied to be a substitute for professional medical advise. Always seek the advice of your physician or other health care provider for any questions you may have regarding your medical condition. Any information offered by our physicians is solely out of courtesy and DOES NOT constitute a doctor-patient relationship between you and any physician and/or professional of the MUSC Digestive Disease Center.

The MUSC Digestive Disease Center does not warrant the accuracy, completeness, correctness, timeliness or usefulness of any information contained within this web site or links herefrom. In no event will the MUSC Digestive Disease Center be liable to you or anyone for any decision made or action taken by you or anyone else in reliance upon the information provided here.

Page last updated February 8, 2007 .


http://www.ddc.musc.edu/ddc_pub/digestiveProbs/diseases/pancBiliary/sphincterOddi.htm
Gallbladder Dysfunction (Biliary Dyskinesia)
Gallstones are the most common cause of gallbladder dysfunction and symptoms such as pain and infection (cholecystitis). However, sometimes the gallbladder can become inflamed and partially obstructed in the absence of stones. The normal gallbladder contracts through muscular activity in response to food, forcing bile through its exit channel (the cystic duct) and into the bile duct for passage into the intestine (through the sphincter of Oddi or the papilla of Vater). If these movements are not appropriately coordinated, the pressure can rise and result in gallbladder type pain.

In this condition, the gallbladder may appear normal on the standard ultrasound scan; abnormalities are only detected when the gallbladder is stimulated to contract, with food or after an injection of a stimulating hormone (cholecystokinin – CCK). Failure of the gallbladder to contract properly, especially if the patient's pain is reproduced, is good evidence of gallbladder dysfunction. This can also be investigated by a special type of isotope scan (HIDA scan) during which the behavior of the bile can be watched and the emptying of the gallbladder measured (the ejection fraction). Patients with clearcut symptoms and positive test results respond well to removal of the gallbladder (laparoscopic cholecystectomy).

Papillary Stenosis: Sphincter of Oddi Dysfunction The sphincter of Oddi is the muscular valve surrounding the exit of the bile duct and pancreatic duct into the duodenum, at the papilla of Vater. The sphincter is normally closed, opening only in response to a meal so that digestive juices can enter the duodenum and mix with the food for digestion.

Sphincter of Oddi dysfunction and papillary stenosis are conditions which occur when this sphincter (opening) mechanism is disturbed. When the hole is too tight, there is a backup of bile and pancreatic juices. This can cause pain (biliary colic). More prolonged obstruction may result in bile leaking back into the blood stream, resulting in abnormalities of the liver function tests, or even yellow jaundice (discoloration of the eyes and skin). Also, blockage to the pancreatic orifice can cause pancreatic pain or attacks of pancreatitis.

Papillary Stenosis can be caused by passage of stones, or scarring after treatments (i.e. endoscopic or surgical sphincterotomy). Papillary stenosis usually results in sufficient backup of bile flow that there is stretching (dilatation) of the bile duct. This can be recognized by scans and various x-rays, including ERCP. Papillary stenosis requires endoscopic or surgical treatment. The hole is enlarged by cutting, to improve drainage. Occasionally it is necessary to do a surgical bypass (choledochoduodenostomy, or Roux-en-Y hepaticojejunostomy) to insure that drainage is effective.

Spasm of the Sphincter
This is a more difficult problem. It may be one manifestation of other muscular spasm problems in different areas of the body (such as the esophagus or intestine – irritable bowel syndrome). However, in some patients, it is the prevailing complaint, and requires focal attention. The pain symptoms are very similar to those caused by bile duct or gallbladder stones. Indeed, sphincter of Oddi dysfunction most frequently occurs in patients who have previously undergone removal of the gallbladder (cholecystectomy). Some patients present with unexplained attacks of acute pancreatitis when the pancreatic sphincter is involved predominantly.

Diagnosis of sphincter of Oddi Dysfunction
Initially, tests are aimed to make sure that there are no stones present. Standard ultrasound and CT scans are not very accurate in detecting or excluding bile duct stones; newer techniques such as MRCP and endoscopic ultrasound (EUS) are more sensitive, but not yet widely available. Most patients are investigated with ERCP. The doctor can examine the drainage hole of the bile duct at the papilla of Vater, and inject dye into the bile duct and pancreatic duct to look for stones and other forms of obstruction. The possibility of sphincter spasm (dysfunction) is considered only when these other conditions have been excluded. Dysfunction can be recognized by a special technique during ERCP, called sphincter of Oddi manometry (SOM). This involves passing a small catheter (tube) into the bile duct and pancreatic duct, to measure the squeeze pressure.

Treatment of Sphincter of Oddi Dysfunction
Antispasm medicines are available, but are not very effective. A decision has to be made whether to cut the sphincter (sphincterotomy), during ERCP, or at surgery. When sphincter of Oddi manometry has confirmed that the pressures are high, sphincterotomy gives complete relief in 70-80% of patients; unfortunately, sphincterotomy also carries a significant risk of complications in this context, particularly the provocation of pancreatitis, and the possibility of perforation. Thus, this condition should be approached and managed with considerable care. Patients may warrant referral to specialist centers.

Sphincterotomy procedures can sometimes scar after months or years, causing papillary stenosis. Further cutting (repeat sphincterotomy) is sometimes possible, but there are limits; surgical bypass may be necessary.

Attempts have been made to treat sphincter of Oddi dysfunction without sphincterotomy – by placing a temporary plastic splinting tube (stent), or by an injection of botulinum toxin, which paralyzes the sphincter. These treatments are experimental.

Page last updated February 8, 2007.

Disclaimer
The information contained within the MUSC's Digestive Disease Center web site is intended solely for general educational purposes. This site is not intended or implied to be a substitute for professional medical advise. Always seek the advice of your physician or other health care provider for any questions you may have regarding your medical condition. Any information offered by our physicians is solely out of courtesy and DOES NOT constitute a doctor-patient relationship between you and any physician and/or professional of the MUSC Digestive Disease Center.

The MUSC Digestive Disease Center does not warrant the accuracy, completeness, correctness, timeliness or usefulness of any information contained within this web site or links herefrom. In no event will the MUSC Digestive Disease Center be liable to you or anyone for any decision made or action taken by you or anyone else in reliance upon the information provided here.


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