Mod 6 notes - Brent DMS Abdo 1120 Anatomy PDF

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Brent DMS Abdo 1120 Anatomy...

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Anatomy, Physiology and Sonography of the Gallbladder and Biliary System

Preamble Gallbladder disease is a prevalent illness in our culture. Right upper quadrant pain leads physicians immediately to think of gallbladder disease, among other things. This module will educate you in the realms of normal gallbladder anatomy, physiology, and sonography. We will explore a few pathogenic processes involved in gallbladder and biliary disease. By the end of this unit, you should be able to view an ultrasound image of a gallbladder and / or the biliary tree, and decide whether it is normal or abnormal. Consider the following scenario A 38-year-old woman went to her in-laws for Thanksgiving dinner. After a fun-filled evening, she begins to feel a crampy feeling in her abdomen and deciding that she must have overindulged, she goes home. While at home her pain worsens, and now she feels the pain in her back. She holds the area under her right ribs, although it seems to hurt when she presses here. She struggles to make it to the bathroom to vomit, and takes a Tylenol for her fever. After a couple hours of this, she tells her husband that she needs to go to the hospital. The emergency room physician performs a physical examination on her, and orders some lab tests. Her white blood cell count is high, as is her Alkaline phosphatase and bilirubin. He orders an abdominal ultrasound. What will you look for?

In terms of biliary anatomy, we left off at the liver lobule. The liver cells are busy making bile and passing it to the bile cannaliculi. The cannaliculi all converge to either the right or left hepatic ducts. This occurs intrahepatically. The right and left hepatic ducts merge together to become the common hepatic duct. This occurs extrahepatically. The gallbladder is drained via the cystic duct, which merges with the common hepatic duct to become the common bile duct.

Gallbladder Anatomy • • • • •

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The normal gallbladder is approximately 8-12 cm long and 3-5cm in diameter in an adult It is a pear, or teardrop shaped sac with walls no more than 3mm think when distended Typical bile capacity is 30-60 ml It is located at the caudal end of the main lobar fissure It lies in the gallbladder fossa in the visceral surface (inferior and posterior) of the liver. Lateral to the second part of the duodenum and anterior to the right kidney and transverse colon It is predominantly intraperitoneal with the visceral peritoneum covering the fundus completely but only partially covering the body and neck

The gallbladder has 3 component parts: the neck, body and fundus

Kawamura, D., & Lunsford, B. (2012). Diagnostic Medical Sonography: Abdomen and Superficial Structures. (3rd ed). Baltimore, MD: Lippincott Williams & Wilkins. Page 167. Figure 6-2

FUNDUS • • •

Position can vary In the supine position it is usually inferolateral to the liver In the decubitus position it will tend to be more midline, and if there were any folds, they sometimes straighten out

BODY • •

Is the central or main portion Is in contact with duodenum and transverse colon

NECK • •

• •

The narrowest portion. Also, the most superior portion of the gallbladder. The neck of the gallbladder is quite consistent in position and moves very little. o Lies to the right of the porta hepatis. o Continuous with the cystic duct Mucus membrane lines the neck and projects into the lumen of the gallbladder spiral valves of Heister (Heister valves). Hartmann’s pouch is a sac-like portion of the neck (looks like the heel on at foot) and may be a site of bile stasis

Histologically there are 3 layers to the gallbladder. We learn these layers because in the next section we talk about different "ducts" within the gallbladder wall, which are arranged in these layers.

1. An inner epithelial mucosa (continuous with that of the duodenum) 2. Fibromuscular layer 3. And an outer serosal surface (which is the visceral peritoneum).

Kawamura, D. (1997). Diagnostic Medical Sonography, A guide to Clinical Practice: Abdomen and Superficial Structures. (2nd ed). Philadelphia, PA: Lippincott-Raven. Page 192. Figure 6-1 (Cropped)

There are 3 types of ducts within the gallbladder wall: Ducts of Luschka • •

Do not communicate with the lumen of the gallbladder, but may sometimes connect to the bile ducts. They are sites for inspissation (becoming thicker or more viscous) of bile, as well as stasis of bacteria and debris, therefore may contribute to instances of inflammatory disease of the gallbladder

Rokitansky-Aschoff sinuses (inflammatory pseudodiverticulum) • • •

Small outpouchings of the mucosa of the gallbladder that extend into the underlying connective tissues and sometimes the muscular layer Occasionally found in normal gallbladders, but are more often found in diseased ones (see adenomyomatosis) May be the result of tissue injury, or just the result of mucosal herniation through a point of muscular weakness

Neck glands •

These are mucous glands found only in the neck of the gallbladder

CYSTIC DUCT ANATOMY • • • •

Connects the gallbladder to the common hepatic duct to form the common bile duct Is 3-4 cm in length Inner diameter is approximately 3 mm Also contains heister valves which prevent collapse or overdistention because of sudden positional changes

COMMON BILE DUCT ANATOMY

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When the cystic duct and the common hepatic duct (aka hepatic duct proper) (CHD) unite it is now called the common bile duct (CBD)

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The CBD courses inferiorly along the right border of the lesser omentum, then along the hepatoduodenal ligament and posterior to the first part of the duodenum into a groove near the posterolateral aspect of the head of the pancreas just anterior to the IVC In some cases, it is surrounded by pancreatic tissue As the Common duct travels through the head of the pancreas, it meets up with the main pancreatic duct forming the hepatopancreatic duct. Together they empty through the papilla of Vater (a protrusion of mucosal lining) into the duodenal lumen at the sphincter of Oddi (a circular muscle surrounding the lower part of the bile duct, ampulla and terminal part of the pancreatic duct). It is commonly accepted that the maximum diameter of the CBD is 4mm up to the age of 40, and thereafter one mm may be added for each decade of life The CBD may be slightly dilated post cholecystectomy

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BLOOD SUPPLY AND INNVERVATION TO THE GALLBLADDER:

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Gallbladder is supplied mostly by blood from cystic artery (branch of right hepatic artery)

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Blood from the gallbladder is drained mostly through the portal venous system Innervation: o o Coeliac Plexus (sympathetic Nervous system) o o Vagus Nerve (parasympathetic nervous system) o o Nerve fibers from right phrenic nerve reach the gallbladder causing referred shoulder pain associated with extrahepatic biliary diseases

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Physiology of the Gallbladder and bile ducts The function of the gallbladder is to concentrate and store bile, which is manufactured by the hepatocytes. Bile enters the gallbladder by travelling up the cystic duct. When a person eats, and the food reaches the small intestine, a hormone called cholecystokinin (CCK) is secreted by the small intestine. This causes 2 effects: 1. relaxation of the sphincter of oddi 2. contraction of the gallbladder Bile enters the cystic duct, then the common bile duct and enters the duodenum via the ampulla of Vater.

Note: The lab tests pertinent to gallbladder and biliary disease are those that we've already mentioned in our liver unit (alkaline phosphatase, AST, ALT, LDH, Bilirubin, WBC)

Sonography of the Gallbladder and Biliary Tree Patient Preparation and Scanning Technique for the Gallbladder and Biliary System • •

Patient should be fasting which allows greater distention of the gallbladder and better demonstration of the extrahepatic ductal system Adults usually fast 12 hours (overnight) and kids should fast 6-8 hours

The examination usually begins with the patient supine. One may identify the gallbladder in the caudal aspect of the main lobar fissure. Once the longitudinal lie of the gallbladder has been established, the organ is then scanned slowly from medial to lateral borders. Then the transducer is rotated 90 degrees so that the gallbladder can be scanned from fundus to neck transversely. Once supine scans have been completed, the patient is turned into the left lateral decubitus position. There are two main reasons for altering the patient’s positions:

1. To change the position of the gallbladder, thereby improving visualization 2. To alter the position of the contents of the gallbladder. You may use the prone and upright positions as well.

It is necessary to determine whether the contents (if present) of the gallbladder are mobile or not. Stones are usually mobile while tumors and polyps are usually not (unless attached by a long pedicle). If there is an immobile mass present, the wall of the gallbladder must be very carefully evaluated to see if the mass disrupts the gallbladder wall.

Transducer frequency and placement of the focal zone should always be matched to the patient habitus and the depth of the gallbladder. If stones are suspected, the sonographer should ensure that the stones are placed in the focal zone of the beam. One of the chief diagnostic criteria for gallstones is their ability to cast a shadow. For this reason, it is crucial that a shadow be elicited distal to the stone if at all possible. Some tiny stones may not shadow. The image below demonstrates proper focal zone focusing on the stone (a) which would show a shadow most definitely. The other 3 (b,c and d) show how when the focal zone is not adjusted right at the proper level, or if the stone is too small, a shadow may not be seen.

Bates, J. (2004). Abdominal Ultrasound: How, Why and When. (2nd ed). Philadelphia, PA:. Elsevier - Churchill Livingstone. Pg. 43.

TIPS: • • •

Smoking, chewing gum and coffee may all cause gallbladder contraction Landmarks to find the gallbladder = portal vein, right kidney, and MLF Reasons for non-visualization of the GB are o Agenesis (rare) o Vermiform GB (tube-like) o Patient ate o Gallbladder removed

Sonographic Appearance of the Normal Gallbladder and Biliary System. •

The normal gallbladder lumen is anechoic, ellipsoidal and is placed on the inferomedial aspect of the right lobe of the liver.

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Although the position is quite variable, it is most often seen in the region of the junction of the right and left lobes of the liver, at the distal end of the main lobar fissure. While the fundal position of the gallbladder can vary immensely, the neck is virtually always related to the main lobar fissure and the right portal vein. The image below shows this. The echogenic line is the main lobar fissure running between the gallbladder neck and the right portal vein (which is seen in cross-section).

Kawamura, D., & Lunsford, B. (2012). Diagnostic Medical Sonography: Abdomen and Superficial Structures. (3rd ed). Baltimore, MD: Lippincott Williams & Wilkins. Page 166. Figure 6-1

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The gallbladder is classically described as lying just anterior and medial to the right kidney. The image below is a transverse right image, displaying the relationship of the gallbladder to the right kidney.

Curry, R., & Tempkin, B. (2011). Sonography: Introduction to Normal Structure and Function. St. Louis, MO: Elsevier. Page 230. Figure 13-8.

In its distended state, the gallbladder wall should be smooth and not significantly thick. (Normal is up to 3mm). •

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The gallbladder may be significantly dilated in diabetic patients, bedridden patients, patients with pancreatitis and patients who are taking anticholinergic drugs. (These drugs block the passage of impulses through the parasympathetic nerve fibers). The gallbladder should always be less than 4 cm in axial section. Heister valves may cause shadowing thereby causing confusion with gallstones impacted in the cephalic aspects of the gallbladder and the distal cystic duct.

The Common Bile Duct In longitudinal section, the common bile duct can be seen as a small anechoic tubular structure anterior to the main portal vein. The image below shows the CBD in its classic orientation to the main portal vein. The circular structure between the two is the right hepatic artery. Most people have this configuration of the 3 tubes (top image), however a small percentage (approximately 15%) have a variant where the right hepatic artery is anterior to the common bile duct (bottom image).

Stocksley, M. (2001). Abdominal Ultrasound. San Francisco, CA:. Greenwich Medical Media. Pg. 69

The image below demonstrates the correct caliper placement for measureing the CBD. Note that the calipers are placed "inner wall to inner wall" just distal to the right hepatic artery.

Kawamura, D., & Lunsford, B. (2012). Diagnostic Medical Sonography: Abdomen and Superficial Structures. (3rd ed). Baltimore, MD: Lippincott Williams & Wilkins. Page 172. Figure 6-6 B

When measuring, we want to ensure that we are indeed measuring the CBD and not the common hepatic duct (CHD). While it is impossible to determine the exact point of transition of the CHD to the CBD the general rules are: 1. The CHD is superior to the gallbladder and the CBD is seen inferior to the gallbladder 2. The CHD is the portion of the duct before the hepatic artery crosses the portal vein, and the CBD is the portion of the duct after the hepatic artery crosses the portal vein. The image below demonstrates the anatomical location of these areas.

Kawamura, D., & Lunsford, B. (2012). Diagnostic Medical Sonography: Abdomen and Superficial Structures. (3rd ed). Baltimore, MD: Lippincott Williams & Wilkins. Page 170. Figure 6-6 D

The CBD is also demonstrated within the “Mickey mouse” sign, anterior and to the right of the patient. (refer to your liver notes for this image) Further down the common duct can be seen either on the lateral or posterior aspect of the head of the pancreas. The cystic duct is not usually visualized, but if you are trying to see it, you might want to try the Trendelenburg position (head lowered, and feet raised).

Remember: The commonly accepted rule for normal diameter of the common bile duct is as follows: Up to the age of 40, the maximum internal diameter should be no more than 4mm A/P. After the age of 40, the normal diameter can be increased by 1mm for every decade; this means that a person in their 50’s can have a maximum internal diameter of 5mm and up to 6mm for a person in their 60’s. There is a limit to this, however, no matter how old a person is, a common duct measuring 7mm or more should be considered highly suspicious for being pathologic.

Learning activities Read Chapter 15 in Curry and Tempkin Look at the pertinent paragraphs in chapter 24 of Tortora Have a look on the internet for anatomy tutorials

Self-Assessment Quiz Complete the quiz to cement your learning

References 1. Rumack, C., Wilson, S., Charboneau, J., & Levine, D. (2011). Diagnostic Ultrasound. (4th. ed.). Philadelphia, PA.: Elsevier. 2. Curry, R., & Tempkin, B. (2016). Sonography: Introdcution to Normal Structure and Function. (4th ed.). St. Louis, MO.: Elsevier. 3. Kawamura, D., & Lunsford, B. (2012). Diagnostic Medical Sonography: Abdomen and Superficial Structures. (3rd ed). Baltimore, MD: Lippincott Williams & Wilkins. Chapter 6. 4. McConnell, T., & Hull, K. (2011). Human Form, Human Function: Essentials of Anatomy and Physiology. Baltimore, MD: Lippincott Williams & Wilkins. Chapter 14. 5. Tempkin, B. (2009). Ultrasound Scanning: Principles and Protocols. (3rd ed). St. Louis, MO: Elsevier. Chapter 7. 6. Bates, J. (2004). Abdominal Ultrasound: How, Why and When. (2nd ed.). Philadelphia, PA:. Elsevier, Churchill Livingstone 7. Stocksley, M. (2001). Abdominal Ultrasound. San Francisco, CA:. Grenwich Medical Media. 8. Kawamura, D. (1997). Diagnostic Medical Sonography, A Guide to Clinical Practice: Abdomen and Superficial Structures. (2nd ed). Philadelphia, PA:. Lippincott-Raven. 9. http://25.media.tumblr.com/tumblr_lvr6aoI68W1qk3rzjo1_500.jpg. Public Domain 10. http://2.bp.blogspot.com/SFrxrkyF3d4/TzLTxLfN5pI/AAAAAAAAF8Y/0_xrr6QhiIY/s640/Hirsh+ant+gb+wall+measureme nt.jpg. Public Domain 11. www.ultrasound-images.com/gall-bladder.htm. Public Domain...