1. Lower GI
Anatomy, Pathology, and Radiography of the Lower GI Tract & Accessory Organs
All images copyright Mosby Inc., an affiliate of Elsevier Inc.

2. The Continued Saga of Bite
Anatomy
The Continued Saga of Bite
Chyme was last seen in the small intestine. The digestive process continues in the large intestine, also known as the colon. Chyme buys a ticket to get on this 5-foot-long ride at the ileocecal valve. This is where the small intestine’s ileum meets the large intestine’s cecum. As Chyme enters the cecum, he looks to the left. The cecum is shaped like a cul-de-sac with one narrow driveway leading nowhere. This driveway is the vermiform appendix. Instead, Chyme turns to the right. No longer surrounded by the rugae of the stomach or the villi of the small intestine, Chyme experiences a new adventure. Strong muscular bands create series of pouches called haustra. Peristalsis contractions help to push Chyme up the ascending colon, make a sharp corner at the right colic flexure; traverse the transverse colon; make another sharp corner at the left colic flexure, and slide down the descending colon to the sigmoid colon. As Chyme makes this journey, fluid is reabsorbed through the 4-layer walls of the colon. He transitions his identity one last time. His last alter ego is Feces. The final act of the large intestine is to squeeze the waste out of the body. So, with one last s-curve, up into the rectum and down through the anal canal Feces goes. When it is time, the anal sphincter will allow what’s left of him to be evacuated.

3. Habitus Affects Colon’s Position
Anatomy
Habitus Affects Colon’s Position
Body habitus influences the stomach’s location. The colon’s whereabouts is determined the same way.
You have seen pictures in textbooks that show where large intestines are normally found. Remember that 15% of the population deviates substantially from those pictures. A hypersthenic person’s colon will have a high transverse colon. An asthenic patient will have a colon that is bunched together down low in the abdomen. Again, this knowledge will help develop your x-ray vision. You will have an idea where organs are according to the patient’s body habitus.

4. A Few of the Accessory Organs
Anatomy
A Few of the Accessory Organs
When you hear the word “gland”, do you think of the swollen section of your neck when you are sick? The largest gland in the body is often thought of as an organ. Do you know what it is? Here’s a hint. It is wedge-shaped and takes up almost all of the right hypochondrium and lots of the epigastrium. The liver is the largest gland in the body. It performs about 5000 functions. From a radiographic perspective, the formation of bile is one of the most significant.
Sparing the specific details about the blood supply to the liver, you only need to know it comes from two sources: the portal vein and the hepatic artery. Usually, blood full of oxygen and nutrients is carried through arteries. Why is a vein carrying blood TO the liver instead of AWAY from it? Here is a brief overview: The portal system consists of veins arising from the walls of the stomach, part of the intestinal tract, gallbladder, pancreas and spleen. The blood in this portal system is rich in nutrients and goes TO the liver before returning to the heart. You don’t really need to know about the portal system in this class, but just remember the portal vein and hepatic artery supply the blood to the liver.

5. The Biliary System Anatomy
Bile is a channel of elimination for the waste products of red blood cells. Bile also aids in the emulsification and assimilation of fats. The liver makes the bile and either directly pours it into the duodenum or sends it to the gallbladder for storage and release during periods of digestion. There are two important ducts and an ampulla that you should become familiar with. The common bile duct joins the pancreatic duct, and they enter together into a chamber called the hepatopancreatic ampulla otherwise known as the ampulla of Vater. This ampulla opens into the descending portion of the duodenum – the first part of the small intestine.

6. Pancreas and Spleen Anatomy
The pancreas is another large gland. It is an exocrine as well as an endocrine gland. As an exocrine gland, the pancreas produces pancreatic juice which acts on proteins, fats, and carbohydrates. The endocrine function of the pancreas lies in the islets of Langerhans where cells produce hormones of insulin and glucagon. The spleen produces lymphocytes and stores and removes dead red blood cells. Notice the spleen’s location. It is located in the left, upper quadrant, just below the diaphragm, and behind the stomach.

7. Click on the correct answer.
Anatomy
Knowledge Check
Veriform appendix
At what junction does the small intestine meet the large intestine?
Ileocecal valve
Right colic flexure
Rectum
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8. The bony thorax is comprised of the sternum, ribs, and thoracic vertebrae.
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9. Pathology of Lower GI Tract and Accessory Organs
Root Forms
Meaning
Chole-
Relationship with bile
Cysto-
Bag or sac
Choledocho-
Common bile duct
Cholangio
Bile ducts
Choleycyst
Gallbladeder
One of the primary pathologies that occurs within the lower G.I. and accessory digestive areas is inflammation. The suffix “itis” means inflammation. Therefore, colitis is inflammation of the colon. Pancreatitis is inflammation of the pancreas. Appendicitis is inflammation of the appendix. You get the idea. Cholecystitis needs to be broken down a little further. You can see the “itis”, so you know there is inflammation. The prefix “chole” refers to bile, while “cystic” means bladder or sac. What is a sac that holds bile? That’s right--the gallbladder. You will see many words starting this way, like cholecystectomy – surgical removal of the gallbladder and cholecystolithiasis (lith means stone)–gallstones in the gallbladder.
Hernias are protrusions of organs (or parts of organs) through walls that normally contain them. While hernias can happen in many locations, approximately 80% of them take place in this area of the body. An inguinal hernia is where the sac containing the intestine protrudes through the abdominal wall, and often descends into the scrotum.
A few other pathologies in this area are:
Biliary stenosis - the narrowing of the bile ducts.
Hirshspung disease - absence of parasympathetic ganglia, usually in the distal colon, resulting in the absence of peristalsis.
Polyp – growth or mass protruding from a mucous membrane

10. Click on the correct answer.
Pathology
Knowledge Check
Bile Ducts
What does the prefix choleycyst mean?
Bag or Sac
Gallbladder
Common Bile Duct
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11. Increased density of a typically soft bone is called osteopetrosis.
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12. General Exposure and Technical Considerations
Radiography
General Exposure and Technical Considerations
Projection
Position
PT Lies
Side Elevated
Degrees
Colic Flexure
Aspect of Colon
PA Oblique
RAO
Prone
Left
35-45
Right
Ascending
LAO
Descending
AP Oblique
LPO
Supine
RPO
There are 13 essential projections of the large intestine. Breathing should be suspended for all of them. Images taken with a perpendicular central ray will be centered to the midline of the body at the level of the iliac crest.
In the PA oblique projection (RAO), the patient will be prone with the left side elevated degrees. This shows the right colic flexure and ascending colon.
In the PA oblique projection (LAO), the patient will be prone with the right side elevated degrees. This shows the left colic flexure and descending colon.
In the AP oblique projection (LPO), the patient will be supine with the right side elevated degrees. This shows the right colic flexure and ascending colon.
In the AP oblique projection (RPO), the patient will be supine with the left side elevated degrees. This shows the left colic flexure and descending colon.

13. Endoscopic Retrograde Cholangio-Pancreatography (ERCP)
Radiography
Endoscopic Retrograde Cholangio-Pancreatography (ERCP)
The ERCP is a procedure used to diagnose biliary and pancreatic pathologies. This study is performed by feeding a fiber optic endoscope through the mouth and into the duodenum. Fluoroscopy guides the way.

14. Click on the correct answer.
Pathology
Knowledge Check
Level of ASIS
Where should the CR be aimed for images of the colon?
Level of Iliac Crests
2-3” Above Level of
Iliac Crest
Public Symphysis
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15. When imaging the posterior ribs below the diaphragm, tell the patient to exhale and hold.
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16. Presented by