Supra and Infracolic Organs; Retroperitoneum Flashcards
(123 cards)
1
Q
What are supracolic organs?
A
• the organs superior to the level of the transverse colon
2
Q
Examples of supracolic organs
A
• Includes the liver, biliary system, stomach, spleen, pancreas and duodenum
3
Q
Venous Drainage of the supracolic organs
A
• All Supracolic organs (except the liver), are drained by tributaries of the hepatic portal vein
4
Q
Location of the Liver in the abdomen
A
- Right Hypochondriac Region (right lobe)
- Epigastric Region (right and left lobe)
- Left Hypochondriac Region (left lobe)
5
Q
Anterior/Diaphragmatic Surface of the Liver
A
• Right and Left lobes are separated by the falciform ligament
??
6
Q
What is the falciform ligament?
A
• Falciform ligament attaches the liver to the thoracic diaphragm and the anterior wall of the peritoneal cavity
7
Q
What is the ligamentum teres?
A
adult remnant of the foetal umbilical vein and attaches between the umbilicus and the porta hepatis
8
Q
What subdivisions are found in the Posterior/Visceral Surface of the Liver
A
• Left lobe has two smaller subdivisions (caudate lobe, quadrate lobe)
9
Q
Caudate Lobe
A
More superior and lies immediately to the left of the inferior vena cava
10
Q
Quadrate Lobe
A
More inferior and lies immediately to the left of the gallbladder
11
Q
What is the Porta Hepatis
A
o Continuous with the hepatic pedicle which carries the vessels and ducts to and from the liver
o Is the hilum and is the point where major vessels and ducts enter and exit the liver
o Surrounded by fibrous tissue
12
Q
What vessels enter and exit the liver?
A
Includes the hepatic artery proper, the hepatic portal vein and the common hepatic duct
13
Q
Function of the common hepatic duct
A
carrying bile to the gallbladder
14
Q
Function of the hepatic artery proper
A
to carry oxygenated blood to the liver
15
Q
Function of the hepatic portal vein
A
to carry the molecules absorbed within the digestive system for the liver to metabolise and detoxify these molecules
16
Q
Branches of the structures within the liver
A
Define the functional compartments or lobules of the liver
17
Q
Left Branches of the structures entering the porta hepatis
A
Enter the quadrate and caudate lobes – therefore are considered part of the functional left lobe of the liver
18
Q
What separates the lobes of the liver?
A
an imaginary plane through the IVC and gallbladder separates the two functional lobes of the liver
19
Q
Bare Area of the Liver
A
Refers to the area where the peritoneum reflects from the thoracic diaphragm to the surface of the liver
o No peritoneum in contact with the liver in this area
o The liver is in contact with the thoracic diaphragm
The coronary ligaments on the surface of the liver are folds of peritoneum
20
Q
What is the Liver Related to?
A
- Inferior Vena Cava
- Gallbladder
- Stomach (gastric impression)
- Duodenum
- Right colic/hepatic flexure (colic impression)
- Right kidney (renal impression)
21
Q
Segments of the Liver
A
- Eight hepatic segments
- Each segment is supplied blood by a branch of the left or right hepatic artery, a branch of the hepatic portal vein and is drained by a branch of the right or left hepatic duct
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Q
Segments of Gallbladder
A
• Consists of fundus, body and neck
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Q
Segments of the cystic duct
A
• Spiral Valve (mucosal folds)
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Q
Location of the Stomach
A
• Variable organ
o Epigastric region, umbilical region, left hypochondriac region
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Types of Variability in Stomach Shape
* Hypersthenic - massive build
* Sthenic - average build
* Hyposthenic - slender build
* Asthenic - very slender build
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Hypersthenic Stomach Shape (5%)
o Massive build, broad and deep thorax, high diaphragm and high gallbladder and stomach
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Sthenic Stomach Shape (48%)
o Athletic type, relatively heavy with large bones, high gallbladder and stomach
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Hyposthenic Stomach Shape (35%)
o Slender and light weight, stomach and gallbladder high in abdomen
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Asthenic Stomach Shape (12%)
o Extremely slender with light build, shallow thorax and low gallbladder and stomach position in abdomen
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Duodenum
* Approximately 25cm in length
* Most of the duodenum is retroperitoneal
* duodenojejunal flexure
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Parts of the Duodenum
o Superior Part (L1)
o Descending Part (L1-L3)
o Horizontal Part (L3)
o Ascending Part (L2)
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Duodenal Cap/Bulb/Ampulla
* Proximal 2cm of first part of duodenum
* Cone-Shaped and contains no plicae circulares
* Contains rugae
* Intraperitoneal organ (i.e., has mesentery)
• Note the gastroduodenal junction located between the stomach and duodenum
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Pancreas
Vertebral Levels
o L1-L3
* Retroperitoneal abdominal organ
* Extends between the duodenum and spleen
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Location of the differing segments of the pancreas
* Head of the pancreas sits within the C-shaped duodenum
* Neck is anterior to the superior mesenteric artery and the superior mesenteric vein
* Tail is located within the hilum of the spleen
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Uncinate Process of the Pancreas
o Hook process which extends from the head
o Major mesenteric vessels sit superior to the uncinate process
o Vessels pass posterior within the neck region
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Celiac Trunk
located superiorly (lies at level T12)
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Splenic artery
travels along the superior border of the pancreas
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Superior Mesenteric Artery
o Extends off the anterior abdominal aorta at L1
o Branching off the abdominal aorta posterior to the pancreas
o Enters the mesentery of the small intestines
o supplies the small intestine, jejunum and ileum
• J-Shaped
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Left Side Branches of the Superior Mesenteric Artery
Supply jejunum and ileum – jejunal and ileal arteries
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Right Side Branches of the Superior Mesenteric Artery
Supply caecum, ascending colon and 2/3 of transverse colon
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Splenic Vein
o Extends from spleen and joins the superior mesenteric vein to form a confluence
o Confluence forms the hepatic portal vein – extends to the liver (carries molecules and nutrients from the digestive tract to the liver)
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Inferior Mesenteric Vein
o Tributary into the Splenic Vein as it passes posterior to the pancreas
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Anterior Relations of the Pancreas
Transverse Mesocolon
| Stomach
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Posterior Relations of the Pancreas
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Hepatic Pedicle
Superior mesenteric artery and vein
Splenic vein
Inferior mesenteric vein
IVC and aorta
Left psoas major
Left suprarenal gland and left kidney
```
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Features of the Spleen
o Diaphragmatic Surface – in contact with the thoracic diaphragm
o Visceral surface – several organs form impressions
Gastric impression (stomach), colic impression (splenic flexure of the colon), renal impression
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Spleen Relations
* Tail of pancreas medial relation at hilum
| * Related to left ribs 9-11
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Blood Supply of the Liver
• Common hepatic artery -> Hepatic artery proper -> Right hepatic artery and Left Hepatic Artery
- Cystic Artery - Branch of the Right Hepatic Artery
- Middle hepatic artery - Branch of the Left Hepatic Artery
• Hepatic portal vein
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Blood Supply of the Stomach
Right Gastric Artery - Branch of the Hepatic Artery Proper
Left Gastric Artery - Branch of the coeliac trunk
- Right and left gastric arteries (supplies lesser curvature of stomach)
Left gastroepiploic/gastro-omental Artery - Collateral Branch of the Splenic Artery
Right gastroepiploic/gastro-omental Artery - Branch of the Gastroduodenal Artery
- Right and left gastroepiploic/gastro-omental arteries (supplies greater curvature of stomach)
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Blood Supply of the Pancreas
* Gastroduodenal artery - Branch of the Common Hepatic Artery
* Superior mesenteric artery
* Splenic artery
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Blood Supply to the Spleen
• Splenic Artery
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Coeliac Trunk
* Origin typically at T12
| * Visceral branch of the abdominal aorta
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Coeliac Trunk Divisions
• Terminally divides into left gastric (courses to the lesser curvatures of stomach), splenic, and common hepatic (travels to right side of body and branches to the liver, small instestine and stomach) arteries
o Trifurcates – divides simultaneously into the three branches
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Coeliac Trunk Variations: 3 Branches
o (70%)
o Common trunk with trifurcation (10-19%)
o Common trunk with bifurcation into hepatosplenic and left gastric (50-75%)
o May also include 4th branch (e.g., gastroduodenal) (10%)
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Coeliac Arteriogram
* Plain radiography is typically only used within emergencies
* Contrast within the urinary system is common
* Computed Tomography Angiography is most used to examine the coeliac trunk
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Right Gastroepiploic Artery
o Branches of the gastroduodenal artery
o Anastomoses with the left gastroepiploic artery (branch of the splenic artery)
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Hepatic Artery proper
o Branches include the right, middle (branch of the left hepatic artery) and left hepatic arteries and the cystic branch (arises as a collateral branch of the right hepatic artery)
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Variations with the absence of the coeliac trunk
Type III
o Independent branches of the left gastric, common hepatic, and superior mesenteric arteries are found coming off the abdominal aorta
Gastrosplenic Trunk and Hepatomesenteric Trunk
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Location of the Infracolic Organs
• Located inferior to the transverse colon and include the small and large intestines
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Superior Mesenteric Artery relation to the infracolic organs
• Superior mesenteric artery is responsible for the entire blood supply to the jejunum, ileum, and proximal 2/3 of the large intestine
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Inferior Mesenteric Artery relation to the infracolic organs
• Inferior mesenteric artery is responsible for the blood supply for the distal 1/3 of the large intestine
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Where does the blood of the intestine and the stomach drain into?
• All of the blood from the intestine and stomach drains into the liver via the hepatic portal vein before it enters the venous flow
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What forms the hepatic portal veins?
• The hepatic portal veins is typically formed from the confluence of the superior mesenteric and splenic veins
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Mesenteries of the small intestine
• Mesenteries (including the mesocolons of the transverse and sigmoid colon) also contains important lymph nodes, lymphatic vessels and nerves, all supported by fat between the two layer of peritoneum
- Allows the small intestine to move around
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Location of the main trunk of the superior and inferior mesenteric blood vessels
• The main trunk of the superior and inferior mesenteric blood vessels is retroperitoneal and it is only the branches and tributaries that course through the mesenteries
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What does the small intestine consist of?
Consists of the retroperitoneal and most proximal part of the duodenum, followed by the jejunum and ileum
o These are intraperitoneal structures having the mesentery of the small intestine attaching them to the posterior abdominal wall
o The branches and tributaries of the superior mesenteric artery and vein run through
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Location of the parts of the small intestine
* Duodenum – Umbilical
* Jejunum – Umbilical (left half), left lumbar, left iliac
* Ileum – umbilical (right half), right lumbar, hypogastric and right iliac
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Plicae Circulares of the Small Intestine
• Unique to the small intestine and are permanent folds of the mucosa that help to slow down the passage of food and increase surface area to increase efficiency of nutrient absorption
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Folds of the Small Intestine
* These folds are more numerous in the more proximal parts of the small intestine (duodenum and jejunum) where nutrient absorption is mainly occurring
* The folds decrease in density and size in the distal parts of the small intestine (ileum) since most of the nutrients have already been absorbed by the time food reaches the ileum
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Large Intestine from proximal to distal
```
o Caecum and Vermiform Appendix
o Ascending Colon
o Transverse Colon
o Descending Colon
o Sigmoid Colon
o Rectum
```
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Large Intestine: Caecum and Vermiform Appendix
Intraperitoneal organ in the right iliac region
Ileum of the small appendix terminates here
Vermiform appendix extends from the caecum
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Large Intestine: Ascending Colon
Retroperitoneal organ in the right lumbar region (25% have mesocolon)
Approx. 15cm in length
- Continuation of the Caecum
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Large Intestine: Transverse Colon
Intraperitoneal organ in umbilical region with a transverse mesocolon attaching it to posterior abdominal wall (anterior surface of retroperitoneum along the inferior border of pancreas)
- Continuation of the ascending colon
Length and location highly variable due to its mobility (approx. 50cm in length)
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Large Intestine: Descending Colon
Retroperitoneal with smaller diameter than ascending colon
Left lumbar region (33% have mesocolon)
Almost twice as long as ascending colon, approx. 25cm in length
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Large Intestine: Sigmoid Colon
S-shaped intraperitoneal organ in left iliac and hypogastric regions of abdomen and pelvic cavity with a sigmoid mesocolon attaching it to posterior abdominal wall
Length and location highly variable due to its mobility
Terminated at S3
Approximately 40 cm in length
o Rectum
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Large Intestine: Rectum
Largely in the pelvic cavity
| Proximal part may lie in the hypogastric region
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Large Intestine: Parts and Features
```
o Hepatic/Right colic flexure
o Splenic/Left colic flexure
o Haustra
o Plicae Semicirculares
o Epiploic appendages
```
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Large Intestine: Hepatic/Right colic flexure
Between the ascending and transverse colons
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Large Intestine: Splenic/Left colic flexure
Between the transverse and descending colon
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Large Intestine: Haustra
Mark wall of the large intestine
| Three longitudinal bands of smooth muscle tissue called teniae coli
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Large Intestine: Plicae Semicirculares
Matching the location of each haustra internally
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Large Intestine: Epiploic appendages
Fat tags
| Extend off the teniae coli
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Location of the Vermiform Appendix
• Located in the right iliac region of abdomen
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Variable Length of the Vermiform Appendix
Variable length: (2-20cm) and diameter (0.3-1cm)
| o Typically about 10cm
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Variable Position of the Vermiform Appendix
o Retrocaecal (65-70%)
o Pelvic (25-30%)
o Pre or Post Ileal (5%)
o Duplex appendix is very rare
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Retrocaecal (65-70%): Vermiform Appendix
Located posterior to the caecum
Ileum arrives at a perpendicular angle to attach to the caecum -> base of vermiform appendix is attached to the most inferior (proximal) part -> ascends posterior to caecum
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Pelvic (25-30%): Vermiform Appendix
Directed inferiorly and is descending towards the pelvic cavity
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Duplex Appendix Variation: Vermiform Appendix
o Two appendices located in the proximal part of caecum of the large intestine in the right iliac region
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McBurney's Point
o Base of vermiform appendix
o Line drawn between right ASIS and umbilicus
Point located 1/3 distance medial to ASIS – indicated the base of the vermiform appendix
o Used when removing an inflamed appendix
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Blood Supply of the Small Intestine
• Superior Mesenteric Arte ry
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Blood Supply to the Large Intestine
• Superior Mesenteric Artery and Inferior Mesenteric Artery
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Inferior Mesenteric Artery
* Origin – L3
| * Supplies transverse colon (distal 1/3), descending and sigmoid colon and rectum
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Hepatic Portal Vein
* Typically forms as a confluences of the splenic and superior mesenteric veins
* Diverts the blood from the intestine to the liver -> in the liver molecules which are absorbed can be metabolised and detoxification of harmful chemicals can also occur
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Superior Mesenteric Vein
o Carries blood from the small intestine and the proximal two thirds of the large intestine
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Splenic Vein
o Carries blood after the blood is filtered through the spleen
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Inferior Mesenteric Vein
o Typically, a tributary of the splenic vein and is carrying blood from the distal 1/3 of the large intestine
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Variations of the Hepatic Portal Vein
o Confluence between the inferior and superior mesenteric veins and the splenic vein
o Inferior mesenteric may be tributary of the superior mesenteric vein
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What does CTA stand for?
o Computed Tomography Angiography
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Course of the Hepatic Portal Vein
* Course through the hepatic pedicle (bundle of structures passing out of the liver)
* Divides into several branches upon reaching the liver
* Related to the abdominal aorta (posterior to the portal vein)
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Most common phenotype of the hepatic portal vein
SMV and splenic vein are forming a confluence to form the portal vein
• Occurs posterior to the pancreas
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CT of the Abdomen Approach
Three-Phase Approach
- Perform CT without contrast
- Perform CT with contrast in an arterial phase
• Contrast is mainly in the arteries only
- Perform CT with contrast in a portal venous phase
• Contrast has passed through the major organs and is draining into the veins
• Portal vein will be more prominent
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Retroperitoneum
* a sub-region of abdomen that lies posterior to peritoneal cavity
* contains retroperitoneal structures and extraperitoneal fat.
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Retroperitoneum Structures
* Sympathetic ganglia and associated nerves travel through the epigastric, umbilical and hypogastric regions
* The ascending and descending colons are also typically retroperitoneal.
* the prominent kidneys and suprarenal glands in the right and left lumbar regions
* the right and left ureters travelling from the lumbar regions to the hypogastric region
* the left-sided abdominal aorta and right-sided inferior vena cava passing through the epigastric and umbilical regions.
* Others organs include duodenum of small intestine, pancreas, peripheral nerves of lumbar plexus, lymphatics, extraperitoneal fat
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Location of the Kidneys
* located in the paravertebral gutters lateral to the vertebral column at the level of T12 to L3 vertebrae and are retroperitoneal organs.
* right kidney is more inferior than the left kidney due to the size and position of the liver being moreso on the right side of the abdomen.
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Capsule of Each Kidney
• capsule of each kidney is surrounded by perinephric/perirenal fat for cushioning.
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Longitudinal Axes of the Kidneys
o Each is obliquely inclined
Medial aspect of kidney lying across the psoas major
o Parallel to longitudinal axis of psoas major
o Superior pole more medial
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Renal Pedicle
o All structures which enter and exit the renal hilum
```
Consists of:
Ureter
Renal artery
Renal vein – anterior to renal artery before flowing to the IVC
Nerves
Lymphatics
```
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Posterior Relations of Kidneys
o Thoracic Diaphragm
o Transversus abdominis
o Quadratus lumborum
o Psoas Major
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Anterior Relations of Kidney
```
o Right Suprarenal gland
o Area for liver
o Duodenum
o Area for colon
o Area for small intestine
o Left suprarenal gland
o Area for stomach
o Area for spleen
o Area for descending colon
```
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Abdominal Ureters
o Retroperitoneal
o 3 to 5 mm in diameter
o 12 cm in length
Constrictions can occur:
ureteropelvic junction
common iliac vessels
pelvic brim
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Abdominal Ureters Location
o Descends anterior to psoas major, across common iliac vessels and pelvic brim where it becomes pelvic ureter before entering the urinary bladder.
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Ureter Variations
* Duplex Collecting System
| * Bifid Ureter
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Ureter: Duplex Collecting System
o A double pelvis may occur with fusion at the uretopelvic junction to become a single ureter
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Ureter: Bifid Ureter
o Can occur where the ureters fuse before entering the urinary bladder
o May also result in a complete duplication of ureters
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Lumbar Plexuses
* Formed by the anterior rami of spinal nerves L1 to L4
* Located within belly of psoas major
* Major nerves arising from this plexus include the femoral nerve (which supplies the anterior thigh) and the obturator nerve (which supplies the medial thigh).
115
Plicae Circulares within the Duodenum
- Do not allow the duodenum to stretch as they are permanent folds in the lining
- Slow the movement of chyme and increase the surface area to increase absorption
- Found in all of the duodenum expect the duodenal cap
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Mesentery attached to the Large Intestine
- Attached to the transverse colon is known as the transverse mesocolon
- Attached to the sigmoid colon is known as the sigmoid mesocolon (contains blood vessels and lymph nodes)
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Greater Omentum
- Contains fatty tissue, lymph nodes, blood supply
- Layer of the peritoneum forming a sheet anterior to the intestines
- Can move and increase blood supply in an area with reduced blood supply
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Abdominal Region of the Caecum and Vermiform Appendix
- Right Iliac/Inguinal Region
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Abdominal Region of the Ascending Colon
- Right lumbar region
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Abdominal Region of the Transverse Colon
Umbilical Region
121
Abdominal Region of the Descending Colon
Left Lumbar Region
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Abdominal region of the Sigmoid Colon
Left Inguinal Region and Hypogastric Region
- Also enters the pelvic cavity
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Variations of the Kidney
Pelvic Kidney - Sitting in the pelvis not the abdomen
Horeshoe Kidney - Two kidneys are medially connected anterior to the aorta
