2.) Examine the duodenum from its proximal source, the pylorus of the stomach, to its terminus at the duodenojejunal flexure. Take note of the attachment of the hepatoduodenal ligament to the 1st part of the duodenum.

Note: The duodenum is loosely shaped like the letter ‘C.’ Each part of the duodenum is named for its relative position or orientation.  

Note: The 1st part of the duodenum is intraperitoneal and is anteriorly associated with the hepatoduodenal ligament. The 2nd and 3rd parts of the duodenum (and the pancreas) are secondarily retroperitoneal. The 4th part is secondarily retroperitoneal for the majority of its length, but the left lateral extent is anchored to the posterior abdominal wall by the suspensory muscle of the duodenum, just posterosuperior to the duodenojejunal flexure. Many resources you will read will categorize the 4th part as intraperitoneal.

Note: The 3rd part of the duodenum is typically found between the superior mesenteric a. and the abdominal aorta, making it vulnerable in some individuals to compression (superior mesenteric artery syndrome).

Photo 2. Duodenum

Examine the interior of the duodenum

Find these structures:

• Major duodenal papilla

• Minor duodenal papilla

3.) Find the midpoint of the 1st part of the duodenum, and incise along the anterior wall of the 1st and 2nd parts. If necessary, clean the lumen of the incised regions with paper towels. Note the differences in the appearances of the mucosa between the 1st and 2nd parts. Find the duodenal papillae in the 2nd part of the duodenum.

Note: The duodenal papillae are eruptions of the mucosa that surround drainage from the gallbladder and pancreas into the 2nd part of the duodenum. The papillae surround dilations (ampullae) of the ducts that pass through them.

Note: The major duodenal papilla surrounds the hepatopancreatic ampulla, a dilation of the joining of the (common) bile duct and main pancreatic duct. The pancreatic and (common) bile ducts may open into the duodenum separately.

Note: The minor duodenal papilla receives the accessory pancreatic duct, if present. Typically, the minor duodenal papilla is found 1.5-2 cm proximal to the major duodenal papilla.  

Photo 3. Major and minor duodenal papillae

Expose the pancreas, and identify its parts

Find these structures:

• Pancreas

  • Pancreatic duct

  • Accessory pancreatic duct

4.) Clear the peritoneum and connective tissues on anterior surfaces of the 2nd and 3rd parts of the duodenum and the pancreas, but be very careful not to interrupt any of the blood vessels.

5.) Identify the pancreas, and note the relationships of these parts to other viscera.

Photo 4. Pancreas

Note: All of the pancreas is secondarily retroperitoneal with the exception of the tail, which is intraperitoneal.

6.) Using blunt dissection with sharp-sharp scissors of the anterior pancreas, locate the pancreatic duct. Start at the midpoint of the body of the pancreas, and work bilaterally to expose the length of the pancreatic duct. Take note of where the pancreatic duct meets the (common) bile duct, and their common course to the major duodenal papilla.

7.) If an obvious connection between the pancreatic duct and accessory pancreatic duct is seen, follow the connection to uncover the entirety of the accessory pancreatic duct. If no obvious connection is present, attempt to locate an accessory duct with blunt separation of the anterosuperior pancreas with sharp-sharp scissors, starting adjacent to the minor duodenal papilla.

Note: Typically, the accessory pancreatic duct is found in the head of pancreas, superior to the pancreatic duct. Also, it is common for the pancreatic and accessory pancreatic ducts to anastomose.

Photo 5. Pancreatic duct and accessory pancreatic duct

Examine the vasculature of the duodenum and pancreas

Note: The duodenum spans the distal foregut and proximal midgut. As such, the duodenum (and by association the pancreas) is supplied by branches from both the celiac trunk and the superior mesenteric a. While vasculature is inconstant, it may be helpful to conceptualize the vasculature of the duodenum and head of pancreas separately from the vasculature of the neck, body, and tail of pancreas.

Find these structures:

• Gastroduodenal a. (from the common hepatic a.)

  • Anterior superior pancreaticoduodenal a. 

  • Posterior superior pancreaticoduodenal a.

• Inferior pancreaticoduodenal a. (from the superior mesenteric a.)

  • Anterior br.

  • Posterior br.

8.) Locate the gastroduodenal a. from its divergence from the common hepatic a. Trace the gastroduodenal a. inferiorly, to locate the anterior superior pancreaticoduodenal a. Carefully trace the anterior superior pancreaticoduodenal a. over the head of pancreas to find an anastomosis with the anterior br. of the inferior pancreaticoduodenal a. If no anastomosis is apparent, turn your attention to the superior mesenteric a.

Photo 6. Superior pancreaticoduodenal a.

Note: The superior mesenteric a. can be found in the vicinity of the neck of pancreas, which overlays the origin of the SMA and the junction of the SMV with the splenic v.

9.) Trace the inferior pancreaticoduodenal a. from the SMA, and locate the anterior br. of the inferior pancreaticoduodenal a.

Photo 7. Inferior pancreaticoduodenal a.

Photo 8. Anastomosis of anterior superior pancreaticoduodenal a. & anterior br. of inferior pancreaticoduodenal a.

10.) Incise the peritoneum at the right border of the 2nd part of the duodenum to allow posterior access.

11.) Reflect the 2nd part of the duodenum and head of pancreas toward the midline. From this view, locate the posterior br. of the inferior pancreaticoduodenal a. (from the SMA) and the posterior superior pancreaticoduodenal a. (from the gastroduodenal a.).

Photo 9. Anastomosis of posterior superior pancreaticoduodenal a. & posterior br. of inferior pancreaticoduodenal a.

Find these structures:

• Celiac trunk

  • Splenic a.

    • Dorsal pancreatic a.

      • Inferior pancreatic a.

    • Greater pancreatic a.

12.) Starting from the splenic a., use blunt dissection to find the dorsal pancreatic a. and greater pancreatic a. Follow the dorsal pancreatic a. through the pancreas to uncover its transition into the inferior pancreatic a. Anastomoses among the arteries serving the pancreas are quite common and should be examined as they are found.

Photo 10. Pancreatic aa.

Examine the kidneys, suprarenal glands, and retroperitoneal space.

Find these structures:

• Suprarenal glands

• Kidney

  • Pararenal (paranephric) fat 

  • Renal fascia

  • Perirenal (perinephric) fat 

  • Fibrous capsule

• Ureter

13.) Remove the jejunum and ileum.

       a. Tie off and cut the jejunum four finger-breadths distal to the duodunojejunal flexure.

Photo 11. Procedural: cutting the jejunum

        b. Cut the intestinal aa. two finger-breadths from SMA.

Photo 12. Procedural: cutting intestinal aa.

c. Tie off and cut the distal ileum taking care not to disrupt any ileocecal a. brs. to the ileum. This is best done after removing the mesentery and locating the ileal branches of the ileocecal a.

Photo 13. Procedural: cutting the distal ileum

14. ) Carefully remove the pararenal fat surrounding the renal fascia.

15.) Remove the renal fascia and perirenal fat to reveal the kidneys and suprarenal glands.

Photo 14. Procedural: renal fascia removal

Photo 15. Kidney, suprarenal gland, & ureter

Find these structures:

• Abdominal aorta

  • Middle suprarenal aa.

  • Renal aa.

    • Inferior suprarenal aa.

  • Gonadal aa.

• Inferior vena cava 

  • Right suprarenal v.

  • Right renal v.

  • Right gonadal v.

  • Left renal v.

    • Left gonadal v.

    • Left suprarenal v.

16.) Trace the vasculature from the hila of the kidneys medially and inferiorly to uncover the renal vasculature and ureters.

Note: The abdominal aorta is left lateral to the inferior vena cava. This relationship creates an asymmetry in length between left and right renal vessels. Thus, the left renal v. is longer than the right, and the right renal a. is longer than the left.

Note: When examining the renal vasculature, one typically encounters renal vv. anterior to renal aa. Often, segmental arteries can be found anteriorly encircling segmental veins

Note: The pattern of drainage of the renal veins is asymmetrical. The short right renal v. typically drains only the right kidney, whereas the longer left renal v. typically drains the left kidney, and receives the left suprarenal v. and the left gonadal v.

Photo 16. Renal vasculature and ureter

17.) Examine the relationship between the superior mesenteric a. and both the inferior (3rd) part of the duodenum and the left renal vein.

Note: An acute angle between the SMA and the abdominal aorta may lead to compression of either (or both) the 3rd part of the duodenum (superior mesenteric artery syndrome), or the left renal v. (renal vein entrapment - aka nutcracker - syndrome).

Note: Three arteries typically supply each of the suprarenal glands: superior suprarenal a. (from the inferior phrenic a.), the middle suprarenal a. (from the abdominal aorta), and the inferior suprarenal a. (from the renal a.).

Photo 17. Suprarenal gland vasculature

Note: Only one vein, the suprarenal v., typically drains each of the suprarenal glands. The left suprarenal v. typically drains into the left renal v., whereas the right suprarenal v. typically drains directly into the inferior vena cava.

18.) Carefully remove the parietal peritoneum from the abdominal aorta and inferior vena cava to locate visceral branches and tributaries.

Photo 18. Vasculature of the IVC

Note: It is not uncommon to find accessory renal aa., as they have a frequency of about 30% (Gray’s Anatomy, 41st ed.). Accessory renal aa. run from the abdominal aorta through the hilum of the kidney. Polar aa, which may run from the abdominal aorta to the poles of the kidneys, are also considered to be accessory renal aa.

Photo 19. Vasculature of the abdominal aorta

19.) Carefully remove the right kidney by cutting the right renal vasculature and ureter medial to the hilum.

Photo 20. Procedural: removing the right kidney

Find these structures:

• Kidney

  • Medial border

    • Renal sinus

  • Renal cortex

    • Renal columns

  • Renal medulla

    • Renal pyramids

    • Renal papillae

  • Renal pelvis

    • Minor calices

    • Major calices

• Ureter

20.) From the posterolateral surface of the kidney, use sharp dissection to hemisect the kidney.

Note: The parenchyma of the kidney is divided into the cortex, an outer layer of tissue which covers and surrounds inner masses of medulla, called the pyramids. Nephrons, individual functional units of kidneys, span both the cortex and medulla. Collecting ducts, which receive filtrate from the nephrons, terminate at the renal papillae. Each papilla empties urine into a minor calyx. Minor calices coalesce into major calices. Major calices drain into the renal pelvis, which is contiguous with the ureter. Ureters conduct urine to the urinary bladder.

Note: The medial border of the kidney is concave, and hosts the hilum of the kidney. The hilum conducts nearly all of the neurovasculature of the kidney (excluding capsular aa. and polar aa.). Nestled within the concavity of the medial border is the renal sinus, which is largely occupied by perirenal fat.

Photo 21. Hemisected kidney

Note: Regions of cortex situated between renal pyramids are called renal columns. These columns both host nephrons and conduct arteries and veins that service nephrons.

Photo 22. Hemisected kidney

Note: Typically, there are 2-3 major calices per kidney, and 3-4 minor calices per major calyx.

Photo 23. Hemisected kidney