The retroperitoneum Flashcards
List the primary retro-peritoneal structures
Abdominal aorta and its branches Inferior vena cava and its tributaries Kidneys & ureters Adrenal glands Nerves (lumbar plexus & sympathetic trunk
What is meant by primary retroperitoneal structures
These structures developed outside the parietal peritoneum. They never had a mesentery.
List the secondary retroperitoneal structures and explain why they are secondary
Duodenum (except the first part) *
Pancreas (tail is INTRAperitoneal) *
Colon (ascending and descending only)*
- These organs originally had a mesentery, then became secondarily retroperitoneal when the mesentery fused with the body wall
Are any retroperitoneal structures found on the anterior abdominal wall
No- they are found on the posterior abdominal wall
Therefore we access the body posteriorly to perform biopsies of these organs
What is the first superimposed structure
the duodenum
Describe the first part of the duodenum
Superior
Extends from pyloric orifice to neck of gallbladder
Just to the right of L1
Passes anteriorly to bile duct, gastroduodenal artery, portal vein and IVC
5cm long
Why is the first part of the duodenum important clinically
Referred to as the ampulla or duodenal cap
Most duodenal ulcers occur in this part of the duodenum
Describe the second part of the duodenum
Right of midline extends from neck of gall bladder to the lower border of L3
Anterior surface is crossed by the transverse colon
Posterior to it is the right kidney
Medially is the head of the pancreas
This part contains the major duodenal papilla- entrance for bile and pancreatic ducts
Also contains minor duodenal papilla- entrance for accessory pancreatic duct
7-10cm
Where is the junction between the foregut and midgut found
Just below the major duodenal papilla
Describe the 3rd part of the duodenum
The inferior part- crosses the IVC, the aorta and vertebral column
It is crossed anteriorly by the superior mesenteric artery and vein
6-8cm
Describe the 4th part of the duodenum
Ascending
Passes upward on or to the left of the aorta to approximately the upper border of L2 and terminates at the duodenojejunal flexure
5cm
Describe the superimposed structures
Duodenum, pancreas and spleen are superimposed on the ‘background’ structures. All are retroperitoneal except the spleen and the tail of the pancreas.
What type of organ is the pancreas
Exocrine and endocrine gland
It is therefore a secretory organ
Describe the relations of the pancreas
It extends across from the posterior abdominal wall from the duodenum, on the right, to the spleen on the left
Lies mostly posterior to the stomach
Describe the head of the pancreas
Lies within C-shaped concavity of the duodenum
anterior to IVC
Describe the uncinate process
Projects from the lower part of the head
Passes posterior to the superior mesenteric vessels
But passes anterior to the IVC
Describe the neck of the pancreas
Anterior to the superior mesenteric vessels and IVC
Posterior to the neck is where the superior mesenteric vein and splenic vein join to form the portal vein
Describe the body of the pancreas
Elongate and extends from neck to tail
extends to the left side across the aorta to left kidney
Describe the tail of the pancreas
Passes between layers of the splenorenal ligament
kidney to spleen in dorsal foregut mesentery (lieno-renal or spleno-renal ligament)
Describe the pancreatic duct
Begins at tail
After entering the head it moves inferiorly and in the lower part of the head it joins the bile duct
This joining forms the hepatopancreatic ampulla (Ampulla of Vater), which enters the descending part of the duodenum at the major duodenal papilla
Surrounding the ampulla of vater is the sphincter of oddi- a collection of smooth muscle
Describe the accessory pancreatic duct
Empties into the duodenum just above the major duodenal papilla in the minor duodenal papilla
Presence of two ducts reflects the embryological origin of the pancreas
Describe the embryogenesis of the pancreas
Derived from buds growing into dorsal and ventral foregut mesenteries
At the foregut/midgut junction the septum transversum generates 2 pancreatic buds (dorsal and ventral endoderm) which will fuse to form the pancreas. The dorsal bud arises first and generates most of the pancreas. The ventral bud arises beside the bile duct and forms only part of the head and uncinate process of the pancreas.
Dorsal swings to the ventral
Describe the arterial supply to the pancreas
Branches from common hepatic artery
Branches from splenic artery
Branches from superior mesenteric artery
Discuss the significance of these relations to pancreatitis and pancreatic cancer
Pancreas is in close proximity to many important epigastric structures: duodenum, stomach, spleen, left kidney, adrenal gland
Cancer or trauma to the pancreas can damage these structures
Cancers can spread locally, invading the portal vein and superior mesenteric vessels and may extend into the porta hepatis
Lymph node spread is common
Can cause obstructive jaundice
Describe the duct system for bile
Connects gallbladder to the descending part of the duodenum
Coalescence of ducts begins in the liver parenchyma and continues until the right and left hepatic ducts are formed
These combine to form the common hepatic duct
Descends until it is joined by cystic duct from gallbladder- completing the formation of the bile duct
Descends posteriorly to the superior part of duodenum before joining the pancreatic duct.
Describe the relations of the duct system
Common hepatic duct runs near the liver, with the hepatic artery proper and portal vein in the free margin of the lesser omentum
Bile duct is to the right of the hepatic artery proper and usually to the right of and anterior to the portal vein
omental foramen is posterior
Describe the clinical significance of gall stones
Gallstones occur in 10-20% of adults
Risk factors include age, obesity and being female
80% are cholesterol stones and 20% are pigment (bilirubin calcium salts) stones.
Gallstones can block the flow of bile from the gallbladder to the duodenum and cause inflammation (cholecystitis) or block the hepatopancreatic ampulla and impede pancreatic excretion from the pancreas
The pain of acute cholecystitis may be felt in the right upper abdominal quadrant, radiating laterally just beneath the right breast to the back just below the inferior angle of the right scapula
Describe the histology of the endocrine pancreas
The islets of Langerhans are clumps of secretory cells (up to around 3000) supported by reticulin fibres, and containing numerous fenestrated capillaries. There is a delicate capsule around each islet. They are paler than the surrounding exocrine cells, as they have less rER. These islets do not have an acinar organisation.
Highly vascularised
Describe the histology of the acinus of the pancreas
Intensely eosinophilic
Have basal nuclei and produce digestive enzymes
Centroacinar cells- paler cytoplasm and protrude into the ducts
Describe the difference between interlobular and intralobular ducts
shorter intercalated ducts- branching- initial part of excretory system- lined by a low simple cuboidal epithelium
longer intralobular ducts- lined by simple cuboidal epithelium- consisting of more plump cells
larger interlobular ducts- lined by cuboidal epithelium- invested by deep fibrous connective tissue- drain directly to main pancreatic ducts
Which part of the kidney is palpable
the lower pole- upper pole is behind the ribs
Describe the gross structure of the kidney
At the gross level, the interior of the kidney is divided into an outer cortical layer and an inner medullary layer
At its apex each medullary pyramid has a real papilla in which the collecting ducts of the nephron deliver urine to minor and major calicies.
Several major calicies coalesce to form the real pelvis, which exits the kidney at its hilum and forms the ureter.
The ureter conveys urine to the urinary bladder
Describe the hilum of the kidney
Present in medial margin of each kidney
Deep vertical slit through which renal vessels, lymphatics and nerves enter and leave the substance of the kindey,
Internally, the hilum is continuous with the renal sinus
Perinephric fat continues into the hilum and sinus and surrounds all structures
Lies in transpyloric plane (L1)
Describe the anterior relations of the right kidney
Small part of superior pole- suprarenal gland
Large part of rest of upper part- liver (separated by layer of peritoneum)
Medially- descending part of duodenum
Inferolaterally- right colic flexure
Inferomedially- segment of intraperitoneal S.I
Describe the anterior relations of the left kidney
A small part of the superior pole and its medial side- suprarenal gland
Rest of superior pole is covered by intraperitoneal stomach and spleen
Inferiorly- retroperitoneal pancreas
Lateral lower half- left colic flexure and beginning of the descending colon
Inferomedially- intraperitoneal jejunum
Summarise the visceral relations of the kidneys
Adrenal glands on both sides Liver on the right 2nd part of duodenum on the right Ascending colon on the right Descending colon and stomach on the left Spleen on the left Tail of pancreas on the left Coils of small bowel especially on the left
Describe the differences in location of the right and left kidney
Right kidney is usually slightly lower than the left
Superior pole of the R kidney lies at the level of the 11th intercostal space and that of the L at the 11th rib
Hilum lies at about the level of L1 (R & L)
L1 is a large vertebrae- this is why they have their hilum at the same vertebral level
Left kidney is slender and longer and more medial
Describe the locations of the kidneys
Extend from T12 to L3
Hilum is 5cm from midline
Inferior pole is 3-4cm above iliac crest
Summarise the positions of the kidneys
Right often lower than left
Upper poles closer to median plane than lower poles
12th ribs run diagonally across posterior surfaces of kidneys
Ureters descend vertically, anterior to lumbar transverse processes
Ureter narrows at 3 places: 1) ureteropelvic junction, 2) at pelvic brim (common iliac vessels cross) 3) Entrance of urinary bladder
Describe the posterior relations common to both kidneys
Superiorly is the diaphragm and inferior to this moving in a medial to lateral direction are the psoas major, quadratus lumborum and transversus abdominis muscles.
Describe the posterior relations of the right kidney
The superior pole of the right kidney is anterior to rib 12.
Describe the posterior relations of the left kidney
The superior pole of the left kidney is anterior to ribs 11 and 12
Describe the relations of the pleural sacs to the kidneys
The pleural sacs and specifically, the costo-diaphragmatic recesses therefore extend posterior to the kidneys
Also passing posteriorly, are the subcostal vessels and nerves and the iliohypogastric and ilio-inguinal nerves
Summarise the posterior relations of the kidneys
Lie on the diaphragm, psoas, quadratus lumborum & transversus abdominis muscles
Between kidneys and muscles cross the T12 (subcostal) and L1 (ilio-hypogastric and ilio-inguinal) nerves
A posterior approach to the kidneys is used for open surgery and for renal biopsy
Describe the renal arteries
lateral branches of the abdominal aorta that supply each kidney; arise inferior of the SMA origin at L2/3, with the left renal artery shorter and higher
Describe the renal veins
are formed by multiple smaller veins, and run anterior to the arteries; left renal vein crosses anterior to aorta but posterior to the SMA, and can be compressed by aneurysms in either vessel
Describe the ureters
muscular tubes transporting urine from kidneys to the bladder; continuous with the renal pelvis - formed by the condensation of 2/3 major calices
Describe the uteropelvic junction
: narrowing of the renal pelvis where it becomes continuous with the ureter
Describe the course of the ureters
descend retroperitoneally on the medial aspect of Psoas major to the pelvic brim, where they cross the common iliac/proximal end of the external iliac artery to enter the pelvic cavity and enter the bladder (at the level of the ischial spine)
Describe the sites of constrictions of the ureters
Ureteropelvic junction
Point of crossing the common iliac vessels at the pelvic brim
Entrance to the bladder
Urinary stones: will cause renal colic at these constrictions as painful stimulus as passes tight area
Descirbe the blood supply of the ureters
Vasculature: renal arteries, abdominal aorta and internal iliac arteries all branch to supply
Describe innervation of the ureters
renal, aortic and sup/inferior hypogastric plexuses all innervate (visceral efferents from both SNS and PSNS sources - visceral afferents return to T11-L2 leading to referred pain at their dermatomes - e.g. Posterolateral abdominal wall pain)
Describe the suprarenal glands
also enclosed within the renal fascia and separated by a thin septum, with the fused layer connecting with the transversalis fascia on the lateral abdominal wall
Where should you look for ureters on an X-ray
shadow at transverse lumbar processes
stones sometimes radiolucent
white- due to calcium
Describe kidney stones
AKA nephrolithiasis can form in kidney and enter the urinary collecting system where they may cause renal colic (loin to groin pain) and obstruct the flow of urine
small variations in pH may cause the salts to precipitate
Hematuria may be noticed
need to exclude infection
