Narrow Abdomen Flashcards
(115 cards)
1
Q
3 parietal branches of the abdominal aorta
A
inferior phrenic nerve - originates just below the diaphragm, supplying it from below
lumbar branches - four on each side supplying the abdominal wall and spinal cord
median sacral - artery arising from the middle of the aorta at its lowest part
2
Q
3 paired visceral branches of the abdominal aorta
A
Middle suprarenal - to adrenal gland
renal - at the transpyloric plane
gonadal arteries at L2
3
Q
3 unpaired visceral branches of the abdominal aorta
A
Coeliac trunk - upper border of L1
SMA - Lower L1
IMA - L3
4
Q
Arterial supply of the colon - description
A
- Caecum to the splenic flexure is midgut (supplied by the SMA), then becomes the hindgut (supplied by the IMA)
- Part of the rectum is supplied by the internal iliac system and this anastamoses with the lower branches of the inferior mesenteric system
- Arteries pass between layers of mesentery
- Arterial anastamoses occur throughout
5
Q
Branches of the SMA
A
• inferior pancreaticoduodenal artery
• jejunal branches
• ileal branches
• ileocolic artery
o ileal branch that supplies the terminal ileum
o colic branch that supplies the proximal ascending colon
o anterior and posterior caecal arteries
o appendicular artery
• right colic artery
o descending branch that supplies the lower portion of the ascending colon
o ascending branch which supplies the upper portion of the ascending colon
• middle colic artery
o right branch supplies the right portion of the transverse colon
o left branch supplies the left portion of the transverse colon
6
Q
IMA branches
A
• left colic artery o ascending branch o descending branch • two-to-four sigmoid arteries • superior rectal artery o terminal branch of the IMA o divides into two terminal branches which descend on each side of the rectum
7
Q
Marginal artery of Drummond
A
• continuous arterial circle along the inner border of the colon formed by the anastomoses of the terminal branches of the SMA and IMA
• straight vessels (vasa recta) pass from this marginal artery to the colon
• important connection between the SMA and IMA providing collateral flow in the event of occlusion or significant stenosis
• junction of the SMA and IMA territories is at the splenic flexure
o anastomoses here are often weak or absent, hence the marginal artery at this point (known as Griffiths point) is often focally small or discontinuous
o for this reason, the splenic flexure is a watershed area prone to ischaemia / infarction
8
Q
Arterial supply to the liver - description
A
- Common hepatic artery is a terminal branch of the coeliac artery
- Proper hepatic artery is a branch of the common hepatic artery
- The proper hepatic artery runs with the portal vein and the CBD in the hepatoduodenal ligament to the porta hepatis
- It terminates by bifurcating into the right and left hepatic arteries before entering the porta hepatitis of the liver
- Variations of arterial supply to the liver are common (50% of people)
9
Q
Variations of arterial supply of the liver
A
Common hepatic artery:
• arising from the from aorta (2%)
• arising from the from SMA (2%)
• trifurcation into RHA, LHA and GDA (~6%)
Right hepatic artery (RHA):
• arising from the coeliac trunk (2.5%)
• arising from the SMA (12.5%) - most common
• accessory RHA from SMA (4%)
Left hepatic artery (LHA):
• arising from the left gastric artery (7.5%) - second most common
• accessory LHA from LGA (7.5%)
Right and left hepatic arteries:
• RHA from SMA and LHA from LGA (1%)
• accessory RHA from SMA and accessory LHA from LGA (1%)
10
Q
Course/relation of the renal arteries
A
- right renal artery courses inferiorly and passes posterior to the IVC and the right renal vein to reach the renal hilum
- left renal artery passes more horizontally, posterior to the left renal vein to enter the renal hilum
- ureter is most posterior structure in the renal hilum
11
Q
Course/relation of the renal veins
A
- emerges from the renal hilum anterior to the renal artery
- drains into the inferior vena cava at the level of L2
- left renal vein is much longer (6-7cm) than the right renal vein (3-4cm)
- the left renal vein courses anteriorly to the abdominal aorta, under the SMA
- At the hilum, the order from superficial to deep is vein, artery, ureter
12
Q
Branches of the renal artery
A
- inferior adrenal artery
- capsular artery
- ureteric artery
- terminates by dividing into dorsal and ventral rami
13
Q
Tributaries of the renal vein
A
• left renal vein:
o left gonadal vessel
o left adrenal vein
o sometimes left inferior phrenic
o small branches from kidney capsule, proximal ureter and renal pelvis
• right renal vein
o small branches from kidney capsule, proximal ureter and renal pelvis
14
Q
Variations of the renal artery
A
• early / perihilar branching
• accessory renal arteries
o can sub-categorize
o accessory artery - supplying the renal hilum
accessory renal arteries most commonly arise from abdominal aorta but can arise from coeliac trunk, SMA, middle colic
o aberrant renal artery - supplying inferior pole (more common)
15
Q
Variations of the renal vein
A
- retroaortic left renal vein - renal vein courses behind the aorta to empty into the IVC
- circumaortic left renal vein - forms collar around the abdominal aorta
- supernumerary renal veins - can affect either kidney
- Nutcracker syndrome: compression of the left renal vein between the SMA and aorta, can cause venous hypertension
16
Q
Bowel variants
A
Intestinal malrotation:
• Congenital anomaly of rotation of the midgut
• Predispose to midgut volvulus and internal hernias
• Non-rotation is a subtype of malrotation
Situs inversus:
• Congenital condition in which the major visceral organs are reversed or mirrored from their normal positions
Caecal variants:
• Subhepatic caecum: failure of the caecum to migrate to its typical position during midgut rotation in embryogenesis
• Mobile caecum: incomplete fixation to the retroperitoneum due to right colonic mesentery failing to fuse to the lateral peritoneum
17
Q
Caecum - description
A
- Caecum is a blind-ending sac of bowel, the first part of the large bowel, and lies in the right lower quadrant of the abdomen
- Superior margin of the caecum is defined by the ileocaecal ostium
- Upper and lower flaps consisting smooth muscle protrude into the lumen around the ostium forming the ileocaecal valve
- Above which the large intestine continues as the ascending colon
- Caecum measures 6cm in length and can have a maximum diameter of 9cm before it is considered abnormally enlarged
- Appendix typically arises from the posteromedial surface, 2cm inferior to the ileocaecal valve
- Caecum is covered in peritoneum, except posteriorly
- Three longitudinal bands (taenia coli) start from the appendix
- The wall is composed of four coats: serosa, muscularis externa, submucosa and mucosa
18
Q
Caecum - relations
A
- Anterior - parietal peritoneum, anterior abdominal wall and loops of small bowel
- Posterior - iliacus muscle, psoas muscle, femoral nerve, lateral cutaneous nerve of the thigh, appendix (variable)
- Medial - ileocaecal valve, terminal ileum, external iliac vein and artery, right ureter
- Superior - ascending colon
- Inferior - lateral third of the inguinal ligament
19
Q
Caecum - neurovasculature
A
Arterial supply:
• Ileocolic artery giving the anterior and posterior caecal arteries
Venous drainage:
• Anterior and posterior caecal veins to the SMV (a tributary of the portal venous system)
Lymph drainage:
• Paracolic lymph nodes which drain to the superior mesenteric lymph node group
Nerve supply:
• Sympathetic supply via superior mesenteric plexus
• Parasympathetic supply via pelvic splanchnic nerves (from S2-S4)
• Enteric nervous system
20
Q
Caecal - variations
A
- Subhepatic caecum - failure of the caecum to migrate to its typical position during midgut rotation in embryogenesis
- Mobile caecum - incomplete fixation to the retroperitoneum due to right colonic mesentery failing to fuse to the lateral peritoneum
- Retrocaecal, subcaecal, paracaecal, preileal, postileal and pelvic variation of the appendix
21
Q
Common bile duct - description
A
- Transmits bile into the duodenum
- Along with the cystic duct makes up the extra-hepatic bile ducts
- Cystic duct + common hepatic duct = CBD
- CBD is approximately 8cm long and usually <6mm wide in diameter
22
Q
Common bile duct - course/relation
A
- The CBD travels initially in the free edge of the lesser omentum (with proper hepatic artery and the portal vein)
- Then courses posteriorly to the duodenum and pancreas to unite with the main pancreatic duct to form the ampulla of Vater
- Drains at the major duodenal papillae on the medial wall of the D2 segment of the duodenum
- Calot triangle (relation)
23
Q
Common bile duct - arterial supply
A
- Upper part: cystic artery
* Lower part: superior pancreatico-duodenal artery
24
Q
Common bile duct - variants
A
• Four main relationships of the CBD with the pancreatic head:
o partially covered posteriorly (most common ~50%)
o completely covered
o completely uncovered
o CBD may pass laterally to the pancreatic head (least common)
25
Duodenum - Description
* Duodenum is the first part of the small intestine and is the continuation of the stomach
* Duodenum is a 20-30cm C-shaped hollow viscus
* Lies at the level of L1-3
* Convexity of the duodenum usually encompasses the head of the pancreas
* Duodenum begins at the duodenal bulb and ends at the ligament of Treitz
* Continues as the jejunum (duodenojejunal / D-J flexure)
* Composed of four parts (D1-4)
* Four layers: mucosa, submucosa, muscularis propria (inner circular, outer longitudinal), adventitia
26
Course D1
o commences at the pylorus and passes backward, upward, and to the right, beneath the quadrate lobe to the body of the gall-bladder
o intraperitoneal for first 2-3 cm
27
Course D2
o descends along the right margin of the head of the pancreas, generally to the level of the upper border of the body of L3
o pancreatic duct and CBD enter the descending duodenum through the major duodenal papilla (ampulla of Vater)
o also contains the minor duodenal papilla, the entrance for the accessory pancreatic duct
o junction between the embryological foregut and midgut lies just below the major duodenal papilla
28
Course D3
o takes a second bend, and passes from right to left across the vertebral column
29
Course D4
o ascends and ends opposite L2
o unites with the jejunum, forming the duodendojejunal flexure
o DJ flexure is surrounded by a peritoneal fold containing muscle fibres (ligament of Treitz)
30
D1 relations
o anteriorly - gallbladder, quadrate lobe of liver
o posteriorly - common bile duct, portal vein, gastroduodenal artery
o superiorly - epiploic foramen
o inferiorly - pancreatic head
31
D2 relations
o anteriorly - transverse mesocolon
o posteriorly - right kidney, right ureter, right adrenal gland
o superiorly - liver, gallbladder (variable)
o inferiorly - loops of jejunum
o laterally - ascending colon, hepatic flexure, right kidney
o medially - pancreatic head
32
D3 relations
o anteriorly - small bowel mesentery root, SMA, SMV
o posteriorly - right psoas muscle, right crus of diaphragm, right ureter, gonadal vessels, aorta and IVC
o superiorly - pancreatic head / uncinate process
o inferiorly - loops of jejunum
33
D4 relations
o superiorly - stomach
o inferiorly - loops of jejunum
o posteriorly - left psoas muscle, aorta, left renal vessels
34
Duodenum - arterial supply
* Duodenal cap (first 2.5cm) - supraduodenal artery (branch of gastroduodenal artery)
* Remaining D1 to mid D2 - superior pancreaticodudenal artery (branch of gastroduodenal artery)
* Mid-D2 to ligament of Trietz - inferior pancreaticoduodenal arteries (branch of SMA)
35
Duodenum -venous drainage
* Duodenal cap (first 2.5cm) - prepyloric vein (drains to portal vein)
* Remaining duodenum - superior pancreaticoduodenal vein (drains to portal vein) and inferior pancreaticoduodenal vein (drains to SMV)
36
Duodenum - Lymph drainage
* Coeliac Nodes
| * Superior Mesenteric Nodes
37
Duodenum - nerve supply
* Sympathetic nerve fibres via coelic and superior mesenteric trunks
* Parasympathetic nerve fibres via anterior and posterior vagal trunks
* Enteric nervous system
38
Duodenum Variants
• Duodenal diverticulum - most commonly occurs in D2 or D3
• Duodenal duplication - most commonly occurs at the medial wall of D2 or D3
o appears as a cystic structure that does not communicate with the lumen
• Malrotation
• Duodenal atresia
• Third part can cross as low as L4
39
Epiploic foramen boundaries
Borders:
• Anterior: the free border of the lesser omentum (hepatoduodenal ligament)
o this has two layers and within these layers are the CBD, proper hepatic artery and portal vein (DAVE: Duct, Artery, Vein, Epiploic foramen)
o hepatoduodenal ligament + hepatogastric ligament = lesser omentum
• Posterior: the peritoneum covering the inferior vena cava
• Superior: the peritoneum covering the caudate lobe of the liver
• Inferior: the peritoneum covering the commencement of the duodenum and the hepatic artery
o hepatic artery passes forward below the foramen before ascending between the two layers of the hepatoduodenal ligament
• Left lateral: gastrosplenic ligament and splenorenal ligament
40
Gallbladder - description
• The gall-bladder is a pear-shaped musculomembranous sac
• Divided into a fundus, body, and neck
• Extends from the right border of porta hepatis, inferolaterally
• Gallbladder consists of four layers: serosa, muscularis externa, lamina propria, mucosa
• The cystic duct connects the neck of the gallbladder to the common hepatic duct
• Calot's triangle is an anatomic space bordered by the CHD medially, the CD laterally and inferior border of liver
o contains Lund's node (lymph node) which may enlarge in cholecystitis
o may contain cystic artery, accessory right hepatic artery or anomalous bile ducts within triangle (important surgical implications)
41
Gallbladder - relations
* Superiorly: liver
* Inferiorly: transverse colon, D2 segment of the duodenum (or pylorus of the stomach)
* Anteriorly: liver, transverse colon, 9th costal cartilage
* Medial: IVC
* The cystic duct travels alongside the cystic artery
42
Gallbladder - neurovasculature
Arterial supply:
• Cystic artery (branch of right hepatic artery)
Venous drainage:
• Cystic vein drains directly into the right portal vein
Lymph drainage:
• Nodes at the porta hepatis and portal nodes
• Subsequently to the coeliac lymph nodes
Nerve supply:
• Sympathetic: coeliac plexus (passes along the cystic artery)
• Parasympathetic: vagus nerve
43
Gallbladder - variant anatomy
• Morphology
o Phrygian cap: the fundus is sometimes folded back upon itself
o Hartmann pouch (infundibulum): neck is focally dilated and probably pathological / related to cholelithiasis
• Number
o accessory gallbladder
gallbladder bifid / duplication / triplication
cystic duct may also be duplicated / tripled
gallbladder agenesis
• Location
o left-lobe > intrahepatic > retrohepatic
44
Cystic duct
o low cystic duct insertion - into the distal-third of the CHD
o medial cystic duct insertion - into the left, not the right, side of the CHD
o parallel cystic duct course - courses parallel to the CHD for at least 2cm
o cystic duct empties into the right posterior hepatic duct
45
Locations of hernas
A: epigastric - through a defect in linea alba superior the umbilicus
B: incisional - widening / dehiscence of the scar allows intra-abdominal content to herniate into the subcutaneous tissues
C: umbilical - at the umbilicus in the midline
D: direct - through a weakness of the posterior wall of the inguinal canal medial to the inferior epigastric vessels (through the Hesselbach's triangle)
E: indirect - protrude through the deep or internal inguinal ring into the inguinal canal (lateral to the Hesselbach's triangle)
F: femoral - through the femoral ring into the femoral canal, posterior and inferior to the inguinal ligament
46
Inguinal triangle
* Medial border: lateral margin of the rectus sheath (linea semilunaris)
* Superolateral border: inferior epigastric vessels
* Inferior border: inguinal ligament
47
IMA - origin, termination, supply
Origin:
• Arising from abdominal aorta at the level of L3
• Close to the lower border of D3
Termination:
• Terminates as the superior rectal artery
Supply:
• Hindgut (distal third of the transverse colon to the rectum)
48
IMA - course/relations
* Artery descends anteriorly to the aorta
* Then passes to the left as it continues inferiorly
* Crosses the left common iliac artery and continues into the pelvis as the superior rectal artery
49
IMA - branches
• Left colic artery
o ascending and descending branches
• Two-to-four sigmoid arteries
• Superior rectal artery (terminal branch)
o anastamoses with middle and inferior rectal arteries
• Terminal branches of the ileocolic, right, middle, left colic and sigmoid branches form a continuous arterial arcade along the inner border of the colon known as the marginal artery of Drummond with straight arteries known as vasa recta
50
IMA - variants
* Absent IMA with all its given off by the SMA
* Arises from a common trunk with the SMA
* May gives extra branches (eg. middle colic or "accessory" renal artery)
* Arc of Riolan (second anastamosis in addition to drummond collateral)
51
IVC - Description/features
• IVC drains venous blood from the lower trunk, abdomen, pelvis and lower limbs to the right atrium of the heart
52
IVC - Origin and course
Origin:
• Formed by the confluence of the two common iliac veins at the L5 vertebral level
Course:
• IVC has a retroperitoneal course within the abdominal cavity
• Runs along the right side of the vertebral column
• Passes through the diaphragm at the caval hiatus at the T8 level
• Has a short intra-thoracic course before draining into the right atrium
53
IVC -relations
* Anterior: right common iliac artery, mesentery, right gonadal artery, third part of the duodenum, pancreas, posterior surface of the liver
* Posterior: vertebral column, right crus of the diaphragm, right inferior phrenic / adrenal / renal and lumbar arteries, right sympathetic trunk
* Right: right kidney, right ureter, right adrenal
* Left: aorta
54
IVC - Tributaries
* T8: paired inferior phrenic veins
* T8: hepatic veins (3)
* L1: right adrenal vein
* L1: renal veins
* L2: right gonadal vein
* L1-L4: lumbar veins
* L5: common iliac veins (origin)
55
IVC - variants
• IVC duplication: IVC continues on both sides of aorta
• Transposition of IVC: only one IVC on the left side of the aorta
• Azygos continuation of the IVC
o differential for dilated azygos vein
o hepatic segment of the IVC is absent
o hepatic veins join and drain directly into the right atrium
• Circumcaval ureter: IVC develops passing infront of the ureter, so ureter initially courses behind IVC
56
Morrisons pouch - decription
* Also known as posterior right subhepatic space and hepatorenal fossa
* Potential space with no contents in normal conditions
* Communicates with the right subphrenic space and right paracolic gutter
* Communicates with the lesser sac via the foramen of Winslow
* Fluid accumulates here as it is the lowest dependent spaces
* Also a preferential site for metastases and abscesses
57
Morrison's pouch - boundaries
* Anterior: right lobe of the liver and gallbladder
* Posterior: superior aspect right kidney, right adrenal gland, second part of the duodenum, hepatic flexure, pancreatic head
* Superior: transverse mesocolon
58
Oesophagus - nerves
- Vagus
- ,Sympathetics
- Meisners
- Aubachs
59
Oesophagus - arteries
- Superior and inferior thyroid
- Direct from aorta
- Left gastric
60
Oesophagus - veins
- ?inferior thyroid
- Azygous/hemiazygous/?accessory
- Left gastric
61
Oesophagus - lymphatics
- Cervical
- Anterior/posterior mediastinum
- Gastric/coeliac
62
Oesophagus - muscles and lyaers
- Constrictors
- Cricopharyngeous
- Mucosa
- Sub mucosa
- Transverse muscle
- Longitudinal muscle
- Outer connective tissue (thin unlike true serosa)
63
Oesophagus - relations
- Azygous crossing
- Thoracic duct
- Lymph nodes (especially sub carinal and just before hiatus
- Aorta
- Trachea
- ?Superiorly
- Heart
64
Pancreas - description
• The pancreas is a exocrine and endocrine gland
o serous acini and endocrine Islets of Langerhans
acini secrete various digestive enzymes
alpha islets secrets glucagon, beta islets secrete insulin, delta islets secrete somatostatin
• Consists of a head, neck, body and tail
• The uncinate process projects left from its lower part
• Situated at approximately L1 and lies obliquely
• Pancreatic duct travels through pancreatic substance
o reaches neck and turns inferiorly and ends at a common orifice with the common bile duct at the major duodenal papilla (7.5-10 cm distal to the pylorus)
o accessory pancreatic duct (of Santorini) open into the duodenum ~2.5 cm proximal to duodenal papilla
• Mostly retroperitoneal, except tail
• Embryology: dorsal and ventral buds fuse
65
Pancreas head - relations
o Lodged within the curve of the duodenum
o Posterior: aorta, IVC, CBD, right renal vessels, right crus of the diaphragm, SMA, SMV
uncinate process passes posterior to the SMV and SMA
o Anterior: small bowel
66
Pancreas neck - relations
o Antero-superiorly: pylorus
| o Posterior: commencement of the portal vein
67
Pancreas body -relations
o Anterior: lesser sac
o Posterior: splenic vein, left kidney, left renal vessels, left suprarenal gland
o Superior: splenic artery
68
Pancreas tail - relations
o Extends to the splenic hilum
| o Lies within the lienorenal ligament
69
Pancreas - neurovasculature
Arterial supply:
• Branches from the Splenic Artery
• Superior Pancreaticoduodenal Artery (Gastroduodenal Artery)
• Inferior Pancreaticoduodenal Artery (SMA)
Venous drainage:
• Drains to the SMV and splenic veins and ultimately portal vein
Lymphatic drainage:
• Coeliac / Superior Mesenteric Nodes
Nerve supply:
• Spinal Cord Segment T6 to T10
• Vagal Trunks
70
Pancreas variants
* Pancreas Divisum: MPD drains at minor duodenal papilla (incomplete: communication with duct of Wirsung vs complete: no communication with duct of Wirsung)
* Annular Pancreas: ventral pancreatic bud fails to rotate resulting in ring of pancreatic tissue around second part of duodenum
* Agenesis of Dorsal Pancreas: failure of the dorsal pancreatic bud to form the body and tail of the pancreas
* Ectopic Pancreas: gastric antrum, proximal duodenum, ileum, Meckel's diverticulum
* Bifid tail of pancreas / fishtail pancreas: rare branching anomaly of pancreatic tail and duct system
71
Inferior phrenic arteries - course
o left inferior phrenic passes behind the esophagus, and runs forward on the left side of the esophageal hiatus
o right phrenic passes behind the inferior vena cava and along the right side of the vena caval foramen
o near the back part of the central tendon each vessel divides into a medial and a lateral branch
medial branch curves forward, and anastomoses with its fellow of the opposite side, and with the musculophrenic and pericardiacophrenic arteries
lateral branch passes toward the side of the thorax, and anastomoses with the lower intercostal and musculophrenic arteries
lateral branch of the right inferior phrenic gives off a few vessels to the IVC; and the left gives branches to the esophagus
72
Lumbar arteries - course/relations
o usually 4 paired arteries
o run lateral and backward on the bodies of the lumbar vertebrae → behind the sympathetic trunk → to the intervals between the adjacent transverse processes → arteries of the right side pass behind the IVC / upper two lumbar arteries on each side run behind the corresponding crus of the diaphragm → pass beneath the tendinous arches which give origin to the psoas major → continues behind psoas and the lumbar plexus → behind the quadratus lumborum (upper three arteries running behind, last usually in front of the muscle) → at the lateral border of the quadratus lumborum they pierce the posterior aponeurosis of the transversus abdominis → travel forward between transversus abdominis and the internal oblique
o anastomose with the lower intercostal, the subcostal, the iliolumbar, the deep iliac circumflex and the inferior epigastric arteries
73
Median sacral artery - course/relations
o arises posterior to the abdominal aorta and superior to its bifurcation
o descends in the middle line in front of the fourth and fifth lumbar vertebra, the sacrum and coccyx
o small branches pass to the posterior surface of the rectum
o on the last lumbar vertebra it anastomoses with the lumbar branch of the iliolumbar artery
o in front of the sacrum it anastomoses with the lateral sacral arteries
o crossed by the left common iliac vein
74
Parietal branches of the abdominal aorta - supply
* Inferior phrenic: thoracic diaphragm
* Lumbar: quadratus lumborum
* Median sacral: lumbar vertebrae, saccrum, coccyx
75
Parietal branches of the abdominal aorta - variants
• Lumbar arteries
o Adamkiewicz artery sometimes arises from a lumbar artery
• Inferior phrenic arteries
o may arise from a common trunk, which may spring either from the aorta or from the coeliac artery
o arise from renal artery
• Median sacral artery
o fifth pair of lumbar arteries sometimes arise from median sacral artery
76
Portal vein - description
• A vessel that drains blood from the gastrointestinal tract and spleen to the liver
• Measures approximately 8 cm in adults
• 75% of the blood supplied to the liver comes from the portal vein, but it only supplies 50% of the oxygen supply to the liver
Origin:
• Formed by superior mesenteric and splenic veins at the level of L2
77
Portal vein - course
* Formation takes place in front of the inferior vena cava and behind the neck of the pancreas
* It passes upward behind the first part of the duodenum and then in the free border of the lesser omentum (with the CBD and proper hepatic artery)
* It receives the left / right gastric veins
* At the right extremity of the porta hepatis it divides into a right and a left branch
78
Portal vein - tributaries
* Splenic vein
* SMV
* Cystic vein (to right branch of portal vein)
* Paraumbilical veins (left branch of portal vein)
* Left and right gastric veins
* Superior pancreatico-duodenal vein
* Supraduodenal veins
79
Portal vein - supply
• Left portal vein (supplying liver segments II, III, IV)
• Right portal vein divides into 2 branches
o anterior supplies liver segments V and VIII
o posterior supplies liver segments VI and VII
80
Portal vein - variants
• Increased risk of bile duct hilar anatomical variation in the presence of portal vein variants
• Portal vein trifurcation is most common variant
o Portal vein divides into three branches; the left, right anterior and right posterior
• Right Posterior Portal Vein as the first branch of the main Portal Vein
• Enters porta hepatis anterior to bile duct / hepatic artery
• Direct Drainage of IMV into Portal Vein
• Drainage of SMV or Splenic vein into the Renal veins
81
Quadratus lumborum
Description/Features:
• Psoas major muscle is a muscles of the posterior abdominal wall
• Lies in the iliopsoas compartment (posterior to the retroperitoneum)
• Fuses with the iliacus muscle to form the iliopsoas muscle at the level of L5-S2
• Passes deep to the inguinal ligament
• Psoas muscle is enclosed by the psoas fascia, therefore pus is contained in a psoas abscess
Origin:
• Vertebral bodies, intervertebral discs and transverse processes of T12 to L5
Insertion:
• Lesser trochanter of the femur
Action:
• Lateral flexion of the trunk
• Stabiliser and flexor of the hip
Relations:
• The lumbar plexus is embedded within the muscle and its branch emerge from it:
o anterior aspect: genitofemoral nerve
o lateral border: iliohypogastric, ilioinguinal, lateral femoral cutaneous and femoral nerves
o medial border: obturator nerve and lumbosacral trunk
• Forms floor of the femoral triangle: femoral vein, artery, nerve, lymphatics
Nerve supply:
• L1-L3 roots of the lumbar plexus
Blood supply:
• Lumbar branch of the iliolumbar artery
Variation:
• Asymmetry (no clinical significance)
82
Rectus abdominis - description
* Rectus abdominis forms part of the anterior abdominal wall
* Enclosed by the rectus sheath
* Strap-like in appearance
* 3-4 tendinous insertions that divide the muscle into segments, which are often incomplete posteriorly (linea semilunares)
* Divided into two halves by the linea alba
83
Rectus abdominis - origin/insertion
```
Origin:
• Pubic symphysis, tubercle and crest
Insertion:
• Xiphisternum
• 5th-to-7th costal cartilages
```
84
Rectus abdominis - action
* Flexion of the lumbar spine
| * Compression of the abdomen
85
Rectus abdominis - neurovasculature
Arterial supply:
• Superior and inferior epigastric arteries
Innervation:
• Anterior rami of T6-L1 spinal nerves (thoracoabdominal nerves)
86
Rectus sheath - description
• Important component of the anterior abdominal wall
• Composed of the aponeuroses of external oblique, internal oblique and transversus abdominis
o which form an anterior and posterior sheath that fuse laterally at the linea semilunaris and in the midline at linea alba
o anterior layer formed by external oblique aponeurosis and anterior layer of internal oblique aponeurosis
o posterior layer formed by transversus abdominis aponeurosis and posterior layer of internal oblique aponeurosis
o posterior layer has a free inferior margin, the arcuate line (halfway between the umbilicus and pubic symphysis)
below this point all three aponeuroses pass anterior to the muscle
posterior surface of rectus abdominis is in contact with the transversalis fascia
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Rectus sheath - contents
o rectus abdominis
origin - pubic symphysis, tubercle and crest
insertion - xiphisternum and 5th to 7th costal cartilages
blood supply - superior and inferior epigastric arteries
nerve supply - thoracoabdominal (T6-T11)
o pyramidalis muscles
o lower six costal nerves
o intercostal vessels
o superior and inferior epigastric arteries
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Rectus sheath - layers
o external oblique
origin - ribs 5-12
insertion - iliac crest, pubic tubercle, linea alba
blood supply - subcostal arteries, deep circumflex iliac artery, iliolumbar artery
nerve supply - thoracoabdominal (T6-T11), subcostal (T12)
o internal oblique
origin - iliac crest, inguinal ligament, lumbodorsal fascia
insertion - linea alba, ribs 10-12
blood supply - subcostal arteries
nerve supply - thoracoabdominal (T6-T11), subcostal (T12), iliohypogastric nerve (L1), ilioinguinal nerve (L1)
o transverse abdominis
origin - iliac crest, inguinal ligament, thoracolumbar fascia, costal cartilages 7-12
insertion - xiphoid process, linea alba, pubic crest
blood supply - subcostal arteries
nerve supply - thoracoabdominal (T6-T11), subcostal (T12), iliohypogastric nerve (L1), ilioinguinal nerve (L1)
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Retroperitoneal spaces
• Retroperitoneum is the part of the abdominal cavity that lies between the posterior parietal peritoneum and anterior to the transversalis fascia
• Divided into three spaces by the perirenal fascia
o anterior pararenal space
o perirenal space
o posterior pararenal space
o the great vessel space could be considered a fourth space
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Anterior Pararenal Space
• Lies between the posterior surface of the parietal peritoneum and the anterior perirenal fascia
• Contains: duodenum, pancreas, retroperitoneal segments of the ascending and descending colon, roots of the small bowel mesentery and transverse mesocolon
• Little fat within the compartment (difficult to visualise on cross sectional imaging in normal anatomy)
• Bound by:
o anteriorly: parietal peritoneum
o posteriorly: Gerota's fascia
o medially: continuity with the other side
o laterally: the compartment is limited as the lateroconal fascia and parietal peritoneum merge
o superiorly: diaphragm, but communicates via the diaphragmatic openings
o inferiorly: continuous with the pelvis
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Perirenal Space
• Perirenal space is the largest of the three areas in the retroperitoneum
• Surrounded by the perirenal fascia
o posterior: Zuckerkandl's fascia
o anterior: Gerota's fascia
o laterally: lateroconal fascia
o superior: bare area of liver (right), diaphragm (left)
• Continuous with the opposite perirenal space across the midline
• Abuts the bare area of the liver on the right and the subphrenic space on the left
• Mediastinal communication via the various diaphragmatic hiatus
• Does not communicate with the pelvis
• Contains: kidneys, adrenal glands
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Posterior Pararenal Space
• Smallest portion of the retroperitoneum
• Filled with fat, blood vessels and lymphatics (no major organs)
• Bound by:
o posterior: transversalis fascia
o anteriorly: posterior perirenal fascia (Zuckerkandl's fascia)
o medially: fusion of the posterior perirenal and transversalis fascia with muscular fascia
o cranial extent: determined by the fusion of psoas and quadratus lumborum with the inferior phrenic fascia
o inferiorly: open into the pelvis
• Rarely subject to involvement in disease processes except where spread is from adjacent structures
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Segmental liver anatomy
• Couinaud classification divides liver into eight independent functional units
o separation of the units is based on the fact that each has its own vascular inflow, outflow, biliary and lymphatic drainage
o in the centre of each segment there is a branch of the portal vein, hepatic artery and bile duct
o in the periphery of each segment there is vascular outflow through the hepatic veins
• Middle hepatic vein divides the liver into right and left lobes
o this plane runs from the IVC to the gallbladder fossa (ie. Cantlie's line)
• Right hepatic vein divides the right lobe into anterior and posterior segments
• Left hepatic vein divides the left lobe into a medial and lateral parts
• Portal vein divides the liver into upper and lower segments
o the left and right portal veins branch superiorly and inferiorly to project into the centre of each segment
• Segment I is the caudate lobe and is situated posteriorly
o may receive its supply from both left and right branches of portal vein
o contains one or more hepatic veins which drain directly into the IVC
• Superior: 2, 4A, 8, 7
• Inferior: 3, 4B, 5, 6
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Spleen - description
• The spleen is involved in storage of RBC and WBC, immune responses and sequestration of RBC's
• Spleen is composed of red and white pulp
o red pulp consists primarily of blood vessels (splenic sinusoids)
o white pulp consists primarily of lymphoid tissue
• Measures approximately 12 x 7 x 3 cm, and weighs about 200 grams
• Lies in the left upper quadrant
• Spleen is almost entirely surrounded by peritoneum
• Lienorenal ligament joins the the left kidney and the spleen
o the splenic vessels pass between its two layers to the hilum
o ligament also contains tail of the pancreas (the only intraperitoneal portion)
• Gastrosplenic ligament joins the spleen and stomach
o the short gastric and left gastroepiploic vessels course through this
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Spleen - embryology
* Spleen appears about the fifth week as a localized thickening of the mesoderm in the dorsal mesogastrium
* With rotation of the foregut the spleen is carried to the left
96
Spleen - relations
* Superior: under surface of the diaphragm
* Medial: posterior wall of the stomach, tail of the pancreas
* Inferior: left colic flexure
* Posterior: anterior surface of the left kidney and suprarenal gland
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Spleen - neurovasculature
Arterial supply:
• Splenic artery
o at the splenic hilum the splenic artery divides into superior and inferior terminal branches
each terminal branch further dividing into four-to-six intrasplenic segmental branches
Venous drainage:
• Splenic vein
Lymphatic drainage:
• Lymph drains into several nodes lying at the splenic hilum and subsequently to the coeliac nodes
Nerve supply:
• Sympathetic only: coeliac plexus
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Spleen - variants
• Accessory spleen (splenunculus) (~10%)
o most commonly in the splenic hilum with a mean size of 10mm
• Multiple Spleens (polysplenia)
• Asplenia (anatomical vs functional)
• “Wandering” Spleen
o Rare condition; spleen migrates from its usual anatomical position, commonly to the lower abdomen or pelvis
99
SMA - origin, termination
Origin:
• Arising anteriorly from abdominal aorta at the level of L1
Termination:
• SMA terminates at the ileum where it anastomoses with the ileal branch of the ileocolic artery
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SMA - course
• Courses anteroinferiorly
• Behind the neck of pancreas and splenic vein
• Crossing anterior to the left renal vein
• Emerges anterior to the uncinate process of the pancreas
• Crosses anterior to D3
• Superior mesenteric vein (SMV) should always lie to the right of the SMA
o otherwise malrotation should be suspected
• Enters the upper portion of the small bowel mesentery and runs along the root of the mesentery downwards to the right
• Other relations: anterior to right ureter, origin is inferior to coeliac trunk
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SMA - branches
• Inferior pancreaticoduodenal artery
o anastomoses with the superior pancreaticoduodenal artery and supplies the head of the pancreas, D2 and D3
• Jejunal branches
• Ileal branches
• Ileocolic artery
o ileal branch, colic branch, anterior and posterior caecal branches, appendicular branch
• Right colic artery
o ascending and descending branches
• Middle colic artery
o left and right branches
• Terminal branches of the ileocolic, right colic and middle colic arteries - along with the terminal branches of the left colic artery and sigmoid branches of the IMA - form a continuous arterial arcade along the inner border of the colon known as the marginal artery of Drummond with straight arteries known as vasa recta
• Jejunal and ileal branches also form a series of anastomosing arcades from which vasa recta arise
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SMA - variations
• SMA may arise from the aorta as two trunks
• SMA sometimes arises from, or has common trunk with, the coeliac trunk
• May give rise to branches usually derived from other sources:
o right hepatic
o accessory right hepatic
o gastroduodenal
o IMA
o left colic
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SMV - course
• Mesenteric venous arcades (which accompany the arteries) unite to form the jejunal and ileal veins in the small bowel mesentery
• Ascends between the two layers of the mesentery on the right side of the superior mesenteric artery
o if it is not in this position, it can indicate intestinal malrotation
• SMV is considered the common trunk after all the chief tributaries have joined
• Gastrocolic trunk drains into the right-hand aspect of the SMV just anterior to the uncinate process of the pancreas
• Unites with the splenic vein posterior the neck of the pancreas (at the level of L1) to form the portal vein
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SMV - tributaries
• Mesenteric venous arcades (jejunel and ilieal veins)
• Ileocolic vein
• Right colic vein
• Middle colic
• Inferior pancreaticoduodenal vein
• Gastrocolic trunk:
o right gastroepiploic vein: runs between two layers of greater omentum
o anterior superior pancreaticoduodenal vein
105
SMV - relation
* Anterior: neck of pancreas
* Posterior: uncinate process of pancreas, right renal vessels
* Left: SMA
106
SMV - variants
* Absence of common draining trunk with two "intestinal trunks" draining directly into the splenic vein (~10%)
* SMV may receive an accessory splenic vein
* May drain into the a renal vein
* Pancreaticoduodenal veins may drain into it directly
* IMV may empty into the SMV
* Ascends on the left of SMA in malrotation
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Adrenal - Description
* The adrenal glands are paired endocrine glands
* They lie retroperitoneally on top of each kidney
* Each gland is enclosed within the perirenal fascia in a separate compartment from the kidney
* Two limbs - medial and lateral
* Right adrenal gland is pyramidal in shape, left adrenal gland is crescenteric
* Thick outer cortex and a thin inner medulla
* Surrounded by a fibrous capsule
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Adrenal - relations
• Right Adrenal Gland
o medial: right crus of the diaphragm, right inferior phrenic nerve
o lateral: right lobe (bare area) of the liver
o anterior: IVC
o inferior: right kidney
• Left Adrenal Gland
o medial: left crus of the diaphragm, left inferior phrenic nerve
o superior: diaphragm
o anterior: lesser sac, stomach, splenic artery, pancreas
o inferior: left kidney
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Adrenal - neurovasculature
Arterial supply:
• Superior adrenal artery - Branch of the Inferior Phrenic Artery
• Middle adrenal artery - Branch of Abdominal Aorta
• Inferior adrenal artery - Branch of Renal artery
Venous drainage:
• Mainly by single adrenal vein
o Left adrenal vein drains into the left renal vein
o Right adrenal vein drains into the IVC
Lymphatic drainage:
• Para-aortic Lymph Nodes
Nerve supply:
• Splanchnic nerves from the Coeliac and Renal Plexuses
110
Adrenal - variants
* Horseshoe adrenal gland: solitary adrenal gland that is present in the midline
* Pancake adrenal gland: takes on a flattened appearance, often in the presence of a pelvic kidney or renal agenesis
* Adrenal gland hypoplasia/agenesis
* Accessory adrenal glands: often near adrenal glands but may be found anywhere in the abdomen, pelvis or scrotum
111
Ureters - descriptions
• Paired fibromuscular tube that conveys urine from the kidneys in the abdomen to the bladder in the pelvis
• It is 25-30cm long and has three parts:
o abdominal ureter: from the renal pelvis to the pelvic brim
o pelvic ureter: from the pelvic brim to the bladder
o intramural ureter: within the bladder wall
• Ureter peristalsis (vermiculation) dependent on haemodynamic forces
• Ureteric wall is composed of three layers: adventitia, smooth muscle and urothelium (transitional cell epithelium)
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Ureters - course
• Runs along the medial aspect of the psoas major
o ureter lies anteriorly and slightly medial to the tips of the L2-L5 transverse processes
• Enters the pelvis anteriorly to the sacroiliac joint at the bifurcation of the common iliac vessels (at the pelvic brim) and then courses anteriorly to the internal iliac artery down the lateral pelvic sidewall
• At the level of the ischial spine it turns forward and medially to enter the posterolateral wall of the bladder
o then runs an oblique 1-2cm course before opening into the bladder at the internal ureteric orifice
o in the male
ureter crosses above the seminal vesicles and is crossed by the ductus deferens
o in the female
ureter runs medial and forward on the lateral aspect of the cervix and upper part of the vagina to reach the fundus of the bladder
here it is crossed by the uterine artery
• Constrictions of the ureter are the most common sites of stone obstruction
o pelvi-ureteric junction (PUJ)
o as the ureter enters the pelvis and crosses over the common iliac artery bifurcation
o vesicoureteric junction (VUJ)
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Ureters - relations
• Abdominal ureter
o posteriorly
psoas muscle, genitofemoral nerve, common iliac vessels, tips of L2-L5 transverse processes
o anteriorly
right ureter: descending duodenum (D2), gonadal vessels, right colic vessels, ileocolic vessels
left ureter: gonadal artery, left colic artery, loops of jejunum, sigmoid mesentery and colon
o medially
right ureter: IVC
left ureter: abdominal aorta
• Pelvic ureter
o posteriorly
sacroiliac joint, internal iliac artery
o inferiorly
male: seminal vesicle
female: lateral fornix of the vagina
o anteriorly
male: ductus deferens
female: uterine artery (in the broad ligament)
o medially
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Ureters - neurovasculature
Blood supply:
• branches of the renal artery, abdominal aorta, superior and inferior vesical arteries
Venous drainage:
• similarly named veins (but is highly variable)
Lymphatic drainage:
• Upper ureter - lateral aortic nodes
• Abdominal ureter - common iliac nodes
• Pelvic ureter - common iliac, internal iliac nodes
Nerve supply:
• Derived from renal, aortic and hypogastric autonomic plexuses
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Ureters - variants
• Duplex collecting system
o ranges from duplicated renal pelvis to duplicated ureters draining into bladder separately
o unilateral more common than bilateral
o single ureter, bifid ureter, duplicated ureter
• Ectopic ureter
o congenital renal anomaly that occurs as a result of abnormal caudal migration of the ureteral bud during its insertion to the bladder
o ureter may insert into lower urinary bladder, urethra, vestibule or vagina, seminal vesicle, vas deferens, ejaculatory duct
rarely uterus or rectum
• Ureterocoele
o congenital dilatation of the distal-most portion of the ureter
o associated with ectopic ureter and duplex collecting systems
• Retrocaval ureter
