Ch17: Abdomen II — Peritoneum & Supracolic Compartment（结肠上区）

# Ch17: Abdomen II — Peritoneum & Supracolic Compartment

Preparatory Mindset

The supracolic compartment (above the transverse colon) contains the stomach, liver, spleen, gallbladder & bile ducts, pancreas (head), and duodenum (1st-3rd parts). The peritoneum and its formations (omenta, mesenteries, omental bursa) are the organizing scaffold. The lecture's key points: (1) omental bursa & omental foramen, (2) location/ligaments/relations/blood supply of the stomach, (3) location, surface markings & relations of the liver, (4) formation of the bile system, (5) relations of the pancreas. The celiac trunk branches are MUST-KNOW.

Exam mindset: Celiac trunk branches, stomach blood supply, portal triad (hepatoduodenal ligament), bile duct formation, and the omental bursa boundaries are the classic questions. The 局解mc大全 adds bleeding gastric ulcer (left gastric artery — concept 32), pancreatic cancer (severe jaundice), and cholelithiasis (concept 44).

Core Concepts

1. Peritoneum — basic concepts (concept 30)

- Lesser omentum: from the liver (porta hepatis) to the lesser curvature of the stomach (hepatogastric ligament) & first part of duodenum (hepatoduodenal ligament) — the free right edge of the hepatoduodenal ligament contains the portal triad: common bile duct (anterior/right), proper hepatic artery (anterior/left), portal vein (posterior) — mnemonic "D-A-V" (Duct, Artery, Vein) - Greater omentum: 4-layer apron from the greater curvature hanging to the transverse colon — "abdominal policeman" (mobile, rich in vessels, walls off infection) - Omental bursa (lesser sac): behind the stomach & lesser omentum; communicates with the greater sac via the omental (epiploic) foramen of Winslow; boundaries: anterior = stomach/lesser omentum; posterior = pancreas & posterior abdominal wall; superior = liver & diaphragm; inferior = transverse colon/mesocolon - Falciform ligament: liver to anterior abdominal wall; contains the ligamentum teres (obliterated umbilical vein); subdivides the suprahepatic space - Coronary ligament & bare area of the liver - Mesenteries: mesentery (small intestine), transverse mesocolon, sigmoid mesocolon, mesoappendix

• Peritoneal cavity vs abdominal cavity: the peritoneal cavity is the potential space between parietal & visceral peritoneum within the abdominal cavity
• Intraperitoneal organs: stomach, liver, spleen, jejunum/ileum, transverse & sigmoid colon, appendix, uterus/uterine tubes, ovaries (suspended by mesenteries/ligaments)
• Retroperitoneal organs (mnemonic "SAD PUCKER"): Suprarenal glands, Aorta/IVC, Duodenum (2nd-4th parts), Pancreas (except tail), Ureters, Colon (ascending & descending), Kidneys, Esophagus (abdominal), Rectum — plus bladder, prostate
• Peritoneal formations:

2. Stomach (concept 32)

- Left gastric artery (direct celiac branch) — runs along the lesser curvature; common site of bleeding ulcer (posterior gastric ulcer may erode into the splenic artery? no — see below) - Right gastric artery (from proper hepatic) - Right gastro-omental (gastroepiploic) artery (from gastroduodenal → common hepatic) - Left gastro-omental artery (from splenic) - Short gastric arteries (from splenic — to the fundus)

• Position & relations: most of it lies under the left costal margin; anterior = anterior abdominal wall & left lobe of liver; posterior = omental bursa → pancreas, left kidney, spleen, diaphragm ("stomach bed")
• Ligaments: lesser omentum (hepatogastric), greater omentum (gastrocolic), gastrosplenic, gastrophrenic
• Blood supply (from the celiac trunk):
• Nerve supply: vagus (parasympathetic; anterior & posterior gastric nerves), sympathetic via celiac plexus
• Clinical (concept 32 — posterior gastric ulcer): a chronic posterior wall ulcer of the stomach may erode into the splenic artery (classic!) or pancreas → severe hemorrhage; pain in the back. Anterior ulcers perforate → peritonitis (free air). The MCQ: chronic gastric ulcer perforated the posterior wall & eroded the structure behind → answer often splenic artery or pancreas.
• Bleeding ulcer (MCQ): a bleeding ulcer on the lesser curvature → left gastric artery is the usual source

3. Celiac trunk (MUST KNOW)

1. Left gastric artery 2. Hepatic (common hepatic) artery → proper hepatic (→ left & right hepatic), gastroduodenal (→ right gastro-omental & superior pancreaticoduodenal), right gastric 3. Splenic artery (largest; runs along the upper border of the pancreas) → left gastro-omental, short gastrics, pancreatic branches

• Arises from the abdominal aorta at T12/L1, behind the lesser sac, just below the aortic hiatus
• Three branches (mnemonic "Left Hand Side" / "L-H-S"):
• Mnemonic: "LHS" = Left gastric, Hepatic, Splenic

4. Liver (concept 45 + lecture)

• Location: right hypochondrium & epigastrium; surface markings: upper border at 5th ICS midclavicular; lower border at right costal margin
• Lobes: right (large) & left (smaller), divided by the falciform ligament; caudate & quadrate lobes (from the bare area aspect)
• Relations: superior = diaphragm; anterior = abdominal wall; inferior = stomach, duodenum, right colic flexure, right kidney, gallbladder (visceral surface)
• Porta hepatis: portal vein (posterior), hepatic artery (anterior), bile duct (anterior) — the portal triad
• Blood supply (concept 45): portal vein (70-75%, nutrient) + hepatic artery (25-30%, oxygenated) → sinusoids → hepatic veins → IVC
• Nerve supply: hepatic plexus (sympathetic) & vagus; the liver capsule (Glisson's) is pain-sensitive (stretch → RUQ pain); parenchyma is not
• Clinical: cirrhosis → portal hypertension; HCC (see Imaging: arterial enhancement/washout); liver biopsy in the midaxillary line between ribs 9-10 (avoid pleura — costodiaphragmatic recess)

5. Gallbladder & bile system (concepts 43-44)

• Gallbladder: pear-shaped, under the liver (visceral surface, between right & quadrate lobes); parts = fundus, body, neck; fundus projects at the tip of the 9th right costal cartilage (junction of right midclavicular line & costal margin) — Murphy's sign
• Blood supply: cystic artery (from right hepatic artery, behind the cystic duct) — the triangle of Calot: cystic duct, common hepatic duct, cystic artery (containing the cystic artery & cystic lymph node of Lund)
• Bile duct formation: right & left hepatic ducts → common hepatic duct → joins the cystic duct → common bile duct (CBD) → descends behind the duodenum, through the pancreas, joins the pancreatic duct → hepatopancreatic ampulla (of Vater) → opens into the 2nd part of duodenum at the major duodenal papilla, guarded by the sphincter of Oddi
• Cholelithiasis (concept 44): gallstones — cholesterol (radiolucent, in obese "4F": female, forty, fertile, fat), pigment (bilirubin, hemolysis); obstruct the cystic duct → biliary colic (RUQ pain after fatty meal), jaundice if CBD blocked, pancreatitis if ampulla blocked; gallstone ileus (cholecystoenteric fistula)
• Clinical: CBD obstruction → obstructive jaundice (dark urine, pale stools, pruritus) + dilated ducts on US/CT

6. Pancreas (concept 47)

• Retroperitoneal, behind the omental bursa; parts = head (in the C-loop of duodenum), uncinate process, neck, body, tail (reaches the splenic hilum)
• Relations: head embraces the 2nd part of duodenum; neck behind = portal vein (SMV + splenic vein join behind it); body behind = aorta, left renal vessels, left suprarenal; tail = splenic hilum
• Ducts: main pancreatic duct (Wirsung) joins the CBD at the ampulla; accessory duct (Santorini) opens at the minor papilla
• Blood supply: superior & inferior pancreaticoduodenal arteries (gastroduodenal & SMA), pancreatic branches of splenic artery
• Clinical (MCQ): pancreatic head carcinoma → obstructive jaundice (severe, painless), Courvoisier's law (palpable, non-tender gallbladder); pancreatic cancer invades the portal vein/duodenum; acute pancreatitis (see Imaging)
• Chronic pancreatitis → calcification on plain film; pseudocysts

7. Spleen (concept 48)

• Location: left hypochondrium, under ribs 9-11, deep to the 9th-11th ribs in the midaxillary line
• Relations: superior = diaphragm; medial = stomach (gastrosplenic ligament), left kidney, splenic flexure; hilum = splenic artery & vein, tail of pancreas
• Ligaments: gastrosplenic (contains short gastric & left gastro-omental vessels), splenorenal (contains splenic vessels & tail of pancreas), phrenicocolic (suspends the splenic flexure)
• Blood supply: splenic artery (from celiac) → branches at the hilum; splenic vein → joins SMV to form the portal vein
• Clinical: splenic rupture (lower ribs fracture, mononucleosis) → left shoulder-tip pain (Kehr's sign — diaphragmatic irritation via phrenic C3-5), hypovolemic shock; accessory spleen in the splenorenal/gastrosplenic ligaments

8. Duodenum

• C-shaped, surrounds the head of the pancreas; 4 parts: 1st (duodenal bulb — peptic ulcers), 2nd (ampulla/papilla, CBD opens), 3rd (crossed by SMA), 4th (duodenojejunal flexure + ligament of Treitz)
• Blood supply: superior pancreaticoduodenal (celiac) & inferior pancreaticoduodenal (SMA) — watershed between foregut & midgut
• Clinical: posterior duodenal ulcer → erosion into the gastroduodenal artery → severe GI bleed; SMA syndrome (3rd part compressed by SMA)

High-Yield Points

• Celiac trunk branches: "LHS" — Left gastric, Hepatic, Splenic (T12/L1)
• Portal triad in hepatoduodenal ligament: "DAV" — common bile Duct, hepatic Artery, portal Vein (duct & artery anterior, vein posterior)
• Omental foramen (Winslow): behind the free edge of the lesser omentum; boundaries: anterior = hepatoduodenal ligament, posterior = IVC, superior = liver (caudate), inferior = 1st part of duodenum
• Posterior gastric ulcer → splenic artery erosion (severe bleed, back pain)
• Duodenal (posterior) ulcer → gastroduodenal artery erosion
• Bleeding lesser-curvature ulcer → left gastric artery
• Gallbladder fundus: tip of the 9th costal cartilage / right midclavicular line; Murphy's sign (inspiratory arrest on palpation)
• Triangle of Calot: cystic duct + common hepatic duct + cystic artery
• CBD → ampulla of Vater → major papilla (2nd part of duodenum) with sphincter of Oddi
• Pancreatic head cancer → painless obstructive jaundice + Courvoisier (palpable gallbladder)
• Spleen: ribs 9-11 midaxillary; Kehr's sign (left shoulder pain) with rupture
• Retroperitoneal "SAD PUCKER" — but stomach/liver/spleen/jejunum/ileum/transverse-sigmoid colon are intraperitoneal
• Bile duct = 2 hepatic + cystic; the "biliary tree" drains into the 2nd part of duodenum

Topic Summary

The supracolic compartment is organized by the peritoneum: the lesser omentum (with the portal triad in its free edge — DAV), the greater omentum, and the omental bursa (communicating via the epiploic foramen). The stomach is supplied by the celiac trunk (left gastric along the lesser curvature — common bleeding ulcer; posterior ulcers may erode the splenic artery). The celiac trunk gives LHS (left gastric, hepatic, splenic). The liver (portal vein 70% + hepatic artery 30%) sits under the diaphragm with the gallbladder beneath; the bile system drains via the CBD & ampulla into the 2nd part of duodenum (sphincter of Oddi); gallstones cause biliary colic/jaundice/pancreatitis. The retroperitoneal pancreas (head in the duodenal C-loop, portal vein behind the neck) — pancreatic head cancer = painless jaundice + Courvoisier. The spleen (ribs 9-11) has gastrosplenic & splenorenal ligaments and is prone to rupture with Kehr's sign.