ABSITE 2026 Quick Hits: Foregut, HPB, and Pancreas Review

Esophageal Anatomy and Pathology

• 💡 The esophagus has a squamous epithelium inner layer, inner circular and outer longitudinal muscle layers, and lacks a serosa.
• 🧠 The upper third is striated muscle, the lower two-thirds is smooth muscle, with the LES at 40 cm from incisors.
• ⚠️ Anatomical narrowings where foreign bodies can lodge include the upper esophageal sphincter (cricopharyngeus), left main stem bronchus, aortic arch crossing, and diaphragmatic hiatus.
• 🏥 Surgical access: left-sided incision for the neck, right side for the upper two-thirds of the chest, and left side for the lower one-third.
• 🎯 Zenker's diverticulum is a false diverticulum between the cricopharyngeus and pharyngeal constrictor muscles, treated with cricopharyngeal myotomy or resection.
• 📈 In the US, adenocarcinoma is the most common esophageal cancer (associated with obesity/GERD); worldwide, squamous cell carcinoma is most common.

Stomach Anatomy and Gastric Bypass

• 🩸 Stomach blood supply includes the left gastric (celiac trunk), right gastric (common hepatic), left gastroepiploic and short gastric (splenic artery), and right gastroepiploic (GDA).
• 🧪 Parietal cells secrete hydrochloric acid, activated by acetylcholine, histamine, and gastrin.
• 💊 GIST is medically treated with imatinib, a tyrosine kinase inhibitor.
• ⚠️ The first sign of a leak post-bypass can be tachycardia.
• 📉 Roux-en-Y gastric bypass can lead to B12 deficiency (lack of intrinsic factor/acid) and iron deficiency (absorbed in the duodenum).

Hepatobiliary and Pancreatic System

• 🗺️ Common hepatic artery variants: right hepatic from SMA (most common), left hepatic from left gastric.
• 📍 Cantlie's line separates liver lobes (gallbladder fossa to IVC); the falciform ligament separates medial and lateral segments of the left lobe.
• 🖐️ Liver segments (using a fist analogy): Segment 1 (caudate), 2 (proximal index), 3 (middle index), 4A (proximal middle), 4B (middle middle), 5 (ring middle), 6 (little middle), 7 (little proximal), 8 (ring proximal).
• ⚡ Hepatocytes in acinar zone 3 are most sensitive to ischemia.
• 📊 Gilbert's and Crigler-Najjar syndromes involve conjugation issues (high indirect bilirubin); Rotor and Dubin-Johnson syndromes involve excretion issues (high direct bilirubin).
• 📈 PT/INR is the best indicator of synthetic function in cirrhosis due to Factor VII's short half-life.
• ⚖️ Normal portal vein pressure is 5-10 mmHg; hepatic venous pressure gradient (HVPG) is normal at 1-5 mmHg.
• 🚺 Hepatic adenomas are common in reproductive-age women on OCPs or men on anabolic steroids; risk of hemorrhage and malignant transformation exists.
• 🔬 CT findings for adenomas: early arterial enhancement, isoattenuation in portal/delayed phases.
• 🚺 Treatment for adenomas: conservative for females <5cm and asymptomatic (stop OCPs); resection for males or females >5cm.
• 🦠 Most common malignant liver tumor is metastasis (20:1 ratio over primary).
• 🚰 Morphine contracts the sphincter of Oddi; glucagon relaxes it.
• 📏 Normal common bile duct size: <0.8 cm (under 65), <1.1 cm (over 65), <1 cm post-cholecystectomy.
• ⬆️ Bile excretion increases with cholecystokinin, secretin, and vagal input; decreases with somatostatin, VIP, and sympathetic input.
• 🦠 Air in the biliary system can be caused by ERCP, cholangitis, or a fistula to the enteric tract.
• 🎗️ Choledochal cysts: Type 1 (most common, cystic dilation of CBD, treated with resection/hepaticojejunostomy), Type 2 (diverticular dilation), Type 3 (choledochocele), Type 4A (intra- and extrahepatic dilation), Type 4B (extrahepatic dilation), Type 5 (Caroli's disease, intrahepatic dilation).
• 🔬 Primary biliary cirrhosis is associated with antimitochondrial antibodies and may require transplant.
• 🤢 Most common bugs in cholangitis: E. coli, Klebsiella.
• 🚨 Charcot's triad: RUQ pain, fever, jaundice; Reynolds' pentad adds altered mental status and shock.
• 🔪 Treatment for cholangitis: urgent biliary decompression (ERCP, PTC).
• 🔴 Imaging findings: Hemangioma (peripheral to central enhancement), Focal Nodular Hyperplasia (central scar), Hepatocellular Carcinoma (heterogeneous, poorly circumscribed, early arterial enhancement, washout, rim enhancement).
• 🪨 Gallbladder polyps >10mm are concerning.
• 🧪 Biliary dyskinesia diagnosed with HIDA scan (ejection fraction <35% 20 min post-CCK), with absence of stones/cholecystitis.

Pancreatic Function and Anatomy

• 🧬 Pancreatic endocrine cells: Alpha (glucagon), Beta (insulin), Delta (somatostatin).
• 💥 Pancreatic enzymes are activated by enterokinase from the duodenum converting trypsinogen to trypsin.
• 💧 Pancreatic accessory duct is the duct of Santorini; the major duct is the duct of Wirsung.
• 🍩 Annular pancreas involves the second portion of the duodenum surrounded by pancreatic tissue, treated with duodenostomy/duodenoduodenostomy.
• 🫀 Grey Turner's sign (flank ecchymosis) and Cullen's sign (umbilical ecchymosis) are caused by hemorrhagic pancreatitis.