Gastrointestinal System on Step 1: Liver, Bowel, Pancreas and Infant Disorders

Scope and time budget

Twenty-two questions is about one 30-minute block. The system has 16 subtopics, with liver disease as the densest part. Share a week with cardiovascular in a 12-week plan, or give it a full week in a 16-week plan. The GI row connects to the multisystem row through microbiology (diarrhea, hepatitis viruses), biochemistry (bilirubin, iron overload, copper) and pharmacology (PPIs, antiemetics, laxatives).

What is tested

• Upper GI. Esophageal disorders (GERD, Barrett esophagus, achalasia, esophageal cancer), gastric physiology, peptic ulcer disease and gastric cancer.
• Intestine. Small bowel malabsorption (celiac disease, lactose intolerance, Whipple disease), inflammatory bowel disease, colorectal polyps, hereditary syndromes and colorectal cancer, and infectious diarrhea.
• Liver, biliary tract and pancreas. Viral and autoimmune hepatitis, cirrhosis, portal hypertension and hepatic encephalopathy, biliary disease (gallstones, cholecystitis, cholangitis), pancreatitis and pancreatic cancer, alcohol-related and metabolic liver disease, hemochromatosis and Wilson disease.
• Physiology. GI hormones, motility and secretion, and bilirubin metabolism with hereditary hyperbilirubinemias.
• Anatomy and congenital disorders. Abdominal anatomy, hernias, mesenteric ischemia, pyloric stenosis, Hirschsprung disease, intussusception and malrotation.
• Pharmacology. Proton pump inhibitors, antiemetics and laxatives.

Anchor facts and US conventions

These are standard textbook points to verify against your reference.

• Bilirubin. Unconjugated hyperbilirubinemia (raised indirect bilirubin) arises from hemolysis or impaired conjugation. Conjugated hyperbilirubinemia (raised direct bilirubin) points to cholestasis or hepatocellular injury. Hemolysis also shows low haptoglobin and raised LDH, which links to the blood and immune page.
• Hepatitis serology. Learn the pattern of surface antigen, core antibodies and surface antibody for acute infection, chronic infection and immunity after vaccination. Questions give the serology panel and ask for the stage.
• Celiac disease. Associated with HLA-DQ2 and DQ8, with villous atrophy and positive tissue transglutaminase antibodies. It also associates with dermatitis herpetiformis.
• Inflammatory bowel disease. Crohn disease is transmural, can affect any part of the tract, and has skip lesions and granulomas. Ulcerative colitis is mucosal and continuous from the rectum.
• Gallbladder and pancreas. Gallstones and alcohol are the leading causes of acute pancreatitis. Cholangitis presents with fever, jaundice and right upper quadrant pain.
• Iron and copper. Hemochromatosis (iron overload) and Wilson disease (copper accumulation) are classic liver-plus-another-organ diseases.
• Congenital disorders. Pyloric stenosis presents in young infants with projectile non-bilious vomiting. Hirschsprung disease reflects absent enteric ganglion cells in the distal bowel.
• US conventions. Liver enzymes in units per liter, bilirubin in mg/dL, albumin in g/dL, and US generic names such as omeprazole and ondansetron.

Three typical traps

1. Mixing the cholestatic and hepatocellular patterns. Alkaline phosphatase and bilirubin dominate in biliary obstruction, while transaminases dominate in hepatocellular injury. Decide the pattern from the stem before you choose a diagnosis.
2. Confusing Crohn disease with ulcerative colitis. The stems often mix features (smoking, extraintestinal signs, endoscopy and pathology, imaging). Use a two-column table with every feature on both sides.
3. Treating the GI hormones as a list. Questions ask what raises or lowers acid secretion, motility or bile release in a specific situation. Learn each hormone's trigger, site of release and effect, and then reason about the scenario.

How to revise this system

• Draw the tract. Label the epithelium, the common cancers, the common infections and the typical congenital lesion at each segment.
• Memorize the liver panel patterns. Make a small table of lab patterns for hepatocellular injury, cholestasis, hemolysis and Gilbert-type conjugation defects.
• Table the hepatitis viruses. Transmission, chronicity, serology and treatment.
• Learn the drugs with their toxicities. PPIs, H2 blockers, antiemetics and laxatives each have a signature adverse effect that questions like to ask.
• Mix with microbiology and biochemistry. Infectious diarrhea and metabolic liver disease are shared with the multisystem row.

The study plan guide shows how to place this system.

What the questions look like

Items usually give a history, abdominal examination findings, a lab panel (liver enzymes, bilirubin fractions, serology) and sometimes an imaging or pathology description. The final question asks for the diagnosis, the underlying mechanism, the next best step or the adverse effect of a drug. Our original practice bank follows the same format with conventional units and five options, and it does not copy official or recalled items. The Step 1 hub lists every system and weight, and the high-yield topics guide has the drug and organism tables you will reuse here.

Two comparison tables worth building

First, build a table of the four main causes of jaundice by pattern: hemolytic, hepatocellular, cholestatic and hereditary conjugation defects. For each, write the bilirubin fraction that rises, the enzyme pattern, the urine findings and a typical cause. Second, build a table of the esophageal and gastric conditions by symptom and by risk of cancer: reflux disease and Barrett esophagus, achalasia, peptic ulcer disease and gastric cancer. Both tables can be rebuilt from memory in ten minutes, and that is the test of whether they work.

Finally, remember the infant conditions. Pyloric stenosis, malrotation, intussusception and Hirschsprung disease each have an age window, a classic presentation and a characteristic imaging or biopsy clue. A one-page card for the four of them is enough to answer most of the congenital items in this row.

Add one more page for the hereditary colorectal cancer syndromes and the polyp types, because the link between a genetic syndrome and a cancer risk is a reliable question pattern in this row and in the multisystem row.