1. Presenting Symptom: Abdominal Pain
Differentials:
RUQ Pain
Cholecystitis → RUQ US
Choledocholithiasis → RUQ US ± MRCP
Cholangitis → RUQ US + Blood Cultures
Hepatitis → LFTs, Viral Hep Panel
Epigastric Pain
Pancreatitis → Lipase, Abdominal CT
Peptic Ulcer Disease → H. pylori Testing, EGD
GERD → Trial of PPI, ± EGD if alarm symptoms
RLQ Pain
Appendicitis → CT Abdomen (adults), US (kids)
Crohn’s Disease → Colonoscopy ± Biopsy
Ovarian Torsion (females) → Pelvic US with Doppler
LLQ Pain
Diverticulitis → CT Abdomen/Pelvis with contrast
Sigmoid Volvulus → Abdominal X-ray (coffee-bean sign), CT
Diffuse Pain
Bowel Obstruction → Upright Abdomen X-ray
Mesenteric Ischemia → CTA Abdomen
Gastroenteritis → Stool Studies (if severe)
2. Presenting Symptom: Diarrhea
Differentials:
Acute Watery Diarrhea
Viral Gastroenteritis → Clinical
Food Poisoning (E. coli, Salmonella, Shigella) → Stool Cultures
Bloody Diarrhea
Dysentery (Shigella, EHEC) → Stool Culture, Shiga Toxin Assay
IBD (Ulcerative Colitis, Crohn’s) → Colonoscopy + Biopsy
Chronic Diarrhea
Celiac Disease → tTG-IgA antibodies, Duodenal Biopsy
IBS → Diagnosis of exclusion
Microscopic Colitis → Colonoscopy + Random Biopsies
3. Presenting Symptom: GI Bleed
Differentials:
Upper GI Bleed (Melena, Hematemesis)
Peptic Ulcer Disease → EGD
Esophageal Varices → EGD
Mallory-Weiss Tear → EGD
Lower GI Bleed (Hematochezia)
Diverticulosis → Colonoscopy
Angiodysplasia → Colonoscopy
Colorectal Cancer → Colonoscopy + Biopsy
4. Presenting Symptom: Jaundice
Differentials:
Pre-hepatic
Hemolysis (e.g., G6PD Deficiency) → CBC, Reticulocyte count, LDH, Haptoglobin
Hepatic
Viral Hepatitis → Hepatitis Panel
Alcoholic Hepatitis → AST>ALT (2:1), Elevated GGT
Drug-induced liver injury → Medication history + LFTs
Post-hepatic (Obstructive)
Gallstones → RUQ US
Malignancy (e.g., pancreatic cancer) → CT Abdomen
5. Presenting Symptom: Nausea/Vomiting
Differentials:
Gastroenteritis → Clinical
SBO (Small Bowel Obstruction) → Abdominal X-ray
Gastric Outlet Obstruction → Abdominal CT, EGD
Increased Intracranial Pressure → Head CT/MRI (if neurologic signs)
📝 QUICK STRATEGY TIPS:
Always start with RUQ Ultrasound for biliary issues.
CT Abdomen is a key test for acute abdominal pain when diagnosis unclear.
Endoscopy (EGD or Colonoscopy) is confirmatory for bleeds and chronic diarrhea.
Labs (LFTs, Lipase, CBC) are first line when systemic signs are present (fever, jaundice).
