Clinical Chemical Pathology Crash Course — OmpathStudy

SECTION 4: GI & Pancreatic Disorders, Liver Disease, and Body Fluid Cytology (Pages 154–223) --- 1. Gastrointestinal (GI) Disorders Definition: Conditions affecting the digestive tract — oesophagus, stomach, small intestine, colon, rectum — disrupting digestion, absorption, and waste elimination. Common symptoms: Abdominal pain, nausea/vomiting, diarrhoea or constipation, bloating, unexplained weight loss, appetite changes. Categories of GI Disorders Inflammatory: Gastritis — stomach lining inflammation; causes: H. pylori, NSAIDs, alcohol, autoimmune Crohn's Disease — transmural inflammation, any part of GI tract (commonly terminal ileum); can cause strictures and fistulas Ulcerative Colitis — continuous mucosal inflammation of colon/rectum only Peptic Ulcer Disease — gastric or duodenal ulcers; caused by H. pylori or NSAIDs Functional (no structural cause): IBS — abdominal pain + altered bowel habits (IBS-D, IBS-C, IBS-M) Functional Dyspepsia — chronic upper abdominal pain, bloating, early satiety; no organic pathology Structural: Diverticulitis — inflamed colonic pouches; pain, fever, altered bowel habit Hiatal Hernia — stomach herniation through diaphragm → GERD, heartburn Achalasia — failure of lower oesophageal sphincter to relax → dysphagia, regurgitation Neoplastic: Colorectal Cancer — altered bowel habit, rectal bleeding, pain Pancreatic Cancer — jaundice, weight loss, back pain, new-onset diabetes Oesophageal Cancer — dysphagia, weight loss, chest pain; subtypes: squamous cell and adenocarcinoma Metabolic/Endocrine: Coeliac Disease — autoimmune reaction to gluten → small intestinal damage → malabsorption Pancreatic Insufficiency — inadequate digestive enzymes → malabsorption, steatorrhoea Motility: Gastroparesis — delayed gastric emptying; nausea, vomiting, early satiety; common in diabetics Oesophageal Spasm — abnormal contractions → chest pain, dysphagia Obstructive: Bowel Obstruction — adhesions, tumours, hernias → severe pain, vomiting, inability to pass stool/gas Gallstones — obstruct bile ducts → pain, jaundice, cholecystitis --- 2. Laboratory Evaluation of GI Disorders Test Purpose Key Indicators --- --- --- CBC Overall health, detect anaemia/infection Low Hb → GI bleeding or malabsorption; elevated WBC → infection BMP/CMP Electrolytes, kidney function, metabolic status Electrolyte losses from diarrhoea/vomiting; glucose for pancreatic function LFTs Liver/biliary function ALT/AST → hepatitis; ALP/GGT → bile duct obstruction; bilirubin → jaundice Serum Amylase & Lipase Pancreatitis diagnosis Lipase more specific and stays elevated longer Fecal Occult Blood Test (FOBT) Screen for GI bleeding Hidden blood → colorectal cancer or ulcer Fecal Immunochemical Test (FIT) Colorectal cancer screening Detects human haemoglobin in stool Stool Cultures Infectious diarrhoea Identify bacteria, viruses, parasites Fecal Fat Test Malabsorption Steatorrhoea → pancreatic insufficiency Anti-tTG IgA Coeliac disease Elevated → coeliac H. pylori tests Peptic ulcer/gastritis Serology, urea breath test, stool antigen Lactose Tolerance Test Lactose intolerance Low post-ingestion glucose rise Hydrogen Breath Test Carbohydrate malabsorption Elevated H₂ → malabsorption CEA, CA 19-9 GI cancer monitoring CEA → colorectal; CA 19-9 → pancreatic Gastrin Levels Zollinger-Ellison syndrome Elevated → gastrin-secreting tumour --- 3. Pancreatic Disorders The pancreas has two roles: Exocrine — secretes digestive enzymes (amylase, lipase, trypsin) into the duodenum Endocrine — secretes insulin and glucagon into the blood Types of Pancreatic Disorders Inflammatory: Acute Pancreatitis — sudden inflammation; causes: gallstones (most common), alcohol, drugs, trauma. Features: severe epigastric pain radiating to the back, raised amylase/lipase, nausea, fever. Complications: necrosis, abscess, systemic sepsis Chronic Pancreatitis — progressive permanent damage; cause: chronic alcohol use or genetic. Features: persistent pain, steatorrhoea, weight loss, diabetes. Complications: exocrine insufficiency, pseudocysts Neoplastic: Pancreatic Adenocarcinoma — most common; often presents late (jaundice, weight loss, back pain, new-onset diabetes). Poor prognosis Pancreatic Neuroendocrine Tumours (PNETs) — less common; may be functional (e.g., insulinoma, gastrinoma) Functional: Pancreatic Insufficiency — inadequate enzyme production → malabsorption, steatorrhoea, weight loss; caused by chronic pancreatitis, cystic fibrosis, or pancreatic cancer Metabolic: Diabetes Mellitus Type 1 — autoimmune destruction of beta cells → no insulin Diabetes Mellitus Type 2 — insulin resistance + relative deficiency Structural: Pancreatic Cysts — simple, pseudocysts (post-pancreatitis), cystic neoplasms; may be asymptomatic or cause pain Pseudocysts — fluid collections after pancreatitis, surrounded by fibrous wall; require drainage if symptomatic Genetic: Cystic Fibrosis — CFTR gene mutation → thick secretions → pancreatic insufficiency + recurrent lung infections;