GASTROINTESTINAL PATHOLOGY (Part 1) — Notes OmpathStudy

GASTROINTESTINAL PATHOLOGY (Part 1) Summary This document provides essential notes on gastrointestinal pathology , focusing on the oral cavity , oesophagus , and stomach . It covers common inflammatory lesions in the oral cavity, such as aphthous ulcers , HSV infections , and candidiasis , alongside proliferative and neoplastic lesions like leukoplakia , erythroplakia , and oral squamous cell carcinoma . Diseases of the salivary glands, including xerostomia , mumps , mucoceles , and bacterial sialadenitis , are also addressed. For the oesophagus, conditions discussed range from congenital anomalies and motility disorders (e.g., achalasia , hiatal hernia ) to inflammatory oesophagitis ( infectious , reflux , eosinophilic ) and the premalignant Barrett oesophagus . The section on the stomach details acute and chronic gastritis ( H. pylori and autoimmune ), peptic ulcer disease , and various gastric tumours, including adenocarcinomas , lymphomas , carcinoid tumours , and gastrointestinal stromal tumours (GISTs) . Key Points Oral Inflammatory Lesions Aphthous ulcers (canker sores) are common, painful, recurrent, and of unknown cause. Herpes Simplex Virus (HSV) infections (cold sores) are reactivations, showing intranuclear inclusions and multinucleated giant cells . Oral Candidiasis (thrush) is a fungal infection, typically appearing as grey-to-white membranes that can be scraped off , distinguishing it from leukoplakia. Oral Proliferative and Neoplastic Lesions Leukoplakia is a white patch that cannot be scraped off and is considered precancerous (5-25% progress to SCC) . Erythroplakia is a red, velvety area with a much greater risk of malignant transformation ( 50%). Oral Squamous Cell Carcinoma (SC C) accounts for 95% of oral cancers, is aggressive, and is linked to " field cancerisation ." It has two main pathways: tobacco/alcohol ( TP53 mutations ) and HPV-related ( HPV-16 , p16 overexpression , better prognosis). Salivary Gland Diseases Xerostomia (dry mouth) is common, often drug-induced or seen in Sjögren syndrome . Mumps is a viral sialadenitis (paramyxovirus), primarily affecting parotids, and can cause pancreatitis or orchitis in adults. A mucocele is the most common inflammatory salivary lesion, resulting from duct blockage/rupture, typically on the lower lip. Oesophageal Motility and Congenital Disorders Oesophageal atresia is a congenital anomaly (blind pouch), often with a tracheoesophageal fistula , posing an aspiration risk. Achalasia involves incomplete LES relaxation, increased LES tone, and aperistalsis, characterized by a " bird's beak " appearance on barium swallow. Oesophageal Inflammation Infectious oesophagitis affects immunocompromised patients: HSV causes " punched-out " ulcers with viral inclusions and giant cells; CMV causes shallower ulcers with nuclear and cytoplasmic inclusions; Candida causes adherent grey-white pseudomembranes. Reflux Oesophagitis (GERD) is the most frequent cause, leading to mucosal injury from gastric acid; histology shows eosinophils , basal zone hyperplasia ( 20%), and elongated papillae. Eosinophilic Oesophagitis is characterized by large numbers of eosinophils in the oesophageal epithelium (especially superficially and away from the GEJ), often resistant to PPIs and associated with atopy . Barrett Oesophagus A complication of chronic GERD, Barrett oesophagus is defined by intestinal metaplasia within the oesophageal squamous mucosa, significantly increasing the risk of oesophageal adenocarcinoma . Gastritis Acute gastritis involves inflammation without mucosal injury (e.g., NSAIDs, alcohol, stress); severe cases can lead to acute haemorrhagic erosive gastropathy . Chronic gastritis is characterized by mucosal inflammation, atrophy, and metaplasia. H. pylori Gastritis: This is the most common chronic gastritis, predominantly affects the antrum , is associated with increased acid secretion, and can lead to PUD , MALT lymphoma , and adenocarcinoma . Autoimmune Gastritis: This affects the body and fundus , is associated with anti-parietal cell and anti-intrinsic factor antibodies , leading to achlorhydria (decreased acid) and hypergastrinemia . It is a major cause of pernicious anaemia and increases gastric cancer risk. Peptic Ulcer Disease (PUD) Peptic Ulcer Disease (PU D) is most often associated with H. pylori infection or NSAID use , commonly found in the gastric antrum and first portion of the duodenum ( duodenal ulcers are 4x more common ). It is characterized by " punched-out " defects, pain relieved by alkali or food, and complications including haemorrhage and perforation. Zollinger-Ellison syndrome causes multiple, severe ulcers due to excessive gastrin. Gastric Tumours Gastric Adenocarcinoma: This has highly variable incidence worldwide; H. pylori is the most common etiologic agent. It is classified into intestinal pattern (bulky, ulcerated) and diffuse pattern ( signet ring cells , linitis plastica ). Primary Gastric Lymphoma (MALT): Often induced