GI Pathology · Study Notes

🔬 Esophagus

Tracheoesophageal fistula — congenital connection between esophagus & trachea
Often with esophageal atresia; presents with aspiration at birth
Adults: secondary to malignancy, trauma, or iatrogenic
Esophageal webs — thin mucosal protrusions → dysphagia
Plummer‑Vinson: webs + iron‑deficiency anemia + ↑ SCC risk (middle‑aged women)
Schatzki ring — web‑like narrowing at GE junction
Achalasia — LES fails to relax; progressive dysphagia
Dilated esophagus proximal to LES; "bird‑beak" on barium
Micro: loss of myenteric ganglion cells
Tx: balloon dilation or myotomy; ↑ risk of SCC
Chagas disease (S. America) can cause achalasia (Trypanosoma cruzi)
Mallory‑Weiss tear — linear laceration at GE junction from severe vomiting
Associated with alcohol abuse; can cause hematemesis
Esophageal varices — dilated submucosal veins (lower ⅓) due to portal HTN
Most common cause: cirrhosis; risk of massive hemorrhage
Tx: band ligation, sclerotherapy, balloon tamponade

          pearl Barrett esophagus: metaplasia (squamous → columnar) from GERD; ↑ adenocarcinoma risk

        

Pyloric stenosis — congenital hypertrophy of pyloric sphincter
Male > female; associated with Turner/Edwards
Projectile vomiting, palpable "olive" mass; surgical tx
Congenital diaphragmatic hernia — stomach herniates into thorax
Left‑sided; associated with intestinal malrotation, lung hypoplasia
Menetrier disease — hyperplasia of surface mucous cells; enlarged rugae
Decreased acid, protein‑losing enteropathy, ↑ gastric cancer risk
Acute hemorrhagic gastritis — mucosal erosion from barrier breakdown
Causes: NSAIDs, alcohol, stress, uremia, burns
Epigastric pain, hematemesis, melena
Stress ulcers — multiple, superficial; ICU, burns, ↑ ICP (Cushing)
Chronic gastritis – fundic (autoimmune)
Anti‑parietal cell / anti‑intrinsic factor → loss of parietal cells
↓ acid, ↑ gastrin, pernicious anemia (B12 deficiency)
↑ risk gastric carcinoma; loss of rugal folds
Chronic gastritis – antral (H. pylori)
Most common in US; curved gram‑negative rods, urease‑positive
Associated with peptic ulcer, gastric MALT lymphoma, intestinal‑type adenocarcinoma
Micro: organisms in mucous layer, lymphoid follicles, intestinal metaplasia
Peptic ulcer disease — distal stomach / proximal duodenum
Duodenal: ~100% H. pylori, ↑ acid, blood group O, MEN1, ZES
Gastric: ~75% H. pylori, lesser curvature antrum, <3 cm, punched out
Complications: hemorrhage, perforation (free air), penetration, obstruction

Volvulus — bowel twist on mesentery → obstruction & infarction
Sigmoid colon or small bowel; associated with malrotation
Intussusception — telescoping of bowel (proximal into distal)
Children: vomiting, abdominal pain, bloody stools, sausage‑shaped mass
Adults: often due to tumor
Hirschsprung disease — congenital absence of ganglion cells (rectum + sigmoid)
Males > females; associated with Down syndrome
Delayed meconium, constipation, abdominal distention; narrow segment + megacolon
Biopsy: absent ganglia in Auerbach & Meissner plexuses
Celiac sprue — gluten hypersensitivity (gliadin) → villous atrophy
HLA‑DQ2/DQ8; diarrhea, steatorrhea, weight loss, dermatitis herpetiformis
↑ risk GI malignancy; Tx: gluten‑free diet
Whipple disease — Tropheryma whipplei (PAS‑positive macrophages)
Malabsorption, arthralgias, CNS; Caucasian males 30–50; Tx: antibiotics
Pseudomembranous colitis — C. difficile (often after antibiotics)
Yellow‑tan pseudomembranes; diarrhea, fever, cramps
Tx: vancomycin or metronidazole
Appendicitis — obstruction by fecalith → periumbilical pain → RLQ
Fever, nausea, elevated WBC; rupture → peritonitis
Ischemic bowel — atherosclerosis, thromboembolism, shock
Watershed areas (splenic flexure); abdominal pain, bloody diarrhea
Hemorrhoids — dilated anal veins; constipation, pregnancy, cirrhosis
Angiodysplasia — vascular malformation; >55 years, recurrent bleeding

          pearl Meckel diverticulum: 2% population, 2 ft from ileocecal, 2 cm, ≤2 years; may have ectopic gastric mucosa

        

Feature	Crohn disease	Ulcerative colitis
Most common site	Terminal ileum	Rectum
Distribution	Discontinuous ("skip")	Continuous, rectum → colon
Gross	Cobblestone, fissures, creeping fat	Pseudopolyps, extensive ulceration
Micro	Non‑caseating granulomas, transmural	Crypt abscesses, mucosa/submucosa
Complications	Strictures, fistulas, obstruction	Toxic megacolon
Extra‑intestinal	Arthritis, PSC, uveitis, erythema nodosum	Same (PSC, arthritis, etc.)

Gastric adenocarcinoma — Japan > US; risk: H. pylori, smoked foods, nitrosamines
Intestinal type: gland‑forming; diffuse type: signet‑ring, linitis plastica
Metastasis: Virchow node, Krukenberg tumor (ovary)
Gastric MALT lymphoma — associated with H. pylori; marginal zone B‑cell
Colonic adenocarcinoma — 3rd most common cancer; risk: low‑fiber, red meat, polyps, IBD
APC mutation → Wnt activation; mismatch repair → microsatellite instability
Right‑sided: polypoid, bleeding, iron deficiency; Left‑sided: napkin‑ring, obstruction
TNM staging; CEA for recurrence monitoring
Familial adenomatous polyposis (FAP) — APC 5q21; >100 polyps; 100% cancer by 40
Gardner: + osteomas, fibromas; Turcot: + CNS tumors
HNPCC (Lynch) — mismatch repair; ↑ colon, endometrial, ovarian cancer
Peutz‑Jeghers — hamartomatous polyps, oral pigmentation; ↑ multiple cancers
Carcinoid — neuroendocrine, serotonin; appendix & ileum; ↑ 5‑HIAA
GIST — KIT mutation; sarcoma; tyrosine‑kinase inhibitor

Anal skin tags — fibroepithelial polyps from inflammation or injury
Perianal Crohn — fissures, fistulas, abscesses, stenosis
Hemorrhoids — above dentate: columnar; below: anoderm/skin; bright red bleeding
Condyloma acuminatum — HPV‑induced; most common anal tumor
Anal intraepithelial neoplasia (AIN) — precursor to SCC; HPV‑related
Screening: high‑risk groups; anoscopy + biopsy