Lower GI Pathology

Question 1

• Hiatal/sliding: cardia of stomach is diplaced into the esophagus
• Paraesophageal: cardia of stomach penetrates weakness in diaphragm into peritoneal space
• intestinal hernia: displacment of segment of bowel into peritoneal space

Complications:

• Reflux
• Impaired venous drainage
• incarceration, strangulation, Infarction

Answer 1

Hernia

Question 2

• segment of intestine telescoping into distal segment
• may lead to obstruction, compression of vessels, infarction
• commonly caused by tumor

Answer 2

Intussusception

Question 3

• Complete twisting of loop of bowel
• results in luminal and vascular compromise
• commonly in sigmoid colon (elderly) and cecum (young adults)

Answer 3

Volvulus

Question 4

• Congenital anganglionic megacolon
• DX requires absence of ganglionic cells within affected region
• defective relaxation and peristalsis of rectum and distal sigmoid colon
• associated with Down syndrome
• Myelnteric/Auerbach plexus: regulates motlity
• Submucosal (Meissner) plexus: regulates blood flow, secretions and absorption

Answer 4

Hirschsprung’s Disease

Question 5

• outpouching of all 3 layers of the bowel wall (true diverticulum)

Rule of 2’s:

• presents during 1st 2 years of life
• seen in 2% of population
• within 2 feet of ileocecal valve
• 2 inches long
• 2x more common in males

Answer 5

Meckel Diverticulum

Question 6

• Pseudodiverticulum: involve only muscosa, submucosa and muscular is propria (not transmural)
• Acquired: assoc with constipation, straining and low-fiber diet
• arise where vasa recta traverse the muscular is propria
• Generally multiple
• most comon in the sigmoid colon

Answer 6

Colonic Diverticula / Diverticulosis

Question 7

• inflammation of the diverticulum due to obstruction of fecal material
• presents with appendicitis-like symptoms in the LLQ (location of sigmoid colon)
• prone to perforation

Answer 7

Diverticulitis

Question 8

• Mucosal and submucosal vascular malformations (acquired)
• usually arises in the cecum and right colon due to high wall tension
• Ruptures present as hematochezia (passing blood in stool)
• don’t biopsy, b/c may bleed

Answer 8

Angiodysplasia

Question 9

• Distended blood vessels below the anorectal line

Answer 9

External Hemorrhoids

Question 10

• Distended blood vessels above the anorectal line, within the distal rectum

Answer 10

Internal Hemorrhoids

Question 11

Mucosal: due to acute/chronic hypoperfusion
- e.g., shock, cardiac failure, cocaine use (vasoconstriction), dehydration

Transmural: due to acute vascular obstruction
- Atherosclerosis, aortic aneurysm, embolization

2 phases:

• initial hypoxic injury
• Reperfusion injury (free radical damage)

Complication:

• stricture
• postpandrial pain and weight loss
• bloody diarrhea

Answer 11

Ischemic Bowel Disease

Question 12

• intestinal segments at end of their arterial supply
• splenic flexure
• sigmoid colon and rectum
• right colon

Answer 12

Watershed zones

Question 13

• inflammation due to obstruction of the appendix by fecalith (fecal material)

Acute inflammation: neutrophilic infiltrate extending into muscularis propria

• Periumbilical pain, migrating to RLQ (McBurney point)
• repture results in peritonitis (rebound tenderness)

Answer 13

Appendicitis

Question 14

• autsomal recessive deficiency of apolipoprotein B-48 (make chylomicrons) and B-100 (make VLDL and LDL)
• results in malabsorption

Answer 14

Abetalipoproteinemia

Question 15

Systemic tissue damage, characterized by macrophages (Pas+) loaded with Tropheryma whippelii

• involves the small bowel lamina propria (foamy macrophages in the lamina propria)
• causes compression of lacteals, resulting in fat malabsorption and steatorrhea

Answer 15

Whipple Disease

Question 16

• immune-mediated damage of small bowel villi (flattening of villi) due to gluten exposure
• Associated with HLA-DQ2 and HLA-DQ8

Presentation:

• flattening of villi; hyperplasia of crypts
• Lymphoplasmacytic expansion of the lamina propria
• abdominal distension, diarrhea, failure to thrive
• Dermatitis herpetiformis

Dx: IgA antibodies; tTG; gliadin

Answer 16

Celiac Disease

Question 17

• pathogenic component of gluten
• Once absorbed, is deamindated by tissue transglutaminase (tTG) and is presented to MHC class II cells to Helper T cells

Answer 17

Gliadin

Question 18

• diarrhea w/ neutrophils (+- blood) due to mucosal necrosis from C.difficile infection
• overgrowth can occur with use of antibiotics

Answer 18

Pseudomembranous Colitis

Question 19

• Chronic relapsing inflammation of the bowel

- diagnosis of excluding: need to rule out infection

Answer 19

Inflammatory Bowel Disease

Question 20

• Mucosal & submucosal ulcers
• begins in rectum and extends proximally
• continuous ascending spread

Symptoms:

• Bloody diarrhea
• LLQ pain (rectum)

Histology:
- crypt abscesses with neutrophils

Gross: pseudopolyps; loss of haustra; “lead pipe” sign

Complications:

• Toxic megacolon
• Carcinoma

Association:

• primary sclerosing cholangitis
• p-ANCA positive

Smoking is protective

Answer 20

Ulcerative Colitis

Question 21

• Full-thickness inflammation with knife-like fissures
• anywhere from mouth to anus with skip lesions; terminal ileum is most common; rectum is least common
• Gross appearance: Cobblestone pattern with creeping fat and strictures; “string sign” on imaging

Main symptom: RLQ pain with non-bloody diarrhea

Histology:
- lymphoid aggregates with granulomas (non-caseating)

Complications: malabsorption; calcium oxalate nephrolithiasis; fistula formation; carcinoma

Associations: ankylosing spondylitis, sacroiliitis, migratory polyarthritis, erythema nodosum, uveitis

Smoking increases risk

Answer 21

Crohn Disease

Question 22

• raised protrusions of colonic mucosa, due to hyperplasia of glands
• classically show a serrated appearance on microscopy
• Benign, with no malignant potential

Answer 22

Hyperplastic polyp

Question 23

• autosomal dominant disorder
• Hamartomatous (benign) polyps throughout GI tract, with mucocutaneous hyperpigmentation on lips, oral mucosa and genital skin
• assoc with increased risk of colorectal, breast and gynecologic cancer

Answer 23

Peutz-Jeghers Syndrome

Question 24

• sporadic hamartomatous (benign) polyp that arises in children
• characterized by multiple juvenile polyps in stomach and colon
• increased risk of progression to carcinoma

Answer 24

Juvenile Polyposis

Question 25

• Autosomal Dominant disorder
• Inherited APC mutation, increasing the propensity to deelop adenmatous polyps throughout the colon and rectum
• requires prophylactic colonectomy; otherwise 100% develop colorectal carcinoma by age 30

Answer 25

Familial Adenomatous Polyposis

Question 26

• FAP with fibromatosis, osteomas and dental abnormalities

Fibromatosis: non-neoplastic proliferation of fibroblasts

Osteoma: benign tumor of bone that usually arises in the skull

Answer 26

Gardner Syndrome

Question 27

• FAP with CNS tumors (meduloblastoma and glial tumors)

Answer 27

Turcot Syndrome

Question 28

• due to inherited mutations in DNA mismatch repair enzymes
• increased risk for colorectal, ovarian and endometrial carcinoma
• Colorectal carcinoma arises de novo (via microsatellite instability); relatively young age, usually right-sided

Answer 28

Hereditary Nonpolyposis colorectal carcinoma (HNPCC)

Question 29

• APC mutations increase risk for formation of polyp
• K-ras mutation leads to formation of polyp
• p53 mutation and increased expression of Cox: progression to carcinoma

Answer 29

Adenoma-carcinoma sequence

Question 30

• annular growth, “napkin-ring” lesion

- results in obstruction; blood streaked stool

Answer 30

Left-sided carcinoma

Question 31

• Polypoid, raised lesion growth pattern

- presents with iron defciency anemia and vague pain

Answer 31

Right-sided carcinoma

Question 32

• a neuroendocrine tumor

Carcinoid syndrome: serotonin production

Zollinger-Ellison syndrome: Gastrin producing tumor, increasing risk for PUD

Answer 32

Carcinoid tumor