Small Intestine and Colon Pathology #2 - Nelson

Question 1

What is the most common cause of acute diarrhea?

Answer 1

Most common cause of acute diarrhea is infectious diarrhea.

Question 2

What are the key clinical and pathologic findings of C. difficile associated colitis?

Answer 2

• Clinical:
  
  • Symptoms can occur several weeks after discontinuation of antibiotic therapy.
  • mild diarrhea to fully developed pseudomembranous colitis to fulminant disease with perforation or toxic megacolon.
• Pathological:
  
  • apoptosis of the colonic epithelium
  • necrotic crypts with mucin, fibrin and neutrophils, with production of a pseudomembrane

Question 3

What is the key diagnostic test for C. difficile associated colitis?

Answer 3

Diagnosis is established by detecting toxin producing strains of C. difficile, typically with a stool PCR assay.

Question 4

What are the key pathologic findings of ulcerative colitis?

Answer 4

• Inflammatory changes involve the mucosa and at most the superficial submucosa
  
  • no transmural involvement
  • lymphoplasmacytic inflammation
  • Some crypts are branched (architectural distortion), indicating previous injury and regeneration
  • neutrophils perforate the crypt epithelium (neutrophilic cryptits) and form a crypt abscess
• disease is limited to the colon and rectum in a continuous fashion
  
  • rectum is always involved, so this is a “left sided disease of the colon” → involves the rectum and can involve the whole colon

Question 5

What are the key pathologic findings of Crohn’s disease?

Answer 5

• Inflammatory changes are typically transmural
  
  • can involve any area of the GI tract
  • usually in a non-continuous fashion (skip lesions)
• As Crohn’s disease typically involves the ileum, it is sometimes known as regional enteritis.
  
  • deep ulcers → cobblestone appearance
  • fat wrapping

Question 6

Define and describe diversion colitis.

Answer 6

• Colitis developing in a blind distal segment of the colon which is excluded from the fecal stream, following surgery with formation of a temporary or permanent diverting ostomy
  
  • due to deficiency of short-chain fatty acids
• Results in mucosal erythema, friability, and nodularity (due to mucosal lymphoid hyperplasia) with aphthous uclers

Question 7

Define and describe radiation enterocolitis.

Answer 7

• Occurs when the GI tract is irradiated.
  
  • Epithelial damage occurs acutely
  • chronic injury is often ischemic, resulting from vascular injury with occlusion of blood vessels
  • Patients can develop ulcers, strictures, fistulas, and serosal adhesions.
• Mucosal changes ⇒ patchy erythema, secondary to mucosal telangiectasias.
• Blood vessels show hyalinization and thickening of the walls, with reduced luminal diameter.
• Atypical pleomorphic “radiation fibroblasts” can be seen.

Question 8

Define and describe neonatal necrotizing enterocolitis.

Answer 8

• Can develop in the first week of life in premature infants.
• Both the small and large bowel exhibit necrosis which can become transmural.
• Bacterial overgrowth can produce gas in the wall of the intestine, seen as air bubbles (pneumatosis intestinalis).
• Etiology is probably multifactorial
  
  • resulting in mucosal injury in premature infants that can have impaired GI defenses to mucosal injury

Question 9

What are the two types of microscopic colitis?

Answer 9

• Lymphocytic colitis
  
  • the biopsy shows increased lamina propria chronic inflammation (especially increased plasma cells) along with increased intra-epithelial lymphocytes and surface epithelial damage
  • crypt architecture is intact
• Collagenous colitis
  
  • band of subepithelial collagen + above stuff
  • crypt architecture is intact

Question 10

What are the typical clinical presentations of microscopic colitis?

Answer 10

Patients present with chronic watery diarrhea and a normal colonoscopic exam.

Question 11

What class of drugs is commonly implicated in drug-induced enterocolitis?

Answer 11

NSAIDs

_{(also Chemotherapeutic agents and Antibiotics)}

Question 12

Define and describe irritable bowel syndrome.

Answer 12

• chronic, relapsing, abdominal pain or discomfort, bloating, and changes in bowel habits (diarrhea or constipation)
  
  • in the absence of any known causative agent that could explain the symptoms.
• Endoscopic/colonoscopic/microscopic examination reveals no abnormalities
• clinical syndrome → requires excluding organic causes of the symptoms
• different subtypes → based on stool consistency

Question 13

What are the causes of ischemic bowel disease?

Answer 13

• Acute arterial obstruction/thrombosis:
  
  • atherosclerosis, aortic aneurysm, hypercoagulable states, and thromboembolism
• Mesenteric venous thrombosis:
  
  • hypercoagulable states, portal hypertension due to cirrhosis, trauma, invasive neoplasms, abdominal masses that compress portal drainage
• Hypoperfusion:
  
  • cardiac failure, shock, dehydration, vasoconstrictive drugs, vasculitis

Question 14

How are the bowel segments most likely to be affected by ischemia in ischemic bowel disease?

Answer 14

• Mucosal ischemic injury results in:
  
  • atrophy/loss of surface epithelium
  • hemorrhagic and hyalinized lamina propria
  • crypt atrophy
• Severe ischemic injury results in coagulative necrosis of the bowel layers (complete necrosis of all three layers in transmural infarcts).

Question 15

What are the complications of transmural bowel necrosis?

Answer 15

sepsis due to break down of the mucosal barrier, with septic shock and death

Question 16

Define angiodysplasia.

Answer 16

Lesion consisting of malformed submucosal and mucosal blood vessels.

Question 17

What is the clinical presentation of angiodysplasia?

Answer 17

• Lower GI bleeding
  
  • bleeding may be acute and massive (hematochezia, bright red blood in the stool) or chronic and intermittent.
• Typically occurs in the cecum and right colon in older adults

Question 18

Define and describe sigmoid diverticulitis.

Answer 18

• Formation and inflammation of multiple diverticulae in the sigmoid colon
• Pathogenesis is related to elevated intra-luminal pressure in the sigmoid colon
  
  • focal discontinuities of the inner muscular coat exist → leads to outpouchings of mucosa

Question 19

What are the common complications of sigmoid diverticulitis?

Answer 19

• Lower GI bleed
• Abscess formation
• Perforation
• Fistula

Question 20

Define and describe solitary rectal ulcer syndrome.

Answer 20

• Malfunction of the puborectalis muscle → leads to excessive straining on defecation
  
  • Straining → leads to rectal mucosal prolapse that can ulcerate and form polypoid masses (inflammatory polyp)
  • typically on the anterior rectal wall, 4-10 cm from the anal verge
• Lesion can mimic adenocarcinoma or the ulcers seen in Crohn’s disease.
• Microscopically → fibromuscular hyperplasia of the lamina propria, along with inflammation and ulceration, including reactive crypt hyperplasia.

Question 21

What is the clinical significance and morphology of inflammatory polyp?

Answer 21

• Clinical significance:
  
  • Associated with conditions such as solitary rectal ulcer syndrome, ulcerative colitis, and Crohn’s disease.
• Morphology:
  
  • inflammatory, non-neoplastic
  • inflamed and regenerating mucosa that projects above the level of the surrounding mucosa, which is frequently ulcerated

Question 22

What is the clinical significance and morphology of juvenile (retention) polyp?

Answer 22

• Clinical Significance:
  
  • most common type of polyp to occur in young children (polyp can also occur in adults)
  • can result in rectal bleeding
  • increased risk for GI tract adenocarcinomas
• Morphology:
  
  • Hamartomatous polyp that can occur sporadically or as the result of a polyposis syndrome
  • occur in the colon (usually rectum) and are typically solitary

Question 23

What is the clinical significance and morphology of Peutz-Jeghers polyp?

Answer 23

• Clinical Significance:
  
  • can present in childhood with GI bleeding and intussusception
  • Patients with PJS can have loss of function mutations of STK11 which is a tumor suppressor gene
  • patients are at risk for the development of GI tract adenocarcinomas, as well as malignancies of other organs (breast, lung, pancreas, gonads, uterus)
• Morphology:
  
  • Hamartomatous polyps + mucocutaneous hyperpigmentation
  • arborizing smooth muscle pattern and are frequently pedunculated

Question 24

What is the clinical significance and morphology of hyperplastic polyp?

Answer 24

• Clinical significance:
  
  • most common type of adult colonic polyp
• Morphology:
  
  • proliferative polyp without significant malignant potential
  • most are small (less than 0.5 cm in size)
  • found in the left colon, especially the rectum.
  • Polyps may be single or multiple

Question 25

What is the clinical significance and morphology of adenoma (adenomatous polyp)?

Answer 25

* Clinical significance: * benign → but can be precursors to adenocarcinoma, although most adenomas do not become malignant * needs to be completely removed * Morphology: * Neoplastic polyp characterized by dysplastic glandular proliferation * consist largely of a tubular proliferation of glands (tubular adenoma), or more villous proliferation (villous adenoma), or mixed *

Question 26

What is the clinical significance and morphology of the sessile serrated polyp?

Answer 26

* Clinical significance: * hyperplastic polyps → can be precusors to adenocarcinoma * complete endoscopic polypectomy is recommended * Morphology: * These polyps lack the adenomatous epithelium of the conventional adenomas * Adenomatous type epithelial changes * low-high grade dysplasia

Question 27

What are the key features of Peutz-Jeghers syndrome?

Answer 27

* multiple Peutz-Jeghers polyps and mucocutaneous hyperpigmentation * Patients with PJS can have loss of function mutations of STK11 which is a tumor suppressor gene * patients are at risk for the development of GI tract adenocarcinomas, as well as malignancies of other organs

Question 28

What are the features of FAP?

Answer 28

* Autosomal dominant inherited mutations in the APC tumor suppressor gene * Develop large numbers of adenomatous polyps in the colon and rectum during late childhood, adolescence, and early adulthood. * 100% risk of colorectal adenocarcinoma * 70-80% pts have congenital hypertrophy of the pigmented retinal epithelium * Tx: screening + postadolescent prophylactic colectomy

Question 29

What are the features of Lynch syndrome (HNPCC)?

Answer 29

* mutations in the genes that encode enzymatic mismatch repair proteins responsible for the detection, excision, and repair of errors that occur during DNA replication * greatly increased risk of malignant transformation of adenomas, and the risk for colon cancer is 80-90%