3B - Large Intestine Pathology Flashcards Preview

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Flashcards in 3B - Large Intestine Pathology Deck (56):
1

Vomiting before onset of pain suggests ___

Gastroenteritis or obstruction

2

Vomiting after onset of pain suggests ___

Appendicitis

3

Complications of acute appendicitis

  1. Post-op wound infection
  2. Perforation
    • Periappendiceal abscess
    • Peritonitis

4

In women with suspected acute appendicitis, must do ___ first. 

Pelvic (and beta-HCG) to rule out gynecologic etiology

5

Dianosis of acute appendicitis (2)? 

  1. CT (good Sn & Sp)
  2. U/S

6

Top 3 causes of hemorrhoids

  1. Straining at defecation (MC)
  2. Pregnancy
  3. Portal HTN

7

Internal hemorrhoids pathogenesis: Elevated pressure in the ___

Superior venous plexus

8

Enternal hemorrhoids pathogenesis: Increased venous pressure within the ___

Inferior hemorrhoidal plexus

9

Complication of external hemorrhoids

Painful thrombosis

10

Rectal prolapse in a child, consider ___

CF

11

Dx?  Tx?

  • Perianal pain
  • Fever
  • Difficulty voiding
  • Fluctuant tender mass in perianal region

 

Anorectal abscess

Drainage

12

Abnormal channel between an anorectal abscess and the anal mucosa or perianal skin

Anal fistula

13

Chronic anal fissure has ___ at the proximal end and a ___ at the distal end. 

  1. Hypertrophied anal papillae
  2. Sentinel pile (skin tag)

14

___ may have a protective role in colorectal carcinoma due to their role in inhibited prostaglandins (which promote epithelial proliferation)

NSAIDs

15

___ mutations (sporadic or germline) increase risk for formation of polp

APC

16

___ mutations lead to formation of polyp(s)

K-ras

17

___ mutations and increased expression of ___ allow for progression to carcinoma

  1. P53
  2. COX

18

Colorectal carcinoma is often asymptomatic and detected during screening colonoscopy. Other common clinical presentations include (5): 

1. Iron-deficiency anemia and complications

2. Rectal bleeding

  • Right sided à much wider lumen

3. Abdominal pain

4. Change in bowel habits

5. Intestinal obstruction or perforation

  • Left sided à obstruction, pencil-thin stools

19

The following can cause a false-positive guaiac test (5)

  1. Red meat (recent injestion)
  2. NSAIDs (associated GI bleeding)
  3. Turnips (food with peroxidase activity)
  4. Broccoli (food with peroxidase activity)
  5. Horseradish (food with peroxidase activity)

20

Two causes for false-negative guaiac tests

  1. Tumor may not bleed
  2. Vitamin C (antioxidant properties)

21

___ is recommended preoperatively.                                                                              If high before surgery, it is expected to normalize following resection of tumor. Rising levels indicate progression or recurrence of colorectal carcinoma. 

NOT RECOMMENDED AS A SCREENING TOOL

CEA

22

S/S of left colon colorectal carcinoma (3)

  1. Decreased stool diameter
  2. Andominal cramping
  3. Obstruction → perforation

23

S/S of right sided colorectal carcinoma

  1. Bleeding → iron deficiency anemia
    • Anemia symptoms
      • Fatigue
      • Palpitations
      • Decreased exercise tolderance
      • Angina

24

Colon cancer metastasis

  • Mesenteric LN
  • Liver
  • Lungs
  • Ovary
  • Brain

25

Colorectal cancers of the distal rectum may metastasize initially to the ___ because the inferior rectal vein drains into the IVC. 

Lungs

26

Because the venous drainage of the intestinal tract is via the portal system, the first site of hematogenous dissemination is usually the ___

Liver

27

Primary treatment for colorectal carcinoma is ___

Surgical resection

28

Left-sided colorectal carcinoma tend to progress through the ___ pathway

APC (adenoma-carcinoma sequence)

29

Right-sided colorectal carcinoma tend to progress through the ___ pathway

MSI

30

With an adenomatous polyp, risk of malignancy is directly proportional to ___, ___, ___

  1. Size (>2 cm)
  2. Number
  3. Villous component % (villous greater risk)

31

Polyp?

  • Dysplastic by definition, thus premalignant
  • Due to neoplastic proliferation of the glands via chromosomal instability pathway (adenoma-carcinoma sequence) with mutations in APC and K-ras

Adenomatous Polyp

32

Polyp?

  • MC type

  • Due to hyperplasia of glands

  • Generally smaller

  • Usually in left colon (rectosigmoid)

  • Benign

  • No risk of malignant change

Hyperplastic Polyps

33

Polpy?

  • ŸHamartomatous lesions

  • Benign

  • MC in children, usually in rectum

  • Presents with rectal bleeding

  • May prolapse from rectum

Juvenile (Retention) Polyp

34

Polyposis Syndrome? 

Rare, autosomal dominant

Characterized by:

  • Multiple hamartomatous polyps scattered throughout GI tract (stomach à rectum)

Risk of intussusception (50%)

Melanotic mucosal and cutaneous pigmentation (face, oral mucosa, lips, palms, genitalia)

Risk of developing various malignancies

  • Colon
  • Pancreas
  • Breast
  • Lung
  • Ovary
  • Uterus

Peutz-Jeghers syndrome

35

  • ŸAutosomal dominant disorder caused by germline mutation in the tumor suppressor gene, adenomatous polyposis coli (APC), located on chromosome 5q21-q22
  • ŸResults in hundreds to thousands of adenomatous polyps that “carpet” the colon from cecum to anus
  • ŸPancolonic; always involves rectum
  • ŸPolyps begin developing mid-teens; minimum 100 required for diagnosis
  • ŸTreatment: Colectomy in early adulthood
  • ŸIf left untreated, ALL develop colon cancer (usually by ~40 to 45 years)
  • Increased risk of adenocarcinoma of small intestine as well (ampulla)

Familial adenomatous polyposis (FAP)

36

  • Fewer polyps (<100)
  • Cancer risk increased but not as high as FAP
  • Polyps develop later (mid 30s) and cancers tend to develop later (mid 50s)

Attenuated FAP

37

FAP +

  • Osteomas (benign bone growths seen MC in mandible and skull) and soft tissue tumors
  • Congenital hypertrophy of the retinal pigment epithelium (CHRPE)
  • Epidermal cysts
  • Fibromatosis
  • Impacted / supernumerary teeth

Gardner syndrome

38

FAP +

  • Malignant brain tumors (medulloblastoma/glioblastoma)

Turcot syndrome

39

Diagnose patients for hereditary nonpolyposis colorectal cancer (lynch syndrome) by testing tumor cells for ___

Microsatellite instability (sequence changes reflecting defective mismatch repair)

40

Patients with lynch syndrome have increased risk of ___, ___, ___ cancers as well as colorectal cancers. 

  1. Endometrial
  2. Ovarian
  3. Gastric

41

Disease

M>F

Associated with Down's Syndrome

Failure to pass meconium (48 hours)

Risk: Perforation

Dx: Rectal suction biopsy

Tx: Surgical excision of aganglionic segment

Barium enema - tapered transition zone

Congenital aganglionic megacolon (Hirschprung's disease)

42

Slowly progressive constipation

Acquired aganglionosis

Reduviid "kissing" bug

Invades and destroyed ganglion cells

Most cases associated with dilated esophagus (achalasia), which results in megaesophagus

Chagas' Disease

43

Arteries that supply the splenic flexure (2)

  1. SMA
  2. IMA

44

Arteries that supply the rectosigmoid region (2)

  1. IMA
  2. Hypogastric artery

45

Atherosclerotic narrowing of mesenteric artery

Usually elderly patient with severe postprandial pain
(usually LUQ)

Loss of weight

Mesenteric angina

46

Due to acute vascular occlusion

  • Atrial fibrillation
  • Vascular procedures

Presents with severe acute abdominal pain, bloody diarrhea

Repair with fibrosis (scarring), which can lead to stricture (obstruction)

Infarction

47

—Clinical term used to describe both lymphocytic and collagenous colitis (only findings are microscopic)

—Both are characterized by:

  • Chronic non-bloody diarrhea
  • Normal endoscopy

—Differ histologically

—Lymphocytic: M=F

—Collagenous: F>>>M

Microscopic colitis

48

Liquid stool used for Dx:

  • Enzyme immunoassay for exotoxin A (enterotoxin), B (cytotoxin)
  • Identification of microbial toxin genes (never, high Sn/Sp)

Complication: Toxic megacolon (perforation)

B1/NAP1/027 strain - especially virulent strain with increased toxin production

Tx: Metronidazole, vancomycin, fedaxomicin

Pseudomembranous colitis

49

Potentially lethal complication of colitis (e.g., C. difficile, IBD, ischemic, etc.)

Characterized by non-obstructive colonic dilatation plus systemic toxicity (fever, tachycardia, leukocytosis)

Thought to be due to release of inflammatory mediators such as NO (inhibits smooth muscle tone, causing dilation)

Mortality increases with perforation

Toxic megacolon

50

ŸTortuous dilation of mucosal & submucosal vessels

ŸMore common in cecum/right colon (highest wall tension)

ŸPathogenesis:

  • ŸTheorized to be due to intermittent, recurrent low-grade obstruction of submucosal veins within colonic wall
  • ŸOver many years, the obstruction results in dilatation and tortuosity of the draining vessels (i.e., submucosal vessels, venules, and superficial capillaries

Associated with aortic stenosis

Dx: Colonoscopy/angiography

Common cause of GI (along with diverticulosis) - hematochezia

Angiodysplasia

51

If bleeding (hematochezia) is recurrent and/or massive in the case of angiodysplasia, treatment options include (3):

  1. Endoscopic cauterization
  2. Intravascular embolization
  3. Hemicolectomy

52

MC sigmoid colon

Increases with age; common 35-50% of population

Increased with patients with CT disorders

Pathogenesis: Increased intraluminal pressure in combination with area of weakness where vasa recta penetrate the muscularis propria

Diverticula

53

Fecal impaction of diverticulum causes obstruction with subsequent ulceration, ischemia, inflammation

Clinical findings:

  • Acute abdominal pain (LLQ) and fever
  • LLQ tenderness and mass
  • Leukocytosis

Imaging studies:

  • CT scan best

Diverticulitis

54

Other possible complications (besides diverticulitis) with diverticular disease

  1. Bleeding (OSIS, not itis)
  2. Perforation with peritonitis/abscess

55

Treatment for diverticular disease

Non-pharm: high fiber diet

Acute disease: antibiotics

Colonic resection (selected severe cases)

56