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1

Colon & Rectum - Development

First trimester of gestation
Distal midgut (Cecum to splenic flexure) & hindgut (splenic flexure to rectum)

2

Colon & rectum - Size

1m long
2L capacity

3

Colon & Rectum - Regions

Cecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
Rectum

4

Colon - 5 layers

Mucosa
Submucosa
Circular muscle
Longitudinal muscle
Serosa

5

Colon - Haustra

Tonic contractions of rings of circular muscle (plicae semilunares coli)

6

Colon - Circular muscle layer control

Thin layer of cells, interstitial cells of Cajal on submucosal surface of smooth muscle layer

7

Colon & Rectum - Histo

Mucosa:
Columnar cells
Goblet cells
Enteroendocrine cells (mainly located in the crypts)

No Villi

Epithelial cells proliferate in lower parts of crypts, migrate toward surface

8

Blood supply: Cecum, Ascending Colon, Transverse Colon

SMA

9

Blood Supply: Transverse Colon, Descending Colon, Sigmoid Colon, Rectum

IMA

10

Venous drainage

Analogous to arterial supply

11

Colon - Neuronal supply

Intrinsic and extrinsic neurons

Extrinsic - Autonomic

Parasympathetic innervation supplied by vagal fibers (midgut derivatives) or the nerves of the pelvic plexus from sacral spinal cord (hindgut derivatives)

12

Colon & Rectum purpose

Maintain fluid & electrolyte balance
Salvage products of intra-colonic fermentation
Store waste materials
Recover 1.5L fluid per day (mostly in proximal colon)
1 - 2 bowel movements/day
Can absorb sodium against high electrochemical gradient!

13

Colon & Rectum - Pharmacology

Most drugs already absorbed by that point

EXCEPT Sulfasalazine (used to treat UC)

14

Sulfasalazine

Composed of sulfapyridine (sulfonamide antibacterial) linked by a diazo bond with 5-Aminosalicylic acid (5-ASA, or mesalamine)

15

5-ASA

The active therapeutic moiety of sulfasalazine.

The sulfapyridine just prevents 5-ASA from being absorbed earlier. The diazo bond is broken by bacterial action.

5-ASA decreases inflammation in the colon.

16

Microbiome

10^10 organisms/mL

Represent a pool of metabolic enzymes

Anaerobes, can thrive in low-oxygen tension

Modify oxygen tension, pH, mucopolysaccharide composition & hydration capacity of stool solids.

Normal flora protects against pathogenic bacterial proliferation. Homeostasis between types of bacteria.

17

Colon & Rectum - Vascular Diseases

Ischemic colitis
Diverticular bleeding
Hemorrhoidal bleeding

18

Colon & Rectum - Neoplastic Diseases

Colon polyps
Colorectal cancer

19

Colon & Rectum - Infectious Diseases

Appendecitis
Bacerial/Viral Colitis
Clostridium Difficile
Diverticulitis

20

Colon & Rectum - Mechanical Diseases

Volvulus
Large bowel obstruction

21

Colon & Rectum - Immunologic Diseases

IBD
Collageneous/Microscopic Colitis
Ileus

22

Colon & Rectum - Motility Diseases

Ileus
IBD

23

Ischemic Colitis - Presentation

Crampy, mild LLQ abdominal pain

Urge to defecate

Pass bright red (or maroon) blood mixed with stool

24

Ischemic Colitis - Morphologic Changes

Vary with duration & severity of injury

25

Ischemic Colitis - Watershed Areas

Splenic Flexure
Rectosigmoid

Due to limited collateral flow

26

Ischemic Colitis - Mildest injuries

Reversible

Mucosal & submucosal hemorrhage & edema

with or without partial necrosis of the mucosa

27

Ischemic Colitis - Unresorbed Hemorrhage

Overlying mucosa sloughs off, forming an ulcer.

28

Ischemic Colitis - Prolonged Severe Ischemia

Muscularis propria is damaged, replaced with fibrous tissue.

Stricture.

29

Ischemic Colitis - Most Severe

Trans-mural infarction
Gangrene
Perforation

30

Diverticulae

Herniations of colonic mucosa through defects in the muscularis layer, resulting in formation of pseudodiverticulae (wall is only made of mucosa and serosa)

Common. Found in 50% of individuals over age 60 on western diet, and 2/3 of patients over 80

Cause unknown

31

Hypothesis of diverticulae origins

Low fiber western diet
Lower stool volume
Smaller stools
More colon segmentation
High pressures in colonic lumen
Mucosa forced through wall of colon where nutrient vessels enter.

32

Diverticulosis

Only 5% of these patients bleed significantly

Still, however, one of the most common causes of Lower GI Bleed

33

Diverticulae most common in

Left colon

34

Diverticular bleeding most common in

Right colon

35

Diverticular bleed - Pathway

Diverticulum expands
Small arterioles running adjacent bleed briskly.

Painless!!

Most episodes stop spontaneously.

50% recur

36

Diverticular bleeding

Sudden
Painless
May be severe

May present with hypovolemia before blood appears in the rectum (a large amount of blood can be stored in the colon)

Nutrient arteriole ruptures at the base of the diverticulum (maybe due to a fecalith impaction?)

37

Small amounts of blood in stool, or intermittent rectal bleeding

Probably not diverticular bleed.

More likely hemorrhoids, proctitis, polyps or carcinoma

38

Iron deficiency anemia

NEVER explained by diverticular bleeding.

Typically a long-standing microcytic anemia, where patients are unaware that they're losing blood.

Diverticular bleeds are FAR too overt and large volume for that.

39

NSAIDs or Aspirin

Increase likelihood of diverticular bleeds

40

Diverticular Bleeding - Treatment

Resuscitate patient (IV fluids, packed RBC)
Assess blood loss

Administer ADH
Selectively embolize the bleed
Surgery may be necessary
Often the bleeding stops spontaneously
We may also have to clip the diverticulum.

After the bleeding stops, we must do a colonoscopy to check.

41

Differentiate Diverticular Bleed from Upper GI Bleed

BUN Elevated in an Upper GI Bleed because the body resorbs the blood.

Sometimes also a lavage via NG tube would also reveal an upper GI bleed too.

42

Tagged Radionuclide Red Blood Cell Scan

Localize where the bleeding is coming from.

Send patient to interventional radiology where they can administer ADH, then selectively embolize by angiography.

43

Hemorrhoidal Bleeding

Occur in >50% of individuals in USA

Most common cause of Lower GI Bleed in adults

Present with scant hematochezia usually.

Occasionally bleed massively

Path unknown

44

Hemorrhoidal Bleeding - Conservative Treatment

Topical anti-inflammatory agents
Increased dietary fiber

45

Hemorrhoidal Bleeding - More extreme measures

Rubber band ligation
Injection sclerotherapy
Cryosurgery
Electrocoagulation
Laser ablation
Photocoagulation

46

Lower GI Bleed - Differential

Diverticular
Hemorrhoidal
Arteriovascular Malformations
Stercoral Ulcers
Neoplasms
Mechanical Injury (post-polypectomy bleeding)

47

Arteriovascular Malformation - Colon

Typically leads to iron deficient anemia.

If patient is on Warfarin, it can lead to massive bleed, but this is less common.

48

Stercoral Ulcers

Pressure necrosis
Patients constantly impacted
Stool pressing against the wall causes the wall to necrose.

Mentally-impaired patient not receiving enough attention to their bowel movements.

49

Colon Cancer

Can bleed, but typically presents with an iron deficiency anemia.

50

Colon Neoplasia

Colorectal adenoma
Colorectal adenocarcinoma
Colorectal hyperplastic polyp
Colorectal sessile polyp
Carcinoids of the colon and rectum
Leiomyomas of the colon and rectum
Gastrointestinal stromal cell tumors of the rectum and colon

51

FAP

Familial Adenomatous Polyposis

52

Appendicitis - Lifetime risk in western populations

7%
Slightly higher male predominance in 2nd and 3rd decades of life

53

Appendix

Previously thought to be vestigial
Now thought to have a role in intestinal immunity

Has many lymphoid follicles
# of follicles peaks between ages 10 - 30.

54

Appendicitis - Causes

70% due to obstruction of the appendiceal lumen:

Fecaliths
Tumors
Parasites
Lymphoid hyperplasia

55

Obstruction of the appendiceal lumen is followed by

Mucus secretion
Bacterial overgrowth
Increasing intra-luminal pressure and wall tension
Vascular congestion
Gangrene and perforation.

56

Appendicitis - Atypical presentation

Appendix lies in atypical positions (Retrocecal, retroileal)

Increased risk of perforation (due to delayed diagnosis)

57

Most common microbes for appendicitis

E. Coli is most common gram-negative
B. Fragilis is most common anaerobe, second only to E. Coli overall

Most infections are polymicrobial

58

Appendicitis - Diagnosis

H&P are major
Abdominal pain is primary symptom.
Classically peri-umbilical, but may be epigastric or suprapubig
After 1 - 12 hours, pain migrates to RLQ (McBurney's Point), becomes more intense
Anorexia
Nausea
Rovsing's Sign
Fever
Elevated WBC

59

Appendicitis - When should you question your diagnosis?

If vomiting precedes abdominal pain.

60

McBurney's Point

2/3 of the distance from umbilicus to ASIS

61

Rovsing's Sign

Palpation of LLQ produces pain in RLQ

62

Appendicitis - Imaging

Abdominal CT = Gold Standard
Dilated appendix
Edema
Mesenteric stranding around the appendix in the RLQ

63

Appendicitis - Treatment

Appendectomy for nearly all patients.

Give prophylactic antibiotics to prevent infection.

Patient presents late in course after perforation, we give a course of antibiotics and see what happens

64

Appendectomy - Most common complication

Infection.

This is why we give single dose broad spectrum antibiotics as prophylaxis. Without these, the wound infection rate is 9 - 30% in early appendicitis. Late appendicitis, this approaches 80%.

With ppx, infection risk is

65

Appendectomy - Perforation

Rates of 20 - 30% over the last 70 years
Precedes surgical evaluation in most cases
Increases risk of second laparotomy by more than 250%

66

Diverticulitis - Average Age

44 years

67

Appendicitis - Average Age

Much Younger

68

Diverticulitis - Duration

3.3 days

69

Appendicitis - Duration

24 hours

70

Diverticulitis - Location

RLQ of abdomen

71

Appendicitis - Location

Epigastrium initially, then RLQ

72

Diverticulitis - Nausea

20%

73

Appendicitis - Nausea

80%

74

Infectious causes of colitis - Bacterial

Campylobacter
C. Difficile
E. Coli
Salmonella enteritidis
Shigella
Yersinia
Aeromonas

75

Infectious causes of colitis - Viral

Adenovirus
Norwalk virus
Rotavirus
Others

76

Infectious causes of colitis - Parasitic/Protozoal

Entamoeba histolytica
Giardia lambia
Cryptosporidium
Cyclospora

77

Food Poisoning - Microbes

B. Cereus
C. Perfringens
Salmonella
Staphylococcus
Vibrio
Shigella
Campylobacter
E. Coli
Yersinia Enterocolitica
Listeria Monocytogenes

78

Clostridium Difficile

Most common cause of nosocomial infectious diarrhea

Present in 3 - 5% of healthy, asymptomatic adults.

79

Clostridium Difficile - Range of Clinical Presentation

Varies.

Mild self-limited illness
Diarrhea
Resolves soon after withdrawal of offending antibiotic

OR

Severe pseudomembranous colitis
Fever
Profuse watery, non-bloody diarrhea
Toxicity
Toxic megacolon
Significant mortality

Small bowel rarely affected
Diarrhea often associated with fever, crampy abdominal pain, leukocytosis

80

C. Diff - More serious complications

Toxic megacolon
Colonic perforation

81

Toxic Megacolon

The colon shuts down
Adynamic ileus
Severe risk of gangrene and perforation.

82

C. Diff - Endoscopy

Pseudomembranes!!

Looks almost like oral thrush

83

C. Diff - Risk factors - Antibiotics

Within 4 - 8 weeks of presentation:

Clindamycin
Ampicillin
Amoxicillin
Cephalosporins
Fluoroquinolones (eg Levofloxacin or Ciprofloxacin)

84

C. Diff - Risk factors - Non antibiotics

Hospitalization
Recent surgery
Uremia
Crohn's Disease
Severe concurrent infection
Recent cancer chemotherapy

85

C. Diff - Diagnostic

Gold standard - Tissue Culture Assay

Rarely have to do that, though. Frequently just send a stool sample for latex particle agglutination immunoassays(Sensitivity 87%, Specificity 99%)

Endoscopic/Histologic pseudomembranes are pathognomonic

86

C. Diff - Treatment

Offending antibiotic should be discontinued if possible

Oral antibiotic therapy prescribed for 14 days

If patient can't handle oral medication, give metronidazole 500mg IV q 8 hours

Do NOT give IV vancomycin. It will not work. PO will, though.

87

C. Diff - Surgery

In the cases of:

Refractory colitis
Toxic megacolon
Perforation

88

C. Diff - Metronidazole

500 mg po TID
OR
250 mg po QID

Response rate: 98%
Relapse rate: 7%

89

C. Diff - Vancomycin

125 mg po QID

Response rate: 96%
Relapse rate: 18 %

90

C. Diff - Bacitracin

25,000 U QID

Response rate: 83%
Relapse rate: 34%

91

C. Diff - Cholestyramine

4 gm po TID

Response rate: 68%
Relapse rate: Unknown

Binds to the toxin of C. Diff and helps patient expel that toxin.

92

C. Diff - Relapses

10 - 20% of cases

Usually due to incomplete eradication of initial infection

Spores can live for 2 weeks after completion of antibiotic course

93

C. Diff - Relapse treatment

Metronidazole 500 mg po TID

PLUS

Rifampin 300 mg po BID

OR

Vancomycin 125 mg po QID and TAPER steadily (over 6 weeks) down to one tablet every 2nd or 3rd day.

94

Diverticulitis

Infected diverticulum

Most frequently occurs in sigmoid colon

10 - 25% of patients with previously-recognized diverticulosis

Risk increases over time. 10% after 5 years with diverticulosis, 35% after 20 years with diverticulosis

60% of patients with a first episode will have mild illness, can be treated as outpatients with abx

95

Diverticulitis - Antibiotic regimen

Should cover:

Enterobacteriacea
Bacteroides
Pseudomonas (less frequent)
Enterococci (less frequent)

96

Diverticulitis - Path

Inspissated fecal matter in a diverticulum may form a fecalith

Causes impaction within diverticulum
Local mucosal inflammation
Ensuing necrosis
Microperforation of macroperforation

97

Diverticulitis - Microperforation

Initially contained by pericolonic tissues (mesentery, fat, adjacent organs)

See peritoneal air, but you don't see contrast spilling out. Air has perforated through the diverticulum, but then it healed.

This results in an inflammatory mass or phlegmon

Can be treated with antibiotics, bowel rest, supportive care.

98

Diverticulitis - Repeated Microperforation

May lead to fibrosis of colonic wall, then stricture

99

Diverticulitis - Macroperforation

Result of free perforation with generalized peritonitis

Needs surgery

100

Diverticulitis - Peri-diverticular abscess

May result in a fistula

101

Diverticulitis - Imaging

Abdominal CT
Fat stranding and/or a mass in the LLQ

102

Diverticulitis - Clinical Picture

LLQ pain in 93 - 100% of patients
Change in bowel habits
Fever (86% of patients)
Leukocytosis (in up to 90% of patients)

If fistula to bladder formed:
Frequency, urgerncy, pneumaturia, fecaluria

LLQ abdominal tenderness
Mass may be palpable
Involuntary guarding & rebound tenderness (if peritonitis)

103

Diverticulitis - Diagnostic Studies

Abdominal/Pelvic CT with IV contrast

Colonoscopy or Sigmoidoscopy not done in acute setting (fear of worsening perf)

104

Diverticulitis - Treatment (Mild Disease)

Liquid or low residue diet
Oral antibiotics 7 - 10 days:
Metronidazole + either Levofloxacin, TMP-Sulfa, Ciprofloxacin or Amoxicillin-Clavulanate

105

Diverticulitis - After resolution of acute attack

Colonoscopy 4 - 6 weeks to rule out colitis, polyps, cancer

106

Diverticulitis - Surgery

Not indicated after first episode, since only 20 - 30% recur.

Should be considered 4 - 6 weeks after THIRD episode inflammation has resolved

107

Diverticulitis - Recurrence

Usually take place within 5 years of the initial episode

108

Diverticulitis - Indications for hospitalization

Severe pain
Inability to tolerate oral diet
Failure of symptoms to resolve with outpatient therapy
Clinical toxicity (High fever, worsening leukocytosis)

109

Vovlulus

Twisting of colon around the mesentery

180 degrees minimum for significant obstruction to occur

If intraluminal pressure exceeds capillary perfusion pressure, vascular compromise may occur. Leads to ulcer, necrosis, grangrene and perforation.

If obstruction persists, strangulation is initiated by venous thrombosis, followed by arterial occlusion and infarction.

110

Volvulus - Locations

Stomach
Cecum
Sigmoid

111

Volvulus - Predisposing Factors

Congenital or Acquired:

Long, redundant (from long-standing constipation), mobile sigmoid colon
Elongated, freely movable sigmoid mesentery
Narrow mesenteric attachment frequently scarring at the base (from repeated twisting)

112

Sigmoid Volvulus

Axial torsion of sigmoid volvulus usually occurs in counterclockwise direction around mesenteric base.

Attacks can be subacute or acute fulminating.

60% of patients with sigmoid volvulus report prior attacks that spontaneously resolved

113

Sigmoid Volvulus - Barium Enema

Bird's beak in the sigmoid. No more contrast beyond that point very dilated loop of bowel.

114

Sigmoid Volvulus - Epi

Highest prevalence - Underdeveloped countries with high-residue diet with vegetable fiber.

Accounts for 3 - 10% of colonic obstructions in the western world

M:F
3:1 (men have longer sigmoids, women have wider pelvises)

115

Most common cause of Lower Bowel Obstruction in pregnancy

Sigmoid Volvulus

116

Chronic constipation leads to

Lengthening of the sigmoid

117

Sigmoid volvulus - Physical findings

Markedly distended abdomen
Tympanic
No (or low) bowel sounds

118

Sigmoid volvulus - Diagnosis

Plain films are diagnostic in 2/3 or cases

Contrast studies:
Bird's beak
Ace of spades

119

Sigmoid volvulus - Therapeutic Goals

Relief of acute torsion
Prevention of recurrence

120

Sigmoid volvulus - Treatment

85 - 90% of subjects can be decompressed by sigmoidoscopy (if mucosa is not ischemic or necrotic)

121

Sigmoid volvulus - Recurrence

High recurrence rate
Mortality higher after recurrence than it was after initial episode.

122

Sigmoid volvulus - Surgery

Best to do it electively after 2nd or 3rd occurrence. Typically a complete sigmoid resection is indicated.

If patient presents emergently and is peritoneal, surgery may be indicated earlier.

123

Large Bowel Obstruction

Result of any mechanical obstruction in the large intestine not permitting the passage of stool or gas.

Can be secondary to tumor, stricture, extrinsic compression

124

Large Bowel Obstruction - Presentation

Obstipation
Abdominal Distention
Abdominal Pain

Can be toxic on presentation, depending on degree of ischemia caused

125

Large Bowel Obstruction - Perforation

Occurs if underlying mechanical obstruction is not treated.

126

Large Bowel Obstruction - Treatment

Surgery
Enteral stents

127

Large Bowel Obstruction - Imaging (Tumor)

Barium enema:
Apple core lesion in the colon
Very dilated upstream colon

128

Crohn's Disease

Full thickness inflammation of bowel wall.

Results in:
Strictures
Fistulas
Abscesses

Relapsing remitting course treated by topical anti-inflammatory agents & immunomodulators

129

Ulcerative Colitis

Superficial colitis of bowel beginning in rectum and extending proximally contiguously for varying lengths
(Proctitis vs. Pancolitis)

Clinically, patients present most often with bloody diarrhea, weight loss

Total colectomy - Curative

130

Collagenous / Lymphocytic Colitis

Microscopic Colitis

Typically elderly patients on long-standing NSAIDS

Syndrome:
Watery diarrhea
No specific endoscopic or radiographic abnormalities of the bowel

May be the same disease with a part of the spectrum containing collagen, but may be separate. We don't know.

Relapsing remitting course over years

131

Collagenous Colitis

Watery Diarrhea
Sub-epithelial collagen band in colonic mucosa
Chronic inflammatory infiltrate in lamina propria

132

Lymphocytic colitis

Watery diarrhea
No collagen band in the colonic sub-epithelium
Intraepithelial lymphocytes present

133

Lamina propria of normal colonic mucosa

Scattered lymphocytes, monocytes, eosinophils

If there is subepithelial collagen, it is very narrow (3 microns or less in diameter)

134

Collagenous Colitis - Histo

Thickened subepithelial collagen layer (20 -60 microns)

Collagen band not a marker for disease severity, no correlation between thickness and age/duration of disease

135

Collagenous / Lymphocytic Colitis - Appears like

Celiac Sprue. If they don't get better on a gluten free diet, they may have collagenous/lymphocytic colitis.

136

Collagenous / Lymphocytic Colitis - Endoscopy

NORMAL

137

Collagenous / Lymphocytic Colitis - Symptoms

Secretory diarrhea, so persists even when fasting
Watery stools
8 stools/day average
Cramping pain
Nausea
Weight loss
Fecal urgency
Fecal incontinence

138

Collagenous Colitis - Epi

50 - 70 year olds
M:F
20:1

139

Lymphocytic Colitis - Epi

51 years old
M:F
1:1

140

Collagenous/Lymphocytic Colitis - Physical Exam

Unremarkable or mild abdominal tenderness

141

Collagenous Colitis - Associated with

Rheumatoid Arthritis
Seronegative Polyarthritis
Thyroid disease
Diabetes Mellitus
CREST Syndrome

142

Lymphocytic Colitis - Associated with

Rheumatoid Arthritis
Sicca Syndrome
Uveitis
Diabetes Mellitus

143

Collagenous / Lymphocytic Colitis - Diagnosis

Characteristic histopathologic changes in colonic mucosal biopsies from patient with chronic watery diarrhea

Blood/stool studies are USELESS!!!!

144

Collagenous / Lymphocytic colitis - Treatment

Remove NSAID use
Bismuth subsalicylate tablets induce remission

Mild/Intermittent - Antidiarrheal drugs:
Diphenoxylate with Atropine, loperamide, psyllium or methylcellulose

Troublesome/Persistent - Anti-inflammatory agents such as sulfasalazine and mesalamine

Unresponsive to anti-inflammatories - Corticosteroids

Last resort - Surgery

145

Adynamic Ileus or Pseudo-Obstruction

Failure of effective peristalsis without mechanical obstruction

146

Adynamic Ileus or Pseudo-Obstruction - Causes

Metabolic abnormalities (uremia, electrolyte abnormalities)
Drugs (Narcotics, opiates, anti-cholinergics)
Local or systemic infections (C. Diff)
Non-infectious Inflammatory Processes (Pancreatitis)
Neurogenic causes (spinal cord injury)
Post-operative Ileus (Ogilvie Syndrome)

147

Adynamic Ileus or Pseudo-Obstruction - Presentation

Abdominal Pain
Lack of bowel sounds
or
High pitched bowel sounds

148

Distinguish Ileus from Obstruction

Barium Enema
Obstruction - Contrast doesn't make it all the way across the colon.
Ileus - Air fluid levels

149

Ileus - Management

Supportive care through fluid & electrolyte management
Remove precipitating agent
Decompress EARLY

150

Ileus - If patient doesn't get better with only supportive care

Try neostygmine
Get a surgical consult, in case emergency surgery is needed (rare).

151

Irritable Bowel Syndrome

22% of the US population
28% of GI visits

Chronic disorder (unknown origin). Maybe visceral hypersensitivity?

Alterations in bowel habits and exacerbations/remissions of abdominal pain and discomfort

Diagnosis of exclusion

152

Irritable Bowel Syndrome - Presentation

Abdominal pain/discomfort
Relieved with defecation
Associated with a change in frequency of bowel movements and/or altered stool form
Passage of mucus or bloating/distention

153

Irritable Bowel Syndrome - Types

Diarrhea predominant
Constipation predominant
Mixed

154

Irritable Bowel Syndrome - Treatment

Bulking agents
Anti-diarrheal agents
Smooth muscle relaxants
Pro-kinetic agents
Antidepressants
Anxiolytics
Psychologic and behavioral treatments.