Intestinal Pathology 1

Question 1

Congenital Malformations

Answer 1

Meckel diverticulum (failure of the vitelline duct to involute)
- Ileum

Hirschsprung Disease
- Large Bowel

Question 2

Meckel DiverticulumRule of 2s

Answer 2

Occur in approximately 2% of the population

Are generally present within 2 feet (60 cm) of the ileocecal valve

Are approximately 2 inches (5 cm) long

Are twice as common in males

Are most often symptomatic by age 2 (only approximately 4% are ever symptomatic)

Question 3

Hirschsprung Disease

Answer 3

Occurs in approximately 1 of 5000 live births
10% of all cases occur in children with Down syndrome, serious neurologic abnormalities are present in another 5%.
Normal migration of neural crest cells from cecum to rectum is arrested prematurely or the ganglion cells undergo premature death.

typically presents with a failure to pass meconium in the immediate postnatal period.

Obstruction or constipation, often with visible, ineffective peristalsis, that may progress to abdominal distention

Primary mode of treatment is surgical resection of the aganglionic segment followed by anastomosis of the normal proximal colon to the rectum

Question 4

Signs and Symptoms

of Gastrointestinal Obstruction

Answer 4

Crampy abdominal pain that comes and goes.
Nausea.
Vomiting.
Diarrhea.
Constipation.
Inability to have a bowel movement or pass gas.
Swelling of the abdomen (distention

Question 5

signs of strangulation

Answer 5

Clinical criteria such asfever, tachycardia, localized tenderness, and leukocytosismay be used as sign of strangulation.

Question 6

Mechanical Causes of Obstruction

Answer 6

Intussusception
Volvulus
Hernia
Adhesions

*** air fluid levels are sign on x-ray of obstruction!!!

Question 7

chagas disease associated with

Answer 7

megacolon

wipes out the ganglion cells in the colon

Question 8

Instussusception

Answer 8

defined:
as the invagination of one bowel segment into another (telescoping into a distal segment).

Most common cause of intestinal obstruction in children younger than two years of age

Most commonly between 5-9 months

Twice as frequent in males than females

Question 9

intussusception etiology

Answer 9

90% are idiopathic. 10% involve a discrete lead point

Associated with viral illness and rotavirus vaccine, possibly related to Peyer patch lymphoid hyperplasia

The telescoping can produce obstruction, ischemia, and eventual strangulation of the bowel

Common lead points include Meckel’s diverticulum, intestinal polyps, appendicitis, neoplastic lesions, and foreign bodies.

Question 10

Volvulus

Answer 10

Radiographic
“coffee bean” sign

Volvulus is most common in adults occuring with equal frequency in small intestine (around a twisted mesentery) and colon (in either sigmoid or cecum.
In very young children, volvulus almost always happens in the small intestine.

Question 11

External Inguinal Hernia

Answer 11

Protrusion of a serosa-lined pouch of peritoneum called a hernia sac.

Acquired hernias typically occur anteriorly, via the inguinal and femoral canals, umbilicus, or at sites of surgical scars

Obstruction usually occurs because of visceral protrusion into hernia sac.

Small bowel loops are typically involved.

With prolonged incarceration, get ischemia and obstruction and danger of perforation

Question 12

most common cause of intestinal obstruction in the United States.

Answer 12

adhesions

• Postoperative adhesions
• Inflammation
• Endometriosis

Question 13

Lower Gastrointestinal Bleeding

Answer 13

Lower GI tract bleedingrefers this to bleeding distal to the ligament of Treitz.

Colorectal causes are more prevalent than small intestinal causes.

Most common in the seventh decade

Chronic low-grade bleeding is often not visible to the patient
** (iron deficiency anemia)

Question 14

Common Causes of Lower Gastrointestinal Bleeding

Answer 14

Diverticulosis accounts for 30% to 40% of cases of significant lower GI hemorrhage

Angiodysplasia is a common cause of lower GI bleeding in elderly patients (acquired lesions associated with aging)

Question 15

Other Causes of Lower Gastrointestinal Bleeding

Answer 15

Inflammatory Bowel Disease

Anal fissure

Ischemia *** (watershed zones) > 70 yo

Infectious enteritis

Intestinal polyps

Cancer

Hemorrhoids

Question 16

Intestinal Vascular Disorders

Angiodysplasia

Answer 16

Non-neoplastic vascular lesion. Usually cecum or proximal right colon

Pathogenesis unknown

Tortuous dilatation of malformed submucosal and mucosal blood vessels

Accounts for * 20% of significant lower intestinal bleeding

Question 17

Ischemic Bowel Disease

Answer 17

Patients with acute mesenteric ischemia commonly present with * abdominal pain and hematochezia.

Paradoxically, elderly patients (who are the most prone to ischemia from arterial insufficiency) * often experience little or no pain until the disease is far advanced

• Watershed areas:
  Splenic flexure
  Recto-sigmoid junction

Question 18

Lower Gastrointestinal Ischemia: Arterial Insufficiency

Answer 18

vast majority

Nonocclusive mesenteric ischemia (* inadequate arterial blood flow)

• Systemic hypotension
• Shock
• Hypoxemia
• Dehydration

Occlusive ischemia (~70%) 
(obstruction to arterial blood flow)** 
- Atheromatous emboli (50%)
- Thrombus  (10%)
- Atherosclerosis
	 (mesenteric origin)
- Arteritis
- Dissecting aneurysm

Question 19

Lower Gastrointestinal Ischemia: venous insufficiency

Answer 19

Abdominal pain
Younger patients
External venous compression
Mesenteric venous thrombosis
Hypercoagulable states (genetic and acquired)

Question 20

Mechanical causes of ischemia

Answer 20

External compression

(volvulus, incarceration, adhesions)

Question 21

Normal Bowel

Vasculature

Answer 21

Extensive anastomosing arterial blood supply to the bowel make it more difficult to infarct

Question 22

Ischemic Bowel Disease

Answer 22

Small intestine and colon tolerate slowly progressive loss of blood supply

• Acute compromise of any major vessel can lead to infarction of several meters of intestine.
• • Superficial mucosal infarction extending no deeper than the muscularis mucosae
• • Transmural infarction involving all three wall layers

Question 23

Pathogenesis of Intestinal Ischemia

Answer 23

The initialhypoxic injuryoccurs at the onset of vascular compromise.

The second phase,reperfusion injury, is initiated by restoration of the blood supply and it is at this time that the greatest damage occurs.

Mechanisms of reperfusion injury:

• leakage of gut lumen bacterial products- lipopolysaccharide into the systemic circulation
• free radical production and neutrophil infiltration

Question 24

most common cause of intravascular occlusion.

Answer 24

Thrombi and emboli

Outcome of obstruction is
determined by size of affected artery and degree of collateral circulation.

Question 25

Diarrhea.

Answer 25

Normally, absorption and secretion take place simultaneously, but * absorption is quantitatively greater. Either a decrease in absorption or an increase in secretion leads to additional fluid within the lumen and thus Diarrhea. Disruption of epithelial electrolyte transport or its regulatory system by toxins, drugs, hormones, and cytokines is a major cause of diarrhea.

Question 26

Diarrhea | Classification

Answer 26

Increase of fecal water excretion of 100mL is the upper limit of normal - Watery diarrhea implies either * secretory or osmotic diarrhea. - Fatty diarrhea implies * defective absorption of fat and perhaps other nutrients in the small intestine. - Inflammatory diarrhea implies the presence of one of a limited number of inflammatory or neoplastic diseases involving the GI tract. * (purulent or bloody stools)

Question 27

Secretory diarrhea

Answer 27

persists during fasting | usually infectious; viral or enterotoxin

Question 28

Osmotic diarrhea

Answer 28

abates with fasting | classically lactase deficiency

Question 29

Exudative diarrhea

Answer 29

mucosal damage -> purulent, bloody stools persists during fasting usually bacterial or IBD

Question 30

Infectious Enterocolitis

Answer 30

Gastrointestinal infections are a major cause of morbidity and mortality worldwide  Most enteric infections are self-limited * Many infections of the gut are related to ingestion of fecal contaminated water or food or to foreign travel Enteric infection is the result of the interaction of host factors and microbial virulence factors

Question 31

Causes of Infectious Enterocolitis

Answer 31

Viral Bacterial Parasites Fungus Protozoa

Question 32

Enterocolitis Symptoms

Answer 32

Diarrhea (watery and/or bloody) Vomiting/Nausea Dehydration Fever Abdominal pain

Question 33

Pathogenesis of Bacterial Enteritis

Answer 33

Ingestion of * preformed bacterial toxins. (Staphylococcus aureus, Bacillus cereus, Clostridium botulinum, Clostridium perfringens) Non-invasive bacteria that * secrete toxins while adhering to the intestinal wall (Enterotoxigenic E.coli, Vibrio cholerae, Campylobacter jejuni) * Intracellular invasion of the intestinal epithelial cells. (Shigella, Salmonella) Bacteria that * enter the blood stream via the intestinal tract. (Salmonella typhi, Listeria monocytogenes)

Question 34

Staphylococcus Aureus

Answer 34

The gram positive cocci bacteria * produce enterotoxins while multiplying in food. Staphylococcal enterotoxins act as superantigens which induces diarrhea. Sensory stimulus is carried to the vomiting center in the brain by vagus and sympathetic nerves

Question 35

Vibrio cholerae

Answer 35

Most people exposed to V. cholerae are asymptomatic or develop only mild symptoms. Severe disease can lead to dehydration, hypotension shock and death in 24 hrs. ** Vibrio cholera produces multiple toxins that affect ion secretion and absorption resulting in increased Na and Cl ions in the lumen. Virulent Vibrio cholerae organisms attach to the brush border of epithelial cells

Question 36

Escherichia coli

Answer 36

Classified according to morphology, serotyping, mechanism of pathogenesis, and in vitro behavior. ``` Subgroups with major clinical relevance include: Enterotoxigenic E. coli (ETEC) Enteropathogenic E. coli (EPEC) Enterohemorrhagic E. coli (EHEC) Enteroinvasive E. coli (EIEC) Enteroaggregative E. coli (EAEC). ```

Question 37

Enterotoxigenic  E. Coli (ETEC)

Answer 37

* Noninvasive organisms cause non-bloody diarrhea Major cause of traveler's diarrhea Affects small intestine Produces secretory toxins (increase Cl secretion) that cause * non-inflammatory diarrhea

Question 38

Enteropathogenic E. coli (EPEC)

Answer 38

``` * Attaching and effacing mucosal lesions Non-invasive non-bloody diarrhea Infection of infants Affects small intestine Toxin also affects Na and Cl transport ```

Question 39

Enterohemorrhagic E. coli (EHEC)

Answer 39

E coli O157:H7 and non-O157:H7 serotypes Bloody diarrhea Produces a cytotoxin similar to that of Shigella * (Shiga like toxin) Use of antibiotics to treat EHEC appears to increase the risk for * hemolytic-uremic syndrome Cows are reservoir --> undercooked meat

Question 40

Enteroinvasive  E. coli (EIEC)

Answer 40

Do not produce toxins * Invade epithelial cells Similar to Shigella genetically  Produce a severe, dysentery-like illness as well as bacteremia * Young children in developing countries

Question 41

Enteroaggregative E. coli (EAEC)

Answer 41

Cause diarrhea in children and adults Causes of chronic diarrhea and wasting in AIDS patients Produce enterotoxins (Shigela-like) Non-bloody diarrhea

Question 42

Campylobacter jejuni

Answer 42

Most common enteric pathogen in developed world The gram negative curved bacillus is invasive but generally less so than Shigella. Campylobacter produces toxins similar to cholera. Associated with reactive arthritis in patients with HLA-B27 Guillain-Barre syndrome is post infection complication (1 in 2000 infections) Gastroenteritis is clinically indistinguishable from that caused by other enteric pathogens Faint Gram negative curved rods which may be gull-winged in shape. (arrows) This finding may provide presumptive evidence of Campylobacter infection prior to the results of stool culture

Question 43

Shigellosis

Answer 43

Shigella are resistant to the harsh acidic environment of the stomach Shiga toxin Stx, inhibits eukaryotic protein synthesis Virulent invasive organism causes blood diarrhea * Cause aphthous-appearing ulcers similar to those seen in Crohn disease.

Question 44

symptoms of shigellosis

Answer 44

Most prominent in left colon Most infections and deaths occur in children under 5years old Highly transmissible fecal oral route or contaminated water In endemic areas responsible for 75% of diarrheal deaths Incubation period one week with self limited disease diarrhea fever and abdominal pain

Question 45

Salmonella enteritidis 

Answer 45

Salmonella enteritidis  features are nonspecific and are similar to acute self-limited colitis  

Question 46

Salmonella typhi

Answer 46

causes typhoid fever can disseminate via lymphatic and blood vessels. - This causes reactive lymphoid hyperplasia in Peyer patches and lymphoid tissues throughout the body. 

Question 47

Non-typhoid salmonella (S. enteritidis)

Answer 47

Salmonellosis (food poisoning) Most infections are self-limited but can persist for weeks Antibiotic therapy not recommended can prolong carrier state and does not shorten diarrhea

Question 48

Yersinia

Answer 48

Y. enterocolitica strains are usually confined to the intestinal tract and lead to enteritis/diarrhea - Post-infectious complications include reactive arthritis with urethritis and conjunctivitis, myocarditis, erythema nodosum, and kidney disease. Y. pseudotuberculosis has symptoms of fever and abdominal pain mimicking appendicitis (actually from mesenteric lymphadenitis)

Question 49

Pseudomembranous Pattern

Answer 49

Clostridium difficile Shigella Enterohemorrhagic E. coli

Question 50

Granulomas

Answer 50

Yersinia sp. Mycobacterium Parasites and Fungus

Question 51

Macrophages

Answer 51

Whipple disease- Tropheryma whippelii

Question 52

Acute Self-Limited Colitis

Answer 52

Shigella Campylobacter jejuni Salmonella Clostridium difficile

Question 53

Architectural Distortion

Answer 53

Salmonella typhimurium | Shigella

Question 54

Pseudomembranous Colitis

Answer 54

Acute colitis characterized by formation of an adherent layer of inflammatory cells and debris overlying sites of mucosal injury --> pseudomembrane C. difficile overgrowth and toxin production following normal flora loss * (Antibiotic-Associated Colitis) Occurs primarily in adults as an acute diarrheal illness, can have chronic phase Diagnosis by detecting C. difficile cytotoxin in stool

Question 55

Norovirus

Answer 55

Most common cause of acute gastroenteritis requiring medical attention in US Second only to rotavirus as a cause of severe diarrhea in * infants and young children Local norovirus outbreaks are usually related to contaminated food or water, but person-to-person transmission underlies most sporadic cases. 

Question 56

Rotavirus

Answer 56

Rotavirus is a common cause of severe childhood diarrhea and diarrheal mortality worldwide. Rotavirus selectively infects and destroys mature enterocytes in the small intestine Loss of absorptive function and net secretion of water and electrolytes

Question 57

Adenovirus

Answer 57

Major cause of childhood diarrhea Important cause of diarrhea in immunocompromised patients Adenovirus is also one of the associated with ileal and * cecal intussusception in children

Question 58

Gastrointestinal Pathogens Associated with AIDS Diarrhea

Answer 58

Bacteria: Mycobacterium avium- intracellulare  Shigella  Salmonella Enteroaggregative E. coli  Clostridium difficile Viruses: Cytomegalovirus [CMV]  Herpes simplex Fungi:  Candida  Aspergillus Protozoa:  Cryptospordium  Toxoplasma  Giardia  Entameba histolytica  Microsporidia  Isopora belli Helminths:  Strongyloides  Enterobius

Question 59

ProtozoaCryptosporidium spp.

Answer 59

C. parvum was considered a very rare pathogen until AIDS epidemic. Important cause of diarrhea. Contaminated drinking water Most concentrated in terminal ileum and right colon.

Question 60

Parasitic Enterocolitis

Answer 60

Nematodes - * Ascaris, most common nematode (1 billion worldwide) - Strongyloides - Hookworm - * Pinworm, Whipworm Cestodes: - Fish and pork tapeworm - Hymenolepsis Trematodes - Schistosmiasis - Fasciola, Paragonimus Unicellular Parasites - * Entamoeba histolytica (ameba) - * Giardia lamblia - * Cryptosporidium spp.

Question 61

Places Where Kids Can Get Giardia

Answer 61

Giardiasis ( Giardia lamblia infection) is the leading GI protozoal disease in the United States The overall prevalence rate is 2% to 7% but reaches 35% in day care centers. Endoscopic examination is generally unremarkable, and small intestinal biopsies are often normal in appearance/mild villous blunting. Tissue invasion is not a feature of this infection.

Question 62

Giardia lamblia

Answer 62

Cysts are resistant forms and are responsible for transmission of giardiasis Both cysts and trophozoites can be found in the feces (diagnostic stages)

Question 63

Entamoeba histolytica

Answer 63

Dysentery causing protozoa that can also cause fulminant colitis Increased incidence in homosexual men and AIDS patients Amoeba invade colonic crypts, burrow into lamina propria, create flask shaped ulcer with broad base 40% invade portal vessels, embolize to liver and cause abscesses up to 10 cm Rare abscesses in liver, lung, heart, kidneys, brain

Question 64

Robbins Key Concepts infectious diarrhea

Answer 64

Vibrio cholerae secrete a preformed toxin that causes massive chloride secretion. Water follows the resulting osmotic gradient, leading to secretory diarrhea. Campylobacter jejuni is the most common bacterial enteric pathogen in developed countries and also causes traveler’s diarrhea. Most isolates are noninvasive. Salmonella and Shigella spp. are invasive and associated with and exudative bloody diarrhea (dysentery). Salmonella infection is a common cause of food poisoning. S. typhi can cause systemic disease (typhoid fever). Pseudomembranous colitis is often triggered by antibiotic therapy that allows colonization by Clostridium difficile. The organism releases toxins that disrupt epithelial function. The associated inflammatory response includes characteristic volcano-like eruptions of neutrophils from colonic crypts that spread to form mucopurulent pseudomembranes.

Question 65

Robbins key concepts viral and parasitic diarrhea

Answer 65

Norovirus is a very common cause of self limited diarrhea both in adults and children. It spreads from person to person in sporadic cases and by water in epidemic cases. Rotavirus is the most common cause of severe childhood diarrhea and diarrheal mortality worldwide. The diarrhea is caused by loss of mature enterocytes, resulting in malabsorption as well as secretion. Parasitic and protozoal infections affect more than one half of the world’s population on a chronic or recurrent basis. Each parasite has a distinctive life cycle and tissue reaction. Most are associated with tissue and systemic eosinophilia