Chapter 17 - SI And Colon; Peritoneal Cavity

Question 1

What are the most common causes of intestinal obstruction?

Answer 1

Hernias, adhesions, volvulus, intussusception

Question 2

What are sx of bowel obstruction?

Answer 2

Abdominal pain, Distention (tympanic), vomiting, constipation/obstipation, sx of ischemic bowel

Question 3

What is the most common cause of obstruction worldwide? Describe it

Answer 3

Hernia: part of an organ is displaced and protrudes through the wall of the cavity containing it
Acquired and congenital types
Complications: obstruction, incarceration (entrapment), strangulation (blood compromise)

Question 4

What is the most common cause of obstruction in the US? Describe them

Answer 4

Adhesions: fibrous bands/bridges btwn bowel segments, abdominal wall, or operative site
Etiology: surgical procedures, infection, or other causes of peritoneal inflammation, such as endometriosis
Same complications as hernia

Question 5

What is volvulus?

Answer 5

Twisting of a loop of bowel about its mesenteric point of attachment
Luminal and vascular compromise -> obstruction and infarction
Rare!
Sigmoid colon MC
Lots of tympanic sounds and distention in question stem

Question 6

What is the most common cause of intestinal obstruction in children younger than 2? Describe it

Answer 6

Intussusception: inversion of one portion of the intestine w/i another
Idiopathic or after viral infection/rotavirus vaccine peds; mass or tumor in adults
Dx and Rx: barium enema

Question 7

What are the causes of acute obstruction to flow leading to ischemic bowel disease?

Answer 7

Severe atherosclerosis (ostium)
AAA
Embolization (cardiac valves/atheroma)
Hypercoagulation
Mesenteric thrombosis 
OCP

Question 8

What are the chronic/hypoperfusion states that results in Ischemic bowel disease?

Answer 8

Cardiac failure 
Shock
Dehydration
Drugs (cocaine, vasoconstrictors)
Vasculitides

Question 9

What are the three major variables of the pathogenesis of ischemic bowel disease? What causes the majority of the damage?

Answer 9

Severity of vascular compromise
Duration
Vessels affected
Majority of damage: reperfusion injury-> leakage gut lumen bacterial products, inflammatory mediators into systemic circulation

Question 10

What is the clinical setting and presentation of Ischemic bowel disease? What is the Rx?

Answer 10

Ischemic colitis most common
>70, slightly > F
Fq seen co-existing cardiac and/or vascular disease
Acute obstruction->s/o of cramping LEFT lower abdominal pain, desire to defecate, passage of blood
Rx: surgery if decreased bowel sounds (paralytic ileum), guarding or rebound tenderness

Question 11

What is the outcome of Ischemic bowel disease?

Answer 11

Mucosal and non transmural infarcts may not be fatal
Transmural-> 10% mortality first 30 days
Superior mesenteric occlusion worse outcome - supplies both right side colon and much of SI (right sided more severe course)
Coexisting COPD - poor prognosis

Question 12

What is the most common site of GI ischemia?

Answer 12

Colon

Question 13

What is angiodysplasia?

Answer 13

Tortuous, ecstatic dilations of mucosal or submucosal veins 
1% of pop 
Right colon 
After age 60
20% of major lower GI bleeds

Question 14

How does malabsorption most commonly presents? How is it characterized?

Answer 14

Presents s chronic diarrhea
Characterized by defective absorption of fats, fat and water soluble vitamins, proteins, carbs, electrolytes and minerals, and water

Question 15

What are the S/Sx of malabsorption ?

Answer 15

Chronic diarrhea, flatus, abd pain, borborygmi, anorexia and WL, mm wasting
Hallmark of malabsorption is steatorrhea: excessive feat fat and bulky, frothy, greasy, yellow or clay-colored stools

Question 16

Describe the symptoms of vitamin deficiency:
Vit B, A, D
Ca and Mg

Answer 16

B6 (pyridoxine), folate, B12 - anemia and muscositis
Vit K - bleeding
Ca, Mg, Vit D - osteopenia and tetany
A, B12 (cobalamin) - peripheral neuropathy

Question 17

What are the most commonly encountered chronic malabsorptive disorders in the US?

Answer 17

Pancreatic insufficiency
Celiac disease
Crohn disease

Question 18

What is diarrhea? What are the classifications

Answer 18

Increase stool mass, fq, or fluidity, typically greater than 200 g/day
Secretory: isotonic stool
Osmotic: d/t excessive osmotic forces
Malabsorptive: steatorrhea
Exudative: inflammatory disease, purulent, bloody stools

Question 19

How does Cystic fibrosis involve the GI tract?

Answer 19

Absence of CFTR->defective luminal hydration->intestinal obstruction
Pancreatic duct obstruction->low-grade chronic autodigestion of pancreas, eventual exocrine pancreatic insufficiency in majority
Failure of intraluminal phase of nutrient absorption**: Rx oral enzyme supplement

Question 20

What is celiac disease? How common is it?

Answer 20

Spruce, celiac spruce, gluten sensitive enteropathy
Immune-mediated enteropathy via gluten (gliadin) (wheat, rye, barley)
Association with other autoimmune diseases
Increased intraepithelial CD8+ T cell #s
1% of population: Class II HLA-DQ2, DQ8

Question 21

What are the clinical features of celiac disease?

Answer 21

Adults: 30-60s, >F, Classic and atypical
Adults Sx: chronic diarrhea, bloating, chronic fatigue, malabsorption, or asymptomatic
Children: M=F
Infant Sx: irritability, abd distension, chronic diarrhea, FTT, WL, mm loss
Child: abd pain, N/V, bloating, constipation
10% of pts with blistering skin disorder: dermatitis herpetiformis

Question 22

What is the most sensitive diagnosis for Celiac disease and what is the treatment? What may have occurred if Sx return?

Answer 22

IgA tTG abs or IgG to deamidated gliadin
Change of diet - gluten free
Sx return: fell off diet or malignancy: adenocarcinoma or enteropathy-associated T lymphoma (EALT)

Question 23

Environmental enteropathy pearls

Answer 23

Setting: areas of poor sanitation - parts of Africa, South America, Asia; areas of impoverished communities - Brazil, Guatemala, India, Pakistan
No Dx criteria
Cause unknown
Global impact - esp children: diarrhea, defects in physical and cognitive development
Terminal digestion and transepithelial transport defects

Question 24

Autoimmune enteropathy pearls

Answer 24

Terminal digestion and Transepitheial transport defects
Rare, X-linked
MC children: persistent diarrhea and autoimmune disease
Severe IPEX form d/t FOXP3 TF of CD4+ T reg cell mutation
Autoabs - enterocytes, goblet cells, parietal cells, islet cells

Question 25

Lactase deficiency pearls

Answer 25

Congenital - rare, autosomal recessive Explosive watery diarrhea frothy stools Abdominal distention upon milk ingestion Acquired - down-reg lactose gene Native A, AA, and Chinese Follows Enteric viral and bacterial infections terminal digestion defects

Question 26

Abetlipoproteinemia pearls

Answer 26

``` Transepitheial transport defects Rare autosomal recessive Inability to process and secrete TG-rich lipoproteins MTP mutation Presents in infancy -> FTT, steatorrhea Dx: acanthocytic red cells: burr cells Intracellular lipid accumulation ```

Question 27

Infectious enterocolitis - Cholera

Answer 27

Vibrio cholera: comma-shaped, gram-negative bacteria India, Africa, Gulf of Mexico (shellfish) Fecal-oral (drinking water) Rice Water stools - severe watery diarrhea Small Intestines Toxin A: Gs pathway ->Surge of cAMP opens CFTR

Question 28

Infectious Enterocolitis: Campylobacter

Answer 28

Campylobacter spp: comma-shaped, flagellated, gran-negative C. Jejuni - MC enteric pathogen in developed countries Important cause of traveler's diarrhea (food poisoning - chicken, milk, water) Erythema nodosum, HLA-B27 and reactive arthritis, Guillain-Barre syndrome (abs cross react with gangliosides) Bloody or watery diarrhea Colon

Question 29

Infectious Enterocolitis: Shigellosis

Answer 29

Gram-negative unencapsulated, nonmotile, facultative anaerobes, enterobacteriaceae fam: closely related to E.coli Lactose nonfermenter Humans - reservoir: daycare centers, migrant workers, travelers to developing countries, nursing homes one of MC causes of bloody diarrhea worldwide Fecal-oral low dose Self limited: prominent in left colon, ileum may be involved Sterile reactive arthritis, urethritis, conjuctivitis (HLA-B27-positive men 20-40 YOA) Bloody diarrhea

Question 30

Infectious Enterocolitis: Salmonella non-typhoid type

Answer 30

``` Enterobacteriaceae family G - bacilli, Lactose nonfermenter, S. Enteriditis Young children, elderly Contaminated food Stool cultures to ID Loose stools to cholera-like diarrhea to dysentery Usually self-limited: sepsis, abscess At risk: malignancies, immunosuppresssion, alcoholism, cardiovascular dysfunction, Sickle cell disease, hemolytic anemia Colon and Si ```

Question 31

Infectious Enterocolitis: Salmonella typhoid type

Answer 31

G - bacteria Salmonella enterica: subtypes typhoid (endemic countries kids) and paratyphi (travelers) India, mexico, philippines, pakistan, el salvador, haiti Gall bladder stones Peyer patches in terminal ileum Anorexia, abd pain, bloating, N/V, bloody diarrhea Short asymptomatic phase Bacteremia, fever, flulike sx, Pain mimic appendicitis Encephalopathy, meningitis, seizures, endocarditis, myocarditis, pneumonia, cholecystitis Liver - typhoid nodules Disseminate vial lymphatics and blood vessels SI

Question 32

Infectious Enterocolitis: Yersinia

Answer 32

Yersinia Enterocolitis a and pseudotuberculosis: G-, lactose nonfermenter Ileum, Appendix, right colon Europe Reservoir: pigs, cows Abdominal pain, fever, diarrhea, mimic appendicitis Reactive arthritis, erythema nodosum

Question 33

E. coli microbiology

Answer 33

Gram - bacilli Healthy GI tract Lactose fermenter, fast = McConkees agar

Question 34

ETEC

Answer 34

``` Enterotoxigenic E coli MC of travelers diarrhea Toxins: Heat-labile (cAMP), Heat-stable (cGMP) - both block intestinal fluid absorption Infants, adolescents, travelers Severe watery diarrhea SI ```

Question 35

EPEC

Answer 35

``` Enteropathogenic E coli Pediatric A/E lesions Effacement of microvilli Watery diarrhea SI ```

Question 36

EHEC

Answer 36

``` Enterohemorrhagic E coli O157:H7 and non-O157:H7 Shigalike toxin Contaminated milk and veggies Cows natural reservoir Hemolytic-Uremic syndrome - anemia, thrombocytopenia, RF Bloody diarrhea Colon ```

Question 37

EIEC

Answer 37

``` Enteroinvasive E coli Similar to Shigella but no toxin Food, water, p2p transmission MC in children Colon Bloody diarrhea ```

Question 38

EAEC

Answer 38

``` Enteroaggregative E coli Children Colon Nonbloody diarrhea Produce shigalike toxin ```

Question 39

Pseudomembranous colitis pearls

Answer 39

C diff Pathognomonic Lamina propria has dense infiltrate of neutro, surface epithelium denuded Eruption, volcano crypts - exudates coalesce = pseudomembranes RF: age, hospitalization, antibiotics CF: fever, leukocytosis, abdominal pain, cramps, watery diarrhea, dehydration

Question 40

Wipple disease pearls

Answer 40

Rare Caucasian male farmers Soil/animals Gram + actinomycete: Tropheryma wippelii Diarrhea, WL, malabsorption The only cause of malabsorption due to lymphatic transport Laden Mo in LNs, joints and brain

Question 41

Most common cause of viral gastroenteritis outbreaks? Describe the virus and key features

Answer 41

Norovirus: small icosahedral viruses with ssRNA; caliciviridae Most common cause of acute gastroenteritis requiring medical attention Contaminated food and water, P2P MC Immunocompetent: self limited watery diarrhea Spreads on school, cruise Immunocompromised: airborne

Question 42

What is the most common cause of severe childhood diarrhea? Describe the virus and clinical features

Answer 42

``` Rotavirus: encapsulated segmented dsRNA 6-24 mo Low dose for infection Daycare/hospital common Damage to enterocytes NSP-4 Vomiting, watery diarrhea Vaccine associated w/ intussusception ```

Question 43

What is the second MC cause of pediatric diarrhea? Details

Answer 43

Adenovirus SI epithelial degeneration Nonspecific villa us atrophy Self limited diarrhea, vomiting, abd pain

Question 44

Enterobius vermicularis

Answer 44

``` Enterobiasis, Parasitic enterocolitis Pinworms Migrate anus at night, lay eggs -> rectal and perineal pruritis Scotch tape test Fecal oral Do not invade host tissues No serious illness ```

Question 45

Giardia lamblia

Answer 45

Parasitic enterocolitis Most common parasitic pathogen in humans Unfiltered public water, campers, swimming Decrease lactase Trophozoites ID in duodenal biopsies - pear shape and 2 equal sized nuclei Immunofluorescent detection of cysts in stool samples Damage microvilli brush border IgA and IL-6 for clearance

Question 46

What is IBS? Who is it most prevalent in? And what are the clinical features?

Answer 46

Chronic, relapsing abdominal pain, bloating, and changes in bowel habits Females 20-40 CF: Dx using clinical criteria that require the occurrence of abdominal pain/discomfort for at least 3 days per month over 3 months w improvement after defecation and change in stool fq or form No pathologic abnormality* Rome III criteria diagnosis

Question 47

What is Inflammatory bowel syndrome ?

Answer 47

Chronic condition related to inappropriate mucosal immune activation: Crohn disease or ulcerative colitis

Question 48

What is the epidemiology of IBD?

Answer 48

Presents teens/early 20's More common in Caucasians and Ashkenazi jews Developed countries

Question 49

What is the pathogenesis of IBD?

Answer 49

Results from the combined effects of alterations in host interactions with intestinal micfrobiota, intestinal epithelial dysfunction, aberrant mucosal immune responses, and altered composition of the gut microbiome Genetics: More common in twins TNF - increase Tight jxn permeability

Question 50

Describe the Key features of Crohn disease

Answer 50

``` MC in Small intestine, can include colon Skip lesions Transmural inflammation ->creeping mesenteric fat, strictures, perforation, and perianal fistula Aphthous ulcers - deep Fissure formation Cobblestone appearance Non-caseating granulomas Abs - Sacccharomyces cerevisiae Wall - thick and rubbery Abundant neutrophils Recurrence after surgery Malignant potential with colonic involvement ```

Question 51

What are the symptoms of Crohn disease? Potential therapy?

Answer 51

Variable RLQ pain, fever, bloody diarrhea - mimic acute appendicitis or bowel perforation Malabsorption and malnutrition, vit B12 deficiency Extra-intestinal manifestations - Erythema nodosum, clubbing of fingertips, iron deficiency anemia, uveitis, migratory polyarthritis, sacroiliitis, ankylosing spondylitis Reactivation from emotional stress, smoking Anti-TNF abs - therapy option

Question 52

Describe key features of Ulcerative colitis

Answer 52

``` Colon only - always involves rectum Slightly more common in females Diffuse No strictures Wall - thin, pseudopolyps and mucosal bridges Mucosal inflammation Ulcers - superficial, broad based No recurrence after surgery Crypt abscesses Toxic megacolon Malignant potential: higher if pancolitis P-ANCA ```

Question 53

What are the clinical features of Ulcerative colitis

Answer 53

Pt at greatest risk for developing Primary sclerosing cholangitis Relapsing disorder: bloody diarrhea, stringy, mucous material. Lower abdominal pain and cramps relieved by defecation Triggers - infectious enteritis, psychological stress, some d/t smoking CESSATION Extra-intest: migratory polyarthritis, sacroiliitis, ankylosing spondylitis, uveitis, and skin lesions - same as Crohn

Question 54

What are the three factors of neoplasia in IBD?

Answer 54

Duration of disease: increases after 8 years Extent of disease: pancolitis greater risk Nature of the inflammatory response: Increase w severity and duration of active inflammation

Question 55

What is indeterminate type colitis

Answer 55

Does not involve small bowel, Colonic disease in continuous pattern - maybe ulcerative colitis BUT - key features of CD: fissures, patchy, FH of CD, perianal lesions, onset after initiating use of cigarettes

Question 56

How is IBD monitored?

Answer 56

Surveillance biopsies 8 years after dx High grade - colectomy Low grade - colectomy or surveillance depending on age and # of foci

Question 57

What is diversion colitis? What is the treatment?

Answer 57

Creating of blind distal colonic pouch following intestinal surgery Colitis d/t change in microbiome or irritation from diverted fecal stream Histo: look like IBD - crypt abscesses, mucosal distortion, rarely granulomas Rx: enemas w SCFA from bacterial digestion

Question 58

What is microscopic colitis

Answer 58

Middle-aged women, chronic watery diarrhea w abd pain Endoscopic findings grossly normal Two forms: Collagenous: intraepithelial lymphocytes and a dense subepithelial collagen band Lymphocytic: intraepithelial lymphocytes without bandlike collagen

Question 59

Key features of GVHD

Answer 59

Hx of hematopoietic stem cell transplant Epithelial apoptosis Watery diarrhea that may become bloody in severe cases

Question 60

What is diverticular disease? Who is it most prevalent in?

Answer 60

Acquired pseudo-diverticulum outpouchings of the colonic mucosa Prevalence - common after age 60, western population; low fiber diets - MC in sigmoid (most weak point) Right sided in Africa and Asia Pathogenesis: unique structure of the colonic muscularis propria and elevated intraluminal pressure in the sigmoid colon

Question 61

What are the clinical features of Diverticular disease?

Answer 61

Symptomatic in about 20%: intermittent cramping, continuous lower abdominal discomfort, constipation, distention, or a sensation of never being able to completely empty the rectum Symptoms can mimic IBS Rare blood loss or hemorrhage Obstruction of diverticula leads to diverticulitis->possible performation

Question 62

What is the most common polyp in the GI tract?

Answer 62

Hyperplastic polyp

Question 63

Key features of hyperplastic polyp

Answer 63

``` Nonneoplastic - no malignant potential MC Left colon Single or multiple 6-7th decade Less than 5 mm Histo: epithelial crowding produces serrated architecture when crypts are cut in x-section ```

Question 64

Key features of inflammatory polyp

Answer 64

Non neoplastic Part of solitary rectal ulcer syndrome (SRUS) Triad: rectal bleeding, mucus discharge, anterior rectal wall location

Question 65

What is a hamartomatous?

Answer 65

Non neoplastic polyp Recognized to be syndrome associated with germline mutations in tumor suppressor genes or protooncogenes Syndromes associated with cancer, extra-intestinal manifestations Juvenile polyps and Peutz-Jeghers syndrome

Question 66

Key features of Juvenile polyps (retention polyps)

Answer 66

Focal hamartomatous malformations of SI and colon mucosa < 5 YOA Sporadic or syndromic Rectal location Syndrome: rare autosomal dominant disorder: 100 hamartomatous polyps, SMAD4, Pulmonary arteriovenous malforamtions, Increassed risk of bowel malignancy (adenocarcinoma by age 45, 50%) Congenital malformations, digital clubbing

Question 67

Peutz-Jeghers syndrome key features

Answer 67

Rare AD syndrome Age 11 Multiple GI harmartomatous polyps Mucoccutaneous hyperpigmentation: dark blue to brown macules on lips, nostrils, buccal mucosa, palmar surfaces of the hands, genitalia, and perianal regions Multiple polyps->intussusception in SI LOF mutations in STK11/LKB1 Lifetime risk of malignancies in multiple organs (SI>colon>stomach adenocarcinoma; breast, lung, pancreatic cancer) Complex glandular architecture and presence of smooth muscle

Question 68

What are colonic adenomas?

Answer 68

Benign polyp precursors to the majority of colorectal carcinomas Most do NOT progress to malignancy Risk of malignancy correlated to size and severity of dysplasia Intraepithelial neoplasms that range from small, often pedunculated polyps to large sessile lesions 30% by age 60 Males >

Question 69

What is the hallmark of epithelial dysplasia?

Answer 69

Nuclear hyperchromasia, elongation, and stratification

Question 70

FAP key features

Answer 70

Autosomal dominant 100-1000 colorectal adenomatous polyps as teenager APC gene Risk of cancer 100%***** often before age 30, always by 50 Classic: congenital hypertrophy of retinal pigment epithelium, age 10-15 Attenuated: 40-50 YOA Gardner: 10-15 YOA, osteomalacia, thyroid and Desmond tumors, skin cysts Turbot: 10-15 YOA - medulloblastoma, glioblastoma

Question 71

HNPCC key features

Answer 71

``` Lynch syndrome 2-4% of all colorectal cancer MC syndromic form Earlier age RIGHT SIDED location Family history MMR and MSI molecular defects Genes: MSH2, MLH1 ```

Question 72

What should be considered in pts 65 and older or postmenopausal women with unexplained iron loss?

Answer 72

Colonic adenocarcinoma - MC GI malignancy

Question 73

Key features of colonic adenocarcinoma

Answer 73

60-70 YOA, North America, low veggies, high CHO's, high fat Methylation-induced epigenetic event Classic: APC/B-catering pathway->activated MYC and cyclin D1, Left sided, annular lesions - napkin ring constrictions MMR: right sided - polyploid, exophytic masses, MSI high

Question 74

Clinical features of right-sided colon adenocarcinoma

Answer 74

Fatigue, weakness d/t iron deficiency anemia | Fe Def anemia older man/postmen woman = GI cancer

Question 75

Clinical features of left sided colorectal adenocarcinoma

Answer 75

Occult bleeding, changes in bowel habits,, or cramping and left lower quadrant discomfort

Question 76

What are the two most important prognostic factors of colon adenocarcinoma?

Answer 76

Depth of invasion and the presence of LN metastases | Metastasis: regional LN, lungs, bones, LIVER MC

Question 77

Describe carcinomas of the anal canal

Answer 77

May have typical glandular or squamous, or basaloidpatterns of differentiation Pure squamous cell carcinoma is fq associated with HPV infections (HIV related) which also causes precursor lesions such as condylomata acuminatum

Question 78

What are the risk factors and cause of Hemorrhoids? Clinical presentation?

Answer 78

RF: straining at defecation bc of constipation, and venous stasis of pregnancy, and cirrhosis (portal HTN) Secondary to persistently elevated venous pressure within the Hemorrhoidal plexus - varices dilations Presentation: pain and rectal bleeding, bright red blood on toilet tissue, Rarely <30 y/o except pregnancy

Question 79

Key features of acute appendicitis

Answer 79

MC acute abdominal condition requiring surgery MC adolescents and young adults, M>F Most associated with obstruction d/t small mass of stool (fecalith), tumor, worms -> stasis and favorable bacterial proliferation/ischemia/inflammation McBurney sign Morph: neutrophilic infiltration of muscularis propria

Question 80

What is the MC tumor of the appendix?

Answer 80

Carcinoid - neuroendocrine tumor w solid bulbous swelling distal top of appendix

Question 81

Describe primary tumors of the peritoneum

Answer 81

Rare Mesothelioma: asbestos exposure Desmoplastic small round cell tumor: translocation (11,22) Ewing sarcoma and Wilms tumor Most are malignant

Question 82

Describe secondary tumors of Peritoneum

Answer 82

Most are malignant More common than primary MC: ovarian and pancreatic adenocarcinomas