Small and Large Intestine Flashcards
What histological features distinguish the duodenum? Jejunum? Ileum?
Duodenum - Brunner’s glands in the submucosa
Ileum - Peyer’s patches
Jejunum - neither
What is the function of Brunner’s glands?
Secrete mucus and HCO3- to neutralize acid coming into duodenum from stomach
What is the function of Peyer’s patches?
Large aggregates of lymphoid cells used for host defense
What is the function of Paneth cells?
Contain pink granules with lysozymes, defensins, and other things to aid digestion and help regulate microbiota of small intestine
Where in the GI tract are ganglion cells located?
Submucosa (Meissner’s/submucosal plexus)
Between the inner circular muscle and outer longitudinal muscle of the muscularis propria (Auerbach/myenteric plexus)
What is the main difference between gastroschisis and omphalocele?
Gastroschisis has exposure of abdominal contents without the peritoneum
Omphalocele has abdominal contents surrounded by the peritoneum and the amnion of the cord
What is intussusception?
Telescoping of one part of bowel into another (often part of small intestine inside large intestine)
Could cause obstruction of blood vessels and of the food bolus moving through intestines
What is volvulus?
Twisting of bowel around its mesentery, leading to obstruction and infarction
What is necrotizing enterocolitis?
Acute necrotizing inflammation of small and/or large intestines
Edema -> necrosis -> gangrenous bowel
Most common acquired GI emergency in premie or low birth weight neonate
Meckel Diverticulum
What is the pathologic issue?
Persistence of the vitelline duct
Meckel Diverticulum
Known as disease of 2’s because…
2% of population, mostly asymptomatic
2 inches long
Within 2 feet of ileocecal valve in small intestine
2:1 M:F ratio
2 major complications:
Pain with inflammation
Hemorrhage with ulcer
Hirschsprung Disease
What is the basic pathologic issue?
Absence of ganglion cells
Death of neural crest cells from cecum to rectum
Hirschsprung Disease
How is it diagnosed?
Suction biopsy needed to get a biopsy deep enough to include submucosa and muscularis propria
Hirschsprung Disease
What do you expect to see on histology?
Lack of ganglion cells in the myenteric plexus
Hirschsprung Disease
Treatment
Resection of the portion of bowel without the neurons
What are some general symptoms of malabsorption?
Chronic diarrhea
Weight loss
Abdominal pain
No villi -> steatorrhea
What are some signs of pancreatic insufficiency?
Increased neutral fat
Normal D-xylose absorption test (urinary excretion)
Disaccharidase Deficiency
What is the most common deficiency?
Lactase deficiency (Lactose intolerance)
What happens when a person with lactose intolerance eats lactose?
Due to lack of lactase enzyme, the intestines cannot digest lactose. Lactose remains in intestinal lumen, pulling water into the lumen via osmotic forces and causing an osmotic diarrhea
Abetalipoproteinemia
What is the basic issue?
Low synthesis of apolipoprotein B, which is required for chylomicron generation
Results in decreased secretion of cholesterol and fat accumulation in enterocytes
Presents as failure to thrive in early childhood
Celiac Disease
What is the basic issue?
Autoimmune disorder resulting in damage to small intestine lining when foods containing gluten are eaten
Celiac Disease
Diagnosis
Serum test
Look for IgA/IgG to tissue transglutaminase (tTG), deaminated gliadin, HLA DQ2 or DQ8
Biopsy
Look for increased intraepithelial lymphocytes and flattening of the villi
Celiac Disease
Clinical Features in Infants
Diarrhea Failure to thrive Abdominal distension Anorexia Weight loss Irritability
Celiac Disease
Clinical Features in Older Children and Adults
Abdominal pain
Nausea
Vomiting
Bloating/Constipation
Diarrhea Flatulence Weight loss Anemia Fatigue
Celiac Disease
Describe Dermatitis Herpetiformis
Skin blistering disease caused by IgA deposition in the dermal papillae
Can cause obstruction of blood vessels in dermis, causing epidermis to separate and blister
Tropical Sprue
What is it caused by? Where? How to treat?
Similar findings to celiac disease, caused by an unknown infectious agent
Seen in Caribbean
Treat with antibiotics
Bacterial Infectious Enterocolitis
What is seen on histology?
Acute inflammation of the colon with many PMNs in the epithelium and lamina propria
List two common viral causes of enterocolitis
Noravirus
Rotavirus
List the two common protozoan causes of enterocolitis
Giardia - commonly from drinking freshwater streams
Entamoeba Histolytica - causes flash shaped ulcer on histology
Pseudomembranous Colitis
What often precedes the development of this disease?
Course of broad spectrum ABX
Pseudomembranous Colitis
Gross appearance of colon
Yellow-green false membrane of mucus and PMNs
See mushroom shaped pseudomembrane on histology
What organism is associated with Pseudomembranous Colitis?
Clostridium difficile
Collagenous Colitis
Who commonly gets this? What is the main symptom?
Middle aged females with watery diarrhea
Collagenous Colitis
What is seen histologically?
Lymphocytes in the epithelium
Subepithelial deposition of collagen
Lymphocytic Colitis
What is the primary symptom? What is seen histologically?
Chronic watery diarrhea
Intraepithelial lymphocytes are present, but there is no subepithelial collagen
Whipple Disease
Describe the basic pathogenesis
Organism: Tropheryma whippleli
Macrophages engulf the organism, distend the villi, congest blood vessels and lymphatics
May cause enterocyte necrosis or poor absorption
What are two main types of IBD?
Crohn’s Disease
Ulcerative Colitis
Crohn’s Disease
Symptoms
Diarrhea (non-bloody)
Cramping abdominal pain (RLQ)
Low grade fever
Asymptomatic periods (skip periods) with recurrent attacks or flare ups
Crohn’s Disease
Complications and extra-intestinal manifestations
Erythema nodosum (subcutaneous nodules on lower extremities)
Pyoderma gangrenosum
Uveitis
Kidney stones
Crohn’s Disease
Gross appearance
Fissure moving through entire wall into the muscularis propria and serosa
Narrowing of lumen (stricture)
Crohn’s Disease
Histology
Non caseating granulomas
Transmural inflammation
See many PMNs in the crypt
Ulcerative Colitis
Symptoms
Bloody diarrhea
Recurring with asymptomatic intervals
Ulcerative Colitis
Complications
Primary sclerosing cholangitis
Ulcerative Colitis
Pathogenesis
Inflammation involving only the colon, spreading up from rectum through colon.
Pseudopolyps are seen grossly (normal areas surrounded by ulcerated areas)
Ulcerative Colitis
Histology
Crypts filled with PMNs is primary feature
More superficial process than Crohn’s – Ulcerative Colitis only involves the mucosa and submucosa
Crohn’s vs. Ulcerative Colitis
Which is continuous?
Ulcerative colitis involves rectum and colon continuously
Crohn’s has skip areas
Crohn’s vs. Ulcerative Colitis
Which involves the full thickness of the wall?
Crohn’s is transmural
Ulcerative Colitis is only mucosa and submucosa
Crohn’s vs. Ulcerative Colitis
What are the extraintestinal involvements of each?
Crohn’s - migratory polyarthritis and kidney stones
Ulcerative Colitis - Primary sclerosing cholangitis
Diverticulum
Where are they most common?
Sigmoid colon
Diverticulum
Difference between true and false diverticula
True - involving mucosa, submucosa, and muscularis propria
False- involving mucosa and submucosa only
Diverticulum
How does diverticulitis develop?
Diverticulum is a blind outpouching of the colon where fecal matter can get stuck, cause inflammation, thus causing diverticulitis
Where are direct hernias found? What about above and below those?
Hasselbach’s triangle
Above - indirect
Below- Femoral
Ischemic Bowel Disease
Symptoms
Severe abdominal pain Tenderness Bloody diarrhea Melena Could lead to sepsis, shock, death
Ischemic Bowel Disease
What is the watershed zone?
Splenic flexure
Area furthest away from blood supply, so it is at higher risk for ischemia
Ischemic Bowel Disease
Pathogenesis
Something causes hypoxic or reperfusion injury to the colon
Athersclerosis, AAA, hypercoagulable state, oral contraceptives, embolization, cardiac failure, shock, dehydration, vasoconstrictive drugs, vasculitis
What are Hemorrhoids?
Anal varices
Dilated anal and perianal collateral vessels
Causes pain and some abdominal bleeding
What is the difference between internal and external hemorrhoids?
Internal - above pectinate line; receive visceral innervation and are NOT painful
External- below pectinate line; receive somatic innervation and are painful
Inflammatory Polyp
What syndrome is it associated with?
Solitary Rectal Ulcer Syndrome
Hamatomatous Polyp
What syndrome is it associated with?
Peutz-Jeghers syndrome
Peutz-Jeghers Syndrome
What is the inheritance? What are the symptoms?
Autosomal dominant
Hyperpigmented melanotic macules of mouth, lips, genitals, hands
Peutz-Jeghers syndrome
What are patients at risk for?
Polyps themselves are not malignant, but there is increased risk of CRC and other malignancies (pancreas, breast, lung, ovary, uterus, testes)
Hyperplastic Polyp
What is the appearance on histology?
Proliferation of mature goblet cells
Serrated/sawtooth appearance of goblet cells stacking on one another
Adenomatous Polyp
What are the two broad classifications of it’s gross appearance? Which is more dangerous?
Pedunculated (on a stalk)
Sessile (growing directly out of intestinal wall)
Sessile is more dangerous
Adenomatous Polyp
Tubular vs. Villous appearance - Which is more dangerous?
Villous is more likely to grow into an adenocarcinoma
Sessile Serrated Adenoma
Where do they mostly occur?
Adenomatous polyp in the RIGHT colon
Sawlike serrated areas
Familial Adenomatous Polyposis
What is the inheritance? How is it treated?
Autosomal dominant
Defect in APC gene on chromosome 5
Treated with prophylactic colectomy for APC mutations
Gardner Syndrome
What are the symptoms?
Polyps similar to FAP
Osteomas of mandible, skull
Fibromatosis- non-neoplastic fibroblast proliferation
Turcots Syndrome
What are the symptoms?
FAP with CNS tumors
Medulloblastomas
Glioblastomas
HNPCC
What is the defect? Inheritance?
Autosomal dominant defect in DNA mismatch repair, leading to increased risk of many cancers
Describe the function of the APC gene product. What happens when it is knocked out?
APC binds beta-catenin and prevents it from activating transcription of many tumor promoting genes.
When APC is knocked out (2 hits needed), Beta-catenin is free to activate transcription of MYC, cyclin D1, others to promote tumors
DNA mismatch repair defects are seen (mostly) in what disorders?
HNPCC and sessile serrated adenomas
APC mutations are seen mostly in what disorders?
FAP or sporadic CRC
DNA mismatch repair defects may be caused in mutations in what genes?
MLH1 MSH2 MSH6 PMS1 PMS2
Colon Cancer
How will it appear on imaging?
Apple core lesion on barium X ray because tumor is compressing and narrowing lumen
Colon Cancer
How are the shapes of R sided and L sided colon cancers different?
R sided - tumor grows on one side of lumen and obstructs (exophytic tumor)
L sided - “Napkin ring” lesion that causes obstructive symptoms much more quickly
Which side of the colon has a larger diameter?
Right, so R sided colon tumors take longer to cause obstruction
What are the general presenting symptoms of R and L sided colon cancers?
R sided - iron deficiency anemia
L sided - obstruction
What types of cancers are likely to be seen in the rectum and anus?
Rectum = adenocarcinoma
Anus = squamous cell carcinoma
List the stages of colon cancer progression
T is – intraepithelial or lamina propria
T1- submucosa
T2- muscularis externa
T3- serosa
T4- peritoneum, other organs, perforation
Appendicitis
Symptoms
Nausea/vomting
Periumbilical pain localizing to RLQ
Obstruction leading to impaired blood flow and bacterial contamination
Appendicitis
Gross appearance
Appendix is enlarged with yellow-green exudate (pus)
Appendicitis
Histology
Transmural inflammation
Lots of PMNs and eosinophils
