Large intestine Flashcards
Down’s GI problems
“Don’t have a clue”
Duodendal atresia
Hirschsprung disease
annular pancreas
celiac disease
Hirschsprung disease
failed migration of neural crest cells –> congenital megacolon d/t dysfunctional Auerbach and Meissner plexus in distal colon
Impaired peristaltic waves –> no fecal expulsion
Meconium ileus
Less severe: chronic constipation, abdominal distention early in life
Down syndrome - high risk
Volvulus
twisting of colon around mesentery
-cecum or sigmoid colon
cut off blood flow –> ischemia
elderly, men
slowly progressive abd pain w/ signs of intestinal obstruction (constipation, n/v)
Abd exam: distended, tympanic abdomen, tender to palpation
Abd CT to confirm: distended loops proximal to volvulus, whirled pattern
XR: double bubble - proximal and distal to volvulus
Tx: detorsion w/ sigmoidoscopy
surgery to permanently resolve
resect dead bowel w/ reanastamosis
Appendicitis
Inflammation secondary to obstruction
Adults: fecal lith - obstructing fecal stone
Kids: viral infections –> hyperplasia of lymphoid tissue, obstructs appendix (houses MALT)
N/V
diffuse periumbilical pain
later pain locates to RLQ - McBurney’s point
Fever late in course
Rebound tenderness = peritonitis
Psoas sign - passive hip extension = RLQ pain
Rovsing’s sign - LLQ palpation –> RLQ pain
Confirm w/ contrasted CT:
enlarged appendix
appendiceal wall thickening
periappendiceal fat stranding or appendical lith
U/S not reliable enough
Labs - leukocytosis
R/O ectopic pregnancy w/ b-hCG
Tx: preop hydration and abx (cefoxitin, ampicillin + sulbactam)
Appendectomy
hyperplastic colon polyps
MC
rectum, recto-sigmoid - 50%
not precancerous risk
Adenomatous colon polyps
cancer risk
Tubular adenomas - darker nuclei and atypia, tubular glands
Tubulovillious adenomas
Villous adenomas - most “villainous”, villi instead of glands
Juvenile colon polyps
single, benign in rectum - no risk
Juvenile polyposis syn - multiple polyps
-increased risk of adenocarcinoma
Peutz-Jeghers syndrom
50% cancer by 50s
AD
Multiple benign hamartomas - excess normal tissue endogenous to area growing
hyperpigmented areas of lips, mouth, hands, genitalia
increased risk colorectal cancer, small intestine tumors, stomach, pancreas, breast, ovarian, uterine cancers.
Adenocarcinoma of colon (except genes)
over 50 yo
risk: IBD smoking high fat/low fiber diet alcohol use obesity adenomatous polyps 50% colonized w/ S. bovis
Fatigue, wt loss, LAD Abd pain, bowel obstruction, N/V Left sided - change in bowel habitis - pencil thin stools Hematochezia - rectal/sigmoid area Iron deficiency - typical of right sided
Tumor marker: CEA - monitor recurrence
Dx: Colonoscopy fecal occult blood testing barium enema - apple core flexible sigmoidoscopy
Gene mutation pathways for adenocarcinoma of colon
Chromosomal instability APC pathway
1st: lose APC gene
- 80% sporadic, germline mutation –>familial adenomatous polyposis
- -> KRAS mutation - increase growth stimulus
- -> late loss tumor suppressors p53 and DCC on 18q (“deleted in colon cancer”)
Mutation mismatch repair pathway aka microsatellite instability pathway
-less common
-Assoc w/ HNPCC (Lynch Syn)
Dysfunction of NDA mismatch repair enzymes
Familial adenomatous polyposis (FAP)
AD mutation of APC
Lawn of colon polyps
Turcot Syndrome
FAP + malignant CNS tumors (medulloblastoma)
“turbin”
Gardner Syndrome
FAP
Bone and soft tissue tumors
Lipomas
Retinal hyperplasia
Hereditary Nonpolyposis Colon Cancer (HNPCC) - Lynch syndrome
AD - DNA mismatch repair mutation
Proximal colon cancer most
Diverticulosis
blind pouches in colon - many
true - all 3 layers
false - mucosa and submucosal - most diverticulosis
MC in sigmoid colon >60 yo Usually asx vague discomfort in LLQ improved w/ defecation painless rectal bleeding
