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Flashcards in Colon Deck (53):
1

Function of the colon

reabsorption of water and sodium
secretion of potassium and bicarb
storage of feces

2

Is the colon retroperitoneal or intraperitoneal?

Ascending and descending colon are fixed retroperitoneally
Transverse colon is intraperitoneal
Sigmoid is also intraperitoneal

3

What part of the colon does the SMA supply (and what are the branches of the SMA that supply it)?

The SMA gives off the ileocolic, right colic, and middle colic arteries. These supply the cecum, ascending, and proximal to mid-transverse colon.

4

What part of the colon does the IMA supply (and what are the branches of the IMA that supply it)?

IMA gives off left colic, sigmoid, and superior hemorrhoidal arteries. This supplies the mid-transverse colon to the rectum. This area is also supplied by the middle and inferior hemorrhoidal arteries, which don't come from the IMA- they come from the internal iliac.

5

What is the long anastamoses between the SMA and IMA?

anastomosis of Riolan

6

What are the arcades that are close to the mesenteric border of the colon called?

The marginal artery (of Drummond)

7

What is the venous drainage of the colon?

SMV and IMV.
IMV joins the splenic vein. The splenic vein joins the SMV and together they form the portal vein. So, mesenteric blood flow goes to the liver- it's detoxed before it goes back to the central circulation

8

What is ulcerative colitis? Where does it occur?

Inflammation of the colon, starting from rectum and going retrograde. Inflam is confined to mucosa and submucosa only.

9

What human leukocyte antigens are a/w ulcerative colitis?

HLA-AW24 and HLA-BW25

10

Px of UC

bloody diarrhea, fever, abd pain, weight loss.
If abd distention (d/t massive colonic distention), it's toxic megacolon, which can progress to perforation, peritonitis.

11

Dx eval for UC

Colonscopy- shows thickened, friable mucosa. Also fissures and pseudopolyps.
Biopsy- ulceration limited to mucosa and submucosa.
Barium enema- "stovepipe colon" w smooth edges and ulcers

12

Complications in UC

Perforation
Obstruction
Hemorrhage
Toxic megacolon
Colon cancer (10%)

13

Rx for UC

Medical Rx- steroids, immunosuppressants, Sulfasalazine. Topical mesalamine (enema) for mild/moderate
Also fluids, electrolytes, TPN if needed
Infliximab monoclonal Ab against TNF

Later surgery if indicated

14

What are the indications for surgery in UC?

colonic obstruction
massive blood loss
failure of medical Rx
toxic megacolon
cancer

15

What is diverticulosis?

Diverticula- outpouching of colonic wall
Occurs at points where arterial supply penetrates the bowel wall.
Acutally false diverticula, bc not all layers of bowel wall are included

16

Where do most diverticula occur?

Sigmoid colon

17

What is the most common cause of lower GI hemorrhage?

Diverticulosis- usu from R colon

18

Pt px of diverticulosis

Bleeding from rectum but no other complaints.
Maybe had previous bleeding/crampy abd pain in LLQ

19

Dx eval for diverticulosis

If bleeding stopped spontaneously- do a colonoscopy to determine etiology.
If bleeding is continuous- do radioisotope bleeding scan (ok) or mesenteric angiography (best)

20

Rx for diverticulosis

If asx- no Rx. 80% stop spontaneously.
If recurrent bleeding- surgical resection
If active bleeding- rx via colonoscopy- embolize bleeding vessel w angiography.
if all else fails- emergent subtotal colectomy (remv most of the colon)
if bleeding site id'd- segmental colectomy of that part.

21

What is diverticulitis?

Infection of diverticula. Narrow neck --> increased intraluminal prs or inspissated food particles.
Infection --> localized or free perforation into the abd.

22

Where does diverticulitis most commonly occur?

Sigmoid colon

23

Px of diverticulitis

LLQ pain, abd tenderness.
local peritoneal signs- rebound, guarding.
if diffuse peritoneal signs, it's free intra-abd perforation :(

24

Dx Eval of diverticulitis

Blood- WBC count high
XR- normal
CT- shows percolic fat stranding, bowel wall thickening, or abscess
Do NOT do colonoscopy or barium enema- can cause/worsen perforation

25

Complications of diverticulitis

stricture
perforation
fistula w bladder, skin, vag, other part of bowel

26

Rx for diverticulitis

Most are mild- oral abx outpatient: cipro and metronidazole to cover bowel flora
Severe cases- hospitalize w bowel rest and IV abx- ampicillin, levofloxacin, metronidazole
if no improvement- CT drainage
If perforation, surgical drainage + colostomy
If complications or multiple attacks- surgical resection

27

How does colon cancer start out?

Adenomatous polyp which undergoes malignant transformation.

28

What genes are a/w colon ca?

50% have Ras gene mutation
75% have p53 gene mutation

29

What are the classifications of adenomatous polyps?

Tubular and villous (some lesions have characteristics of both)
Villous = bad. Higher villous component = higher malignancy.
Size also matters - bigger size - more malignant.

30

What type of cancer is colon cancer?

90% are adenocarcinoma
and 20% of those are mucinous- worst pgx.
Other types: squamous, adenosquamous, lymphoma, sarcoma, carcinoid

31

Screening for colon ca?

Start at 50, 40 if increased risk.
Yearly fecal-occult blood test
Sigmoidoscopy every 3-5 yrs
Colonoscopy or barium enema every 10 years

32

Px of colon ca

Occult blood in stool can be only sign.
R colon lesions- bleeding
L colon lesions- obstructive sx, chg in stool caliber, tenesmus (feel like constantly need to pass stool), constipation
Constitutional- weight loss, anorexia, fatigue

33

Dx eval for colon ca

Hematocrit- shows anemia
CEA- good for measuring recurrence
LFTs abn if liver mets
Barium enema- can show malignancy
Colonoscopy- can biopsy/excise lesion
CT- look for extent of dz, mets
PET- mets, esp if CEA indicates recurrence
If rectal lesions- endorectal US

34

Rx for colon ca

Surgical removal of lesion.
If endoscopic removal + path report says carcinoma in situ with complete excision- that's all.
If can't be remvd endoscopically- bowel resection
If lesions close to anus- colostomy

35

What is the most common site for colon ca mets?

The liver

36

Which has less morbidity, open or laparoscopic removal for colon resection?

Lap

37

What chemo is used for colon ca?

5FU and levamisole

38

Describe colectomy op

Pre-op mechanical and antimicrobial cleanse.
Midline incision
To mobilize R or L colon, must incise R or L white line of Toldt
Avoid ureter- use ureteral stent if necessary.
After colon mobilization, incise peritoneum over the mesentery to its root, ligate all mesenteric vessels.
Anastamose.

39

What is the px of angiodysplasia?

Multiple episodes of low-grade lower GI bleeding.
10% have massive bleeding
Common in elderly

40

Dx eval of angiodysplasia

arterography
nuclear scans
colonscopy

41

Rx for angiodysplasia

Endoscopy w laser ablation
electrocoagulation
angiography w vasopressin

but 80% of lesions re-bleed, so definitive Rx (segmental colonoscopy) is usu recommended.

42

What is volvulus?

Part of colon rotates on its mesentery, obstructing blood flow and creating closed-loop obstruction

43

Most common locations for volvulus?

Sigmoid (75%)
Cecum (25%)

44

Risk factors for volvulus

Age
Chronic constipation
Prev abd surgery
Neuropsychiatric disorders

45

Pt px for volvulus

acute onset crampy abd pain and distention.
tender, distended abd, peritoneal signs- rebound, guarding
Can turn into frank peritonitis, shock

46

Dx eval for volvulus

Abd XR- massively distended colon and "bird's beak" at the point of obstruction

47

Rx for volvulus

Sigmoid volv- reduce via rectal tube, enema, or proctoscopy. But often recurs, so after you fix it, operate.
Cecal volv- operate immed bc can't really fix it

48

Most coomon reason for urgent abd operation

Appendicitis

49

Px of appendicitis

Epigastric pain that migrates to RLQ
Anorexia!
RLQ tenderness, McBurney's point
Rebound, guarding
Low fever
if high fever- perforation

50

Signs of peritoneal irritation in appendicitis

obturator sign- pain on external rotation of flexed thigh
psoas sign- pain on right thigh extension

51

Where is McBurney's point?

between umbilicus and ASIS (anterior superior iliac spine)

52

Dx eval for appendicitis

WBC mildly elevated
US- wall thickening, luminal distention, lack of compressibility (also good to r/o ovarian path in women)
Barium enema- shows non-filling of appendix
CT shows inflam

53

Rx for appendicitis

Appendectomy- either open or lap
If appendiceal abscess w clinical improvement- can have abx and CT-guided drainage
Kids w perforation- appendectomy w drainage of abscess