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Surgery > Colon > Flashcards

Colon Flashcards

1
Q

Function of the colon

A

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

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2
Q

Is the colon retroperitoneal or intraperitoneal?

A

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

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3
Q

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

A

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

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4
Q

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

A

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.

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5
Q

What is the long anastamoses between the SMA and IMA?

A

anastomosis of Riolan

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6
Q

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

A

The marginal artery (of Drummond)

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7
Q

What is the venous drainage of the colon?

A

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

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8
Q

What is ulcerative colitis? Where does it occur?

A

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

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9
Q

What human leukocyte antigens are a/w ulcerative colitis?

A

HLA-AW24 and HLA-BW25

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10
Q

Px of UC

A

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.

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11
Q

Dx eval for UC

A

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

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12
Q

Complications in UC

A 
Perforation
Obstruction
Hemorrhage
Toxic megacolon
Colon cancer (10%)
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13
Q

Rx for UC

A

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

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14
Q

What are the indications for surgery in UC?

A 
colonic obstruction
massive blood loss
failure of medical Rx
toxic megacolon
cancer
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15
Q

What is diverticulosis?

A

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

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16
Q

Where do most diverticula occur?

A

Sigmoid colon

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17
Q

What is the most common cause of lower GI hemorrhage?

A

Diverticulosis- usu from R colon

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18
Q

Pt px of diverticulosis

A

Bleeding from rectum but no other complaints.

Maybe had previous bleeding/crampy abd pain in LLQ

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19
Q

Dx eval for diverticulosis

A

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

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20
Q

Rx for diverticulosis

A

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.

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21
Q

What is diverticulitis?

A

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

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22
Q

Where does diverticulitis most commonly occur?

A

Sigmoid colon

23
Q

Px of diverticulitis

A

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

24
Q

Dx Eval of diverticulitis

A

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
Q

Complications of diverticulitis

A

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

26
Q

Rx for diverticulitis

A

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
Q

How does colon cancer start out?

A

Adenomatous polyp which undergoes malignant transformation.

28
Q

What genes are a/w colon ca?

A

50% have Ras gene mutation

75% have p53 gene mutation

29
Q

What are the classifications of adenomatous polyps?

A

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

30
Q

What type of cancer is colon cancer?

A

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

31
Q

Screening for colon ca?

A

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
Q

Px of colon ca

A

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
Q

Dx eval for colon ca

A 
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
Q

Rx for colon ca

A

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
Q

What is the most common site for colon ca mets?

A

The liver

36
Q

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

A

Lap

37
Q

What chemo is used for colon ca?

A

5FU and levamisole

38
Q

Describe colectomy op

A

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
Q

What is the px of angiodysplasia?

A

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

40
Q

Dx eval of angiodysplasia

A

arterography
nuclear scans
colonscopy

41
Q

Rx for angiodysplasia

A

Endoscopy w laser ablation
electrocoagulation
angiography w vasopressin

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

42
Q

What is volvulus?

A

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

43
Q

Most common locations for volvulus?

A

Sigmoid (75%)

Cecum (25%)

44
Q

Risk factors for volvulus

A

Age
Chronic constipation
Prev abd surgery
Neuropsychiatric disorders

45
Q

Pt px for volvulus

A

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

46
Q

Dx eval for volvulus

A

Abd XR- massively distended colon and “bird’s beak” at the point of obstruction

47
Q

Rx for volvulus

A

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
Q

Most coomon reason for urgent abd operation

A

Appendicitis

49
Q

Px of appendicitis

A 
Epigastric pain that migrates to RLQ
Anorexia!
RLQ tenderness, McBurney's point
Rebound, guarding
Low fever
if high fever- perforation
50
Q

Signs of peritoneal irritation in appendicitis

A

obturator sign- pain on external rotation of flexed thigh

psoas sign- pain on right thigh extension

51
Q

Where is McBurney’s point?

A

between umbilicus and ASIS (anterior superior iliac spine)

52
Q

Dx eval for appendicitis

A

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
Q

Rx for appendicitis

A

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

Surgery (20 decks)

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