Alimentary Tract - Large Intestine Flashcards Preview

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Flashcards in Alimentary Tract - Large Intestine Deck (102):
1

The malignant potential of a colon polyp is determined by what?

histological type - requires biopsy

2

malignant potential: adenoma

neoplastic, precursor for many colorectal cancers

3

malignant potential: hamartoma polyp

nondysplastic, benign growth; non-neoplastic unless associated w/ Peutz-Jeghers, Cowden syndrome, juvenile polyposis syndrome

4

malignant potential: hyperplastic polyp

metaplastic, non-neoplastic, low risk if small (<1 cm) and distal

5

malignant potential: inflammatory pseudopolyp

not true polyp; associated w/ IBD, infectious colitis, ischemic colitis

6

What is the workup of a patient who presents with blood in his/her stool?

ABCs, H&amp;P including frequency/character/timing, rectal exam, CBC, FOBT, colonoscopy

7

In a patient with polyps, what are some potentially modifiable risk factors to prevent CRC?

weight loss, fiber, decreased alcohol intake

8

What is the next step in a patient who was found to have an adenoma that wasn't completely resected endoscopically? Why?

partial colectomy - incompletely resected adenomas harbor a 30% risk of cancer already being present, thus the benefits of cancer prevention outweigh surgical risks

9

During a colonoscopy, how would you remove a pedunculated polyp?

with a snare

10

During a colonoscopy, how would you remove a sessile polyp?

consider removing piecemeal, facilitated by a saline lift

11

During a colonoscopy, you encounter an ulcerated, friable, indurated polyp. How do you proceed?

biopsy and tattoo in 4 quadrants of the distal margin

12

What can be considered if a tattooed polyp cannot be found intraoperatively?

colonoscopy

13

What if a pedunculated polyp is positive for malignancy into the stalk?

polypectomy is adequate if the margins are negative

14

What parameters need to be met for pedunculated polyps with submucosal invasion (also sessile polyps) to be considered adequately treated with polypectomy?

if they are removed in a single piece with 2mm negative margins

15

High-risk lesions with invasion into the lower 1/3 of the submucosa, a resection margin <2 mm, lymphovascular invasion, piecemeal polypectomy, and/or poor differentiation should be treated how?

oncologic surgical resection

16

Follow up if no polyps found on colonoscopy and average risk?

10 yr colonoscopy

17

Follow up for 3–10 adenomas or 1 adenoma >1 cm or an adenoma with villous features or high-grade dysplasia on colonoscopy?

3 yr colonoscopy

18

Follow up for >10 adenomas found on colonoscopy? What should be considered at this point?

<3 year colonoscopy, consider adenomatous polyposis syndrome (FAP, AFAP, MAP)

19

Follow up for adenoma(s) removed piecemeal during colonoscopy?

2 to 6 month colonoscopy to ensure complete excision

20

Endoscopic follow up for Stage I-III colorectal CA surgically treated?

1 year colonoscopy, then every 3-5 years depending on findings

21

Endoscopic follow up for all patients with curative resection and anastomosis and LAR?

proctosigmoidoscopy +/- endorectal u/s every 6-12 months for 3-5 years; every 6 months for 3-5 years if higher risk of local recurrence

22

Endoscopic follow up for all patients s/p transanal local excision of rectal CA?

proctosigmoidoscopy +/- endorectal u/s every 6 months for 3-5 years

23

In regards to polyps, what are the Amsterdam criteria?

Criteria for HNPCC: 3-2-1 rule: 3 affected family members, 2 generations, 1 under age 50. 3 or more relatives with histologically verified Lynch-associated cancers (CRC, endometrial, small bowel, transitional carcinoma of the ureter or renal pelvis). One must be a first-degree relative of the other two. FAP must be excluded. 2 generations are affected by Lynch-associated cancers. 1 or more cancers diagnosed by age 50

24

What is the appropriate operation for an endoscopically unresectable polyp?

Segmental colectomy with high ligation of the vascular pedicle in order to sample the draining lymph node basin.

25

In a patient with a malignant polyp, when can you consider transanal full-thickness biopsy or transanal endoscopic microsurgery (TEM)?

low- or mid-rectal malignant polyps with no evidence on imaging of nodal disease

26

How does your surgical approach differ for a 24-year-old patient with familial adenomatous polyposis (FAP) versus a 43-year-old with three tubulovillous adenomas in the right colon who has a family history of colorectal and endometrial cancer?

The patient with FAP should be offered total proctocolectomy with ileal pouch-anal anastomosis or end ileostomy. Total abdominal colectomy with rectal surveillance can be considered if there is a low polyp burden in the rectum.

The <50 yr pt w/ right-sided adenomas should raise suspicion of HNPCC/Lynch. Lots of screening - colorectal, endometrial, ovarian, skin, neuro gastric.

27

You are asked to see an 86-year-old woman with a 2-cm sessile tubular adenoma in the right colon that was discovered after she had a positive test for occult blood during a routine physician appointment. A colonoscopic biopsy showed no dysplasia. The patient lives in a nursing home and has hypertension and mild congestive heart failure as well as early dementia. How will you counsel this patient and her family?

There is approximately a 5% chance of occult malignancy in a tubular polyp. An attempt should be made at endoscopic resection. The operative risk for partial colectomy with this patient’s comorbidities needs to be weighed against the advantages.

28

Describe how a 3-cm benign polyp may be different in terms of endoscopic management in the cecum versus the sigmoid.

Endoscopic management is the same in a 3-cm benign polyp in the cecum versus the sigmoid; however, an important consideration is that the cecum is thinner and there is a higher risk of perforation. Consider LIFT polypectomy by injecting the submucosa with an epinephrine solution.

29

A gastroenterologist refers a morbidly obese patient to you for management of a 4-cm sessile tubulovillous adenoma in the ascending colon that is not amenable to endoscopic resection. Describe your preoperative decision making.

It is important to localize the polyp endoscopically by tattooing it with India ink, particularly if a laparoscopic resection is planned. A right colectomy will be indicated; an oncologic resection should be performed for any endoscopically unresectable polyp. This morbidly obese patient may benefit from a laparoscopic approach which will minimize postoperative wound complications, pain, and narcotic use.

30

What types of polyps can occur in the large intestine, and which have malignant potential?

  • Neoplastic (adenomatous) – highest malignant risk
  • Hamartomatous (juvenile) – very low malignant risk
  • Inflammatory (pseudopolyps) – seen with inflammatory bowel disease (IBD)
  • Hyperplastic – almost no malignant potential

31

What are the hamartomatous polyposis syndromes?

  • Peutz-Jeghers
  • Cowden
  • juvenile polyposis syndrome

32

CRCs in Lynch syndrome differ from sporadic CRCs in that they are predominantly where in location?

Right-sided

33

Lynch/HNPCC mutation

AD mutation in MMR causing microsatellite instability

34

Approach to screening for patient with known HNPCC

Sorted by age when starting screening

  • 20-25: Q1y colonoscopy or 2-5 yrs prior to fam CRC
  • 25-30: Q1yr PE w/ skin and neuro exam 
  • 30-35: Q1yr pelvic exam, endometrial bx, transvaginal U/S or 3-5 yrs prior to fam endometrial/ovarian cancer
    • Q1yr UA beginning at
    • Q2-3 yrs EGD w/ bx of gastric antrum if increased risk of gastric cancer

35

What do you recommend for a patient with HNPCC/Lynch and an endoscopically unresectable adenoma?

Unlike a regular risk patient, this patient should be offered TAC + IRA w/ annual endoscopy eval.

36

In a female undergoing colon resection for HNPCC/Lynch, what else should be offered?

Ppx TAH w/ BSOO

37

Diverticulum risk increases with what types of diet

high in fat, high in red meat, low fiber

38

What is complicated diverticulitis?

associated with complication - abscess, obstruction, perforation, fistula

39

Describe the presentations for uncomplicated and complicated acute diverticulitis.

  • uncomplicated - acute increasing LLQ pain, nausea, vomiting, low-grade temp, point tenderness
  • complicated - above + hypotension, peritonitis, palpable mass on abdominal/rectal exam, no improvement w/ pain/fever w/in 72 hrs of abx

40

Abdominal pain w/ profuse watery diarrhea, hematochezia, or bloody diarrhea should do what to diverticulitis on ddx?

These sx do not rule out diverticulitis, but other pathological processes should be worked up first, ie infectious colitis, IBD

41

CT scan findings of acute diverticulitis

  • diverticular "tics" throughout
  • localized thickening (4 mm), pericolic fat stranding
  • complicated - free air, pericolic abscess, fistula, air-fluid levels

42

Treat a stable patient w/ diverticulitis and an abscess

  • abx, fluids, bowel rest
  • percutaneous drain

43

Treat diverticulitis w/ hypotension, peritonitis, free fluid or air

OR for ex-lap w/ resection and end ostomy

44

A patient w/ mild diverticulitis is treated as an outpatient, he returns w/ persistent abdominal pain, fevers, and inability to tolerate PO diet. What do you do?

  • admit
  • IV abx, IV fluids, bowel rest
  • repeat imaging - could be more complicated
    • abscess - perc drain
  • if peritonitis, sepsis, or signs of organ failure - OR

45

You are asked to see a 44-year-old man who had a kidney transplant 6 months ago and is taking 20 mg prednisone daily. He is in the emergency room with a fever of 103º and left lower quadrant pain and has a CT scan showing sigmoid diverticulitis and a surrounding phlegmon. What will your recommendation be?

  • immunosuppressed patients have a very high failure rate of medical therapy for acute diverticulitis
  • admit, resusc, IV abx, IVF, serial exams
  • would likely benefit from elective resection

46

What are common indications for a stoma (8)?

  1. protection of intestinal anastomosis
  2. treatment of anastomotic leak
  3. large bowel obstruction
  4. bowel perforation or trauma
  5. intraperitoneal rectal injury
  6. diverticular disease
  7. complex anorectal disease
  8. infections–necrotizing fasciitis or Fournier gangrene

47

When a stoma is indicated, what are the indications for an ileostomy vs colostomy?

  • Ileostomy can be used for fecal diversion, is easier to close, and has lower rate of parastomal hernia.
  • Ileostomy does not decompress the colon with an intact ileocecal valve.
  • Colostomy can be created with a stapled rectal stump to avoid an anastomosis.
  • Left-sided colostomies produce formed stool and have lower rate of electrolyte abnormalities or dehydration than ileostomy, which has high liquid output. 

48

During the creation of a colostomy, when can the left ureter be damaged? 

The mesosigmoid is often attached to the pelvic sidewall and the ureter is frequently found underlying. Otherwise, the ureter can be identified where it crosses over the bifurcation of the iliac vessels. 

Additionally, the left ureter can be swept up with the sigmoid colon and mistaken for the superior rectal artery.

49

When can the right ureter be identified during the creation of a stoma? 

The right ureter should be identified when mobilizing the cecum at the white line of Toldt, and is usually seen beneath the gonadal vein and can be identified by observing peristalsis.

50

During mobilization of the ascending colon and at the hepatic flexure, what should be visualized and avoided? How is this done?

the duodenum

As the transverse colon is being pulled caudally, the duodenum can be expected near the location of the gallbladder.

When retracting the right colon medially to dissect it from the retroperitoneum, identify the duodenum near the renocolic ligament, and avoid rough dissection to prevent injury.

51

What stoma is superior in a patient with an obstructing sigmoid mass requiring temporary diversion?

a loop transverse colostomy, it allows for fecal diversion and decompression of the distal limb

52

What operation is required in a patient with perforated diverticulitis and peritonitis?

resection of the inflamed sigmoid colon, a stapled rectosigmoid stump, and creation of an end descending colostomy

53

Given a stable patient who requires elective surgery for creation of an ostomy, discuss the potential benefits of laparoscopic ostomy creation.

Laparoscopic colorectal surgery is associated with shorter hospital stays, earlier return of bowel function, less narcotic use, and fewer overall complications.

54

When preparing for the creation of an ostomy, understand the importance of preoperative stoma marking, and describe how it is done?

  • Performed by a trained stoma nurse or the surgeon
  • Location should be visible to the patient, lie within the boundaries of the rectus abdominis, and be free of skinfolds and scars.
  • Have at least 2 inches of intact skin around the planned stoma to ensure appropriate wafer sealing.
  • A correctly chosen ostomy site is the most important predictor of the patient's quality of life with the stoma.

55

Why should all stomas be externalized through the rectus abdominis?

prevent parastomal hernia formation

56

What are the operative steps of stoma creation?

  • A disk of skin is removed.
  • Muscle-splitting technique is used to approach the fascia.
  • Divide fascia, allowing 2 fingers to slide through.
  • A Babcock is used to pull the stoma through.
  • The bowel is visualized again for adequate perfusion.
  • Close other incisions before maturation of the colostomy.
  • Create some protrusion of the colostomy above the skin.
  • Mobilize. The marginal artery should not be disrupted.
  • Confirm perfusion w/ pulsatile flow to the cut end.

57

What are the unique operative steps to create a loop colostomy?

  • Bring a loop of the colon through the abdominal wall.
  • Make a transverse incision on the antimesenteric bowel.
  • Fold the cut edges back and suture them to the skin.
  • Transverse or sigmoid colon can be used for loop colostomies.
  • A supporting rod or looped catheter is placed below the common edge of bowel in a loop colostomy to keep it from retracting.

58

What are the steps for a colostomy takedown?

  • A circumferential peristomal incision is made in the skin and dissected to the level of the fascia.
  • Adhesions to the fascia should be dissected to free the colon.
  • Loop colostomies should have the edges freshened and closed transversely with running sutures or reestablish continuity with a side-to-side stapled anastomosis.
  • Loop reversals can be done through a transfascial incision.
  • End colostomies require mobilization and further intraabdominal dissection to reach the rectal stump.
  • The left colon is mobilized off Gerota fascia, and if more mobilization is required, the splenic flexure can be takedown.
  • Colorectal anastomosis is then performed using a circular stapler most commonly or a hand-sewn anastomosis.

59

Why/when could an end descending colostomy be better than a sigmoid colostomy?

descending colon has more reliable perfusion than the sigmoid colon, especially if the inferior mesenteric artery (IMA) is transected

60

Given a patient undergoing colonic surgery with planned colocolonic or colorectal anastomosis, identify variables that increase the risk for anastomotic complications.

  • Malnutrition: low albumin (< 3.5 g/dL)
  • Hx of radiation treatment increases both leak rate and stenosis
  • Immunosuppression: intrinsic, (ie, HIV) or extrinsic (ie, steroids)
  • Smoking
  • Obesity: body mass index (BMI) > 35

61

What is the benefit of diverting a fecal stream for a bowel anastomosis?

Diversion of the fecal stream has not been shown to decrease anastomotic leak, but a diverting stoma lessens the consequences associated with anastomotic leak.

62

How does stoma necrosis occur? How is it assessed? Managed?

  • Due to venous congestion from a tight fascial opening or arterial insufficiency due to excessive mesenteric mobilization.
  • The extent of necrosis is determined by inserting a lubricated test tube into the stoma and shining a light. 
  • If the necrosis is only above the fascia and therefore only within the stoma, this can be observed.
  • If the necrosis extends down to the level of the fascia, immediate revision is required.

63

How do you assess and manage postop stomal bleeding?

  • rare 
  • eval appliance to ensure no laceration to the bowel wall
  • manage with direct pressure, silver nitrate, cautery, or suture
  • bleeding due to peristomal varices associated with cirrhosis can be treated with direct pressure, a suture, or injection sclerotherapy followed by med management of portal HTN.

64

How do you assess and manage postop stomal mucocutaneous separation?

If partial, observation is appropriate and the defect can be filled with absorptive material.

If circumferential, the ostomy should be revised due to risk of stomal stenosis.

65

Which stomas have the highest rate of prolapse?

How do you manage stomal prolapse?

  • Loop transverse colostomies have the highest rate of prolapse, ranging from 30% to 50%, and often involve the distal limb.
  • The prolapse can be reduced manually by invaginating the mucosa back into the stoma.
  • Osmotic agents (eg, table sugar) can help reduce edema.
  • If the mucosa is not viable, stomal revision is indicated.

66

How do you manage stomal retraction?

Secondary to ischemia

Treatment with local wound care and dietary modifications is usually adequate.

With severe stenosis, irrigating the stoma with a cone catheter or revision may be necessary. 

67

What is the most common complication following a colostomy reversal? How is it prevented?

wound infection

prevented by circular/purse-string closure or healing by secondary intention 

68

During a Hartmann procedure for perforated diverticulitis, you perform an end colostomy. Describe your decision making regarding stoma placement and whether the splenic flexure should be mobilized.

With significant contamination, you would avoid mobilizing the splenic flexure if possible to avoid contamination in the left subphrenic space.

The end colostomy should be placed in the easiest location to minimize tension considering the patient's body habitus and skin folds. Due to the inflammation, the mesentery can be foreshortened which can make the mobilization more difficult.

The colostomy should be delivered through the rectus abdominis muscle leaving 3 to 4 cm between the midline and the skin opening.

69

Two days after you have created an end sigmoid colostomy, the mucosa is a dark-blue coloration, almost black in some areas. What will you do?

The stoma can be further evaluated with a flashlight and a clear glass test tube or flexible endoscopy bedside to evaluate the extent of ischemia. Often the ischemia is only above the skin level and observation is appropriate.

If the ischemia extends below the fascia, the patient will require an operation and revision of the stoma with resection of the ischemic portion.

70

What are advantages and disadvantages of a loop transverse colostomy?

  • The stoma is technically easy to perform. The transverse colon is relatively free and often does not require mobilization. The abdominal wall is in thin in the upper abdomen even in obese patients. 
  • Loop transverse colostomies have higher risk of prolapse.
  • The transverse loop colostomy tends to be bulky and is difficult to fit within an ostomy appliance.
  • Right loop transverse colostomies still produce liquid stool compared to descending or sigmoid colostomies.

71

What portions of the colon does the SMA supply?

Ascending and first two-thirds of transverse colon

72

What portions of the colon does the IMA supply?

last third of the transverse, descending, sigmoid, and upper rectum

73

What are the main branches of the SMA to the colon?

ileocolic, middle colic

74

What major artery gives rise to the superior rectal artery?

IMA

75

What arteries provide collateral flow between the IMA and SMA?

marginal artery of Drummond

Arc of Riolan

76

What is the most patulous and distendable portion of the colon? What is the clinical significance of this?

cecum, most vulnerable to perforation if distal obstruction (law of Laplace)

77

An elongated and narrowed mesentery increasing risk for what disease?

volvulus

78

What vascular pedicles do sigmoid and cecal volvuluses twist around, respectively?

IMA, ileocolic

79

What is the Law of Laplace?

wall stress is directly related to pressure and diameter within the vault

it is indirectly related to wall thickness

80

3 most common causes of LBO

malignancy, diverticulitis, volvulus

LBO is cancer unless proven otherwise

81

most common type of volvulus? 2nd most common?

sigmoid, cecal

82

What is the presentation of LBO? What are emergency presenting signs?

abdominal pain, distention, obstipation

peritonitis and systemic toxicity are indications for emergency surgery

83

What is the workup for suspected volvulus?

  • H&P: chronic constipation, colonoscopies
  • CBC, BMP, lactate
  • Acute abd XR series: coffee bean, omega sign
  • CT if not dx w/ XR

84

Once diagnosed, how is volvulus managed?

  • not toxic, sigmoid: colonoscopic decompression then sigmoid resection during admission
  • cecal: ileocecectomy 
  • malignant: high ligation resection w/ 5 cm margin
  • malignant, R0 not possible: proximally divert or stent, plan for neoadj and staging later
  • primary anastomosis is often difficult in an emergency situation

85

A 70-year-old healthy man presents with a large bowel obstruction. CT scan shows an obstruction at the level of the sigmoid colon with proximally dilated colon to 10 cm, and what appears to be a liver metastasis. What is your management of this patient?

  • he has stage IV cancer
  • stent can be placed for temporary relief, but is not a long-term solution (erodes)
  • anastomosis should be avoided since the patient will need chemo
  • ideal: high ligation w/ 5 cm margins, end colostomy; otherwise proximal diversion w/ mucous fistula 

86

A 68-year-old woman with chronic constipation presents with abdominal pain and distension. Radiograph is consistent with sigmoid volvulus. How would you proceed to take care of this patient?

  • if really sick: resuscitate, IV abx, OR
  • if stable: endoscopic decompression, same admission sigmoid resection
    • decompression allows for better anastomosis
    • resection required d/t high recurrence rate

87

What is the presentation of c-diff?

  • diffuse watery diarrhea
  • ileus
  • leukocytosis, abdominal pain, fever

88

What should prompt the workup of c-diff?

3 loose bowel movements in 24 hours in a patient with leukocytosis or fever w/ abdominal pain

higher suspicion given to those w/ abx exposure or previous infx

contact precautions until the patient is cleared

89

In a patient with c-diff, what does it mean if the patient is having watery diarrhea that suddenly stops?

ileus in the setting of c-diff is a marker of severe infection and should raise suspicion for worsening disease

90

Describe the lab workup for c-diff

antigen is the screening - it can be positive after clearance

toxin confirms - it reflects active disease

91

What time interval can retesting be done in c-diff patients?

do not repeat tests within 7 days

92

What is the initial treatment regimen for c-diff (non-fulminant)?

vancomycin PO 125 mg 4x/day x10 days

93

What is fulminant c-diff infection?

c-diff w/ ileus, shock, or megacolon

94

What is the treatment for fulminant c-diff?

PO vanc: 500 mg 4/day x10 days

OR rectal vanc if ileus: 500 mg/100 ml NS q6h as retention enema

ADD IV flagyl 500 mg q8h

95

In an ill patient with c-diff, toxic megacolon, and septic shock, what is the treatment?

emergent subtotal colectomy w/ preservation of the rectum

can argue for loop ileostomy w/ anterograde vanc flushes 

96

What are treatment options for the first recurrence of non-fulminant c-diff?

pulsed/tapered oral vancomycin

OR 10 days of fidaxomicin

97

What is a procedural treatment option for patients w/ non-fulminant c-diff that have failed multiple antibiotic trials?

fecal microbiota transplantation

98

If a c-diff patient treated with appropriate antibiotic management is continuing to have watery diarrhea w/o instability, what are some management options?

step up to fidaxomicin and consider subtotal colectomy w/ ileostomy

99

A 50-year old man is admitted to the MICU with severe pneumonia. After 3 days of multiple, broad-spectrum antibiotics, the patient develops low-grade fevers, a WBC of 32,000 and profuse watery diarrhea. How should you manage this patient?

In this severely ill patient with antibiotic exposure (risk factors) and a typical presentation, can start empiric tx before test results

100

In a patient with known C. difficile colitis treated nonoperatively, what are the chances of cure and chances of recurrence when treated with metronidazole? With vancomycin?

Cure rates for metronidazole are 76%. Vancomycin results in cure 97% of the time. Remission rates are similar for both -- around 15%.

PO vanc is first line. 

http://www.idsociety.org/Guidelines/Patient_Care/IDSA_Practice_Guidelines/Infections_By_Organism-28143/Bacteria/Clostridium_difficile/#recommendations

101

A 56-year-old woman had C. difficile colitis diagnosed 3 weeks ago. She has successfully completed a 10-day course of oral antibiotics, but returns to the clinic with recurrent diarrhea. How will you proceed with diagnosis and treatment for this patient?

Immunodetection for C. difficile toxins remains the definitive test for recurrence. There is not an extended period of false-positive results as can be seen with antibody assays.

102

A 71-year-old previously healthy man has been recently treated for community-acquired pneumonia. After treatment, he developed diarrhea that progressed to severe pseudomembranous colitis prior to seeking medical attention. He has been on antibiotics for 24 hours but continues to have abdominal pain. How will you proceed with the treatment of this patient?

In the absence of hypotension, vasopressor dependence, or extreme leukocytosis, antibiotic treatment can stepped up by changing to fidaxomicin or adding IV flagyl to PO vanc.

If the patient becomes hypotensive or vasopressor-dependent, or develops extreme leukocytosis, he should undergo subtotal abdominal colectomy.