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1

What are the following characteristics of diverticulosis?

  • Percent of lower GI diverticular bleed that stops spontaneously
  • Diagnosis
  • Treatment

  • Percent of lower GI diverticular bleed that stops spontaneously: 75% (recurs in 25%)
  • Diagnosis: NGT (to rule out upper GI source), colonoscopy (diagnostic and therpeutic), Angiogram (1st step in management of massive bleed), tagged RBC scan (for intermittent bleeds that are hard to localize)
  • Treatment: Colonoscopy (ligate bleeder), Angio with coil embolization, may need segmental colectomy or subtotal colectomy if bleeding is not localized or controlled.

 

[Diverticulosis is the most common cause of a lower GI bleed. It is caused by disrupted vasa rectum (resulting in arterial bleeding). Patients with recurrent diverticular bleeds should have resection of the area that has recurrent bleeding.]

2

What are the respective resolutions of the following imaging modalities as it pertains to detecting intrahepatic metastases?

  • Conventional U/S
  • Abdominal CT
  • Abdominal MRI
  • Intraoperative U/S

  • Conventional U/S: 10 mm
  • Abdominal CT: 5-10 mm
  • Abdominal MRI: 5-10 mm (better than CT)
  • Intraoperative U/S: 3-5 cm

 

[Intraoperative U/S is the best method of picking up intrahepatic metastases.]

3

Which is more sensitive to ischemia: Colon or small bowel?

Colon is more sensitive to ischemia secondary to decreased collaterals

4

Which 3 chemotherapy agents are used in colorectal cancer?

  • 5-FU
  • Leucovorin
  • Oxaliplatin

 

[FOLFOX.]

5

What is the appropriate management for a patient with a sigmoid volvulus?

  • If no evidence of gangrenous bowel or peritoneal signs then decompress with colonoscopy (80% reduce, 50% will recur), give bowel prep, and perform sigmoid colectomy during same admission
  • If signs of gangrenous bowel or peritonitis are present then go straight to the OR

6

What are the following characteristics of GI bleeding?

  • Length of time stool guaiac can remain positive after lower GI bleed
  • Cause of azotemia after GI bleed
  • Bleeding rate required for detection on arteriography
  • Bleeding rate required for detection on tagged RBC scan

  • Length of time stool guaiac can remain positive after lower GI bleed: 3 weeks
  • Cause of azotemia after GI bleed: Production of urea from bacterial action on intraluminal blood (Increased BUN; also get elevated total bilirubin)
  • Bleeding rate required for detection on arteriography: > 0.5 cc/min
  • Bleeding rate required for detection on tagged RBC scan: > 0.1 cc/min

7

Which 3 characteristics of a colon polyp increase cancer risk?

  1. > 2cm
  2. Sessile
  3. Villous

8

What are the following characteristics of colonic angiodysplasia?

  • Side that angiodysplasia most commonly occurs on
  • Bleeding severity and risk of recurrence compared to diverticular bleeds
  • Venous or arterial bleeding
  • Percent of patients with angiodysplasia that have aortic stenosis

  • Side that angiodysplasia most commonly occurs on: Right side
  • Bleeding severity and risk of recurrence compared to diverticular bleeds: Less severe than diverticular bleeds but more likely to recur (80% compared to 25% for diverticular bleeds)
  • Venous or arterial bleeding: Venous (Diverticular bleeds are arterial)
  • Percent of patients with angiodysplasia that have aortic stenosis: 20%

 

[Soft signs of angiodysplasia on angiogram include tufts and slow emptying.]

9

What is the treatment for diversion colitis (stump pouchitis)?

Short-chain fatty acids

 

[UpToDate: Diversion colitis or diversion proctitis is a nonspecific inflammatory disorder that occurs in segments of the colon and rectum that are diverted from the fecal stream by surgery (eg, creation of a loop colostomy/ileostomy or an end colostomy/ileostomy with closure of the distal colon segment [eg, Hartmann's procedure]).

Surgical reanastomosis is the treatment of choice in symptomatic patients with diversion colitis. Medical therapy (eg, short-chain fatty acid [SCFA] enemas, topical 5-aminisalicylic acid, and topical glucocorticoids) should be reserved for symptomatic patients who are not candidates for surgery or in whom diversion colitis cannot be distinguished from active distal inflammatory bowel disease (IBD).

SCFA enemas are used as initial therapy in patients with diversion colitis who are unable or unwilling to undergo surgery and in patients with known distal IBD in whom the diagnosis of diversion colitis is unclear. In patients with underlying IBD, we use SCFA enemas in combination with topical antiinflammatory drugs.]

10

What are the following characteristics of ulcerative colitis?

  • Most common extraintestinal manifestation requiring total colectomy
  • 2 extraintestinal manifestations of ulcerative colitis that do not improve with colectomy
  • 3 extraintestinal manifestations of ulcerative colitis that do improve with colectomy
  • 1 extraintestinal manifestation of ulcerative colitis that sometimes (50%) improves with colectomy

  • Most common extraintestinal manifestation requiring total colectomy: Failure to thrive in children
  • 2 extraintestinal manifestations of ulcerative colitis that do not improve with colectomy: Primary sclerosing cholangitis and ankylosing spondylitis
  • 3 extraintestinal manifestations of ulcerative colitis that do improve with colectomy: Most ocular problems, arthritis, and anemia
  • 1 extraintestinal manifestation of ulcerative colitis that sometimes (50%) improves with colectomy: Pyoderma gangrenosum

11

What is the 5-year survival of a colorectal cancer patient with resectable liver metastases?

35% 5-year survival

 

[If resection leaves adequate liver function.]

12

What is the main nutrient of colonocytes?

Short-chain fatty acids (SCFAs)

 

[UpToDate: SCFAs, predominantly acetate, propionate, and n-butyrate, are derived from anaerobic bacterial metabolism of unabsorbed dietary carbohydrates. They are absorbed from the lumen by a combination of simple diffusion and ion exchange and oxidized by colonocytes. In addition to supplying 70% of the fuel used by mucosal cells, luminal SCFAs have a number of other effects, including modulation of fluid and electrolyte transport, colonic motility, mucosal blood flow, and production of inflammatory cytokines. Other luminal nutrients for colonocytes, such as glutamine, may also play a role in the pathogenesis of diversion colitis.]

13

Do colon polyps have a left or right side predominance?

Left side predominance

14

Rectal cancer can metastasize directly to the spine via which plexus of vessels?

Batson's plexus

 

[Colon cancer typically doesnt metastasize to bone.]

15

Most colorectal cancers in which region can be treated with primary anastamosis after resection without needing an ostomy?

Right-sided colorectal cancer

 

[Need 2cm margins.]

16

What percent of patients with colorectal cancer recur after surgical resection?

20%

 

[Recurrence usually occurs in the first year. 5% get another primary which is the main reason for surveillance colonoscopy. Follow-up colonoscopy is done at 1 year.]

17

What are the following characteristics of diverticulitis?

  • Most common complication of diverticulitis
  • Treatment for uncomplicated diverticulitis
  • Treatment of complicated diverticulitis
  • Treatment of right-sided diverticulitis
  • Best diagnostic tool for suspected colovesicular fistula

  • Most common complication of diverticulitis: Abscess formation
  • Treatment for uncomplicated diverticulitis: Levofloxacin and flagyl, bowel rest for 3-4 days (treat mild cases as outpatient)
  • Treatment of complicated diverticulitis: Resect all of sigmoid colon down to the superior rectum (distal margin should be normal rectum)
  • Treatment of right-sided diverticulitis: Right hemicolectomy
  • Best diagnostic tool for suspected colovesicular fistula: Cystoscopy

 

[Need follow-up colonoscopy after an episode of diverticulitis to rule out colorectal cancer.]

18

What are the criteria that make a low rectal T1 cancer eligible for transanal resection?

  • < 4cm
  • Negative margins (need 1 cm)
  • Well differentiated
  • No neurologic or vascular invasion

 

[If these criteria are not met, an APR or LAR are required. Low rectal T2 cancers or higher require an APR or LAR.]]

19

What is the role of chemotherapy in treating colorectal cancer?

  • Stage III and IV colon cancer --> Postop chemotherapy (no XRT)
  • Stage II and III rectal cancer --> Pre-op chemo and XRT
  • Stage IV rectal cancer --> Chemo and XRT +/- surgery (possibly just a colostomy, may choose to avoid APR in patients with metastatic disease.)

 

[UpToDate: In our view, patients with potentially resectable disease should undergo multivisceral resection rather than upfront chemoradiotherapy, if they are surgical candidates. Consensus-based guidelines from the National Comprehensive Cancer Network (NCCN) suggest that patients with locally unresectable colon cancer or who are medically inoperable be given chemotherapy for advanced disease.

For patients who have undergone potentially curative resection of a colon cancer, the goal of postoperative (adjuvant) chemotherapy is to eradicate micrometastases, thereby reducing the likelihood of disease recurrence and increasing the cure rate. The benefits of adjuvant chemotherapy have been most clearly demonstrated in patients with stage III (node-positive) disease, who have an approximately 30% reduction in the risk of disease recurrence and a 22% to 32% reduction in mortality with modern chemotherapy.

Most treatments involve a combination of several chemotherapy drugs, which are given intravenously, in a specific order on specific days. For patients with node-positive colon cancer, a six-month course of oxaliplatin-containing chemotherapy is generally recommended for most patients, although the benefits of oxaliplatin are controversial in the elderly.

Among patients with resected node-negative (stage II) disease, the benefits of chemotherapy are controversial, as is the relative benefit of an oxaliplatin as compared with a non-oxaliplatin-based regimen. Treatment decisions must be individualized.]

20

Which portions of the colon are retroperitoneal?

  1. Ascending colon
  2. Descending colon
  3. Sigmoid colon

 

[Transverse colon is intraperitoneal.]

 

[UpToDate: The colon and rectum occupy retroperitoneal and intraperitoneal spaces, in close approximation to solid organs. The ascending and descending colon are retroperitoneal, while the transverse colon, which extends from the hepatic flexure to the splenic flexure, is intraperitoneal. The sigmoid colon continues from the descending colon, ending where the teniae converge to form the rectum. The rectum is the distal continuation of the colon, measuring 12 to 15 cm in length. The rectum lies anterior to the three inferior sacral vertebrae, the coccyx, and sacral vessels, and is posterior to the bladder in men and the vagina in women. The anterior upper two-thirds of the rectum are located intraperitoneally and the remainder is extraperitoneal.

21

At what age does colonoscopy screening for colon cancer begin?

  • Age 50 for normal risk
  • Age 40 for intermediate risk or 10 years before youngest first degree relative with colon cancer diagnosis

22

Where does colorectal cancer fall on the list deaths caused by cancer?

2nd leading cause of cancer death

23

What are the following characteristics of inflammatory bowel disease?

  • Most common location of perforation in ulcerative colitis
  • Most common location of perforation in crohn's disease

  • Most common location of perforation in ulcerative colitis: Transverse colon
  • Most common location of perforation in crohn's disease: Distal ileum

24

What are the following characteristics of colon pathphysiology?

  • Most likely location for colon perforation to occur in setting of obstruction
  • #1 cause of colonic obstruction
  • #2 cause of colonic obstruction
  • Problem associated with pneumatosis intestinalis
  • Problem associated with air in the portal system

  • Most likely location for colon perforation to occur in setting of obstruction: Cecum (LePlace's law: Tension = pressure x diameter)
  • #1 cause of colonic obstruction: Cancer
  • #2 cause of colonic obstruction: Diverticulitis
  • Problem associated with pneumatosis intestinalis: Ischemia and dissection of air through areas of bowel wall
  • Problem associated with air in the portal system: Significant infection or necrosis of the large or small bowel (often an ominous sign)

25

Injury to which nerve during an abdominal perineal resection (APR) can result in impotence and bladder dysfunction?

Pudendal nerves

26

What are the names of the following components of the colon?

  • Inner nerve plexus
  • Outer nerve plexus
  • Mucus-secreting goblet cells
  • Rectovesicular fascia in men, Rectovaginal fascia in women
  • Rectosacral fascia

  • Inner nerve plexus: Meissner's (submucosal) plexus
  • Outer nerve plexus: Auerbach's (myenteric) plexus
  • Mucus-secreting goblet cells: Crypts of Lieberkuhn
  • Rectovesicular fascia in men, Rectovaginal fascia in women: Denonvilliers (anterior) fascia
  • Rectosacral fascia: Waldeyer's (posterior) fascia

27

What is the difference between Lynch I and Lynch II subtypes of Lynch syndrome?

  • Lynch I: Just colon cancer risk
  • Lynch II: Colon cancer risk + risk of ovarian, endometrial, bladder, and stomach cancer

28

What are the below characteristics of colorectal cancer?

  • Most common site of primary
  • Most important prognostic factor
  • #1 site of metastasis
  • #2 site of metastasis
  • Histological subtype with worst prognosis

  • Most common site of primary: Sigmoid colon
  • Most important prognostic factor: Nodal status
  • #1 site of metastasis: Liver
  • #2 site of metastasis: Lungs
  • Histological subtype with worst prognosis: Mucoepidermoid

 

[Isolated liver or lung metastases should be resected.]

29

How does the venous drainage differ between the superior, middle, and inferior rectal veins?

  • The superior and middle rectal veins drain into the IMV and eventually the portal vein
  • The inferior rectal veins drain into the internal iliac veins and eventually the caval system

 

[Picture is misleading and suggests the middle and inferior veins drain in similar fashion.]

 

[UpToDate: The colon and rectum occupy retroperitoneal and intraperitoneal spaces, in close approximation to solid organs. The ascending and descending colon are retroperitoneal, while the transverse colon, which extends from the hepatic flexure to the splenic flexure, is intraperitoneal. The sigmoid colon continues from the descending colon, ending where the teniae converge to form the rectum. The rectum is the distal continuation of the colon, measuring 12 to 15 cm in length. The rectum lies anterior to the three inferior sacral vertebrae, the coccyx, and sacral vessels, and is posterior to the bladder in men and the vagina in women. The anterior upper two-thirds of the rectum are located intraperitoneally and the remainder is extraperitoneal.

The blood supply to the colon is derived from the superior (SMA) and inferior mesenteric arteries (IMA), and internal iliac artery. The SMA, ileocolic, right colic, and middle colic arteries supply the cecum, right colon, and first portion of the transverse colon respectively. The venous outflow generally follows the arterial supply. The transverse colon derives its blood supply from both the SMA and IMA. The watershed area between these vessels is at risk for ischemia. The descending and sigmoid colon are supplied by the left colic artery and the superior sigmoid artery, branches of the IMA. The rectum is supplied by the superior, middle rectal, and inferior rectal artery. Venous drainage from the rectum is from the superior rectal and middle rectal veins draining to the inferior mesenteric veins, and the inferior rectal veins draining to the internal pudendal veins.]

30

What are the 4 layers of the colon from the lumen outwards?

  1. Mucosa (columnar epithelium)
  2. Submucosa
  3. Muscularis propria
  4. Serosa

 

[The muscularis mucosa is the small interwoven inner muscle layer just below mucosa but above the basement membrane. The muscularis propria is the circular layer of muscle.]