Colorectal

Where does the hindgut begin and end?

• Hindgut begins at distal third of the transverse colon and extends to the rectum

The hindgut relies on which artery for its blood supply?

• Inferior mesenteric artery

What are the white lines of Toldt?

• The lateral peritoneal reflections of the ascending and descending colon

What parts of the gastrointestinal (GI) tract do not have a serosa?

• Esophagus, middle, and distal rectum

What are the major anatomic differences between the small bowel and colon?

• The small bowel is smooth, whereas the colon has fat appendages (appendices epiploicae), haustra, and taenia coli

What is the arterial blood supply to the rectum?

• Proximal: superior hemorrhoidal artery (superior rectal artery) from the inferior mesenteric artery

• Middle: middle hemorrhoidal artery (middle rectal artery) from the hypogastric artery (internal iliac artery)

• Distal: inferior hemorrhoidal artery (inferior rectal artery) from the pudendal artery, which is a branch of hypogastric artery (internal iliac artery)

What is the venous drainage of the rectum?

• Proximal: inferior mesenteric vein that joins the splenic vein to drain into the portal vein

• Middle: iliac vein into the inferior vena cava

• Distal: iliac vein into inferior vena cava

What is the purpose of the colon?

• Water, sodium, and bile salt absorption and stool storage

What is the main nutrient of a colonocyte?

• Short-chain fatty acids (SCFA) (butyrate)

How long is the rectum?

• 12 to 15 cm

What are the approximate proximal and distal extents of the anal canal/rectum/rectosigmoid junction from the anal verge?

• Anal canal: 0 to 5 cm

• Rectum: 5 to 15 cm

• Rectosigmoid junction: 15 to 18 cm

What 2 points are considered to mark the location of the rectosigmoid junction?

• The distal point at which the taeniae converge at the level of the sacral promontory

What do anatomists consider the distal extent of the rectum versus what surgeons consider the distal extent of the rectum?

• Anatomists: dentate line

• Surgeons: proximal border of the anal sphincter complex

What is the eponym for the extension of the peritoneal cavity between the rectum and back wall of the uterus in the female human body?

• Pouch of Douglas (Ehrhardt-Cole Recess/rectouterine excavation/rectouterine pouch)

What is the deepest point of the peritoneal cavity in women?

• Pouch of Douglas

What is another name for the rectovesicular fascia in men/rectovaginal fascia in women?

• Denonvilliers fascia

What is the eponym for a mass that forms in the pelvic cul-de-sac from a drop metastases from a visceral tumor that may be detected by a digital rectal examination?

• Bloomer shelf

What is the thick condensation of endopelvic fascia that connects the presacral fascia to the fascia propria at the level of S4, which then extends to the anorectal ring called?

• Waldeyer fascia (rectosacral fascia)

What artery is contained within the lateral rectal stalks?

• The middle rectal artery

What muscles make up the pelvic floor (pelvic diaphragm)?

• Pubococcygeus, iliococcygeus, puborectalis (which form the levator ani)

Where does the pelvic floor (pelvic diaphragm) lie?

• Between the pubis, obturator fascia, sacrum, and ischial spines

What artery runs close to the bowel in the mesentery as part of a vascular arcade that connects the superior mesenteric artery and inferior mesenteric artery?

• The marginal artery of Drummond

What artery found low in the mesentery, near the root, is part of a vascular arcade that connects the proximal middle colic artery to the proximal inferior mesenteric artery?

• The arc of Riolan (meandering mesenteric artery)

What is the most proximal branch of the inferior mesenteric artery?

• Left colic artery

Describe the venous drainage of the colon and rectum?

• Right and proximal transverse colon drain into the superior mesenteric vein, which joins with the splenic vein to become the portal vein

• Distal transverse colon, descending colon, sigmoid, and most of the rectum drain into the inferior mesenteric vein, which drains into the splenic vein that joins with the superior mesenteric vein to become the portal vein

• Anal canal drains by way of the middle and inferior rectal veins into the internal iliac veins, which drain into the inferior vena cava

What nodal chain do lymphatics from the colon and proximal two-thirds of the rectum drain into?

• Para-aortic nodal chain

What nodal chains do lymphatics from the distal rectum and anal canal drain into?

• Para-aortic nodal chain or superficial inguinal nodal chain

What kind of neurologic injury after rectal surgery generally results in sympathetic dysfunction characterized by retrograde ejaculation and bladder dysfunction?

• Severing of the hypogastric nerves near the sacral promontory

What kind of neurologic injury after rectal surgery generally results in impotence and atonic bladder?

• Injury to the mixed parasympathetic and sympathetic periprostatic plexus

What is the most prevalent species of bacteria in the colon?

• Bacteroides species

What is the most common aerobe in the colon?

• Escherichia coli

In what colonic segment are bacteria the most metabolically active?

• The cecum

How is diarrhea defined?

• >3 loose stools/d

How is constipation defined?

• <3 stools/wk

What are absolute contraindications to bowel preparation?

• Complete bowel obstruction, free perforation

How are the diverticula with colonic diverticulosis formed?

• Mucosa herniates through the colon at sites of penetration of the muscular wall by arterioles on the side of the antimesenteric taeniae

What area of the colon is most commonly affected by diverticula?

• Sigmoid colon (80%)

What segment of the colon has the smallest intraluminal diameter?

• Sigmoid colon

What is the treatment for uncomplicated diverticulitis?

• Antibiotics on an outpatient basis; if patient has significant pain (localized peritonitis), admit to the hospital and give intravenous (IV) antibiotics for ~48 hours

How should patients be followed after an episode of uncomplicated diverticulitis?

• After symptoms have subsided for at least 3 weeks, a colonoscopic examination should be performed to establish the presence/location of the diverticula and to exclude cancer (mimic diverticulitis)

What is the approximate chance of a patient who recovered from an initial episode of uncomplicated diverticulitis developing a second attack of diverticulitis?

• <25%

What is the estimated percentage of patients who recovered from an initial episode of uncomplicated diverticulitis requiring a subsequent emergency colectomy or colostomy?

• ~5%

Although controversial, what types of patients might you offer an elective sigmoid colectomy?

• Young patients with an episode of diverticulitis (<45 years old), patients with 2 episodes of diverticulitis, and immunocompromised patients

What is the treatment for an abscess complicating diverticulitis?

• The preferred treatment is computed tomography (CT) or ultrasound-guided percutaneous drainage or drainage of a pelvic abscess into the rectum through a transanal approach followed by elective surgery ~6 weeks after drainage of the abscess when the patient has completely recovered from the infection versus a more undesirable transabdominal approach by laparotomy

What are the 2 causes of generalized peritonitis resulting from diverticulitis?

• A perforated diverticulum into the peritoneal cavity that is not sealed by the body's normal defenses; an initially localized abscess that expands and suddenly bursts into the peritoneal cavity

What procedure would you perform for generalized peritonitis from perforated diverticulitis?

• A Hartmann procedure: resection of the diseased sigmoid colon; creation of a descending colostomy using noninflamed tissue; closure of the divided end of the rectum with suture/staples

What is the usual time period to wait before restoring intestinal continuity by reversing a Hartmann procedure for perforated diverticulitis?

• At least 10 weeks (when patient has completely recovered from their illness)

What is the Hinchey classification grading system for diverticulitis?

• Stage I Diverticulitis with associated pericolic abscess

• Stage II Diverticulitis associated with distant abscess (retroperitoneal or pelvic)

• Stage III Diverticulitis associated with purulent peritonitis

• Stage IV Diverticulitis associated with fecal peritonitis

What is the most common colonic segment to be involved in a volvulus?

• Sigmoid colon

What is the least common colonic segment to be involved in a volvulus?

• Transverse colon

What is a cecal bascule?

• The cecum folds anteromedial to the ascending colon from the presence of a constricting band across the ascending colon

What findings might you see on plain film, CT scan, and barium enema with a sigmoid volvulus?

• Plain film: bent inner tube with apex in the right upper quadrant

• CT scan: mesenteric whorl

• Barium enema: bird's beak deformity

What is the treatment for sigmoid volvulus?

• Appropriate resuscitation; decompression with placement of a soft rectal tube through the proctoscope past the twist of the volvulus and leaving the rectal tube in place

• If a rectal tube cannot be passed, detorsion of the volvulus with a colonoscope

• If unable to detorse volvulus by rectal tube or colonoscopy, perform Hartmann operation procedure

• Confirm the reduction with an abdominal radiograph, attempt a full colonoscopic examination after cleansing the bowel with cathartics, perform an elective sigmoid colon resection

What is the recurrence rate for sigmoid volvulus without surgical intervention?

• ~50%

What is a cecal (cecocolic) volvulus?

• An axial rotation of the terminal ileum, cecum, and ascending colon with concomitant twisting of the associated mesentery from a lack of fixation of the cecum to the retroperitoneum

What might you see on plain abdominal radiographs with a cecal volvulus?

• A gas-filled comma shape with the concavity facing inferiorly and to the right (upside down comma sign), a circular shape with a narrow, triangular density pointing to the right and superiorly, a dilated cecum displaced to the left side of the abdomen

What is the treatment for a cecal volvulus?

• The procedure of choice is a right colectomy with primary anastomosis; if frankly gangrenous bowel, resect right colon and create an ileostomy; cecopexy is another option (higher recurrence rates)

What is the most common cause of large intestinal obstruction in the United States?

• Colorectal cancer

What is the most common cause of large intestinal obstruction in Russia, Eastern Europe, and Africa?

• Colonic volvulus (high-fiber diets)

What is a closed loop obstruction?

• An obstruction featuring the occlusion of the proximal and distal parts of the bowel

What is pseudo-obstruction of the colon otherwise known as?

• Ogilvie syndrome

What study should be performed in all stable patients with a suspected diagnosis of colonic pseudo-obstruction?

• Water-soluble contrast enema can reliably differentiate between mechanical obstruction and pseudo-obstruction; can consider colonoscopy

What is the treatment for Ogilvie syndrome?

• Initial treatment with nasogastric decompression, fluid replacement, correction electrolyte abnormalities, discontinuation of all medications that inhibit bowel motility, serial abdominal examinations and radiographs; consider administration of 2.5 mg of neostigmine given intravenously over 3 minutes after ruling out distal obstruction with water-soluble contrast enema or colonoscopy (do not give to patients with significant cardiac history and watch for bradycardia by monitoring patient with telemetry during administration of the drug with atropine immediately available); can consider colonoscopic decompression but high recurrence

What is the Law of Laplace?

• Tension is directly proportional to increased pressure times radius. Stated differently, for a given pressure, increased radius requires increased wall thickness to accommodate a stable wall tension; also, increased pressure requires increased thickness to maintain a stable wall tension.

• It is remembered by the following equation:

  T = ½ (P × R)/t

  (T = wall tension, P = pressure, R = radius, T = wall thickness)

  The law explains why the cecum, with its largest diameter, is the most common site of colonic rupture secondary to distal obstruction or increased pressure (eg, overzealous insufflations with excessive air during colonoscopy).

What layers of the bowel wall are affected by ulcerative colitis?

• Mucosa and submucosa

What is the sine qua non of ulcerative colitis?

• Rectal involvement (proctitis)

What diagnostic characteristics of ulcerative colitis help differentiate it from Crohn disease?

• Continuous, uninterrupted inflammation of the colonic mucosa beginning in the distal rectum and extending proximally (Crohn disease features normal segments of colon [skipped areas] interspersed between distinct segments of colonic inflammation), ulcerative colitis does not involve the terminal ileum, except with backwash ileitis; ulcerative colitis affects the mucosa and submucosa where Crohn can have transmural involvement

What 3 features are suggestive of a malignant stricture in the setting of ulcerative colitis?

• Stricture appears later in the course of ulcerative colitis; stricture is proximal to the splenic flexure and causes large bowel obstruction

What are the extraintestinal manifestations of ulcerative colitis?

• Arthritis, ankylosing spondylitis, erythema nodosum, pyoderma gangrenosum, primary sclerosing cholangitis

What extraintestinal manifestation of ulcerative colitis does not improve with colectomy?

• Primary sclerosing cholangitis, ankylosing spondylitis

What are the American Cancer Society guidelines regarding surveillance colonoscopy for ulcerative colitis patients?

• Colonoscopy every 1 to 2 years beginning 8 years after the onset of pancolitis

• 12 to 15 years after the onset of left-sided colitis

What classes of drugs are used in the treatment of ulcerative colitis?

• Aminosalicylates (sulfasalazine, mesalamine)

• Corticosteroids (prednisone)

• Immunosuppressive agents (azathioprine, cyclosporine)

What are indications for surgery in a patient with ulcerative colitis?

• Dysplasia-carcinoma, longstanding disease, intractability, massive colonic bleeding, toxic megacolon (may consider surgery for malnutrition/growth retardation in pediatric/adolescent patients), persistent obstruction or stricture, perforation

What is the treatment for toxic megacolon?

• Nasogastric decompression; IV hydration (with consideration given to IV hyperalimentation depending on length of illness before fulminant episode and patient's nutritional status); broad-spectrum IV antibiotics; high-dose IV steroids if patient is steroid-dependent; follow with serial abdominal exams and leukocyte counts, if deteriorates or if lack of improvement with medical therapy for 24–48 hours, perform an urgent procedure

What is the preferred operation for toxic megacolon?

• Total abdominal colectomy with ileostomy and preservation of the rectum

What is the procedure of choice in a patient with massive hemorrhage from ulcerative colitis?

• Subtotal colectomy; if severe bleeding from rectal mucosa, may also require emergency proctectomy

What are your options for elective surgery in patients with ulcerative colitis?

• Total proctocolectomy with ileostomy; restorative proctocolectomy with ileal pouch anal anastomosis; total proctocolectomy with a continent ileal reservoir (Kock pouch)

What are indications for surgery in a patient with Crohn disease?

• Cancer

• Fistula

• Fulminant colitis

• Growth retardation

• Intra-abdominal abscess

• Intractability

• Toxic megacolon

• Massive bleeding

• Intestinal obstruction

What operation would you perform for massive bleeding from Crohn disease?

• Abdominal colectomy and ileostomy versus ileorectal anastomosis if the rectum is not inflamed

What organisms should be evaluated for in a stool sample from a patient with suspected infectious colitis?

• Campylobacter jejuni, Yersinia enterocolitica, Salmonella typhi, Clostridium difficile

What is the most common form of intestinal ischemia?

• Colonic ischemia

What sign may be seen on radiographic imaging with intestinal wall edema or submucosal hemorrhage?

• Thumb printing

Which colonic segment is the most prone to ischemia?

• Splenic flexure and rectosigmoid junction (Griffith and Sudeck point)

What are indications for surgery with acute colonic ischemia?

• Peritoneal signs, massive bleeding, universal fulminant colitis with or without toxic megacolon

What are the Amsterdam criteria for Hereditary Nonpolyposis Colorectal Cancer (HNPCC)?

• "3,2,1"

• At least 3 first-degree relatives with colon cancer and all of the following:

• 2 successive generations affected

• At least 1 case of colon cancer diagnosed before age 50 years; familial adenomatous polyposis excluded

What is the difference between the Amsterdam criteria and the modified Amsterdam criteria?

• The modified Amsterdam criteria is almost the same as the Amsterdam criteria, except that with the modified Amsterdam criteria the cancer must be associated with HNPCC (colon, endometrium, small bowel, ureter, renal pelvis) instead of specifically colon cancer

What are the screening recommendations for patients with HNPCC?

• Colonoscopy at age 20 to 25 years and repeat every 1 to 3 years

• Transvaginal ultrasound or endometrial aspirate at age 20 to 25 years and repeat annually

What is the mainstay of the diagnosis of HNPCC?

• A detailed family history

What is the procedure of choice when colon cancer is detected in a patient with HNPCC?

• Abdominal colectomy with ileorectal anastomosis

• If the patient is female with no further plans for childbearing, prophylactic total abdominal hysterectomy and bilateral salpingo-oophorectomy are recommended

What are the screening recommendations for patients with familial adenomatous polyposis(FAP)/Gardner syndrome?

• Flexible proctosigmoidoscopy at age 10 to 12 years and repeat every 1 to 2 years until age 35, after age 35 repeat every 3 years

• Upper GI endoscopy every 1 to 3 years starting when polyps are first identified

What is the most commonly recommended procedure for the treatment of FAP syndrome?

• Restorative proctocolectomy with ileal pouch anal anastomosis with distal rectal mucosectomy

• Alternative includes total abdominal colectomy with ileorectal anastomosis

What percentage of patients with the adenomatous polyposis coli (APC) mutation express the gene?

• 100%

Do you have to worry about duodenal and ampullary polyps found in a patient with FAP syndrome?

• Yes, because the duodenal and ampullary polyps are usually neoplastic

• All large polyps should be removed with endoscopic polypectomy, and pancreatoduodenectomy (Whipple procedure) is indicated with ampullary cancer discovered at an early stage

How many juvenile polyps need to be present to make the diagnosis of familial juvenile polyposis?

• 10 juvenile polyps

What are the most common colonic polyps?

• Hyperplastic polyps

Are hyperplastic polyps considered to have malignant potential?

• No, but adenomatous changes can be found in hyperplastic polyps

What autosomal dominant syndrome is characterized by a combination of hamartomatous polyps of the intestinal tract and hyperpigmentation of the buccal mucosa, lips, and digits?

• Peutz-Jeghers syndrome

T or F: patients with Peutz-Jeghers syndrome are not at increased risk for the development of cancer?

• False; Peutz-Jeghers syndrome is associated with an increased risk for cancer throughout the intestinal tract, from the stomach to the rectum and extraintestinal malignancies (breast, ovary, cervix, fallopian tubes, thyroid, lung, gallbladder, bile ducts, pancreas, testicles)

What is the approximate lifetime risk of colon cancer in the general US population?

• 6%

The APC gene is located on what chromosome?

• Chromosome 5q21

What kind of gene is the APC gene?

• Tumor suppressor gene

What is the most frequently mutated tumor suppressor gene in human neoplasia?

• p53

On what chromosome can p53 be found?

• Chromosome 17p

On which chromosome can the ras proto-oncogene be found?

• Chromosome 12

What do right-sided colon cancers tend to do?

• Bleed

What do left-sided colon cancers tend to do?

• Obstruct

What is the gold standard for establishing the diagnosis of colon cancer?

• Colonoscopy

In patients with colon cancers causing a complete obstruction, what study can you order to establish the anatomic level of the obstruction when colonoscopy cannot be performed?

• A water-soluble contrast enema

What is the treatment for an obstructing cancer of the proximal colon?

• Right colectomy with primary anastomosis between the ileum and the transverse colon

What is the procedure of choice for a colon tumor involving the cecum, ascending colon, or the hepatic flexure?

• Right hemicolectomy

What is the procedure of choice for most transverse colon tumors?

• Extended right hemicolectomy

What is the procedure of choice for a descending colon tumor?

• Left hemicolectomy

What is the procedure of choice for a sigmoid colon tumor?

• Sigmoidectomy

When is abdominal colectomy for colon cancer indicated?

• Patients with multiple primary tumors

• Individuals with HNPCC

• Occasionally for patients with completely obstructing sigmoid cancers

According to the AJCC TNM Staging System for Colorectal Cancer, what is a Tis lesion?

• Carcinoma in situ: intraepithelial or invasion of lamina propria

According to the AJCC TNM Staging System for Colorectal Cancer, what is a T1 lesion?

• Tumor invades submucosa

According to the AJCC TNM Staging System for Colorectal Cancer, what is a T2 lesion?

• Tumor invades muscularis propria

According to the AJCC TNM Staging System for Colorectal Cancer, what is a T3 lesion?

• Tumor invades through the muscularis propria into the subserosa, or into nonperitonealized pericolic or perirectal tissues

According to the AJCC TNM Staging System for Colorectal Cancer, what is a T4 lesion?

• Tumor directly invades other organs or structures and/or perforates visceral peritoneum

According to the AJCC TNM Staging System for Colorectal Cancer, what is N0 nodal status?

• No regional lymph node metastasis

According to the AJCC TNM Staging System for Colorectal Cancer, what is N1 nodal status?

• Metastasis in 1 to 3 regional lymph nodes

According to the AJCC TNM Staging System for Colorectal Cancer, what is N2 nodal status?

• Metastasis in 4 or more regional lymph nodes

According to the AJCC TNM Staging System for Colorectal Cancer, what does M0 mean?

• No distant metastasis

According to the AJCC TNM Staging System for Colorectal Cancer, what does M1 mean?

• Distant metastasis

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage 0 colon cancer?

• Tis, N0, M0

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage I colon cancer?

• T1, N0, M0; T2, N0, M0

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage IIA colon cancer?

• T3, N0, M0

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage IIB colon cancer?

• T4, N0, M0

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage IIIA colon cancer?

• T1-2, N1, M0

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage IIIB colon cancer?

• T3-4, N1, M0

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage IIIC colon cancer?

• Any T, N2, M0

According to the AJCC TNM Staging System for Colorectal Cancer, what is a stage IV colon cancer?

• Any T, Any N, M1

What is the 5-year survival rate for patients who undergo appropriate resection of a T stage 1 colon cancer?

• ~95%

What is the 5-year survival rate for a patient with stage II colon cancer treated by appropriate surgical resection?

• ~80%

What is the survival rate for stage III cancer treated by surgery alone?

• ~65%

What is the 5-year survival rate for a patient with colon cancer with distant metastatic disease (stage IV)?

• <10%

What would you do if you found an isolated hepatic or pulmonary lesion while performing a right colectomy for colon cancer?

• Attempt to resect the isolated hepatic/pulmonary metastasis

What stage of colon cancer shows a clear benefit with chemotherapy?

• Stage III colon cancer

What is FOLFOX?

• Oxaliplatin, 5-fluorouracil, leucovorin regimen

What is Xeloda?

• Capecitabine (an oral fluoropyrimidine)

What is bevacizumab (Avastin)?

• A monoclonal antibody that is a vascular endothelial growth factor inhibitor

What is cetuximab (Erbitux)?

• A monoclonal antibody that binds to and inhibits the epidermal growth factor receptor (EGFR)

What percentage of colon cancer recurrences is detected within 2 years of the time of resection?

• ~85%