Colon and Rectum Flashcards
What are the white lines of Toldt?
Lateral peritoneal reflections of the ascending and descending colon
What parts of the GI tract do not have a serosa?
Esophagus, middle and distal rectum
What are the major anatomic differences between the colon and the small bowel?
Colon has taeniae coli, haustra, and appendices epiploicae (fat appendages), whereas the small intestine is smooth
What is the blood supply to the proximal rectum?
Superior hemorrhoidal (or superior rectal) from the IMA
What is the blood supply to the middle rectum?
Middle hemorrhoidal (or middle rectal) from the hypogastric (internal iliac)
What is the blood supply to the distal rectum?
Inferior hemorrhoidal (or inferior rectal) from the pudendal artery (a branch of the hypogastric)
What is the venous drainage of the proximal rectum?
IMV to the splenic vein, then to the portal vein
What is the venous drainage of the middle rectum?
Iliac vein to the IVC
What is the venous drainage of the distal rectum?
Iliac vein to the IVC
What is colorectal carcinoma?
Adenocarcinoma of the colon or rectum
What is the incidence of colorectal carcinoma?
Most common GI cancer, second most common cancer in US
How common is colorectal carcinoma as a cause of cancer deaths?
Second most common cause of cancer deaths
What is the lifetime risk of colorectal carcinoma?
6%
What is the male:female ratio for colorectal carcinoma?
1:1
What are the risk factors for colorectal carcinoma?
Dietary (e.g. low-fiber, high-fat)
Genetic (e.g. FAP, Lynch’s syndrome)
IBD (e.g. UC > Crohn’s)
What is Lynch’s syndrome?
HNPCC = Hereditary NonPolyposis Colon Cancer.
AD inheritance of high risk for development of colon cancer.
What are current ACS recommendations for polyp/colorectal screening in asymptomatic patients without family history of colorectal cancer?
Starting at age 50, 1 of the following:
- Colonoscopy q10y
- Double contrast barium enema q5y
- Flex sigmoidoscopy q5y
- CT colonography q5y
What are the common recommendations for colorectal cancer screening if there is a history of colorectal cancer in a first-degree relative less than 60 years?
Colonoscopy at age 40, or 10 years before age at diagnosis of the youngest first-degree relative, and every 5 years thereafter
What percentage of adults will have a guaiac-positive stool test?
2%
What percentage of patients with a guaiac-positive stool test will have colon cancer?
10%
What signs and symptoms are associated with right-sided colon cancer?
May attain large size before presentation (as right side of bowel has a large luminal diameter).
Microcytic anemia, melena > hematochezia, postprandial discomfort, fatigue
What signs and symptoms are associated with left-sided colon cancer?
Change in bowel habits (small-caliber stools), colicky pain, signs of obstruction, abdominal mass, heme-positive or gross red blood, N/V, constipation
From which site of colon cancer is melena more common?
Right-sided colon cancer
From which site of colon cancer is hematochezia more common?
Left-sided colon cancer
What are the signs and symptoms of rectal cancer?
Most common symptom is hematochezia or mucus.
Tenesmus, feeling of incomplete evacuation of stool, rectal mass.
What is the incidence of rectal cancer?
Comprises 20-30% of all colorectal cancers
What is the differential diagnosis of a colon tumor or mass?
Adenocarcinoma, carcinoid tumor, lipoma, liposarcoma, leiomyoma, leiomyosarcoma, lymphoma, diverticular disease, UC, Crohn’s disease, polyps
Which diagnostic tests are helpful for colorectal cancer?
H&P; heme occult; CBC; barium enema; colonoscopy
What disease does microcytic anemia signify until proven otherwise in a man or postmenopausal woman?
Colon cancer
What tests help find colorectal cancer metastases?
CXR (lung); LFTs (live); abdominal CT (liver)
What is the preoperative workup for colorectal cancer?
H&P, LFTs, CEA, CBC, Chem 10, PT/PTT, T&C, CXR, UA, abdominopelvic CT
What are the means by which colorectal cancer spreads?
Direct extension (circumferentially and then through bowel wall to later invade other abdominoperineal organs);
Hematogenous (portal circulation to liver, lumbar/vertebral veins to lungs);
Lymphogenous (regional lymph nodes);
Transperitoneal;
Intraluminal
Is CEA useful in colorectal cancer?
Not for screening but for baseline and recurrence surveillance (but offers no proven survival benefit)
What unique diagnostic test is helpful in patients with rectal cancer?
Endorectal U/S
How are colorectal tumors staged?
TMN staging system
What is stage I colorectal cancer?
Invades submucosa or muscularis propria
What is stage II colorectal cancer?
Invades through muscularis propria or surrounding structures but with negative nodes
What is stage III colorectal cancer?
Positive nodes, no distant metastasis
What is stage IV colorectal cancer?
Positive distant metastasis
What is the approximate 5-year survival for colorectal cancer by stage?
I: 90%, II: 70%, III: 50%, IV: 10%
What percentage of patients with colorectal cancer have liver metastases on diagnosis?
20%
What is the preoperative bowel prep for colorectal cancer?
- Golytely colonic lavage or Fleets Phospho-Soda until clear effluent per rectum
- PO antibiotics (1 gm neomycin and 1 gm erythromycin, 3 doses)
What are the common preoperative IV antibiotics in colorectal cancer?
Cefoxitin, Unasyn
If the patient is allergic (hives, swelling), what antibiotics should be prescribed before surgery for colorectal cancer?
IV Cipro and Flagyl
What are the treatment options for colorectal cancer?
Resection (wide surgical resection of lesion and its regional lymphatic drainage)
What decides low anterior resection vs. abdominal perineal resection for colorectal cancer?
Distance from the anal verge and pelvis size
What do all rectal cancer operations include?
Total mesorectal excision (remove the rectal mesentery, including the lymph nodes)
What is the lowest LAR possible?
Coloanal anastomosis (anastomosis normal colon directly to anus)
What do some surgeons do with any anastomosis
Temporary ileostomy to protect the anastomosis
What surgical margins are needed for colon cancer?
Traditionally > 5 cm (margins must be at least 2 cm)
What is the minimal surgical margin for rectal cancer?
2 cm
How many lymph nodes should be resected with a colon cancer mass?
12 LN minimum
What is the adjuvant treatment of stage III colon cancer?
5-FU and leucovorin (or levamisole) chemotherapy
What is the adjuvant treatment for T3-4 rectal cancer?
Preoperative radiation therapy and 5-FU chemotherapy as a radiosensitizer
What is the most common site of distant (hematogenous) metastasis from colorectal cancer?
Liver
What is the treatment of liver metastases from colorectal cancer?
Resect with > 1 cm margins and administer chemotherapy if feasible
What is the surveillance regimen for colorectal cancer?
PE; stool guaiac; CBC; CEA; LFTs (q3m for 3 years, then q6m for 2 years); CXR (q6m for 2 years, then yearly); colonoscopy (at year 1 and 3); CT
Why is followup so important the first 3 years postoperative for colorectal cancer?
90% of colorectal recurrences are within 3 years of surgery
What are the most common cause of colonic obstruction in the adult population?
Colon cancer, diverticular disease, colonic volvulus
What is the 5-year survival rate after liver resection with clean margins for colon cancer liver metastasis?
33%
What is the 5-year survival rate after diagnosis of unresectable colon cancer liver metastasis?
0%
What are colorectal polyps?
Tissue growth into bowel lumen, usually consisting of mucosa, submucosa, or both
How are colorectal polyps anatomically classified?
Sessile (flat), pedunculated (on a stalk)
What is the histology of inflammatory polyps?
Similar to Crohn’s disease or UC
What is the histology of hamartomatous polyps?
Normal tissue in abnormal configuration
What is the histology of hyperplastic polyps?
Benign, normal cells with no malignant potential
What is the histology of neoplastic polyps?
Proliferation of undifferentiated cells (premalignant or malignant)
What are the subtypes of neoplastic polyps
Tubular adenomas (usually pedunculated), tubulovillous adenomas, villous adenomas (usually sessile and look like broccoli heads)
What determines malignant potential of an adenomatous polyp?
Size, histologic type, atypia of cells
What is the most common type of adenomatous polyp?
Tubular (85%)
What is the correlation between size and malignanta potential of an adenomatous polyp?
Polyps > 2 cm have a high risk of carcinoma (33-55%)
What is the correlation between histology and malignancy potential of an adenomatous polyp?
Villous > tubulovillous > tubular
Where are most polyps found?
Rectosigmoid
What are the signs and symptoms of colorectal polyps?
Bleeding (red or dark blood), change in bowel habits, mucus per rectum, electrolyte loss, totally asymptomatic
What are the diagnostic tests for colorectal polyps?
Colonoscopy, barium enema, sigmoidoscopy
What is the treatment for colorectal polyps?
Endoscopic resection (snared); Large sessile villous adenomas should be removed with bowel resection and lymph node resection
What is FAP?
Familial Adenomatous Polyposis
What are the characteristics of FAP?
Hundreds of adenomatous polyps within the rectum and colon that begin developing at puberty.
Untreated patients develop cancer by age 40-50.
What is the inheritance pattern of FAP?
AD
What is the genetic defect in FAP?
APC (adenomatous polyposis coli) gene
What is the treatment for FAP?
- Total proctocolectomy and ileostomy
2. Total colectomy and rectal mucosal removal (mucosal proctectomy) and ileoanal anastomosis
What are the characteristics of Gardner’s syndrome?
Neoplastic polyps of the small bowel and colon.
Cancer by age 40 in 100% of undiagnosed patients.
What are the associated findings with Gardner’s syndrome?
Desmoid tumors (in abdominal wall or cavity), osteomas of skull, sebaceous cysts, adrenal and thyroid tumors, retroperitoneal fibrosis, duodenal and periampullary tumors
How can the findings associated with Gardner’s syndrome be remembered?
Gardener planting SOD:
Sebaceous cysts, Osteomas, Desmoid tumors
What is a desmoid tumor?
Tumor of the musculoaponeurotic sheath, usually of the abdominal wall.
Benign, but grows locally.
Treated by wide resection.
What medications may slow the growth of a desmoid tumor?
Tamoxifen, sulindac, steroids
What is the inheritance pattern of Gardner’s syndrome?
AD, varying degree of penetrance
What is the treatment of colon polyps in patients with Gardner’s syndrome?
- Total proctocolectomy and ileostomy
2. Total colectomy and rectal mucosal removal (mucosal proctectomy) and ileoanal anastomosis
What are the characteristics of Peutz-Jegher’s syndrome?
Hamartomas throughout the GI tract (jejunum/ileum > colon > stomach)
What is the associated cancer risk from polyps in Peutz-Jegher’s syndrome?
Increased
What is the associated cancer risk for women with Peutz-Jegher’s syndrome?
Ovarian cancer (granulosa cell tumors is most common)
What is the inheritance pattern of Peutz-Jegher’s syndrome?
AD
What are the non-GI signs of Peutz-Jegher’s syndrome?
Melanotic pigmentation of buccal mucosa, lips, digits, palms, feet
What is the treatment for Peutz-Jegher’s syndrome?
If symptomatic (i.e. bleeding, intussusception, obstruction, > 1.5 cm), removal of polyps
What are juvenile polyps?
Benign hamartomas in the small bowel and colon.
Also called retention polyps.
What is Cronkhite-Canada syndrome?
Diffuse GI hamartoma polyps associated with malabsorption/weight loss, diarrhea, and loss of electrolytes/protein.
Signs include alopecia, nail atrophy, skin pigmentation.
What is Turcot’s syndrome?
Colon polyps with malignant CNS tumors (glioblastoma multiforme)
What is diverticulosis?
Condition in which false diverticula can be found within the colon, especially the sigmoid
What is the pathophysiology of diverticulosis?
- Weakness in the bowel wall develops at points where nutrient blood vessels enter between anti-mesenteric and mesenteric taeniae.
- Increased intraluminal pressures then cause herniation through these areas.
What is the incidence of diverticulosis?
50-60% by age 60 (10-20% symptomatic)
What is the most common site for diverticulosis?
Sigmoid colon (95%)
Who is at risk for diverticulosis?
Low-fiber diet, chronic constipation, family history
What are the symptoms and complications of diverticulosis?
Bleeding (may be massive), diverticulitis
What is the diagnostic approach to suspected diverticulosis with bleeding?
Colonoscopy
What is the diagnostic approach to suspected diverticulosis with pain and signs of inflammation?
Abdominal and pelvic CT
What is the treatment of diverticulosis?
High-fiber diet
What are the indications for operation with diverticulosis?
Complications of diverticulitis (e.g. fistula, obstruction, stricture); recurrent episodes; hemorrhage; suspected carcinoma; prolonged symptoms; abscess no drainable by percutaneous approach
With diverticulosis, when is it safe to get a colonoscopy, barium enema, or sigmoidoscopy?
Due to risk of perforation, this is performed 6 weeks after inflammation resolves to rule out colon cancer
What is diverticulitis?
Infection or perforation of a diverticulum
What is the pathophysiology of diverticulitis?
Obstruction of diverticulum by a fecalith leading to inflammation and microperforation
What are the signs and symptoms of diverticulitis?
LLQ pain (cramping or steady), change in bowel habits, diarrhea, fever, chills, anorexia, LLQ mass, N/V, dysuria
What are the associated lab finding with diverticulitis?
Increased WBCs
What are the associated radiographic findings with diverticulitis?
XR: ileus, partially obstructed colon, air-fluid levels, free air if perforated;
Abdominal/pelvic CT: swollen, edematous bowel wall
What are the associated barium enema findings with diverticulitis?
Should be avoided in acute cases!
Is colonoscopy safe in acute diverticulitis?
No, increased risk of perforation
What are the possible complications of diverticulitis?
Abscess, diffuse peritonitis, fistula, obstruction, perforation, stricture
What is the most common fistula with diverticulitis?
Colovesical fistula
What is the best test for diverticulitis?
CT
What is the initial therapy for diverticulitis?
IV fluids; NPO; broad-spectrum antibiotics with anaerobic coverage; NG suction
When is surgery warranted for diverticulitis?
Obstruction, fistula, free perforation, abscess no amenable to percutaneous drainage, sepsis, deterioration with initial conservative treatment
What is the lifelong risk of recurrence after the first episode of diverticulitis?
33%
What is the lifelong risk of recurrence after the second episode of diverticulitis?
50%
What are the indications for elective resection for diverticulitis?
2 episodes of diverticulitis.
Should be considered after the first episode in a young, diabetic, or immunosuppressed patient
What surgery is usually performed electively for recurrent bouts of diverticulitis?
One-stage operation:
Resection of involved segment and primary anastomosis
What type of surgery is usually performed for an acute case of diverticulitis with a complication?
Hartmann’s procedure:
Resection of involved segment with an end colostomy and stapled rectal stump (will need subsequent reanastomosis of colon usually after 2-3 postoperative months)
What is the treatment of diverticular abscess?
Percutaneous drainage (if abscess is not amenable to percutaneous drainage, then surgical approach for drainage is necessary)
How common is massive lower GI bleeding with diverticulitis?
Very rare (more associated with diverticulosis)
What are the most common causes of massive lower GI bleeding in adults?
Diverticulosis, vascular ectasia
What must you rule out in any patient with diverticulitis or diverticulosis?
Colon cancer
What is colonic volvulus?
Twisting of colon on itself about its mesentery, resulting in obstruction and, if complete, vascular compromise with potential necrosis, perforation, or both
What is the most common type of colonic volvulus?
Sigmoid volvulus
What is sigmoid volvulus?
Twist in the sigmoid colon
What are the etiologic factors for sigmoid volvulus?
High-residue diet resulting in bulky stools and tortuous, elongated colon; chronic constipation; laxative abuse; pregnancy; bedridden
What are the signs and symptoms of sigmoid volvulus?
Acute abdominal pain, progressive abdominal distention, anorexia, obstipation, cramps, N/V
What findings are evident with sigmoid volvulus on abdominal plain film?
Distended loop of sigmoid colon, often in the classic “bent inner tube” or “omega” sign with the loop aiming toward the RUQ
What are the signs of necrotic bowel in colonic volvulus?
Free air, pneumatosis (air in bowel)
How is the diagnosis of sigmoid volvulus made?
Sigmoidoscopy or radiographic exam with gastrografin enema
Under what conditions is gastrografin enema useful for sigmoid volvulus?
If sigmoidoscopy and plain films fail to confirm the diagnosis.
“Bird’s beak” is pathognomonic as seen on enema contrast study
What are the signs of strangulation with sigmoid volvulus?
Discolored or hemorrhagic mucosa on sigmoidoscopy; bloody fluid in the rectum; frank ulceration or necrosis at the point of the twist; peritoneal signs; fever; hypotension; increased WBCs
What is the initial treatment for sigmoid volvulus?
Non-operative; if there is no strangulation, sigmoidoscopic reduction is successful in 85% of cases (enema study with occasionally reduce)
What is the percentage of recurrence after non-operative reduction of a sigmoid volvulus?
40%
What are the indications for surgery for sigmoid volvulus?
Strangulation is suspected or non-operative reduction is unsuccessful.
Most patients should undergo Hartmann’s procedure during same hospitalization of redundant sigmoid after successful non-operative reduction because of high recurrence rate
What is cecal volvulus?
Twisting of the cecum upon itself and the mesentery
What is a cecal bascule volvulus?
Instead of the more common axial twist, the cecum folds upward (lies on the ascending colon)
What is the incidence of cecal volvulus?
25% of colonic volvulus
What is the etiology of cecal volvulus?
Idiopathic, poor fixation of the right colon
What are the signs and symptoms of cecal volvulus?
Acute onset of abdominal or colicky pain beginning in the RLQ and progressing to a constant pain, vomiting, obstipation, abdominal distention, and SBO
How is the diagnosis of cecal volvulus made?
AXR: dilated, ovoid colon with large air/fluid level in the RLQ often forming the classic “coffee bean” sign with the apex aiming toward the epigastrium or LUQ
What diagnostic studies should be performed with cecal volvulus?
Water-soluble contrast study (gastrografin), if diagnosis cannot be made by AXR
What is the treatment for cecal volvulus?
Emergent surgery:
Right colectomy with primary anastomosis or ileostomy and mucous fistula (primary anastomosis may be performed in stable patients)
What are the major differences in the emergent management of cecal volvulus vs. sigmoid?
Patients with cecal volvulus require surgical reduction, whereas the vast majority of patients with sigmoid volvulus undergo initial endoscopic reduction
