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TABLE 13-3 Stage and Prognosis of Colorectal Cancer

 

Stage Dukes ClassificationT Level

N Level

M LevelCure Rate

 

 

0

—

Tis

N0

M0

100%

 

 

 

 

 

 

 

 

 

 

I

A

T1 or T2

N0

M0

90%

 

 

 

 

 

 

 

 

 

 

II

B

T3 or T4

N0

M0

80%

 

 

 

 

 

 

 

 

 

 

III

C

Any T

N1, N2, or N3

M0

60%

 

 

 

 

 

 

 

 

 

 

IV

D

Any T

Any N

M1

5%

 

 

 

 

 

 

 

 

 

 

T, tumor; N, regional lymph nodes; M, distant metastases.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E

Other neoplasms may arise from normal colorectal tissues but are rare, including:

1.Lymphoid tissue (lymphoma and lymphosarcoma)

2.Adipose tissue (lipoma and liposarcoma)

3.Muscle tissue (leiomyoma and leiomyosarcoma)

V Diverticular Disease

ATerminology

1.Diverticulum: abnormal sac or pouch protruding from the wall of a hollow organ (e.g., the colon)

2.True diverticulum: diverticulum composed of all layers of bowel wall (rare in the colon)

3.False diverticulum: diverticulum lacking a portion of the bowel wall (common)

4.Diverticula: more than one diverticulum

5.Diverticulosis: the presence of diverticula

6.Diverticulitis: infection associated with diverticula

BEpidemiology and etiology

1.Diverticulosis is a disease of modern times.

a.It was not recognized until after the Industrial Revolution (1880).

b.Its appearance seems to be related to processing wheat flour in a roller mill and reducing fiber in the diet.

2.It is common in Western societies and rare in unindustrialized nations.

3.Populations who eat high-fiber, low-sugar foods (e.g., sub-Saharan Africans) have a low incidence of diverticulosis.

4.The incidence of this acquired disorder increases with age.

a.Diverticulosis is rare in persons younger than 30 years of age.

b.It is present in 75% of people older than 80 years.

CPathogenesis

1.Diverticula are herniations of mucosa through the colonic wall.

a.They occur at sites where arterioles traverse the wall.

b.These herniations lack a muscular layer: They are false diverticula.

2.The sigmoid colon is the most common site for diverticula.

a.Diverticula occur with decreasing frequency in the descending, transverse, and ascending colon.

b.It is rare for diverticula to occur in the rectum.

3.Increased intraluminal pressure in the colon, which is thought to be associated with a low-fiber diet, has been proposed as the cause of mucosal herniation.

a.Segmentation of isolated areas of colon can produce high pressures.

P.232

b.By Laplace's law, P = T/R, the highest pressure across the colon wall occurs in the sigmoid colon, which has the smallest radius in the colon.

4.Muscular hypertrophy of the colon wall often accompanies diverticula and is especially common in the involved sigmoid colon.

5.The diverticula are in close proximity to arterioles that traverse the colon wall.

D

Diverticulitis is caused by a perforation of one or more diverticula.

1.The perforation occurs in the sigmoid colon in more than 90% of cases.

2.Extravasation of colonic bacteria results in a pericolic infection.

3.A wide spectrum of disease is possible, ranging from:

a.Localized cellulitis, which is a pericolic phlegmon

b.An intra-abdominal abscess

c.Generalized purulent peritonitis (from ruptured abscess)

d.Feculent peritonitis (persistent leakage of feces from the perforation)

e.Fistula formation, including fistulas from the colon to the bladder, vagina, skin, or other sites

4.Clinical presentation is variable, depending on the location of the perforation and the extent of the infection.

a.Left lower abdominal pain is the most common symptom. Pain may radiate to the suprapubic area, groin, or back.

b.Abdominal or pelvic mass may be caused by a phlegmon or abscess.

c.Fever and leukocytosis are common.

d.Associated ileus may cause small bowel distention and vomiting.

e.Generalized peritonitis may be present in severe cases.

f.Pneumaturia, dysuria, pyuria, or fecaluria may be caused by colovesical fistula. Similarly, colovaginal fistula may be accompanied by vaginal drainage of pus or stool.

5.Initial evaluation

a.A CT scan of the abdomen and pelvis is the most helpful test to confirm the suspected diagnosis of diverticulitis.

1.If intravenous contrast is given before the CT scan, the kidneys and ureters can be evaluated simultaneously, and intravenous pyelography (IVP) is not usually necessary.

2.If an abscess is revealed, it may be amenable to CT-guided percutaneous drainage.

3.Air in the bladder is highly suggestive of colovesical fistula.

4.Contrast enema should generally be avoided if diverticulitis is suspected; hydrostatic pressure can worsen the situation by causing extravasation of contrast and feces through the perforation.

b.Chest radiography. Subdiaphragmatic air is detected in fewer than 3% of cases of diverticulitis.

c.The leukocyte count should be obtained initially as a baseline and serially to evaluate the response to treatment.

d.Frequent abdominal examinations are necessary to determine the activity of the disease.

6.Subsequent evaluation. After the patient's condition has stabilized and signs of sepsis have subsided, further evaluation may be necessary.

a.Colonoscopy may be indicated to exclude a sigmoid cancer.

b.Barium enema is less useful than colonoscopy because small tumors may be masked by diverticula and may not be detected by barium enema.

c.Cystoscopy should be done if a colovesical fistula is suspected to determine the probable site of the fistula.

7.Treatment depends on the severity of the disease, the number of previous attacks, the presence of complications, and the overall condition of the patient.

a.Initial treatment for a phlegmon of the sigmoid colon includes:

1.Intravenous fluids

2.Nothing orally (a nasogastric tube is placed if ileus is present)

3.Broad-spectrum intravenous antibiotics

P.233

b.Treatment if an intra-abdominal abscess is present

1.Intravenous fluids

2.Nothing orally (a nasogastric tube is placed if ileus is present)

3.Broad-spectrum intravenous antibiotics

4.Drainage of the abscess, preferably by percutaneous drainage using CT guidance

c.Treatment for purulent or feculent peritonitis

1.Administration of fluid and antibiotics

2.Resection of the diseased segment of bowel (if possible)

3.Closure of rectal stump and construction of colostomy (Hartmann's operation)

a.It is not safe to make an anastomosis in the presence of severe infection.

b.The colostomy can be taken down, and the colon can be anastomosed to the rectum after the patient has recovered from the illness and surgery, which is usually at least 10 weeks later.

d.Treatment for recurrent attacks of diverticulitis

1.Sigmoidectomy and primary colorectal anastomosis

2.Considerable clinical judgment is required to determine indications.

a.Young patients with a single severe attack may warrant elective surgery to prevent another attack, because this group of patients has a very high incidence of complicated diverticulitis.

b.Elderly patients should probably not have surgery unless more than one episode of diverticulitis has occurred.

c.The chance of recurrent episodes of diverticulitis after a single, uncomplicated episode is approximately 10%.

d.The chance of recurrent episodes after a complicated episode of diverticulitis (with abscess formation) is probably higher than 30%.

e.The risk of complications increases with subsequent episodes of diverticulitis.

e.Treatment for fistulas caused by diverticulitis

1.Treat initially with antibiotics to allow acute inflammation to resolve.

2.Sigmoidectomy and primary colorectal anastomosis

a.Excising the diseased sigmoid colon with anastomosis is usually possible if acute inflammation has resolved.

b.If considerable inflammation persists, Hartmann's operation is indicated. The colostomy can be closed at a later date, as discussed previously (Chapter 13, V D 7 c).

8.Surgical treatment of diverticulitis

a.Abscesses should be drained by percutaneous, transvaginal, or transrectal route, if possible.

1.Laparotomy for abscess drainage risks spreading infection throughout the peritoneal cavity, and a colostomy almost always is required in such cases.

2.If the abscess can be successfully drained, the patient usually recovers sufficiently to permit a singlestage sigmoidectomy with colorectal anastomosis.

b.If there is significant pelvic inflammation, ureteral catheters may be placed prior to surgery to assist intraoperative location of the left ureter.

c.All hypertrophied muscular colon should be removed.

d.The anastomosis should be made at the level of the rectum.

1.The distal sigmoid colon almost always has a hypertrophied muscular wall, which should not be incorporated into the anastomosis (this is thought to be a cause of recurrence).

2.The rectum is almost never involved in diverticular disease.

e.It is not necessary to remove all segments of colon containing diverticula; only the hypertrophied muscular segment (which is usually confined to the sigmoid) must be removed.

E

Hemorrhage is the other major complication of diverticular disease.

1.An arteriole adjacent to a diverticulum may disrupt, causing massive bleeding. Such bleeding is most frequent in elderly patients.

2.Presentation. Abdominal pain is rare; patients usually pass large amounts of bright-red blood via the rectum. Rapid blood loss may result in shock.

P.234

3.Diagnostic tests that accompany resuscitation

a.Preparation. A crystalloid solution is administered intravenously. Blood is transfused, if required, for hemodynamic stabilization. A nasogastric tube is passed to rule out gastroduodenal hemorrhage.

b.Proctoscopy is done to rule out anorectal hemorrhage (from hemorrhoids or rectal varices).

c.Coagulation studies (e.g., prothrombin time [PT], partial thromboplastin time [PTT], platelets) are obtained, and clotting factors are corrected if they are abnormal.

d.A nuclear scan (labeled red blood cell scan) is obtained if the patient's condition permits.

e.A mesenteric arteriogram is indicated if the nuclear scan indicates the site of bleeding.

1.If the mesenteric arteriogram shows the site of bleeding, vasopressin can be infused through the mesenteric catheter to constrict the mesenteric artery and lower portal pressure. This infusion stops 90% of diverticular hemorrhages.

2.If bleeding persists and the mesenteric arteriography has shown the site of hemorrhage, a segmental colectomy is indicated.

3.If bleeding persists and the site cannot be detected by arteriography, a total abdominal colectomy with ileostomy is indicated.

VI Angiodysplasia

A

This acquired vascular lesion joins diverticulosis as a major cause of colonic hemorrhage. Other names for this entity include angiectasis, arteriovenous malformation, and vascular ectasis.

1.These acquired vascular lesions occur most commonly in the right colon.

2.They rarely occur in persons before 40 years of age, and they increase in frequency with age.

3.It has been suggested that the lesions are the result of chronic, intermittent obstruction of the submucosal veins.

a.This chronic obstruction results eventually in incompetence of the precapillary sphincters, which in turn causes small arteriovenous communications within the bowel wall.

b.These lesions are probably present in most people older than 70 years of age. The reason why some lesions bleed, whereas most do not, remains unknown.

4.Hemorrhage from angiodysplasia tends to be slower than that from diverticulosis. Stools may be melanotic or bright red, depending on the rate of hemorrhage.

B

Evaluation and treatment are similar to those for a patient with bleeding diverticulosis. However, angiodysplasia tends to bleed intermittently, whereas diverticular bleeding is caused by an arteriolar disruption with massive bleeding that does not usually recur after it ceases.

1.Some angiodysplastic lesions can be detected by colonoscopy as “cherry-red spots” on the mucosa. These lesions may be eradicated by endoscopic electrocoagulation.

2.If the bleeding persists or recurs and can be isolated to a colonic segment by nuclear scans, arteriography, or colonoscopy, segmental colectomy is indicated.

3.If the bleeding persists and the site cannot be identified, total abdominal colectomy with ileostomy may be required as a lifesaving measure.

VII Inflammatory Bowel Disease

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