Atlas of pathophysiology, 2 Edition

Part II - Disorders

Gastrointestinal Disorders

Colonic Polyps

A polyp is a small tumorlike growth that projects from a mucous membrane surface. Types of polyps include common polypoid adenomas, villous adenomas, hereditary polyposis, focal polypoid hyperplasia, and juvenile polyps (hamartomas). Most rectal polyps are benign; however, villous and hereditary polyps tend to become malignant. Indeed, a striking feature of familial polyposis is its strong association with rectosigmoid adenocarcinoma.

Age Alert

Juvenile polyps, usually occurring among children under age 10, are characterized by rectal bleeding. Villous adenomas are most prevalent in men over age 55; common polypoid adenomas, in white women between ages 45 and 60. Incidence of nonjuvenile polyps rises after age 70 in both sexes.

Causes

Unknown

Predisposing factors

·   Heredity

·   Age

·   Infection

·   Diet

·   Sedentary lifestyle

Pathophysiology

Colonic polyps are masses of tissue resulting from unrestrained cell growth in the upper epithelium that rise above the mucosal membrane and protrude into the GI tract.

Polyps may be described by their appearance: pedunculated (attached by a stalk to the intestinal wall) or sessile (attached to the wall with a broad base and no stalk).

Signs and symptoms

·   Usually asymptomatic; discovered incidentally during a digital examination or rectosigmoidoscopy

·   Rectal bleeding (high rectal polyps leave a streak of blood on the stool, whereas low rectal polyps bleed freely)

·   Painful defecation

·   Diarrhea

Clinical Tip

Although most are asymptomatic, polyps may cause symptoms by virtue of their protrusion into the bowel lumen. They may bleed, cause abdominal pain, or actually obstruct the intestine.

Diagnostic test results

·   Barium enema identifies polyps high in the colon.

·   Fecal occult blood test is positive.

·   Blood studies reveal decreased hemoglobin level and hematocrit.

·   Proctosigmoidoscopy or colonoscopy and rectal biopsy confirm the presence of the polyps.

·   Serum analysis reveals electrolyte imbalances (villous adenomas).

Treatment

Common polypoid adenomas

·   Less than 1 cm in size—polypectomy, commonly by fulguration during endoscopy

·   Over 4 cm—abdominoperineal resection or low anterior resection

Invasive villous adenomas

·   Abdominoperineal resection

·   Low anterior resection

Focal polypoid hyperplasia

·   Obliterated by biopsy

Hereditary polyps

·   Total abdominoperineal resection with permanent ileostomy

·   Subtotal colectomy with ileoproctostomy

·   Ileoanal anastomosis

Juvenile polyps

·   Often autoamputate

·   Snare removal during colonoscopy

P.167

POLYPS WITHIN THE COLON

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