Polyps, Colonic

Essentials of Diagnosis

• Discrete mass lesions that are flat or protrude into the intestinal lumen

• Most commonly sporadic, may be inherited as part of familial polyposis syndrome

• Of polyps removed at colonoscopy, over 75% are adenomatous; most of the remainder are serrated; distinguished by histology

General Considerations

• Four major pathological groups

  • Mucosal adenomatous polyps (tubular, tubulovillous, villous)

  • Mucosal serrated polyps (hyperplastic, sessile serrated polyp, traditional serrated adenoma)

  • Mucosal nonneoplastic polyps (juvenile polyps, hamartomas, inflammatory polyps)

  • Submucosal lesions (lipomas, lymphoid aggregates, carcinoids, pneumatosis cystoides intestinalis)

• Adenomas and serrated polyps may be flat, sessile, or pedunculated (containing a stalk)

  • They are present in more than 30% of men and 20% of women over the age of 50

  • Their significance is that over 95% of cases of adenocarcinoma of the colon are believed to arise from these lesions

• Sessile serrated lesions (prevalence 5–15%) and traditional serrated adenomas (prevalence < 1%) may harbor an increased risk of colorectal cancer similar or greater to that of adenomas

• Small hyperplastic polyps (< 5 mm) located in the rectosigmoid region are of no consequence, except that they cannot reliably be distinguished from adenomatous lesions other than by biopsy

• Diminutive hyperplastic polyps (< 5 mm) are extremely common (prevalence 20–30%), especially in the rectum, and believed to be without significant risk

Symptoms and Signs

• Usually asymptomatic

• Chronic occult blood loss may lead to iron deficiency anemia

• Large polyps may ulcerate, resulting in intermittent hematochezia

Differential Diagnosis

• Colorectal cancer

• Nonneoplastic polyp, eg, hyperplastic, inflammatory

• Submucosal polyp, eg, lipoma, lymphoid aggregate

• Other causes of occult gastrointestinal bleeding, eg, arteriovenous malformation, inflammatory bowel disease

Laboratory Tests

• Fecal occult blood test (FOBT), fecal immunochemical test (FIT), and fecal DNA tests

• FIT is more sensitive than prior guaiac-based FOBT for the detection of colorectal cancer and advanced adenomas

• Combination fecal DNA and FIT for stool hemoglobin (proprietary name: "Cologuard"); in a prospective comparative trial

  • Sensitivity for colorectal cancer for "Cologuard" was 92.3% compared to 73.8% for FIT

  • Sensitivity for large (> 1 cm) adenomas or serrated polyps for "Cologuard" was 42.4% compared to 23.8% for FIT

Imaging Studies

• CT colonography ("virtual colonoscopy")

  • Has a sensitivity of ≥ 90% for the detection of polyps > 10 mm in size

  • However, the accuracy for detection of polyps 5–9 mm in size is significantly lower (sensitivity 50%)

• Barium enema is no longer recommended due to its poor diagnostic accuracy

Diagnostic Procedures

• Colonoscopy is best means of detecting and removing adenomatous polyps

• Capsule endoscopy of the colon

  • Has an 86% sensitivity and 88% specificity for detection of adenomas > 6 mm compared with colonoscopy

  • Has 29% sensitivity and 33% specificity for sessile serrated polyps

  • May be considered in patients with an incomplete colonoscopy or those who are unsuitable or unwilling to undergo colonoscopy

Surgery

• Primary surgical resection may be required for large (> 2–3 cm) sessile polyps

• Malignant polyps are adenomas that appear grossly benign at endoscopy but on histologic assessment are found to contain cancer

• Malignant polyps are adequately treated by polypectomy alone if the polyp is completely excised and is well differentiated, the margin is not involved, and there is no vascular or lymphatic invasion

• Risk of residual cancer or nodal metastasis with favorable histologic features is < 1%

• "Unfavorable" malignant polyps are treated by surgical resection

Therapeutic Procedures

• Colonoscopic polypectomy is possible for most polyps, particularly pedunculated polyps

Follow-Up

• Periodic colonoscopic surveillance is recommended to detect "metachronous" adenomas

• Obtain colonoscopy

  • In 5–10 years for patients with 1–2 small (< 1 cm) tubular adenomas (without villous features or high-grade dysplasia)

  • In 3 years for patients with 3–10 adenomas, an adenoma > 1 cm, or an adenoma with villous features or high grade dysplasia

  • In 1–2 years for patients with > 10 adenomas; consider evaluating these patients for a familial polyposis syndrome

Complications

• Complications of colonoscopic polypectomy include perforation in 0.2%, bleeding in 0.3–1%

Prevention

• Nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, and cyclooxygenase (COX)-2 selective NSAID (celecoxib) may decrease the incidence of colorectal adenomas and the progression to cancer; however, due to their other side effects, routine prophylaxis with these agents is not currently recommended