Polyps, Colonic

Key Features

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

Clinical Findings

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

Diagnosis

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 ...