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Colonic Polyps

Basics

  • Intraluminal tissue growth; mostly sporadic or polyposis syndromes.
  • Size: diminutive ≤5 mm; small 6–9 mm; large ≥10 mm.
  • Morphology: depressed, flat, sessile, pedunculated.

  • 95% of colonic adenocarcinomas arise from polyps.

Epidemiology

  • More common in non-Caucasian men in Western countries.
  • Incidence increases with age.
  • Prevalence: 15-20% adults; 30% adults >50 years; 6% children; 12% children with lower GI bleed.

Etiology & Pathophysiology

  • Mucosal:
  • Neoplastic: adenomatous polyps (tubular >80%, villous 5-15%, tubulovillous 5-15%).
  • Serrated polyps: sessile serrated polyps (SSPs) common in proximal colon, malignant potential if dysplastic; traditional serrated adenoma rare, distal colon, high malignant potential.
  • Nonneoplastic: hyperplastic, juvenile, hamartomas, inflammatory pseudopolyps.
  • Submucosal: lipomas, lymphoid aggregates, carcinoids.
  • Genetics:
  • APC mutations in FAP (autosomal dominant).
  • MUTYH mutations in MUTYH-associated polyposis (autosomal recessive).
  • Juvenile polyposis syndrome (JPS) mutations in SMAD4/BMPR1A.
  • Inactivation of tumor suppressor and mismatch repair genes causes progression.

Risk Factors

  • Family history of polyposis or CRC.
  • Age, male sex.
  • High-fat, low-fiber diet; smoking; heavy alcohol (>8 drinks/week).
  • IBD associated with decreased polyps but increased CRC risk.

Prevention

  • Low-fat, high-fiber diet.
  • Avoid smoking, reduce alcohol.
  • NSAIDs and calcium may reduce incidence and recurrence.

Associated Conditions

  • Hereditary syndromes: FAP (classic, attenuated), MAP, Gardner, Turcot syndromes.
  • Hamartomatous syndromes: Peutz-Jeghers, JPS, Cowden syndrome.

Diagnosis

History

  • Usually asymptomatic.
  • May have painless rectal bleeding, diarrhea, mucus, constipation, abdominal pain.
  • Chronic bleeding may cause iron-deficiency anemia.
  • McKittrick-Wheelock syndrome: large secretory villous adenoma causing severe diarrhea, electrolyte imbalance.

Physical Exam

  • Usually normal.
  • Rectal polyps may be prolapsed or palpable on DRE.

Tests

  • CBC: anemia if chronic bleeding.
  • Metabolic panel: electrolyte abnormalities with secretory adenomas.
  • FOBT (gFOBT, FIT) and stool DNA testing; stool DNA more sensitive, less specific.
  • Colonoscopy: gold standard, allows polypectomy.
  • CT colonography: less sensitive for flat polyps, requires excellent prep.
  • Advanced endoscopic imaging: narrow-band imaging (NBI), i-scan, FICE, confocal laser endomicroscopy (CLE).
  • Genetic testing for >10 adenomas.

Histopathology

  • Tubular adenomas: polypoid, dysplastic epithelium, tubular structure.
  • Villous adenomas: sessile, fingerlike projections, dysplasia.
  • Tubulovillous adenomas: mixed features.
  • Hyperplastic: hyperplastic mucosa.
  • Juvenile polyps: pedunculated, smooth, red, 1-3 cm.

Treatment

  • Polypectomy:
  • Snare polypectomy with electrocautery for pedunculated.
  • Endoscopic mucosal resection for sessile.
  • Endoscopic submucosal dissection.
  • Surgery:
  • Total colectomy with ileorectal anastomosis or proctocolectomy with ileal pouch anal anastomosis in polyposis syndromes.
  • Chemoprevention with NSAIDs and calcium for FAP and MAP.

Follow-Up

  • Colonoscopy intervals based on polyp number, size, and histology:
  • 10 years if no polyps or small distal hyperplastic (<10 mm).
  • 3-5 years for hyperplastic ≥10 mm.
  • 7-10 years for 1-2 small tubular adenomas <10 mm.
  • 3-5 years for 3-4 small tubular adenomas <10 mm.
  • 3 years for 5-10 small tubular adenomas <10 mm.
  • 1 year for >10 adenomas.
  • 3 years for adenomas ≥10 mm, villous/tubulovillous histology, or high-grade dysplasia.
  • 6 months for adenoma or SSP ≥20 mm with piecemeal resection.
  • Genetic screening for mutation carriers; start young depending on syndrome.

Diet

  • Low-fat, high-fiber diet recommended (insufficient evidence).

Patient Education

  • Importance of colonoscopy screening.
  • Risk factors for progression to cancer: adenomatous or serrated histology, high-grade dysplasia, villous features, size >1 cm, proximal location, multiple polyps.

Prognosis

  • Small hyperplastic polyps may regress or remain unchanged.
  • Recurrence low (<10%) after polypectomy.
  • Juvenile polyps recur in 17-45% of cases with multiple polyps.

Complications

  • Malignant transformation.
  • Polypectomy risks: bleeding (2-11%), perforation (0-1%).
  • Colonoscopy complications related to procedure and anesthesia.

Clinical Pearls:

  • Colonoscopy is gold standard for diagnosis and removal.
  • Biopsy small hyperplastic polyps to differentiate adenomatous vs serrated.
  • NSAIDs and calcium may reduce polyp incidence and recurrence.
  • Polyp to carcinoma progression takes years.