Gallbladder polyps

Outgrowths of the gallbladder mucosal wall

Pathophysiology

• See separate topic of 'gallbladder cancer' - suspected adenoma-carcinoma sequence involving polyps
• The only polypoid lesions that have malignant potential are adenomatous polyps

Classification

Benign

• • Cholesterolosis/cholesterol polyps
    • Accumulation of lipids in the mucosa of the gallbladder wall
    • Diffuse (cholesterolosis) or polypoid (cholesterol polyp) type
      • Diffuse type is usually diagnosed incidentally during cholecystectomy (9-26%)
      • Cholesterol polyp is the most common form of GB polyp
    • Results from abnormal deposits of triglycerides, cholesterol precursors, and cholesterol esters in the GB mucosa. The lipid accumulation creates yellow deposits which are visible macroscopically.
    • Polyps can form from cholesterol and lipid-filled macrophages, which can theoretically break off and cause symptoms akin to gallstones
    • Also called 'strawberry gallbladder' due to appearance of pits
  • Inflammatory
    • Uncommon
    • Appear as granulation and fibrous tissue
    • Usually <1cm
  • Adenomyomatosis
    • Hyperplasia of the mucosa and muscularis propria
    • Pathognomic epithelial invaginations forming cystic pockets (Rokitansky-Aschoff sinuses) which may contain calculi or cholesterol crystals
    • Can be diffuse, segmental or localised to the fundus of the gallbladder
    • Possibly secondary to chronic inflammation
    • Seen on USS as echogenic foci with comet tail artefacts

Neoplastic

• • Adenoma
    • Benign epithelial tumours composed of cells resembling biliary tract epithelium
    • Increasing risk of cancer with increasing polyp size
  • Fibroma
  • Lipoma
  • Leiomyoma

Predictors of malignancy

• Single polyp
• Sessile polyp
• Size >10mm
  • Risk of malignancy 43-77%
  • 128.2 GB cancers per 100,000 person-years
  • 1.3 per 100,000 person-years for polyps <6mm
• Age >60yo
• PSC
  • About half of polyps will have malignancy
• Indian ethnicity

Complications

• Risk of progression to cancer
• Unclear association with cholecystitis
• Cholecystitis seems to occur more commonly in patients with stones and polyps vs those with just stones

Indications for surgery

• Polyps > 1cm
• Radiographic evidence of vascular stalks
• Lower threshold for surgery in the setting of other prominent risk factors such as PSC

Non-operative management

• Surveillance of polyps not meeting resectability criteria
• Polyps 6-9mm without risk factors for malignancy:
  • USS at 6 months and 12 months
  • Then annual USS thereafter if stable
• Polyps <6mm
  • Repeat USS at least once, 12 months later, and then for consideration of further surveillance
  • However very low chance of harbouring malignancy if size is stable