Polypen der Gallenblase

Gallbladder polyps are elevated lesions on the mucosal surface of the gallbladder. The vast majority are benign, but malignant forms are seen.

On imaging, although they may be detected by CT or MRI, they are usually best characterized on ultrasound as a non-shadowing and immobile polypoid ingrowth into gallbladder lumen.

Epidemiology

Gallbladder polyps are relatively frequent, seen in up to 9% of the population . Over 90% are benign, and the majority are cholesterol polyps.

Cholesterol polyps are most frequently identified in patients between 40-50 years of age and are more common in women (F:M, 2.9:1) .

Clinical presentation

Typically gallbladder polyps are incidentally found on upper abdominal imaging, usually during imaging for upper abdominal discomfort. Unless large, polyps are asymptomatic .

Pathology

A wide variety of entities appear as polyps and histology is variable:

• benign polyps: 95% of all polyps
  • cholesterol polyps: >50% of all polyps
  • adenoma: ~30%, possibly premalignant
  • inflammatory polyps: ~10%
  • other rare entities (see benign tumors and tumor-like lesions of the gallbladder)
• malignant polyps: 5% of all polyps
  • adenocarcinoma: ~90% of malignant polyps
  • other rare entities including
    • metastases to gallbladder
    • squamous cell carcinoma
    • angiosarcoma

Associations

Patients with Peutz-Jeghers syndrome have an increased prevalence of adenomas within the gallbladder.

Radiographic features

In most instances, predicting histology based purely on imaging is not possible, with the possible exception of cholesterol polyps in some instances (see below), and thus features that are predictive of benign vs malignant disease should be noted (see benign vs malignant features of gallbladder polyps) .

Overall size is probably the most useful indicator of malignancy, with polyps over 10 mm in diameter having a reported malignancy rate of 37-88% .

Ultrasound

Ultrasound is the best initial imaging choice and is often able to separate cholesterol polyps from those requiring treatment. General features of gallbladder polyps are a non-shadowing polypoid ingrowth into gallbladder lumen, which is usually immobile unless there is a relatively long pedunculated component.

General features of polyps include :

• small size 
  • as cholesterol polyps are the most frequent, over 90% are <10 mm, the vast majority less than <5 mm
  • adenomas or malignant lesions tend to be larger
• echogenicity varies with the size
  • small polyps are echogenic but non-shadowing
  • larger cholesterol polyps tend to be hypoechoic
• morphology
  • small polyps may be adherent to the wall and smooth
  • larger lesions tend to be pedunculated and granular in outline

Adenomas, on the other hand, tend to be larger, solitary, more often sessile with internal vascularity, and of intermediate echogenicity. It is impossible to confidently distinguish an adenoma from an adenocarcinoma .

Rarely, endoscopic ultrasound may be useful to further assess gallbladder polyps as it may generate higher resolution images .

High resolution ultrasound 

Some publications have suggested a useful role in high resolution ultrasound (HRUS) for categorization of gallbladder polyps with features favoring a neoplastic polyps from benign comprising of :

• size greater than 1 cm
• single polyp (verses multiple)
• lobulated surface contour
• presence of a vascular core seen on color Doppler
• hypoechoic internal echo of the polyp
• hypoechoic foci within the polyp

CT

CT is often unable to detect small gallbladder polyps. Larger polyps will appear as soft tissue attenuation projections into the lumen of the gallbladder and will demonstrate enhancement similar to that of the rest of the gallbladder. More intense enhancement should be viewed with suspicion, as it is associated with increased vascularity in malignancy.

Treatment and prognosis

European guidelines (2017)

In 2017 joint guidelines between the European Society of Gastrointestinal and Abdominal Radiology (ESGAR), European Association for Endoscopic Surgery and other Interventional Techniques (EAES), International Society of Digestive Surgery - European Federation (EFISDS) and European Society of Gastrointestinal Endoscopy (ESGE) were published and provide the most up to date and comprehensive guidance :

• polyp >10 mm: increased risk of malignancy, cholecystectomy recommended
• polyp <10 mm
  • symptoms attributed to the gallbladder: cholecystectomy suggested if no other cause for the symptoms determined (polyp may be indicative of underlying occult calculus or inflammation)
  • if the patient has risk factors* for gallbladder malignancy:
    • polyp <6 mm
      • follow-up ultrasound at 6 months, then yearly for 5 years
      • an increase in size ≥2 mm: consider cholecystectomy
    • polyp >6 mm: consider cholecystectomy
  • no risk factors for gallbladder malignancy:
    • polyp <6 mm: follow-up ultrasound at 1, 3 and 5 years
    • polyp >6 mm:
      • follow up ultrasound at 6 months, then yearly for 5 years
      • an increase in size ≥2 mm: consider cholecystectomy

*risk factors: >50 years, primary sclerosing cholangitis, Indian ethnicity, sessile polyp (including focal wall thickening >4 mm)

Statistically, gallbladder polyps are common and gallbladder cancer is rare, so very few polyps progress to gallbladder cancer. There is also controversy regarding the development of gallbladder cancer and some suggest that polyps may not actually progress to cancer .

American College of Radiology guidelines (2013)

According to the White Paper of the ACR Incidental Findings Committee II on Gallbladder and Biliary Findings (2013) :

• ≤6 mm: no further evaluation or follow up necessary
• 7-9 mm: yearly follow up with ultrasound to ensure no interval growth
• ≥10 mm: surgical consultation for cholecystectomy
  • if no cholecystectomy, annual follow up is justified

Lower thresholds for follow up or intervention may be warranted if the patient population is known to have a higher risk of gallbladder carcinoma (e.g. higher incidences in Pakistan, Ecuador, and females in India).

Differential diagnosis

The differential for a gallbladder polyp is limited, and includes :

• gallstones
  • usually mobile, but can be adherent
  • usually cast an acoustic shadow
• biliary sludge
  • tumefactive sludge
• adenomyomatosis
• gallbladder carcinoma
• gallbladder metastases (especially in patients with a history of melanoma)

Siehe auch:

• Gallenblasenkarzinom
• Peutz-Jeghers-Syndrom
• Gallenblasenadenom
• benign vs malignant features of gallbladder polyps
• benign tumours and tumour like lesions of the gallbladder
• Cholezystolithiasis
• dysplasia of gallbladder wall
• Neoplasien der Gallenblase
• differentiating gallbladder polyps
• biliary sludge
• Adenom der Gallenblase

und weiter:

• Gallenblase
• tubuläres Adenom der Gallenblase Pylorusdrüsentyp