We illustrate both common and unusual inflammatory gallbladder conditions, including adenomyomatosis, emphysematous cholecystitis, xanthogranulomatous cholecystitis, gangrenous cholecystitis, perforation and inflammatory masses mimicking gallbladder malignancy. We also demonstrate true gallbladder neoplasms including adenocarcinoma, lymphoma and melanoma. Emphasis is placed on the imaging features that help differentiate inflammatory from malignant gallbladder disease.

MALIGNANCY

·   Adenocarcinoma is the commonest histological type

·   Clinical presentation

    o   Non-specific, can be seen in cholecystitis and other benign / malignant conditions

            §    Abdominal pain

            §    Weight loss

            §    Fever

            §    Jaundice, with other features of biliary obstruction

     o   Atypically can present with fistulation Fig. 1

·   Often advanced stage if symptoms present

     o   Due to vascular invasion, direct tumour spread into liver / peritoneum, lymphadenopathy Fig. 2 Fig. 3

     o   Poor prognosis

·   Risk factors

     o   Cholelithiasis

     o   Chronic biliary infections

     o   Primary sclerosing cholangitis (PSC)

     o   Porcelain gallbladder

·   Imaging

     o   Ultrasound / CT often first modalities for non-specific symptoms Fig. 4

             §   High sensitivity for detection of advanced tumours

             §   Limited in diagnosis of early lesions

            §   CT poor sensitivity/specificity for assessment of gallbladder luminal content

·   Can be falsely reassuring

·   Good for tumour staging

    o   MRI used for further characterisation Fig. 5

             §   If gallbladder appearances equivocal

             §   For pre-operative planning (check local resectability) Fig. 6

ADENOCARCINOMA

Background:

·   5th most common GI malignancy

·   Most common biliary tract malignancy

·   Macroscopically, 3 basic radiological patterns:

    o   Soft-tissue mass within gallbladder, occupying / replacing lumen

    o   Diffuse / focal thickening of gallbladder wall

    o   Polypoid mass within gallbladder lumen

US:

·   Heterogeneous, predominantly hypoechoic intraluminal tumour

·   Anechoic foci of trapped bile or necrotic tumour may be present

·   Shadowing foci from gallstones, porcelain gallbladder or tumour calcifications

·   Polyps

    o   >1cm increased risk of malignancy

    o   Thickened implantation base

CT:

·   Hypointense on unenhanced CT

·   Enhancement with IV contrast

  o   Early arterial phase may reveal intense, irregular peripheral enhancement

         §   Compared to smooth, slow enhancement in chronic cholecystitis

   o   Contrast may be retained in fibrous stroma during PV and delayed phases

·   Irregular, asymmetric, extensive wall thickening Fig. 7

   o   Benign processes more likely to cause diffuse, symmetrical wall-thickening

MRI:

·   Focal/asymmetric mural thickening of >1cm highly suggestive of malignancy

·   T1WI- hypo-isointense relative to liver

·   T2WI- mildly hyperintense relative to liver

·   Enhancement after IV contrast similar to CT

·   May not be able to identify gallbladder separately

    o   Gallstones maybe present within the mass

·   Extension into adjacent liver

    o   Similar signal characteristics as gallbladder tumour

PET-CT:

·   Typically intense accumulation of FDG

·   Not specific to malignancy

    o   Also seen in benign inflammatory gallbladder conditions

METASTATIC MELANOMA

Background:

·   Most common cancer to metastasise to gallbladder (50% of metastases)

·   Indicative of widespread metastatic disease

·   Poor prognosis

·   Treatment - surgical excision if solitary site

·   History crucial to diagnosis

US:

·   Single, or multiple hyperechoic masses, >1cm in diameter, attached to gallbladder wall

    o   No shadowing Fig. 8

    o   Not mobile

·   Focal thickening

CT and MRI:

·   Hyper-enhancing mass or focal wall thickening Fig. 9

·   T1WI- high signal (due to melanin)

·   T2WI- low signal

·   Can have a heterogeneous appearance, if low melanin content / internal haemorrhagic foci / necrosis Fig. 10

PET-CT:

·   Avid uptake of FDG Fig. 9

    o   Not specific for melanoma metastases

LYMPHOMA

Background:

·   Very rare (case reports)

·   Classified as either primary, non-Hodgkins lymphoma from MALT, or secondary to systemic lymphoma

US, CT and MRI :

·   Homogenous bland soft-tissue mass

·   Associated lymphadenopathy

·   Can be difficult to differentiate from primary adenocarcinoma

    o   Hypointense on T1WI, and hyperintense on T2WI images relative to liver

    o   Little enhancement following contrast

    o   Little or no mass effect maybe only distinguishing feature

PET-CT:

·   Avid uptake of tracer

INFLAMMATORY

·   Common cause of pain

·   Clinical presentation

    o   Right upper quadrant pain

    o   +/- fever

    o   +/- jaundice

    o   Mass

    o   Most inflammatory conditions associated with gallstones

·   Imaging

    o   Ultrasound often first modality

    o   MR/CT good problem-solving tools

CHRONIC CHOLECYSTITIS

Background:

·   Almost always associated with gallstones

·   Non-specific clinical presentation

    o   Nausea

    o   Non-specific abdominal pain

    o   Abdominal distension

US, CT and MRI:

·   Gallbladder may be contracted, and not demonstrated

·   Symmetrical diffuse wall-thickening

    o   Low T2 signal on MRI (due to fibrosis from repeated episodes of inflammation)

·   Minimal wall enhancement, compared to acute cholecystitis, following contrast Fig. 11

·   Enhancement is smooth, slow and prolonged Fig. 12 Fig. 13 Fig. 14

EMPHYSEMATOUS CHOLECYSTITIS

Background:

·   Variant of acute cholecystitis- similar presentations

·   Secondary infection of gallbladder wall by gas-forming organisms

    o   Clostridium perfringens, Escherichia coli, Bacilis fragili

·   Presence of intramural or intraluminal gas in absence of abnormal fistulation

·   Common in patients with diabetes and the elderly

·   Increased risk of gangrene, perforation, pericholecystic abscess, peritonitis

US:

·   Appearances of gas may mimic porcelain gallbladder / stones in contracted gallbladder

·   Curvilinear or punctate hyperechoic foci, with ring-down artefact

CT:

·   Most sensitive and specific modality

·   Low attenuation foci, consistent with intraluminal and intramural gas Fig. 15

·   Other non-specific signs:

  o   Pneumobilia, irregularity or discontinuity of gallbladder wall, pericholecystic fluid, abscess formation, free intraperitoneal gas

MRI:

·   Areas of signal void (gas) within gallbladder wall / lumen

GANGRENOUS / NECROTISING CHOLECYSTITIS

Background:

·   Severe complication of acute cholecystitis Fig. 16

·   Increased patient morbidity and mortality

US:

·   Specific sign - alternating hyper and hypo echoic linear areas within gallbladder wall

CT:

·   Highly specific

·   Lack of enhancement of gallbladder wall Fig. 17  Fig. 18

·   Intramural or intraluminal gas

·   Intraluminal membranes - consistent with sloughed mucosal lining

·   Pericholecystic abscess formation

·   Further, non-specific signs: transient adjacent hepatic parenchymal enhancement, pericholecystic fluid, striation of gallbladder wall

MRI:

·   T1 - high signal within and adjacent to the gallbladder wall (haemorrhage/necrosis)

·   T2 - high signal within and adjacent to the gallbladder wall (oedema)

GALLBLADDER PERFORATION

Background:

·   Complication of gangrenous gallbladder

·   Caused by transmural necrosis in acute cholecystitis

·   Pathology:

   o   Obstructive mass of cystic duct (gallstone usually), causing proximal gallbladder distension, vascular compromise, ischaemia, necrosis and perforation

US, CT and MRI :

·   Frank disruption of gallbladder wall

·   May see an extraluminal gallstone- secondary to a wall-defect

·   Pericholecystic fluid +/- abscess formation Fig. 19

ADENOMYOMATOSIS

Background:

·   Common, incidental

·   Benign, usually asymptomatic

·   Focal thickening of gallbladder wall

    o   Mucosal hyperplasia

    o   Thickening of muscular layer

    o   Prominence of Rokitansky-Aschoff (RA) sinuses

        §   Excessive proliferation of surface epithelium with deep / branching invaginations

US:

·   Comet-tail artefact is pathognomonic Fig. 20

    o   Cholesterol crystals within RA sinuses

CT and MRI:

·   Mural thickening Fig. 7

·   Multiple intramural cystic components (bile-filled RA sinuses)

    o   String-of-pearls / rosary sign (best on T2W MRI) Fig. 21

·   Early mucosal and subsequent serosal enhancement 

PET-CT:

·   False positive uptake reported in acute infection

XANTHOGRANULOMATOUS CHOLECYSTITIS (XGC)

Background:

·   Uncommon inflammatory condition

·   Associated with gallstones

·   Caused by intramural extravasation of bile from RA sinuses / superficial mucosal ulcerations

·   Histologically focal or diffuse destructive inflammatory process with xanthoma-like foam cells, scarring and ceroid nodules

·   Clinical presentation

    o   Acute cholecystitis

    o   F> M

US:

·   Hypoechoic intramural nodules

CT:

·   Closely resembles gallbladder carcinoma Fig. 22

    o   Continuous linear enhancement of mucosa Fig. 23

    o   Diffuse or focal gallbladder wall thickening Fig. 24

    o   Hypoattenuating intramural nodules (xanthogranulomas)

MRI:

·   Intramural lesions with markedly elevated T2 signal

    o   Correspond to low-attenuation intramural nodules seen at CT

·   Preservation of linear mucosal enhancement

PET-CT:

·   False positive uptake has been reported

INFLAMMATORY PSEUDOTUMOUR

Background:

·   Part of a spectrum of mass-forming diseases that can occur in almost any organ

·   Fibro-inflammatory masses characterised by proliferation of histiocytes, eosinophils and plasma cells.

·   Conservative treatment

US, CT and MRI:

·   Wall thickening Fig. 25 Fig. 26 Fig. 27

·   Gallbladder mass

    o   Early enhancement on CT and MRI

    o   Usually causes little mass effect (unlike true malignant tumours)

·   Local inflammation and invasion of surrounding structures