Solid organizing abscess of the liver

Clinical History

Recurrent cholangitis in a patient with long-standing stenosis of a roux-en-y choledochojejunostomy performed 30 years ago because of a chronic calcified mass- forming pancreatitis.
- Intrahepatic biliary stones.
- Portal cavernoma and prehepatic portal hypertension with esophageal varices,
bleeding previously.
- Diabetes mellitus.

Imaging Findings

MR imaging (Dec-2013): T2-wheighted MRI shows dilatation of intrahepatic biliary tree, pneumobilia and intrahepatic stones; MR-cholangiopancreatography evidences marked stenosis of the choledochojejunostomy, dilatation of intrahepatic biliary ducts and intrahepatic stones (Fig. 1a-c). Portal cavernoma and portal-systemic collaterals are visible on CE-3D-GE MRI (Fig. 1d).

MR imaging (Oct-2014): T1-wheighted GE MRI documents a hypointense mass-like lesion (2.5x5 cm) in segment IV of the liver; the lesion is isointense to the liver and circumscribed by an irregular hyperintense rim on T2-weighted MRI (Fig. 2a, b). The lesion does not exhibit water diffusion restriction but colliquative foci on multi-b DW-MRI (Fig. 3). No significant enhancement is evident on arterial phase of dynamic MRI with Gd-BOPTA; a wedge shape transient hepatic intensity attenuation is appreciable (Fig. 4a). The rim is hyperintense relative on late phase of CE-MRI; the mass does not take up the liver-specific contrast medium on hepatobiliary phase (Fig. 4b, c).

Discussion

Among focal infection of the liver, organizing solid abscesses are relatively infrequent and are thought to be an atypical slow-healing process in patients partially responsive to antibiotic therapy. They are characterized by a prominent chronic inflammatory reaction bounded by a fibrous rim and centered on a suppurative core, only seldom recognizable on non-invasive imaging, without any identifiable bacteria at microscopy; patients often have a history of biliary stone disease and recurrent pyogenic cholangitis [1].
Solid organizing hepatic abscesses are ipoattenuating/hypointense relative to the normal liver on non-enhanced CT and T1-wheighted MRI respectively, whereas they exhibit a typical target appearance on T2-weighted MRI and dynamic imaging [1]. The fibrous rim appears hyperintense on T2-weighted MRI and does not show water diffusion restriction on DWI [1, 2]. Moreover, whereas the main inflammatory component enhances similarly to the liver on dynamic imaging, the rim does not enhance on early dynamic phase but strongly enhances only on late phases [1].
Other hepatic abscesses (usually due to pyogenic pathogens, Brucella or parasites) can show a large solid component on diagnostic imaging [3–7]. However these abscesses are not circumscribed by a rim and are “predominantly” solid with a uniloculated or multiloculated liquefaction component [5].
Patients with chronic granulomatous disease, an inherited childhood immunodeficiency disease characterized by primary phagocyte defect, can suffer from hepatic abscesses presenting a solid or target-like lesion in early stages [3]. These abscesses, usually recurrent and often multiple, present a rim strongly enhancing on post contrast imaging [3].
Differential diagnosis of organizing solid hepatic abscesses should also include solid masses. Hepatic inflammatory pseudotumours can show a large spectrum of CT and MRI findings. They sometimes appear multilayered [8, 9], but they are usually hypointense and hyperintense on T1-weighted and T2-weighted MRI respectively and enhance only on delayed scans of CE-MRI [1, 8]. Hypovascular tumour, both primary and metastatic, enhance less than normal hepatic parenchyma and on late phase of dynamic imaging only. DW-MRI can easily discriminate hepatic abscesses from non-infected fluid collections of the liver [10]; moreover DW-MRI is very helpful in distinguishing a malignant mimicker from an abscess, which rim shows ADC values higher than tumour pseudocapsule [2, 11]. In conclusion, typical MRI findings can yield diagnosis of a solid organizing hepatic abscess in the appropriate clinical setting; percutaneous biopsy should be indicated for a definitive diagnosis in equivocal cases only.

Differential Diagnosis List

Final Diagnosis

Organizing hepatic abscess

URL:	https://www.eurorad.org/case/12245
DOI:	10.1594/EURORAD/CASE.12245
ISSN:	1563-4086