Tumefactive gallbladder sludge: the MRI findings

Highlights

• Tumefactive gallbladder sludge is hyperintensity on T1-weighted images.

• Most of the lesions showed neither enhancement nor diffusion restriction.

• On follow-up, tumefactive gallbladder sludge were found to have either disappeared or decreased.

Aim

To evaluate the conventional and diffusion-weighted magnetic resonance imaging (MRI) images of tumefactive gallbladder sludge.

Materials and methods

The institutional review board approved this retrospective study. Between January 2006 and January 2015, 3478 patients were diagnosed with gallbladder sludge by ultrasonography (US). Of them, 12 patients (eight male, four female; mean age, 63.6 years) with 12 tumefactive gallbladder sludge lesions, who underwent subsequent MRI for further evaluation within 1 month, were included in this study. Data regarding the clinical features, presence of enhancement, and signal intensities of the T2-, T1-, and diffusion-weighted images were collected.

Results

All cases of tumefactive sludge were detected incidentally. None of the patients had any predisposing factors for biliary sludge. The tumefactive gallbladder sludge was predominantly seen as a well-defined mass-like lesion. It showed hyperintensity on T1-weighted images (91.7%, 11/12), and variable signal intensities on T2-weighted images. Most of the tumefactive sludge lesions showed no enhancement on the dynamic phases (90%, 9/10). There were no cases with diffusion restriction. Among the patients with follow-up US data (n=7), all the lesions were found to have either disappeared or decreased in size.

Conclusion

Although tumefactive gallbladder sludge on US can mimic gallbladder cancer, its hyperintensity on a T1-weighted image, and the absence of enhancement and diffusion restriction on MRI images can be helpful for differentiating it from a tumorous condition.

Introduction

Ultrasonography (US) is currently the preferred diagnostic technique in gallbladder pathology including polyps, sludge, and cholelithiasis.¹ Biliary sludge is composed of a suspension of cholesterol monohydrate crystals or calcium bilirubinate granules, and/or other calcium salts embedded in mucus, a mixture of mucin and proteins.² It is rarely seen in asymptomatic healthy adult populations. Its prevalence was reported as ranging from 0% to 0.20% in men, and 0.18% to 0.27% in women.3, 4 The incidence of biliary sludge may be increased in specific clinical conditions such as pregnancy,⁵ total parenteral nutrition,⁶ rapid weight loss,⁷ prolonged fasting in intensive care unit,⁸ and octreotide treatment.⁹

At US, it typically appears as a low-level echo with a fluid–fluid level, without posterior acoustic shadowing, that characteristically moves slowly with changes in patient position.¹⁰ In contrast, the tumefactive appearance of biliary sludge does not form a fluid–fluid level, but appears as a polypoid mass in gallbladder, without movement during position change.¹¹ Thus, tumefactive sludge, as the name suggests, can mimic a tumour in clinical practice, requiring short-term follow-up or further evaluation with additional imaging techniques including contrast-enhanced US (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI).1, 12

A previous study investigating the clinical follow-up for sludge using US reported that it can persist in approximately 20% of cases over a 3-year period.¹³ Given this, follow up studies with conventional US, CEUS, CT, or MRI studies could be applied as adjunct techniques for a definite diagnosis of tumefactive sludge. Recently, technological advances in MRI including diffusion-weighted imaging (DWI), and the use of hepatobiliary contrast agents, enable MRI to be used as a conclusive diagnostic tool for gallbladder diseases14, 15; however, there has been no study analysing the MRI findings of tumefactive sludge. Thus, the aim of the present study was to evaluate the MRI findings of tumefactive sludge using a large retrospective cohort.