Imaging-based algorithmic approach to gallbladder wall thickening

Table 1 Features of ultrasonography which help in differentiation of benign and malignant gallbladder wall thickening

USG features	Benign wall thickening	Malignant wall thickening
Type of thickening	Diffuse and symmetric	Diffuse/focal and asymmetric
Mucosa	Intact	Discontinuous
Layered pattern of GB wall	Preserved	Lost
Color doppler findings	Low mean flow velocity and peak systolic velocity	High mean flow velocity and peak systolic velocity
Shear wave elastography parameters	Low shear wave velocity	High shear wave velocity

USG: Ultrasonography; GB: Gallbladder.

Table 2 Features of contrast-enhanced ultrasonography which help in differentiation of benign and malignant gallbladder wall thickening

	Benign wall thickening	Malignant wall thickening
Type of enhancement	Homogenous arterial phase enhancement	Non-homogenous arterial phase enhancement
Pattern of vascularization	Branched or tortuous intralesional vascularity	Dotted intralesional vascularity
Dynamic change of enhancement	Washout time > 40 s	Washout time < 40 s
Infiltration into liver parenchyma	Absent	Present

Table 3 Features of computed tomography which help in differentiation of benign and malignant gallbladder wall thickening

CT findings	Benign wall thickening	Malignant wall thickening
Patterns of enhancement	Single layer: Homogenous enhancement; two layered patterns: Inner layer isoattenuating to liver	Single layer: Strongly heterogeneously enhancing; two layered patterns: Inner layer enhancing in arterial phase and isoattenuating in venous phase
Biliary obstruction	Not seen	More likely to be seen
Regional lymphadenopathy	Not present	Present
Infiltration into liver	Not seen	May be present

CT: Computed tomography.

Table 4 Features of magnetic resonance imaging which help in differentiation of benign and malignant gallbladder wall thickening

MRI findings	Benign wall thickening	Malignant wall thickening
Pattern of thickening	On T2, thin hypointense inner layer and thick hyperintense outer layer or multiple T2 hyperintense foci in wall	Diffuse nodular thickening without layering
Dynamic contrast enhancement	Relatively slow enhancement	Early enhancement
Diffusion restriction	High ADC value and low lesion to spinal cord ratio	Low ADC value and high lesion to spinal cord ratio

MRI: Magnetic resonance imaging; ADC: Apparent diffusion coefficient.

Table 5 Rare causes of gallbladder wall thickening and their imaging findings

Cause	CT findings
Tuberculosis	(1) micronodular type: Micronodular or polypoidal lesions in GB wall; (2) thickened wall type: Most common. Diffuse or focal, nonspecific, homogeneous, or heterogeneous enhancement. Halo of edema may be present; and (3) mass-forming type: Large mass with multicentric necrosis and foci of calcification
Primary lymphoma	(1) high grade: Solid and bulky mass in the GB fossa or marked GB wall thickening; (2) low grade: Mild GB wall thickening with intact mucosa
Neuroendocrine tumor	Most common as mass replacing GB with well-defined margins and intact mucosa as compared to GBC. Arterial hyperenhancement. More extensive and bulky lymph node and hepatic metastasis compared to GBC

CT: Computed tomography; GB: Gallbladder; GBC: Gallbladder carcinoma.