Diagnostic accuracy of MRI for gallbladder polyps;
a prospective diagnostic pilot study

Gallbladder (GB) polyps exist of two main pathological entities: true polyps
(neoplastic) and pseudo polyps (nonneoplastic). Surgery is only needed for true
polyps (potentially dysplastic or malignant). Based on current diagnostic
procedures (mainly by transabdominal ultrasound) the differentiation between
true and pseudo polyps is a dilemma due to inconsistent results. The decision
for cholecystectomy is mainly based on size and growth of the polyp and
concomitant suspicion of dysplastic or malignant degeneration.However
postoperative many polyps with a diameter > 1cm prove to be pseudo polyps and
some polyps < 1 cm have shown to be true polyps. Better differentiation between
true and pseudo polyps and differential diagnosis by diagnostic modalities like
MRI could prevent unnecessary surgeries and improve expediency and
cost-effectiveness of cholecystectomy for GB polyps.

Primairy objective: To determine the diagnostic accuracy of MRI for the
(differential) diagnosis of GB polyps and the differentiation between true and
pseudo polyps in patients with suspected GB polyp(s) on previous imaging
modality (TAUS) by using histopathological analysis of the gallbladder as
reference standard.
Secundairy Objective: - To compare the diagnostic properties of MRI to those of
TAUS and evaluate the position of MRI as second stage diagnostic tool in the
diagnostic algorithm of patients suspected of GB polyps.
- In parallel to create a cohort of patients
with GB polyps to establish symptoms and characteristics of these patients and
possible risk factors for GB polyps.

single centre prospective diagnostic pilot study. Patients from other hospitals
may be referred to the Radboudumc for participation in this study. All
information about the study will be given by the investigator of the Radboudumc
and all study procedures will be performed at the Radboudumc.

Participating patients will be asked to come to the Radboudumc to undergo
transabdominale ultrasound and MRI-scan. Both procedures will be performed and
evaluated according standarised protocols by specialised radiologists.
Radiologists are blinded for the result of the other imaging modality.
Patients will additionaly be treated at the reffering center (mainly by
cholecystectomy). Postoperative the results of the histopathological analysis
will be requested to compare to the preoperative diagnosis of the
transabdominal ultrasound and MRI-scan.

Included patients are already considered for cholecystectomy and will undergo
two additional diagnostic tests to increase scientific knowledge on the
diagnostics of GB polyps. Patients have to travel to the Radboudumc to undergo
the diagnostic test and lay supine, mainly during the MRI, for about 45
minutes. Additional unknown medical problems might be found on MRI and will be
reported to the treating physician. Transabdominal ultrasound and MRI have no
adverse reactions of their own. Gadolinium contrast agent used during MRI can
cause (mild) reactions in an extremely small percent of patients.
Butylscopolamine administered during MRI may cause side-effects in a small
proportion of patients.