Visualization of Gallbladder with In-111 Octreotide Scan

A 54-year-old woman underwent octreotide scintigraphy for evaluation of neuroendocrine tumor recurrence. The images demonstrated unusual uptake in gallbladder area in addition to physiologic uptake at other tissues. Whole-body planar and SPECT imaging were repeated after fatty meal ingestion at 28 hours in order to figure out whether this activity was physiologic or not. Since the unusual uptake in the gallbladder was still detected at these images, additional images were obtained 72 hours after radionuclide injection. The activity in the gallbladder disappeared at these images revealing the physiologic nature of this unusual accumulation.


Introduction
In-111 octreotide scan is widely used in the evaluation of neuroendocrine tumors and physiologic accumulation of the activity might lead to misinterpretation (1). Herein, we present a patient with neuroendocrine tumor who was imaged with In-111 octreotide and showed unusual uptake in the gallbladder.

Case Report
A 54-year-old woman was referred to our department of nuclear medicine for In-111 octreotide (Octreo Scan, Mallinckrodt Medical, Petten, the Netherlands) scanning. The patient had undergone an operation for neuroendocrine carcinoma 8 months ago and octreotide scintigraphy was planned with the purpose of detection of any possible recurrences.
Octreotide scintigraphy was performed and wholebody planar and SPECT were acquired at 4 and 24 hours after administration of 5 mCi (185 MBq) In-111 octreotide. The images demonstrated physiologic uptake at the liver, spleen, kidneys and bladder along with an unusual uptake at the location of gallbladder. Whole-body planar and SPECT imaging were repeated after fatty meal ingestion at 28 hours in order to differentiate pathological activity and physiologic uptake in the gallbladder. The unusual uptake in the gallbladder was still detected at these images; therefore additional images were obtained 72 hours after radionuclide injection. The activity in the gallbladder disappeared at these images indicating the physiologic nature of this unusual accumulation ( Figure 1 and Figure 2).

Literature Review and Discussion
In-111 octreotide has been widely used for 20 years for scintigraphic localization of primary and metastatic neuroendocrine tumors that express somatostatin receptors. Normal physiologic distribution of In-111 octreotide includes faint visualization of thyroid, pituitary gland and marked increased uptake in the liver, spleen, kidneys and bladder. Although rarely encountered, falsepositive studies have been reported due to increased activity at nonmalignant pathologies such as Paget's disease, parathyroid adenoma, cholecystitis, thrombus, abscess, infection, pulmonary fibrosis, pleural plaques and uterine myomas (2,3,4,5,6,7,8,9). Only a few cases in the literature have reported increased In-111 octreotide activity in the gallbladder (10,11,12,13,14). The unusual accumulation of In-111 octreotide in benign pathologies may be explained partially by the presence of somatostatin receptors in activated leukocytes during chronic inflammatory processes (15,16). After injection, In-111 octreotide is rapidly cleared by the kidneys (85% of the injected dose is recovered in the urine by 24 hours) and approximately 2% of the injected dose undergoes hepatobiliary excretion. Functional impairment is another possible reason for gallbladder visualization due to a delay in radionuclide excretion. Turner et al. showed that gallbladder motility is impaired in patients receiving long-acting somatostatin analogue and there might be an association with octreotide treatment and gallstone development (17). In our case a gallbladder inflammation that could explain such an uptake was not identified. Krausz et al. encountered unusual uptake in the gallbladder in 3 patients who underwent In-111 octreotide scintigraphy, and this activity disappeared after a fatty meal. It is also advised to administer a laxative on the day before injection, especially when the abdomen is the area of interest (18). Kurtaran et al. proposed that this problem might be prevented by performing a dual tracer SPECT imaging using In-111 octreotide and hepatobiliary agent, 99m Tc-trimethyl-brom-imino-diacetic acid (TBIDA) with dual energy window sets (13). In our case the activity in the gallbladder persisted even after the patient had a fatty meal, but it disappeared in late images at 72 hours after injection.
We concluded that the images in In-111 octreotide scintigraphy should not be obtained in the fasting state and if significant uptake is seen in the gallbladder area, late images up to 72 hours should be acquired. Concept