An Unexpected Case of Metal Biliary Stent Fracture Detected by Contrast Enhanced ¹⁸F-FDG PET/C

¹⁸F-FDG PET/CT is an useful diagnostic tool for cancer patients. In our routine practice, we perform a significant number of PET/CT scans in association with contrast enhanced CT, to assess resectability of abdominal tumors or to evaluate distant brain and liver metastases. We documented an unexpected emergency disease during a contrast enhanced ¹⁸F-FDG PET/CT. In a 63-year-old male patient, examined during follow-up of lung cancer, no sites of disease relapse were detected at PET/CT; nevertheless, diffuse tracer uptake was detected along the outline of a biliary stent. Correlative contrast enhanced CT diagnosed fracture of a metallic biliary stent without any evidence of cancer involvement. Patient was referred to the local department of surgery for substitution of the biliary stent. Although rare, unexpected emergency diseases requiring urgent management are detected using 18FFDG PET/CT. Correlative CT should be carefully evaluated in order to avoid delays in diagnosis, potentially leading to poorer prognosis.

PET/CT with ¹⁸F-FDG is widely used to investigate cancer patients. The ¹⁸F-FDG PET allows important metabolic information about tumor metabolism, growth or response to therapy while correlative CT imaging, with or without contrast agent, provides significant data on tumor location and respectability or about the presence or metastases in organs or tissues with high rate of physiological ¹⁸F-FDG uptake (i.e. liver and brain) [1], which are not easily recognizable by the only PET component of the scan [2]. In clinical practice, nuclear physicians and radiologists cannot exclude the possibility to encounter cases of unexpected emergency diseases when conducting PET/CT studies with contrast agent. Few studies in literature described this specific clinical setting, demonstrating that 0.35% of examined patients with ¹⁸F-FDG PET/CT may present clinical emergency disease, requiring a prompt and opportune treatment. Despite low, this percentage is significant when considering the poor prognosis linked to clinical conditions as pneumothorax, cerebral hemorrhage, acute cholecystitis and pancreatitis, already documented by means of ¹⁸F-FDG PET/CT in cancer patients [3]. Although rare, an unexpected emergency disease requiring urgent management can be observed using ¹⁸F-FDG-PET/CT in oncology patients; this condition needs to be correctly detected for accurate patient care and treatment.

A 63-year-old male patient underwent whole body contrast enhanced ¹⁸F-FDG PET/CT in our Department, during follow-up of lung cancer. Patient was previusly submitted (two years before) to upper right lobectomy for lung squamous carcinoma. Patient anamnesis was also positive for chronic pancreatitis. For this reason, he was submitted, 11 months before, to implantation of biliary stent due to the development of fibrosis of the bile duct. No sites of lung cancer relapse were detected at PET/CT. Nevertheless, PET/CT showed focal tracer uptake along the outline of the biliary stent (Figure 1) as evident in axial (a) and coronal (b) PET/CT details. Coronal Maximum Intensity Projection CT (c) and CT detail (d) after contrast administration underlined the fracture of the distal tract of the biliary stent, also evident as a covered self-expandable biliary metal stent in correlative Volume Rendering CT of the upper abdomen (e). Patient was referred to our local department of surgery, where he underwent biliary stent removal and reimplantation. After surgery, histological specimen diagnosed chronic inflammation; confirming the absence of neoplastic involvement. Biliary stents are used to manage benign and malignant obstruction by enabling biliary drainage and decompression, alleviate patient symptoms and improve quality of life [4]. Stent occlusion and stent migration are the most common complications of biliary stent insertion, whereas cholecystitis, cholangitis, pancreatitis, perforation and and bleeding are less common [5]. On the other hand, stent fracture is an extremely rare complication which has only been described in a few case reports [6,7]. PET/CT with ¹⁸F-FDG is widely used for staging or restaging cancer patients; it is known that a significant minority of oncology patients may present some emergency conditions which may mimick a malignant neoplasm at PET/CT or can be misdiagnosed to the relative specificity of ¹⁸F-FDG. In fact, being an analogue of glucose, ¹⁸F-FDG uptake may occur in several conditions other than malignant lesions, as phlogosis and infection. Correlative imaging with contrast enhanced CT can play a role of the utmost importance. Several studies have reviewed unexpected CT findings obtained in the emergency department [8,9]. For the best of our knowledge, no data are reported about the detection of the fracture of a biliary stent during a contrast enhanced ¹⁸F-FDG PET/CT performed in a cancer patient. The accurate knowledge of this emergency disease which can be observed in clinical practice of nuclear physicians and radiologists by ¹⁸F-FDG PET/CT can favour rapid diagnoses and could enable the need for urgent intervention for some patients. The CT component of the exam, with or without contrast agent, should be carefully evaluated immediately after the images acquisition, in order to avoid delays in diagnosis, potentially leading to poorer prognoses.

The authors do not have conflicts of interest relevant to this article to disclose.

Dr. Ferdinando Calabria examined PET/CT scan, conceptualized and designed, drafted the initial manuscript and reviewed and revised the manuscript. Dr. Mario Leporace examined contrast enhanced CT, collected data, carried out initial analyses and critically revised the manuscript. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

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