The value of (18)F-FDG PET/CT in Diagnosis and Evaluation of Response to Treatment in Retroperitoneal Fibrosis.

A 34-year-old male patient with abdominal pain and weight loss, without any known chronic disease, was referred to our clinic for Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) scan for malignant etiology due to the detection of a mass lesion in abdominal computed tomography (CT). Sedimentation: 34mm/hour, CRP: 8.3mg/dl, PPD test and sputum ARB test were negative. Abdominal CT showed a mass lesion with soft tissue density extending from the infrarenal level of bilateral iliac artery bifurcation, surrounding the aorta, inferior vena cava, bilateral common iliac veins and ureters, and bilateral Grade 1 hydronephrosis was observed. (18)F-FDG PET/ CT imaging showed intense hypermetabolism with the heterogeneous character in the mass lesion with soft tissue density, which was measured approximately 83 × 61 × 39mm in size on CT sections of the abdomen (SUVmax: 8.7). The appearance was considered in favor of malignancy and histopathological examination was recommended. However, the histopathological examination could not be performed because the patient’s consent could not be obtained. Idiopathic retroperitoneal fibrosis (RF) were considered considering the clinical, laboratory, and imaging findings of the case. Methylprednisolone was started at 64mg/day, the dose was decreased according to the clinical response and discontinued during the sixth month. In the fourth month, 50mg of Azathioprine was added, and patient follow-up continued. After six months of treatment, the patient’s clinical and laboratory findings improved. (18)F-FDG PET/CT examination was performed in terms of control and response to treatment. (18)F-FDG PET/CT showed that the hypermetabolic mass lesion in the retroperitoneal area of the abdomen was metabolically and morphologically completely regressed (▶ Fig. 1). Idiopathic RF is a rare disease also known as Ormond’s disease [1, 2]. RF causes inflammation and fibrosis by surround▶ Fig. 1 Before therapy (18)F-FDG PET/CT axial fusion a, c, e, coronal g sagittal i images show a hypermetabolic mass lesion with soft tissue density extending from infrarenal level to bilateral iliac artery bifurcation, surrounding the aorta, inferior vena cava, bilateral common iliac veins, and ureters, after therapy axial fusion b, d, f, coronal h sagittal j images show the hypermetabolic mass lesion in the retroperitoneal area of the abdomen metabolically and morphologically completely regress. Case Report