Renal osteodystrophy presenting as a metabolic superscan on F-18 FDG PET/CT

Abstract

Rationale:F-18 Fluoro Deoxyglucose positron emission tomography and computed tomography (F-18 FDG PET/CT) is a useful modality in the evaluation of patients with malignancies. Increased incidence of lympho-proliferative disorders has been reported in individuals with long-standing end-stage renal disorders treated with renal replacement therapy.Patient concerns:A 30-year-old male on peritoneal dialysis on account of end-stage renal disease. He had acute rejection of an earlier transplanted renal allograft. He was referred for an F-18 FDG PET/CT based on a clinical suspicion of lymphoma on account of bilateral inguinal lymphadenopathy associated with bilateral pedal swelling.Diagnosis:Renal osteodystrophy was diagnosed based on diffusely intense F-18 FDG uptake in the axial skeleton, focal uptake in the costochondrial junctions and linear cortical uptake in the appendicular skeleton. No findings suggestive of lymphoma was seen.Interventions:A diagnosis of renal osteodystrophy with no evidence of a lymphoma prevented futile biopsy of inguinal lymphadenopathy. Patient continued with peritoneal dialysis with no further interventionOutcomes:Regular follow-up of patient to monitor calcium, phosphate and parathyroid hormone levels. Treatment will be indicated when laboratory results as well as clinical signs and symptoms are suggestive.Lesson:Metabolic bone disorder such as is seen in renal osteodystrophy should be considered in the differential diagnoses in patients with diffusely increased bone uptake on F-18 FDG PET/CT scan.

Case report: 18F-FDG PET/CT skeletal superscan-like in an adult patient with acute lymphoblastic leukemia

“…This feature “looks too good” due to the diffuse and symmetric skeletal uptake, similar to the appearance of a bone scan. To date, diffuse tracer uptake in the skeleton/bone marrow as a skeletal superscan pattern on 18 F-FDG PET/CT has been previously reported in hematological diseases (including two cases of multiple myeloma ( 12 , 13 ), two cases of lymphoma and two cases of acute lymphoblastic leukemia ( 6 , 14 – 16 ), and one case of hemophagocytic lymphohistiocytosis) ( 17 ), nine cases of solid tumors with extensive bone metastasis ( 11 , 18 – 25 ), and metabolic diseases with three cases of hyperparathyroidism and one case of renal osteodystrophy ( 26 – 29 ). By reviewing all the medical images of the reports, the hematological diseases revealed greater homogeneous radiotracer uptake in the skeleton, as in our case, and the metabolic diseases all had a specific skull and mandible intense uptake pattern.…”

Metabolic Superscan on 18F-FDG PET/CT in a Patient With Secondary Hyperparathyroidism

“…This causes continuous stimulation of parathyroid glands leading to secondary hyperparathyroidism. In renal osteodystrophy, there is an increase in bone turnover as a result of chronic hypocalcemia 12. It has been postulated that the diffuse osseous FDG hypermetabolism in axial and appendicular skeleton in metabolic superscan is due to the increment in osteoblastic activity and bone turnover induced by hypersecretion of parathormone,11,13,17 leading to an increase of chemisorption onto the calcium hydroxyapatite crystal.…”

“…6 Superscan has also been reported in nonskeletal metastasis such as liver 7,8 and peritoneum. 9 Causes of metabolic superscan in FDG PET/CT include primary hyperparathyroidism, 10 secondary hyperparathyroidism caused by chronic renal failure, 11,12 parathyroid carcinoma, 13,14 and also acute lymphoblastic leukemia. 15,16 The inadequacy of vitamin D activation and phosphorus excretion into the urine by the kidneys in end-stage renal failure results in hyperphosphatemia and hypocalcemia.…”

“…In renal osteodystrophy, there is an increase in bone turnover as a result of chronic hypocalcemia. 12 It has been postulated that the diffuse osseous FDG hypermetabolism in axial and appendicular skeleton in metabolic superscan is due to the increment in osteoblastic activity and bone turnover induced by hypersecretion of parathormone, 11,13,17 leading to an increase of chemisorption onto the calcium hydroxyapatite crystal. Superscan in FDG PET/CT is not always metastatic in origin, and careful assessment is essential in differentiating pathologic from benign superscan to avoid a diagnostic pitfall.…”