 Persistent PHPT is defined as failure to achieve normocalcemia within 6 months of initial parathyroidectomy, whereas recurrent PHPT is defined as hypercalcemia occurring after a normocalcemic interval of 6 months or more after parathyroidectomy [2,10]. Parathyroid reoperations are surgically challenging, with lower cure rates than first- Reprint requests to: publications@acr.org Parathyroid Adenoma time surgery and higher complication rates. As such, recent international guidelines state that preoperative imaging is essential in the reoperative setting to localize a target parathyroid lesion (or lesions) and to identify postoperative changes from previous parathyroid explorations that can impact a subsequent surgery [10]. Secondary hyperparathyroidism (SHPT) is a failure of calcium homeostasis whereby increased PTH production in response to hypocalcemia (and/or hyperphosphatemia) is unable to correct plasma calcium because of organ failure or reduced calcium availability. This is most commonly due to chronic kidney disease but can also be a result of malabsorption or vitamin D deficiency, among other causes [11]. Rarely, tertiary hyperparathyroidism (THPT) can occur in patients with longstanding SHPT and is characterized by a lack of PTH suppression despite rising serum calcium levels, manifesting as hypercalcemic hyperparathyroidism. This is most commonly encountered following kidney transplantation in patients with longstanding chronic kidney disease [11]. Surgical excision is recommended for medically refractory cases of SHPT and THPT. As these are typically disorders of MGD (ie, parathyroid hyperplasia), the goal of imaging is to identify all eutopic and potential ectopic or supernumerary glands in an attempt to guide the surgical approach [10,12-14]. Discussion of Procedures by Variant Variant 1: Adult or child. Primary hyperparathyroidism. Initial imaging.
Parathyroid Adenoma.  Persistent PHPT is defined as failure to achieve normocalcemia within 6 months of initial parathyroidectomy, whereas recurrent PHPT is defined as hypercalcemia occurring after a normocalcemic interval of 6 months or more after parathyroidectomy [2,10]. Parathyroid reoperations are surgically challenging, with lower cure rates than first- Reprint requests to: publications@acr.org Parathyroid Adenoma time surgery and higher complication rates. As such, recent international guidelines state that preoperative imaging is essential in the reoperative setting to localize a target parathyroid lesion (or lesions) and to identify postoperative changes from previous parathyroid explorations that can impact a subsequent surgery [10]. Secondary hyperparathyroidism (SHPT) is a failure of calcium homeostasis whereby increased PTH production in response to hypocalcemia (and/or hyperphosphatemia) is unable to correct plasma calcium because of organ failure or reduced calcium availability. This is most commonly due to chronic kidney disease but can also be a result of malabsorption or vitamin D deficiency, among other causes [11]. Rarely, tertiary hyperparathyroidism (THPT) can occur in patients with longstanding SHPT and is characterized by a lack of PTH suppression despite rising serum calcium levels, manifesting as hypercalcemic hyperparathyroidism. This is most commonly encountered following kidney transplantation in patients with longstanding chronic kidney disease [11]. Surgical excision is recommended for medically refractory cases of SHPT and THPT. As these are typically disorders of MGD (ie, parathyroid hyperplasia), the goal of imaging is to identify all eutopic and potential ectopic or supernumerary glands in an attempt to guide the surgical approach [10,12-14]. Discussion of Procedures by Variant Variant 1: Adult or child. Primary hyperparathyroidism. Initial imaging.