Influence of Surgical Volume on Operative Failures for Hyperparathyroidism
Parathyroidectomy is the mainstay of treatment for hyperparathyroidism. Operative intervention in a previously unexplored neck can yield cure rates greater than 95% [1,2]. However, once a patient has undergone neck surgery, such as in the case of failed parathyroidectomy, reoperation leads to cure rates of only 80% [3,4]. Similarly, complication rates associated with parathyroidectomy have been found to be much greater during reoperations than during initial surgeries [3]. This significantly lower success rate for reoperation combined with the higher complication rate illustrates the need for a surgeon to achieve eucalcemia at the initial operation.
Hyperparathyroidism
Hyperparathyroidism is as an elevation in parathyroid hormone (PTH) levels (the normal level being 10–65 pg/mL) causing hypercalcemia (the normal level being 8.5–10.5 mg/dL). The symptoms of hyperparathyroidism are varied and at times vague, affecting multiple organ systems (Box 1) [5]. Surgical intervention is warranted for patients with distinct symptoms that can be attributed to the elevation in calcium levels, such as nephrolithiasis, bone disease, and cardiovascular abnormalities. Many other patients with hyperparathyroidism are asymptomatic and are found to have an elevated calcium level on routine blood testing. Although these patients seem asymptomatic, studies have shown that they have vague neurologic symptoms that improve with surgery [6,7]. Furthermore, after parathyroidectomy, the quality of life markedly improves in asymptomatic patients [8]. Similarly, data have shown that the bone mass increases significantly after parathyroidectomy [9]. In 2009, guidelines were established for the timing of surgery in asymptomatic patients (Box 2) [10].
Box 1 The symptoms of hyperparathyroidism are nonspecific and varied, affecting multiple organ systems
Data from Doherty GM. Parathyroid Glands. In: Mulholland MW, editor. Greenfield’s surgery: scientific principles and practice. 4th edition. Philadelphia (PA): Lippincott Williams & Wilkins; 2006. p. 1316.
Box 2 Guidelines for surgical intervention in patients found to be hyperparathyroid, who seem to have no clinical symptoms of the disease
Data from Bilezikian J, Khan A, Potts JJ. Hyperthyroidism TIWotMoAP. Guidelines for the management of asymptomatic primary hyperparathyroidism: summary statement from the third international workshop. J Clin Endocrinol Metab 2009;94(2):335–9.
Most commonly, hyperparathyroidism is caused by a primary disorder of the parathyroid glands. A single parathyroid adenoma accounts for around 80% of the cases of primary hyperparathyroidism, with double adenomas and multigland hyperplasia making up the remaining 20% [11,12]. Rarely, primary hyperparathyroidism is because of parathyroid carcinoma. In the United States, primary hyperparathyroidism is a fairly common disease with an annual incidence of approximately 100,000 individuals [13]. The incidence is increased in the elderly and in women, with 2 of 1000 women older than 60 years being affected yearly [13]. The mainstay of treatment for patients with primary hyperparathyroidism is parathyroidectomy.
Secondary hyperparathyroidism is the excess secretion of PTH that occurs in response to hypocalcemia, most often because of chronic renal failure. It has been estimated that as many as 90% of patients with renal failure who require hemodialysis suffer from secondary hyperparathyroidism [14]. Malabsorption and other disorders causing calcium and vitamin D deficiencies, such as rickets and osteomalacia, are the less-common causes of secondary hyperparathyroidism. Up to 2% of patients with secondary hyperparathyroidism require parathyroidectomy [15].
Tertiary hyperparathyroidism occurs in patients with secondary hyperparathyroidism due to chronic renal failure who undergo renal transplantation and continue to have persistent hyperparathyroidism. Tertiary hyperparathyroidism affects up to 30% of kidney transplant recipients, and 1% to 5% of such patients require surgical management [15–17].
Parathyroidectomy is the standard treatment for patients with primary hyperparathyroidism and for those with secondary and tertiary hyperparathyroidisms requiring surgical intervention. Therefore, regardless of the cause, the ability to perform a safe and successful operation is imperative for surgeons treating this population of patients.
Surgical failure
Surgical failure for hyperparathyroidism results in persistent disease, whereby hypercalcemia either continues after the initial surgery or recurs within 6 months of the operation. In contrast, recurrent hyperparathyroidism occurs when a patient becomes hypercalcemic after 6 months of normal postoperative calcium levels. Although there are instances in which reoperation is unavoidable, for many patients, their second operations are because of inadequate or inappropriate initial surgeries. Mitchell and colleagues [18] examined this fact in a study on patients undergoing reoperations for thyroid and parathyroid surgery. They established criteria for avoidable and unavoidable parathyroid reoperations (Box 3). According to them, avoidable reoperations occurred because of errors in judgment, illustrated by a surgeon performing a focal exploration or reexploration without appropriate preoperative localization, which then leads to persistent hyperparathyroidism. Technical errors are also responsible for avoidable reoperative parathyroidectomy, such as a missed gland in its normal anatomic location. In a review of 130 patients undergoing reoperative parathyroidectomy, Udelsman and Donovan [19] reported that 91 glands were found in their normal anatomic locations. The remaining glands were found in the retroesophageal space, mediastinal thymus, carotid sheath, submandibular space, or aortopulmonary window or were intrathyroidal. Regardless of the location of the abnormal gland, the investigators were able to achieve a 95% success rate, demonstrating that experienced surgeons with knowledge of the ectopic locations of parathyroid glands can perform successful parathyroidectomies and that had they operated on these patients initially, most reoperations could have been avoided.
Box 3 Classification of parathyroid reoperations as either avoidable or unavoidable. Avoidable operations were either because of technical errors during the case or because of errors in judgment occurring preoperatively or during the operation
Persistent hyperparathyroidism after exploration without localization or intraoperative drop in PTH levels
Data from Mitchell J, Milas M, Barbosa G, et al. Avoidable reoperations for thyroid and parathyroid surgery: effect of hospital volume. Surgery 2008;144(6):899–906 [discussion: 906–7].
In the early nineties, there began to be an increased interest in the correlation between hospital and/or surgeon volume and clinical outcomes. Several studies of patients undergoing coronary artery bypass surgery, colectomy, gastrectomy, and pancreatic resection demonstrated that high-volume centers and surgeons had better outcomes than those considered to be less experienced [20–22]. Similar studies have been performed by multiple investigators regarding hospital and/or clinician volume as it correlates to outcomes in endocrine surgery. One of the first studies by Sosa and colleagues [3]
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