Overview
Definition:
Parathyroidectomy is the surgical removal of one or more parathyroid glands, most commonly performed to treat hyperparathyroidism
It involves identifying and excising diseased parathyroid tissue while preserving the function of remaining healthy glands
The procedure is crucial for normalizing calcium and phosphate metabolism and alleviating symptoms associated with parathyroid disorders.
Epidemiology:
Primary hyperparathyroidism (PHPT) is the most common indication, affecting approximately 1-4% of the general population, with higher prevalence in women and increasing incidence with age
Sporadic adenomas account for about 80-85% of PHPT cases, while hyperplasia accounts for 10-15%, and carcinoma is rare (<1%)
Secondary hyperparathyroidism (SHPT) is prevalent in patients with chronic kidney disease (CKD).
Clinical Significance:
Uncontrolled hyperparathyroidism leads to significant morbidity, including nephrolithiasis, osteoporosis, cognitive dysfunction, cardiovascular complications, and pancreatitis
Parathyroidectomy is the definitive treatment for symptomatic PHPT and selected asymptomatic cases, offering a cure and preventing long-term sequelae
It is a cornerstone of endocrine surgery and requires meticulous surgical skill for optimal outcomes.
Indications
Indications For Surgery:
Symptomatic primary hyperparathyroidism regardless of serum calcium levels
Asymptomatic PHPT with serum calcium >1 mg/dL above the upper limit of normal, reduced bone mineral density (T-score < -2.5), or urinary calcium excretion >400 mg/day
Age <50 years
Significant comorbidities that might worsen with hyperparathyroidism
Parathyroid carcinoma
Severe secondary hyperparathyroidism refractory to medical management and impacting quality of life or causing significant morbidities like extraskeletal calcification.
Imaging Guidance:
Preoperative imaging (ultrasound, sestamibi scan, CT scan) is vital to localize the diseased gland(s), particularly for minimally invasive approaches
However, surgical exploration remains the gold standard, and imaging is complementary, not a replacement for careful surgical dissection.
Patient Selection:
Careful patient selection based on clinical presentation, biochemical profile, bone density, and imaging is paramount
Multidisciplinary assessment, including nephrologists and endocrinologists, may be required for complex cases, especially those with CKD.
Diagnostic Approach
Biochemical Evaluation:
Elevated serum calcium levels (often >10.5 mg/dL or 2.6 mmol/L), typically with elevated or inappropriately normal parathyroid hormone (PTH) levels
Measurement of serum phosphate (often low), alkaline phosphatase (may be elevated), 25-hydroxyvitamin D, and urine calcium excretion (24-hour urine collection) is essential
Renal function tests and bone mineral density (DEXA scan) are also important.
Imaging Studies:
High-resolution ultrasound is highly sensitive for detecting adenomas, especially in the anterior neck
99mTc-sestamibi scintigraphy is useful for identifying hyperfunctioning parathyroid tissue, particularly for ectopic glands or multiglandular disease
Multidetector CT (MDCT) with contrast can further delineate the anatomy and location of abnormal glands.
Differential Diagnosis:
Familial hypocalciuric hypercalcemia (FHH) is a key differential to rule out, characterized by low urinary calcium excretion and normal PTH
Other causes of hypercalcemia include malignancy-associated hypercalcemia (PTHrP production), granulomatous diseases, certain medications (thiazides, lithium), and vitamin D intoxication.
Surgical Management
Preoperative Preparation:
Confirmation of diagnosis through biochemical tests
Preoperative imaging to localize the offending gland
Briefing the patient about the procedure, risks, and benefits
Ensuring adequate hydration
Avoiding medications that might interfere with calcium metabolism if possible.
Anesthesia:
General anesthesia is typically used
Local anesthesia with sedation may be an option for select minimally invasive procedures
Intraoperative neuromonitoring of the recurrent laryngeal nerve is crucial
Intraoperative PTH monitoring (quick PTH assay) is highly valuable for confirming complete removal of hyperfunctioning tissue and enabling unilateral or focused exploration.
Surgical Approaches:
Traditional bilateral cervical exploration involves a transverse incision in the lower neck, with careful identification and dissection of all four parathyroid glands
Minimally invasive parathyroidectomy (MIP) utilizes smaller incisions and may be guided by imaging and intraoperative PTH monitoring, often targeting a single adenoma.
Technique Details:
Meticulous dissection is required to identify the parathyroid glands, which are typically located posterior to the thyroid lobes
Identification of the recurrent laryngeal nerve and its preservation is paramount
The surgeon must differentiate parathyroid tissue from lymph nodes and thyroid nodules
If hyperplasia is present, subtotal (3.5 gland) or total parathyroidectomy with autotransplantation may be performed.
Postoperative Care
Monitoring:
Close monitoring of serum calcium and PTH levels is essential postoperatively
A significant drop in calcium and PTH within hours of surgery indicates successful removal of hyperfunctioning tissue
Monitoring for signs and symptoms of hypocalcemia (tetany, paresthesias, muscle cramps, Chvostek’s and Trousseau’s signs).
Medical Management:
Intravenous calcium supplementation may be required in cases of significant hypocalcemia
Oral calcium and calcitriol (active vitamin D) are often initiated to maintain normocalcemia and prevent hungry bone syndrome, especially after extensive resections or in the setting of severe preoperative hyperparathyroidism
Doses are adjusted based on serum calcium levels.
Complications Management:
Management of early complications such as recurrent laryngeal nerve injury (dysphonia, aspiration) and hypoparathyroidism
Late complications like hungry bone syndrome and potential graft failure (if autotransplantation was performed) require ongoing monitoring and adjustment of medical therapy.
Complications
Early Complications:
Hypocalcemia (most common, ranging from asymptomatic to symptomatic tetany, often due to hungry bone syndrome)
Recurrent laryngeal nerve injury leading to vocal cord paralysis (temporary or permanent dysphonia)
Hematoma formation and wound infection
Persistent or recurrent hyperparathyroidism due to missed glands or inadequate resection.
Late Complications:
Hungry bone syndrome (severe hypocalcemia after removal of long-standing hyperparathyroidism)
Scarring and cosmetic concerns
Autotransplant failure (if performed) leading to permanent hypoparathyroidism
Recurrence of hyperparathyroidism years later.
Prevention Strategies:
Careful surgical technique, especially nerve identification and preservation
Intraoperative PTH monitoring to confirm complete removal of hyperfunctioning tissue
Thorough anatomical dissection to identify all glands
Judicious use of subtotal or total parathyroidectomy with autotransplantation in cases of hyperplasia
Prophylactic calcium and calcitriol administration postoperatively
Experienced surgical team.
Prognosis
Factors Affecting Prognosis:
The success rate of parathyroidectomy is high, typically >95% for experienced surgeons
Factors influencing prognosis include the underlying cause (adenoma vs
hyperplasia vs
carcinoma), surgeon's experience, completeness of resection, and management of postoperative hypocalcemia
Prompt diagnosis and treatment lead to significant improvement in symptoms and reduction of long-term morbidities.
Outcomes:
Successful parathyroidectomy leads to normalization of serum calcium and PTH levels, resolution of symptoms related to hypercalcemia, and improvement in bone mineral density
Nephrolithiasis and renal function may also improve
Parathyroid carcinoma has a poorer prognosis with a higher risk of recurrence and metastasis.
Follow Up:
Postoperative follow-up typically includes biochemical assessments (calcium, PTH) at intervals of 1 week, 1 month, 3 months, 6 months, and then annually
Bone mineral density scans should be repeated to monitor recovery
Patients should be educated on lifelong monitoring for recurrence or persistent hypoparathyroidism.
Key Points
Exam Focus:
Differentiate between primary, secondary, and tertiary hyperparathyroidism
Understand indications for surgery in PHPT
Recall the biochemical profile of hyperparathyroidism
Recognize the importance of intraoperative PTH monitoring and recurrent laryngeal nerve preservation
Be aware of the management of hypocalcemia and hungry bone syndrome postoperatively.
Clinical Pearls:
Always consider the differential diagnosis of hypercalcemia
Preoperative imaging is a guide, not a dogma
surgical exploration is key
Intraoperative PTH drop of >50% from baseline or to below normal levels within 10-15 minutes confirms successful resection
Postoperative hypocalcemia is common and manageable
aggressive treatment of hungry bone syndrome is crucial.
Common Mistakes:
Failure to consider FHH in cases of mild hypercalcemia and hypocalciuria
Inadequate preoperative workup leading to missed diagnoses or inadequate surgical planning
Inadvertent injury to the recurrent laryngeal nerve
Incomplete resection of hyperfunctioning parathyroid tissue leading to persistent hyperparathyroidism
Underestimating the severity of hungry bone syndrome and inadequately treating postoperative hypocalcemia.