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Parathyroidectomy

last modified on: Wed, 10/03/2018 - 11:19

see also: Thyroidectomy and Thyroid Lobectomy
 # GENERAL CONSIDERATIONS

  1. Primary hypercalemia accounts for approximately 80-90% of all hypercalcemic patients in the outpatient setting.
    1. It is most commonly secondary to hyperplasia of one of the parathyroid glands, while 25% of the time it can be attributable to hyperplasia of all 4 glands.
      1. 3% of cases will be secondary to parathyroid carcinoma
    2. One half of patients with hyperparathyroidism are asymptomatic.
  2. Parathyroid hormone:
    1. The function of Parathyroid hormone is to maintain an extracellular concentration of calcium through the following effects:
      1. Stimulates osteoclasts
      2. Increases distal tubular reabsorption of Ca2+
      3. Decreases Phosphate reabsorption
      4. Increases production of 1,25 (OH)2 Vit D
  3. Diagnosis:
    1. The diagnosis can be made with findings of serum calcium levels > 10.2 mg/dl, in the setting of an elevated PTH level (Normal serum values for PTH are 10 - 55 picograms per milliliter (pg/mL)
    2. Thiazide diuretics and lithium excess can cause elevated PTH and serum calcium levels, mimicking primary hyperparathyroidism. Therefore, it is important to consider these medications when taking a history and to carry out further investigation if necessary before proceeding with surgery.

Parathyroid hormone levels above 55 picograms per milliliter (pg/mL) are considered to be high. These higher levels may be caused by:

  • Disorders that increase phosphate or phosphorous levels in the blood, such as chronic kidney disease
  • Failure of the body to respond to parathyroid hormone (pseudohypoparathyroidism)
  • Lack of calcium, which may be due to not eating enough calcium, not absorbing calcium, or losing too much calcium in your urine
  • Pregnancy or breastfeeding (uncommon)
  • Primary hyperparathyroidism
  •  Parathyroid Adenomas
  • Vitamin D disorders, including not enough sunlight in older adults and problems absorbing, breaking down, and using vitamin D in the body
  • Urine calcium can be elevated, but may be normal in this setting due to the mechanism of reabsorption of Ca by PTH
    1. For this reason, a 24 hour urine calcium level is generally obtained, but can still be normal in 1/3 of patients.
    2. It is important to rule out Familial Hypocalciuric Hypercalcemia in these patients, and this may lead to misdiagnosis. This is usually indicated by elevated serum calcium levels in the setting of low urinary calcium levels (true hypercalcemia will usually have elevated levels of both).
  • There are currently over 25 separate disease states that may lead to hypercalcemia.  In every other cause of hypercalcemia however, the PTH will be low (with the exception of 10% of patients that develop hypercalcemia secondary to lithium usage).
  • Indications: 
    1. Surgical excision of abnormal parathyroid tissue is the only definitive cure for primary hyperparathyroidism.  For symptomatic patients, indications are straight forward.  For asymptomatic patients, management may not be as clear cut.  The NIH established guidlines as published in 1991.
      1. Markedly elevated serum calcium (1-1.6 mg/dL above normal, ie, > 12 mg/dL
      2. History of an acute episode of life threatening hypercalcemia
      3. Creatinine clearance reduced by 30% with age-matched normal subjects
      4. Markedly elevated 24 hour urine calcium (>400 mg/d)
      5. Nephrolithiasis
      6. Age < 50
      7. Osteitis fibrosa cystica
      8. Substantially reduced bone mass as determined by direct measurement (Bone mass > 2 SD below controls matched for age, gender, and ethnic group)
      9. Neuromuscular symptoms: documented proximal weakness, atrophy, hyper-reflexia, and agait distubance
  •  Hereditary Hyperparathyroidism:

                 Although cases of sporadic hyperparathyroidism are idiopathic and the etiology remains unknown, heredity plays an important role in familial     hyperparathyroid disorders. Identifying conditions caused by genetic conditions is extremely important since the treatment differs from that used in patients with primary or secondary hyperparathyroidism.

Although primary hyperparathyroidism occurs sporadically, the familial disorders can occur with relatively high penetrance (approaching 95% in Multiple endocrine Neoplasia, type 1 [MEN1]).

The following are definitions of hereditary hyperparathyroid disorders:

  • MEN1 - Multiple endocrine Neoplasia, type 1 (previously Wermer syndrome); tumors of parathyroid, pituitary, and pancreas
  • MEN2A -Multiple endocrine Neoplasia, type 2A (previously Sipple syndrome); medullary carcinoma of the thyroid, adrenal pheochromocytoma, and parathyroid tumors
  • HPT-JT - Hyperparathyroidism, jaw tumor syndrome
  • FIHPT - Familial isolated hyperparathyroidism
  • ADMH - Autosomal dominant mild hyperparathyroidism or familial hypercalcemia with hypercalcuria
  • FHH - Familial hypocalciuric hypercalcemia
  • NSHPT - Neonatal severe hyperparathyroidism
  • Imaging
    1. Several imaging studies are useful in the surgical workup for the parathyroidectomy.

      Imaging Studies

         
       
  • Consideration 2 (Contraindications)
    1. Surgery is contraindicated in patients with  Familial hypocalciuric hypercalcemia (FHH).
    2. Consideration 1 (Evaluation)
      1. Sub-Con
        1. Sub-sub-con
    3. Consideration 2 (Consent for Surgery)
      1. Sub Con
  • NURSING CONSIDERATIONS
    1. Room Setup
      1. See Basic Soft Tissue Room Setup
    2. Instrumentation and Equipment
      1. Standard
        1. Major Instrument Tray 1, Otolaryngology
        2. Major Instrument Tray 2, Otolaryngology
        3. Bipolar Forceps Trays
      2. Special
        1. Mahorner Thyroid Retractor Tray (available only)
        2. Tracheotomy Tray (available only)
        3. Maloney Esophageal Bougie Instrument Tray
        4. J/P bulb (250mL); fully-perforated 10cm Jackson-Pratt suction drain
        5. Gelpi self-retaining retractors
    3. Medications (specific to nursing)
      1. Antibiotic ointment
      2. 1% lidocaine with 1:100,000 epinephrine
    4. Prep and Drape
      1. Standard prep using noniodine solution
      2. Drape
        1. Head drape
        2. Square off with towels around neck, including chin, to 5 cm below clavicles laterally to trapezius muscles
        3. Split sheet
    5. Drains and Dressings
      1. Varidyne vacuum suction: 10 mm, Jackson-Pratt bulb drains, or Penrose drains (x 2)
      2. Antibiotic ointment to suture lines
      3. Pressure dressing: Fluffs, Kerlix, burn netting
  • ANESTHESIA CONSIDERATIONS
    1. General
      1. Patient supine with shoulder roll
    2. Specific
      1. No paralysis
      2. Intraoperative RLN monitoring has become increasingly common, but is still not considered by all to represent the standard of care. Several studies have failed to show significantly lower rates of RLN paresis or paralysis using intraoperative monitoring. It is thought to be most useful in advanced stage or in reoperative situations.  When performed, a special Laryngeal Monitoring Tube (LMT) tube is placed, with typically a 7.0 tube used for males, and 6.0 tube used for females. See Otolaryngol Head Neck Surg 2004 Nov;131(5):596-600 and Surgery 2004 Dec;136(6):1310-22.
  • RELEVANT ANATOMY
    a. A detailed knowledge of the embryology of parathyroid glands is helpful when only 3 normal glands have been found and the pathologic gland has not been located. The development of the parathyroid glands and thymus gland is specifically related to the embryology of the third and fourth branchial arches. Since the 2 inferior parathyroid glands are derived from the third branchial arch, they are pulled caudally with the migrating thymus in the fifth week of development and may descend into the mediastinum. If an adenoma is suspected in a lower gland that has not been found, it is probably located in the superior mediastinum or thymus. Occasionally, the lower gland can be located as low as the aortic arch. Parathyroid adenomas occur in the inferior glands twice as often as in the superior glands.
    The location of the superior parathyroid glands is more variable. At times, they can even be located inferior to the inferior glands and have been identified in locations between the skull base and the aortopulmonary window in the posterior mediastinum. A missing superior gland, derived from the fourth branchial arch, is embryologically related to the cricothyroid muscle, pharyngeal constrictors, and superior laryngeal nerve, since the superior gland is embryologically located in the wall of the pharynx.
    Since the fourth arch vessel is the common carotid artery, the ectopic superior gland may be located in the retroesophageal space, posterior mediastinum, or retropharyngeal areas (if still attached to the pharynx) or within the carotid sheath. This knowledge is also useful when 4 normal glands have been identified and the adenoma remains at large, necessitating exploration of an ectopic site to locate the missing adenoma. It may also be located within the posterior thyroid capsule or the parenchyma of the thyroid lobe, requiring hemithyroidectomy.
    In straightforward cases, an inferior adenoma is quickly identified relatively superficially in the space just lateral to the veins at the inferior thyroid pole. The most common location of the inferior gland is caudal to the inferior thyroid artery (ITA) and medial and anterior to the recurrent laryngeal nerve (RLN). The superior gland is typically located on the undersurface of the thyroid lobe superior to the ITA and lateral to the plane of the RLN.
  • OPERATIVE PROCEDURE
    1. Typically a  low collar incision one finger breadth above the clavicle and approximately the length between the lateral borders of the SCMs
      1. If there is a localizing scan consideration can be made to extend incision more to the side of the adenoma
      2. Dissection continues through the platysmal muscle, and the subplatysmal flaps are raised. If a localization study suggests a unilateral abnormality (see above), then the thyroid is mobilized first on that side.
      3. Dissection continues along the thyroid capsule, and the thyroid gland is rotated anteriorly and medially. If a preoperative localization study suggested either a superior or inferior gland, the corresponding area is examined first.
      4. The location of the superior parathyroid gland is sought on the posterior and lateral aspect of the thyroid gland. The middle thyroid veins are ligated, and the gland is rotated. The superior gland should be located deep to the plane of the recurrent laryngeal nerve and superior to the intersection of the recurrent laryngeal nerve and the inferior thyroid artery. The superior gland is often within 1 cm of the cricothyroid cartilage articulation. Blunt dissection of the fibroareolar tissue in this area facilitates finding both normal and abnormal parathyroid glands.
      5. Care should be taken to maintain excellent hemostasis, because blood that stains the tissue makes identifying the parathyroid glands harder and increases the risk of injury to the recurrent laryngeal nerve. Often, there is a covering layer of fascia just superficial to the parathyroid gland; once this is divided, the parathyroid gland generally presents itself with gentle blunt palpation in this area.
      6. The clefts within the thyroid gland are carefully examined to confirm that the parathyroid gland is not within a cleft and to make sure that the parathyroid gland has not been accidentally caught within the retractor and is not being retracted with the thyroid. If the superior gland is still not found, exploration proceeds to the common ectopic locations.
      7. Although identification of the recurrent laryngeal nerve is not always necessary, it is important and often helpful in cases in which a gland cannot be found. The superior gland is posterior to the plane of the recurrent laryngeal nerve and can often be found in the tracheoesophageal groove, in the posterior mediastinum, or adjacent or posterior to the esophagus. If additional exposure is needed, the superior thyroid artery can be ligated as it enters the superior aspect of the thyroid, and the thyroid gland can be further rotated anteromedially.
      8. In addition, it is sometimes helpful to divide the sternothyroid muscle. Often, an abnormal gland can be palpated before it can be seen. This is especially true of the superior glands, which migrate to posterior and deep locations. Finger palpation along the tracheoesophageal groove and along the esophagus down into the posterior mediastinum may lead to the area where dissection is needed to find the abnormal gland.
      9.  Most normal parathyroid glands are light brown in color; this coloration helps distinguish them from the surrounding fat, which is more yellow. The parathyroid glands can often be teased out of the fat by means of gentle palpation with a Kittner or peanut dissector.
      10.  The search for the inferior gland begins at the inferior and posterior aspect of the thyroid lobe and should include the thyrothymic ligament and the superior aspect of the thymus. The inferior gland is typically anterior to the plane of the recurrent laryngeal nerve and is often found just medial and anterior to the intersection of the recurrent laryngeal nerve and the inferior thyroid artery. With gentle retraction, the ectopic inferior gland can usually be pulled up into the neck and removed.
      11. If a normal parathyroid gland is inadvertently devascularized during the dissection, it should be set aside in saline for later reimplantation. The gland should be cut into 1 mm cubes and placed in 1 or more small pockets that are made within the sternocleidomastoid muscle. The area should be marked with nonabsorbable suture (eg, polypropylene) and with staple clips; this facilitates imaging and intraoperative identification should the patient becomes hyperparathyroid again in the future.
      12. After dissection is complete, and abnormal gland(s) have been identified and removed, the wound is irrigated and closed in similar fashion to thyroidectomy: re-approximation of the strap muscles, deep dermal sutures to re-approximate the platysmal layer and a running subcuticular closure of the epidermis.
  • The importance of the Inferior thyroid artery: In non-ectopic parathyroids the location of the superior glands are superior to the intersection of the inferior thyroid artery and the RLN, and the inferior glands below this intersection.
    1. Usually the middle thyroid vein requires ligation for medial mobilization of the thyroid to allow exploration.
    2. Obviously in cases of malignancy important to not violate capsule of gland but also in benign disease to prevent parathyromatosis (multiple nodules of hyperfunctioning parathyroid tissue scattered through the neck and mediastinum).  
    3. If intraoperative PTH is not available and/or as means to confirm gland removal pathology review is critical for removed specimen 
    4. PTH should fall at least 50% in cases of successful single adenoma disease (or should fall into normal range), though the half life of PTH is roughly 5-8 minutes it is advised to wait at least 15 to 20 minutes before post-excision redraw of PTH as manipulation of gland during removal can lead to spike in PTH temporarily confounding levels. 
    5.  Failure of the PTH to fall to expected levels following removal of a suspected adenoma should prompt the search for additional adenomas via four-gland exploration with removal of up to 3.5 glands.
       

      Surgical Images

         
       

      Parathyroid Adenoma Specimens

         
       
  • POSTOPERATIVE CARE
    1. Hungry bone syndrome is hypocalcemia that occurs after surgical removal of a hyperactive parathyroid gland.
      1.  Patients may experience transient HYPOcalcemia, and may present with weakess, tetany or perioral numbness/tingling sensation.
      2. Patients are typically discharged on POD 1 with or without a suction drain in place.
      3. Patients are instructed to keep their incision sites clean and dry. Suture removal is usually not necessary, as wounds are typically closed with a running subcuticular closure using 4-0 monocryl.
    2. All patients are encouraged to be up and active as soon as possible after surgery
  • Patients should elevate the head of their bed 30-45 degrees or sleep in a recliner at 30-45 degrees for the first 3-4 days to decrease swelling.
  • SUGGESTED READING
    1. Lafferty FW Differential diagnosis of hypercalcemia. Bone Miner Res. 1991 Oct;6 Suppl 2:S51-9; discussion S61.
    2. Felger EA, Kandil E. Primary hyperparathyroidism. Otolaryngol Clin North Am. 2010 Apr;43(2):417-32
    3. Pellitteri PK. Evaluation of hypercalcemia in relation to hyperparathyroidism.  Otolaryngol Clin North Am. 2010 Apr;43(2):389-97, x.
    4. Lew JI and Solorzano CC: Surgical Management of Primary Hyperparathyroidism: State of the Art in Surgical Clinics of North America - vol 89, Issue 5(October 2009)
    5. Consensus development conference statement. J Bone Miner Res. 1991;
      6:S9--S13.
    6. Eigelberger MS, Cheah WK, Ituarte PH, Streja L, Duh QY, Clark OH. The NIH criteria for parathyroidectomy in asymptomatic primary hyperparathyroidism: are they too limited? Ann Surg. 2004 Apr;239(4):528-35.
    7. Operative Otolaryngology Head and Neck Surgery 2nd Edition.  Eugene Myers. 2008