Parathyroidectomy

See topic under 'anatomy' for localisation guide

To identify parathyroid tissue:

• 'Float sign' or 'wobble' - a rounded silhouette in the fatty tissues that bounces back or 'floats' upon gentle palpation
• Frozen section
• Aspiration of a small amount, injecting into 1mL saline, and measuring PTH in the sample
• IOPTH monitoring

Indications for bilateral exploration

• Surgeon preference
• Failure of focused exploration
• Known or intra-operatively identified parathyroid hyperplasia
• High suspicion of multi-gland disease (secondary and tertiary HPT, lithium-induced HPT, familial HPT)
• Discordant or negative pre-operative localisation studies

Intra-op PTH monitoring:

• Suggested timepoints:
  • Pre-incision
  • Pre-excision (after exposing the abnormal gland, but prior to ligating the blood supply)
  • 5 minutes after gland removal
  • 10 minutes after gland removal
• Miami Criteria
  • Decline of >50% at 10 minutes post-removal compared to the highest previous level, suggests cure and the case can be terminated
  • Can also require a normal PTH level to terminate the procedure
  • These criteria give a cure rate of 97-99%
• Obtain another level at 20 minutes if it doesn't fall into normal range as expected

Focused parathyroidectomy/minimally invasive parathyroidectomy (MIP)

• Choice of approach
  • Anterior is better for inferior adenomas, due to their more anterior location
  • Lateral approach good for superior glands that are located in a more posterior position in the neck, and for re-operative cases
• Anterior approach
  • Incise at or around the upper border of the thyroid isthmus, usually 2.5cm
  • Sub-platysmal flaps between thyroid cartilage and sternal notch
  • Separate strap muscles in the midline (cut through deep cervical fascia, starting near thyroid notch and moving caudally)
  • Separate ipsilateral sternohyoid muscle from the deeper sternothyroid - blunt dissection - proceeding laterally until ansa cervicales is visible at the lateral border of sternothyroid
  • Sternothyroid dissected from thyroid capsule
  • Elevate strap muscles and retract laterally
  • Retract thyroid medially
  • Divide middle thyroid vein
  • Identify RLN
  • Often find inferior adenoma prior to RLN
• Lateral approach
  • Placement of incision largely determined by the location of the adenoma - but usually centred along anterior border of SCM, about 2.5-4cm length
  • Elevate sub-platysmal flaps and place self-retainer
  • Incise superficial layer of deep cervical fascia along anterior border of SCM, developing plane in between lateral edge of sternothyroid and medial edge of SCM, then retract them apart
  • Omohyoid overlies IJV
  • IJV identified, and carotid can be palpated. At this point need to start moving medially onto thyroid.
  • Separate the space between anteromedial IJV and lateral thyroid
  • Should be able to access parathyroid location

Bilateral exploration

• Exposure of all four glands then comparison to decide if the patient has a single adenoma, four-gland hyperplasia, or double adenoma
• Continue on to look for ectopic glands if an abnormal parathyroid can't be identified
• All four glands abnormal: subtotal parathyroidectomy (removal of three glands and part of the fourth, leaving a remnant that is about 1-2x the size of a normal gland). The remnant should be fashioned, marked with a clip and check for viability prior to removing any others.

Dissecting parathyroid tissue

• Carefully dissect cirumferentially around a vascular pedicle, which is then ligated with suture, clip or Ligasure
• Avoid direct grasping - can cause parathyromatosis or tumour spillage

Unable to find the gland

• Superior
  • Upper pole of thyroid mobilised completely, including division of the ligament of Berry
  • Carotid sheath/trache-oesophageal groove
  • Along vagus nerve
  • Carotid bifurcation
  • Pharyngeal wall and retro-pharyngeal space (may need to increase incision)
  • Can incise thyroid capsule or do a hemithyroidectomy
• Inferior
  • Mobilise inferior pole of thyroid to assess thyrothymic ligament and thymus gland, taking care not to traction until fully mobilised to avoid shearing veins in thorax
  • Mobilise upper pole, then back along carotid/vagus to mandible
  • Can incise thyroid capsule or do a hemithyroidectomy
  • Probably don't do a sternotomy at first operation if not found, as removing some parathyroid tissue is often enough - close and re-image

If a normal parathyroid gland is devascularised

• Autotransplant into the ipsilateral SCM, a strap muscle, or the forearm, and its location marked with clips

Post-op

• Focused parathyroidectomy: Check calcium that afternoon, and calcium and PTH in the morning, aiming home the next day. See 'thyroidectomy' topic for full calcium protocol.
  • Normal PTH and calcium: Educate patients on symptoms of hypocalcaemia, and instruct them to take tablets and present to ED as needed
  • Mildly low calcium: start on regular calcium and vitamin D. Likely to be the result of suppression of the other glands.
• Bilateral exploration/biopsy: Check calcium that afternoon, and calcium and PTH in the morning
  • If PTH or calcium dropping, may want to keep for 48 hours until the nadir is reached

Complications

• RLN injury
• Hypoparathyroidism
  • Signs of hypocalcaemia: paraesthesiae, muscle spasms, tetany, seizures.
  • Check calcium that afternoon, and calcium and PTH in the morning
  • Transient hypocalcaemia is common after single gland removal, as other glands require stimulus of hypocalcaemia to begin functioning. Nadir is usually within the first 24-48 hours post-op. More common in those with severe hypercalcaemia and vitamin D deficiency pre-op. It is usually mild.
    • Mild - give 1500-2000mg calcium as carbonate or citrate, in divided doses
    • Oral vitamin D supplementation usually required to maximise GI absorption of calcium
  • Beware of patients with CKD having parathyroidectomy for secondary/tertiary hyperparathyroidism - see Austin guidelines - most likely need a calcium infusion post-op for hungry bone syndrome
• Parathyromatosis
  • Multiple parathyroid implants in the soft tissue of the neck
  • Occurs with rupture of a gland
  • Causes chronic intractable hypercalcaemia
• Neck haematoma

Follow-up

• Check PTH, calcium and vitamin D levels at 2 week follow-up and then at 6 months
  • Common for PTH to mildly up with low normal calcium, as a result of vitamin D deficiency