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PARATHYROID

Operation_technique_dr_john

Dr John Chaplin – Auckland Head and Neck Specialist

Parathyroidectomy, Minimally Invasive Parathyroidectomy

 

Hypercalcaemia

 

Hypercalcaemia is the medical word for a high level of calcium in the blood. This condition can occur in a number of different ways. The most common cause is primary hyperparathyroidism. (Over-active parathyroid glands, parathyroid disease)

Anatomy

 

Parathyroid Glands are usually four in number, they are quite small, only 4-9mm in size and they weigh only 40-70gm each. Typically they are closely associated with the thyroid gland and they are in predictable positions. The superior or upper glands are at the back of the thyroid at the level of the voice box (larynx). The inferior or lower glands are at the level of the bottom of the thyroid gland near the windpipe (trachea). Occasionally there are variations in the anatomy of these glands and they can occur in other positions in the neck and very rarely in the chest.

Pathology

 

Pathology_dr_johnThere are several abnormalities that can cause primary hyperparathyroidism. By far the most common (90% of cases) is a benign (non-cancerous) tumour in one of the parathyroid glands called a Parathyroid Adenoma. Next most common (5%) is a condition which can affect all of the parathyroid glands called Parathyroid Hyperplasia, this condition is sometimes associated with a rare genetic condition called multiple endocrine neoplasia or MEN. Sometimes there can be two or more parathyroid adenomas (4%) and the rarest cause is parathyroid cancer (1%).

Incidence

 

Primary hyperparathyroidism is quite common (incidence 30cases/100,000 population/year).The condition affects women three times more often than men and is more common in the older age groups.

Presentation

Most patients who have hypercalcaemia do not have any symptoms and the condition is diagnosed when the patient has a blood test that shows a higher than normal calcium level in the blood. Some people do, however, have symptoms and these may include: aching in the arms and legs, osteoporosis and bone fractures; kidney stones; stomach ulcers and abdominal pain; mental confusion. There are also a range of other more vague symptoms which may be caused by high calcium these include: dehydration, high blood pressure, tiredness and depression.

Investigation

 

If you have been diagnosed with a high calcium level in the blood your doctor will organise some other tests which may include:

  1. Blood tests
    1. Parathyroid hormone level
    2. Kidney function
    3. Alkaline phosphatase level
    4. Vitamin D level
  2. Urine Tests
    1. 24 hour urine calcium level
    2. Calcium/creatinine clearance ratio

The condition can ususally be differentiated from other conditions that may cause elevated calcium levels on these tests alone.

Treatment

Occasionally drugs are used to temporarily bring down the level of calcium if the patient is very symptomatic. The only definitive treatment, however, is surgical removal of the overactive parathyroid tissue.

Surgery

 

Surgery for hyperparathyroidism is a highly successful procedure with a very low complication rate if performed by an experienced surgeon.

The object of the operation is to locate and remove the overactive parathyroid tissue (usually one gland). In the past surgeons had the try and identify all four glands to ensure that only one was enlarged , they also used ultrasound, CT and MRI scans to try and localise an enlarged gland before the operation. These techniques were unreliable and the operation could be long and have increased risk of complications. There are some recent techniques that have been developed to help the surgeon to localise the abnormal gland both prior to and during the operation, which have allowed smaller incisions, shorter operations and more reliable outcomes. These include:

Sestamibi Scan:

Sestamibi_Scan_1_dr_johnSestamibi_Scan_2_dr_johna low dose radioactive label is attached to a protein that is taken up by overactive parathyroid tissue. The protein is injected and scans are taken at 10 minutes and 2 hours. The technique is quite reliable in cases where there is one overactive gland (90% of cases).

Rapid Parathyroid Hormone Assay:During the operation, while the patient is asleep blood tests are taken and sent urgently to the laboratory where they are put through an analyser that measures parathyroid hormone within a few minutes (rather than hours that it used to take). If the overactive parathyroid tissue is removed the level will drop significantly after 10 minutes. This is very reliable and correlates well with long term cure. Armed with these techniques an experiences surgeon can potentially increase the accuracy of exploration, reduce operative time, make smaller incisions and lower the complication rates for the surgery.

Operation technique

Operation_technique_dr_johnThe operation is performed through an incision in the front of the neck low down and usually in a skin crease. The thyroid gland is exposed and partially lifted out of the way to expose the parathyroid glands. The enlarged gland(s) are then removed completely. There are several important structures near the parathyroid glands that are at risk of injury during this type of surgery. Your surgeon will explain the risks of the operation to you. It is important to note that these complications are rare, they include:

Nerve Injury

There are two nerves that are close to the thyroid gland each side that allow the larynx (voice-box) to function. If these nerves, called the recurrent laryngeal nerve and the external laryngeal nerve, are injured during parathyroid surgery the character of your voice may change. This is very uncommon and any change is usually temporary.

Low Calcium Levels

Following parathyroidectomy there is a risk the calcium levels in your blood can fall. Calcium is important for nerve and muscle function and you may need to take calcium tablets if this happens. Again this is usually a temporary problem and the glands usually start to function again after a period.

Bleeding

As with any surgery bleeding can sometimes occur after the operation. If this happens your neck may swell and you may have to be taken back to the operating room to have the blood drained away.

Pain

Parathyroidectomy is not usually a painful operation, there may be some minor discomfort with swallowing and neck movement following surgery for a short time. Simple pain relieving medications are very effective.

You will generally need only one to two days in hospital following this operation and you may need your blood calcium levels checked during your stay. You may have a drain placed into the wound at the time of surgery, this is usually removed after one or two days. You will probably need about a week to recover before resuming normal activities.

 

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