Parathyroid Imaging and Hyperparathyroidism
A Case Study

By Mohammed Moinuddin, M.D., F.A.C.P..

A 41 year old white female was admitted with abdominal pain and fever. Subsequent workup including a CT scan of the abdomen (Fig. 1) showed acute pancreatitis and pseudocyst of the pancreas. During her workup, the EKG monitor strip showed bursts of wide QRS tachycardia. Serum Calcium was found to be 9.8 (high normal) but ionized Calcium was 5.36 (normal up to 5.3), parathormone level was 83 (10-65 normal). At this stage, she carried two diagnoses – acute pancreatitis with infected pseudocyst and primary hyperparathyroidism. Both of these conditions required surgery but the dilemma was which one to operate first. With the patient having cardiac complications of hypercalcemia, it was decided to proceed with parathyroidectomy first. To localize the parathyroid adenoma, a parathyroid scan was performed in Nuclear Medicine.

This (Fig. 2) showed a parathyroid adenoma at the thoracic inlet, near the left sternoclavicular joint. With this information, the patient was taken to surgery for neck exploration. At surgery, three parathyroid glands were identified and confirmed on biopsy. However, since the parathyroid scan showed adenoma near a sternoclavicular joint area, dissection was carried into this area. Parathyroid adenoma was found, removed and confirmed on frozen section (130 mg.). The parathyroid scan played a key role in this patient with partially ectopic adenoma. Without the scan, it would have resulted in failed surgery because of ectopic location. Second exploration in phase of continued hypercalcemia would have been a disaster. Post-op, the patient did well. Serum Calcium was normalized. Eight days later, the patient underwent pancreatic cyst jejunostomy with Roux-en-y anastomosis along with small bowel resection and primary anastomosis.

Comment:
This patient had two diseases, both requiring surgical treatment. The decision to take care of hyperparathyroidism first was based on metabolic derangements of hypercalcemia (mainly cardiac). In recent years, parathyroid imaging has been used frequently to localize the parathyroid adenoma. The causes of hyperparathyroidism in decreasing order of frequency are: adenoma (87%), hyperplasia (12%) and carcinoma (1%). Any of the imaging modalities can be used, such as ultrasonography, CT scanning, MRI for localization but Cardiolyte scintigraphy has become more popular because of its higher accuracy. It carries an accuracy of 70-90%. When this test is false negative, US, CT or MRI may be used. The indication of parathyroid scintigraphy is ectopic parathyroid adenoma which occurs in 5-7% of all cases of hyperparathyroidism. Therefore, in cases of failed surgery in whom parathyroid adenoma is anticipated in the chest or unusual locations, parathyroid scintigraphy can be very useful. Recently, many surgeons utilize parathyroid imaging for localization even before the first surgery to minimize the surgical/anesthesia times. Some surgeons even perform parathyroidectomy under local anesthesia with a short incision in one day surgery under local anesthesia thereby reducing the anesthesia /operating room expenses.

Two significant advances that have occurred in this area recently are worth mentioning. First, is the localization of parathyroid adenoma using gamma probe perioperatively. The patient receives the isotope intravenously and 60-90 minutes later sent to the OR. The surgeon searches the parathyroid adenoma with a small gamma probe (about the size of a thick pen), that detects radiation. The incision is made at that site and the parathyroid adenoma is excised. This procedure may only take 30-50 minutes. However, this procedure can miss an ectopic adenoma in the chest and therefore prior imaging may be very useful. Second, to ensure the success of the parathyroidectomy, serum parathormone levels are measured immediately and 10 minutes after the parathyroidectomy. A drop in parathormone level by 50% ensures a surgical cure (PTH has a very short half life of less than 5 minutes).