Hyperparathyroidism is identified by direct assay of the circulating intact parathyroid hormone (iPTH). This leads to loss of regulation of calcium levels and hypercalcemia. Osteoporosis may occur, and if untreated, there is an increased incidence of cancer of the breast, colon, kidney, or prostate. Surgical removal of the hypersecreting gland or glands is the best treatment. In some cases there is diffuse hyperactivity, and in others a single gland is implicated.

Before surgery, enlarged parathyroid glands may be identified by high-resolution ultrasonography, multislice contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI), and technetium-99m (^99mTc) sestamibi nuclear scanning.

In experienced hands, primary surgical excision is curative in 95% of cases, but only 64% of patients with secondary surgery show success.¹ Recently this outcome has been improved with the use of iPTH assays.² When the primary surgery fails, reoperative parathyroidectomy is often difficult and unsuccessful because of scarring and distortion of the tissue planes without localization of the site of excess parathyroid hormone secretion by selective venous sampling (SVS).

In a study of 228 consecutive patients with persistent/recurrent hyperparathyroidism, the single most common site of missed adenoma glands was in the tracheoesophageal groove in the superior compartment of the posterior mediastinum (27%). In this position, the glands may be adherent to the recurrent laryngeal nerve. Other ectopic sites for parathyroid adenomas in this group of patients were thymus (17%), intrathyroidal (10%), undescended glands (8.6%), carotid sheath (3.6%), and retroesophageal space (3.2%). The most sensitive and specific noninvasive imaging test was the ^99mTc-sestamibi subtraction scan, with 67% true-positive and no false-positive results. The rate of true-positive results for ultrasonography, CT, MRI, and technetium thallium scans was approximately 50%.³

The accuracy of SVS for localization of the residual adenomas ranges between 75% and 90%4,5 and is related to the skill and persistence of the operator. It is possible to combine ultrasonography and needle aspiration for parathyroid hormone assay to identify lymph nodes that are the major cause of false-positive scans with ultrasonography, CT, and MRI.⁶

Equipment

Catheter

A coaxial system is recommended because the normal anatomy is often disrupted by previous surgery, and the guide catheter helps prevent prolapse of the sampling catheter into the right atrium and ventricle. A 7F guide catheter 80 cm in length and an inner catheter of 4F external diameter and 100 cm long is used.

In complicated cases, a variety of catheter shapes tailored to the veins at the time may be required. Alternatively, a microcatheter may be used.

Guidewires

For general venous access, a Teflon-coated J-tip with a 1.5-mm curve radius (0.035-inch) diameter and that is 145 cm long (Cook Medical, Bloomington, Ind.) is used with a standard 0.035-inch angled guidewire (Glidewire, Terumo Medical Corp., Somerset, N.J.).

Deflecting tip wires and torque wires may also be required in difficult cases.

A fine-gauge guidewire (0.018-inch diameter) may be used with a Tuohy-Borst adapter to prevent the 4F catheter tip from obstructing on the vein wall when a sample is obtained from small veins.

Contrast Medium

Iodine, 300 mg/mL, is used. The volume and rate depend on the site of the injection and can be gauged from test injections. Hand injections only are used for filming.

Exposure Sequence

With digital subtraction angiography, two exposures per second for 1 to 2 seconds are obtained. Often this will demonstrate other nearby veins that should also be sampled.

Other Equipment

An ice bucket for the blood samples is required because all samples (usually 20-25) should be placed immediately on ice and transported to the laboratory with a vein diagram (Fig. 110-1) as soon as possible after the procedure.

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