Diagnostic ultrasound ( PDFDrive )

CHAPTER 20 The Parathyroid Glands 749
T
Tr
T
C
T
T
A B C
FIG. 20.19 Parathyroid Adenoma: Correlation of Ultrasound and MRI. (A) Longitudinal and (B) transverse sonograms show superior
parathyroid adenoma (arrows) posterior to upper-middle portion of left lobe of the thyroid (T). C, Common carotid artery; Tr, trachea. (C) T2-weighted
fast spin-echo axial MRI of the neck shows the same left superior parathyroid adenoma (arrow), which appears hyperintense compared with the
thyroid gland.
Importance of Imaging in Primary
Hyperparathyroidism
Primary hyperparathyroidism is commonly clinically recognized,
and both clinicians and patients desire deinitive treatment for
it. Deinitive cure of primary hyperparathyroidism requires
surgical parathyroidectomy, which can be accomplished with a
very high degree of success and minimal morbidity when performed
by an experienced surgeon. 24,25,27 Historically, the standard
surgical procedure involved open bilateral neck dissection with
inspection of each parathyroid gland, and routine preoperative
imaging was not considered necessary.
Minimally invasive surgical techniques, termed minimalaccess
parathyroidectomy (MAP), now predominate as standard
surgical technique for irst-time surgery in primary hyperparathyroidism.
24,27,130-133 In MAP the abnormal gland or adenoma
is selectively removed through a small unilateral incision in the
neck, thereby potentially improving cosmesis, reducing complication
risks, and decreasing operative time, hospital stay, and overall
cost, oten without sacriicing signiicant operative eicacy when
performed by an experienced surgeon (Fig. 20.20). Moreover,
postsurgical ibrosis is limited to a smaller area, thus facilitating
any necessary repeat surgery in the future. he successful institution
of these minimally invasive techniques is predicated on the
availability of (1) accurate preoperative imaging techniques to
direct a focused surgical approach and (2) reliable, rapid (10-15
minutes) intraoperative parathyroid hormone monitoring,
which facilitates the surgical determination of the need for further
exploration. With intraoperative PTH monitoring the surgeon
can quickly assess the success of a focused unilateral approach.
If intraoperative PTH levels fail to normalize or decrease by at
least 50%, multigland disease should be suspected, and the
procedure may be converted to a bilateral dissection.
Many investigators promote the use of both anatomic and
functional imaging, such as ultrasound and 99m Tc sestamibi
scintigraphy, to increase the preoperative certainty of unilateral
disease and aid in excluding patients with multigland disease
who are not candidates for MAP. 19,62,82,84-86,103,104,110,112,113,116,129
Proponents of preoperative imaging in primary hyperparathyroidism
also note that some adenomas are found lower in the neck
or mediastinum and that the initial operative approach may be
changed or optimized if imaging shows parathyroid disease near
the thymus. 24,60,87,91
In patients with persistent or recurrent hyperparathyroidism,
localization studies are liberally used because of the lower surgical
success rate and the higher morbidity rate of reoperation.
Preoperative localization studies in recurrent hyperparathyroidism
contribute to both the success and the speed of the
repeat surgery. In patients who had reexploration for persistent
or recurrent hyperparathyroidism, the surgical cure rate was
88% to 89%, and it was thought that prospective localization
studies contributed to this high rate of success and decreased
surgical time. 57,59,60 Because most persistent and recurrent
parathyroid adenomas are accessible in the neck or the upper
mediastinum through a cervical incision, sonography and 99m Tc
sestamibi scintigraphy, particularly with SPECT or SPECT/CT,
may be the initial localizing procedures of choice and, in select
patients, can aid in directing a focused, minimal-access surgical
approach 44,59,60,62,64,92,100,103,110,111,113,115,116,129 (Fig. 20.21). However, low
threshold for additional diagnostic conirmation with ultrasoundguided
biopsy, 4D MDCT, and/or MRI is supported. 103,110,111,118,120
(Fig. 20.22).
INTRAOPERATIVE SONOGRAPHY
Intraoperative sonography is occasionally a useful adjunct in
the surgical detection of parathyroid adenomas, particularly in
the reoperative setting. 19,134,135 Intraoperative scanning can be
performed with a small, conventional, high-frequency (8-18 MHz)
transducer draped with a sterile plastic sheath or with a dedicated
sterilized intraoperative transducer. Intraoperative ultrasound
appears to be most useful for localizing abnormal inferior and
intrathyroid parathyroid glands. 135 Correlated with preoperative
imaging, intraoperative sonography can also help guide a focused
surgical resection to limit tissue damage associated with exploration
in the reoperated patient; it also allows directed resection
of ectopic adenomas in the mediastinum, thyroid, and carotid
sheath. If an abnormal parathyroid gland is detected, surgical
time can be shortened.