Nephrol Dial Transplant (1996) 11: 2504-2506
Teaching Point
Nephrology
Dialysis
Transplantation
(Section Editor: K. Kiihn)
Localization of ectopic parathyroid tissue: usefulness of 99mTc sestamibi
scanning in a dialysis patient with severe secondary hyperparathyroidism
J. Zingraff \ A. Leger2, H. Skhiri1, C. Billotey3, E. Sarfati4 and T. Driieke1
'INSERM U90, Departement de Nephrologie, and 2Service de Radio-Isotopes, Hopital Necker; 'Service Central de
Medecine Nucleaire, and 4Service de Chirurgie Viscerale, Hopital Saint Louis, Paris, France
A 45-year-old woman who had been maintained on
long-term haemodialysis for 5 years for end-stage renal
failure secondary to lupus nephritis was referred to
our department for the investigation and treatment of
severe secondary hyperparathyroidism. She complained of diffuse bone pain. An X-ray survey of her
skeleton showed overt resorption of the cortical bone
and blood biochemistry confirmed the hyperparathyroid state: increased values of plasma calcium
and phosphorus (2.95 and 2.9 mmol/1 respectively), an
alkaline phosphatase activity twice the upper limit of
the normal range, and a circulating parathyroid hormone level (PTH1-84) which was gradually increasing
from 1092 to 2000 pg/ml (normal, 10-65 pg/ml). She
was unresponsive to the medical management of this
complication. Therefore she underwent a first neck
surgery, which was believed to be a total parathyroidectomy (PTx), some months prior to admission. Four
glands were identified at their usual sites and removed
by the surgeon. The weight of the glands was 300, 100,
81 and 35 mg respectively. After a transient fall during
the immediate postoperative period, the plasma calcium increased again. At admission in our department
plasma calcium was 2.8 mmol/1, plasma phosphate
Left clavicle
2 mmol/1, and PTH1-84 1252 pg/ml. The patient
was almost crippled by severe osteoarticular pain.
Complementary investigations showed that the
i ^ y — 3 — Innominate vein
patient's lupus erythematosus was quiescent. However,
Carotid artery
severe hypothyroidism of unknown origin was documented, with a plasma TSH>100mU/l. Therefore
Int. jugular vein
supplementation with thyroid hormone was initiated.
Vertebra
The patient underwent several imaging procedures
to localize the site of the remaining, overfunctioning
parathyroid tissue, including ultrasonography, computed tomography (CT) scanning and 99mTc-sestamibi
scintigraphy. The ultrasonographic technique failed to
identify a supernumary gland. The presence of an
P = parathyroid ?
enlarged and nodular thyroid gland hindered the
(b)
interpretation of the observed signals. The CT scan
(Figure 1) was not conclusive either: it showed a 2-cm Fig. 1. a CT scan, cross-section of the upper chest at the infrathyroid
nodular formation in the infrathyroid position behind level, showing a voluminous retroclavicular mass that could be an
the left clavicle and in front of the common carotid ectopic parathyroid gland (P). b Schematic diagram of Figure la.
1996 European Renal Association-European Dialysis and Transplant Association
Localization of ectopic parathyroid tissue
artery, which was compatible with, but not confirmatory of, an ectopic parathyroid gland. In contrast, the
99m
Tc-sestamibi scan revealed a large tracer uptake
under the lower extremity of the left thyroid lobe.
Tracer kinetics were characteristic for parathyroid
tissue.
Guided by these results, the surgeon proceeded to a
second cervicotomy but failed to discover the suspected
5th gland. He even resected the left lobe of the thyroid
gland but was unable to identify any parathyroid
structure within the removed tissue. The day after this,
99m
Tc-sestamibi scintigraphy was repeated, this time
together with concomitantly projected anatomical
markers to localize the gland more precisely with
respect to surrounding structures (Figure 2). This
resulted in the discovery and resection of a voluminous
gland during repeat surgery the day thereafter. It was
lodged behind the first rib and the left clavicle. Several
fragments of the gland were frozen for cryopreservation. Light-microscopy examination of the remainder,
estimated to about one-quarter of the total gland,
showed a very dense, diffusely hyperplastic parathyroid
parenchyma, weighing 530 mg. Furthermore a tiny
parathyroid nodule could be identified inside the profoundly altered thyroid lobe that was removed 2 days
before. Plasma calcium fell rapidly to 1.65mmol/l at
the evening after repeat surgery. Plasma PTH1-84 was
61 pg/ml, i.e., within the limits of the normal range 5
days later.
The long-term management of chronic dialysis
patients with secondary hyperparathyroidism con-
(f)
Marking the cervical incision
(5)
Top of the sternal manubrium
(D
Mark on the sternum 6.5 cm distant from (5)
Fig. 2. Second phase of a 99"Tc-sestamibi scan with three topographic marks, illustrating an intensive tracer uptake near the left
sternoclavicular joint (arrow).
2505
tinues to cause considerable problems. Even in compliant individuals, medical therapy may ultimately fail to
control the disturbances of calcium-phosphate metabolism or may expose the patient to an unacceptable
risk of soft-tissue calcification. Parathyroid-cell proliferation probably changes from a polyclonal to a monoclonal type of growth in case of severe secondary
hyperparathyroidism [1]. This could explain the ultimate occurrence of resistance to medical treatment in
the majority of such patients [2]. With the lengthening
of dialysis treatment, the percentage of patients who
require surgery to correct parathyroid overfunction
increases steadily [3]. The incidence of persistent or
recurrent hyperparathyroidism after a first cervicotomy
has been reported to be high [4-6], ranging from 10
to 30% in large series of uraemic patients. If visualization of the enlarged glands is not mandatory prior to
a first surgical approach, reoperation should always be
guided by thoroughly documented investigations in
order to localize the remaining gland (s) precisely.
Ultrasonography of the neck, when performed by
an experienced radiologist, gives generally useful
informations on the site and the size of a single
adenoma, or of several enlarged glands in case of
diffuse hyperplasia. However, the technique is usually
not able to detect ectopic glands, especially when they
are of retroclavicular or mediastinal location, and may
be constrained by locally modified anatomical conditions due to nodular alterations of the thyroid gland
or previous surgery.
Computerized tomography, double-labelling subtraction scintigraphy, and magnetic resonance imaging
are all non-invasive techniques that have been used
during the last decade for the preoperative identification of remaining parathyroid tissue.
All these methods have limited specificity and sensitivity [7]. Hence the systematic use of these investigations cannot be recommended for the detection of
residual parathyroid tissue after a first parathyroidectomy. Single labelling, double-phase scanning with
99m
Tc-sestamibi has been reported more recently as a
valuable tool to explore patients with primary hyperparathyroidism [7-9], prior to a first cervicotomy as
well as before reoperation. Extensive studies with this
technique have not yet been published in uraemic
patients with secondary hyperparathyroidism: in one
recent article, four chronic renal failure patients were
studied [7], and in another, seven patients with recurrent hyperparathyroidism after a total PTx with autotransplantation [10]. Altogether, there is a large
consensus as to the high specificity, almost 100%, of
the method. Sensitivity is rather good in case of a
single adenoma, but much less so when several glands
are enlarged, as is usually the case in severely hyperparathyroid end-stage renal failure patients maintained on
renal replacement therapy. Our own preliminary
experience is in agreement with this statement [11].
We have observed no false positive results. However,
prior to a first PTx, there is not sufficient indication
to perform 99mTc-sestamibi scintigraphy, since generally not all glands can be identified. In particular, this
2506
technique does not permit the provision of a separate
imaging of two neighbouring glands, even when they
are both greatly enlarged.
Teaching point
99m
Tc sestamibi scan is not indicated in secondary
hyperparathyroidism prior to a first parathyroidectomy, but is the method of choice to localize the
parathyroids in case of persistent or recurrent hyperparathyroidism.
References
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MIBI scanning to the identification of hyperfunctioning parathyroid tissue (Abstract). Nephrol Dial Transplant (in press)