The role of imaging techniques in the study of renal osteodystrophy.

Secondary hyperparathyroidism is the most common form of this condition found in renal osteodystrophy. Enlarged parathyroid glands are the rule in severe secondary hyperparathyroidism because of a marked parathyroid cell hyperplasia. For several years, ultrasonography, computed tomography, and scintigraphy with thallium201-technetium99 have been useful techniques to identify enlarged parathyroid glands. More recently, ultrasonography with color Doppler and parathyroid scintigraphy with 99mTc-sestamibi have proved to be useful as well. Computed tomography and magnetic resonance imaging can be used, but their sensitivity is similar to ultrasonography and they cost more. Ultrasonography with color Doppler signals has made it possible to evaluate tissue blood supply, an aid in differentiating thyroid nodules. The degree of blood supply may be an indirect index of cell proliferation when there is neither necrosis nor calcification, because an enriched blood supply suggests vigorous cell growth and nodule formation. Scintigraphy with 99mTc-sestamibi allows identification of ectopic glands, including those located in the mediastinum, and also provides functional information. Sestamibi uptake is closely related to both parathyroid hormone levels and to the histological type of parathyroid proliferation. In our experience, when hyperparathyroidism is not too severe, 2 weeks after 2 g of calcitriol is administered intravenously, these scintigraphic images can disappear (inhibition test). This suggests a possibility for a medical treatment. By contrast, when parathyroid hormone levels are higher, parathyroid sestamibi uptake remained unchanged. In such patients, parathyroidectomy or ethanol injection should be the best treatment. These glands would correspond to the most actively functioning glands; they would have a lesser expression of vitamin D receptors, rendering them refractory to medical treatment with calcitriol.

[(99m)Tc]-sestamibi parathyroid scintigraphy in chronic haemodialysis patients: static and dynamic explorations.

BACKGROUND: The place of parathyroid gland imaging by [(99m)Tc](technetium)-sestamibi scintigraphy in uraemic patients with secondary hyperparathyroidism remains a matter of debate. The purpose of the present study was (i) to assess its value with respect to plasma intact parathyroid hormone (iPTH) levels and to surgical parathyroidectomy (PTx), and (ii) to explore the possibility of suppressing parathyroid [(99m)Tc]-sestamibi uptake by calcitriol. METHODS: In a first cross-sectional, static study 52 chronic haemodialysis (HD) patients with plasma iPTH levels between 14 and 2791 pg/ml (normal, 10-65 pg/ml) had a [(99m)Tc]-sestamibi scan, and 21 of them underwent surgical PTx. In a second longitudinal, dynamic study 14 chronic HD patients with advanced secondary hyperparathyroidism received short-term calcitriol treatment in an attempt to suppress [(99m)Tc]-sestamibi imaging of parathyroid glands. Calcitriol was given intravenously for 2 weeks, 2 microg after each haemodialysis session. Scintigraphy was carried out before and at the end of this inhibition test. RESULTS: [(99m)Tc]-Sestamibi scan led to imaging of one or more (maximum three) parathyroid glands in most, but not all, HD patients with plasma iPTH values >600 pg/ml. Based on surgical findings, overall sensitivity of [(99m)Tc]-sestamibi scan in correctly locating parathyroid glands was only 50%, whereas specificity was 100%. In contrast, its sensitivity was 100% in locating single glands in the subgroup of five patients with recurrent hyperparathyroidism. The calcitriol inhibition test showed suppression of [(99m)Tc]-sestamibi uptake by at least one parathyroid gland in eight patients (57%), with complete suppression in five of them (36%). Basal plasma iPTH or decrease of plasma iPTH in response to calcitriol was not predictive of suppressible [(99m)Tc]-sestamibi uptake in the individual case, although mean iPTH was markedly higher in patients with non-suppressible parathyroid glands. CONCLUSION: Because of its relatively low sensitivity the [(99m)Tc]-sestamibi scan is of limited help in the exploration of uraemic patients with severe secondary hyperparathyroidism before a first surgical PTx. However, it is very useful in locating the remaining parathyroid gland(s) in case of reoperation. The novel calcitriol inhibition test of [(99m)Tc]-sestamibi uptake could help to better distinguish parathyroid glands with non-suppressible, autonomous activity from glands whose activity might be amenable to long-term suppression.

Can we use 99mTc-MIBI in functional studies of the parathyroid gland?

The usefulness of technetium-99m-sestamibi (99mTc-MIBI) in patients with secondary hyperparathyroidism on haemodialysis was assessed. We studied 33 patients with parathyroid scintigraphy with i.v. (99mTc-MIBI). Static images in a scintillation camera were taken at 15 and 120 min after the injection. With P x Ca<80, we performed an inhibition test with calcitriol i.v. 2 microg, three times a week, for 2 weeks. The MIBI study and assessment of intact parathyroid hormone (iPTH) were performed before (baseline study) and after inhibition. A 'focal positive study' corresponded to one or more areas of abnormal hypercaptation in relation to surrounding thyroid tissue seen in early images and persisting in later images, and a 'negative study' did not correspond to the previous image. In the baseline study, iPTH in the positive MIBI group was significantly greater than in the negative group. Eight positive MIBI patients had a bone biopsy; six corresponded to severe osteitis fibrosa and two to mild osteitis fibrosa. In the negative MIBI group, four of the six patients who had bone biopsy had mild forms of osteitis fibrosa (Fisher=0.03); the other two had low turnover forms. A positive inhibition test was defined when the basal uptake disappeared after calcitriol administration. In these patients, we observed a significant decrease of iPTH, not observed in the negative inhibition test. In 10 patients who had been parathyroidectomized, those with alpha positive basal MIBI result had a nodular parathyroid hyperplasia. We conclude that a scintigraphic parathyroid study with 99mTc-MIBI showed a good correlation with functional parathyroid status. With the same inhibition test, only some glands were inhibited, suggesting that this could be the expression of different vitamin D receptor densities in inhibited glands and/or a different kind of proliferation in those glands. This test would be of value in functional studies when a therapeutic decision must be made.

Radiopharmacological evaluation in dogs of a new renal function agent.

The hydrophilic penta-anionic complex [Technetium (Carboxymethylisocyanide)6]-5, [Tc(CNCH2COO-)6]-5 (Tc-CAMI) was synthesized to evaluate its potential as a renal function imaging agent. The compound contains six distally arranged carboxyl groups that can act as substrates for the organic acid receptor of the renal cell to effect tubular secretion of this agent. Dynamic gamma-camera imaging of 99mTc-CAMI was performed in normal dogs to compare its bio-distribution and pharmacokinetics with those of proven tubular secretion (99mTc-MAG3) and globular filtration (99mTc-DTPA) agents. The relative difference between the observed mean renal transit times (MRTT) of 99mTc-CAMI and 99mTc-MAG3 was 0.15 compared with 1.24 for 99mTc-CAMI and 99mTc-DTPA. Pathological models of obstructive uropathy, renal arterial stenosis and renal denervation were produced in the same animals to demonstrate the diagnostic potential of the agent. These experiments and data showing that probenecid competes with 99mTc-CAMI for renal transport indicate that this compound functions as a tubular secretion agent and may be useful for monitoring renal function in various disease states.

Exploración radisotopica de la función ventricular basal izquierda del tránsito esofágico, de la vía urinaria superior y de la función vesical en pacientes chagásicos cronicos predominantemente asintomáticos / Radioisotopic exploration of basal left ventricular function of the esophageal transit, of upper urinary duct and of bladder function of patients with chronic Chagas' disease predominantly en assymptomatic

Estudou-se em 56 pacientes chagásicos crônicos (45 assintomáticos e os restantes portadores de transtornos cardiovasculares e digestivos) a funçäo ventrícular esquerda (ejeçäo basal, motilidade parietal segmentar e o histograma); em 29 deles, o trânsito esofagiano e em outros 25 enfermos explorou-se a via urinária, respectivamente com o 99m - TC coloidal e o 99ml - TC b + PA. Observou-se que a fraçäo de ejeçäo do ventrículo esquerdo entre os indivíduos normais era de 0,66 + ou - 0,07, enquanto nos chagásicos crônicos com alteraçöes cardiovasculares (Grupo II) verificou-se 0,49 + ou - 0,21. A motilidade parietal esteve alterada em 60% do mesmo grupo de enfermos e o desvio standard do histograma foi de 1,98 + ou - 0,45, para 1,29 + ou - 0,17 no grupo de voluntários. O trânsito esofágico foi considerado normal em 9 casos e alterado em 20, sendo que em 6 foi do tipo prolongado, em 4 adinâmico e em 10 incoordenado. Nos 25 pacientes nos quais investigaram a via urinária superior, foi encontrada alteraçäo em 22 (dilataçäo piélica uni ou bilateral) e a funçäo vesical nestes pacientes foi normal em apenas quatro casos. Concluem os pesquisadores que o 99 - TC representa um grande avanço tecnológico no estudo da funçäo cardíaca, esofágica e das vias urinárias em pacientes chagásicos crônicos e assintomáticos

The use of radioiodinated alpha-fetoprotein for the scintigraphic detection of mouse mammary carcinomas.

Alpha-fetoprotein (AFP) is taken up by developing fetal cells but not by normal adult cells. This finding together with the resemblance between fetal cells and cancer cells suggests that malignant tissue could incorporate AFP in opposition to normal tissue. In the present work, we injected mice bearing spontaneous mammary adenocarcinomas with 131I-radioiodinated AFP. The scintigraphic images obtained with a gamma camera showed that 11 out of 12 carcinomas displayed strong radiolabelling with very low activity in the surrounding normal tissues. In addition, three non-neoplastic cystic lesions were found to be negative. The future implications of this result for tumour diagnosis, as well as the possible mechanisms of AFP uptake are discussed.

Centellografia osea y determinacion de parathormona en insuficientes renales en hemodialisis cronica. / Bone scintigraphy and parathormone determination in renal insufficiency in chronic hemodialysis

Con objetivo de brindar un aporte diagnostico a la interpretacion de las alteraciones del metabolismo fosfocalcico en la insuficiencia renal; se realizo el estudio combinado de PTH y centellograma oseo en un grupo de pacientes en hemodialisis cronica. Esta metodologia de estudio permitio clasificar humoralmente a los enfermos en tres grupos: normo, hipo o hipercalcemicos, frente al aumento de los niveles de PTH. A su vez la centellografia osea en la etapa prerradiologica subdividio al grupo en: normales (estadio 0), con hipercaptacion moderada (estadio I) y con hipercaptacion severa (estadio II)

Estudio de la perdida sanguinea intestinal (PSI) en relacion a la vida media globular y la fibrogastroscopia en insuficientes renales en hemodialisis cronica. / Intestinal blood loss (IBL) related to red cell life span and fibrogastroscopy in patients with renal insufficiency in chronic hemodialysis

Se estudiaron 10 pacientes con el objeto de analizar el valor de la determinacion de la perdida sanguinea intestinal (PSI), en los insuficientes renales en hemodialisis cronica. Se determino la P.S.I. y la vida media globular por medio de la marcacion del globulo rojo con 51Cr. A todos los pacientes se les realizaron estudios fibrogastroscopicos.Del analisis de los resultados se concluye que el estudio de PSI es de utilidad para el "Screening test" para cuantificar la magnitud de la perdida, para sustentar la indicacion de la fibrogastroscopia y para fundamentar la exploracion distal o la biopsia del tubo digestivo a los pacientes con insuficiencia renal cronica

Centellografia osea y determinacion de parathormona en insuficientes renales en hemodialisis cronica. / Bone scintigraphy and parathormone determination in renal insufficiency in chronic hemodialysis

Con objetivo de brindar un aporte diagnostico a la interpretacion de las alteraciones del metabolismo fosfocalcico en la insuficiencia renal; se realizo el estudio combinado de PTH y centellograma oseo en un grupo de pacientes en hemodialisis cronica. Esta metodologia de estudio permitio clasificar humoralmente a los enfermos en tres grupos: normo, hipo o hipercalcemicos, frente al aumento de los niveles de PTH. A su vez la centellografia osea en la etapa prerradiologica subdividio al grupo en: normales (estadio 0), con hipercaptacion moderada (estadio I) y con hipercaptacion severa (estadio II)

Estudio de la perdida sanguinea intestinal (PSI) en relacion a la vida media globular y la fibrogastroscopia en insuficientes renales en hemodialisis cronica. / Intestinal blood loss (IBL) related to red cell life span and fibrogastroscopy in patients with renal insufficiency in chronic hemodialysis

Se estudiaron 10 pacientes con el objeto de analizar el valor de la determinacion de la perdida sanguinea intestinal (PSI), en los insuficientes renales en hemodialisis cronica. Se determino la P.S.I. y la vida media globular por medio de la marcacion del globulo rojo con 51Cr. A todos los pacientes se les realizaron estudios fibrogastroscopicos.Del analisis de los resultados se concluye que el estudio de PSI es de utilidad para el "Screening test" para cuantificar la magnitud de la perdida, para sustentar la indicacion de la fibrogastroscopia y para fundamentar la exploracion distal o la biopsia del tubo digestivo a los pacientes con insuficiencia renal cronica