Biomedical subjects

L Delbridge

Publications and source records attributed to L Delbridge.

At least 37 records · Page 2Linked to original sources

PubMed1995

Computerized consensus diagnosis: a classification strategy for the robust analysis of MR spectra. I. Application to 1H spectra of thyroid neoplasms.

We introduce and apply a new classification strategy we call computerized consensus diagnosis (CCD). Its purpose is to provide robust, reliable classification of biomedical data. The strategy involves the cross-validated training of several classifiers of diverse conceptual and methodological origin on the same data, and appropriately combining their outcomes. The strategy is tested on proton magnetic resonance spectra of human thyroid biopsies, which are successfully allocated to normal or carcinoma classes. We used Linear Discriminant Analysis, a Neural Net-based method, and Genetic Programming as independent classifiers on two spectral regions, and chose the median of the six classification outcomes as the consensus. This procedure yielded 100% specificity and 100% sensitivity on the training sets, and 100% specificity and 98% sensitivity on samples of known malignancy in the test sets. We discuss the necessary steps any classification approach must take to guarantee reliability, and stress the importance of fuzziness and undecidability in robust classification.

Adenocarcinoma, Follicular↗

PubMed1995

Papillary thyroid carcinoma arising in thyroglossal duct cysts: incidence and management.

The incidence and pathological features of papillary thyroid carcinoma arising in the thyroglossal duct cysts were reviewed and compared with papillary thyroid carcinoma arising elsewhere in the thyroid gland. In the 30 year period 1964 to 1993 there were 90 thyroglossal duct nodules or cysts treated surgically at the Endocrine Surgical Unit, Royal North Shore Hospital, Sydney, Australia. There were four cases of papillary thyroid carcinoma in this group (4.4%). In the same period 2814 cases presented with clinical single thyroid nodules which were treated surgically. There were 182 cancers in this group of which 121 were papillary thyroid carcinomas (4.3% of total cases). This is identical to the incidence seen in the thyroglossal duct. We conclude that the incidence of papillary thyroid carcinoma arising in the thyroglossal duct is no different to that arising elsewhere in the gland. The difference in number of carcinomas related only to the volume of follicular thyroid tissue present in the gland proper. That being the case, there is no reason to treat these cancers differently from papillary thyroid carcinoma elsewhere in the gland.

Adult↗

PubMed1995

Giant double parathyroid adenoma presenting as a hypercalcaemic crisis.

The largest documented case of a double parathyroid adenoma is reported. The patient presented in hypercalcaemic crisis with a large intrathoracic mass. After removal of a massive cystic parathyroid adenoma from the right superior mediastinum, a second very large parathyroid adenoma was found on the contralateral side adjacent to the left thyroid lobe. This case illustrates the importance of the cervical approach, as well as routine bilateral neck exploration, for all cases of primary hyperparathyroidism.

Adenoma↗

PubMed1995

Diagnosis of follicular thyroid lesions by proton magnetic resonance on fine needle biopsy.

Most thyroidectomies are currently performed for diagnostic purposes. It has been established that proton magnetic resonance spectroscopy (MRS) on excised thyroid tissue can distinguish normal thyroid from invasive carcinomas (P < 0.0001). The purpose of this study was to assess whether the same discrimination could be obtained preoperatively from fine needle biopsy (FNB). This has clinical importance because cytological examination of fine needle aspirates cannot distinguish between benign and malignant follicular thyroid lesions. Here we demonstrate a sensitivity of 95% for proton MRS to correctly identify clinically or histologically proven carcinoma. MRS measurements were made on FNB specimens (containing as few as 10(6) cells) from solitary thyroid nodules. MR assessment of FNB was inconsistent with that of the corresponding tissue in only 6.5% of cases. The discrimination between cancer and normal tissue was based on altered cellular chemistry measured as a one-dimensional spectral ratio of resonances from the amino acid lysine and lipid. Benign follicular lesions were separated into two groups: 67% with a spectral ratio similar to malignant thyroid tumors, and 33% with a spectral ratio comparable to that in normal thyroid tissue. Thus, in contrast with histopathology, MRS offers a method for assessment of FNB of follicular lesions with the potential to identify a biologically benign group, which could avoid thyroid surgery for purely diagnostic purposes.

Adenocarcinoma, Follicular↗

PubMed1994

Can total thyroidectomy be performed as safely by general surgeons in provincial centers as by surgeons in specialized endocrine surgical units? Making the case for surgical training.

OBJECTIVE: To determine whether surgeons who had received appropriate training in the technique of total thyroidectomy could continue to perform the procedure with minimal morbidity after moving to a provincial surgical practice. DESIGN: Comparison of the complication rates from total thyroidectomy between a specialized endocrine surgical unit and provincial centers. SETTING AND PATIENTS: Six hundred fifty patients undergoing total thyroidectomy by two surgeons over a 5-year period in the endocrine surgical unit at Royal North Shore Hospital, St Leonards, Australia, were compared with 120 patients undergoing total thyroidectomy by seven provincial surgeons who were former trainees in the unit. MAIN OUTCOME MEASURES: Indications for surgery and specific complications of thyroidectomy including recurrent laryngeal nerve palsy, permanent hypoparathyroidism, and postoperative bleeding. RESULTS: Each of the seven surgeons in provincial practice performed only between two and 16 thyroidectomies annually. The percentage of total thyroidectomies for benign and malignant disease was identical for both the endocrine surgical unit and provincial center groups (44%). There was no difference in the incidence of recurrent laryngeal nerve palsy, permanent hypoparathyroidism, or postoperative bleeding between the two groups. CONCLUSION: Total thyroidectomy is an operation that always engenders controversy relating to the morbidity of recurrent laryngeal nerve and parathyroid injury. Surgeons who have completed a well-designed training program and who have become proficient at total thyroidectomy as trainees will remain proficient at the procedure despite practicing in a provincial center. Achieving a low morbidity rate demands meticulous attention to operative technique and anatomical detail.

Clinical Competence↗

PubMed1994

Intracellular Ca2+ inactivates an outwardly rectifying K+ current in human adenomatous parathyroid cells.

We have used whole-cell patch-clamp techniques to study the conductances in the plasma membranes of human parathyroid cells. With a KCl-rich pipette solution containing Ca2+ buffered to a concentration of 0.1 mumol/l, the zero current potential was -71.1 +/- 0.5 mV (n = 19) and the whole-cell current/voltage (I/V) relation had an inwardly rectifying and an outwardly rectifying component. The inwardly rectifying current activated instantaneously on hyperpolarization of the plasma membrane to potentials more negative than -80 mV, and a semi-logarithmic plot of the reversal potential of the inward current (estimated by extrapolation from the range in which it was linear) as a function of extracellular K+ concentration ([K+]o) revealed a linear relation with a slope of 64 mV per decade change in [K+]o, which is not significantly different from the Nernstian slope, demonstrating that the current was carried by K+ ions. The conductance exhibited a square root dependence on [K+]o as has been observed for inward rectifiers in other tissues. The current was blocked by the presence of Ba2+ (1 mmol/l) or Cs+ (1.5 mmol/l) in the bath. The outwardly rectifying current was activated by depolarization of the membrane potential to potentials more positive than -20 mV. It was inhibited by replacement of pipette K+ with Cs+, indicating that it also was a K+ current: it was partially (42%) blocked when tetraethylammonium (TEA+, 10 mmol/l) was added to the bath.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗

PubMed1994

Proton magnetic resonance and human thyroid neoplasia. I: Discrimination between benign and malignant neoplasms.

PURPOSE: Thyroid nodules are very common, yet the vast majority are biologically benign. The extreme difficulty facing the clinician selecting potentially malignant thyroid nodules for surgery was the subject of a recent editorial by Ernest L. Mazzaferri in the American Journal of Medicine (93:359-362, 1992). Here we evaluate the potential of proton magnetic resonance spectroscopy (1H MRS) to provide a solution to this problem. PATIENTS: Thyroid tissue from fifty-three patients undergoing partial or total thyroidectomy for solitary thyroid nodules were assessed by 1H MRS. RESULTS: When compared with the histologic diagnosis, 1H MRS distinguished normal thyroid tissue (n = 8) from invasive papillary (n = 9), anaplastic (n = 1), and medullary (n = 1) carcinomas with P values of < 0.0001, based on altered cellular chemistry. The same magnetic resonance (MR) criteria categorized pathologically proven follicular carcinoma (n = 8) (established as such by the presence of capsular or vascular invasion at the periphery of the tumor, or by the presence of metastases in the patient) with the other thyroid cancers (P < 0.0001). All other "benign" follicular neoplasms (n = 34), including five atypical follicular adenomas, were assessed by the same 1H MRS criteria and found to fit into one of the two above categories, viz. analogous to benign or malignant thyroid tissue. CONCLUSIONS: Proton MRS has the potential to separate out a group of truly benign follicular neoplasms from follicular tumors (both follicular adenomas and follicular carcinomas) that have an atypical follicular pattern on cytologic examination. This is the first report of an objective diagnostic procedure that has the potential to obviate surgical excision in a significant number of patients with benign follicular adenomas, independent of exhaustive histopathologic assessment.

Adenoma↗

PubMed1994

Thyroid nodules in childhood and adolescence.

Thyroid nodules are uncommon in the paediatric age group. One hundred and twenty-two children and adolescents underwent thyroidectomy for nodular thyroid disease in the Endocrine Surgical Unit at the Royal North Shore Hospital over a 37 year period. In the adolescent age group (13-18 years) 99 thyroidectomies were performed and the pattern of thyroid disease was similar to that seen in adults. In the prepubertal are group (0-12 years), the major difference was the high incidence of thyroid malignancy, especially in males. Of 23 prepubertal children undergoing thyroidectomy for nodular disease, malignancy was found in 38% of boys and 13% of girls. Multicentric papillary cancer (66%) and cervical lymph node metastases (80%) were very common, despite which the long-term survival was excellent.

Adolescent↗

PubMed1994

Adrenalectomy: expanded indications for the extraperitoneal approach.

The adrenal glands can be removed surgically by the anterior transperitoneal approach, or by the extraperitoneal approaches, either posteriorly or posterolaterally. While the extraperitoneal routes have become accepted as the preferred approach to the adrenal glands for small benign cortical adenomas, many authors still recommend the anterior transperitoneal route as the preferred operative approach for phaeochromocytoma, large tumours, adrenal cancers or bilateral hyperplasia. A series of 51 consecutive adrenalectomies performed for a wide range of adrenal disorders is presented, including phaeochromocytoma and large malignant tumours. In 47 cases the tumours were successfully removed through an extraperitoneal approach, with minimal morbidity. The anterior approach had to be employed in only four cases, and in three of these there was pre-operative evidence of tumour invasion into either the major vessels or the liver. The extraperitoneal approach to the adrenal gland is technically simple and can be performed quickly, with a low postoperative morbidity and should be regarded as the routine approach for almost all adrenal procedures.

Adrenal Cortex Neoplasms↗

PubMed1994

Pharmacological characterization of the nucleotide receptors that mobilize Ca2+ ions in human parathyroid cells.

We have used the fluorescent probe fura-2 to perform agonist studies of the receptor(s) that mobilizes Ca2+ ions in response to extracellular ATP in human parathyroid cells. Extracellular ATP induced Ca2+ responses in both normal and adenomatous parathyroid cells. Activation resulted in an initial small transient response during which Ca2+ ions were released from intracellular stores, followed by a prominent plateau response during which Ca2+ ions entered the cells from the extracellular fluid. The responses exhibited moderate desensitization upon repeated stimulation with ATP, and the ratio of the plateau to the peak response remained constant for any given group of activated cells. The baseline intracellular calcium concentration was 100 +/- 4.3 nM (mean +/- S.E.M., n = 3). Following maximal activation by extracellular ATP it rose to a peak of 684 +/- 45.7 nM (n = 3) and a plateau level of 415 +/- 9.9 nM (n = 3). We examined the effects of a variety of nucleotide species. The order of potency was: adenosine, AMP < alpha, beta-methylene ATP < ADP < ATP approximately UTP. In the concentration range 1-1000 microM, UTP (the concentration of agonist inducing a half-maximal response, EC50 = 2.4 microM) was slightly more potent than ATP (EC50 = 3.6 microM), and the two nucleotides evoked similar maximal responses. In the concentration range 0.01-1.0 microM, however, there was a clear difference in the behaviour of the two nucleotides. In particular, ATP, but not UTP, evoked responses that suggested the presence of a second receptor of higher potency but markedly lower efficacy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗

PubMed1994

Extraperitoneal 'laparoscopic' adrenalectomy.

The technique of extraperitoneal 'laparoscopic' adrenalectomy is described in two cases, a left sided 1 cm Conn's tumour and a right sided 3.5 cm incidental non-functioning tumour. The extraperitoneal approach has the advantage of direct access to the adrenal gland without the need to mobilize abdominal organs, while maintaining all the advantages of minimal access surgery.

Adrenal Gland Neoplasms↗

PubMed1993

An inwardly rectifying K+ channel in human adenomatous parathyroid cells.

The ion channel populations of cells prepared from human adenomatous parathyroid glands have been investigated using standard patch-clamp techniques with pipettes containing isotonic K(+)-rich solutions. The principal channel type observed was an inwardly rectifying K+ channel of 35 pS conductance. In addition, we have frequently observed a lower conductance (12 pS) K+ channel that appeared to conduct current in both directions. In addition to these K+ channels, we have observed non-selective cation channels and possibly CI- channels. Although we have observed occasional current transitions that might have arisen from a large conductance K+ channel similar to that observed in rat and bovine parathyroid cells, we have not been able positively to identify such a channel in human parathyroid cells, either in cell-attached or in excised inside-out patches.

Adenoma↗

PubMed1993

The value of frozen section examination in planning surgery for follicular thyroid neoplasms.

Frozen section examination of follicular neoplasms of the thyroid has been claimed to be of little value in planning the extent of surgery. Clinical factors such as age, sex and tumour size are said to be more accurate predictors of malignancy. The aim of this study was to examine the respective value of clinical factors and frozen section in the surgical management of follicular thyroid neoplasms. A retrospective study of 735 patients with follicular neoplasms treated at Royal North Shore Hospital was undertaken. Factors assessed included clinical features, such as age and sex of the patients and tumour size, as well as findings at frozen section examination. No significant difference in sex distribution was demonstrated when comparing follicular adenoma with follicular carcinoma. There was a significant difference with respect to patient age between the two groups, but the large overlap in the distribution made this difference of no clinical value. In addition, there was no significant difference in tumour size when comparing follicular adenoma with carcinoma. On the other hand, review of frozen section results showed that 40% of patients with follicular carcinoma were positively identified by frozen section examination at initial surgery, with a false positive rate of less than 0.2%. It appears that clinical factors, such as age, sex and tumour size, are of little assistance in differentiating benign from malignant follicular neoplasms. Frozen section examination remains the most definitive tool in planning intra-operatively the extent of surgery for follicular neoplasms of the thyroid.

Adenoma↗

PubMed1992

Total thyroidectomy: its role in the management of thyroid disease.

Of 7812 patients treated for thyroid disease in the Endocrine Surgical Unit at the Royal North Shore Hospital, 825 underwent total thyroidectomy as an initial procedure. One third of these patients (269) were operated on for malignancy and the remaining 556 were treated for benign conditions such as multinodular goitre (405), Graves' Disease (79) and thyroiditis (45). The rate of recurrent laryngeal nerve palsy was 0.5% while permanent hypoparathyroidism occurred in 0.6% of cases, the low complication rate being due to the technique of capsular dissection employed in the Unit. The number of total thyroidectomies performed as a percentage of all thyroid operations has risen from 4% in 1970 to more than 40% in 1990. The majority of this increase has been due to surgery for multinodular goitre where the proportion of patients treated by total thyroidectomy now exceeds 80%. A similar but smaller increase has been seen in an analysis of the New South Wales figures for all other public and private hospitals. It is concluded that the complication rate from total thyroidectomy can no longer be used to argue against its use as the definitive operation for malignant disease of the thyroid. Furthermore, in view of the risks of re-operative surgery, total thyroidectomy should be considered the operation of choice for most benign disease affecting the whole thyroid gland such as multinodular goitre, thyroiditis, and in a significant number of goitres affected by thyrotoxicosis.

Adolescent↗

PubMed1992

Total thyroidectomy: the technique of capsular dissection.

This paper describes the technique of total thyroidectomy using capsular dissection. Total thyroidectomy is a safe straightforward anatomical procedure in which meticulous dissection can provide protection to the parathyroid glands and to the recurrent laryngeal nerve. This protection is achieved by using capsular dissection, hugging the gland and dividing the tertiary branches (i.e. the third order of division) of the vessels while dissecting the parathyroid glands with their vascular pedicles free from the thyroid surface, with minimal exposure of the recurrent laryngeal nerve and disturbance of its blood supply. Total thyroidectomy removes all visible thyroid tissue although it is permissible to leave a very small remnant of tissue (less than a fraction of a gram) in the region of the ligament of Berry in order to protect the recurrent laryngeal nerve and the blood supply to the parathyroid glands. This technique ensures that the incidence of complications, including permanent hypoparathyroidism and recurrent laryngeal nerve palsy, is reduced to a minimum.

History, 20th Century↗

PubMed1992

Microfollicular thyroid adenoma and congenital goitrous hypothyroidism.

Three patients with congenital goitrous hypothyroidism are reported. They were treated with adequate thyroxine replacement and developed well defined microfollicular thyroid adenomas despite being euthyroid clinically and biochemically throughout their clinical course. Patients with congenital goitrous hypothyroidism appear to be at increased risk of developing thyroid adenoma in childhood despite the use of replacement thyroxine treatment in physiological doses.

Adenoma↗

PubMed1992

Does Graves' disease or thyrotoxicosis affect the prognosis of thyroid cancer.

Twenty-one patients who underwent surgical treatment for thyrotoxicosis and who were found at operation to have thyroid cancer are presented. Sixteen had Graves' disease and 5 had toxic nodular goiter. The group with Graves' is compared with 110 euthyroid patients with thyroid cancer who underwent their initial surgery in the same time period and who were of the same age (+/- 1 yr) and sex as the patients with Graves' disease. None of the thyrotoxic patients died during follow-up of 2-24 yr or developed subsequent metastases. The 1 patient with a local lymph node metastasis has not shown evidence of recurrence. Hypoparathyroidism appeared as a complication in only 1 patient. The size of tumors in the patients with Graves' disease was significantly smaller than in the euthyroid group. The course of the disease in both the patients with Graves' disease and the thyrotoxic group as a whole was relatively benign. This series does not support the recent suggestions that thyroid cancer in patients with Graves' disease is more aggressive than in either patients with toxic nodular goiter or euthyroid subjects. Patients with Graves' disease and thyroid cancer should be treated identically to other patients with thyroid cancer. Therapy should consist of total thyroidectomy followed by a postoperative 131I scan. Residual tissue or metastases found on the scan should be ablated with 6 GBq 131I. The patient should receive a suppressive dose of T4.

Adult↗

PubMed1991

Longitudinal changes in forearm bone mineral content in primary hyperparathyroidism.

Forearm bone mineral content was measured in 28 patients with primary hyperparathyroidism before and 1 year after successful parathyroidectomy. The forearm bone mineral content rose from a mean value of 1.068 to 1.092 g/cm (P less than 0.05, paired t-test). Those patients with the lower initial values had the largest rise. In an additional study, the forearm bone mineral content was measured in 10 women over the age of 40 years (mean age 58.6 +/- 7.9SD years) with hyperparathyroidism before and for 2 years after successful parathyroidectomy and compared with the forearm bone mineral content measured over 2 years in 12 women (mean age 56.3 +/- 5.5SD years) with continuing hyperparathyroidism and with the forearm bone mineral content of 12 eucalcemic control women (mean age 58.8 +/- 8.2SD years), also measured over 2 years. The parathyroidectomized group gained bone, whereas the ongoing hyperparathyroid group and the eucalcemic control group lost bone. The difference between the parathyroidectomized group and the ongoing hyperparathyroid group was significant after 2 years (P less than 0.05). The percentage loss of forearm bone mineral in the eucalcemic control subjects was not significantly different from the percentage loss of forearm bone mineral in the ongoing hyperparathyroid group, although the initial mean bone mineral content in the eucalcemic group was significantly higher than in the ongoing hyperparathyroid group, suggesting that a possible determinant of bone mineral loss in women in this age group is the initial bone mineral content.

Adult↗