Laboratory simulations of the atmospheric mixed-layer in flow over complex topography.

A laboratory study of the influence of complex terrain on the interface between a well-mixed boundary layer and an elevated stratified layer was conducted in the towing-tank facility of the U.S. Environmental Protection Agency. The height of the mixed layer in the daytime boundary layer can have a strong influence on the concentration of pollutants within this layer. Deflections of streamlines at the height of the interface are primarily a function of hill Froude number (Fr), the ratio of mixed-layer height (z i ) to terrain height (h), and the crosswind dimension of the terrain. The magnitude of the deflections increases as Fr increases and z i /h decreases. For mixing-height streamlines that are initially below the terrain top, the response is linear with Fr; for those initially above the terrain feature the response to Fr is more complex. Once Fr exceeds about 2, the terrain-related response of the mixed layer interface decreases somewhat with increasing Fr (toward more neutral flow). Deflections are also shown to increase as the crosswind dimensions of the terrain increase. Comparisons with numerical modeling, limited field data, and other laboratory measurements reported in the literature are favorable. Additionally, visual observations of dye streamers suggest that the flow structure exhibited for our elevated inversions passing over three dimensional hills is similar to that reported in the literature for continuously stratified flow over two-dimensional hills.

Defining hypercalciuria in nephrolithiasis.

The classic definition of hypercalciuria, an upper normal limit of 200 mg/day, is based on a constant diet restricted in calcium, sodium, and animal protein; however, random diet data challenge this. Here our retrospective study determined the validity of the classic definition of hypercalciuria by comparing data from 39 publications analyzing urinary calcium excretion on a constant restricted diet and testing whether hypercalciuria could be defined when extraneous dietary influences were controlled. These papers encompassed 300 non-stone-forming patients, 208 patients with absorptive hypercalciuria type I (presumed due to high intestinal calcium absorption), and 234 stone formers without absorptive hypercalciuria; all evaluated on a constant restricted diet. In non-stone formers, the mean urinary calcium was well below 200 mg/day, and the mean for all patients was 127±46 mg/day with an upper limit of 219 mg/day. In absorptive hypercalciuria type I, the mean urinary calcium significantly exceeded 200 mg/day in all studies with a combined mean of 259±55 mg/day. Receiver operating characteristic curve analysis showed the optimal cutoff point for urinary calcium excretion was 172 mg/day on a restricted diet, a value that approximates the traditional limit of 200 mg/day. Thus, on a restricted diet, a clear demarcation was seen between urinary calcium excretion of kidney stone formers with absorptive hypercalciuria type I and normal individuals. When dietary variables are controlled, the classic definition of hypercalciuria of nephrolithiasis appears valid.

Effect of the Bethesda system for reporting thyroid cytopathology on thyroidectomy rates and malignancy risk in cytologically indeterminate lesions.

BACKGROUND: Cytologically indeterminate thyroid nodules represent a diagnostic and therapeutic challenge. In 2007, the National Cancer Institute recommended The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) as a means of improving the accuracy of thyroid cytopathology. Our objective was to determine the effect of TBSRTC on thyroidectomy rates and malignancy risk in cytologically indeterminate lesions. METHODS: We compared thyroidectomy rates and malignancy risk in patients with indeterminate thyroid cytopathology across 2 time periods, spanning January 2000 and November 2009; pre-TBSRTC (January 2000 to September 2003) and post-TBSRTC (June 2008 to November 2009). Statistical comparisons were performed using the Fisher's exact test and chi-square analysis (P = .05 significant). RESULTS: We performed 938 fine-needle aspirations in the first period, 765 in the second. We identified 78 (8.3%) cytologically indeterminate lesions in the pre-TBSRTC group and 91 (11.9%) lesions in the post-TBSRTC group. We found no difference in thyroidectomy rates between the groups (37/78 [47%] pre-Bethesda versus 32/91 [35%] post-Bethesda; P = .12). However, the malignancy rate was significantly lower in the post-TBSRTC group (13/37 [35%] pre-Bethesda versus 4/32 [13%] post-Bethesda; P = .02). CONCLUSION: Application of TBSRTC is associated with lower malignancy risk in indeterminate thyroid nodules, despite similar thyroidectomy rates. These findings imply that standardization of cytologic classification improves diagnostic accuracy.

Trends in thyroid cancer demographics and surgical therapy in the United States.

BACKGROUND: The incidence of thyroid cancer is increasing. Our objective was to characterize the demographic pattern of this increase and to examine trends in surgical therapy for thyroid cancer. METHODS: Analysis of the SEER and NHDS databases was performed from 1974 to 2000 and from 1979 to 2004, respectively. Thyroid-related diagnoses were extracted, and thyroid cancer (ICD 193.X) were analyzed using the SAS statistical package. We compared the population-adjusted incidence of thyroid cancer and examined regional variations in the operative therapy for thyroid cancer. RESULTS: The incidence of thyroid cancer has increased during the past 26 years. This increase occurred predominantly in women and in the Northeastern and Southern United States, whereas there has been a decrease in thyroid cancers in the Midwest. Papillary cancer accounts for most of this increase. Total thyroidectomy (TT) is now the most common operation for thyroid cancer. No differences in the use of TT were observed based on hospital size or insurance status. CONCLUSION: The increasing incidence of thyroid cancer in the United States is predominantly in women. These results suggest that women are a high-risk group for developing thyroid cancer although men have higher stage disease.

"Subclinical Cushing's syndrome" is not subclinical: improvement after adrenalectomy in 9 patients.

BACKGROUND: A subgroup of patients with adrenal cortisol hypersecretion fails to meet the biochemical criteria for Cushing's syndrome. Appropriate therapy for this entity, subclinical Cushing's syndrome (subclinical CS), is unclear. We examined outcomes for patients who underwent unilateral adrenalectomy for subclinical CS. METHODS: Between 2003 and 2006, all patients who underwent adrenalectomy for cortisol hypersecretion caused by an adrenal mass were examined. We analyzed biochemical, metabolic, and clinical outcomes. RESULTS: Overall, 24 patients underwent adrenalectomy for adrenal cortisol hypersecretion, of which 9 were found to have subclinical CS. Median serum cortisol was 2.0 microg/dL (range, 1.1-6.1) after 1-mg overnight dexamethasone suppression testing. Suspicious clinical findings on preoperative examination included skin bruising, unexplained weight gain, proximal muscle weakness, abnormal fat pads, skin thinning, fatigue, and facial plethora. During a median follow-up period of 5 months (range, 1-30 months), all 8 patients with easy bruising noted resolution postoperatively. Fatigue improved in 4 of 5 patients, muscle weakness in 6 of 8 patients, and weight in 7 of 9 patients, with a median body mass index change of -2.0 kg/m(2) (range, -7.1 to +0.5 kg/m(2)). CONCLUSION: Adrenalectomy improves clinical and metabolic parameters for many patients with subclinical CS.

Primary hyperaldosteronism: effect of adrenal vein sampling on surgical outcome.

HYPOTHESIS: Adrenal vein sampling is superior to computed tomography for subtype differentiation of primary hyperaldosteronism. DESIGN: Retrospective review. SETTING: University medical center. PATIENTS: Forty-eight patients (32 men and 16 women) with biochemically confirmed primary hyperaldosteronism. MAIN OUTCOME MEASURES: We compared demographic factors, results of biochemical and imaging studies (computed tomography and adrenal vein sampling), therapy, and patient outcomes. RESULTS: Mean +/- SEM adrenal nodule size was 1.54 +/- 0.2 cm. Adrenal vein sampling was performed in 41 (85%) of 48 patients, and it was successful in 39 (95%) of those 41 patients. Concordance between computed tomography and adrenal vein sampling was observed in 22 (54%) of the 41 patients. Thirty-two patients underwent successful laparoscopic adrenalectomy. There was 1 complication and no deaths. All 32 patients were cured of hypokalemia. CONCLUSION: Adrenal vein sampling is superior to image-based techniques for subtype differentiation of primary hyperaldosteronism.

Inframanubrial parathyroid glands in patients with primary hyperparathyroidism: alternatives to sternotomy.

Deep inframanubrial parathyroid tumors have traditionally been excised through a median sternotomy. With the advent of minimally invasive surgical access, we chose to examine the treatment options and outcomes of patients with inframanubrial mediastinal parathyroid tumors. Patients with primary hyperparathyroidism seen at a university medical center over a 12-year period were retrospectively reviewed. The utility of localization studies, methods of treatment, complications, and outcomes were examined in patients with a parathyroid tumor located in the mediastinum inferior to the manubrium. Patients with parathyroid adenomas located at the thoracic inlet were excluded. Sixteen patients with inframanubrial mediastinal tumors were treated during the study period. Altogether, 81% of the patients had undergone at least one prior neck exploration for primary hyperparathyroidism. Preoperative calcium and parathyroid hormone levels were 12.4 +/- 0.36 mg/dl and 273 +/- 70 pg/ml, respectively. Localization studies identified mediastinal parathyroid adenomas in the following locations: anterior mediastinum (n = 8), middle mediastinum (n = 7), posterior mediastinum (n = 1). Mediastinal computed tomography and technetium-sestamibi scans demonstrated the best sensitivity, 92% and 85%, respectively. Seven patients underwent successful excision of the mediastinal adenoma by transcervical mediastinal exploration with the Cooper retractor. The other patients underwent angiographic ablation (n = 4), anterior mediastinotomy (n = 3), video-assisted thoracoscopy (VATS) (n = 1), and VATS plus thoracotomy (n = 1). The mean hospital stay for the study group was 2.9 +/- 0.7 days. The complication rate was 25%. All patients were normocalcemic after a mean follow-up of 15 +/- 7 months. Most inframanubrial mediastinal parathyroid tumors can be successfully managed without median sternotomy.

Prevalence of malignancy within cytologically indeterminate thyroid nodules.

BACKGROUND: The optimal management of cytologically indeterminate thyroid nodules is controversial given the variable malignancy rates reported in this patient population. We examined the prevalence of malignancy within cytologically indeterminate follicular thyroid lesions in an attempt to predict malignancy based on cytologic features. METHODS: Cytopathology reports obtained after fine-needle aspiration biopsy (FNAB) examination of indeterminate follicular thyroid lesions were examined over a 4-year period. The prevalence of malignancy on final histology was determined in 4 indeterminate cytologic categories. RESULTS: A total of 107 records were available (91 women, 16 men). The mean patient age was 45.4 +/- 16 years. Forty-eight patients (45%) underwent surgery and had histopathologic diagnosis, while 57 patients did not have surgery. The prevalence of malignancy in patients who underwent thyroidectomy was 42% (20 of 48). CONCLUSIONS: The high prevalence of malignancy within indeterminate follicular lesions may necessitate thyroidectomy for patients with indeterminate follicular lesions on FNAB examination.

Directed parathyroidectomy: feasibility and performance in 100 consecutive patients with primary hyperparathyroidism.

HYPOTHESIS: Directed parathyroidectomy (DP) can be successfully completed in most patients with primary hyperparathyroidism. DESIGN AND SETTING: Retrospective review at a tertiary referral center. PATIENTS: One hundred consecutive patients with untreated, sporadic primary hyperparathyroidism operated on by a single surgeon from April 1, 1999, through December 31, 2001. INTERVENTIONS: Following preoperative imaging with sestamibi scintigraphy and ultrasonography, patients underwent parathyroidectomy with intraoperative parathyroid hormone monitoring using a focused approach through a limited neck incision (DP) or bilateral neck exploration (BNE) through a standard collar incision. MAIN OUTCOME MEASURES: Extent of exploration, operative time, length of stay, morbidity, and cure. RESULTS: Directed parathyroidectomy was completed in 70 patients and BNE in 30. Bilateral neck exploration was performed as the initial procedure in 13 patients and following intraoperative conversion from attempted DP in 17. Indications for predetermined BNE were failed preoperative localization (n = 8) and concomitant thyroid disease that required operative treatment (n = 5). The need for predetermined BNE decreased as preoperative localization improved. Intraoperative factors that necessitated conversion to BNE included persistently elevated intraoperative parathyroid hormone levels that accurately predicted multiglandular disease (n = 6), incorrect localization (n = 5), and inadequate exposure (n = 6). Operative time and length of stay were less for DP compared with BNE patients (66 vs 165 minutes and 0.5 vs 1.6 days, respectively). One patient had a temporary vocal cord paresis. All patients were eucalcemic in follow-up (4 months to 3 years). CONCLUSIONS: With accurate preoperative localization and intraoperative parathyroid hormone monitoring, DP can be successfully completed in most patients with sporadic primary hyperparathyroidism. Patients benefit from DP, which reduces operative time and length of stay and facilitates rapid convalescence.