Sleeve gastrectomy and Roux-en-Y gastric bypass exhibit differential effects on food preferences, nutrient absorption and energy expenditure in obese rats.

OBJECTIVE: All available treatments directed towards obesity and obesity-related complications are associated with suboptimal effectiveness/invasiveness ratios. Pharmacological, behavioral and lifestyle modification treatments are the least invasive, but also the least effective options, leading to modest weight loss that is difficult to maintain long-term. Gastrointestinal weight loss surgery (GIWLS) is the most effective, leading to >60-70% of excess body weight loss, but also the most invasive treatment available. Sleeve gastrectomy (SGx) and Roux-en-Y gastric bypass (RYGB) are the two most commonly performed GIWLS procedures. The fundamental anatomic difference between SGx and RYGB is that in the former procedure, only the anatomy of the stomach is altered, without surgical reconfiguration of the intestine. Therefore, comparing these two operations provides a unique opportunity to study the ways that different parts of the gastrointestinal (GI) tract contribute to the regulation of physiological processes, such as the regulation of body weight, food intake and metabolism. DESIGN: To explore the physiologic mechanisms of the two procedures, we used rodent models of SGx and RYGB to study the effects of these procedures on body weight, food intake and metabolic function. RESULTS: Both SGx and RYGB induced a significant weight loss that was sustained over the entire study period. SGx-induced weight loss was slightly lower compared with that observed after RYGB. SGx-induced weight loss primarily resulted from a substantial decrease in food intake and a small increase in locomotor activity. In contrast, rats that underwent RYGB exhibited a substantial increase in non-activity-related (resting) energy expenditure and a modest decrease in nutrient absorption. Additionally, while SGx-treated animals retained their preoperative food preferences, RYGB-treated rats experienced a significant alteration in their food preferences. CONCLUSIONS: These results indicate a fundamental difference in the mechanisms of weight loss between SGx and RYGB, suggesting that the manipulation of different parts of the GI tract may lead to different physiologic effects. Understanding the differences in the physiologic mechanisms of action of these effective treatment options could help us develop less invasive new treatments against obesity and obesity-related complications.

Changes in serum ghrelin predict weight loss after Roux-en-Y gastric bypass in rats.

BACKGROUND: Although Roux-en-Y gastric bypass (RYGB) is an effective and widely used therapy for severe obesity, the mechanisms by which it induces weight loss are not well understood. Several studies have shown that RYGB in human patients causes a decrease in circulating levels of ghrelin, a gastric hormone that strongly stimulates food intake. Substantial variation in the effect of RYGB on serum ghrelin has been reported in different studies and among individual patients, suggesting that regulation of this hormone is complex and subject to genetic and other patient-specific factors. To control for these factors and to enable more detailed study of physiologic mechanisms, we have recently developed a clinically relevant rat model of RYGB. In this study, we used this model to examine the effect of RYGB on serum ghrelin levels. METHODS: Fifteen Sprague-Dawley rats that had received a high-fat diet to induce moderate obesity underwent RYGB. The operation closely resembled the procedure in humans. Serum samples were collected 1 month before and 3 months after RYGB, and serum ghrelin levels were measured. The primary outcomes of the study were the changes in body weight, food intake, and circulating ghrelin levels after RYGB. A multiple linear regression model was developed to examine the relationship between ghrelin levels and weight change after RYGB. RESULTS: Three months after the procedure, RYGB-treated rats weighed 20 +/- 5% less than they would have, had they not undergone the procedure. Despite the weight loss, serum ghrelin levels were 38 +/- 6% lower than before surgery. There was appreciable variation in the weight loss in individual animals, and preoperative weight and pre- and postoperative ghrelin levels were the best predictors of postoperative weight loss. Thus, the animals who had the greatest weight loss were those that were heaviest before surgery. These rats had the highest preoperative and lowest postoperative ghrelin levels. CONCLUSIONS: Using our recently developed rat model of RYGB, we found that postoperative weight loss is correlated with the magnitude of the decrease in circulating ghrelin levels. This correlation provides the strongest evidence to date that altered ghrelin signaling contributes to weight loss after this operation. The lower level of circulating ghrelin after RYGB likely blunts the appetitive drive, leading to decreased food intake in these animals.

Simulated laparoscopy using a head-mounted display vs traditional video monitor: an assessment of performance and muscle fatigue.

BACKGROUND: The direction of visual gaze may be an important ergonomic factor that affects operative performance. We designed a study to determine whether a head-mounted display (HMD) worn by the surgeon would improve task performance and/or reduce muscle fatigue during a laparoscopic task when compared to the use of a traditional video monitor display (VMD). METHODS: Surgical residents (n = 30) were enrolled in the study. A junior group, consisting of 15 postgraduate year (PGY) = 1 subjects with no previous laparoscopic experience, and a senior group, consisting of 15 PGY 4 and PGY 5 subjects with experience, completed a laparoscopic task that was repeated four times using the Computer Enhanced Laparoscopic Training System (CELTS). Groups alternated between using the HMD with the task placed in a downward frontal position and the VMD with the task at a 30 degrees lateral angle. The CELTS module assessed task completion time, depth perception, path length of instruments, response orientation, motion smoothness; the system then generated an overall score. Electromyography (EMG) was used to record sternocleidomastoid muscle activity. Display preference was surveyed. RESULTS: The senior residents performed better than the junior residents overall on all parameters (p < 0.05) except for motion smoothness, where there was no difference. In both groups, the HMD significantly improved motion smoothness when compared to the VMD (p < 0.05). All other parameters were equal. There was less muscle fatigue when using the VMD (p < 0.05). We found that 66% of the junior residents but only 20% of the senior residents preferred the HMD. CONCLUSIONS: The CELTS module demonstrated evidence of construct validity by differentiating the performances of junior and senior residents. By aligning the surgeon's visual gaze with the instruments, HMD improved smoothness of motion. Experienced residents preferred the traditional monitor display. Although the VMD produced less muscle fatigue, inexperienced residents preferred the HMD, possibly because of improved smoothness of motion.

How accurate is computed tomography in predicting the real size of adrenal tumors? A retrospective study.

BACKGROUND: The ability to accurately assess tumor size is an important consideration during the preoperative evaluation of adrenal tumors, particularly solid nonfunctioning masses (incidentalomas or adrenalomas). Does the histological size of the adrenal tumor correspond to the preoperative computed tomography (CT)-estimated size? OBJECTIVE: To evaluate the accuracy of CT in predicting the real size of adrenal tumors. DESIGN: Retrospective review of all clinical records of patients who underwent adrenalectomy from 1984 through 1995. The mean tumor size reported from CT examinations was compared with the corresponding size obtained from the pathology reports and the statistical difference was evaluated. SETTING: University and private hospitals in Athens, Greece. PATIENTS: Seventy-six patients who underwent adrenalectomy for various adrenal diseases and who met strict entry criteria. RESULTS: For the entire population, the mean diameter of the tumors was estimated (CT reports) at 4.64 cm, but the real value (pathology reports) was 5.96 cm (P < .001). The underestimation held true for all of the studied subgroups that were defined by the different proposed cutoffs for malignancy. Three patients were incidentally found to have adrenal cancer, with the tumors measuring from 2.6 to 2.9 cm on CT. In addition, 4 pheochromocytomas were clinically and laboratory "silent" at the time of their discovery. The regression line (y = 0.85 + 1.09x) relating CT-estimated and histological tumor size was linear (r = 0.90, P < .001). CONCLUSIONS: Computed tomography underestimates the real size of adrenal tumors. The CT-estimated value should be corrected accordingly to obtain the real size. The size of an adrenal tumor, even when corrected, cannot predict the tumor's clinical behavior in many cases. Surgeons should always cautiously interpret the proposed diagnostic cutoffs, especially when considering surgical or conservative management of small nonfunctioning adrenal tumors.

Anterior, posterior, or laparoscopic approach for the management of adrenal diseases?

BACKGROUND: At the advent of laparoscopic adrenalectomy it seemed timely to us to assess the advantages and the overall results of the different techniques that are currently used in an approach to adrenalectomy. PATIENTS AND METHODS: Between 1984 and 1995, 165 patients underwent adrenalectomy. Eighty-six patients (37 men and 49 women with a mean age of 46.4 years) underwent adrenalectomy via the anterior approach, 61 patients (18 men and 43 women with a mean age of 43.8 years) underwent posterior extraperitoneal adrenalectomy, and 18 patients (8 men and 10 women with a mean age of 48.7 years) underwent anterior laparoscopic adrenalectomy. For statistical analysis of the different comparisons between the groups we used the t test for independent samples, the Wilcoxon test, chi-square, and one way analysis of variance. RESULTS: There was no operative mortality. The morbidity was 13.9% in the anterior approach, 9.8% in the posterior approach, and 0% in the laparoscopic approach. The mean operating time for unilateral adrenalectomy was 155.3 min (range 75 to 315) for the anterior approach, 108.6 min (range 60 to 195) for the posterior approach and 116.1 min (range 75 to 180) for the laparoscopic approach. For bilateral adrenalectomy the mean operating time was 165 min for the anterior and 178 min for the posterior approach. The average diameter of tumors resected anteriorly was 8.07 cm (range 2.5 to 20), posteriorly was 5.25 cm (range 0.5 to 14), and laparoscopically was 4.03 cm (range 2 to 6.5). The mean length of postoperative hospitalization for patients undergoing unilateral adrenalectomy was 8 days (range 2 to 25) for the anterior approach, 4.5 days (range 1 to 11) for the posterior approach, and 2.2 days (range 1 to 5) for the laparoscopic approach. Patient controlled analgesia lasted 3.4 days for those operated anteriorly, 2.3 days for those operated posteriorly, and 1.08 days for those that underwent laparoscopic adrenalectomy. CONCLUSIONS: The laparoscopic approach to the adrenal promises the safest and least painful operation with shorter in-hospital stay and the best cosmetic and long-term results. The posterior approach is the fastest of all and a better overall operation than the anterior approach that should only be reserved for removing very large adrenal tumors and when concomitant intra-abdominal procedures, that can't be handled laparoscopically, are anticipated.

Histologic characteristics of laparoscopic saline-enhanced electrosurgery of liver and splenic injuries.

BACKGROUND: Hemostasis is crucial during laparoscopic surgery. Unlike conventional electrosurgery, saline-enhanced electrosurgery (SEE) improves the electrode-to-tissue interface. This study investigated SEE as a means of achieving hemostasis in liver and splenic injuries and assessed the associated histologic changes. METHODS: Nine anesthetized pigs underwent laparoscopic liver tip and splenic wedge amputations. Injuries were treated with SEE (25-35 and 35-45 W, respectively). Animals were sacrificed postprocedure and at 1 and 4 weeks. Depth of necrosis was analyzed using a mixed model analysis of variance. RESULTS: Liver mean depth of necrosis was 5.3 mm (acute), 6.0 mm (1 week), and 5.3 mm (4 weeks) ( p = not significant). Splenic mean depth of necrosis was 7.0 mm (acute), 7.0 mm (1 week), and 2.7 mm (4 weeks). ( p < 0.01) Acute injuries demonstrated thermal coagulation necrosis that healed with well-defined bands of collagen at 1 and 4 weeks. CONCLUSIONS: SEE provides effective hemostasis and results in an acceptable depth of necrosis with satisfactory wound healing in a porcine model of solid organ injury.

A cost--utility analysis of treatment options for inguinal hernia in 1,513,008 adult patients.

BACKGROUND: The controversial issue of the cost-effectiveness of laparoscopic inguinal hernia repair is examined, employing a decision analytic method. MATERIALS AND METHODS: The NSAS, NHDS (National Center for Health Statistics), HCUP-NIS (Agency for Healthcare Research and Quality) databases and 51 randomized controlled trials were analyzed. The study group constituted of a total of 1,513,008 hernia repairs. Projection of the clinical, economic, and quality-of-life outcomes expected from the different treatment options was done by using a Markov Monte Carlo decision model. Two logistic regression models were used to predict the probability of hospital admission after an ambulatory procedure and the probability of death after inguinal hernia repair. Four treatment strategies were modeled: (1) laparoscopic repair (LR), (2) open mesh (OM), (3) open non-mesh (ONM), and (4) expectant management. Costs were expressed in US dollars and effectiveness in quality-adjusted life years (QALYs). The main outcome measures were the average and the incremental cost-effectiveness (ICER) ratios. RESULTS: Compared to the expectant management, the incremental cost per QALY gained was 605 dollars (4086 dollars, 9.04 QALYs) for LR, 697 dollars (4290 dollars, 8.975 QALYs) for OM, and 1711 dollars (6200 dollars, 8.546 QALYs) for ONM. In sensitivity analysis the two major components that affect the cost-effectiveness ratio of the different types of repair were the ambulatory facility cost and the recurrence rate. At a LR ambulatory facility cost of 5526 dollars the ICER of LR compared to OM surpasses the threshold of 50,000 dollars/QALY. CONCLUSIONS: On the basis of our assumptions this mathematical model shows that from a societal perspective laparoscopic approach can be a cost-effective treatment option for inguinal hernia repair.

Computer-enhanced laparoscopic training system (CELTS): bridging the gap.

BACKGROUND: There is a large and growing gap between the need for better surgical training methodologies and the systems currently available for such training. In an effort to bridge this gap and overcome the disadvantages of the training simulators now in use, we developed the Computer-Enhanced Laparoscopic Training System (CELTS). METHODS: CELTS is a computer-based system capable of tracking the motion of laparoscopic instruments and providing feedback about performance in real time. CELTS consists of a mechanical interface, a customizable set of tasks, and an Internet-based software interface. The special cognitive and psychomotor skills a laparoscopic surgeon should master were explicitly defined and transformed into quantitative metrics based on kinematics analysis theory. A single global standardized and task-independent scoring system utilizing a z-score statistic was developed. Validation exercises were performed. RESULTS: The scoring system clearly revealed a gap between experts and trainees, irrespective of the task performed; none of the trainees obtained a score above the threshold that distinguishes the two groups. Moreover, CELTS provided educational feedback by identifying the key factors that contributed to the overall score. Among the defined metrics, depth perception, smoothness of motion, instrument orientation, and the outcome of the task are major indicators of performance and key parameters that distinguish experts from trainees. Time and path length alone, which are the most commonly used metrics in currently available systems, are not considered good indicators of performance. CONCLUSION: CELTS is a novel and standardized skills trainer that combines the advantages of computer simulation with the features of the traditional and popular training boxes. CELTS can easily be used with a wide array of tasks and ensures comparability across different training conditions. This report further shows that a set of appropriate and clinically relevant performance metrics can be defined and a standardized scoring system can be designed.

Oncocytic differentiation in salivary gland tumours.

An oncocytic mucoepidermoid carcinoma and an oncocytic pleomorphic adenoma occurred in a 47-year-old male and a 75-year-old female, respectively. Both presented as asymptomatic parotid gland masses without evidence of facial nerve paralysis and were treated by superficial parotidectomy. There has been no evidence of recurrence or metastasis. Oncocytic change is rare in major salivary gland mucoepidermoid carcinoma with only two previously reported cases. Marked oncocytic transformation of pleomorphic adenomas can cause their confusion with oncocytomas. Recognition of oncocytic differentiation in various salivary gland tumours is important to avoid misclassification of these lesions.

Measurement of in-vivo force response of intra-abdominal soft tissues for surgical simulation.

The lack of data on in-vivo material properties of soft tissues has been a significant impediment in the development of virtual reality based surgical simulators that can provide the user with realistic visual and haptic feedback. As a first step towards characterizing the mechanical behavior of organs, this work presents in-vivo force response of the liver and lower esophagus of pigs when subjected to ramp and hold, and sinusoidal indentations delivered using a haptic feedback device, Phantom, employed as a mechanical stimulator. The results show that pulse significantly affects the reaction forces and that the lower esophagus is 2 to 2.5 times stiffer than the liver.

Adrenaloma: a call for more aggressive management.

We review our experience from the surgical management of 57 patients (24 males, 33 females) with a mean age of 48.5 years who underwent adrenalectomy because of the computed tomography (CT) finding of a "nonfunctioning" adrenal tumor (adrenaloma). We found that CT consistently underestimated the real histologic size of the adrenal tumor (p = 0.001). Of the 57 resected tumors, 23 were cortical adenomas, 7 myelolipomas, 8 adrenal cysts, 11 nodular hyperplasias, 2 primary adenocarcinomas, 2 metastatic carcinomas, and 4 pheochromocytomas. The mean diameter was 5.89 cm and the mean weight 114.07 g. The mean diameter of the resected primary adenocarcinomas was 3.0 cm and 4.5 cm, respectively. The operative mortality was zero and the perioperative morbidity minimal. The mean operating time was 137 minutes (range 60-240 minutes). The posterior approach had the shortest operating time and the laparoscopic approach the shortest hospital stay and the least postoperative need for narcotics. During the 6.2 years mean follow-up period, five patients with preoperative hypertension remained normotensive, and both patients with the resected primary adenocarcinomas are alive without recurrence. We suggest a more liberal surgical approach to patients with adrenalomas because: (1) even small tumors can be malignant or potentially lethal (e.g., pheochromocytomas); (2) some tumors that appear to be nonfunctioning may in reality be functioning; and (3) other nonfunctioning tumors may, with time (and without prior notice), function. The low risk of adrenalectomy especially via the laparoscopic approach can provide an early definitive diagnosis and treatment, avoiding the cost of repeated CT scans and other studies as suggested by the currently prevailing conservative management of these tumors.