Metabolic syndrome after a liver transplantation in an Asian population.

BACKGROUND: With improvements in patient survival after a liver transplantation (LT), long-term sequelae such as metabolic syndrome (MS) have become increasingly common. This study aims to characterize the prevalence, associations and long-term outcomes of post-LTMS and its components in an Asian population. METHODS: A retrospective review of all adult patients who underwent LT at the National University Health System Singapore between December 1996 and May 2012 was performed. MS was defined using the Adult Treatment Panel (ATP) III criteria modified for an Asian population. RESULTS: The median age of this cohort of 90 patients was 50.0 (16.0-67.0) years, with a median follow-up duration of 60.0 (7.0-192.0) months. The prevalence of post-LTMS was 35.6%, diabetes mellitus (DM) 51.1%, hypertension 60.0%, obesity 26.7% and dyslipidaemia 46.7%. On univariate analysis, factors significantly associated with post-LT MS include female gender (P = 0.066), pre-LT respiratory comorbidities (P = 0.038), pre-LT obesity (P = 0.014), pre-LTDM (P < 0.001), pre-LT hypertension (P = 0.039), pre-LTMS (P < 0.001), prednisolone use ≥24 months (P = 0.005) and mycophenolate mofetil use ≥24 months (P = 0.035). On multivariate analysis, independent associations of post-LT MS were pre-LTDM (P = 0.011) and pre-LTMS (P = 0.024). There was no difference in long-term survival of patients with and without post-LTMS (P = 0.425). CONCLUSION: In conclusion, pre-LT components of the MS and the use of certain immunosuppressants are related to developing post-LTMS.

Outcomes of resection of giant hepatocellular carcinoma in a tertiary institution: does size matter?

BACKGROUND: The surgical management of giant hepatocellular carcinoma (G-HCC), or HCC of ≥10 cm in diameter, remains controversial. The aim of this study was to compare the outcomes of surgical resection of, respectively, G-HCC and small HCC (S-HCC), or HCC measuring <10 cm. METHODS: A retrospective review of all patients (n = 86) diagnosed with HCC and submitted to resection in a tertiary hospital during the period from January 2007 to June 2012 was conducted. Overall survival (OS), recurrence rates and perioperative mortality at 30 days were compared between patients with, respectively, G-HCC and S-HCC. Prognostic factors for OS were analysed. RESULTS: The sample included 23 patients with G-HCC (26.7%) and 63 with S-HCC (73.3%) based on histological tumour size. Patient demographics and comorbidities were comparable. Median OS was 39.0 months in patients with G-HCC and 65.0 months in patients with S-HCC (P = 0.213). Although size did not affect OS in this cohort, the presence of satellite lesions [hazard ratio (HR) 3.70, P = 0.012] and perioperative blood transfusion (HR 2.85, P = 0.015) were negative predictors for OS. CONCLUSIONS: Surgical resection of G-HCC provides OS comparable with that after resection of S-HCC.

Laparoscopic cholecystectomy for acute cholecystitis: safe implementation of successful strategies to reduce conversion rates.

INTRODUCTION: A higher rate of conversion to open surgery is a well-known problem in patients with acute cholecystitis undergoing laparoscopic cholecystectomy. The aim of this study is to analyze factors which may impact on conversion rates, and to analyze our outcomes following implementation of a departmental strategy in reducing conversion rates. MATERIALS AND METHODS: 122 patients with acute cholecystitis were considered for laparoscopic cholecystectomy from July 2003 to July 2007. An audit of the results of laparoscopic cholecystectomy was done in July 2005 and a departmental strategy aimed at reducing the conversion rates was introduced. The strategies included early laparoscopic cholecystectomy (within 72 hours of admission), performed or supervised by specialist hepatobiliary surgeons, and modifications of operative techniques. This study compares the conversion rates before and after that audit. Forty-eight patients (group A) were from the preaudit period and the remaining 74 (group B) were from the postaudit period. A multivariate analysis was performed to identify risk factors for conversion to open surgery and whether the strategies implemented resulted in decrease in conversion rates. RESULTS: In the group A patients, there was a conversion rate of 29.2%. Gallbladder wall thickness of greater than 5 mm was found to be a statistically significant (p = 0.028) risk factor for conversion to open surgery. In group B patients, the conversion rates were significantly lower at 6.75% (p = 0.001). Analyzing both groups of patients, using multivariate analysis, gallbladder wall thickness, increasing age, and preaudit operative period were found to be independently associated with conversion to open surgery. CONCLUSIONS: This study demonstrated that, with specific strategies to decrease conversion and with technical improvements, the conversion rates can be decreased with no demonstrable difference in postoperative complications. Gallbladder wall thickness and increasing age are risk factors for conversion to open surgery.

Fast segmentation and modeling of hepatic components for the planning of robot-assisted liver tumor ablation.

Segmentation and modeling of hepatic components from pre-operative images is very important for treatment planning and guidance in robot-assisted liver tumor ablation. An in-house developed system for hepatic component segmentation and modeling using CT data is presented in this paper. This system includes gross liver segmentation by a 3D mesh deformation model, liver vasculature segmentation by a vessel context-based voting and grouping method, liver tumor segmentation by a support vector machine framework, and other segmentation/modeling tool. This system was tested using 20 data sets from human patients and 5 sets of porcine CT scan. It is suggested by experimental results that the developed system is able to conduct fast segmentation and modeling of hepatic components for both human and large animal, with a satisfying accuracy, to support treatment planning.

Changes in mechanical, structural integrity and microbiological properties following cryopreservation of human cadaveric iliac arteries.

INTRODUCTION: The study seeks to investigate how the duration of storage of cryopreserved human cadaveric iliac arteries impacts their mechanical, structural and microbiological properties as compared to their fresh sample. MATERIALS AND METHODS: Iliac arteries were harvested from 12 human cadavers and divided into 2 groups. One group underwent mechanical stress-strain assessment immediately and another was cryopreserved for a pre-determined time-period (range, 29 to 364 days). Mechanical functionality was assessed with a customised clamping mechanism. The arteries' microbiological properties were studied pre- and post-cryopreservation. The post-thawed arteries were also assessed histologically for structural integrity. RESULTS: Of the 12 pairs, only 7 (58, 119, 150, 252, 300, 332 and 364 days) iliac arteries were included in the final analysis. The other 5 pairs (29, 90, 188, 205 and 270 days) had abundant local calcification and their stress-strain curves could not be characterised. From the curves, pre- and post-cryopreserved arteries had the most similar mechanical properties when stored for 119 days. A trend of increasing relative stiffness with increased duration of storage was noted. The post-thawed arteries demonstrated minimal fragmentation except in atherosclerotic areas. Majority of the arteries were not contaminated by bacterial or fungal infection pre- and post-cryopreservation. Also, 2 arteries (364 and 332 days) which had initial bacterial colonisation showed no bacterial growth on their post-thawed sample. CONCLUSION: Mechanically, non-atherosclerotic cryopreserved arteries can be a good substitute to their corresponding fresh arterial graft. However, the length of cryopreservation has an effect on the relative stiffness of the pre- and post-cryopreserved arteries. Histological and microbiological findings suggest that cryopreservation have little impact on an artery structural integrity and may possibly have a role in maintaining sterility and sterilising the arteries.

Robotic learning of motion using demonstrations and statistical models for surgical simulation.

PURPOSE: In robotic-assisted surgical training, the expertise of surgeons in maneuvering surgical instruments may be utilized to provide the motion trajectories for teaching. However, the motion primitives for trajectory planning are not known until the motion trajectory is generalized. We hypothesize that a generic model that encodes surgical skills using demonstrations and statistical models can be used by the surgical training robot to determine the motion primitive base on the motion trajectory. METHODS: The generic model was developed from twenty-two sets of motion trajectories of soft tissue division with laparoscopic scissors collected from a robotic laparoscopic surgical training system. Adaptive mean shift method with initial bandwidth determined by the plug-in-rule method was used to identify the primitives in the motion trajectories. Gaussian Mixture Model was applied to model the underlying motion structure. Gaussian Mixture Regression was then applied to reconstruct a generic motion trajectory for the task. RESULTS: The generic model and proposed method were investigated in experiments. Motion trajectory of tissue division was model and reconstructed. The motion model which was trained based on primitives determined by adaptive mean shift method produced RMS error of 3.05° and 3.08° with respect to the demonstrated trajectories of left and right instruments, respectively. The RMS error was smaller than that of k-means method and fixed bandwidth mean shift method. The dexterous features in the demonstrations were also preserved. CONCLUSIONS: Surgical tasks can be modeled using Gaussian Mixture Model and motion primitives identified by adaptive mean shift method with minimum user intervention. Generic motion trajectory has been successfully reconstructed based on the motion model. Investigation on the effectiveness of this method and generic model for surgical training is ongoing.

Longitudinal in-vivo volumetry study for porcine liver regeneration from CT data.

The use of hepatic-like cloned cord lining epithelial cells (CLEC) to enhance liver regeneration has been proposed, but has not been properly investigated in a large animal study. The paper presents a system developed for the longitudinal in-vivo volumetry study on porcine liver regeneration from computed tomography (CT) data. In this system, a rough 3D liver volume is firstly automatically segmented by a 3D mesh deformation-based method. Then a refinement step to eliminate the segmentation error is carried out by a 3D post-editing tool, followed by mesh-volume conversion and volume calculation. This system was applied in a pilot study, which was composed of 4/4 pigs in the Experimental/Control Groups, to measure liver volumes over pre- to post-operative time course. Experimental results suggest that (1) the developed system can perform CT-based porcine liver volumetry efficiently, and (2) the infusion of CLEC to liver remnant may potentially enhance the liver regeneration.

Influence of dynamic shadowing on 2D and 3D laparoscopic visualization under visible light and infrared light.

BACKGROUND: Depth perception is a significant weakness in conventional two-dimensional (2D) endoscopy. We hypothesize that dynamic shadowing improves endoscopic depth perception during laparoscopy. Two experiments were performed to investigate this hypothesis. The first experiment compared the effect of dynamic shadowing with 2D and three-dimensional (3D) displays. The second experiment compared the effect of dynamic shadowing under visible light and infrared light. MATERIALS AND METHODS: In the experiment, a box trainer was designed and built to house three laparoscopic tasks. Six settings were investigated: 2D display without dynamic shadows under visible light, 2D display with dynamic shadows under visible light, 3D display without dynamic shadows under visible light, 3D display with dynamic shadows under visible light, 2D display without dynamic shadows under infrared light, and 2D display with dynamic shadows under infrared light. Two types of illumination were used: static overhead illumination and dynamic grasper illumination. The execution time and number of errors committed by the volunteers with no formal laparoscopic experience were measured in the experiments. RESULTS: The experimental results showed that dynamic shadowing with 2D display under both visible light and infrared light reduced mean execution time. Dynamic shadowing with 3D display increased execution time for one of the tasks and increased the number of errors for all three tasks. CONCLUSIONS: Dynamic shadowing has the potential to be an inexpensive method to improve laparoscopic depth perception. However, subjects needed to pay special attention to the shadows, which suggests that better implementation is necessary to improve the dominance of shadows as an effective depth cue.

Single-port laparoscopic spleen preserving distal pancreatectomy.

Single-port laparoscopic surgery has become increasingly popular, with widened indication to more types of surgery. This report will present our initial experience with spleen-preserving distal pancreatectomy technique through a small transumbilical incision using the single-port approach for a cystic tumor of pancreatic body. The surgery was done using specialized single-port instruments and normal laparoscopic instruments. The total operative time for this surgery is 233 minutes, and it was completed without drains. Patient was discharged from the hospital on the third day postoperatively in good condition.

Quasi-linear viscoelastic modeling of arterial wall for surgical simulation.

PURPOSE: Realistic soft tissue deformation modeling and haptic rendering for surgical simulation require accurate knowledge of tissue material characteristics. Biomechanical experiments on porcine tissue were performed, and a reduced quasi-linear viscoelastic model was developed to describe the strain-dependent relaxation behavior of the arterial wall. This information is used in surgical simulation to provide a realistic sensation of reduction in strength when the user holds a virtual blood vessel strained at different levels. MATERIALS AND METHODS: Twelve pieces of porcine abdominal artery were tested with uniaxial elongation and relaxation test in both circumferential and longitudinal directions. The mechanical property testing system consists of automated environment control, testing, and data collection mechanism. A combined logarithm and polynomial strain energy equation was applied to model the elastic response of the specimens. The reduced relaxation function was modified by integrating a rational equation as a corrective factor to precisely describe the strain-dependent relaxation effects. RESULTS: The experiments revealed that (1) stress is insensitive to strain rate in arterial tissue when the loading rate is low, and (2) the rate of stress relaxation of arterial wall is highly strain dependent. The proposed model can accurately represent the experimental data. Stress-strain function derived from the combined strain energy function is able to fit the tensile experimental data with R(2) equals to 0.9995 in circumferential direction and 0.999 in longitudinal direction. Modified reduced relaxation function is able to model the strain-dependent relaxation with R(2) equals to 0.9686 in circumferential direction and 0.988 in longitudinal direction. CONCLUSION: The proposed model, based on extensive biomechanical experiments, can be used for accurate simulation of arterial deformation and haptic rendering in surgical simulation. The resultant model enables stress relaxation status to be determined when subjected to different strain levels.

Designing an active motor skill learning platform with a robot-assisted laparoscopic trainer.

Laparoscopic Surgery poses significant complexity in hand-eye coordination to the surgeon. In order to improve their proficiency beyond the limited exposure in the operating theatre, surgeons need to practice on laparoscopic trainers. We have constructed a robotic laparoscopic trainer with identical degrees of freedom and range of motion as a conventional laparoscopic instrument. We hypothesize that active robotic assistance through a laparoscopic trainer improves training efficacy as compared to autonomous practice. In order to test the hypothesis, we have divided the subjects into two groups. The control group practiced on two laparoscopic tasks manually without feedback or supervision. The other group practiced on the same tasks with robotic assistance. Results from the robot-assisted group show that tool orientation (pitch and yaw joint motion) in the pointing task improved by more than 15%.

Minimally invasive retroperitoneal pancreatic necrosectomy in the management of infected pancreatitis.

INTRODUCTION: Surgical debridement is the mainstay in the management of infected pancreatic necrosis. Minimally invasive techniques have been shown to minimize surgical insult. We aim to review our recent experience with minimally invasive retroperitoneal pancreatic necrosectomy (MIRP). METHODS: The medical records of consecutive patients between October 2007 and April 2008 who underwent MIRP at our hospital were reviewed. All the patients had a preoperative computed tomography-guided aspiration and positive bacteriologic culture of the peripancreatic collection. RESULTS: Five patients underwent MIRP during the 8-month period. Fourteen procedures were carried out, with a median of 3 (range, 1 to 5) procedures per patient. Only 1 patient required postoperative intensive care monitoring. One patient had a left renal contusion that resolved, and 2 patients developed pancreatic fistula owing to pancreatic duct disruption requiring stenting of the pancreatic duct. There were no mortalities. CONCLUSION: MIRP is a good alternative technique in the management of selected patients with infected peripancreatic necrosis.