Michael A.J. Moser

OVERVIEW OF UPCOMING ADVANCES IN COLONOSCOPY

Although colonoscopy is a very commonly carried out procedure, it is not without its problems, including a risk of perforation and significant patient discomfort, especially associated with looping formation. Furthermore, looping formation may prevent a complete colonoscopy from being carried out in certain patients. The conventional colonoscope has not changed very much since its original introduction. We review promising technologies that are being promoted as a way to address the problems with current colonoscopy. There are some methods to prevent looping formation, including overtube, variable stiffness, computer‐guided scopes, Aer‐O‐Scope™, magnetic endoscopic imaging and the capsule endoscope. In recent years, with the progress of microelectromechanical and microelectronic technologies, many biomedical and robotic researchers are developing autonomous endoscopes with miniaturization of size and integration functionality that represent state of the art of the micro‐robotic endoscope. The initial results by using aforementioned methods seem promising; however, there are some conflicting reports of clinical trials with the overtube colonoscope, the computer‐guided scope and the variable stiffness colonoscope. There are also some limitations in the use of the Aer‐o‐scope and the capsule endoscope. The autonomous endoscope is based on a self‐propelling property that is able to avoid looping completely. This novel technology could potentially become the next generation endoscope; however, there are still critical techniques to be approached in order to develop the effective and efficient novel endoscope.

Radiofrequency ablation technique in the treatment of liver tumours: review and future issues

Abstract Thermal ablation is increasingly being used for treatment of liver tumours. Among the techniques of thermal ablation, radiofrequency ablation (RF) is undoubtedly being used most frequently because of its advantages, such as morbidity and mortality rates, effective tumour ablation, as well as being less time-consuming. This paper presents the state of the art of RF ablation technique. This includes the theoretical development, experimental study and clinical application of the radiofrequency ablation technique. First, it introduces the principle of this technique. Second, it shows the development of this technique and valuable achievements. These achievements include the device, strategy of operation and extension to other diseases. Third, it concludes future issues to be addressed in order to further advance this technique.

How useful are bowel sounds in assessing the abdomen

Background: The purpose of our study is to determine the accuracy of bowel sounds in the diagnosis of ileus and bowel obstruction. Methods: Healthy volunteers (n = 10) and patients with radiologically or laparotomy confirmed small bowel obstruction (n = 9) and ileus (n = 7) were enrolled. Two 30-second recordings from each subject were obtained using an electronic stethoscope. Study physicians (n = 20) were then presented with 43 recordings in blinded fashion and were asked whether each was from a normal subject or from a subject with bowel obstruction or ileus. Results: Physicians arrived at the correct diagnosis a median of 30 times out of 43 (69.8%). Intra-observer variation (ĸ = 0.72, agreement 81.3%) and intra-subject variation (ĸ = 0.63, agreement 78.7%) were very good. Bowel sounds from subjects with ileus and normal bowel sounds were correctly identified most of the time (84.5 and 78.1%, respectively). Bowel sounds from patients with obstruction were correctly identified only 42.1% of the time, but if a physician believed he or she was hearing a bowel obstruction, this had a strong positive predictive value (PPV, 72.7%). Conclusion: Our results suggest that the auscultation of bowel sounds is useful, especially in detecting ileus. The diagnosis of obstruction had a high PPV.

Study of the relationship between the target tissue necrosis volume and the target tissue size in liver tumours using two-compartment finite element RFA modelling

Abstract Purpose: The aim of this study was to investigate the relationship between the target tissue necrosis volume and the target tissue size during the radiofrequency ablation (RFA) procedure. Materials and methods: The target tissues with four different sizes (dxy = 20, 25, 30 and 35 mm) were modelled using a two-compartment radiofrequency ablation model. Different voltages were applied to seek the maximum target tissue necrosis volume for each target tissue size. The first roll-off occurrence or the standard ablation time (12 min) was taken as the sign for the termination of the RFA procedure. Results: Four different maximum voltages without the roll-off occurrence were found for the four different sizes of target tissues (dxy = 20, 25, 30 and 35 mm), and they were 36.6, 35.4, 33.9 and 32.5 V, respectively. The target tissues with diameters of 20, 25 mm can be cleanly ablated at their own maximum voltages applied (MVA) but the same finding was not found for the 35-mm target tissue. For the target tissue with diameter of 30 mm, the 50 °C isothermal contour (IT50) result showed that the target tissue can be cleanly ablated, but the same result did not show in the Arrhenius damage model result. Furthermore, two optimal RFA protocols with a minimal thermal damage to the healthy tissues were found for the target tissues with diameters of 20 and 25 mm, respectively. Conclusions: The study suggests that target tissues of different sizes should be treated with different RFA protocols. The maximum target tissue volume was achieved with the MVA without the roll-off occurrence for each target tissue size when a constant RF power supply was used.

Emphysematous pancreatitis: a less aggressive form of infected pancreatic necrosis?

Objective: Emphysematous pancreatitis is characterized by the presence of intraparenchymal pancreatic air in the setting of necrotizing pancreatitis. Mortality and morbidity rates approach approximately 40% and 100%, respectively. Traditionally, emphysematous pancreatitis was an indication for surgical intervention. The purpose of this review was to discuss our experience with nonoperative management of emphysematous pancreatitis. Methods: Between July 2005 and August 2007, 5 patients with emphysematous pancreatitis were admitted to Royal University Hospital (Saskatoon, Saskatchewan, Canada). The cases are described in the context of the current literature. Results: The 5 male patients ranged in age from 50 to 77 years. Four required at least 1 week in the intensive care unit. All 5 cases of emphysematous pancreatitis went on to be treated successfully with nonoperative management. Furthermore, after a minimum of 1-year follow-up, they remain out of hospital and continue to do well. Conclusions: Our data suggest that emphysematous pancreatitis may be a favorable subtype of severe pancreatitis. In well-selected patients, nonoperative management with aggressive antibiotic treatment and nutritional support may suffice.

Numerical analysis of the relationship between the area of target tissue necrosis and the size of target tissue in liver tumours with pulsed radiofrequency ablation

Abstract Purpose: Radiofrequency ablation (RFA) is currently restricted to the treatment of target tissues with a small size (<3 cm in diameter). To overcome this problem with RFA, some phenomena need to be understood first. The study presented in this paper investigated the relationship between the area of target tissue necrosis (TTN) and the size of target tissue in pulsed radiofrequency ablation (PRFA). Materials and methods: Liver tumour, one of the common targets of RFA in clinical practice, was used as the target tissue in this study. Two types of pulsed RF power supply methods (half-square and half-sine) and three target tissues with different sizes (25 mm, 30 mm and 35 mm in diameter) were studied using finite element modelling. The finite element model (FEM) was validated by using an in vitro experiment with porcine liver tissue. The first roll-off occurrence or 720 s, whichever occurs first, was chosen as the ablation termination criterion in this study. Results: For each target tissue size, the largest TTN area was obtained using the maximum voltage applied (MVA) without roll-off occurrence. In this study, target tissues with a 25 mm diameter can be ablated cleanly but target tissues with 30-mm and 35-mm failed to be ablated. Conclusions: The half-square PRFA could achieve a larger TTN area than the half-sine PRFA. The MVA decreases with an increase in the target tissue diameter in both the half-square PRFA and the half-sine PRFA. The findings of this study are in agreement with the clinical results that lesions (≥3 cm in diameter) have less favourable results from RFA.

Analysis of and mathematical model insight into loop formation in colonoscopy

The colonoscope is an important tool in the diagnosis and management of diseases of the colon; yet its design has not changed appreciably since it was first introduced to clinical practice 40 years ago. One of the ongoing challenges with this device is that the natural shape of the colon predisposes to loop formation by the scope during the examination. The result of this looping is that further insertion of the scope results in a larger loop size without any advancement of the tip of the scope. Looping thus causes pain in the patient, risks perforation of the colon, and results in incomplete examinations. In this article, loop formation is analyzed in terms of frictional force state and Kirchhoff’s slender rod model in order to better understand the generic principle of loop formation. Next, a mathematical model of deformation of the colon with respect to external manipulation involving a number of variables involved in loop formation is constructed. Finally, a model of the motion of the scope relative to the colon when looping occurs is presented. The model has clinical significance for prediction of advancement of the tip of the scope when looping occurs. The mathematical model was then validated and verified using data available from the literature. Our models are an important starting point in the development of a novel device to overcome loop formation and result in increased patient comfort and an improved completion rate for colonoscopy procedures.

Intrapancreatic accessory spleen: A case report and review of the literature

We present the case of a 26 year old male who was found to have a mass in the tail of the pancreas on an ultrasound scan. The lesion was suspicious for a non-functioning pancreatic neuroendocrine tumour (PNET) and so he underwent distal pancreatectomy. Pathology revealed this to be an intrapancreatic accessory spleen (IPAS). This is a rare entity, and the literature on this subject is reviewed. A lesion in the pancreas that enhances in a manner similar to the spleen, whether the contrast is used in the setting of a Contrast Enhanced Ultrasound, a contrast enhanced CT scan, or a gadolinium enhanced MRI scan, is suggestive of IPAS. Nonetheless, the majority of these rare lesions are likely to be surgically excised rather than observed due to the similar appearance to PNET.

A review of radiofrequency ablation: Large target tissue necrosis and mathematical modelling.

Radiofrequency ablation (RFA) is an effective clinical method for tumour ablation with minimum intrusiveness. However, the use of RFA is mostly restricted to small tumours, especially those <3cm in diameter. This paper discusses the state-of-the-art of RFA, drawn from experimental and clinical results, for large tumours (i.e. ⩾3cm in diameter). In particular, the paper analyses clinical results related to target tissue necrosis (TTN) and mathematical modelling of the RFA procedure to understand the mechanism whereby the TTN is limited to under 3cm with RFA. This paper also discusses a strategy of controlling of the temperature of target tissue in the RFA procedure with the state-of-art device, which has the potential to increase the size of TTN. This paper ends with a discussion of some future ideas to solve the so-called 3-cm problem with RFA.

The prognostic value of time needed on dialysis in patients with delayed graft function

INTRODUCTION We hypothesize that in patients with delayed graft function (DGF), the need for a longer time needed on dialysis (TND) post-kidney transplant is associated with poorer long-term function and an increase in complications. METHODS This was a retrospective chart review involving collaboration between Western University (WU) Renal Transplant Program of London, Ontario and the Saskatchewan renal transplant program (SRTP). A total of 774 patients (567 WU and 207 SRTP) received kidney transplants between 2004 and 2011, of which 83 patients with deceased donor transplants (59 WU and 24 SRTP) developed DGF, defined as the need for dialysis in the first week posttransplant. RESULTS Patients with DGF were divided into three groups depending on TND [group 1: <7 days (n = 52), group 2: 7-14 days (n = 13) and group 3 (n = 18): >14 days]. The creatinine clearance (CrCl) at 30 days (42.5, 33.8, 20.0 cc/min; P < 0.001) and 1 year (56.7, 49.2, 37.3 cc/min, P = 0.031) were significantly different between the three groups. Multivariate regression analysis identified length of TND posttransplant (β = -0.5, P < 0.001) and donation after cardiac death (DCD) donor (β = 19.5, P < 0.001) as the most significant predictors of CrCl at 1 year in these patients with DGF. DCD kidneys with DGF had a higher CrCl at 1 year and fewer readmissions in the first year compared with non-DCD kidneys with DGF. DISCUSSION Our study suggests that increased TND is associated with worse CrCl at 1 year. The data also support the hypothesis of a different mechanism for DGF in DCD and non-DCD kidneys.