The Natural History and Management of Patients With Pancreatic Pseudocysts as a Complication of Acute Pancreatitis

In this thesis I have studied the natural course, outcome and management of patients who developed a pancreatic pseudocyst following an episode of acute pancreatitis. The clinical information for this work originated in 2 studies involving a total of 129 patients with a pseudocyst. This represents one of the largest reports of such patients in medical literature. One study was of 100 patients with a pseudocyst presenting to Glasgow Royal Infirmary, over a period of 23 years (1962 - 1984 ) (Chapter 3 ) (Imrie et al 1988 . Appendix 1). The second study was of 29 similar patients (Chapter 4) documented during a prospective trial of therapeutic peritoneal lavage in patients with severe acute pancreatitis recorded in Leeds, Bristol and Glasgow (1982 - 1984) (Corfield et al 1985, Mayer et al 1985. Appendix 1). Using the information derived from these studies, I have formulated an assessment system for predicting the likelihood of spontaneous resolution of a pseudocyst (Chapter 8). With the addition of results obtained from an analysis of percutaneous needle aspiration (Chapter 6) and analysis of acute phase reactant proteins within pseudocyst fluid (Chapter 7) I propose a new plan of management for patients with acute pancreatic pseudocysts. The important findings of this thesis are summarised as follows:- 1. The "waiting time" for conservative management of a pancreatic pseudocyst could safely be extended to 12 weeks. Bradley et al (1979) have suggested that a period of 6 weeks from the time of pseudocyst formation should be regarded as both the maximum time to wait for spontaneous resolution of a pseudocyst and the optimum time to consider some form of drainage procedure. A pseudocyst was drained surgically in 78 (%) of the 100 patients from Glasgow Royal Infirmary and resolved spontaneously in the other 22 (%). The median time from diagnosis to drainage by cystogastrostomy was 12 weeks (range 2 - 69 weeks). The median time to complete spontaneous resolution was also 12 weeks (range 2 - 104 weeks). Of the 29 patients from Leeds, Bristol and Glasgow surgical drainage was performed in 11 (38%) at a median time of 7 weeks (range 3-38 weeks) and spontaneous resolution occurred in 15 (52%) at a median time of 7 weeks (range 2-20 weeks). Bradley et al (1979) also found an increasing proportion of patients developed complications the greater the time a pseudocyst was left untreated. Only 6 (5%) of all 129 patients studied suffered complications as a result of an undrained pseudocyst. Based on the above results I suggest that 6 weeks is too short a period and 12 weeks is a more appropriate time to wait for spontaneous resolution to occur provided the is repeatedly assessed by clinical examination and ultrasound scanning to confirm that the diameter of the pseudocyst is not increasing and that the clinical state of the clinical state of the patient is not deteriorating. 2. No single factor causing acute pancreatitis predisposes to pseudocyst formation. Of the 100 patients from Glasgow Royal Infirmary alcohol was the cause of acute pancreatitis in 59%, gallstones in 27% and the aetiology was idiopathic in 9%. In contrast, of the 29 patients from Leeds, Bristol and Glasgow alcohol was the aetiological factor in 23%, gallstones in 48% and it was idiopathic in 23 %. This distribution was very similar to that of a total of 418 patients with acute pancreatitis studied in the three cities (Chapter 4)(gallstones 54%: alcohol 20%: idiopathic 21%). This suggests that no single aetiological factor of acute pancreatitis is more likely to cause pseudocyst formation. 3. The aetiology of the preceding acute pancreatitis is an important factor in determining the outcome of patients with a pseudocyst. The mortality amongst patients from Glasgow Royal Infirmary with gallstone induced pancreatitis and pseudocyst formation was 22% significantly greater than that of patiens with alcohol induced disease (5% mortality. The majority of patients who died as a result of gallstone induced disease did so because of sepsis and/or haemorrhage. The implication from this is that, if possible, in order to decrease the possibility of infection, the biliary tract should be cleared of stones at the time of definitive pseudocyst surgery. 4. Spontaneous resolution of a pseudocyst can be predicted using a multi-factor assessment system. A pseudocyst resolved spontaneously in 22 (%) of the 100 Glasgow Royal Infirmary patients and 15 (52%) of those from Leeds, Bristol and Glasgow. Differences in clinical, laboratory and radiological findings in these patients were compared with those of patients whose pseudocyst needed drainage. The proportion of patients with a palpable abdominal mass was significantly greater in those who required surgery in both groups of patients. The results for the patients from Leeds, Bristol and Glasgow also showed a significantly higher proportion with abdominal distension and a leukocytosis (>10 x 10e9 cells/1) amongst those who underwent surgery. (Abstract shortened by ProQuest.)

An investigation of the Eigenvalue Calibration Method (ECM) using GASP for non-imaging and imaging detectors

Polarised light from astronomical targets can yield a wealth of information about their source radiation mechanisms, and about the geometry of the scattered light regions. Optical observations, of both the linear and circular polarisation components, have been impeded due to non-optimised instrumentation. The need for suitable observing conditions and the availability of luminous targets are also limiting factors. GASP uses division of amplitude polarimeter (DOAP) (Compain and Drevillon) to measure the four components of the Stokes vector simultaneously, which eliminates the constraints placed upon the need for moving parts during observation, and offers a real-time complete measurement of polarisation. Results from the GASP calibration are presented in this work for both a 1D detector system, and a pixel-by-pixel analysis on a 2D detector system. Following Compain et al. we use the Eigenvalue Calibration Method (ECM) to measure the polarimetric limitations of the instrument for each of the two systems. Consequently, the ECM is able to compensate for systematic errors introduced by the calibration optics, and it also accounts for all optical elements of the polarimeter in the output. Initial laboratory results of the ECM are presented, using APD detectors, where errors of 0.2% and 0.1{\deg} were measured for the degree of linear polarisation and polarisation angle respectively. Channel-to-channel image registration is an important aspect of 2-D polarimetry. We present our calibration results of the measured Mueller matrix of each sample, used by the ECM. A set of Zenith flat-field images were recorded during an observing campaign at the Palomar 200 inch telescope in November 2012. From these we show the polarimetric errors from the spatial polarimetry indicating both the stability and absolute accuracy of GASP.Comment: Accepted for publication in Experimental Astronom

The Motion of a Thin Liquid Film Driven by Surfactant and Gravity

We investigate wave solutions of a lubrication model for surfactant-driven flow of a thin liquid film down an inclined plane. We model the flow in one space dimension with a system of nonlinear PDEs of mixed hyperbolic-parabolic type in which the effects of capillarity and surface diffusion are neglected. Numerical solutions reveal distinct patterns of waves that are described analytically by combinations of traveling waves, some with jumps in height and surfactant concentration gradient. The various waves and combinations are strikingly different from what is observed in the case of flow on a horizontal plane. Jump conditions admit new shock waves sustained by a linear surfactant wave traveling upstream. The stability of these waves is investigated analytically and numerically. For initial value problems, a critical ratio of upstream to downstream height separates two distinct long-time wave patterns. Below the critical ratio, there is also an exact solution in which the height is piecewise constant and the surfactant concentration is piecewise linear and has compact support

CELLULAR BASIS OF THE GENETIC CONTROL OF IMMUNE RESPONSES TO SYNTHETIC POLYPEPTIDES : I. DIFFERENCES IN FREQUENCY OF SPLENIC PRECURSOR CELLS SPECIFIC FOR A SYNTHETIC POLYPEPTIDE DERIVED FROM MULTICHAIN POLYPROLINE ([T, G]-PRO--L) IN HIGH AND LOW RESPONDER INBRED MOUSE STRAINS

SJL mice are high responders to the synthetic multichain polypeptide antigen (T,G)-Pro--L, whereas DBA/1 mice are low responders (10, 11). In order to determine whether the genetic control of immune response can be correlated with the number of antigen-sensitive precursor cells, spleen cell suspensions from normal and immunized SJL and DBA/1 donor mice were transplanted into lethally X-irradiated syngeneic recipients (incapable of immune response) along with (T, G)-Pro--L. Anti-(T, G)-Pro--L responses (donor-derived) were assayed in the sera of the hosts 12–16 days later. By transplanting graded and limiting numbers of spleen cells, inocula were found which contained one or a few antigen-sensitive precursors reactive with the immunogen. Using this method to estimate the relative numbers of such cells for the high responder SJL strain, one precursor was detected in ∼1.3 x 106 and ∼7.2 x 106 spleen cells from immunized and normal donors, respectively. In contrast, one precursor was detected in about 30 x 106 spleen cells from low responder DBA/1 mice, irrespective of whether the donors had been immunized. These results indicate that the genetic control of immunity to the synthetic polypeptide antigen investigated is directly correlated to the relative number of precursor cells reactive with the immunogen in high and low responder strains

Gravity-driven Thin Liquid Films with Insoluble Surfactant: Smooth Traveling Waves

The flow of a thin layer of fluid down an inclined plane is modified by the presence of insoluble surfactant. For any finite surfactant mass, traveling waves are constructed for a system of lubrication equations describing the evolution of the free-surface fluid height and the surfactant concentration. The one-parameter family of solutions is investigated using perturbation theory with three small parameters: the coefficient of surface tension, the surfactant diffusivity, and the coefficient of the gravity-driven diffusive spreading of the fluid. When all three parameters are zero, the nonlinear PDE system is hyperbolic/degenerateparabolic, and admits traveling wave solutions in which the free-surface height is piecewise constant, and the surfactant concentration is piecewise linear and continuous. The jumps and corners in the traveling waves are regularized when the small parameters are nonzero; their structure is revealed through a combination of analysis and numerical simulation

An Agent-Based Model of Financial Benchmark Manipulation

Financial benchmarks estimate market values or reference rates used in a wide variety of contexts, but are often calculated from data generated by parties who have incentives to manipulate these benchmarks. Since the the London Interbank Offered Rate (LIBOR) scandal in 2011, market participants, scholars, and regulators have scrutinized financial benchmarks and the ability of traders to manipulate them. We study the impact on market quality and microstructure of manipulating transaction-based benchmarks in a simulated market environment. Our market consists of a single benchmark manipulator with external holdings dependent on the benchmark, and numerous background traders unaffected by the benchmark. All market participants use zero-intelligence trading strategies. When these agents trade under equilibrium settings in our market environment with and without benchmark manipulation, we find that the total surplus of all market participants who are trading increases with manipulation. However, the aggregated market surplus decreases for all trading agents, and the market surplus of the manipulator decreases, so the manipulator’s surplus from the benchmark significantly increases. This entails under natural assumptions that the market and any third parties invested in the opposite side of the benchmark from the manipulator are negatively impacted by this manipulation