B R Davidson

Royal Free London NHS Foundation Trust, Londinium, England, United Kingdom

Are you B R Davidson?

Claim your profile

Publications (204)1004.02 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Endoscopic ultrasound (EUS) and magnetic resonance cholangiopancreatography (MRCP) are tests used in the diagnosis of common bile duct stones in patients suspected of having common bile duct stones prior to undergoing invasive treatment. There has been no systematic review of the accuracy of EUS and MRCP in the diagnosis of common bile duct stones using appropriate reference standards. OBJECTIVES: To determine and compare the accuracy of EUS and MRCP for the diagnosis of common bile duct stones. SEARCH METHODS: We searched MEDLINE, EMBASE, Science Citation Index Expanded, BIOSIS, and Clinicaltrials.gov until September 2012. We searched the references of included studies to identify further studies and of systematic reviews identified from various databases (Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment (HTA), Medion, and ARIF (Aggressive Research Intelligence Facility)). We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively. SELECTION CRITERIA: We included studies that provided the number of true positives, false positives, false negatives, and true negatives for EUS or MRCP. We only accepted studies that confirmed the presence of common bile duct stones by extraction of the stones (irrespective of whether this was done by surgical or endoscopic methods) for a positive test, and absence of common bile duct stones by surgical or endoscopic negative exploration of the common bile duct or symptom free follow-up for at least six months for a negative test, as the reference standard in people suspected of having common bile duct stones. We included participants with or without prior diagnosis of cholelithiasis; with or without symptoms and complications of common bile duct stones, with or without prior treatment for common bile duct stones; and before or after cholecystectomy. At least two authors independently screened abstracts and selected studies for inclusion. DATA COLLECTION AND ANALYSIS: Two authors independently collected the data from each study. We used the bivariate model to obtain pooled estimates of sensitivity and specificity. MAIN RESULTS: We included a total of 18 studies involving 2366 participants (976 participants with common bile duct stones and 1390 participants without common bile duct stones). Eleven studies evaluated EUS alone, and five studies evaluated MRCP alone. Two studies evaluated both tests. Most studies included patients who were suspected of having common bile duct stones based on abnormal liver function tests; abnormal transabdominal ultrasound; symptoms such as obstructive jaundice, cholangitis, or pancreatitis; or a combination of the above. The proportion of participants who had undergone cholecystectomy varied across studies. Not one of the studies was of high methodological quality. For EUS, the sensitivities ranged between 0.75 and 1.00 and the specificities ranged between 0.85 and 1.00. The summary sensitivity (95% confidence interval (CI)) and specificity (95% CI) of the 13 studies that evaluated EUS (1537 participants; 686 cases and 851 participants without common bile duct stones) were 0.95 (95% CI 0.91 to 0.97) and 0.97 (95% CI 0.94 to 0.99). For MRCP, the sensitivities ranged between 0.77 and 1.00 and the specificities ranged between 0.73 and 0.99. The summary sensitivity and specificity of the seven studies that evaluated MRCP (996 participants; 361 cases and 635 participants without common bile duct stones) were 0.93 (95% CI 0.87 to 0.96) and 0.96 (95% CI 0.90 to 0.98). There was no evidence of a difference in sensitivity or specificity between EUS and MRCP (P value = 0.5). From the included studies, at the median pre-test probability of common bile duct stones of 41% the post-test probabilities (with 95% CI) associated with positive and negative EUS test results were 0.96 (95% CI 0.92 to 0.98) and 0.03 (95% CI 0.02 to 0.06). At the same pre-test probability, the post-test probabilities associated with positive and negative MRCP test results were 0.94 (95% CI 0.87 to 0.97) and 0.05 (95% CI 0.03 to 0.09). AUTHORS' CONCLUSIONS: Both EUS and MRCP have high diagnostic accuracy for detection of common bile duct stones. People with positive EUS or MRCP should undergo endoscopic or surgical extraction of common bile duct stones and those with negative EUS or MRCP do not need further invasive tests. However, if the symptoms persist, further investigations will be indicated. The two tests are similar in terms of diagnostic accuracy and the choice of which test to use will be informed by availability and contra-indications to each test. However, it should be noted that the results are based on studies of poor methodological quality and so the results should be interpreted with caution. Further studies that are of high methodological quality are necessary to determine the diagnostic accuracy of EUS and MRCP for the diagnosis of common bile duct stones.
    Cochrane database of systematic reviews (Online) 02/2015; · 5.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Endoscopic retrograde cholangiopancreatography (ERCP) and intraoperative cholangiography (IOC) are tests used in the diagnosis of common bile duct stones in people suspected of having common bile duct stones. There has been no systematic review of the diagnostic accuracy of ERCP and IOC. OBJECTIVES: To determine and compare the accuracy of ERCP and IOC for the diagnosis of common bile duct stones. SEARCH METHODS: We searched MEDLINE, EMBASE, Science Citation Index Expanded, BIOSIS, and Clinicaltrials.gov to September 2012. To identify additional studies, we searched the references of included studies and systematic reviews identified from various databases (Database of Abstracts of Reviews of Effects (DARE)), Health Technology Assessment (HTA), Medion, and ARIF (Aggressive Research Intelligence Facility)). We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively. SELECTION CRITERIA: We included studies that provided the number of true positives, false positives, false negatives, and true negatives for ERCP or IOC. We only accepted studies that confirmed the presence of common bile duct stones by extraction of the stones (irrespective of whether this was done by surgical or endoscopic methods) for a positive test, and absence of common bile duct stones by surgical or endoscopic negative exploration of the common bile duct, or symptom-free follow-up for at least six months for a negative test as the reference standard in people suspected of having common bile duct stones. We included participants with or without prior diagnosis of cholelithiasis; with or without symptoms and complications of common bile duct stones; with or without prior treatment for common bile duct stones; and before or after cholecystectomy. At least two authors screened abstracts and selected studies for inclusion independently. DATA COLLECTION AND ANALYSIS: Two authors independently collected data from each study. We used the bivariate model to summarise the sensitivity and specificity of the tests. MAIN RESULTS: We identified five studies including 318 participants (180 participants with and 138 participants without common bile duct stones) that reported the diagnostic accuracy of ERCP and five studies including 654 participants (125 participants with and 529 participants without common bile duct stones) that reported the diagnostic accuracy of IOC. Most studies included people with symptoms (participants with jaundice or pancreatitis) suspected of having common bile duct stones based on blood tests, ultrasound, or both, prior to the performance of ERCP or IOC. Most studies included participants who had not previously undergone removal of the gallbladder (cholecystectomy). None of the included studies was of high methodological quality as evaluated by the QUADAS-2 tool (quality assessment tool for diagnostic accuracy studies). The sensitivities of ERCP ranged between 0.67 and 0.94 and the specificities ranged between 0.92 and 1.00. For ERCP, the summary sensitivity was 0.83 (95% confidence interval (CI) 0.72 to 0.90) and specificity was 0.99 (95% CI 0.94 to 1.00). The sensitivities of IOC ranged between 0.75 and 1.00 and the specificities ranged between 0.96 and 1.00. For IOC, the summary sensitivity was 0.99 (95% CI 0.83 to 1.00) and specificity was 0.99 (95% CI 0.95 to 1.00). For ERCP, at the median pre-test probability of common bile duct stones of 0.35 estimated from the included studies (i.e., 35% of people suspected of having common bile duct stones were confirmed to have gallstones by the reference standard), the post-test probabilities associated with positive test results was 0.97 (95% CI 0.88 to 0.99) and negative test results was 0.09 (95% CI 0.05 to 0.14). For IOC, at the median pre-test probability of common bile duct stones of 0.35, the post-test probabilities associated with positive test results was 0.98 (95% CI 0.85 to 1.00) and negative test results was 0.01 (95% CI 0.00 to 0.10). There was weak evidence of a difference in sensitivity (P value = 0.05) with IOC showing higher sensitivity than ERCP. There was no evidence of a difference in specificity (P value = 0.7) with both tests having similar specificity. AUTHORS' CONCLUSIONS: Although the sensitivity of IOC appeared to be better than that of ERCP, this finding may be unreliable because none of the studies compared both tests in the same study populations and most of the studies were methodologically flawed. It appears that both tests were fairly accurate in guiding further invasive treatment as most people diagnosed with common bile duct stones by these tests had common bile duct stones. Some people may have common bile duct stones in spite of having a negative ERCP or IOC result. Such people may have to be re-tested if the clinical suspicion of common bile duct stones is very high because of their symptoms or persistently abnormal liver function tests. However, the results should be interpreted with caution given the limited quantity and quality of the evidence.
    Cochrane database of systematic reviews (Online) 02/2015; · 5.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Ultrasound and liver function tests (serum bilirubin and serum alkaline phosphatase) are used as screening tests for the diagnosis of common bile duct stones in people suspected of having common bile duct stones. There has been no systematic review of the diagnostic accuracy of ultrasound and liver function tests. OBJECTIVES: To determine and compare the accuracy of ultrasound versus liver function tests for the diagnosis of common bile duct stones. SEARCH METHODS: We searched MEDLINE, EMBASE, Science Citation Index Expanded, BIOSIS, and Clinicaltrials.gov to September 2012. We searched the references of included studies to identify further studies and systematic reviews identified from various databases (Database of Abstracts of Reviews of Effects, Health Technology Assessment, Medion, and ARIF (Aggressive Research Intelligence Facility)). We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively. SELECTION CRITERIA: We included studies that provided the number of true positives, false positives, false negatives, and true negatives for ultrasound, serum bilirubin, or serum alkaline phosphatase. We only accepted studies that confirmed the presence of common bile duct stones by extraction of the stones (irrespective of whether this was done by surgical or endoscopic methods) for a positive test result, and absence of common bile duct stones by surgical or endoscopic negative exploration of the common bile duct, or symptom-free follow-up for at least six months for a negative test result as the reference standard in people suspected of having common bile duct stones. We included participants with or without prior diagnosis of cholelithiasis; with or without symptoms and complications of common bile duct stones, with or without prior treatment for common bile duct stones; and before or after cholecystectomy. At least two authors screened abstracts and selected studies for inclusion independently. DATA COLLECTION AND ANALYSIS: Two authors independently collected data from each study. Where meta-analysis was possible, we used the bivariate model to summarise sensitivity and specificity. MAIN RESULTS: Five studies including 523 participants reported the diagnostic accuracy of ultrasound. One studies (262 participants) compared the accuracy of ultrasound, serum bilirubin and serum alkaline phosphatase in the same participants. All the studies included people with symptoms. One study included only participants without previous cholecystectomy but this information was not available from the remaining studies. All the studies were of poor methodological quality. The sensitivities for ultrasound ranged from 0.32 to 1.00, and the specificities ranged from 0.77 to 0.97. The summary sensitivity was 0.73 (95% CI 0.44 to 0.90) and the specificity was 0.91 (95% CI 0.84 to 0.95). At the median pre-test probability of common bile duct stones of 0.408, the post-test probability (95% CI) associated with positive ultrasound tests was 0.85 (95% CI 0.75 to 0.91), and negative ultrasound tests was 0.17 (95% CI 0.08 to 0.33).The single study of liver function tests reported diagnostic accuracy at two cut-offs for bilirubin (greater than 22.23 μmol/L and greater than twice the normal limit) and two cut-offs for alkaline phosphatase (greater than 125 IU/L and greater than twice the normal limit). This study also assessed ultrasound and reported higher sensitivities for bilirubin and alkaline phosphatase at both cut-offs but the specificities of the markers were higher at only the greater than twice the normal limit cut-off. The sensitivity for ultrasound was 0.32 (95% CI 0.15 to 0.54), bilirubin (cut-off greater than 22.23 μmol/L) was 0.84 (95% CI 0.64 to 0.95), and alkaline phosphatase (cut-off greater than 125 IU/L) was 0.92 (95% CI 0.74 to 0.99). The specificity for ultrasound was 0.95 (95% CI 0.91 to 0.97), bilirubin (cut-off greater than 22.23 μmol/L) was 0.91 (95% CI 0.86 to 0.94), and alkaline phosphatase (cut-off greater than 125 IU/L) was 0.79 (95% CI 0.74 to 0.84). No study reported the diagnostic accuracy of a combination of bilirubin and alkaline phosphatase, or combinations with ultrasound. AUTHORS' CONCLUSIONS: Many people may have common bile duct stones in spite of having a negative ultrasound or liver function test. Such people may have to be re-tested with other modalities if the clinical suspicion of common bile duct stones is very high because of their symptoms. False-positive results are also possible and further non-invasive testing is recommended to confirm common bile duct stones to avoid the risks of invasive testing.It should be noted that these results were based on few studies of poor methodological quality and the results for ultrasound varied considerably between studies. Therefore, the results should be interpreted with caution. Further studies of high methodological quality are necessary to determine the diagnostic accuracy of ultrasound and liver function tests.
    Cochrane database of systematic reviews (Online) 02/2015; · 5.70 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Liver biopsy is the reference standard for diagnosing the extent of fibrosis in chronic liver disease; however, it is invasive, with the potential for serious complications. Alternatives to biopsy include non-invasive liver tests (NILTs); however, the cost-effectiveness of these needs to be established. To assess the diagnostic accuracy and cost-effectiveness of NILTs in patients with chronic liver disease. We searched various databases from 1998 to April 2012, recent conference proceedings and reference lists. We included studies that assessed the diagnostic accuracy of NILTs using liver biopsy as the reference standard. Diagnostic studies were assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Meta-analysis was conducted using the bivariate random-effects model with correlation between sensitivity and specificity (whenever possible). Decision models were used to evaluate the cost-effectiveness of the NILTs. Expected costs were estimated using a NHS perspective and health outcomes were measured as quality-adjusted life-years (QALYs). Markov models were developed to estimate long-term costs and QALYs following testing, and antiviral treatment where indicated, for chronic hepatitis B (HBV) and chronic hepatitis C (HCV). NILTs were compared with each other, sequential testing strategies, biopsy and strategies including no testing. For alcoholic liver disease (ALD), we assessed the cost-effectiveness of NILTs in the context of potentially increasing abstinence from alcohol. Owing to a lack of data and treatments specifically for fibrosis in patients with non-alcoholic fatty liver disease (NAFLD), the analysis was limited to an incremental cost per correct diagnosis. An analysis of NILTs to identify patients with cirrhosis for increased monitoring was also conducted. Given a cost-effectiveness threshold of £20,000 per QALY, treating everyone with HCV without prior testing was cost-effective with an incremental cost-effectiveness ratio (ICER) of £9204. This was robust in most sensitivity analyses but sensitive to the extent of treatment benefit for patients with mild fibrosis. For HBV [hepatitis B e antigen (HBeAg)-negative)] this strategy had an ICER of £28,137, which was cost-effective only if the upper bound of the standard UK cost-effectiveness threshold range (£30,000) is acceptable. For HBeAg-positive disease, two NILTs applied sequentially (hyaluronic acid and magnetic resonance elastography) were cost-effective at a £20,000 threshold (ICER: £19,612); however, the results were highly uncertain, with several test strategies having similar expected outcomes and costs. For patients with ALD, liver biopsy was the cost-effective strategy, with an ICER of £822. A substantial number of tests had only one study from which diagnostic accuracy was derived; therefore, there is a high risk of bias. Most NILTs did not have validated cut-offs for diagnosis of specific fibrosis stages. The findings of the ALD model were dependent on assuptions about abstinence rates assumptions and the modelling approach for NAFLD was hindered by the lack of evidence on clinically effective treatments. Treating everyone without NILTs is cost-effective for patients with HCV, but only for HBeAg-negative if the higher cost-effectiveness threshold is appropriate. For HBeAg-positive, two NILTs applied sequentially were cost-effective but highly uncertain. Further evidence for treatment effectiveness is required for ALD and NAFLD. This study is registered as PROSPERO CRD42011001561. The National Institute for Health Research Health Technology Assessment programme.
    Health technology assessment (Winchester, England) 01/2015; 19(9):1-410. DOI:10.3310/hta19090 · 5.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: The cost-effectiveness of non-invasive tests (NITs) as alternatives to liver biopsy is unknown. We compared the cost-effectiveness of using NITs to inform treatment decisions in adult patients with chronic hepatitis C (CHC).Methods: We conducted a systematic review and meta-analysis to calculate the diagnostic accuracy of various NITs using a bivariate random-effects model. We constructed a probabilistic decision analytical model to estimate health care costs and outcomes (QALYs) using data from the meta-analysis, literature, and national UK data. We compared the cost-effectiveness of four treatment strategies: testing with NITs and treating patients with fibrosis stage ≥F2, testing with liver biopsy and treating patients with ≥F2, treat none and treat all irrespective of fibrosis. We compared all NITs and tested the cost-effectiveness using current triple therapy with boceprevir or telaprevir but also modeled new, more potent antivirals.Findings: Treating all patients without any prior NIT was the most effective strategy and had an incremental cost-effectiveness ratio (ICER) of £9,204/additional QALY gained. The exploratory analysis of currently licensed sofosbuvir treatment regimens found that treat all was cost-effective compared to using an NIT to decide on treatment, with an ICER of £16,028/QALY gained. The exploratory analysis to assess the possible impact on results of new treatments, found that if SVR rates increased to >90% for genotypes 1-4, the incremental treatment cost threshold for the “treat all” strategy to remain the most cost-effective strategy would be £37,500. Above this threshold, the most cost-effective option would be non-invasive testing with MR elastography (ICER=£9,189).Conclusions: Treating all adult patients with CHC, irrespective of fibrosis stage, is the most cost-effective strategy with currently available drugs in developed countries. (Hepatology 2014)
    Hepatology 09/2014; 60(3). DOI:10.1002/hep.27296 · 11.19 Impact Factor
  • S. Morris, K. S. Gurusamy, N. Patel, B. R. Davidson
    [Show abstract] [Hide abstract]
    ABSTRACT: BackgroundA recent Cochrane review suggested that laparoscopic cholecystectomy carried out early following mild gallstone pancreatitis was safe. This study compared the cost-effectiveness of laparoscopic cholecystectomy performed within 3 days of admission, during the same admission but after more than 3 days, or electively in a subsequent admission.MethodsA model-based cost–utility analysis was performed estimating mean costs and quality-adjusted life-years (QALYs) per patient in the UK National Health Service with a 1-year time horizon. A decision tree model was constructed and populated with probabilities, outcomes and cost data from published sources for mild gallstone pancreatitis, including one-way and probabilistic sensitivity analyses.ResultsThe costs of laparoscopic cholecystectomy performed within 3 days of admission, beyond 3 days but in the same admission, and electively in a subsequent admission were €2748, €3543 and €3752 respectively; the QALYs were 0·888, 0·888 and 0·884 respectively. Early laparoscopic cholecystectomy had a 91 per cent probability of being cost-effective at the maximum willingness to pay for a QALY commonly used in the UK. It is acknowledged that many hospitals do not have access to magnetic resonance cholangiopancreatography and endoscopic retrograde cholangiopancreatography, especially at weekends, and that implementing a 3-day target is unrealistic without allocating new resources that could erode the cost-effectiveness.Conclusion Performing laparoscopic cholecystectomy for mild gallstone pancreatitis within 3 days of admission is cost-effective, but may not be feasible without significant resource allocation. After 3 days there is little financial advantage to same-admission operation.
    British Journal of Surgery 06/2014; 101(7). DOI:10.1002/bjs.9501 · 5.21 Impact Factor
  • Source
    Journal of Hepatology 01/2014; DOI:10.1016/j.jhep.2013.12.031 · 10.40 Impact Factor
  • Cryobiology 12/2013; 67(3):420. DOI:10.1016/j.cryobiol.2013.09.085 · 1.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This meta-analysis aimed to investigate whether preoperative biliary drainage (PBD) is beneficial to patients with obstructive jaundice. Data from randomized clinical trials related to safety and effectiveness of PBD versus no PBD were extracted by two independent reviewers. Risk ratios, rate ratios or mean differences were calculated with 95 per cent confidence intervals (c.i.), based on intention-to-treat analysis, whenever possible. Six trials (four using percutaneous transhepatic biliary drainage and two using endoscopic sphincterotomy) including 520 patients with malignant or benign obstructive jaundice comparing PBD (265 patients) with no PBD (255) were included in this review. All trials had a high risk of bias. There was no significant difference in mortality (risk ratio 1.12, 95 per cent c.i. 0·73 to 1·71; P = 0·60) between the two groups. Overall serious morbidity (grade III or IV, Clavien-Dindo classification) was higher in the PBD group (599 complications per 1000 patients) than in the direct surgery group (361 complications per 1000 patients) (rate ratio 1·66, 95 per cent c.i. 1·28 to 2·16; P < 0·001). Quality of life was not reported in any of the trials. There was no significant difference in length of hospital stay between the two groups: mean difference 4·87 (95 per cent c.i. -1·28 to 11·02) days (P = 0·12). PBD in patients undergoing surgery for obstructive jaundice is associated with similar mortality but increased serious morbidity compared with no PBD. Therefore, PBD should not be used routinely.
    British Journal of Surgery 11/2013; 100(12):1589-1596. DOI:10.1002/bjs.9260 · 5.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Early results of a randomised trial showed reduced fibrosis due to recurrent HCV hepatitis with tacrolimus triple therapy (TT) versus monotherapy (MT) following transplantation for HCV cirrhosis. We evaluated the clinical outcomes after a median 8 years of follow-up, including differences in fibrosis assessed by collagen proportionate area (CPA). 103 consecutive liver transplant recipients with HCV cirrhosis receiving cadaveric grafts were randomised to tacrolimus MT (n=54) or TT (n=49) with daily tacrolimus (0.1 mg/kg divided dose), azathioprine (1 mg/kg) and prednisolone (20 mg), the last tailing off to zero by 6 months. Both groups had serial transjugular biopsies with hepatic venous pressure gradient (HVPG) measurement. Time to reach Ishak stage 4 was the predetermined endpoint. CPA was measured in all biopsies. Factors associated with HCV recurrence were evaluated. Clinical decompensation was the first occurrence of ascites/hydrothorax, variceal bleeding or encephalopathy. No significant preoperative, peri-operative or postoperative differences between groups were found. During 96 months median follow-up, stage 4 fibrosis was reached in 19 MT/11 TT with slower fibrosis progression in TT (p=0.009). CPA at last biopsy was 12% in MT and 8% in TT patients (p=0.004). 14 MT/ three TT patients reached HVPG≥10 mm Hg (p=0.002); 10 MT/three TT patients, decompensated. Multivariately, allocated MT (p=0.047, OR 3.23, 95% CI 1.01 to 10.3) was independently associated with decompensation: 14 MT/ seven TT died, and five MT/ four TT were retransplanted. Long term immunosuppression with tacrolimus, azathioprine and short term prednisolone in HCV cirrhosis recipients resulted in slower progression to severe fibrosis assessed by Ishak stage and CPA, less portal hypertension and decompensation, compared with tacrolimus alone. ISRCTN94834276: Randomised study for immunosuppression regimen in liver transplantation.
    Gut 10/2013; 63(6). DOI:10.1136/gutjnl-2013-305606 · 13.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Although hepatocytes have a remarkable regenerative power, the rapidity of acute liver failure makes liver transplantation the only definitive treatment. Attempts to incorporate engineered three-dimensional liver tissue in bioartificial liver devices or in implantable tissue constructs, to treat or bridge patients to self-recovery, were met with many challenges, amongst which is to find suitable polymeric matrices. We studied the feasibility of utilising nanocomposite polymers in three-dimensional scaffolds for hepatocytes.Materials and methods: Hepatocytes (HepG2) were seeded on a flat sheet and in three-dimensional scaffolds made of a nanocomposite polymer (Polyhedral Oligomeric Silsesquioxane [POSS]-modified polycaprolactone urea urethane) alone as well as with porogen particles, i.e. glucose, sodium bicarbonate and sodium chloride. The scaffold architecture, cell attachment and morphology were studied with scanning electron microscopy, and we assessed cell viability and functionality.Results: Cell attachment to the scaffolds was demonstrated. The scaffold made with glucose particles as porogen showed a narrower range of pore size with higher porosity and better inter-pore communications and seemed to encourage near normal cell morphology. There was a steady increase of albumin secretion throughout the experiment while the control (monolayer cell culture) showed a steep decrease after day 7. At the end of the experiment, there was no significant difference in viability and functionality between the scaffolds and the control.Conclusion: In this initial study, porogen particles were used to modify the scaffolds produced from the novel polymer. Although there was no significance against the control in functionality and viability, the demonstrable attachment on scanning electron microscopy suggest potential roles for this polymer and in particular for scaffolds made with glucose particles in liver tissue engineering.
    Journal of Biomaterials Applications 04/2012; 28(2). DOI:10.1177/0885328212445404 · 2.76 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Remote ischemic preconditioning (RIPC) protects against liver ischemia reperfusion (IR) injury. An essential circulating mediator of this protection is nitric oxide (NO) induced by lower limb RIPC. One of the mechanisms through which NO generally acts is the soluble guanylyl cyclase-cyclic GMP (sGC-cGMP) pathway. The present study aimed to assess the role of hepatic sGC-cGMP in lower limb RIPC-induced protection against liver IR injury. Mice were allocated to 4 groups: 1.Sham; 2.IR: 40 min of lobar hepatic ischemia and 2 hr reperfusion; 3.RIPC+IR: 6 cycles of 4x4 min IR of the lower limb followed by IR group procedure; (4) 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ)+RIPC+IR: ODQ (sGC inhibitor) was administered followed by RIPC+IR group procedure. Hepatic microcirculatory blood flow (MBF) was measured throughout the experiment. Plasma transaminases, hepatic histopathological and transmission electron microscopy studies were performed at the end of the experiment. Hepatic cGMP levels were measured in groups 1-3 in addition to an RIPC alone group. Compared to liver IR alone, RIPC+IR increased hepatic MBF during liver reperfusion (P<0.05), and reduced plasma transaminases (P<0.05) and ultrastructural markers of injury. In contrast compared to RIPC+IR, ODQ+RIPC+IR decreased hepatic MBF (P<0.05) and ultrastructural markers of injury. However, plasma transaminases were not significantly different in the ODQ+RIPC+IR compared to the RIPC+IR group. Hepatic cGMP levels were significantly elevated in the RIPC compared to sham group. The hepatic sGC-cGMP pathway is required for mediating the protective effects of lower limb RIPC on hepatic MBF in liver IR injury.
    Transplantation 03/2012; 93(9):880-6. DOI:10.1097/TP.0b013e31824cd59d · 3.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ischaemia reperfusion (IR) injury is a clinical entity with a major contribution to the morbidity and mortality of liver surgery and transplantation. A central pathway of protection against IR injury utilizes nitric oxide (NO). Nitric oxide synthase (NOS) enzymes manufacture NO from L-arginine. NO generated by the endothelial NOS (eNOS) isoform protects against liver IR injury, whereas inducible NOS (iNOS)-derived NO may have either a protective or a deleterious effect during the early phase of IR injury, depending on the length of ischaemia, length of reperfusion and experimental model. In late phase hepatic IR injury, iNOS-derived NO plays a protective role. In addition to NOS consumption of L-arginine during NO synthesis, this amino acid may also be metabolized by arginase, an enzyme whose release is increased during prolonged ischaemia, and therefore diverts L-arginine away from NOS metabolism leading to a drop in the rate of NO synthesis. NO most commonly acts through the soluble guanylyl cyclase-cyclic GMP- protein kinase G pathway to ameliorate hepatic IR injury. Both endogenously generated and exogenously administered NO donors protect against liver IR injury. The beneficial effects of NO on liver IR are not, however, universal, and certain conditions, such as steatosis, may influence the protective effects of NO. In this review, the evidence for, and mechanisms of these protective actions of NO are discussed, and areas in need of further research are highlighted.
    Liver international: official journal of the International Association for the Study of the Liver 02/2012; 32(4):531-43. DOI:10.1111/j.1478-3231.2012.02755.x · 4.41 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Roux-en-Y loop is considered the reconstruction method of choice in Orthotopic Liver Transplantation (OLT) for Primary Sclerosing Cholangitis (PSC). We have adopted an approach of duct-to-duct (D-D) reconstruction when recipient common bile duct is free of gross disease. Patients were divided into two groups: patients who underwent a Roux-en-Y choledochojejunostomy and patients who had a D-D anastomosis. Morbidity, mortality, disease recurrence and graft and patient survival were compared between the two groups and analyzed. Ninety-one patients had OLT for PSC. Sixty-three patients underwent a D-D biliary reconstruction, whereas 28 patients had a Roux-en-Y loop. Biliary leak complicated 8% from the D-D group, and 14% from the Roux-en-Y group (P = 0.08), whereas biliary strictures were identified in 10% vs. 7% patients from the D-D and Roux-en-Y group, respectively (P = 0.9). Actuarial 1, 3 and 10 year survival for D-D and Roux-en-Y group was (87%, 80% and 62%) and (82%, 73% and 73%), respectively (P = 0.7). The corresponding 1, 3 and 10 year graft survival was (72%, 58% and 42%) and (67%, 58% and 53%), respectively (P = 0.6). No difference was seen in disease recurrence rates. D-D biliary reconstruction in OLT for selected PSC patients remains our first option of reconstruction.
    Transplant International 01/2012; 25(1):64-8. DOI:10.1111/j.1432-2277.2011.01371.x · 3.16 Impact Factor
  • K Gurusamy, B R Davidson
    British Journal of Surgery 01/2012; 99(1):144. DOI:10.1002/bjs.7827 · 5.21 Impact Factor
  • V. Allen, K.S. Gurusamy, A. Kalia, B.R. Davidson
    International Journal of Surgery 12/2011; 9(5):366. DOI:10.1016/j.ijsu.2011.03.009 · 1.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Most patients with gallbladder and common bile duct stones are treated by preoperative endoscopic sphincterotomy (POES) followed by laparoscopic cholecystectomy. Recently, intraoperative endoscopic sphincterotomy (IOES) during laparoscopic cholecystectomy has been suggested as an alternative treatment. Data from randomized clinical trials related to safety and effectiveness of IOES versus POES were extracted by two independent reviewers. Risk ratios (RRs) or mean differences were calculated with 95 per cent confidence intervals based on intention-to-treat analysis whenever possible. Four trials with 532 patients comparing IOES with POES were included. There were no deaths. There was no significant difference in rates of ampullary cannulation (RR 1·01, 0·97 to 1·04; P = 0·70) or stone clearance by ES (RR 0·99, 0·96 to 1·02; P = 0·58) between the groups. The proportion of patients with at least one post-ES complication, including pancreatitis, bleeding, perforation, cholangitis, cholecystitis or gastric ulcer, was significantly lower in the IOES group (RR 0·37, 0·18 to 0·78; P = 0·009). There was no significant difference in morbidity after laparoscopic cholecystectomy or requirement for open operation between the groups. Mean hospital stay was 3 days shorter in the IOES group: mean difference - 2·83 (-3·66 to - 2·00) days (P < 0·001). In patients with gallbladder and common bile duct stones, IOES is as effective and safe as POES and results in a significantly shorter hospital stay.
    British Journal of Surgery 07/2011; 98(7):908-16. DOI:10.1002/bjs.7460 · 5.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cold preservation injury influences islet graft function. Reliable tools for real-time assessment of pancreas viability before islet isolation are lacking. Phosphorus magnetic resonance spectroscopy ((31)P-MRS) was used immediately after organ harvest to study rat pancreases at 4 °C to 6 °C in five randomized preservation groups: Marshall's solution, static two-layer method (TLM), continuous TLM with oxygen perfused at 0.5 L/min, and static TLM or continuous TLM both the latter following 30 minutes of warm ischemia (WI). (31)P spectra were analyzed for phosphomonoesters, inorganic phosphate (Pi) and α-, β-and γ-nucleotide triphosphate. Intergroup rates of change of [γ-adenosine triphosphate (ATP)]/[Pi] and [β-ATP]/[Pi] throughout preservation period were significantly different. For continuous TLM there was an increase relative to baseline (0.043 (SD0.033) h(-1) and 0.029 (0.029) h(-1), respectively) but a decrease for both static TLM (-0.023 (0.016) h(-1) and 0.015 (0.026), P < .001 and < .05, respectively) and Marshall's (-0.049 (0.025) h(-1) and -0.036 (0.019) h(-1), respectively, both P < .001) with respect to continuous TLM. Rate of decrease was similar for the Marshall's and static TLM groups. [γ-ATP]/[Pi] and [β-ATP]/[Pi] increased with WI continuous TLM (0.008 [0.009] h(-1) and 0.007 [0.008] hr(-1), respectively) but decreased for WI static TLM (-0.018 (0.008) h(-1) and -0.014 (0.004) hr(-1), respectively, P < .001). (31)P-MRS is an effective tool for noninvasive assessment of pancreas bioenergetics. Continuous TLM preserves cellular bioenergetics and is superior to current non-perfluorocar bone based solutions for pancreas preservation.
    Transplantation Proceedings 06/2011; 43(5):1801-9. DOI:10.1016/j.transproceed.2011.02.019 · 0.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hindlimb remote ischemic preconditioning (RIPC) reduces liver ischemia/reperfusion (IR) injury in wild-type mice. The underlying mechanisms of RIPC are currently unknown. In this study, we investigated the role of endothelial nitric oxide synthase (eNOS) in mediating the protective effects of RIPC. Endothelial nitric oxide synthase knockout (eNOS(-/-) ) mice were divided into 4 groups: (1) a sham surgery group, (2) an RIPC group (6 cycles of 4 minutes of hindlimb ischemia and 4 minutes of hindlimb reperfusion), (3) an IR group [40 minutes of lobar (70%) hepatic ischemia and 2 hours of reperfusion], and (4) an RIPC+IR group (RIPC followed by the IR group procedures). Plasma liver aminotransferases, hepatic histopathological injury scores, transmission electron microscopy studies, and hepatic microcirculatory blood flow (MBF) were assessed. eNOS protein expression was analyzed in the livers and hindlimb muscles of wild-type mice. Hindlimb RIPC did not protect against subsequent liver IR injury in eNOS(-/-) mice; this was demonstrated by the lack of reduction in the plasma aminotransferase levels, histopathological scores, or ultrastructural features of IR injury in the RIPC+IR group versus the IR group. Hepatic MBF did not recover during liver reperfusion in the RIPC+IR group versus the IR group. eNOS protein expression was similar among all wild-type groups. In conclusion, eNOS is essential for the protective effects of hindlimb RIPC on liver IR injury. eNOS exerts its protective effects through the preservation of hepatic MBF. At 2 hours of reperfusion, eNOS protection is likely due to the increased activation of eNOS rather than increased expression.
    Liver Transplantation 05/2011; 17(5):610-9. DOI:10.1002/lt.22272 · 3.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Cochrane Hepato-Biliary Group (CHBG) is one of the 52 collaborative review groups within The Cochrane Collaboration. The activities of the CHBG focus on collecting hepato-biliary randomized clinical trials (RCT) and controlled clinical trials (CCT), and including them in systematic reviews with meta-analyses of the trials. In this overview, we present the growth of The CHBG Controlled Trials Register, as well as the systematic reviews that have been produced since March 1996. The CHBG register includes almost 11,000 RCT and 700 CCT publications. The earliest RCT in the register were published in 1955, and the earliest CCT in 1945. From 1945 to 1980, there were less than 100 publications each year. From 1981 to 1997, their number increased from over 100 to 600 a year. After 1997, the number of publications seems to have been decreasing. The CHBG has published 199 protocols for systematic reviews and 107 systematic reviews through to August 2009 in which 21% of the RCT and CCT were included. The CHBG reviews have been cited approximately 1200 times. A large amount of work has been carried out since 1996. However, there is still much to do, as the CHBG register contains a great number of RCT and CCT on topics that have not yet been systematically reviewed.
    Journal of Gastroenterology and Hepatology 04/2011; 26(4):649-56. DOI:10.1111/j.1440-1746.2010.06465.x · 3.63 Impact Factor

Publication Stats

4k Citations
1,004.02 Total Impact Points

Institutions

  • 1996–2014
    • Royal Free London NHS Foundation Trust
      Londinium, England, United Kingdom
  • 2002–2011
    • Royal Free Academy of PMC
      Londinium, England, United Kingdom
  • 1999–2011
    • University College London
      • • Division of Surgery and Interventional Science
      • • Department of Pathology
      • • Department of Medical Physics and Bioengineering
      Londinium, England, United Kingdom
  • 2003–2008
    • University College London Hospitals NHS Foundation Trust
      • Department of Surgery
      Londinium, England, United Kingdom
    • Imperial College London
      Londinium, England, United Kingdom
  • 1994–2001
    • University of London
      Londinium, England, United Kingdom
  • 1997
    • M. K. Haji Orphanage Hospital
      Malappuram, Kerala, India