Tiing Leong Ang

Changi General Hospital, Tumasik, Singapore

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Publications (144)639.19 Total impact

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    ABSTRACT: Autoimmune pancreatitis (AIP) is often misdiagnosed as pancreatic carcinoma (PC) despite recent advances in imaging tests. The aim of the study was to evaluate whether the quantitative perfusion analysis using software "Time intensity curve" with contrast-enhanced harmonic EUS (CH-EUS) facilitate the differentiation of AIP from PC. Consecutive patients with focal AIP and pancreatic carcinoma who underwent CH-EUS from January 2009 to September 2010 were analyzed. CH-EUS was performed with intravenous administration of an ultrasonographic contrast (Sonazoid) and electronic radial echoendoscope. The graph of time intensity curve (TIC) for pancreatic mass was generated to depict the changes in signal intensity over time within the region of interest (ROI). ROI was placed to cover an area with a pancreatic mass lesion. Based on the analysis of TIC, base intensity before injection (BI), peak intensity (PI), time to peak, and maximum intensity gain (MIG: PI-BI) were calculated. Eight patients with focal AIP and twenty-two patients with PC were evaluated by TIC. PI and MIG of mass lesion of AIP were significantly higher than that of PC (21.4 dB vs. 9.6 dB, 17.5 vs. 6.6). Receiver operating characteristics analysis yielded an optimal MIG cutoff value of 12.5 with high sensitivity and specificity. Pancreatic mass lesions of AIP and PC exhibited markedly different patterns with the TIC. This novel diagnostic modality using TIC generated by CH-EUS might offer an opportunity to improve accuracy in the differential diagnosis between pancreatic mass lesion of AIP and PC.
    Scandinavian Journal of Gastroenterology 04/2012; 47(7):853-60. DOI:10.3109/00365521.2012.679686 · 2.33 Impact Factor
  • Gastrointestinal Endoscopy 04/2012; 75(4):AB203. DOI:10.1016/j.gie.2012.04.354 · 4.90 Impact Factor
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    ABSTRACT: Endoscopic retrograde cholangiopancreatography (ERCP) is an advanced procedure with significant complication rate of 5 to 10%. Scant data is available on quality indicators for trainee-involved ERCP. In our study, we evaluated the outcome of trainee-involved ERCPs in which a protocol-based strategy to minimize complications during selective biliary cannulation was adopted. Hands-on training was excluded if patients had ASA grade > 3. The trainee's attempts at selective biliary cannulation were stopped and the procedure taken over by the supervising expert endoscopist if the following factors were encountered: (1) failed cannulation after 5 attempts; (2) unsuccessful cannulation after 10 minutes; (3) edematous papilla; (4) pancreatic duct cannulation ≥ 2 times. After successful ductal cannulation, the trainee was allowed to continue additional hands on training in other aspects such as stone extraction and stenting. During the study period, 331 patients underwent ERCP. Trainee group (TG) consisted of 85 patients; mean age 70 (range 27-99). Expert group (EG) consisted of 246 patients; mean age 65 (range 19-98). The overall technical success rate was 97.9% and there was no significant difference between TG (98.8%) and EG (97.6%). The overall complication rate was 3.9% and there was no difference between TG (3.5%) and EG (4%). In TG, although inadvertent pancreatic duct cannulation occurred in 12/85 (14.1%), acute pancreatitis developed only in 3/85 (3.5%). The high success and low complication rates in trainee-involved and expert-only ERCP procedures were similar. While using a protocol-based strategy, good clinical outcome during the provision of hands-on training for ERCP was observed.
    04/2012; 2(2):66-69. DOI:10.4161/jig.22199
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    ABSTRACT: BACKGROUND AND AIM: Environmental factors such as food, lifestyle and prevalence of Helicobacter pylori infection are widely different in Asian countries compared with the West, and physiological functions and genetic factors of Asians may also be different from those of Westerners. Establishing an Asian consensus for functional dyspepsia is crucial in order to attract attention to such data from Asian countries, to articulate the experience and views of Asian experts, and to provide a relevant guide on management of functional dyspepsia for primary care physicians working in Asia. METHODS: Consensus team members were selected from Asian experts and consensus development was carried out by using a modified Delphi method. Consensus teams collected published papers on functional dyspepsia especially from Asia and developed candidate consensus statements based on the generated clinical questions. At the first face-to-face meeting, each statement was reviewed and e-mail voting was done twice. At the second face-to-face meeting, final voting on each statement was done using a keypad voting system. A grade of evidence and strength of recommendation were applied to each statement according to the method of the GRADE Working Group. RESULTS: Twenty-nine consensus statements were finalized, including seven for definition and diagnosis, five for epidemiology, nine for pathophysiology, and eight for management. Algorithms for diagnosis and management of functional dyspepsia were added. Conclusions:  This consensus developed by Asian experts shows distinctive features of functional dyspepsia in Asia and will provide a guide to the diagnosis and management of functional dyspepsia for Asian primary care physicians.
    Journal of Gastroenterology and Hepatology 04/2012; 27(4):626-41. · 3.63 Impact Factor
  • Tiing Leong Ang, Kwong Ming Fock
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    ABSTRACT: In Singapore colorectal cancer (CRC) is the most common cancer for males, second most common cancer for females and most common cancer overall. A national CRC screening program for average risks individuals was started in July 2011, with the primary test modality being the faecal immunochemical test. Individuals may choose to undergo screening colonoscopy directly. Colonoscopy has two roles in CRC screening. It is performed either as a primary screening test or used to evaluate abnormal results from another screening test. Colonoscopy is a safe and effective procedure but potential risks exist. Local complications such as perforation and bleeding, cardiopulmonary events and even mortality may occur. Additionally there could be failed cecal intubation and missed lesions. It is imperative that prior to colonoscopy, there is a proper discussion of risks, benefits and alternatives. To provide quality assurance for colonoscopy in the CRC screening program, a set of quality indicators and criteria for endoscopists and endoscopy centres was established. The endoscopists must be qualified specialists with a lifetime experience of at least 500 colonoscopies and 50 polypectomies, and need to meet annual monitoring parameters that include at least 50 colonoscopies, >95% cecal intubation rate, >95% recovery rate of excised polyps, and withdrawal time of at least 6 minutes. In addition, complication rates must be within acceptable limits such as perforation rate of less than 0.1% and postpolypectomy bleeding rate less than 1%.
    01/2012; 10(3):219. DOI:10.5217/ir.2012.10.3.219
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    ABSTRACT: To determine the immediate and long-term results of endoscopic drainage and necrosectomy for symptomatic pancreatic fluid collections. The data of 80 patients with symptomatic pancreatic fluid collections (mean diameter: 11.7 cm, range 3-20; pseudocysts: 24/80, abscess: 20/80, infected walled-off necrosis: 36/80) referred for endoscopic management from October 1997 to March 2008 were analyzed retrospectively. Endoscopic drainage techniques included endoscopic ultrasound (EUS)-guided aspiration (2/80), EUS-guided transenteric drainage (70/80) and non-EUS-guided drainage across a spontaneous transenteric fistula (8/80). Endoscopic necrosectomy was carried out in 49/80 (abscesses: 14/20; infected necrosis: 35/36). Procedural complications were bleeding (12/80), perforation (7/80), portal air embolism (1/80) and Ogilvie Syndrome (1/80). Initial technical success was achieved in 78/80 (97.5%) and clinical resolution of the collections was achieved endoscopically in 67/80 (83.8%), with surgery required in 13/80 (perforation: four; endoscopically inaccessible areas: two; inadequate drainage: seven). Within 6 months five patients required surgery due to recurrent fluid collections; over a mean follow up of 31 months, surgery was required in four more patients due to recurrent collections as a consequence of underlying pancreatic duct abnormalities that could not be treated endoscopically. The long-term success of endoscopic treatment was 58/80 (72.5%). Endoscopic drainage of symptomatic pancreatic fluid collections is safe and effective, with excellent immediate and long-term results. Endoscopic necrosectomy has a risk of serious complications. The underlying pancreatic duct abnormalities must be addressed to prevent recurrence of fluid collections.
    Digestive Endoscopy 01/2012; 24(1):36-41. DOI:10.1111/j.1443-1661.2011.01162.x · 1.99 Impact Factor
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    ABSTRACT: Narrow band imaging (NBI) and NBI-magnifying endoscopy (ME) have been reported to facilitate the diagnosis of intestinal metaplasia (IM) and early gastric cancer (EGC) in high-risk populations. This study aimed at comparing the detection rate of focal gastric lesions by NBI against white light endoscopy (WLE), and examined the utility of NBI-ME in differentiating gastric mucosal pathology in a population with intermediate gastric cancer risk. Chinese patients aged 35-70 years undergoing diagnostic gastroscopy (GIF FQ260Z) by six experienced endoscopists were enrolled prospectively. The sequence of endoscopic evaluation was WLE followed by NBI. Focal lesions were re-examined by NBI-ME. The incremental diagnostic yield of NBI over WLE and ability of NBI-ME to differentiate gastric mucosal pathology were analyzed. Over a 30-month period, 458 patients (mean age: 52 years; men: 53.7%; Helicobacter pylori positive: 20.1%) were recruited. WLE detected a focal gastric lesion in 43.7% (200/458). WLE made a definitive diagnosis in 148 out of 200 patients (147 benign lesions and one gastric cancer), whereas NBI-ME correctly clarified the nature of the remaining 52 lesions (benign: 51; EGC: one). NBI detected an additional 69 out of 458 lesions (type 0_IIa: 91.3%; type 0_IIb: 8.7%) missed by WLE; the diagnoses based on NBI-ME were IM (67/69), EGC (1/69), and benign lesion (1/69). Interobserver agreement study revealed a κ statistic of 0.71. NBI detected IM missed by WLE. NBI-ME was useful in differentiating the pathology of focal gastric mucosal lesions.
    European journal of gastroenterology & hepatology 12/2011; 24(4):362-7. DOI:10.1097/MEG.0b013e3283500968 · 2.15 Impact Factor
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    ABSTRACT: Abstract Introduction: We developed a new offset-tip papillotome to facilitate biliary cannulation and reduce the incidence of unintended contrast injection into the pancreatic duct during ERCP. The aim of the present retrospective cohort study was to evaluate the utility of the novel offset-tip papillotome in achievement of biliary cannulation, and prevention of unintended contrast injection into the pancreatic duct during ERCP, compared with a standard straight-tip catheter. Material and methods: Patients with native papilla who required biliary ERCP were retrospectively reviewed. Biliary ERCPs were performed by two experienced endoscopists using either the offset-tip papillotome or a standard catheter. Patients in whom ERCP involved fellows in training were excluded. Results: Eighty-five patients were included and divided into two cohorts: The offset-tip papillotome (OT; n = 40) and the standard straight-tip cohort (ST; n = 45). Biliary cannulation success rates in OT and ST cohort were 92.5% and 88.9%, respectively. The frequency of unintended contrast injection into the pancreatic duct and time to biliary cannulation of the OT cohort during biliary cannulation were significantly less than those of the ST cohort (0.56 vs. 1.65 times and 103.3 vs. 287.9 seconds). Conclusion: The novel offset-tip papillotome could reduce the incidence of unintended contrast injection into the pancreatic duct and the time to biliary cannulation.
    Minimally invasive therapy & allied technologies: MITAT: official journal of the Society for Minimally Invasive Therapy 11/2011; 21(5):335-41. DOI:10.3109/13645706.2011.635659 · 1.18 Impact Factor
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    ABSTRACT: A novel multibending backward-oblique viewing duodenoscope was developed to overcome the difficult technical aspect of deep cannulation into the bile duct during endoscopic retrograde cholangiopancreatography (ERCP). The aim of the present study was to evaluate the initial experience of a novel multibending backward-oblique viewing duodenoscope (M-D scope) for ERCP. This was a retrospective review of 23 patients with native papilla who received biliary ERCP with the M-D scope between April and December 2010. The procedures were performed by two well-experienced endoscopists. In all patients, biliary cannulation and therapeutic procedure were successfully completed. In two patients with Billroth I gastrectomy, ERCP were initially attempted with a conventional single-bending duodenoscope, but biliary cannulations were unsuccessful. However, with the use of the M-D scope, biliary cannulation and therapeutic procedures were successfully completed. A novel multibending backward-oblique viewing duodenoscope is safe and feasible for therapeutic and diagnostic ERCP.
    Endoscopy 11/2011; 44(1):99-102. DOI:10.1055/s-0031-1291445 · 5.20 Impact Factor
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    ABSTRACT: Cough and laryngo-pharyngeal symptoms (LPS) are associated with gastroesophageal reflux disease (GERD). The role of acid reflux (AR) and non-acid reflux (NAR) in atypical GERD pathogenesis is controversial. The aims of the study were to determine the prevalence of high esophageal acid exposure time (AET) in patients presenting with cough or LPS and determine the incremental yield of multichannel intraluminal impedance-pH (MII-pH) monitoring. We undertook a prospective study of patients with cough or LPS referred for GERD evaluation between January 2009 and May 2011. All patients underwent esophageal manometry, gastroscopy and MII-pH. Patients' characteristics, gastroscopy findings, distal esophageal AET, bolus exposure (BE) time and numbers of AR and NAR episodes in the proximal and distal esophagus were studied. Overall 50 patients (22 male, mean age 47.5 ± 14.2 years) were evaluated for unexplained chronic cough (n = 23, 46.0%), and LPS symptoms including globus (n = 10, 20.0%), sore throat (n = 12, 24.0%) and hoarse voice (n = 5, 10.0%). A normal gastroscopy, Los Angeles grade A and B esophagitis occurred in 44 (88.0%), 5 (10.0%) and 1 (2.0%) patient, respectively. Seven (14.0%) recorded elevated AET (chronic cough, 4; sore throat, 2; and hoarse voice, 1). Nine patients recorded abnormal impedance characteristics (raised BE time and/or increased reflux numbers) despite a normal AET leading to an incremental diagnostic yield of 18%. An isolated high AET is uncommon in patients with cough or LPS. Combined MII-pH improves the diagnostic yield in patients with atypical GERD manifestations.
    Journal of Digestive Diseases 10/2011; 12(5):341-8. DOI:10.1111/j.1751-2980.2011.00519.x · 1.92 Impact Factor
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    ABSTRACT: The aim of the Endoscopic Retrograde Cholangiopancreatography (ERCP) Working Group was to examine the issues of training, credentialing and quality control in ERCP in Singapore. Published guidelines and clinical trials concerning issues of training, complications and quality control in ERCP have been reviewed. The Working Group recommended that a trainee reach a minimum threshold of 200 cases before the assessment of competency. The target for achievement of competency was set at an 85 percent successful cannulation rate for native papilla. To perform advanced ERCP, endoscopists should have undergone dedicated training either in a recognised training centre or in conjunction with and under the guidance of a more experienced colleague, until technical competency is achieved. Precut should only be performed by endoscopists with experience and expertise in performing Levels II and III ERCP, who have been formally proctored. An audit of ERCP should examine parameters such as appropriate indication, success rates of selective cannulation, technical success rate of commonly performed procedures and procedure-related complications. To maintain technical competency, an individual should be performing ERCP on a regular basis. In conclusion, the innate risks of ERCP necessitate that all ERCP practitioners should be appropriately trained, practise within their expertise level and maintain regular practice in order to minimise risks and improve patient outcome.
    Singapore medical journal 09/2011; 52(9):654-7. · 0.63 Impact Factor
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    Journal of Digestive Diseases 06/2011; 12(3):226-8. DOI:10.1111/j.1751-2980.2011.00501.x · 1.92 Impact Factor
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    ABSTRACT: Traditionally, either surgical or percutaneous drainage is recommended for liver abscess. Recently, several endoscopists have reported the endoscopic ultrasound (EUS)-guided liver abscess drainage. Herein, we report a case of tuberculous liver abscess in which endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) was useful for the diagnosis and therapy. A 78-year-old woman suffered from continuous epigastric pain and fever up. Computed tomography (CT) showed a 70 mm multilocular and multiseptate cystic lesion around the head of pancreas and caudate lobe of the liver. After confirming liver abscess by EUS-FNA, EUS-guided liver abscess drainage was carried out. Finally, a 7 Fr straight stent and a 5 Fr nasocystic catheter were inserted into the cyst. Four weeks later, we found that cultured microorganism obtained using drainage catheter was Mycobacterium tuberculosis. Although he was doing well during 5 days after the procedure, CT showed the size of another abscess increased. Then, additional EUS-guided abscess drainage was carried out at the body of the stomach into the abscess of the left lobe. Two weeks later, CT showed disappearance of abscesses. Then, she discharged with the internal stent still in place.
    Digestive Endoscopy 05/2011; 23 Suppl 1:158-61. DOI:10.1111/j.1443-1661.2011.01115.x · 1.99 Impact Factor
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    ABSTRACT: AIM: Contrast harmonic endosonography (CHEUS) is not widely available. This study assessed the utility of CHEUS using DEFINITY™, a second generation ultrasonic contrast agent, in the evaluation of suspected pancreatic and peri-ampullary malignancies. METHODS: Prospectively enrolled patients with suspected pancreatic and peri-ampullary malignancies underwent EUS followed by CHEUS. The incremental yield of CHEUS over EUS was analyzed. The gold standard for diagnosis of malignancy was positive cytology or histology; a negative diagnosis for malignancy was based on negative cytology or histology and benign clinical course. RESULTS: Twenty-nine patients were enrolled and underwent CHEUS. The final diagnoses were: pancreatic adenocarcinoma (16/29); metastases to pancreas (4/29); pancreatitis with inflammatory mass (4/29); normal pancreas with focal fat sparing (1/29); ampulla adenocarcinoma (2/29); serous cystic neoplasm (1/29); peri-pancreatic lymph node due to lymphoma (1/29). One bengin case of chronic pancreatitis had calcification casting artifacts that prevented accurate EUS examination and was excluded, leaving 28 cases for comparative analysis between EUS and CHEUS. CHEUS enhanced tumor margins. CHEUS detected vascular invasion missed by EUS in 2/16 patients with pancreatic adenocarcinoma. Masses appeared hypoechoic with EUS. With CHEUS malignant masses had an inhomogeneous hypoechoic pattern associated with abnormal vessels while lesions due to focal pancreatitis or fat sparing were characterized by diffuse enhancement (p<0.001). CONCLUSION: CHEUS improved the visualization of tumor margins and vascular invasion, and differentiated benign from malignant masses.
    04/2011; 1(4):160-165. DOI:10.4161/jig.19958
  • Gastrointestinal Endoscopy 04/2011; 73(4). DOI:10.1016/j.gie.2011.03.391 · 4.90 Impact Factor
  • Gastrointestinal Endoscopy 04/2011; 73(4). DOI:10.1016/j.gie.2011.03.930 · 4.90 Impact Factor
  • Kwong Ming Fock, Tiing Leong Ang
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    ABSTRACT: Barrett's esophagus (BE) is defined as a metaplastic change of the distal esophageal epithelium from squamous to columnar type epithelium with the presence of intestinal metaplasia. There is a striking geographic variation in the prevalence rates of BE. Most epidemiological data on BE are derived from patients undergoing endoscopy and do not reflect prevalence rates in the general population. BE is much more common in the West when compared with Asia and Africa. Although BE is less common in Asia, the demographics are similar to the West, being predominantly found in older men with longer duration of reflux symptoms. Some studies from the West have suggested an increase in prevalence rates of BE. An increase in prevalence rates will have significant implications for health resource utilization and costs, due to the small but significant risk of developing esophageal adenocarcinoma. Endoscopic surveillance with the aim of detecting early lesions has been advocated. Compared with conventional white-light endoscopy with blind four-quadrant biopsies, the use of image-enhanced endoscopy, including chromoendoscopy, may improve detection of subtle mucosal irregularities and facilitate targeted biopsies. However, a truly cost-effective surveillance strategy remains to be determined.
    Expert review of gastroenterology & hepatology 02/2011; 5(1):123-30. DOI:10.1586/egh.10.82 · 2.55 Impact Factor
  • Stefan Seewald, Tiing Leong Ang, Nib Soehendra
    Techniques in Gastrointestinal Endoscopy 01/2011; 13(1):50-52. DOI:10.1016/j.tgie.2011.02.019
  • Gastroenterology 01/2011; 140(5). DOI:10.1016/S0016-5085(11)61009-3 · 13.93 Impact Factor
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    Tiing Leong Ang
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    ABSTRACT: An obstructed biliary system is usually drained by endoscopic retrograde cholangiopancreatography, and when this is unsuccessful, the standard alternative technique is percutaneous transhepatic biliary drainage. Surgical biliary bypass may also be required. In recent years, endosonography has transformed from a solely diagnostic procedure to one with therapeutic capabilities. Endosonography-guided biliary drainage is now being performed as an alternative to percutaneous transhepatic biliary drainage. This is an evolving field, with challenges that must be addressed before it can become a routine clinical practice. This review summarises the current status of endosonography-guided biliary drainage.
    Singapore medical journal 10/2010; 51(10):762-6. · 0.63 Impact Factor

Publication Stats

1k Citations
639.19 Total Impact Points

Institutions

  • 2002–2015
    • Changi General Hospital
      • Department of Gastroenterology
      Tumasik, Singapore
  • 2011–2014
    • The Jikei University School of Medicine
      • Department of Endoscopy
      Edo, Tōkyō, Japan
  • 2008
    • University of Fukui
      Hukui, Fukui, Japan
  • 2006–2008
    • University Medical Center Hamburg - Eppendorf
      • Department of Interdisciplinary Endoscopy
      Hamburg, Hamburg, Germany