During my specialist medical training in gastroenterology I was awarded a Wellcome Trust doctoral Clinical Training Fellowship in 1999 to examine the mucosal immune response to the gut infection. I was awarded The Digestive Disease Foundation (CORE) National Research Prize for this work. Since my appointment at St George’s in 2002, I have expanded my research portfolio with funding from the Wellcome Trust, Medical Research Council, Crohn’s and Colitis UK and the UK Clinical Research Network. I was appointed Professor of Practice in Gastroenterology and Gastrointestinal Infection at St George’s University of London in 2020.

My research is primarily focused on IBD and GI infection with over 100 peer reviewed publications, many appear in high impact international journals such as the Lancet, JAMA, Gastroenterology and Gut.

I have been Principal Investigator  of more than 30 clinical research studies working with the team at  St George’s Clinical Research Facility

I lead international collaborations with NHS and academic partners including Imperial College London, Leeds University and  Christian Medical College, Vellore, India. The impact of my work has grown as  evidenced by more than 2000 citations of my work in the literature and its translation into clinical guidelines. My academic work includes  supervision and mentoring my team of  MD/PhD research fellows.

Alongside my research activity, I am a full time NHS clinician, with activities including out-patient and in-patient consultation, endoscopy, service development and education. I was Clinical Director of Specialist Medicine at  St George’s University Hospitals NHS Foundation Trust between 2008 and 2011 including a portfolio for education and research.

I now lead the  South London Gastroenterology Clinical Research Network and I am a member of the national Gastroenterology CRN committee overseeing a portfolio of commercial- and non-commercial- clinical trials. In this role I have driven recruitment to clinical studies in Gastroenterology, which has more than doubled regionally in the past 5 years

The three major themes to my research portfolio are:

(1) The study of health related outcomes in IBD and GI infection. This includes national studies evaluating the health burden of Clostridium difficile infection in IBD. I am currently leading collaboration with researchers at Imperial College London examining long-term surgical outcomes and prescribing patterns in IBD patients studying an IBD population cohort over 20 years using a UK national dataset. More recently we have evaluated the impact of depression on patients with IBD. Since 2008 our group has published many highly cited original articles in the field of IBD epidemiology and recently published in the top journal in the field Gut.

(2) Non-invasive techniques in the diagnosis and assessment of IBD and GI infection. Successful projects include an evaluation of the role of proteomics technology in the diagnosis of Tuberculosis and IBD, in collaboration with Professor Krishna at SGUL, we published our findings in the Lancet. We have also evaluated novel ultrasound techniques, in collaboration with the Radiology team at St George’s University Hospitals NHS Foundation Trust , for in the diagnosis and assessment of IBD.

(3) Clinical observational and therapeutic studies . We have recruited more than 1000 patients to a range of studies outlined below. Examples include recruitment of patients to the international IBD genetics consortium contributing to a recent paper published in JAMA on rare genetic determinants of IBD. HALT-IT is a large international NIHR-funded trial of a treatment for bleeding in the stomach and small bowel-or work was recently published in the Lancet. I have been instrumental in enterprise development and was awarded 2 NHS innovation awards for development of proteomic–based diagnostic methods and a novel endoscopic device.

I enjoy a wide range of teaching and educational activities at St George’s including Final year medical examination and interviewing prospective medical students. As director for the Early Years clinical Experience (EYCE) Undergraduate Medicine course I led the development and inception of this course for 1^st and 2nd years devised to provide an experience of the clinical milieu in the early years of medical training.

selected publications

Louis E, Resche-Rigon M, Laharie D, Satsangi J, Ding N, Siegmund B, D’Haens G, Picon L, Bossuyt P, Vuitton L, Irving P, Viennot S, Lamb CA, Pollok R, Baert F, Nachury M, Fumery M, Gilletta C, Almer S, Ben-Horin S, Bouhnik Y, Colombel JF, Hertervig E; GETAID and the SPARE-Biocycle research group. Withdrawal of infliximab or concomitant immunosuppressant therapy in patients with Crohn’s disease on combination therapy (SPARE): a multicentre, open-label, randomised controlled trial. Lancet Gastroenterol Hepatol. 2023 Jan 11:S2468-1253(22)00385-5. doi: 10.1016/S2468-1253(22)00385-5. Epub ahead of print. PMID: 36640794.

Jayasooriya N, Baillie S, Blackwell J, Bottle A, Petersen I, Creese H, Saxena S, Pollok RC; POP-IBD study group. Systematic review with meta-analysis: Time to diagnosis and the impact of delayed diagnosis on clinical outcomes in inflammatory bowel disease. Aliment Pharmacol Ther. 2023 Jan 10. doi: 10.1111/apt.17370. Epub ahead of print. PMID: 36627691.

Liu Z, Le K, Zhou X, Alexander JL, Lin S, Bewshea C, Chanchlani N, Nice R, McDonald TJ, Lamb CA, Sebastian S, Kok K, Lees CW, Hart AL, Pollok RC, Boyton RJ, Altmann DM, Pollock KM, Goodhand JR, Kennedy NA, Ahmad T, Powell N; CLARITY study investigators. Neutralising antibody potency against SARS-CoV-2 wild-type and omicron BA.1 and BA.4/5 variants in patients with inflammatory bowel disease treated with infliximab and vedolizumab after three doses of COVID-19 vaccine (CLARITY IBD): an analysis of a prospective multicentre cohort study. Lancet Gastroenterol Hepatol. 2023 Feb;8(2):145-156. doi: 10.1016/S2468-1253(22)00389-2. Epub 2022 Dec 5. PMID: 36481043; PMCID: PMC9757903.

Chanchlani N et al. IMSAT study investigators. Implications for sequencing of biologic therapy and choice of second anti-TNF in patients with inflammatory bowel disease: results from the IMmunogenicity to Second Anti-TNF therapy (IMSAT) therapeutic drug monitoring study. Aliment Pharmacol Ther. 2022 Oct;56(8):1250-1263. doi: 10.1111/apt.17170. Epub 2022 Aug 29. PMID: 36039036; PMCID: PMC9804266.

Kumar S, Pollok R, Muscat I, Planche T. Diagnosis and outcome of Clostridium difficile infection by toxin enzyme immunoassay and PCR in an island population. J Gastroenterol Hepatol. 2016 Aug 9. doi: 10.1111/jgh.13504.

Subramanian V, Chatu S, Echterdiek F, Banerjee A, Finlayson C, Pollok RC. Patients with Endoscopically Visible Polypoid Adenomatous Lesions Within the Extent of Ulcerative Colitis Have an Increased Risk of Colorectal Cancer Despite Endoscopic Resection. Dig Dis Sci. 2016 Oct;61(10):3031-6. doi: 10.1007/s10620-016-4246-7. Epub 2016 Jul 12.

Chhaya V, Saxena S, Cecil E, Chatu S, Subramanian V, Curcin V, Majeed A, Pollok RC. The impact of timing and duration of thiopurine treatment on colectomy in ulcerative colitis: a national population-based study of incident cases between 1989-2009. Aliment Pharmacol Ther. 2015 Jan;41(1):87-98.

Chhaya V, Saxena S, Cecil E, Subramanian V, Curcin V, Majeed A, Pollok RC. Impact of Timing and duration of thiopurine treatment on first Perianalsurgery in Crohn’s Disease:UK population-based Study. Inflamm Bowel Dis. 2015 Jan 7

Prescott NJ,..UK IBD Genetics Consortium,..Pollok R  et al.  Pooled sequencing of 531 genes in inflammatory bowel disease identifies an associated rare variant in BTNL2 and implicates other immune related genes. Nature Genetics  2015

Chatu S, Subramanian V, Saxena S, Pollok RC. The role of thiopurines in reducing the need for surgical resection in Crohn’s disease: a systematic review and meta-analysis. Am J Gastroenterol. 2014 Jan;109(1):23-34

Chatu S, Saxena S, Subramanian V, Curcin V, Yadegarfar G, Gunn L, Majeed A, Pollok RC. The Impact of Timing and Duration of Thiopurine Treatment on First Intestinal Resection in Crohn’s Disease: National UK Population-Based Study 1989-2010. Am J Gastroenterol. 2014 Jan 28

Kumar S, Hakim AF, Alexakis CF, Chhaya VF, Tzias DF, Pilcher JF, Pollok RC. Small intestinal contrast ultrasonography for the detection of small bowel complications in Crohn’s disease: correlation with intra-operative findings and MR enterography. Gastroenterology and Hepatology.  2014; 1440-1746

S Chatu, V Chhaya, R Holmes, P Neild, JY Kang, RC Pollok, A Poullis. Factors associated with vitamin D deficiency in a multicultural inflammatory bowel disease cohort. Frontline Gastroenterology  4 (1), 51-56, 2013 4 2013

Chatu S, Pilcher J, Saxena SK, Fry DH, Pollok RC. Diagnostic accuracy of small intestine ultrasonography using an oral contrast agent in Crohn’s disease: Comparative study from the UK.Clin Radiol. 2012 Jun;67(6):553-9.

Assessment of administrative data for evaluating the shifting acquisition of Clostridium difficile infection in England. Jen MH, Saxena S, Bottle A, Pollok R, Holmes A, Aylin P. J Hosp Infect. 2012 Mar; 80(3):229-37. Epub 2012 Feb 4

Meta-analysis: diagnostic medical radiation exposure in inflammatory bowel disease. Chatu S, Subramanian V, Pollok RC. Aliment Pharmacol Ther. 2012 Mar;35(5):529-39. Epub 2012 Jan 13

Diagnostic accuracy of small intestine ultrasonography using an oral contrast agent in Crohn’s disease: Comparative study from the UK. Chatu S, Pilcher J, Saxena SK, Fry DH, Pollok RC. Clin Radiol. 2011 Dec 31.

Acute upper gastrointestinal bleeding: identifying low risk patients. Chakrabarty G, Groves C, Pollok R. Gut. 2011

Increased health burden associated with Clostridium difficile diarrhoea in patients with inflammatory bowel disease. Jen MH, Saxena S, Bottle A, Aylin P, Pollok RC. Aliment Pharmacol Ther. 2011 Jun;33(12):1322-31

Unusual causes of diarrhoea and peripheral oedema. Gayatri Chakrabarty, RCG Pollok, P Mortimer. Gastroenterology Today  2011; 21(1): 18-19

Primary cytomegalovirus infectious colitis complicating Crohn’s disease successfully treated with oral valganciclovir. Subramanian V, Finlayson C, Harrison T, Rice P, Pollok R. J Crohn’s Colitis. 2010; 4:199-202

JF Rahier..Pollok R.. et al. European evidence-based Consensus guidelines on the management of opportunistic infections in inflammatory bowel disease. J Crohn’s and Colitis 2010 Jun;4(2):199-202

Pollok RCG. Treatment of Clostridium difficile. N Engl J Med. 2009 Feb 5;360(6):636

Subramanian V,  Saxena S, Kang JY, and Pollok R. Pre-operative steroid use in patients with Inflammatory Bowel Disease and post-operative complications: meta-analysis. Am J Gatroenterol. . 2008; 103:2373-81.

Subramanian V, Beharry N, Pollok RC. Determining the proximal extent of ulcerative colitis: white cell scan correlates well with histological assessment.  Aliment Pharmacol Ther. 2007 Feb 15;25(4):441-6.

Agranoff D, Fernandez-Reyes D, Papadopoulos M, Rojas S, Herbster M, Loosemore A, Tarelli T, Sheldon J, Schwenk A, Pollok RCG, Rayner C, Krishna S. Identification of diagnostic markers for tuberculosis by serum proteomic fingerprinting. Lancet 2006 Sep 16;368(9540):1012-21.

Subramanian V, Pollok RC, Kang JY, Kumar D. Systematic review of postoperative complications in patients with inflammatory bowel disease treated with immunomodulators.Br J Surg 2006 Jul; 93(7):793-9

Zulu I, Kelly P, Sianongo S, Kaonga K, McDonald V, Farthing M, Pollok RC. Nitazoxanide for persistent diarrhoea in Zambian AIDS patients: a randomised controlled trial. Aliment Pharmacol Ther 2005; 21: 757-763

Irving PM, Alstead EM, Greaves RR, Feakins RM, Pollok RC, Rampton DS. Acute mesenteric infarction: an important cause of abdominal pain in ulcerative colitis. Eur J Gastro Hepatol. 2005 ; 17(12): 1429-1432

RCG Pollok.Investigation of chronic diarrhoea. Gut. 2004 May;53(5):770

JY Kang, A Dhar, R Pollok et al. Diverticular disease of the colon: ethnic differences in frequency. Aliment Pharmacol Ther 2004; 19:765-69

IS Lean, Ac Stuart, M Bajaj-Elliott, RCG Pollok, MJG Farthing, V McDonald. IL-4 and TGF-beta have opposing regulatory effect on interferon–gamma mediated inhibition of Cryptosporidium parvum. Infec  Immun 2003; 71(8): 4580-85

RCG Pollok et al. Interferon-gamma induces enterocyte resistance to infection against the intracellular pathogen Cryptosporidium parvum. Gastroenterology 2001; 120: 99-107

T Blanchard, L Milne, RCG Pollok. Lancet 1994; 343: 922. Clostridium difficile diarrhoea and rifabutin. Early chemotherapy of neuro-schistosomiasis. Lancet  1993; 341: 959. RCG Pollok, R Bendall, A Moody, PL Chiodini, DR Churchill. Traveller’s diarrhoea associated with “Cyanobacterium-like-bodies”.Lancet 1992; 340: 556-557