su teng lau, guo hou loo, shue hong kong, norlaila mustafa, nik ritza kosai.  (2026).  metabolic bariatric surgery versus medical therapy for type 2 diabetes: a 5-year real-world cost and remission analysis.  - obesity surgery.  3777 - 3784. 

wei lun tan, guo hou loo, guhan muthkumaran, nik ritza kosai.  (2026).  long-term weight loss and metabolic outcomes after bariatric surgery in a large asian cohort: a real-world cohort study.  - obesity surgery.  3736 - 3744. 

guo hou loo, meng xian chan, zhun shen tan and nik ritza kosai.  (2026).  giant paraumbilical hernia causing gastric outlet obstruction in a young man with class iii obesity: a case report and literature review.  - frontiers in surgery.  1 - 11. 

jo ann andoy galvan, guo hou loo, nik ritza kosai, chai hong yeong, karuthan chinna, rusli nordin, kenneth kwing-chin lee, norlaila mustafa.  (2026).  long-term clinical outcomes and cost-effectiveness of bariatric surgery for type 2 diabetes in malaysia: a 10-year retrospective cohort study.  - journal of multidisciplinary healthcare.  1 - 12. 

guo hou loo, nik aisyah kosai, val michael villareal, guhan muthukumaran and nik ritza nik mahmood .  (2026).  case report: three contrasting presentations of acute oesophageal necrosis and the determinants of outcome.  - frontiers in medicine.  1 - 11. 

natasia nicole deser, hans alexander mahendran, guo hou loo and nik ritza kosai.  (2026).  prehabilitative parenteral nutrition and surgery-related muscle loss in patients undergoing major upper gastrointestinal surgery: a single-centre observational cohort study.  - frontiers in nutrition.  1 - 10. 

guo hou loo, yin ping wong, nur fa’izah ab muin, kean leong koay, mariyam nahuza, shahrun niza abdullah suhaimi and nik ritza kosai.  (2026).  case report: heterogeneous endoscopic and histological presentations of gastric and gastroesophageal metastases from breast carcinoma: a three-case series from a malaysian tertiary center.  - frontiers in oncology.  1 - 8. 

theeran kaur gill, guo hou loo, guhan muthkumaran, nik ritza kosai.  (2025).  posterior membranous tracheal injury during mckeown oesophagectomy. a case report with literature review..  - frontiers in oncology.  1 - 6. 

wan izzah wan jaffar, guo hou loo, fazarina mohammed, deborah chia hsin chew, guhan muthkumaran and nik ritza kosai.  (2025).  case report: rare case of signet ring gastric adenocarcinoma with rectal metastasis.  - frontiers in oncology.  1 - 6. 

firdaus che ani, guo hou loo, richelle huey bing chua, kok-yong chin, nik ritza kosai.  (2025).  integrating cruroplasty with laparoscopic sleeve gastrectomy: a strategy to mitigate gerd symptoms in obese patients. a randomized control trial.  - langenbeck's archives of surgery.  1 - 7. 

amrit manik nasta, ramen goel, rishi singhal, luc lemmens, sarfaraz baig, yosuke seki, arun prasad, sonja chiappetta, mohammad kermansaravi, marc vertruyen, beniamino pascotto, juan santiago azagra, waleed al-khyatt, gennaro martines, diva y villao, leandro revello, marco rioseco, francesco martini, arnaud liagre, gildas juglard, giovanni dapri, monika a proczko-stepaniak, adel k abou-mrad, hosam m elghadban, christine stier, jasper l van herck, safwan abdulrahman taha, ozan sen, bruno dillemans, stijn van hoef, mathieu vandeputte, sofie viskens, paolo gentileschi, raj palaniappan, nasser sakran, thomas h shin, ali aminian, matteo uccelli, stefano olmi, giovanni c cesana, marco anselmino, nicolas p a debergh, daniel gärtner, wah yang, digvijay s bedi, kamal mahawar, haidar abdalah, hytham hamid, rajesh gianchandani-moorjani, vincenzo bottino, alfonso bosco, errichetta napolitano, ravikrishna mamidanna, brij madhok, débora acín-gándara, manuel medina-garcía, sajith kumar, rajneesh bankenahally, yasmin sarfaraz, heather fry, tom wiggins, krishnamohan yarlagadda, anna popp, tadeja pintar, francesk mulita, georgios-ioannis verras, michail vailas, george skroubis, manish khaitan, giovanni lezoche, urs pfefferkorn, shahab shahabi, amir davarpanah, cunchuan wang, zhiyong dong, amador garcia ruiz de gordejuela, ramón vilallonga, Óscar gonzález, piotr major, piotr zarzycki, justyna rymarowicz, yannick nijs, jaydeep palep, randeep wadhawan, deepa kizhakke veetil, carlos esquivel, manuel garcía, fernando martinez lascano, maría muriel, josé foscarini, fajer nassour, kazunori kasama, agustin duro, sang hyun kim, aatif inam, sharad sharma, radwan kassir, manuel aceves avalos, saeed alsareii, miljana vladimirov, michela campanelli, domenico benavoli, emanuela bianciardi, juan carlos sebastián-tomás, ramón trullenque-juan, josé Ángel díez-ares, octávio viveiros, rui ribeiro, muzaffer al, ahmet gökhan, nikhilesh krishna, bassel haj, ramy gfely, jabra arraf, abdallah omari, ali awad, pranoy gupt, jacques himpens, jonathan super, vasileios charalampakis, markos daskalakis, mohamed sahloul, spyridon kapoulas, arab rawashdeh, kareem sillah, govindan raghuraman, ana garcia navarro, nr kosai, mohd firdaus che ani.  (2024).  30-day morbidity and mortality of revisional bariatric surgery – an international multi-centre collaborative (broad) study.  - obesity research & clinical practice.  195 - 200. 

wei soon pang, guo hou loo, guo jeng tan, mardiana mardan, reynu rajan, & nik ritza kosai.  (2024).  comparative evaluation of early diabetic outcomes in southeast asian patients with type 2 diabetes mellitus undergoing roux-en-y gastric bypass (rygb) verssus sleeve gastrectomy (lsg).  - scientific reports.  1-7. 

jun sen chuah, jih huei tan, mohamad adam bujang, koon khee chan, nik ritza kosai.  (2024).  transcutaneous electric nerve stimulation of acupuncture points improves tolerance in adults undergoing diagnostic upper gastrointestinal endoscopy - a single center, double-blinded, randomized controlled trial.  - surgical endoscopy.  3279 - 3287. 

nik ritza kosai, aishath azna ali, ryan ghita, guhan muthkumaran, ismail ali, guo hou loo, firdaus hayati.  (2024).  one-year outcomes in a supervised program of swallowable intragastric balloon—analysis of 486 patients in a high-volume bariatric centre in malaysia.  - obesity surgery.  3366 - 3371. 

mohamed arif hameed sultan, muhamad hud muhamad zin, firdaus hayati, zulkifli md zainuddin, nik ritza kosai, reynu rajan, zainal adwin zainal abidin, dayang corieza febriany.  (2023).  improvement in erectile dysfunction among male obese patient, following bariatric surgery in hospital canselor tuanku muhriz (hukm).  - obesity surgery.  1506-1518. 

david eng yeow gan, nik ritza kosai nik mahmood, jitt aun chuah, firdaus hayati.  (2023).  performance and diagnostic accuracy of scoring systems in adult patients with suspected appendicitis.  - lagenbeck's archives of surgery.  1-9. 

global surgery, globalsurg collaborative, mustafa mohammed taher, nik ritza kosai, dayang nita abdul aziz, reynu rajan.  (2023).  use of telemedicine for postdischarge assessment of the surgical wound: international cohort study, and systematic review with meta-analysis.  - annals of surgery.  1331-1347. 

nur izreena ismail, khairul najmi muhammad nawawi, deborah chew chia hsin, kok wei hao, nik ritza kosai nik mahmood, gary lee chong chearn, zhiqin wong, azmi mohd tamil, hazel joseph, raja affendi raja ali.  (2023).  probiotic containing lactobacillus reuteri dsm 17648 as an adjunct treatment for helicobacter pylori infection: a randomized, double- blind, placebo- controlled trial.  - helicobacter.  1-11. 

lee qz, nik ritza k, mohd firdaus ca, muhammad m.  (2023).  the impact of laparoscopic intraperitoneal instillation of ropivacaine in enhancing respiratory recovery and reducing acute postoperative pain in laparoscopic sleeve gastrectomy: a double-blinded randomised control; relieve trial.  - obesity surgery.  3141-3146. 

wah-kheong chan, soek-siam tan, siew-pheng chan, yeong-yeh lee, hoi-poh tee, sanjiv m., khean-lee goh, anis safura ramli, feisul m., nik ritza k. dan raja affendi ra.  (2022).  malaysian society of gastroenterology and hepatology consensus statement on metabolic dysfunction-associated fatty liver disease.  - gastroenterology and hepatology.  795-811. 

nik ritza kosai, raja affendi raja ali.  (2022).  global multi-stakeholder endorsement of the mafld definition.  - the lancet gastroenterology and hepatology.  388-390. 

masayuki o, soo min a, yosuke s, wah y, simon kin hw, suthep u, jefrey m. h, manish k, nik ritza k, weu w, june l, reno r, thejana w, edward o.  (2022).  ten years of change in bariatric/metabolic surgery in the asia-pacific region with covid-19 pandemic: ifso-apc national reports 2021.  - obesity surgery.  2994-3004. 

asif sukri, alfizah hanafiah, nik ritza kosai, mustafa mohammed taher, ramelah mohamed.  (2022).  new insight on the role of helicobacter pylori caga in the expression of cell surface antigens with important biological functions in gastric carcinogenesis.  - helicobacter.  1-8. 

raymond zml, hans am, malaysian upper gastrointestinal surgical society (mugis), ng cb, low ky, sekkapan t, ngo cw, nik ritza kosai, reynu r, mohamad as, ahmad sudiman ms, ramesh g, azrina ab, mahadevan dt, vijaya sa, wan najmi wd, lim sy, kelvin v, moha.  (2022).  esophageal squamous cell carcinoma and adenocarcinoma in malaysia - pooled data from upper gastrointestinal centers in a multiethnic asian population.  - cancer epidemiology.  1-8. 

asif sukri, alfizah hanafiah, and nik ritza kosai.  (2022).  the roles of immune cells in gastric cancer: anti-cancer or pro-cancer?.  - cancers.  1-14. 

nur izreena ismail, raja affendi raja ali, zhiqin wong, khairul najmi muhammad nawawi, wei hao kok, nik ritza kosai nik mahmood, chia hsin chew, chong chearn lee, azmi mohd tamil, hazel joseph.  (2022).  the effect of lactobacillus reuteri probiotic as an adjunct treatment for helicobacter pylori infection in adults.  - gut.  1. 

syarifah nafisah al-yahya, muhammad haffiz haslam mohamed akram, kasturi vijaya kumar, siti nor asyrah mat amin, noor alifah abdul malik, nor ain mohd zawawi, nik ritza kosai nik mahmood,norlaila mustafa, mawaddah azman, and marina mat baki.  (2022).  maximum phonation time normative values among malaysians and its relation to body mass index.  - journal of voice.  457-463. 

zahra rashidbenam, mohd hafidzul jasman, guan hee tan, eng hong goh, xeng inn fam, christopher chee kong ho, zulkifli md zainuddin, reynu rajan, rizal abdul rani, fatimah mohd nor, mohamad aznan shuhaili, nik ritza kosai, farrah hani imran, min hwei ng.  (2021).  fabrication of adipose-derived stem cell-based self-assembled scaffold under hypoxia and mechanical stimulation for urethral tissue engineering.  - international journal of molecular sciences.  1-32. 

asif sukri, alfizah hanafiah, noraziah mohamad zin, nik ritza kosai.  (2020).  epidemiology and role of helicobacter pylori virulence factors in gastric cancer carcinogenesis.  - apmis.  150-161. 

jimmy bys, jiafu j, sang uk, masanori t, guoxin li, hh kim, simon l, asim s, kyo ys, woo jh, nik ritza kosai, koji k, kazunari m, hiroshi y, takahiro k, peng cl, young wk, jaideeraj r, bee ct, hk yang, expel study group.  (2020).  extensive peritoneal lavage after curative gastrectomy for gastric cancer study (expel): an international multicenter randomized controlled trial.  - journal of clinical oncology.  279. 

loo guo hou, reynu rajan, azmi mohd tamil, nik ritza kosai.  (2020).  prevalence of obstructive sleep apnea in asian bariatric population: an underdiagnosed dilemma.  - surgery for obesity and related disease.  778-783. 

surita binti said, guo hou loo, nik ritza kosai, reynu rajan, rozita mohd, asrul abdul wahab, shamsul azhar shah.  (2020).  reduction in urinary chemokine (c-c motif) ligand 2 (ccl-2) after surgery-induced weight loss.  - scientific reports.  1-6. 

globalsurg collaborative; dayang nita abdul aziz, reynu rajan, mohammed taher, nik ritza kosai.  (2019).  pooled analysis of who surgical safety checklist use and mortality after emergency laparotomy.  - british journal of surgery.  103-112. 

sivaneswaran lechmiannandan, mayurran panirselvam, prema muninathan, narwani hussin, reynu rajan, hatta sidi, nik ritza kosai & c. rajkumar vinayak.  (2019).  resolution of female sexual dysfunction (fsd) among the obese multiethnic malaysian women now a reality with bariatric surgery: a prospective pilot study in malaysia.  - obesity surgery.  1571-1575. 

mustafa mohammed taher, nik ritza kosai, dayang nita abdul aziz, reynu rajan.  (2018).  surgical site infection after gastrointestinal surgery in high-income, middle-income and low-income countries: a prospective, international, multicentre cohort study.  - lancet infectious disease.  . 

reynu rajan, nik ritza kosai.  (2018).  history and progress of bariatric surgery in malaysia.  - obesity surgery.  . 

kavitha subramaniam, wah-yun low, peng-choong lau, kin-fah chin, karuthan chinna, nik ritza kosai, mustafa mohammed taher, and reynu rajan.  (2018).  eating behaviour predicts weight loss six months after bariatric surgery: a longitudinal study.  - nutrients.  1-13. 

globalsurg collaborative, dayang nita abdul aziz, mustafa mohamed, reynu rajan, nik ritza kosai..  (2018).  management and outcomes following surgery for gastrointestinal typhoid: an international, prospective, multicentre cohort study.  - world journal of surgery.  . 

globalsurg collaborative, nik ritza kosai, mustafa taher, reynu rajan.  (2018).  laparoscopy in management of appendicitis in high-, middle-, and low-income countries: a multicenter, prospective, cohort study.  - surgical endoscopy.  . 

zar chi thent, chiranjib chakraborty, pasuk mahakkanukrauh, nik ritza kosai nik mahmood, reynu rajan and srijit das.  (2017).  the molecular concept of atheromatous plaques.  - current drug targets.  1250-1258. 

w. liew, y. y. wai, n. r. kosai, h. s. gendeh.  (2017).  tackers versus glue mesh fixation: an objective assessment of postoperative acute and chronic pain using inflammatory markers.  - hernia.  549-554. 

asif sukri, alfizah hanafiah, nik ritza kosai, mustafa mohamed taher and isa mohamed rose.  (2016).  surface antigen profiling of helicobacter pylori-infected and -uninfected gastric cancer cells using antibody microarray.  - helicobacter.  417-427. 

a. bhangu, ......, nr kosai, m taher, r rajan.....globalsurg collaborative.  (2016).  mortality of emergency abdominal surgery in high-, middle- and low-income countries.  - british journal of surgery.  971-988. 

m mohd sukri, a hanafiah, n nik mahmood, mmohamed taher, i mohamed rose, r mohamed.  (2016).  distribution of cd antigens in gastric adenocarcinoma cell line infected with different caga genotypes of helicobacter pylori strains.  - helicobacter.  115-116. 

reynu r, zainal za, kosai nr.  (2016).  pre-operative methods to reduce liver volume:a randomised controlled trial comparing the use of omega-3polyunsaturated fatty acid supplements vs vlcd restriction in patients awaiting bariatric surgery.  - obesity surgery.  122-123. 

reynu r, hisham ahk, kosai nr.  (2016).  concurrent minimally invasive repair of ventral hernia during laparoscopic sleeve gastrectomy : a prospective study.  - obesity surgery (ifso).  251. 

reynu r, hilal z, kosai nr.  (2016).  early effect of bariatric surgery on serum renin-aldosterone, blood pressure and weight: a prospective study in obese malaysian population.  - obesity surgery (ifso).  282-283. 

shabbir a, bc tai, lakdawala m, huang ck, praveen raj p, sby jimmy, eng a, lomanto d, cheng ak, rao j, rajan r, delko t, kosai n, k kasama, kow l, wei-jei lee.  (2016).  influence of asian ethnicity on weight loss 3 years following laparoscopic sleeve gastrectomy.  - obesity surgery (ifso).  349. 

mohd firdaus ca, reynu r, kosai nr.  (2016).  the effect of crura reinforcement on gastro-oesophageal reflux disease score following laparoscopic sleeve gastrectomy; a randomised controlled trial.  - obesity surgery (ifso).  550-551. 

elsa jr, reynu r, kosai nr.  (2016).  the effect of laparoscopic bariatric surgery on serum fibrinogen level : a prospective study in obese malaysian population.  - obesity surgery (ifso).  552-553. 

nr kosai, r reynu, at hizami, g tikfu.  (2015).  comparative study between laparoscopic sleeve gastrectomy and laparoscopic banded gastric plication in malaysia.  - obesity surgery (ifso).  324. 

r reynu, nr kosai, a haniffa.  (2015).  predicting diabetes remission following laparoscopic bariatric surgery in morbid obesity: a malaysian experience.  - obesity surgery (ifso).  323-324. 

r reynu, nr kosai, mt mustafa, lakdawala ma.  (2015).  concurrent laparoscopic mesh repair of a morgagni hernia, umbilical hernia and sleeve gastrectomy in a morbidly obese individual.  - obesity surgery (ifso).  322-323. 

kosai nr, levin kb, reynu r, taher mm, ali rar, palaniappan s.  (2015).  snapshot quiz 15/1 (small bowel adenocarcinoma in crohn`s disease).  - british journal of surgery.  4-15. 

r jarmin, z zuhdi, a azman, y yusoff, ac ariffin, nrn kosai, h othman, r rahim.  (2014).  early experience of the lateral approach for laparoscopic splenic preserving distal pancreatectomy.  - hpb ( journal of internation hepato-pancreatico-biliary association).  642. 

razman jarmin, zamri zuhdi, hairol othman, yussra yusoff, affirul chairil ariffin, razrim rahim, azlanuddin azman, nik ritza nik kosai.  (2014).  the management of acute cholecystitis in pregnancy.  - hpb journal.  340. 

thu, y; barakatun nisak, m; chin, y; gee, t; rohana, a; nik, r.  (2014).  comparison study between bariatric surgery and conventional treatment on nutritional status and quality of life among morbidly obese malaysian patients.  - obesity reviews.  15(S2):135.