Consultant in Internal Medicine

Head of the Internal Medicine Department


  • EBVS® European Veterinary Specialist in Small Animal Internal Medicine
  • RCVS Specialist in Small Animal Medicine
  • DMV
  • DipECVIM-CA (Internal Medicine)

Guillaume graduated from the Ecole Nationale Vétérinaire d’Alfort, near Paris, in 2009. He then completed a small animal rotating internship followed by 3 years as a medicine clinician in the same school, during which he obtained the French certificate of advanced practice in small animal Internal Medicine (CEAV-MI). After that, he worked in first opinion and private referral centres for a year before moving to the UK to undergo a residency at Langford Vets – University of Bristol. He became an EBVS® European Veterinary Specialist in Small Animal Internal Medicine in 2018 and an RCVS Recognised Specialist in 2020. Guillaume joined Highcroft Veterinary Referrals (now BVS) in April 2018.

He enjoys all aspects of Internal Medicine but has a particular interest in gastroenterology and endoscopic procedures and is a member of the European Society of Comparative Gastroenterology (ESCG). Guillaume is a ‘Cat advocate’ at BVS and works with the team to ensure that we provide the best possible care and stress-free environment to our feline patients, following the recommendations and guidelines of the International Cat Care.

Publications and research:

  • G. Ruiz, M. Day, I. Doran, A. Major, S. Warman. Polypoid cystitis in a male entire Springer Spaniel puppy. Vet Record Case Reports 2018 6:e000532
  • S. Keegan, G. Ruiz, M. Day, T. Cogan, F.-X. Liebel. Pyogranulomatous meningoencephalitis in a dog. Vet Record Case Reports 2017 5:e000521
  • G. Ruiz, L. Verrot, E. Laloy, G. Benchekroun. Diagnostic contribution of cytological specimens obtained from biopsies during gastrointestinal endoscopy in dogs and cats. JSAP 2017 58(1): 17-22
  • G. Ruiz, G. Benchekroun. What is your diagnosis? Tracheal inflammatory granuloma in a cat. JAVMA 2016 248 (9): 995-997
  • G. Ruiz, E. Reyes-Gomez, E. Hall, V. Freiche. Comparison of 3 handling techniques for endoscopically obtained gastric and duodenal biopsy specimens: a prospective study in dogs and cats. JVIM 2016 30(4): 1014-1021
  • G. Ruiz, E. Reyes-Gomez, L. Colliard. Exceptionally long-term survival of a dog with gastric lymphoma and concurrent dietary intolerance. Vet Record Case Reports 2015 3: 1-5
  • G. Ruiz, E. Laloy, G. Benchekroun. Chronic gastritis and enterocolitis associated with Leishmania infection in an 18-month-old, intact female dog. Vet Quarterly 2015 35(4): 236-239
  • G. Ruiz, A. Decambron, M. Manassero. Nasopharyngeal stenosis treated using a balloon dilatation in a cat. Revue Vétérinaire Clinique 2014 49: 81-86
  1. Ruiz, C. Maurey. A case of Systemic Lupus Erythematosus in a cat. PMCAC 2012, 47(2): 63-64

Services we offer

Our team of Consultants provide top-quality care in anaesthesia & analgesia, cardiology, dentistry, dermatology, diagnostic imaging, emergency and critical care, internal medicine, neurology and neurosurgery, oncology (including radiotherapy), ophthalmology, orthopaedic and soft tissue surgery.


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Anaesthesia and Analgesia

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Dentistry Icon


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Diagnostic Imaging

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Emergency and Critical Care

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Internal Medicine

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Interventional Radiology

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Neurology and Neurosurgery

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Orthopaedics Icon


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Soft Tissue Surgery