Guillaume (Guy) Cornelis Maria Grinwis joined the Pathology division of the Biomolecular Health Sciences department of the Veterinary faculty at the Utrecht University in October 1990 after he had been working as a relief veterinary practitioner in several companion animal clinics in the Netherlands.

At the Pathobiology department he specialized in veterinary pathology, leading to certification as a veterinary pathologist by the Royal Netherlands Veterinary Association (KNMvD) in September 1995.

His PhD research into health effects of some major aquatic pollutants in European flounder was performed in cooperation with the Dutch National Institute for Coastal and Marine Management (RIKZ) (now Deltares) and the Dutch National Institute for Public Health and the Environment (RIVM) which led to his PhD graduation in May 2006.

He is currently employed as a senior veterinary pathologist at the department of Pathobiology, and is involved in the veterinary pathology diagnostic service of the department (VPDC), and in teaching veterinary students and post-graduate training of residents in veterinary pathology and residents in clinical veterinary sciences (e.g. internal medicine, oncology and ophthalmology).

In diagnostics he has special interest in ocular pathology and liver pathology.

He is also regularly assigned by public prosecutors to perform autopsy on a variety of animals species in forensic cases (forensic animal pathology).

Furthermore he participates in research projects within the strategic theme of Life Sciences (Regenerative Medicine & Stem Cells) in the fields of liver disease, pathologies of the intervertebral disc in dogs and tumors of endocrine organs.