Diana Hassel

Professor, Equine Emergency and Critical Care Clinical Sciences

JFEH Johnson Equine Hospital

(970) 297-4271

About Diana

Dr. Hassel is a professor of equine emergency surgery and critical care and helped establish the 24/7 equine critical care service at CSU in 2004. She has been a specialist in the area of equine colic since completion of her surgical residency in 1997 and has furthered her background in critical care medicine for the horse by obtaining board certification by the American College of Veterinary Emergency and Critical Care in 2007. Her research interests are focused on treatment of the critically ill equine patient, with particular interests in colic, the equine gastrointestinal microbiome, and endotoxemia.


Ph.D., University of California, Davis, 2003Doctor of Veterinary Medicine, University of California, Davis, 1993Bachelor of Science, University of California, Davis, 1989


Diplomate, American College of Veterinary Surgeons
Diplomate, American College of Veterinary Emergency Critical Care


O’Brien T.J., Pezzanite L.M., Acutt, E.V., Vilander A.C., Hassel D.M., Hector R.C., Hendrickson D.A. Successful surgical removal of a pheochromocytoma in a mare via trans-costal approach. Equine Vet J. 2023 http://doi.org/10.1111/evj.13931 Steward, S.K.; McKee, H.M.; Watson, A.M.; Salman, M.D.; Hassel, D.M*. Transcutaneous Detection of Intramural Microchips for Tracking the Migration of the Equine Large Colon: A Pilot Study. Animals 2022, 12, 3421. https://doi.org/10.3390/ani12233421 Hann, M. J., Mair, T. S., Gardener, A., Southwood, L. L., Dechant, J. E., Barton, M. H., Gacia-Marcias, J., Parker, R. A., Hassel, D. M., Archer, D. C. Acute abdominal dehiscence following laparotomy: a multicentre, international retrospective study. Equine Vet J. 2022;54:719–725.Erwin, S. J., Clark, M. E., Dechant, J. E., Aitken, M. R., Hasssel, D. M., Ziegler, A. L., Blikslager, A. T. Multi- institutional Retrospective Case-control Study Evaluating Clinical Outcomes of Foals with Small Intestinal Strangulating Obstruction, Animals 2021, 11, 3337. https://doi.org/10.3390/ani11123337 Steward S, Hassel DM*, Martin H, Doddman C, Stewart A, Elzer E, Southwood L. Geographic disparities in clinical characteristics of duodenitis/proximal jejunitis in horses in the United States. J Equine Vet Sci 2020; 93:103192.Hassel DM*, Curley T, Hoaglund EL. Evaluation of fecal sand clearance in horses with naturally acquired colonic sand accumulation with a product containing probiotics, prebiotics and psyllium. J Equine Vet Sci 2020 doi: 10.1016/j.jevs.2020.102970Hassel DM*, Fahie M, Lohr C, Halsey R, Vernau W, Gorman E. Inter-institutional collaboration for the development of a local peer observation process to enhance teaching. J Vet Med Educ 2020 Oct;47(5):555-569.Avery AC, Dowers KL, West AB, Graham B, Hellyer PW, Avery PR, Ballweber LR, Hassel DM, Oaks JF, Frye MA. Student, faculty and program outcomes associated with Capstone examinations 2 administered to veterinary students at Colorado State University. J Am Vet Med Assoc 2020;257(2):165-175.Hassel DM*. Editorial: Abstracts for the 1st International Dorothy Havemeyer Foundation Workshop: Focus on Colic. Equine Vet Educ 2019 Dec 10. doi: 10.1111/eve.13211.Bayless RL, Moore AR, Hassel DM, Byer B, Landolt GA, Nout-Lomas YS. Equine urinary N-acetyl-ß-D- glucosaminidase assay validation and correlation with other markers of kidney injury. J Vet Diagn Invest 2019;31(5):688-695.Kunz IG, Reed KJ, Metcalf JL, Hassel DM, Coleman RJ, Hess T, Coleman SJ. Equine fecal microbiota changes associated with anthelmintic administration. J Equine Vet Sci 2019;77:98-106.Applegate TJ, Barrell EA, Hassel DM, Hackett ES, Simpson KM, Callan RJ. Combined tube cystostomy and urethrotomy for the treatment of urethral obstruction due to urolithiasis in goats. Vet Surg 2020;49(2):373-379.Hoaglund EL, Hassel DM*, Hess AM. Effect of intravenous fluid administration on the development of post- operative reflux in horses with colic. J Vet Emerg Crit Care 2018;228(6):566-72.Hoon-Hanks LL, Rout ED, Vap LM, Aboellail TA, Hassel DM, Nout-Lomas YS. Reactive mesothelial hyperplasia associated with chronic peritonitis in a 20-year-old Quarter horse. Canadian Vet J 2016:57(5):492-6.Daniel A, Leise B, Burgess B, Morley P, and Hassel DM. Concentrations of serum amyloid A and plasma fibrinogen in horses undergoing emergency abdominal surgery. J Vet Emerg Crit Care 2016 26(3):344-51.Hassel DM*. Management of abdominal strangulations by mesenteric bands. Equine Vet Educ 2014;26(12):645- 646.Hassel DM*. In vitro comparison of V-Loc™? versus Biosyn™? in a one-layer end-to-end anastomosis of equine jejunum. Vet Surg 2014;43(1):80-4.Nelson BB, Lordan E, Hassel DM*. Risk factors associated with gastrointestinal dysfunction in horses undergoing elective procedures under general anesthesia. Equine Vet J 2013;45:8-14.

Research Specialty

ColicEquine gastrointestinal microbiomeEndotoxemiaCritical care medicine