A Tall Order: Texas A&M Vet Removes Massive Kidney Tumor From Horse

Story by Michaela Dunn, VMBS Marketing & Communications

February 18, 2026

Sergio, a 1,200-pound warmblood, is hard to miss, not only for his size but also for his playfulness and what his owner, Caitlyn Vaughn, describes as a “Fabio” vibe.

“He’s so sweet and lovey-dovey, it’s almost like having a golden retriever,” Vaughn said. “Every time I drive up to the barn, he’s at the back of the paddock, and as soon as he sees me, he whinnies and runs to the gate to greet me.”

But beneath Sergio’s friendly, larger-than-life personality was a serious and unexpected condition — an approximately 30-pound tumor growing on his left kidney.

After Sergio’s diagnosis, he was brought to the Texas A&M Large Animal Teaching Hospital (LATH), where Dr. Dustin Major, a clinical assistant professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences, performed a highly complex surgery using specialized techniques to remove the tumor and send Sergio back to the barn — ready to greet everyone with his signature enthusiasm.

A Big Personality, A Bigger Problem

Sergio was originally raised and competed as a high-level dressage horse before joining Vaughn’s family, where he transitioned into an all-around horse.

“He’s half Friesian and half Morgan, very social, intelligent and affectionate,” Vaughn said. “He has been a trail horse, a dressage horse, and has even participated in rodeos.”

Sergio had been a solid horse for years, showing no outward signs of illness. But after he colicked twice in a short period of time, Vaughn’s local veterinarian discovered a large mass on his kidney.

“My vet said, ‘I can tell he is in pain now; you’re going to have to make a decision to try something, try to do the surgery, or he’s not going to make it,’” Vaughn said. “She recommended Dr. Major at Texas A&M because he’s the most experienced person with this kind of surgery and even wrote the textbook for equestrian kidney surgery.”

Sizing Up The Situation

When Sergio arrived at the LATH, the Equine Soft Tissue Surgery team quickly assessed the problem.

“On ultrasound, we could see normal kidney tissue that then transitioned into this giant tumor that was on the back of his left kidney,” Major said. “It was so big that it was sort of crossing over his midline and against his aorta. Our biggest concern was whether it was adhered to something we couldn’t safely separate in surgery.”

Given the tumor’s size and location, the surgical team had to carefully consider how to approach the procedure.

“We planned a hand-assisted laparoscopic surgery, or a minimally invasive technique that uses small incisions and a camera to guide surgical instruments and allow introduction of a hand into the abdomen through a larger incision with the horse standing,” Major said. “We perform laparoscopy often, but it’s unusual to need to work inside the abdomen by hand.”

A Major Operation

Once the surgery began, the scale of the challenge became even more apparent.

“Immediately when I got in the abdomen, what we felt before just did not do justice to how big that tumor was,” Major said. “It measured about 30 centimeters (almost 12 inches) in diameter — larger than a basketball.”

To remove the kidney and its associated tumor, the team carefully separated the kidney from its blood supply and surrounding tissues and then placed it in a sterile bag inside the abdmomen so that it could be safely extracted from the horse’s body. Because the tumor was too large to remove intact, the surgeons removed it piece by piece from inside the bag.

After the surgery was complete, the biopsies came back as a renal carcinoma of papillary subtype, a type of kidney cancer that forms in glandular tissue.

“Most horses with this type of kidney tumor have a poor prognosis because it’s usually already spread,” Major said. “We didn’t see any evidence that it had spread, and the fact that it was a papillary subtype, which is less aggressive, was in our favor.”

Sergio’s tumor was an unusual discovery because he showed no kidney-related symptoms and his blood work was normal.

“It’s lucky that he colicked and the tumor was found,” Major said. “Most horses don’t have any reason to suspect a kidney tumor until later, when it has already spread.”

After surgery, Sergio was monitored closely for 24 to 48 hours.

Riding Toward Recovery

After a short hospital stay, Sergio returned home on a carefully managed rehabilitation plan.

“I just can’t believe how well the surgery went in general,” Vaughn said. “Dr. Major called me after the surgery and was like, ‘This was the most complicated surgery we’ve had in a long time, and it went almost perfectly.’”

With time and careful management, Vaughn was able to begin riding Sergio again.

“I had somebody taking him out twice a day for little walks, giving him treats, loving on him, and slowly working him back into shape,” Vaughn said. “After eight weeks, I jumped on him, and he’s back to normal — just perfectly sound again and great. He worked back into trotting and then cantering, and we just had our first jumping lesson this week.

“I felt really good sending him to A&M, from not only an expenses perspective but also the communication and the veterinary students learning and providing care around the clock,” she said. “I am so glad that we ended up following through with the surgery because he’s so happy, he’s so energetic, he loves everybody, and he’s our barn favorite.”

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For more information about the Texas A&M College of Veterinary Medicine & Biomedical Sciences, please visit our website at vetmed.tamu.edu or join us on Facebook, Instagram, and X.

Contact Information: Jennifer Gauntt, Director of VMBS Communications, Texas A&M College of Veterinary Medicine & Biomedical Sciences, jgauntt@cvm.tamu.edu, 979-862-4216

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