A miniature horse, colic, and a large obstruction that evaded imaging

A 20-year-old miniature horse presenting with colic was found to have three separate intestinal obstructions during emergency exploratory surgery at the University of California, Davis Large Animal Hospital, including one that was completely undetectable on diagnostic imaging. The obstructions were identified as trichobezoars, masses formed from ingested material such as hair that accumulates in the gastrointestinal tract.

According to UC Davis, the largest trichobezoar was not visible on radiographs because it lacked a mineralized outer layer and was composed primarily of compacted, chewed hair,¹ a material that is typically radiolucent on standard radiographs.² Bezoars such as these can be particularly challenging to detect on routine imaging because they may resemble normal intestinal contents rather than discrete foreign bodies.²

The patient, named Big Chief, spent 5 days at UC Davis after a worsening episode of colic that did not respond to medication.

According to UC Davis, the gelding’s owners, Laura Croyle and her husband, Warren, found Big Chief on the ground in severe distress one morning 4 months ago. “Big Chief was on the ground, obviously in a lot of pain,” Laura said in a UC Davis report.¹ “He was upside down and not even rolling around. It was as if he’d given up.”

Although Big Chief had a history of mild colic that typically responded to medication, this episode progressed despite treatment. His primary veterinarian referred him for advanced care at the UC Davis Large Animal Hospital where Sandra Valdez, DVM, DACVS, DABVP (Equine), and equine surgery resident David Orozco-Lopez, DVM, led the case.

Upon admission, Big Chief underwent a full diagnostic evaluation, including physical examination, bloodwork, nasogastric intubation, and abdominal ultrasonography and radiographs. According to UC Davis, the abdominal radiographs showed 2 intra-abdominal structures, though neither displayed the mineral opacity commonly seen with enteroliths.

Because Big Chief’s abdominal pain appeared to subside, the team initially considered performing a computed tomography (CT) scan to better characterize the mass structures before undergoing surgery the next day. He was admitted to the intensive care unit for close monitoring and intravenous fluids.

Overnight, however, Big Chief’s condition worsened.

By morning, increasing pain and clinical decline led the team to proceed directly to exploratory abdominal surgery and skip advanced imaging.

Under general anesthesia, Valdez and Orozco-Lopez found a large colon obstruction caused by 3 trichobezoars lodged in the large colon. Two corresponded to the structures seen on abdominal radiographs. The third—and largest—had gone undetected.

That mass completely blocked the entire intestinal lumen, UC Davis reported. Unlike typical enteroliths, it lacked a mineralized exterior and consisted primarily of densely compacted, chewed hair, rendering it invisible on imaging.

Bezoars like these can be especially difficult to detect on abdominal radiographs and ultrasonography, where they may resemble normal intestinal contents. Although bezoars have been more extensively studied in human medicine than on the veterinary side, research in human medicine may help explain why these masses can evade routine detection.²

When visible on radiographs and ultrasonography, bezoars may appear as poorly defined, radiolucent or heterogeneous material with acoustic shadowing inconsistently present.² In published studies, typical bezoar features were visible on radiographs in fewer than 1 in 5 cases in cats and dogs, and ultrasound findings were confirmed surgically only about half the time.2 Variability in bezoar composition, imaging protocols, and species differences may further limit reliable identification.²

Two of the masses found in Big Chief were irregularly shaped, measuring 7 × 7 × 12 cm and 3 × 2 × 6 cm. The third was more rounded and approximately 5 cm in diameter.

“These gastrointestinal blockages are caused by an accumulation of ingested hair (often from chewing tails or manes), sand, rocks, or other minerals from the ground,” wrote UC Davis.¹

All 3 trichobezoars were removed through a large colon enterotomy, consisting of a surgical incision into the large intestine. According to UC Davis, Big Chief recovered without complications from anesthesia and was managed post-operatively with intravenous fluids, antibiotics, anti-inflammatories, and analgesics. As his condition improved, treatments were gradually tapered. He was discharged with a strong appetite, normal manure production, and a prognosis for a full recovery.

“I couldn’t believe the size of the largest one,” Croyle said of the trichobezoars.¹ “That might not have made much of an impact for a larger horse, but for a mini—no wonder he was so uncomfortable.”

Recovery from colic surgery typically requires adhering to a “strict” 3-month routine, according to UC Davis.¹

“In the first month, they should be kept on strict stall rest with twice daily hand walks for 10 minutes. During the second month, they are allowed to access a small run in addition to stall rest and hand walks. Finally, in the third month, they are granted access to a large pasture,” UC Davis wrote.¹

The Croyles said Big Chief’s recovery “couldn’t have been better,” and he is back with his herd mates, who are happy their friend is back to normal.

References

1. Warren R. Colic Surgery Required to Remove Three Intestinal Obstructions from Mini Horse. University of California, Davis School of Veterinary Medicine. February 24, 2026. Accessed February 25, 2026. https://www.vetmed.ucdavis.edu/news/colic-surgery-required-remove-three-intestinal-obstructions-mini-horse
2. Koo J, Eom K, Kim J, et al. Computed tomographic features of bezoars and other gastrointestinal foreign bodies in dogs and cats: a comparative analysis. Animals (Basel). 2025;15(9):1260. doi:10.3390/ani15091260.