Case Study: Mustang Filly With Recurrent Colic  

A vet tech walks us through a challenging recurrent colic case that utilized many of her clinical skills.
Young horse colicking, lying down in stall, colic case.
Sometimes, medical treatment cannot fix all problems during a colic case, and surgical intervention might be necessary. | Getty Images

On Oct. 12, 2020, at 2:00 a.m., a 7-month-old Mustang filly was admitted to Comstock Equine Hospital, in Reno, Nevada. The filly, which weighed 250 pounds, presented for management of multiple episodes of colic. Her caretakers reported that she had been down and thrashing with diffuse muscle fasciculations. The patient had received a 250-pound dose of oral flunixin meglumine. 

Upon arrival at the clinic, an associate veterinarian performed a physical examination that revealed the filly to be bright and alert. Although she was comfortable upon arrival, the filly was tachycardic with a heart rate of 60 beats per minute (bpm). Respiratory rate was slightly increased at 20 breaths per minute, and lungs auscultated within normal limits. Mucous membranes were pink with a capillary refill time of 1 second but were also tacky to the touch. Skin turgor was within normal limits at 2 seconds. The filly had a temperature of 100.1 degrees F and was not febrile. Borborygmi was auscultated as increased in the four quadrants. Digital pulses were within normal limits in all four legs. The only indication of discomfort was when the patient pawed during the exam. Her perineum and tail were caked in dried diarrhea. She did not present with any clinical signs of endotoxemia or overt colic upon exam. 

Day 1: Bloodwork and Vitals 

Previously, this patient had been admitted to the clinic five times and underwent several recheck examinations both in the field and at the hospital. During those previous hospitalizations, the filly had been on intravenous (IV) fluid therapy multiple times, received a gastroscope, IV antibiotics, IV pain management, fecal polymerase reaction diarrhea tests, fecal parasite tests, gastroprotectants, multiple deworming protocols, nasogastric lavage and oral fluids, abdominal radiographs, and ultrasounds without a definitive diagnosis for her ongoing colic signs. Coming into this hospitalization, the filly had lost 50 pounds from her first visit. 

Bloodwork indicated a high white blood cell count at 11.18 K/μL (reference range: 4.9-11.1 K/μL) characterized by lymphocytosis at 5.83 K/μL (reference range: 1.5-5.1 K/μL) and monocytosis at 0.62K/μL (reference range: 0.2-0.6 K/μL). It also showed a hypoglycemia at 94 mg/dL (reference range: 109.0-268.0 mg/dL), hypercalcemia at 12 mg/dL (reference range: 9.4-11.8 mg/dL), high aspartate aminotransferase at 308 U/L (referange: high at 208 U/L), low alkaline phosphatase at 290 U/L (reference range: 505.0-4,667.0 U/L), and hyperkalemia at 5.1 mmol/L (reference range: 2.4-4.7 mmol/L). 

The high white blood cell count and diarrhea indicated the patient needed to be admitted into the hospital’s isolation facility. Once in the isolation stall, we placed a 14-gauge 13-centimeter over-the-needle intravenous catheter in the filly’s right jugular vein, secured it with 0 Prolene on a curved, reverse cutting needle, and started her on 500 milliliters/hour of lactated Ringer’s solution. The filly continued on the 500 micrograms of misoprostol prescribed by the associate veterinarian who had rechecked her that morning. We added one scoop of Platinum Performance Platinum Balance every 12 hours, 60 milliliters of DTO smectite orally every 24 hours, 500 milligrams of minocycline orally every 12 hours, and 125 milligrams of flunixin meglumine IV every 24 hours. 

Throughout the night, the filly continued to have a high heart rate, increased borborygmi, and semiformed to liquid diarrhea. Her appetite was depressed, and she did not have much interest in grain or fresh grass. 

Day 2: Tests and Samples 

The next morning, we took a fecal sample for a polymerase reaction diarrhea test and a blood antibody test for Lawsonia intracellularis and submitted them to a referral laboratory to test for equine coronavirus, Clostridium difficile toxins A and B, L. intracellularis, Neorickettsia risticii, and Salmonella spp. The lab results came back later as negative for all tests run. A packed cell volume, total protein, systemic lactate, and a complete cell count were also taken to check for dehydration and tissue perfusion. The filly’s packed cell volume was 32%, total protein was 6.4 g/dL, and systemic lactate was 1.6 mmol/L. The blood cell count showed the white blood cell count had decreased to 9.45 K/μL, but the monocytes had increased to 0.64 K/μL. These levels were all within normal limits and did not indicate the patient was not endotoxic. 

While taking a fecal sample, the filly began acting painful, rolling and kicking at her abdomen. We sedated her using 2.5 grams butorphanol and 75 milligrams xylazine IV and performed an ultrasound examination. The veterinarians found thickened intestinal loops and a moderate amount of free fluid ventrally, indicating inflammation within the bowels. After coming out of sedation, the filly remained bright, but her appetite was not consistent. Throughout the day, her temperature fluctuated between 101.6 and 99.0 degrees F. 

Day 3: A Turn for the Worse 

The following day, the filly became painful in the early morning hours. She started thrashing, lying in lateral, and groaning with a heart rate of 80. She passed two piles of manure in the stall but it smelled rather foul. Due to her high level of discomfort, the patient was sedated with 60 milligrams of xylazine IV and 2.5 milligrams of butorphanol IV and IM. This amount of discomfort continued throughout the day, with the patient becoming intermittently very painful, rolling, stretching out, and vocalizing her discomfort. At 11:00 a.m., the filly’s capillary refill time increased to 3 seconds, and her mucous membranes had turned red. 

Due to the patient’s drastic change in comfort, we performed an abdominal paracentesis and another ultrasound. A total protein, lactate, and cell count was performed on the abdominal fluid. Total protein and lactate were within normal limits at 0.6 g/dL and 1.2 mmol/L, respectively. The cell count on the abdominal fluid was also within normal limits, with the total nucleated cell count at 1.20 K/μL, the granulocyte count at 0.89 K/μL, and the agranulocyte count at 0.31 K/μL. The fluid was also normal in color and clarity, being clear and straw-colored. Systemic total protein and lactate was 6.0 g/dL and 0.9 mmol/L. 

We acquired another full panel of bloodwork to assess any differences over the last 24 hours. The new bloodwork showed the patient’s white blood cells, especially the neutrophils, had decreased significantly. The white blood count had decreased to 4.61 K/μL, and the neutrophils had decreased to 2.27 K/μL. This was a potential indicator of a viral infection, but we didn’t know what type because the fecal results weren’t finished. A fecal culture for aerobic identification and susceptibility was also sent out to a reference lab. 

Day 4: Exploratory Surgery 

Unfortunately, the next day, the filly’s pain level increased and, unlike the day before, could not be controlled by sedation and non-steroidal anti-inflammatories. She was looking at her abdomen and displaying a flehmen response after taking a few bites of feed at 7:00 a.m. An hour later, the filly was thrashing. She received 75 milligrams of xylazine and 2.5 milligrams of butorphanol IV as well as 125 milligrams of flunixin meglumine IV. This only lasted a few hours; at 12 p.m. the patient was back down and thrashing. We sedated her again, this time with 75 milligrams of xylazine IV and 75 milligrams of xylazine IM. Again, this did not last and the patient received 10 milligrams of butylscopolammonium chloride IV an hour later. At this point, the owners were told the patient’s pain was becoming uncontrollable with sedation and were given the option of exploratory surgery or humane euthanasia. The owner decided on emergency abdominal exploratory surgery. 

The filly received presurgical antibiotics amikacin sulfate and ampicillin IV at 2,150 milligrams and 1 gram, respectively. She also received an additional 125 milligrams of flunixin meglumine, 5 milligrams of butorphanol, and then 400 milligrams of ketamine and 10 milligrams of diazepam for anesthesia. The patient was then placed in dorsal recumbency. We placed a 12-millimeter endotracheal tube and put the filly on 2.5 sevoflurane inhalant. She received fluids during the surgery at the same rate given before being on the table: 500 milliliters/hour. The patient did breathe on her own, ranging from 8-11 bpm. We placed a 20-gallon 1 ¾-inch IV catheter in the filly’s submandibular artery for direct arterial blood pressure, which started at a mean of 55 mmHg, so we supplemented with a slow drip of dobutamine at one drop per 3 seconds to help bring up the mean blood pressure to 75 mmHg. 

The patient’s abdomen was clipped and prepped with chlorhexidine scrub and alcohol sterilely. We placed a drape over her and made an approximately 10-inch incision along the midline and exteriorized the intestine. During the process to exteriorize the intestine, the surgeon found grossly enlarged veins throughout the small intestine and a mesenteric rent at the base of the mesentery. The surgeon attempted to correct the segment of intestines that had passed through the defect, but the placement of tear in the mesentery and the enlargement of the intestine made it impossible to correct the defect. The surgeon went to inform the owner. 

During the few minutes that the surgeon was out speaking to the owner about the filly’s poor prognosis, her blood pressure dropped to 40 mmHg and her heart rate dropped to 50 bpm from 70 bpm during the surgery. We quickly turned off all sevoflurane to the patient and informed the surgeon. Because the owners decided to humanely euthanize, no further lifesaving drugs or procedures were performed. 

After the patient was euthanized on the surgery table, the surgeon went back into the abdomen to further assess the problem. The surgeon found that one of the engorged veins within the intestines that had passed through the tear in the mesentery had burst, and the patient had blood clots within her abdomen, which is why she started to crash under anesthesia. 

In Summary 

This case was a very interesting one that used a lot of my skills, from the initial hospitalization to the final step in a colic case. It exhausted all the resources at our disposal until our last option was surgery. This case moved from a mild colic episode to multiple hospitalizations to an isolation case and then, finally, an exploratory surgery. 

I was intimately involved with the monitoring and treatments in this case throughout the patient’s many hospitalizations. The skills I used included placing an over-the-wire IV jugular catheter, passing a scope for a gastroscopy, IV fluid therapy, IV pain management, oral medications, induction and maintenance of anesthesia including placement of an endotracheal tube, using a rebreathing bag, placing an arterial IV catheter and monitoring direct arterial blood pressure, and performing an electrocardiogram. 

This case shows the vast progression of medical treatments we can use to treat colic within the spectrum of veterinary medicine. The owners’ monitoring at home between hospitalizations and the staff’s careful observations indicated when the patient needed more treatment. This case also shows that sometimes, medical treatment cannot fix all problems during a colic case, and we must move to the next step in treatment, surgical intervention. 

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