What Is Your Diagnosis?

Amy K. Stuart 1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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Katie L. Ellis 2Department of Environmental Health and Radiological Health Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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Kurt T. Selberg 2Department of Environmental Health and Radiological Health Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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Robert J. Callan 1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523.

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History

A 9-day-old approximately 25-kg (55-lb) Jersey bull calf that had been transported from Texas to Colorado on the day of birth was evaluated because of a 3-day history of coughing and diarrhea, with lethargy that progressed to lateral recumbency 12 hours before examination. The calf was obtunded, laterally recumbent, and dehydrated (approx 8% to 10%). The calf's rectal temperature and heart rhythm and rate were within reference limits; however, the calf was tachypneic (50 breaths/min; reference range, 15 to 40 breaths/min). The calf's ears as well as the distal aspect of all 4 limbs were cold to the touch, and its femoral pulses were absent bilaterally. Signs of deep pain response and withdrawal reflexes were absent in both hind limbs, the anal reflex was absent, and anal tone was low.

Results of a CBC indicated a regenerative left shift with neutropenia (1.8 × 103 neutrophils/μL; reference range, 2.0 × 103 neutrophils/μL to 6 × 103 neutrophils/μL) and band neutrophil cells (1.2 × 103 band neutrophils/μL; reference range, ≤ 0.4 × 103 band neutrophils/μL). Additional abnormalities included a moderate number of toxic neutrophils, hyperfbrinogenemia (1,200 mg/dL; reference range, 200 to 600 mg/dL), thrombocytosis (685 × 103 platelets/μL; reference range, 170 × 103 platelets/μL to 650 × 103 platelets/μL), and hemoconcentration (Hct, 39%; reference range, 24% to 35%). Results of serum biochemical analyses indicated metabolic acidosis (bicarbonate concentration, 99 mEq/L; reference range, 23 to 33 mEq/L), hypernatremia (165 mEq/L; reference range, 132 to 144 mEq/L), hyperchloremia (133.5 mEq/L; reference range, 90.0 to 102.0 mEq/L), high creatinine concentration (1.5 mg/dL; reference range, 0.6 to 1.0 mg/dL), low albumin concentration (2.3 g/dL; reference range, 2.8 to 4.2 g/dL), and high activities of creatine kinase (466 U/L; reference range, 55 to 335 U/L) and γ-glutamyltransferase (90 U/L; reference range, 13 to 35 U/L).

The calf was treated with ceftiofur hydrochloride (2.2 mg/kg [1.0 mg/lb], SC, q 24 h), penicillin G procaine (22,000 U/kg [10,000 U/lb], IM, q 12 h), and flunixin meglumine (1.1 mg/kg [0.5 mg/lb], IV, q 12 h). Fluid therapy (balanced crystalloid fluids [2 L, IV, over 30 minutes] followed by 5% dextrose supplemented with 100 mEq bicarbonate [100 mL/h, IV]) was continued overnight to help determine whether the calf's hind limb weakness was because of its dehydration, acidemia, or hypernatremia, alone or in combination. The following morning, the calf was bright and alert but had no palpable femoral pulses, no signs of deep pain response or withdrawal reflexes in either hind limb, and no anal tone. The hind limbs were cool to the touch, and the calf was unable to stand.

Analysis of CSF obtained from the lumbosacral region of the vertebral column revealed no abnormalities. Serum biochemical analyses were repeated and revealed resolution of acidosis (bicarbonate concentration, 27 mEq/L), improved concentrations of chloride (118.6 mEq/L) and sodium (157 mEq/L), unchanged creatinine concentration, and high activities of aspartate aminotransferase (893 U/L; reference range, 40 to 140 U/L) and creatine kinase (23,086 U/L). The calf underwent ultrasonography of the thorax, proximomedial aspects of both hind limbs, and the abdomen, including the distal portion of the aorta (Figure 1).

Figure 1—
Figure 1—

Sagittal (A) and transverse (B and C) transabdominal ultrasonographic images of the distal portion of the aorta of a 9-day-old approximately 25-kg (55-lb) Jersey bull calf evaluated because of a 3-day history of coughing and diarrhea, with lethargy that progressed to lateral recumbency 12 hours before examination. A—The image is at the level just cranial to the area of the bifurcation for the iliac arteries, and cranial is to the left of the image. B—The image is at level of the caudal pole of the left kidney, and the calf's right is to the right of the image. C—The image is at the level just cranial to the area of the bifurcation for the iliac arteries, and the animal's right is to the right of the image.

Citation: Journal of the American Veterinary Medical Association 256, 3; 10.2460/javma.256.3.301

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Diagnostic Imaging Findings and Interpretation

Abdominal ultrasonography of the distal portion of the aorta with a 2.5-MHz wideband curved linear array transducer probe revealed echogenic material in the lumen of the aorta, consistent with a thrombus (Figure 2). The echogenic material extended approximately 5 cm cranially from the area of the bifurcation for the iliac arteries. Results of color-flow Doppler ultrasonography indicated the thrombus fully occluded the aorta and no blood flow beyond it was noted. Additionally, ultrasonography revealed consolidation of lung fields bilaterally, an enlarged urinary bladder, and no appreciable blood flow in the femoral arteries bilaterally.

Figure 2—
Figure 2—

Same images as in Figure 1. An echogenic aortic thrombus (wide arrows; A and C) is evident in the lumen of the caudal portion of the aorta, just cranial to the area of the bifurcation for the iliac arteries. Cranial to the thrombus, the lumen of the aorta appears anechogenic and clinically normal (thin arrows; A and B).

Citation: Journal of the American Veterinary Medical Association 256, 3; 10.2460/javma.256.3.301

Treatment and Outcome

Because of the poor prognosis associated with aortic thrombosis, the owners elected to euthanize the calf. A necropsy was performed and revealed a fibrin thrombus in the aorta at the level of the bifurcation for the internal and external iliac arteries that also extended 1 to 2 cm into and partially occluded the internal and external iliac arteries bilaterally. Additionally, severe fibrinonecrotic bronchopneumonia and moderate serous abdominal effusion were noted. The calf was tested for the presence of bovine viral diarrhea virus antigens, and the results were negative. Bacterial culture performed on a sample of the calf's liver yielded Acinetobacter spp, and bacterial culture on lung tissue yielded Bacillus spp, Escherichia coli, and Pasteurella spp. No bacteria were isolated from samples of the calf's spleen or aortic thrombus.

Comments

Aortic thrombi and thromboemboli are rarely reported in calves. To our knowledge, only 2 reported cases of thromboemboli have been reported.1,2 Although the exact cause of aortic thrombi and thromboemboli in calves is unknown, authors of previous case reports1,2 hypothesized the cause to have been severe necrotizing colitis and endocarditis of the left atrioventricular valve. No heart lesions or evidence of enteritis were noted in the calf of the present report. Instead, we hypothesized that septicemia secondary to bronchopneumonia caused hypercoagulation, vasculitis, or both, which led to thrombosis of the caudal aspect of the aorta in this calf. On necropsy, the tunica intima of the aorta was irregularly contoured and disrupted where the coagulum of fibrin, RBCs, WBCs, and serocellular debris attached, a finding that suggested the obstruction formed in situ, consistent with a thrombus.

Because of the small size of the calf in the present report, rectal ultrasonography of the aorta was not feasible; however, transabdominal ultrasonography of the aorta was easily performed with the calf in lateral recumbency, and the large size of the thrombus made identifying it easy. Without ultrasonography, the diagnosis would not have been made antemortem. Findings in the calf of the present report indicated that transabdominal ultrasonography can be used to diagnose a thrombus in the abdominal portion of the aorta in neonatal calves.

References

  • 1. Rolfe DL. Aortic thromboemboli in a calf. Can Vet J 1977; 18:321324.

  • 2. Rudmann DG, Stevenson GW. Aortic-iliac thromboembolism as an uncommon sequel to Staphylococcus aureus valvular endocarditis in a calf. J Vet Diagn Invest 1993;5:288290.

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