A4-month-old 127.5-kg (280.5-lb) Holstein heifer calf (patient 1) was referred to University of Wisconsin Veterinary Care for evaluation of dyspnea and wheezing that had persisted for 2 months despite antimicrobial and anti-inflammatory treatment (drugs and dosages unknown). Other pertinent history included the fact that the calf was born with the assistance of forced extraction owing to a posterior presentation.
During the initial examination at the referral hospital, the calf was quiet but alert and responsive. The calf was slightly hyperthermic (rectal temperature, 39.3°C [102.8°F]; reference range, 38.0°C to 39.17°C [100.4°F to 102.5°F]), tachycardic (heart rate, 100 beats/min; reference range, 60 to 84 beats/min), and tachypneic (respiratory rate, 40 breaths/min; reference range, 10 to 30 breaths/min). It had increased inspiratory effort and stridor, and coughing was elicited by tracheal palpation. On thoracic auscultation, upper airway (tracheal) sounds were referred over the thoracic cavity. A soft tissue mass was palpable at the caudoventral aspect of the neck just cranial to the thoracic inlet. Results of a CBC and serum biochemical analysis were unremarkable.
Thoracic radiographs were obtained. Lateral radiographic images indicated severe dorsoventral narrowing of the tracheal lumen. The narrowing was most severe at the level of the thoracic inlet (Figure 1). The tracheal lumen appeared to return to its normal diameter caudal to the stenotic region at the level of the first intercostal space. The lung field had a mild diffuse bronchial and unstructured interstitial pattern suggestive of mild interstitial pneumonia, bronchopneumonia, or an expiration artifact. A well-circumscribed, semicircular, soft tissue or fluid-opaque mass that measured approximately 20 × 8 cm was located ventral to the trachea and extended from the midcervical region to the thoracic inlet. Differential diagnoses for the mass included thymus, enlarged cervical lymph node, abscess, and hematoma. Nasotracheal endoscopy confirmed that the trachea became stenotic approximately 70 cm distal to the nares (Figure 2).
Computed tomography was performed to obtain specific measurements of the stenotic region of the trachea for potential stent development. The CT sequences revealed that the caudal aspect of the cervical portion of the trachea gradually narrowed dorsoventrally until it reached the level of the thoracic inlet. The intraluminal area of the trachea at the thoracic inlet was > 80% less than that at the cranial aspect of the cervical portion of the trachea (Figure 3). Caudal to the thoracic inlet, the intrathoracic portion of the trachea gradually expanded but remained ellipsoidal in shape until it reached the carina. The abnormally narrowed portion of the trachea was 16.8 cm in length and extended from the caudal aspect of the cervical portion of the trachea to immediately cranial to the carina. The most severely narrowed portion of the trachea was approximately 4.5 cm in length and was located in the region of the thoracic inlet. Mineral-attenuating calluses with smooth margins were identified bilaterally within the midbody of the first and second ribs and measured 3 cm at their widest points. Progressively smaller calluses were located within the midbody of the third to sixth rib pairs. The callus on the left first rib appeared to be in contact with but did not deviate the trachea. The distal aspects of the left and right first ribs were axially displaced into the thoracic cavity, the right rib more so than the left rib. The soft tissue mass immediately cranial to the thoracic inlet measured 5.6 × 7.0 × 15 cm and caused minimal dorsal displacement of the adjacent portion of the trachea. While the calf was still sedated after completion of the CT evaluation, a fine-needle aspirate specimen was obtained from the mass and submitted for cytologic evaluation. Cytologic evaluation of the specimen revealed lymphoid tissue with frequent sheets of ciliated respiratory epithelial cells, which was most consistent with a bronchial cyst.
Tracheal collapse and stenosis secondary to perinatal rib fractures were diagnosed on the basis of clinical and diagnostic imaging findings. Initially, the owner agreed to pursue endoscopic placement of a stent within the lumen of the stenotic portion of the trachea. The calf was discharged from the hospital and sent home until a stent could be custom manufactured. It was recommended that the calf be individually housed in a cool, dry, well-ventilated stall in an environment with little dust and no access to headlocks or stanchions.
The calf's dyspnea became less apparent at home over the subsequent 4 to 6 weeks, and the owner decided to forego stent placement. The calf's growth appeared to be unaffected by the condition because it remained comparable in size to similarly aged herdmates.
Patient 1 became a productive oocyte donor after reaching sexual maturity and was returned to the referral hospital for follow-up diagnostic imaging at 21 months old. At that time, the patient was 6 months pregnant and was bright, alert, and active with a body condition score of 4/5 (Figure 4). On physical examination, rectal temperature (38.7°C [101.6°F]), heart rate (60 beats/min), and respiratory rate (24 breaths/min) were all within the respective reference ranges. Tracheal and thoracic auscultation revealed no abnormalities. The soft tissue mass in the caudal cervical region was no longer palpable, and no other remarkable findings were identified.
Radiographs of the caudal portion of the cervical region and thorax were obtained. Evaluation of the radiographic images revealed no overt evidence of a collapsing trachea and no other abnormal findings (Figure 5). Remarkably, the tracheal stenosis had resolved, and there was no appreciable narrowing of the tracheal lumen between the midcervical region and carina.
During nasotracheal endoscopy, a slight linear mucosal defect that occupied < 20% of the tracheal circumference was observed in the dorsal lining of the trachea approximately 80 to 90 cm distal to the nares (Figure 6). The tracheal stenosis was deemed resolved. Since that time, patient 1 has calved and has become a productive member of the herd.
A 4-month-old 174-kg (382.8-lb) Holstein bull calf (patient 2) was referred to University of Wisconsin Veterinary Care for evaluation of persistent cough and dyspnea that had persisted for 3 months despite antimicrobial and anti-inflammatory treatment (drugs and dosages unknown). The calf had no history of trauma, and its birth was not witnessed.
During the initial physical examination at the referral hospital, the calf was bright, alert, and responsive. The calf was euthermic (rectal temperature, 39°C [102.2°F]), tachycardic (heart rate, 130 beats/min), and tachypneic (respiratory rate, 60 breaths/min), with increased inspiratory effort and stridor. The calf had an occasional cough that was honking in nature. On thoracic auscultation, sounds from the upper airway (trachea) were referred over the thoracic cavity, which made it challenging to hear air movement within the lower airways. Results of a CBC and serum biochemical analysis were unremarkable.
Thoracic radiographs were obtained. The right lateral radiographic image indicated a marked narrowing of the trachea from the level of C6 to the thoracic inlet (Figure 7). The left first, second, and third ribs were misshapen, compared with their contralateral counterparts. For each of the left first, second, and third ribs, the midbody had a smoothly marginated fusiform widening and the distal aspect had an abnormal curve in the cranial direction.
Similar to patient 1, CT was performed to obtain specific measurements of the stenotic region of the trachea for potential stent development. The CT sequences confirmed marked dorsoventral narrowing of the trachea, with a > 90% reduction in the diameter of the intratracheal lumen at the level of the thoracic inlet (Figure 8). Overall, an 11.3-cm portion of the trachea was abnormally narrowed, with the most severely narrowed portion measuring approximately 4.6 cm in length. Nothing within the mediastinum appeared to be compressing the trachea. There was axial deviation and mild flaring of the midbody region, albeit with smooth cortical margins, of the cranial aspects of the left first, second, and third ribs. Given the clinical and diagnostic imaging findings, the diagnosis was tracheal stenosis and collapse secondary to perinatal rib fractures.
Because the calf appeared to be systemically healthy with only an occasional cough and dyspnea, it was discharged from the hospital and sent home for conservative treatment. It was recommended that the calf be individually housed in a cool, well-ventilated environment with little dust.
The calf was subsequently acquired by and moved to a commercial bull stud facility. Similar to patient 1, patient 2's clinical signs resolved over time without further intervention. Patient 2 was reexamined at 26 months of age for the purpose of the present report. At that time, patient 2 weighed approximately 818 kg (1,800 lb) and had a satisfactory body condition. Physical examination findings were unremarkable with no abnormalities detected during tracheal and thoracic auscultation. A nasotracheal endoscopic examination was performed with a 3-m endoscope,a which allowed the entire length of the trachea to be evaluated to the carina. The trachea appeared clinically normal throughout its entire length (Figure 9), and it was determined that the tracheal stenosis had resolved.
The bull stud facility began collecting semen from patient 2 when the bull achieved sexual maturity. Patient 2 remains a productive member of the bull stud facility and has hundreds of progeny within the Holstein breed.
The authors thank Dr. Jeff Bleck of Dairy Doctors, Plymouth, Wis, for assistance with management and follow-up for patient 1, and Chris Kortes of Karl Storz Veterinary Endoscopy, Goleta, Calif, for technical assistance with the portable endoscopic equipment used to acquire the follow-up endoscopic images for patient 2.
Japanese Society of Exotic Pet Medicine
Karl Storz Veterinary Endoscopy, Goleta, Calif.
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