Antemortem Diagnosis of Caudal Vena Cava Thrombosis in 2 Cows

Although the incidence of vena caval thrombosis (VCT) appears low,1 the condition could be underdiagnosed clinically and can even be overlooked during postmortem examination.2 Liver abscesses that rupture or extend into the caudal vena cava (CVC) result in development of a thrombus. Various other conditions such as thrombophlebitis, mastitis, metritis, or foot rot can also lead to the formation of VCT.2 Septic emboli from the thrombus can spread to the heart valves and, more commonly, to the pulmonary vasculature, leading to multifocal bronchopneumonia.2, 3 Affected animals can die suddenly from pulmonary hemorrhage secondary to the erosion of a blood vessel at the site of emboli, but many cows are culled because of chronic illness responding poorly to antimicrobials. Presumptive diagnosis can be made on animals showing signs of chronic inflammatory process, often in association with pneumonia. The main clinical signs include chronic weight loss, inappetance, intermittent fever, and cough.1, 2 The use of ultrasound examination and the description of CVC ultrasonographic appearance by Braun et al2, 4 have improved antemortem diagnosis of VCT. Transabdominal ultrasound allows the identification of hepatomegaly caused by venous liver congestion, and the dilated CVC, appearing as a round vessel in contrast to its normal triangular shape.4 The actual thrombus can rarely be seen2, 5; however, it is usually located in the cranial aspect of the right lobe, medial to the lungs, and therefore cranial to the window where the CVC can be visualized, at the 11th and 12th intercostal spaces. Two cases of VCT are described in which antemortem diagnosis was made by intraoperative ultrasound examination of the liver as well as their response to treatment. Cow 1 is a 3-year-old 650-kg Holstein cow, 2 months postpartum, which was admitted to the Centre Hospitalier Universitaire Vétérinaire of the Université de Montréal for intermittent fever and a month long drop in milk production. Despite several short courses of antimicrobial treatment, no significant improvement was noticed. Upon arrival, physical examination revealed tachycardia (90 beats/min [bpm], reference range: 40–80 bpm), increased respiratory noises, and a hypomotile rumen. The animal was mildly hypothermic on admission (37.9 °C, reference range: 38–39 °C), followed by intermittent fever during hospitalization. A CBC revealed a chronic inflammatory process with neutrophilia (14,200 cells/μL, reference range: 600–4,000 cells/μL) and hyperfibrinogenemia (900 mg/dL, reference range: 200–500 mg/dL). The only important abnormality to the serum chemistry profile was an increase in γ-glutamyltransferase (GGT) activity (82 U/L, reference range: 9.5–39 U/L). Ultrasonography of the left cranial portion of the abdomen revealed effusion and hyperechogenic material compatible with fibrin. Contraction amplitude and frequency of the reticulum were normal. The liver was also imaged near the reticulum, ventrally left to the midline. Because the liver cannot be imaged normally at this location, hepatomegaly was suspected. Abdominocentesis revealed slightly turbid liquid with total protein (TP) concentration and total cell count (TCC) compatible with a modified transudate (TP 4.9 g/dL, reference range: <3.0 g/dL; TCC 309 cells/μL, reference range: 300–5000 cells/μL). Bacterial culture of the liquid yielded no growth. Standard radiographs of the thorax and the reticulum were normal. The remaining differential diagnoses at that time were abscesses, especially in the liver, endocarditis, and VCT. Consequently, treatment with oxytetracycline (10 mg/kg IV q12h) was instituted. On Day 4, ultrasonography of the abdomen, including examination of the liver between the 11th and 12th right intercostal spaces, showed increasing ascites, dilated hepatic veins and vena porta, and important hepatomegaly, and left the strong suspicion of a dilated CVC. Liver biopsy revealed a diffuse vacuolar hepatopathy compatible with a mild mixed inflammation. Echocardiography was normal. Standing right flank exploratory laparotomy revealed only slight adherences between the liver and the abdominal wall, and an enlarged liver with moderately rounded edges. The right and caudate lobes of the liver were scanned from their parietal surfaces with a 7.5 MHz finger grip probea covered with a sterile sleeve. The parietal surface of the right lobe could be scanned cranially near the diaphragm. The CVC could be followed to its entry point in the thoracic cavity. A 3.5-cm-wide thrombus was seen at the cranial aspect of the abdominal CVC, over approximately 2 cm (Fig 1a,1b). No liver abscesses were detected, but the thrombus extended into one of the hepatic veins. Color Doppler was used to confirm the presence of blood flow in the CVC and around the thrombus. Intra-operative ultrasonography of the liver and CVC. Cow 1, a thrombus (white arrow) can be seen in the hepatic portion of the CVC (a) and followed cranially in long axis toward the diaphragm (b). In Cow 2, a liver abscess could be seen when the liver was scanned from its visceral aspect (c). A large thrombus was also present in the CVC (c, d). Dilated hepatic vessels where seen in both cows (white arrowheads). A definitive diagnosis of VCT was made. The owner was informed of the poor prognosis but declined euthanasia because of the high value of the animal, so treatment was continued. During hospitalization, periodic CBCs and chemistry panels showed steady improvement. On day 14, CBC showed a fibrinogen value of 500 mg/dL, and the chemistry panel showed decreasing GGT (50 U/L). The cow's appetite and milk production were also improving. Oxytetracycline (IV) was administered for 3 weeks. Owing to the appearance of transient diarrhea, therapy was continued for 2 weeks after discharge with sodium ampicillin (6 g IV q8h). Six months later, the cow was in good general health, with normal CBC and serum chemistry panel values. One year later, the cow was still in the herd with normal milk production values. Cow 2 is a 3-year-old 645-kg Holstein cow, 7 months postpartum, from the same herd as in Case 1. She was presented for intermittent fever and respiratory problems that responded poorly to treatment administered by the referring veterinarian, including trimethoprim-sulfamethazine, tetracycline, florfenicol and prednisone. On admission, physical examination revealed hyperthermia (39.6 °C), tachycardia (108 bpm), tachypnia (52 breaths/min, reference range: 12–36 breaths/min), increased respiratory noises with sporadic coughing, and a hypomotile rumen. A chronic inflammatory process with neutrophilia (14,100 cells/μL, reference range: 600–4,000 cells/μL) and hyperfibrinogenemia (600 mg/dL, reference range: 200–500 mg/dL) was identified by CBC. Serum biochemical abnormalities included increased GGT (350 U/L, reference range: 9.5–39 U/L), hyperproteinemia (8.5 g/dL, reference range: 6–8 g/dL), and hyperglobulinemia (5.61 g/dL, reference range: 2.62–4.52 g/dL). Thoracic radiographs revealed a bronchial and interstitial pattern compatible with bronchopneumonia. Radiographs of the reticulum did not reveal abnormalities. Transabdominal ultrasonographic examination suggested hepatomegaly with the liver heading ventrally and to the left of the cow's abdomen. Upper airway endoscopic examination and an echocardiography were performed and revealed nothing abnormal. Tracheobronchial aspiration revealed a moderate nonseptic suppurative inflammation. A sample of the aspirate was sent for bacteriological culture. Antimicrobial treatment with sodium ampicillin (6 g IV q8h) was initiated pending the culture results. On day 7, the bacteriological results of the tracheobronchial aspirate revealed Mycoplasma spp. Based on its sensitivity to oxytetracycline, antimicrobial treatment was modified (10 mg/kg IV q12h). On day 10, the liver, the CVC, and the kidney were scanned thoroughly by ultrasonography. The liver veins were dilated and prominent, and the CVC appeared circular and dilated. Hypoechogenic liquid compatible with ascites could be seen between the liver and the right kidney. A presumptive diagnosis of VCT was made, and on day 11, exploratory laparotomy was performed. The same procedure as in Cow 1 was used. Although the incision for the laparotomy was made as cranial as possible, the space available for ultrasonography of the parietal side of the right lobe was limited by the rumen being full. The probe was inserted more ventrally and medially between the rumen and the liver. Attachments limited movement, but this approach allowed visualization of a liver abscess approximately 2.5 cm in diameter, adjacent to a thrombus in a large vessel. Considering the location and size of the vessel, and the fact that venous congestion was diffuse throughout the liver, it was determined to be the CVC (Fig 1c,d). The final diagnosis for Cow 2 was a VCT with hepatic abscess, and a Mycoplasma spp. bronchopneumonia. The CBC on day 16 was normal, whereas the serum biochemical profile revealed increased but improving GGT (174 U/L), hyperproteinemia (8.2 g/dL), hypoalbuminemia (2.61 g/dL), and hyperglobulinemia (5.27 g/dL). The cow was discharged on day 21 with sodium ampicillin (6 g IV q8h) for 2 more weeks. One week after discharge, her appetite, weight, and milk production were increasing. Six weeks later, the cow died suddenly with hemoptysis and epistaxis. Postmortem examination was not performed. To our knowledge, this is the 1st report of the use of intraoperative ultrasonography for the diagnosis of VCT in cattle, and the 1st report of successful treatment. In both animals, although CVC dilation was seen by transabdominal ultrasound, only intraoperative ultrasonography allowed visualization of the thrombus, and, in Cow 2, of a liver abscess. When the thrombus cannot be identified, differential diagnosis for CVC congestion also includes right-sided heart failure, pericarditis, and compression of the CVC by a mass.3 Clinical presentation and imaging techniques can help in ruling out these conditions but it can lead to only a presumptive diagnosis of VCT. Intraoperative ultrasound is an excellent method for confirming the diagnosis of VCT and detecting deep liver abscesses. In human medicine, it is an important diagnostic tool for decision making during liver resection.6 Despite advances in cross-sectional imaging, such as computed tomography and magnetic resonance, unrecognized tumors are still found during intraoperative ultrasonography of the liver.7 Moreover, these noninvasive imaging techniques are expensive and cannot be performed in large animal medicine, particularly in adult cattle. Intraoperative ultrasonography is practical and affordable, and in selected cases, earlier confirmed diagnosis could allow successful treatment with aggressive long-term antibiotherapy. Considering that flank exploratory laparotomy is commonly performed in dairy cattle, ultrasonographic examination of the liver increases the duration and cost of the procedure by a only small amount. It should be kept in mind, however, that not all VCT are located intra-abdominally, and thoracic thrombi are not likely to be seen with this technique. The prognosis of VCT is grave considering the multiple possible complications such as severe abscedative bronchopneumonia, pulmonary bleeding, endocarditis, nephritis, ascites, and sudden death.3 Therefore, treatment is usually not recommended.2 However, long-term and highly dosed antibiotics might be worth an attempt in valuable individuals, as shown in this report. The antimicrobial coverage of both cases was chosen because of its broad-spectrum activity. Moreover, the 2 most common infectious agents, Arcanobacterium pyogenes and Fusobacterium necrophorum, isolated in cases of VCT have been reported to be sensitive to β-lactams and tetracycline antibiotics.8, 9 Despite more severe clinical presentation for Case 2, both cases had the same antimicrobial treatment duration (5 weeks). The owner decided to stop the treatment without any reevaluation in both cases because of their good health and satisfactory production. Mohamed et al5 also reported initial improvement in a heifer in which CVC thrombi and liver abscesses where diagnosed by transabdominal ultrasound, but the animal died suddenly 3 weeks after beginning treatment. Interestingly, this heifer and Cow 2 of this report showed marked pulmonary changes on ultrasonographic and radiographic examination of the thorax, respectively. Although Cow 1 of this report had increased respiratory sounds, there were no apparent changes noticed on thoracic radiographs. This may reflect an earlier stage of the disease and could be a prognosis indicator. The importance of an early diagnosis is once again highlighted, and may by obtained by intraoperative ultrasonography. A 2nd surgery could not be performed on Cow 1 to reassess the ultrasonographic appearance of the thrombus because the owner did not want to subject the animal to the unnecessary stress of transportation considering it is now apparently healthy and in lactation. It would be interesting to follow the changes in the thrombus over time, as well as the vena cave dilation. This report describes the antemortem diagnosis of VCT by intraoperative ultrasonography and response to treatment in 2 cows. VCT should be suspected in cows with a chronic affection, an inflammatory process, venous liver congestion, and CVC dilation at the 11th and 12th intercostal spaces. Intraoperative ultrasonography allows early definitive antemortem diagnosis and initiation of treatment, and may be justified in the case of valuable animals. Alternatively, it can help veterinarians and owners in deciding to cull an animal that is at the risk of pulmonary embolism and sudden death. aFinger Grip Intraoperative Transducer, Aloka, Tokyo, Japan

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