Page 1274 - Cote clinical veterinary advisor dogs and cats 4th

Mediastinal Disease 641

• Mediastinal masses: mediastinitis, pleural • Arterial blood gas to assess respiratory Chronic Treatment
function
space disease, pulmonary masses, thoracic • Coagulation testing (prothrombin time • Pneumomediastinum: cage rest
VetBooks.ir esophageal diverticulum, normal thymic [PT], partial thromboplastin time [aPTT]) weeks) antimicrobial therapy based on culture Diseases and Disorders
wall masses, mediastinal fat or fluid,
• Mediastinitis: long-term (minimum, 4-6
if hemorrhage (p. 1325)
and susceptibility results
enlargement (young animals)
• Mediastinal hemorrhage: mediastinitis,
of therapy.
mediastinal fat or fluid, mediastinal mass, • CT or MRI (p. 1132) can better delineate ○ Fungal mediastinitis may require months
the nature and extent of space-occupying
normal thymic enlargement (young animals), disease and address possible metastatic disease ○ Large granulomas causing cranial vena cava
thymic hemorrhage (rare) (CT). syndrome may require surgical excision/
• Fungal serologic testing for possible fungal debulking.
Initial Database mediastinitis • Mediastinal masses
• Thoracic radiographs • Scintigraphy (technetium or iodine 131) ○ Chemotherapy or radiation therapy for
○ Pneumomediastinum: visualization of could confirm ectopic thyroid neoplasia. lymphoma
mediastinal vascular structures not normally • Thoracoscopic exam of the mediastinum ○ Radiation therapy for incompletely
seen (e.g., branches of aorta) is pathog- • Biopsy for histopathologic evaluation can resected or unresectable thymoma
nomonic; subcutaneous emphysema may be obtained transthoracically (Tru-cut) by
also be present thoracoscopy or thoracotomy. Possible Complications
○ Mediastinitis and mediastinal masses: • Flow cytometry analysis of aspirates can dif- • Pneumothorax, pleural effusion, pyothorax
mediastinal widening on dorsoventral or ferentiate thymoma from thymic lymphoma. from thoracostomy tubes
ventrodorsal views, dorsal displacement of • Polymerase chain reaction (PCR) for • Gastrointestinal and/or myelotoxicosis from
trachea on lateral view possible, pleural antigen receptor rearrangement (PARR) to chemotherapeutics
fluid possible, gas in fascial planes of neck demonstrate clonality for lymphoma • Individual drug toxicoses
possible; may be unremarkable in acute ○ Renal: aminoglycosides, amphotericin B
mediastinitis TREATMENT ○ Hepatic: azole antifungals
• Abdominal radiographs: pneumoretroperi- • Surgery entails risks of anesthesia, hemor-
toneum possible Treatment Overview rhage, and infection.
• CBC: leukocytosis if inflammation, rarely Nonlymphoid cranial mediastinal masses
cytopenias or leukemia; anemia if mediastinal typically require surgical intervention, whereas Recommended Monitoring
hemorrhage lymphoid neoplasia is treated like other lym- • Clinical signs
• Serum biochemistry panel: ± hypercalcemia phoma (pp. 607 and 609). Pneumomediastinum • Pulse oximetry, arterial blood gases
(lymphoma) usually resolves with time. • Thoracic radiographs
• FeLV testing • Pleural fluid volume and cytology if thora-
• Thoracic ultrasonography may identify Acute General Treatment costomy tube
masses (e.g., branchial cysts), pleural effu- Pneumomediastinum: • CBC (chemotherapy)
sion, lymphadenopathy, vascularity/vascular • Mild signs: cage rest; subcutaneous emphy- • Serum chemistries for renal and hepatic
invasiveness of mass (impacts biopsy/excision sema typically resolves in approximately 2 function, depending on drugs administered
possibilities), mediastinal fluid if hemorrhage weeks.
○ The presence of internal cysts or a het- • Marked signs: provide supplemental oxygen. PROGNOSIS & OUTCOME
erogenous echogenicity in a mediastinal • Drain subcutaneous emphysema only if
mass makes thymoma more likely than causing discomfort. • Pneumomediastinum: good if underlying
lymphoma. • If large tracheal tear/laceration, consider disease resolves or can be corrected
• Fine-needle aspiration with cytologic surgical repair (p. 986). • Mediastinitis: varies, depending on severity;
evaluation • Thoracocentesis if pneumothorax chronic cases may be hard to resolve.
○ Risks include hemothorax, pneumothorax, Mediastinitis: • Mediastinal masses
or nondiagnostic sample. • Broad-spectrum empirical antimicrobial ○ Lymphoma: chemotherapy usually palliative
○ Inflammatory: culture (aerobic, anaerobic, therapy pending culture/sensitivity ○ Others: surgery for cure or palliation. The
Nocardia, Actinomyces, ± fungal) • Severe systemic signs may require IV fluids prognosis for dogs and cats with surgical
○ Good correlation between cytological and and/or additional supportive therapy. excision of thymoma is generally good,
histological exam of mediastinal masses • Esophageal laceration/rupture may require even if invasive.
(single study) surgery. ○ Cats: median 1-year survival rate: 89%
• Thoracocentesis for cytologic evaluation and Mediastinal masses: ○ Dogs: median 1-year survival rate: 64%
culture if fluid present (p. 1343) • Surgery, chemotherapy, radiation therapy, or • Mediastinal hemorrhage: prognosis varies
• Acetylcholine-receptor antibody concentra- a combination based on type of mass with cause and severity.
tion if mediastinal mass and megaesophagus • Less invasive surgical techniques with
and/or generalized weakness (myasthenia video-assisted thoracic surgery/thoracoscopy PEARLS & CONSIDERATIONS
gravis [p. 668]) have been described as alternatives to
thoracotomy. Comments
Advanced or Confirmatory Testing • Mediastinal cysts: drained transthoracically • Advanced imaging helps define internal
• Tracheoscopy/bronchoscopy if pneumome- or excised. structure and extent of mediastinal masses
diastinum and patient stable (p. 1074) Mediastinal hemorrhage: and detect pulmonary metastases.
• Contrast (water-soluble) esophagram for • Volume support: crystalloid or colloids • Patients at risk for foreign body inhalation
suspected rupture (p. 309) • Blood transfusion if severe (hunting or field trial dogs): consider Nocar-
• Esophagoscopy if suspect esophageal disease • If coagulopathy due to vitamin K antagonism dia, Actinomyces as causes of mediastinitis.
(p. 1098) or deficiency, treat with vitamin K 2.5 mg/
• Cytologic evaluation of respiratory wash kg SQ in multiple sites initially and pos- Prevention
samples if underlying pulmonary disease sibly a fresh-frozen plasma transfusion (p. Avoid iatrogenic tracheal injury associated with
• Echocardiography if heart base mass 1169), followed by vitamin K 2.5 mg/kg PO • Intubating using a stylet
(p. 1094) q 12h. • Overinflation of endotracheal tube cuffs

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