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Recurrent Airway Obstruction (view source)
Revision as of 12:49, 26 August 2010
, 12:49, 26 August 2010→Laboratory Tests
===Laboratory Tests===
===Laboratory Tests===
Routine haematology and biochemistry are usually within normal limits, and there is little evidence to support the use of serum and intradermal allergy testing in the diagnosis of RAO<sup>allen</sup>.
obtained from tracheal wash (TW) and BAL are characterised
by a marked neutrophilia. BAL should not be performed
Fluids obtained from bronchoalveolar lavage or tracheal wash may be useful in the diagnosis of RAO.
Bronchoalveolar lavage is rarely required for diagnosis of fulminant RAO, and is not innocuous in horses that are dyspneic at rest. It is indicated in horses with mild to moderate disease with poor performance and coughing during exercise. Neutrophilic inflammation (20-90% of total cell count) confirms the presence of lower airway inflammation and differentiates horses with eosinophilic pneumonitis, fungal pneumonia, or lungworm infestation from horses with heaves. Curschmann’s spirals may be observed on cytologic evaluation and represent inspissated mucus/cellular casts from obstructed small airways
The severity of lung inflammation can be evaluated by cytological evaluation of bronchoalveolar lavage fluid (BALF; see chapter by Viel and Hewson for lavage and cytology techniques). In normal horses, lymphocytes and macrophages form the majority of cells in BALF and neutrophils comprise less than ten percent of cells. In horses with RAO or SPAOD, there is an increase in the percentage of neutrophils and, in severely affected animals, neutrophils comprise over 50 percent of cells and are not degenerate. Despite the large number of neutrophils in BALF, there is no evidence of bacterial infection.
BAL should not be performed
if the horse is markedly dyspnoeic and should be
if the horse is markedly dyspnoeic and should be
postponed until the dyspnoea is controlled. There is little
postponed until the dyspnoea is controlled. There
ivis The severity of lung inflammation can be evaluated by cytological evaluation of bronchoalveolar lavage fluid (BALF; see chapter by Viel and Hewson for lavage and cytology techniques). In normal horses, lymphocytes and macrophages form the majority of cells in BALF and neutrophils comprise less than ten percent of cells. In horses with RAO or SPAOD, there is an increase in the percentage of neutrophils and, in severely affected animals, neutrophils comprise over 50 percent of cells and are not degenerate. Despite the large number of neutrophils in BALF, there is no evidence of bacterial infection.
ivis
Aspiration of tracheal mucus or a tracheal lavage can also be used to evaluate lung inflammation but it is less reliable than BALF. Because there can be increased numbers of neutrophils in the tracheal wash but not in BALF [52], it is wiser to base evaluation of peripheral lung inflammation on the cytology of BALF. Presumably increased numbers of neutrophils in the tracheal secretions reflect local tracheal inflammation that does not extend deeper into the lung. Mixed populations of bacteria are common in a tracheal wash and usually are of no significance.
Aspiration of tracheal mucus or a tracheal lavage can also be used to evaluate lung inflammation but it is less reliable than BALF. Because there can be increased numbers of neutrophils in the tracheal wash but not in BALF [52], it is wiser to base evaluation of peripheral lung inflammation on the cytology of BALF. Presumably increased numbers of neutrophils in the tracheal secretions reflect local tracheal inflammation that does not extend deeper into the lung. Mixed populations of bacteria are common in a tracheal wash and usually are of no significance.