Veterinarians often use bronchoalveolar lavage (BAL) for diagnostic testing in calves with pneumonia. BAL involves passing a through the nose and into the lungs, introducing saline solution which then is collected for examination
Sheila M. McGuirk, DVM, PhD and Simon F. Peek, BVSc, MRCVS, PhD, at the University of Wisconsin, provide a description of the BAL procedure in calves.
BAL is performed on sedated calves using a sterilized, flexible catheter with a 3-cc balloon cuff. Restrain the calf, clean its nostrils and extend its head and neck to facilitate passage of the sterile BAL catheter.
Drip sterile saline into the catheter to lubricate the guide-wire stylette. Advance the BAL catheter through the ventral meatus of the nose until it encounters resistance in the caudal pharynx. The restrainer then pushes the poll of the calf’s head ventrally while elevating the ventral mandible and advancing the catheter down the trachea during the inspiratory phase of the respiratory cycle.
Repeated coughing is induced as the catheter is rapidly advanced into a cranial lung lobe bronchus. Hold the catheter in place while removing the guide-wire stylette. Inflate the balloon cuff with 3 cc of air and infuse 120 ml of sterile saline using 60 ml syringes with a stopcock and catheter tipped adapter attached. Immediately after the 120 ml infusion, apply negative pressure to aspirate fluid, a process that usually yields 10 to 40 ml of fluid. Place the fluid sample into a sterile 4-oz specimen cup. Following a second infusion and aspiration, process the pooled sample within two hours or refrigerate until it can be analyzed.
BAL fluid that yields homogenous (> 106 CFU/ml) bacterial or positive Mycoplasma bovis culture is considered abnormal. A disproportionate lowering of macrophages (≤60%) or elevation of neutrophils (≥40%) indicates an inflammatory response.
Iowa State University provides online instructional videos demonstrating the procedures for conducting a transtracheal wash (TTW), featuring Dr. Terry Engelken, and conducting a bronchoalveolar lavage (BAL), with Dr Jim Thompson. Find both videos and related resources here.
For more information on this topic from Dr. Geof Smith at North Carolina State University, read Saving Sick Calves.