Bronchial wash / Bronchoalveolar lavage (BAL)

A bronchial wash or bronchoalveolar lavage can help to establish a definitive diagnosis in lower airway respiratory conditions. When an endoscope is available, bronchoalveolar lavages are superior diagnostically.

Sampling procedure

1. Bronchial Wash Technique - no endoscope

Use a cuffed endotracheal tube. Intubate dog/cat as aseptically as possible under a short-acting, light general anaesthetic and inflate the cuff. Measure the distance from the anterior tip of the endotracheal tube to the carina. Using this as a guide, pass a urinary catheter gently via the endotracheal tube, taking care not to use excess force or damage the bronchi. Use sterile saline or lactated Ringers as the flush solution. As a rule of thumb, 0.5 ml of solution per kg bodyweight divided into 2 – 3 flushes can be safely used. Using an appropriately sized syringe, flush the liquid into the bronchi and recover immediately after each flush, by sucking back on the syringe. Commonly only 10 – 15% of the solution is recovered. It is best to keep the animal anaesthetised lightly enough to have a cough reflex as this helps recovery of sample after input.

2. Bronchoalveolar lavage – with endoscope

Pass the endoscope. A sterile endoscopic catheter is then threaded down the endoscope and visualised as the endoscope occludes the selected airway. Flush fluid and recover as above, commonly 20 – 30% of the volume flushed is retrieved.