Background: Diffuse parenchymal lung diseases (DPLD) constitute a group of over 200 diverse etiologic entities which present with respiratory symptoms and diffuse lung infiltrates and account for 15% of patients seen by a pulmonary physician.
Objective: To evaluate the role of transbronchial lung biopsy and bronchoalveolar lavage in diagnosis of diffuse parenchymal lung disease.
Patients and Methods: This prospective cross-sectional study was carried out at the Department of Chest, Al-Hussein University Hospital, during the period from October 2019 to October 2020, and included sixty patients admitted in the inpatient wards with undiagnosed DPLD, after detailed history taking, physical examinations, routine labs, chest X-ray PA view, HRCT chest, pulmonary function tests (PFTs) as simple spirometry, ECG, echocardiography and Arterial blood gases evaluation. All of them were subjected to fibrooptic bronchoscope, transbronchial lung biopsy and bronchoalveolar lavage.
Results: As regard comparison between bronchoalveolar lavage (BAL) and  transbronchial lung biopsy (TBLB) diagnostic yield there was a statistical significant difference between TBLB positive and negative patients, as regard BAL predominant cells and BAL microbiology. the comparison of histopathology as regard TBLB diagnostic yield showed a statistical significant difference between TBLB positive and TBLB negative patients.
Conclusion: Bronchoalveolar lavage was a minimally invasive procedure performed during flexible bronchoscopy. BAL cellular analysis alone was insufficient to diagnose the specific type of DPLD, except in malignancies and some rare interstitial lung diseases (ILDs), and the yield of bronchoscopic lung biopsy was high in diseases where the lesions were peri bronchial in distribution such as in sarcoidosis, hypersensitivity pneumonitis and organizing pneumonias.