INTRODUCTION: Bronchobiliary fistula (BBF) is a rare occurrence of altered anatomy of the biliary duct system in which it connects to the lungs. Biliptysis is pathognomonic for this condition. Predisposing factors include malignancy, bile duct obstruction, trauma, and surgery. Our case highlights a patient who presented with several months of non-resolving right middle lobe (RML) pneumonia who was later found to have a BBF. CASE PRESENTATION:Our patient is a 43-year-old male with a history of colon cancer with liver metastasis on palliative chemotherapy who presented after multiple episodes of RML pneumonia. He had endoscopic retrograde cholangiopancreatography (ERCP) with stent placement for malignant biliary obstruction. Three months later, he had fever, cough, and scant yellow sputum with chest x-ray (CXR) findings of RML consolidation. He received appropriate antibiotics for community-acquired pneumonia. His symptoms recurred two weeks later. During that admission, the CT chest showed consolidation of the RML. Sputum culture grew Klebsiella pneumoniae and was treated appropriately. He had two more similar episodes. Bronchoscopy showed erythematous endobronchial mucosa in the RML with carbapenem-resistant Enterobacteriaceae (CRE) and Klebsiella pneumoniae on culture. Transbronchial lung biopsy was negative for malignancy. After seven months from the initial ERCP, he presented with copious bilious sputum and right pleuritic chest pain. Repeat CT chest showed persistent RML consolidation and 4 cm fluid collection along the hepatic capsule which grew CRE and Klebsiella pneumoniae. This raised suspicion for bronchobiliary fistula. A hepatobiliary iminodiacetic acid (HIDA) scan done did not demonstrate the presence of a fistula. Magnetic resonance cholangiography (MRC) was done which showed a small sinus tract that represented a BBF. He underwent right anterior sectionectomy of the liver with diaphragm repair and ERCP with replacement of biliary stent. DISCUSSION:The most common cause of acquired BBF is liver malignancy likely through obstruction which produces inflammation in the subdiaphragmatic space with subsequent rupture into the bronchial system. Patients can present with pneumonia, while it is rare, it is the most common comorbidity associated with BBF. Our patient presented with biliptysis and recurrent pneumonia with multidrug-resistant organisms. MRC and HIDA are preferred studies as they are non-invasive. Our patient's HIDA scan was not diagnostic but the MRC showed the BBF. Our patient underwent segmental hepatectomy and ERCP with stent replacement with subsequent symptom resolution.CONCLUSIONS: A high index of suspicion is required to diagnose BBF when the presentation is atypical such as in the case of recurrent RML pneumonia. Early diagnosis is important to prevent progressive antibiotic resistance. Non-invasive modalities like HIDA and MRC are preferred for making the diagnosis.