en Pulmonology Pulmonology case report case report <span style="font-family:Times New Roman;"><span style="color:#0033ff;"><strong><em>Background</em></strong><em>:</em> </span>Peritoneal infection following pleural empyema is not a common occurrence. Concomitant pleural empyema and peritonitis have been described in the literature mostly in immunocompromised patients with different pathogenic mechanisms and a wide array of microorganisms. Here we report a case of concomitant pleural empyema and peritonitis with an unusual microorganism in an immunocompetent host.<br> <span style="color:#0033ff;"><strong><em>Case presentation:</em></strong></span> The patient is a 42-year-old man with a history of 2 weeks epigastric pain who had been referred for surgical consult after failure of outpatient medical therapy. Physical examination at emergency ward revealed generalized abdominal guarding, tenderness and rebound tenderness. On emergent laparotomy, the peritoneal cavity was full of malodor pus. All abdominal viscera were intact but there was a 2x2 centimeter defect in the top of left hemi-diaphragm. Pus originated from the left thoracic cavity and then drained to the peritoneal cavity. <em>Morganella morganii</em> grew in the culture of aspirated pleural fluid. After abdominal lavage and chest tube drainage and receiving 14 days course of parenteral antibiotics, the patient experienced marked clinical improvement. Punctual history taking revealed a history of pneumonia before the beginning of abdominal symptoms.<br> <span style="color:#0033ff;"><strong><em>Conclusion:</em></strong></span> In concomitant empyema and peritonitis in an immunocompetent patient, one should keep in mind the possibility of diaphragmatic defect and infection by unusual organisms like <em>M. </em><em>m</em><em>organii.</em></span> Empyema, Peritonitis, Diaphragmatic Defect, Morganella Morganii, pyopneumothorax 232 235 http://caspjim.com/browse.php?a_code=A-10-648-2&slc_lang=en&sid=1 Mahnaz Amini aminim@mums.ac.ir 100319475328460028203 100319475328460028203 No Department of Pulmonary and Critical Care Medicine, Lung Diseases Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Mohammad Reza Motie motiem@mums.ac.ir 100319475328460028204 100319475328460028204 Yes Department of Surgery, Surgical Oncology Research Center, Imam Reza Hospital, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Saeid Amel Jamehdar ameljs@mums.ac.ir 100319475328460028205 100319475328460028205 No Antimicrobial Resistance Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran Mohammad Reza Kasraei kasraeimr@mums.ac.ir 100319475328460028206 100319475328460028206 No Department of Pulmonary and Critical Care Medicine, Lung Diseases Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Mansoore Sobhani sobhanim921@mums.ac.ir 100319475328460028207 100319475328460028207 No Lung Diseases Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran