Pleural effusion

A parapneumonic effusion is a pleural effusion arising alongside bacterial pneumonia, ranging from a sterile uncomplicated collection to infected, loculated empyema. Diagnosis rests on thoracentesis with Light's criteria, pH, and glucose; complicated effusions and empyema require prompt chest tube drainage plus intravenous antibiotics, with intrapleural fibrinolytics or surgery for inadequate drainage.

Empyema is frank pus or a culture/Gram-stain-positive bacterial infection of the pleural space, most often complicating pneumonia, that requires prompt drainage plus antibiotics rather than antibiotics alone.

Hemothorax is blood in the pleural space, most often from blunt or penetrating chest trauma, defined by a pleural fluid hematocrit above 50% of the peripheral hematocrit. Each hemithorax can hold up to 40% of circulating blood volume, so massive hemothorax is a hemorrhagic-shock emergency treated with simultaneous chest tube thoracostomy and resuscitation, with operative thoracotomy triggered by fixed drainage thresholds.

Chylothorax is accumulation of lymphatic chyle in the pleural space from thoracic duct disruption or obstruction, diagnosed by a pleural fluid triglyceride above 110 mg/dL and managed with drainage, fat restriction, and duct-directed therapy when output stays high.

Heart failure is a clinical syndrome of impaired cardiac filling or ejection causing congestion and reduced perfusion, classified by ejection fraction. Diagnosis integrates symptoms, signs, natriuretic peptides, and echocardiography, and treatment of reduced-ejection-fraction disease is quadruple guideline-directed therapy, with device therapy and cause-specific management.

Cirrhosis is end-stage hepatic fibrosis with regenerative nodules, staged as compensated or decompensated by the onset of ascites, variceal hemorrhage, encephalopathy, or jaundice. Severity is graded by Child-Pugh class and MELD, and management centers on treating the underlying cause, surveillance for varices and hepatocellular carcinoma, and timely transplant referral once decompensation appears.

Pulmonary embolism is thrombus, usually from a lower-extremity deep vein thrombosis, obstructing the pulmonary arterial circulation and causing V/Q mismatch, right ventricular strain, and hypoxemia. Diagnosis follows Wells criteria (with PERC in low-risk patients) to sequence D-dimer, CT pulmonary angiography, and V/Q scanning, and management is risk-stratified anticoagulation escalating to thrombolysis or embolectomy for hemodynamic instability.

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading global cause of infectious death and presents as latent infection, primary/secondary pulmonary disease, or extrapulmonary and disseminated (miliary) disease. Diagnosis rests on AFB smear, NAAT, and mycobacterial culture (the gold standard), and drug-susceptible active disease is treated with a four-drug regimen (isoniazid, rifampin, pyrazinamide, ethambutol) for 2 months followed by isoniazid plus rifampin for 4 to 7 months.

Lung cancer is the leading cause of cancer death worldwide, split into non-small cell lung cancer (NSCLC, 80% of cases: adenocarcinoma, squamous cell, large cell) and small cell lung cancer (SCLC, 10-15%), both driven overwhelmingly by cigarette smoking. Diagnosis requires tissue histopathology, staging drives treatment (TNM staging for NSCLC, limited versus extensive stage for SCLC), and management ranges from lobectomy in early-stage disease through concurrent chemoradiation and consolidation immunotherapy in locally advanced disease to targeted tyrosine kinase inhibitors, immune checkpoint inhibitors, or platinum-based chemotherapy in metastatic disease.