Study guide
5.9 Pleural Disease, Empyema & Pneumothorax
ABIM Internal Medicine Exam
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1 Chapter 0: The ABIM Exam, Blueprint & Study Strategy
0.1 Exam Format, Question Types & the 2026 Blueprint 0.2 Eligibility, Registration, Fees & Exam-Day Logistics 0.3 Scoring, the Passing Standard & Score Reports 0.4 Building a Blueprint-Weighted Study Plan
2 Chapter 1: Cardiovascular Disease (14% of Exam)
1.1 Ischemic Heart Disease & Acute Coronary Syndromes 1.2 Antithrombotic Therapy, Secondary Prevention & Mechanical Complications of MI 1.3 Atrial Fibrillation, Atrial Flutter & Stroke Prevention 1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias 1.5 Heart Failure: Classification, Staging & Guideline-Directed Medical Therapy 1.6 Device Therapy, HFpEF & the Cardiomyopathies 1.7 Valvular Heart Disease & Endocarditis Prophylaxis 1.8 Pericardial Disease & Acute Aortic Syndromes 1.9 Hypertension: Classification, Diagnosis & Secondary Causes 1.10 Hypertensive Crises & Dyslipidemia 1.11 Adult Congenital Heart Disease & Coarctation of the Aorta 1.12 Syncope: Reflex, Orthostatic & Cardiac Causes 1.13 Cardiac Physical Examination, Murmurs & Antithrombotic Selection
3 Chapter 2: Endocrinology, Diabetes & Metabolism (9% of Exam)
2.1 Diabetes Mellitus: Diagnosis, Glycemic Targets & Pharmacotherapy 2.2 Insulin Therapy, Hyperglycemic Emergencies & Chronic Complications 2.3 Thyroid Function Testing & Hypothyroidism 2.4 Thyrotoxicosis, Thyroid Storm & Thyroid Nodules 2.5 Adrenal & Pituitary Disorders 2.6 Hypercalcemia, Hypocalcemia & Disorders of Mineral Metabolism 2.7 Osteoporosis & Paget Disease of Bone 2.8 Ovarian, Testicular & Reproductive Endocrine Disorders 2.9 Hypoglycemia, Endocrine Tumors, Polyglandular Syndromes & Severe Hypertriglyceridemia
4 Chapter 3: Gastroenterology & Hepatology (9% of Exam)
3.1 Esophageal Disease 3.2 Stomach & Duodenal Disease and Gastrointestinal Hemorrhage 3.3 Inflammatory Bowel Disease 3.4 Celiac Disease & Irritable Bowel Syndrome 3.5 Diverticular Disease & Colorectal Cancer Screening 3.6 Viral Hepatitis, Steatotic & Alcohol-Associated Liver Disease 3.7 Cirrhosis & the Complications of Portal Hypertension 3.8 Acute Pancreatitis 3.9 Chronic Pancreatitis & Biliary Tract Disease 3.10 Inherited, Autoimmune & Drug-Induced Liver Disease 3.11 Small Intestinal Disease, Ischemia & Gastrointestinal Complications of HIV
5 Chapter 4: Infectious Disease (9% of Exam)
4.1 Lower Respiratory Tract Infections & Sepsis Syndromes 4.2 Viral Respiratory Pathogens & Tuberculosis 4.3 Central Nervous System Infections 4.4 Skin, Soft Tissue, Bone & Joint Infections 4.5 Infective Endocarditis & Cardiovascular Infection 4.6 Clostridioides difficile & Catheter-Related Bloodstream Infection 4.7 HIV Diagnosis, Antiretroviral Therapy & Prevention 4.8 Opportunistic Infections & Sexually Transmitted Infections 4.9 Fever of Unknown Origin, Neutropenic Fever & Toxic Shock 4.10 Travel-Related Illness, Vector-Borne Disease & Outbreaks 4.11 Infection Prevention, Nosocomial Infection & Postexposure Prophylaxis 4.12 Rheumatic Fever, Poststreptococcal Disease, Enteric & Hepatic Infections
6 Chapter 5: Pulmonary Disease (9% of Exam)
5.1 COPD: Diagnosis, GOLD Classification & Initial Pharmacotherapy 5.2 Interventions That Reduce COPD Mortality & Exacerbation Management 5.3 Asthma: Diagnosis, Stepwise Therapy & Status Asthmaticus 5.4 Interstitial Lung Disease & Idiopathic Pulmonary Fibrosis 5.5 Sarcoidosis, Hypersensitivity Pneumonitis & Occupational Lung Disease 5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation 5.7 Pulmonary Hypertension & Sleep-Disordered Breathing 5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation 5.9 Pleural Disease, Empyema & Pneumothorax 5.10 Bronchiectasis, Cystic Fibrosis & Restrictive Lung Disease 5.11 Evaluation of Cough, Dyspnea, Hemoptysis & the Solitary Pulmonary Nodule
7 Chapter 6: Rheumatology & Orthopedics (9% of Exam)
6.1 Rheumatoid Arthritis: Diagnosis & Systemic Manifestations 6.2 Antirheumatic Pharmacotherapy & the Spondyloarthropathies 6.3 Gout: Pathophysiology & Acute Management 6.4 Urate-Lowering Therapy & Calcium Pyrophosphate Deposition Disease 6.5 Osteoarthritis 6.6 Systemic Lupus Erythematosus 6.7 Systemic Sclerosis, Sjogren Syndrome & Inflammatory Myopathies 6.8 The Vasculitides 6.9 Regional Musculoskeletal Syndromes, Back Pain & Sports Injuries 6.10 Other Primary Rheumatic Disorders & Mixed Connective Tissue Disease 6.11 Osteonecrosis & Metabolic Bone Disease
8 Chapter 7: Hematology (6% of Exam)
7.1 Approach to Anemia & the Microcytic Anemias 7.2 Macrocytic, Normocytic & Hemolytic Anemias 7.3 Hemoglobinopathies, Thalassemias & Paroxysmal Nocturnal Hemoglobinuria 7.4 Platelet Disorders, Thrombocytopenia & the Bleeding Patient 7.5 Coagulation Factor Disorders, Thrombophilia & Anticoagulant Reversal 7.6 Acute Leukemias, Chronic Leukemias & Myeloproliferative Neoplasms 7.7 Lymphomas & Plasma Cell Disorders 7.8 Myelodysplastic Syndrome, Myeloproliferative Neoplasms & Porphyria 7.9 Transfusion Medicine & Late Complications of Transplantation
9 Chapter 8: Medical Oncology (6% of Exam)
8.1 Breast, Lung, Colorectal & Prostate Cancer 8.2 Oncologic Emergencies 8.3 Genitourinary & Gynecologic Malignancies 8.4 Head and Neck, Bone & Soft Tissue Cancer and Cancer of Unknown Primary 8.5 Complications of Cancer & Its Treatment 8.6 Cancer Prevention, Survivorship & Psychosocial Care
10 Chapter 9: Nephrology & Urology (6% of Exam)
9.1 Acute Kidney Injury: Staging, Etiology & Urine Microscopy 9.2 Glomerular Disorders & Nephrotic Syndrome 9.3 Nephritic Syndromes, RPGN & Indications for Renal Replacement Therapy 9.4 Chronic Kidney Disease: Staging & Progression Retardation 9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis 9.6 Hyponatremia, Hypernatremia & Water Balance 9.7 Potassium Disorders & Systematic Acid-Base Analysis 9.8 Renal Tubular Acidosis & Nephrolithiasis 9.9 Prostate Disorders, Urinary Incontinence & Other Urologic Conditions 9.10 Cystic Kidney Disease, Obstructive Uropathy, Tubulointerstitial Disease & Hematuria
11 Chapter 10: Neurology (4% of Exam)
10.1 Acute Ischemic Stroke: Syndromes & Reperfusion 10.2 Transient Ischemic Attack, Secondary Prevention & Hemorrhagic Stroke 10.3 Headache & Facial Pain 10.4 Seizures, Epilepsy & Movement Disorders 10.5 Multiple Sclerosis & Neuromuscular Junction Disorders 10.6 Motor Neuron Disease & Acute Peripheral Neuropathy 10.7 Cranial Neuropathies & Neuro-Ophthalmology 10.8 Peripheral Neuropathies, CNS Tumors & Other Neurologic Disorders
12 Chapter 11: Psychiatry & Behavioral Health (4% of Exam)
11.1 Major Depressive Disorder & Medical Mimics 11.2 Antidepressant Pharmacotherapy & Treatment-Resistant Depression 11.3 Bipolar Disorder, Mood Stabilizers & Lithium Toxicity 11.4 Anxiety, Stress-Related & Obsessive-Compulsive Disorders 11.5 Alcohol Use Disorder & Withdrawal 11.6 Pharmacotherapy for Alcohol & Opioid Use Disorder 11.7 Toxidromes, Psychiatric Emergencies & Suicide Risk Assessment 11.8 Psychotic, Somatic Symptom, Factitious & Personality Disorders 11.9 Eating Disorders, Sleep Disorders & Sexual Health
13 Chapter 12: Dermatology (3% of Exam)
12.1 Dermatitis, Papulosquamous & Inflammatory Dermatoses 12.2 Acne, Rosacea & Cutaneous Infections 12.3 Herpes Zoster & Autoimmune Blistering Diseases 12.4 Nodules, Tumors & Cutaneous Oncology 12.5 Dermatologic Emergencies & Severe Cutaneous Adverse Reactions 12.6 Pigment Disorders, Alopecia, Nail Disease & Photosensitivity 12.7 Vascular Dermatoses, Environmental Injury & Cutaneous Signs of Systemic Disease
14 Chapter 13: Obstetrics & Gynecology / Women's Health (3% of Exam)
13.1 Contraception, Preconception Care & Teratogenicity 13.2 Hypertensive Disorders of Pregnancy & Gestational Diabetes 13.3 Thyroid Disease & Venous Thromboembolism in Pregnancy 13.4 Menopause & Menopausal Hormone Therapy 13.5 Abnormal Uterine Bleeding, Endometrial Disease & Gynecologic Cancer Screening 13.6 Breast Disorders & Diseases of the Vulva and Vagina 13.7 Menstrual Disorders, Fibroids, Endometriosis & Early Pregnancy Complications
15 Chapter 14: Geriatric Syndromes (3% of Exam)
14.1 Comprehensive Geriatric Assessment & Frailty 14.2 Falls, Gait Assessment & Polypharmacy 14.3 Urinary Incontinence & Pressure Injuries in Older Adults 14.4 Mild Cognitive Impairment, Dementia & Its Subtypes 14.5 Delirium & the Pharmacotherapy of Cognitive Disorders 14.6 Palliative Care, Hospice & Advance Care Planning 14.7 Chronic Wounds, Nutrition, Swallowing, Constipation & Hip Fracture 14.8 Sensory Impairment, Dizziness, Elder Mistreatment & Care Settings
16 Chapter 15: Allergy & Immunology (2% of Exam)
15.1 Anaphylaxis: Recognition & Emergency Management 15.2 Urticaria & Angioedema 15.3 Drug Allergy, Desensitization & Adult Immunodeficiency 15.4 Food Allergy, Insect Venom Hypersensitivity, Serum Sickness & Contrast Reactions 15.5 Rhinitis, Conjunctivitis, Eosinophilic & Mast Cell Disorders
17 Chapter 16: Preventive Medicine, Immunization & Clinical Epidemiology
16.1 The USPSTF Framework & Evidence-Based Cancer Screening 16.2 Cardiovascular & Metabolic Screening and Primary Prevention 16.3 Adult Immunization & Vaccines in Special Populations 16.4 Clinical Epidemiology, Biostatistics & Study Design
18 Chapter 17: Miscellaneous - Ethics, Patient Safety & Quality Improvement (2% of Exam)
17.1 Principles of Bioethics & Decisional Capacity 17.2 Informed Consent, Treatment Refusal & Special Scenarios 17.3 Surrogate Decision-Making, Advance Directives & Confidentiality 17.4 Patient Safety Science, Medical Error & Diagnostic Reasoning 17.5 Quality Improvement Methods, Health Disparities & Health Equity
19 Chapter 18: Perioperative Medicine & Medical Consultation
18.1 Preoperative Cardiovascular Risk Assessment 18.2 Preoperative Pulmonary Risk & Perioperative Medication Management 18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications
20 Chapter 19: Ophthalmology (1% of Exam)
19.1 The Acute Red Eye & Ophthalmic Emergencies 19.2 Painless Vision Loss & Chronic Ophthalmic Disease 19.3 Uveitis, Scleritis & Orbital Disease
21 Chapter 20: Otolaryngology & Dental Medicine (1% of Exam)
20.1 Dizziness, Vertigo & Epistaxis 20.2 Ear Disorders, Hearing Loss & Upper Respiratory Infections 20.3 Oral Cavity, Salivary Gland, Laryngeal & Taste and Smell Disorders
5.9 Pleural Disease, Empyema & Pneumothorax
Key Takeaways Explain This Topic AI
Non-infectious pleural effusion, infections of the pleural space with empyema, and pneumothorax are the three enumerated pleural blueprint topics.
Light criteria classify an effusion as exudative if any one of the protein or lactate dehydrogenase thresholds is met.
Pleural fluid pH below 7.20, glucose below 60 mg/dL, or positive Gram stain or culture indicates a complicated effusion requiring chest tube drainage.
Frank pus in the pleural space defines empyema and requires drainage regardless of chemistry results.
Tension pneumothorax is a clinical diagnosis treated with immediate needle decompression before any confirmatory imaging.
Last updated: August 2026
Light's Criteria for Exudative Effusion
A pleural effusion is classified as an EXUDATE if it meets AT LEAST ONE of the following three criteria:
- Pleural Fluid Total Protein / Serum Total Protein ratio > 0.5
- Pleural Fluid LDH / Serum LDH ratio > 0.6
- Pleural Fluid LDH > 2/3 the Upper Limit of Normal (ULN) for the laboratory's serum LDH reference range
(If all 3 criteria are absent, the effusion is definitively a TRANSUDATE; sensitivity for exudate is ~98%).
The "Pseudoexudate" in Diuresed Heart Failure
In patients with congestive heart failure who receive aggressive loop diuretic therapy, water is cleared from the pleural space faster than protein and LDH, concentrating the pleural fluid and falsely fulfilling Light's criteria for an exudate in ~20% of cases.
To identify a pseudoexudate, calculate the Serum-to-Pleural Fluid Albumin Gradient : Gradient = Serum Albumin − Pleural Fluid Albumin \text{Gradient} = \text{Serum Albumin} - \text{Pleural Fluid Albumin} Gradient = Serum Albumin − Pleural Fluid Albumin
If the Albumin Gradient > 1.2 g/dL (or Serum Total Protein - Pleural Total Protein > 3.1 g/dL ), the effusion is confirmed to be a transudate secondary to heart failure, and invasive workup for exudative causes can be avoided.
Etiologic Classification & Diagnostic Pleural Fluid Patterns
Effusion Category Etiologies Pleural Fluid Characteristics & Diagnostic Pearls
Transudates Congestive Heart Failure, Cirrhosis (hepatic hydrothorax — usually right-sided), Nephrotic syndrome, Peritoneal dialysis, Hypoalbuminemia. Clear/straw-colored, low protein, low LDH, normal glucose (>60 mg/dL), normal pH (>7.30), low cell count (<1000/mcL).
Parapneumonic & Empyema Bacterial pneumonia ( S. pneumoniae , S. aureus , Klebsiella, anaerobes). Turbid/purulent, elevated neutrophils (>10,000/mcL). Classified as uncomplicated, complicated, or empyema (see below).
Malignancy Lung adenocarcinoma, metastatic breast cancer, lymphoma, ovarian carcinoma, mesothelioma. Serosanguinous/bloody, lymphocytic predominance (>50%), positive cytology (~60% yield first thoracentesis, ~75% second); low glucose/pH indicates extensive tumor burden and poor pleurodesis success.
Tuberculosis Mycobacterium tuberculosis pleurisy. Straw/amber fluid, marked lymphocytic predominance (>80%) , elevated Adenosine Deaminase (ADA > 40 U/L) , elevated interferon-gamma; pleural fluid AFB smear has low yield (<10%), pleural biopsy yield >85%.
Rheumatoid Pleuritis Severe longstanding Rheumatoid Arthritis. Markedly low glucose (<30 mg/dL or undetectable) , very high LDH (>1000 IU/L), low pH (<7.20), elevated rheumatoid factor (>1:320), cholesterol crystals.
Esophageal Rupture (Boerhaave) Transmural distal esophageal tear post-emesis. Elevated pleural amylase (salivary origin) , marked acidosis ( pH < 6.00 ), squamous epithelial cells, food particles.
Pancreatitis Acute or chronic pancreatitis, pseudocyst. Markedly elevated pleural amylase (pancreatic isoenzyme > serum) , exudate, left-sided predominance.
Chylothorax Thoracic duct disruption (lymphoma > trauma / thoracic surgery). Milky/opalescent fluid, Pleural Triglycerides > 110 mg/dL (if 50–110 mg/dL, presence of chylomicrons on lipoprotein electrophoresis confirms diagnosis).
Hemothorax Thoracic trauma, vascular disruption, aortic dissection, iatrogenic. Frank blood, Pleural Fluid Hematocrit > 50% of peripheral blood hematocrit . (Requires immediate large-bore tube thoracostomy).
1. Parapneumonic Effusions and Empyema
Parapneumonic effusions develop in up to 40% of patients hospitalized with bacterial pneumonia and require immediate risk stratification to determine the necessity of tube thoracostomy.
Three-Tier Staging & Management Protocol
Uncomplicated Parapneumonic Effusion:
Pleural Fluid Findings: Clear/turbid fluid, pH > 7.20 , Glucose > 60 mg/dL , LDH < 1000 IU/L , negative Gram stain and culture.
Management: Systemic IV Antibiotics alone . Does not require tube drainage; resolves with treatment of the underlying pneumonia.
Complicated Parapneumonic Effusion:
Pathogenesis: Direct bacterial invasion of the pleural space, leading to accelerated anaerobic glycolysis (producing lactic acid) and neutrophil lysis.
Pleural Fluid Findings: pH < 7.20 , Glucose < 60 mg/dL , LDH > 1000 IU/L , +/- positive Gram stain or culture, loculations/septations on ultrasound.
Management: Prompt Tube Thoracostomy (Chest Tube Drainage) + Systemic IV Antibiotics . Antibiotic penetration into an undrained acidic pleural space is inadequate; delaying drainage leads to extensive pleural organization, trapping, and high mortality.
Empyema:
Pleural Fluid Findings: Frank, visible pus in the pleural space, or presence of visible bacteria on Gram stain or bacterial growth on culture.
Management: Immediate Tube Thoracostomy + IV Antibiotics .
Management of Loculated / Non-Draining Pleural Infection
If chest tube drainage is incomplete due to thick fibrinous loculations and multi-septated fluid:
Intrapleural Fibrinolytic and Enzyme Therapy (MIST-2 Trial): Combination of intrapleural tissue Plasminogen Activator (tPA 10 mg) PLUS recombinant human Deoxyribonuclease (DNase 5 mg) administered twice daily via the chest tube for 3 days (6 doses total). The landmark MIST-2 trial demonstrated that tPA + DNase significantly improves radiographic pleural clearance, reduces the requirement for surgical decortication, and shortens hospital stay (neither agent alone was effective).
If intrapleural tPA/DNase fails or thick pleural peel creates a trapped lung: Video-Assisted Thoracoscopic Surgery (VATS) decortication .
- 2. Pneumothorax: Classification & Emergency Triage
- Primary Spontaneous Pneumothorax (PSP)
Etiology: Rupture of apical subpleural blebs or bullae in patients without underlying lung disease . Classic patient is a tall, thin young male (15–34 years) with a history of cigarette smoking.
Management:
Small (<2–3 cm rim at apex / <2 cm at hilum) and clinically stable: High-flow supplemental oxygen (increases pleural nitrogen washout, accelerating air reabsorption by 4-fold) and observation for 4–6 hours with repeat chest radiograph before discharge.
Large (>=2–3 cm) or symptomatic: Simple needle aspiration (16–18G angiocatheter) or small-bore (<=14F) chest tube / pigtail catheter.
Recurrent PSP: VATS pleurodesis (mechanical/talc) and apical wedge resection.
Secondary Spontaneous Pneumothorax (SSP)
Etiology: Occurs in patients with known underlying lung disease (COPD/emphysema bullae, Pneumocystis jirovecii pneumonia [PJP], cystic fibrosis, necrotizing bacterial pneumonia, lymphangioleiomyomatosis [LAM]).
Management: Because patients have limited pulmonary reserve, SSP is potentially life-threatening. Tube thoracostomy (chest tube drainage) is required for virtually all patients regardless of size, followed by definitive pleurodesis.
Tension Pneumothorax: Emergency Resuscitation
Pathophysiology: A one-way "ball-valve" mechanism allows air to enter the pleural space during inspiration but prevents egress during expiration -> intrapleural pressure exceeds atmospheric pressure throughout the respiratory cycle -> ipsilateral total lung collapse -> mediastinal and tracheal shift to the contralateral side -> compression of the superior/inferior vena cava and right atrium -> catastrophic reduction in venous return -> obstructive shock, electromechanical dissociation (PEA), and death .
Clinical Signs: Severe respiratory distress, cyanosis, hypotension, tachycardia, tracheal deviation AWAY from the affected hemithorax , unilateral absent breath sounds , and hyperresonance to percussion .
EMERGENCY ACTION RULE: Tension pneumothorax is a PURELY CLINICAL DIAGNOSIS. NEVER DELAY TREATMENT TO OBTAIN A CHEST RADIOGRAPH .
Immediate Intervention: Emergent Needle Decompression using a large-bore (14–16 gauge, >=5 cm length) angiocatheter inserted into the 2nd intercostal space in the midclavicular line or the 4th/5th intercostal space in the anterior axillary line on the affected side. Decompression immediately converts tension pneumothorax into a simple open pneumothorax and must be followed immediately by definitive Tube Thoracostomy (chest tube insertion) .