Internal Medicine 2026: A Comprehensive Clinical Textbook: Pathophysiology, Diagnosis, Pharmacotherapy and Hospital Medicine – An Evidence-Based Guide for Physicians, Residents and Medical Students

Table of Contents

Preface .............................................................. iii
How to Use This Textbook ................................. v
Chapter Architecture ..................................... v
Recurring Elements........................................ v
Drug Names and Dosing................................. v
Guidelines and Evidence............................... vi
Procedural Content....................................... vi
The Clinical Method and Diagnostic Reasoning
.........................................................................14
1.1 Introduction ..........................................14
1.2 The Structure of the Clinical Encounter 14
1.2.1 The History .....................................15
1.2.2 The Physical Examination...............15
1.3 Generating and Refining the Differential
Diagnosis......................................................16
1.3.1 Illness Scripts..................................16
1.3.2 Must-Not-Miss Diagnoses..............17
1.4 Diagnostic Testing and Bayesian
Reasoning.....................................................17
1.5 Cognitive Biases in Diagnosis................18
1.6 High-Risk Clinical Situations..................20
1.7 The Clinical Record................................20
Evidence-Based Medicine and Critical Appraisal
.........................................................................23
2.1 Evidence-Based Medicine: Definition and
Practice ........................................................23
2.2 The Hierarchy of Evidence ....................23
2.3 Appraising a Randomized Controlled Trial
.....................................................................24
2.3.1 Internal Validity.............................. 25
2.3.2 External Validity............................. 25
2.3.3 Effect Size and Precision ................ 25
2.4 Systematic Reviews and Meta-Analyses
..................................................................... 26
2.5 Patient-Centered Application ............... 26
Principles of Pharmacotherapy in Adult
Medicine.......................................................... 28
3.1 Introduction.......................................... 28
3.2 Pharmacokinetics.................................. 28
3.2.1 Absorption and Bioavailability....... 28
3.2.2 Distribution.................................... 29
3.2.3 Metabolism.................................... 29
3.2.4 Elimination..................................... 30
3.3 Dose Adjustment in Organ Dysfunction30
3.3.1 Renal Impairment .......................... 30
3.3.2 Hepatic Impairment....................... 31
3.4 Special Populations............................... 31
3.4.1 The Older Adult.............................. 31
3.4.2 Pregnancy and Lactation................ 32
3.5 Medication Reconciliation and
Deprescribing............................................... 32
3.6 Therapeutic Drug Monitoring ............... 33
Heart Failure .................................................... 36
4.1 Epidemiology and Clinical Importance . 36
4.2 Classification ......................................... 36
4.3 Pathophysiology.................................... 37
4.3.1 HFrEF.............................................. 37
4.3.2 HFpEF ............................................. 38
4.4 Clinical Presentation ............................. 38 Textbook of Internal Medicine 2026
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4.5 Diagnostic Evaluation............................39
4.5.1 Natriuretic Peptides.......................39
4.5.2 Echocardiography...........................39
4.5.3 Evaluation for Coronary Disease....40
4.6 Chronic Pharmacotherapy: The Four
Pillars of HFrEF .............................................40
4.6.1 ARNI, ACE Inhibitors, and ARBs......41
4.6.2 Beta-Blockers .................................41
4.6.3 Mineralocorticoid Receptor
Antagonists ..............................................41
4.6.4 SGLT2 Inhibitors.............................42
4.6.5 Adjunctive Therapies......................42
4.7 Acute Decompensated Heart Failure....42
4.7.1 Initial Assessment ..........................42
4.7.2 Diuresis...........................................43
4.7.3 Vasodilators....................................43
4.7.4 Inotropes........................................44
4.8 Device Therapy and Advanced Heart
Failure ..........................................................44
4.9 Transitions of Care and Self-Management
.....................................................................45
Acute Coronary Syndromes and Chronic
Coronary Disease .............................................47
5.1 Epidemiology and Classification............47
5.2 Pathophysiology....................................47
5.3 Clinical Presentation .............................48
5.4 Diagnostic Approach .............................49
5.4.1 Electrocardiography .......................49
5.4.2 Cardiac Biomarkers........................49
5.5 STEMI Management..............................49
5.5.1 Initial Medical Therapy...................49
5.6 NSTEMI Management........................... 50
5.7 Secondary Prevention........................... 51
5.8 Chronic Coronary Disease..................... 51
Arrhythmias and Conduction Disorders.......... 53
6.1 Electrophysiologic Foundations............ 53
6.2 Bradyarrhythmias and Conduction
Disease......................................................... 54
6.2.1 Sinus Node Dysfunction................. 54
6.2.2 Atrioventricular Block .................... 54
6.2.3 Temporary and Permanent Pacing 55
6.3 Supraventricular Tachycardias.............. 55
6.3.1 Atrial Fibrillation ............................ 55
6.3.2 Atrial Flutter................................... 57
6.3.3 Paroxysmal Supraventricular
Tachycardia.............................................. 57
6.4 Ventricular Tachyarrhythmias .............. 57
6.4.1 Monomorphic Ventricular
Tachycardia.............................................. 57
6.4.2 Polymorphic Ventricular Tachycardia
and Torsades de Pointes.......................... 57
6.5 Cardiac Arrest ....................................... 58
Hypertension, Valvular Disease, and Venous
Thromboembolism .......................................... 59
7.1 Hypertension ........................................ 59
7.1.1 Definition and Classification .......... 59
7.1.2 Epidemiology and Impact .............. 59
7.1.3 Evaluation ...................................... 59
7.1.4 Non-Pharmacologic Management. 60
7.1.5 Pharmacologic Management......... 60
7.1.6 Hypertensive Emergency and
Urgency.................................................... 61 Textbook of Internal Medicine 2026
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7.2 Valvular Heart Disease ..........................62
7.2.1 Aortic Stenosis................................62
7.2.2 Mitral Regurgitation.......................62
7.2.3 Aortic and Mitral Regurgitation of
Acute Onset..............................................62
7.2.4 Endocarditis....................................63
7.3 Venous Thromboembolism...................63
7.3.1 Epidemiology and Risk ...................63
7.3.2 Diagnosis........................................63
7.3.3 Risk Stratification in Acute PE ........63
7.3.4 Treatment ......................................63
7.3.5 Advanced Therapies in PE ..............64
Asthma and Chronic Obstructive Pulmonary
Disease .............................................................67
8.1 Airway Obstruction: A Shared Framework
.....................................................................67
8.2 Asthma ..................................................67
8.2.1 Pathophysiology.............................68
8.2.2 Diagnosis........................................68
8.2.3 Classification and Control ..............68
8.2.4 Chronic Pharmacotherapy .............68
8.2.5 Biologics for Severe Asthma...........69
8.2.6 Acute Exacerbation ........................70
8.3 Chronic Obstructive Pulmonary Disease
.....................................................................71
8.3.1 Epidemiology and Pathophysiology
.................................................................71
8.3.2 Diagnosis and Staging ....................71
8.3.3 Chronic Pharmacotherapy .............71
8.3.4 Non-Pharmacologic Interventions.72
8.3.5 Acute Exacerbation ........................72
Pneumonia and Pulmonary Infections ............ 75
9.1 Classification and Epidemiology ........... 75
9.2 Community-Acquired Pneumonia ........ 75
9.2.1 Microbiology .................................. 75
9.2.2 Diagnosis........................................ 76
9.2.3 Severity Assessment and Disposition
................................................................. 76
9.2.4 Empirical Antibiotic Therapy.......... 77
9.3 Hospital-Acquired and Ventilator-
Associated Pneumonia ................................ 78
9.4 Aspiration Pneumonia .......................... 79
9.5 Tuberculosis and Non-Tuberculous
Mycobacteria............................................... 79
9.6 Pneumonia in the Immunocompromised
Host.............................................................. 79
Respiratory Failure and the Acute Respiratory
Distress Syndrome........................................... 82
10.1 Classification of Respiratory Failure ... 82
10.2 The Five Causes of Hypoxemia ........... 82
10.3 Acute Respiratory Distress Syndrome 83
10.3.1 Definition and Pathophysiology... 83
10.3.2 Causes.......................................... 84
10.3.3 Management................................ 84
10.3.4 Ventilator Management .............. 85
10.4 Non-Invasive Ventilation .................... 85
10.5 High-Flow Nasal Oxygen ..................... 85
10.6 Invasive Mechanical Ventilation......... 86
10.6.1 Indications and Mode Selection .. 86
10.6.2 Sedation and Analgesia................ 86
10.6.3 Weaning and Liberation............... 86 Textbook of Internal Medicine 2026
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Gastrointestinal Bleeding and Inflammatory
Bowel Disease ..................................................89
11.1 Upper Gastrointestinal Bleeding.........89
11.1.1 Etiology.........................................89
11.1.2 Initial Management......................89
11.1.3 Pharmacologic Therapy................90
11.1.4 Endoscopy ....................................90
11.1.5 Variceal Bleeding..........................90
11.2 Lower Gastrointestinal Bleeding.........91
11.3 Inflammatory Bowel Disease ..............91
11.3.1 Ulcerative Colitis ..........................91
11.3.2 Crohn Disease...............................92
11.3.3 Pharmacotherapy.........................92
11.3.4 Acute Severe Ulcerative Colitis....93
Acute Pancreatitis, Peptic Ulcer Disease, and
GERD ................................................................95
12.1 Acute Pancreatitis...............................95
12.1.1 Epidemiology and Etiology...........95
12.1.2 Diagnosis and Severity .................95
12.1.3 Management................................96
12.2 Peptic Ulcer Disease............................96
12.2.1 Pathophysiology...........................96
12.2.2 Clinical Presentation and Diagnosis
.................................................................97
12.2.3 Treatment ....................................97
12.3 Gastroesophageal Reflux Disease .......97
Cirrhosis and Acute Liver Injury .......................99
13.1 Cirrhosis...............................................99
13.1.1 Diagnosis and Severity Scoring ....99
13.1.2 Ascites and Spontaneous Bacterial
Peritonitis...............................................100
13.1.3 Hepatic Encephalopathy............ 100
13.1.4 Hepatorenal Syndrome.............. 101
13.1.5 Hepatocellular Carcinoma
Surveillance............................................ 101
13.2 Liver Transplantation........................ 101
13.3 Acute Liver Injury.............................. 101
13.3.1 Acetaminophen Hepatotoxicity. 101
13.3.2 Viral Hepatitis ............................ 102
13.3.3 Alcohol-Associated Liver Disease
............................................................... 102
Acute Kidney Injury and Chronic Kidney Disease
....................................................................... 105
14.1 Acute Kidney Injury........................... 105
14.1.1 Definition and Staging................ 105
14.1.2 Causes........................................ 105
14.1.3 Evaluation .................................. 106
14.1.4 Management.............................. 107
14.2 Chronic Kidney Disease..................... 107
14.2.1 Definition and Staging................ 107
14.2.2 Slowing Progression................... 108
14.2.3 Complications of CKD................. 108
14.2.4 Renal Replacement Therapy...... 109
Acid-Base and Electrolyte Disorders.............. 110
15.1 Acid-Base Interpretation................... 110
15.1.1 Metabolic Acidosis..................... 111
15.1.2 Metabolic Alkalosis.................... 111
15.1.3 Respiratory Disorders................ 111
15.2 Sodium Disorders.............................. 111
15.2.1 Hyponatremia ............................ 111
15.2.2 Hypernatremia........................... 112 Textbook of Internal Medicine 2026
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15.3 Potassium Disorders..........................112
15.3.1 Hyperkalemia .............................112
15.3.2 Hypokalemia ..............................113
15.3.3 Calcium, Phosphate, and Magnesium
...................................................................113
Diabetes and Its Complications......................117
16.1 Classification and Epidemiology........117
16.2 Diagnosis...........................................117
16.3 Glycemic Management .....................117
16.3.1 Targets........................................117
16.3.2 Type 1 Diabetes..........................118
16.3.3 Type 2 Diabetes..........................118
16.3.4 GLP-1 Receptor Agonists and Dual
Agonists..................................................119
16.4 Acute Complications .........................119
16.4.1 Diabetic Ketoacidosis.................119
16.4.2 Hyperosmolar Hyperglycemic State
...............................................................120
16.5 Hypoglycemia....................................120
16.6 Inpatient Glycemic Management......120
16.7 Chronic Complications ......................121
Thyroid, Adrenal, and Pituitary Disorders......123
17.1 Thyroid Disease.................................123
17.1.1 Hyperthyroidism ........................123
17.1.2 Thyroid Storm ............................124
17.1.3 Hypothyroidism..........................124
17.1.4 Myxedema Coma .......................124
17.2 Adrenal Disease.................................124
17.2.1 Adrenal Insufficiency..................124
17.2.2 Adrenal Crisis..............................125
17.2.3 Cushing Syndrome and
Pheochromocytoma .............................. 125
17.3 Pituitary Disease ............................... 125
17.3.1 Pituitary Adenomas ................... 125
17.3.2 Hypopituitarism......................... 126
Anemia, Thrombocytopenia, and Bleeding
Disorders........................................................ 129
18.1 Anemia.............................................. 129
18.1.1 Classification .............................. 129
18.1.2 Iron Deficiency Anemia.............. 130
18.1.3 Anemia of Chronic Disease ........ 130
18.1.4 Macrocytic Anemia .................... 130
18.1.5 Hemolytic Anemia...................... 131
18.2 Thrombocytopenia ........................... 131
18.2.1 Approach.................................... 131
18.2.2 Heparin-Induced
Thrombocytopenia ................................ 131
18.2.3 Thrombotic Thrombocytopenic
Purpura .................................................. 132
18.3 Bleeding Disorders............................ 132
18.3.1 Evaluation .................................. 132
18.3.2 Hemophilia and von Willebrand
Disease................................................... 132
18.3.3 Coagulopathy in the Hospitalized
Patient.................................................... 132
18.4 Transfusion Medicine ....................... 133
18.4.1 Transfusion Reactions................ 133
Oncologic Emergencies.................................. 135
19.1 Febrile Neutropenia.......................... 136
19.2 Tumor Lysis Syndrome...................... 136
19.3 Hypercalcemia of Malignancy........... 136 Textbook of Internal Medicine 2026
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19.4 Spinal Cord Compression ..................137
19.5 Superior Vena Cava Syndrome..........137
19.6 Immune-Related Adverse Events......137
19.7 Cytokine Release Syndrome and
Neurotoxicity .............................................138
Sepsis and Bloodstream Infections................140
20.1 Defining Sepsis: The Sepsis-3
Framework.................................................140
20.1.1 Pathophysiology.........................140
20.2 The Hour-1 Bundle ............................141
20.2.1 Empiric Antimicrobial Therapy...142
20.3 Resuscitation and Hemodynamic
Support ......................................................143
20.3.1 Vasopressor Selection................143
20.3.2 Corticosteroids...........................144
20.4 Source Control...................................144
20.5 Bloodstream Infections.....................145
20.5.1 Staphylococcus aureus Bacteremia
...............................................................145
20.5.2 Gram-Negative Bacteremia........145
20.5.3 Infective Endocarditis.................146
20.5.4 Catheter-Related Bloodstream
Infection.................................................146
20.5.5 Candidemia ................................147
20.6 Sepsis Supportive Care......................147
Antimicrobial Stewardship and Common
Pathogens ......................................................150
21.1 Principles of Antimicrobial Stewardship
...................................................................150
21.2 Beta-Lactam Antibiotics....................151
21.2.1 Beta-Lactam Allergy ...................152
21.3 Non–Beta-Lactam Agents for Gram-
Positive Infection ....................................... 153
21.4 Multidrug-Resistant Gram-Negatives153
21.4.1 ESBL-Producing Enterobacterales
............................................................... 153
21.4.2 AmpC Producers........................ 154
21.4.3 Carbapenem-Resistant Organisms
............................................................... 154
21.5 Clostridioides difficile Infection ........ 155
21.6 Urinary Tract Infection...................... 156
21.7 Skin and Soft Tissue Infection........... 156
21.8 Meningitis......................................... 157
21.9 Additional Common Pathogens........ 158
21.9.1 Influenza .................................... 158
21.9.2 HIV-Associated Opportunistic
Infection................................................. 158
21.9.3 Tick-Borne Disease..................... 158
Rheumatologic Emergencies and Acute
Inflammatory Disease.................................... 162
22.1 Approach to the Patient with Acute
Inflammatory Disease................................ 162
22.2 Giant Cell Arteritis............................. 162
22.3 ANCA-Associated Vasculitis.............. 163
22.4 Other Vasculitides............................. 164
22.5 Septic Arthritis vs. Crystal Arthritis... 164
22.6 Systemic Lupus Erythematosus ........ 166
22.7 Antiphospholipid Syndrome ............. 167
22.8 Inflammatory Myopathy................... 167
22.9 Spondyloarthropathy........................ 167
22.10 Principles of Immunosuppressive
Therapy...................................................... 168 Textbook of Internal Medicine 2026
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Stroke, Seizures, and Altered Mental Status .170
23.1 Acute Ischemic Stroke.......................170
23.1.1 Initial Evaluation.........................171
23.1.2 Intravenous Thrombolysis..........171
23.1.3 Mechanical Thrombectomy .......172
23.1.4 Post-Thrombolysis and Post-
Thrombectomy Care ..............................172
23.1.5 Secondary Prevention................172
23.2 Intracerebral Hemorrhage ................173
23.3 Subarachnoid Hemorrhage ...............173
23.4 Seizures and Status Epilepticus.........174
23.5 Approach to Altered Mental Status..175
23.6 Delirium in the Hospitalized Adult....176
Shock, Mechanical Ventilation, and ICU
Sedation .........................................................179
24.1 Shock: A Unified Framework.............179
24.1.1 Hypovolemic Shock ....................180
24.1.2 Cardiogenic Shock ......................180
24.1.3 Obstructive Shock ......................180
24.1.4 Distributive Shock ......................180
24.2 Mechanical Ventilation .....................181
24.2.1 Modes of Ventilation .................181
24.2.2 Initial Settings.............................181
24.2.3 Lung-Protective Ventilation .......182
24.2.4 PEEP, Prone Positioning, and
Rescue Therapies...................................182
24.2.5 Ventilator Alarms and
Troubleshooting.....................................183
24.3 Sedation and Analgesia.....................183
24.4 Complications of Critical Illness ........184
24.5 Weaning and Liberation from
Mechanical Ventilation.............................. 184
24.6 Goals-of-Care and End-of-Life Care in
the ICU....................................................... 185
Bedside Procedures and Point-of-Care
Ultrasound..................................................... 188
25.1 The Universal Procedural Framework
................................................................... 188
25.2 Central Venous Catheterization........ 189
25.2.1 Indications and Site Selection.... 189
25.2.2 Technique: Ultrasound-Guided
Internal Jugular...................................... 189
25.2.3 Complications ............................ 189
25.3 Arterial Catheterization .................... 190
25.4 Thoracentesis.................................... 190
25.4.1 Technique .................................. 190
25.4.2 Pleural Fluid Analysis ................. 191
25.5 Paracentesis...................................... 192
25.6 Lumbar Puncture .............................. 193
25.6.1 Technique .................................. 193
25.6.2 Post-Dural Puncture Headache.. 194
25.7 Arthrocentesis................................... 195
25.8 Point-of-Care Ultrasound.................. 195
25.8.1 Cardiac POCUS ........................... 195
25.8.2 Lung POCUS ............................... 196
25.8.3 Integrated POCUS Protocols...... 196
25.9 Documentation and Handoff............ 196
Geriatric Medicine ......................................... 200
26.1 The Scope of Geriatric Medicine....... 200
26.2 Physiologic Aging .............................. 200
26.3 Functional Assessment ..................... 201 Textbook of Internal Medicine 2026
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26.4 Cognitive Assessment and Dementia202
26.5 Polypharmacy and Deprescribing .....203
26.6 Falls ...................................................204
26.7 Pressure Injury ..................................204
26.8 Urinary Incontinence.........................205
26.9 Hospital-Acquired Functional Decline
...................................................................205
Palliative Care and End-of-Life Medicine.......207
27.1 Palliative Care and Hospice...............207
27.2 Communication and Goals of Care ...207
27.3 Symptom Management ....................208
27.3.1 Pain.............................................208
27.3.2 Opioid Dosing and Conversion...209
27.3.3 Dyspnea......................................210
27.3.4 Nausea and Vomiting .................210
27.3.5 Constipation...............................211
27.3.6 Delirium at the End of Life .........211
27.4 Advance Care Planning......................211
27.5 Care of the Actively Dying Patient ....211
27.6 Hospice..............................................212
Perioperative Medicine..................................214
28.1 Preoperative Assessment..................214
28.2 Cardiac Risk Assessment...................214
28.3 Perioperative Beta-Blockade and Statins
...................................................................215
28.4 Perioperative Anticoagulation and
Antiplatelet Management..........................216
28.5 Perioperative VTE Prophylaxis..........217
28.6 Pulmonary Risk..................................217
28.7 Diabetes and Glycemic Management
...................................................................217
28.8 Other Specific Populations................ 218
28.9 Postoperative Complications............ 218
28.9.1 Myocardial Injury after Non-Cardiac
Surgery (MINS)....................................... 218
28.9.2 Postoperative Atrial Fibrillation. 219
28.9.3 Postoperative Ileus.................... 219
28.9.4 Postoperative Delirium.............. 219
Preventive Medicine and Health Maintenance
....................................................................... 222
29.1 The Framework of Prevention.......... 222
29.2 Screening: Principles and Pitfalls...... 222
29.3 Cancer Screening .............................. 223
29.3.1 Colorectal Cancer....................... 223
29.3.2 Breast Cancer............................. 224
29.3.3 Cervical Cancer .......................... 224
29.3.4 Lung Cancer ............................... 224
29.3.5 Prostate Cancer.......................... 225
29.4 Cardiovascular Prevention................ 225
29.4.1 Diabetes Prevention .................. 226
29.5 Adult Immunization .......................... 227
29.6 Behavioral Counseling ...................... 228
29.7 Obesity and Metabolic Health .......... 228
29.8 Preconception and Interconception
Health ........................................................ 229
Dermatology for the Internist........................ 231
30.1 The Internist and the Skin................. 231
30.2 Life-Threatening Cutaneous Drug
Reactions ................................................... 231
30.2.1 Stevens-Johnson Syndrome and
Toxic Epidermal Necrolysis.................... 232 Textbook of Internal Medicine 2026
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30.2.2 Drug Reaction with Eosinophilia
and Systemic Symptoms........................232
30.2.3 Acute Generalized Exanthematous
Pustulosis...............................................233
30.3 Skin and Soft-Tissue Infections .........234
30.3.1 Cellulitis and Erysipelas..............234
30.3.2 Necrotizing Soft-Tissue Infection
...............................................................235
30.3.3 Other Common Infections..........235
30.4 Inflammatory Dermatoses................235
30.5 Autoimmune Blistering Diseases ......236
30.6 Urticaria, Pruritus, and Angioedema 236
30.7 Cutaneous Manifestations of Systemic
Disease .......................................................237
30.8 Skin Cancer........................................238
Medical Toxicology and Environmental
Medicine ........................................................241
31.1 The General Approach to Poisoning .241
31.2 Acetaminophen.................................242
31.3 Salicylate ...........................................243
31.4 Tricyclic Antidepressants...................244
31.5 Beta-Blocker and Calcium Channel
Blocker Poisoning.......................................244
31.6 Digoxin ..............................................244
31.7 Opioids and Stimulants.....................245
31.8 Toxic Alcohols....................................245
31.9 Carbon Monoxide and Cyanide.........246
31.10 Envenomation.................................246
31.11 Hyperthermia and Hypothermia.....247
Allergy and Immunology ................................251
32.1 Anaphylaxis.......................................251
32.2 Drug Allergy ...................................... 252
32.2.1 Radiocontrast Reactions............ 253
32.3 Angioedema...................................... 253
32.4 Primary Immunodeficiency in the Adult
................................................................... 254
32.5 Biologic Therapy: Mechanisms and
Monitoring................................................. 254
32.6 Food Allergy ...................................... 256
32.7 Mast Cell Disorders........................... 256
Sleep Medicine for the Internist.................... 259
33.1 The Physiology and Importance of Sleep
................................................................... 259
33.2 Obstructive Sleep Apnea .................. 259
33.3 Central Sleep Apnea.......................... 261
33.4 Insomnia ........................................... 261
33.5 Restless Legs Syndrome and Periodic
Limb Movements....................................... 262
33.6 REM Sleep Behavior Disorder and
Parasomnias............................................... 262
33.7 Narcolepsy and Hypersomnolence... 263
Psychiatric Emergencies and Substance Use
Disorders........................................................ 266
34.1 The Internist and Psychiatric Care .... 266
34.2 Suicide Risk Assessment ................... 266
34.3 Acute Agitation ................................. 267
34.4 Serotonin Syndrome and Neuroleptic
Malignant Syndrome ................................. 268
34.5 Lithium Toxicity................................. 269
34.6 Alcohol Use Disorder and Withdrawal
................................................................... 269
34.7 Opioid Use Disorder.......................... 270 Textbook of Internal Medicine 2026
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34.8 Stimulant Use Disorder.....................271
34.9 Tobacco Use Disorder .......................271
34.10 Depression and Anxiety in the Medical
Patient........................................................271
HIV Medicine for the Internist .......................276
35.1 HIV in the Third Decade of Antiretroviral
Therapy ......................................................276
35.2 Pathophysiology and Natural History276
35.3 Diagnosis and Laboratory Monitoring
...................................................................277
35.4 Antiretroviral Therapy.......................278
35.5 Opportunistic Infections and
Prophylaxis.................................................279
35.6 Non-AIDS Comorbidities and Primary
Care............................................................281
35.7 Pre-exposure and Post-exposure
Prophylaxis.................................................281
Solid Organ Transplant Medicine for the
Internist..........................................................284
36.1 The Growing Transplant Population .284
36.2 Immunosuppression .........................284
36.3 Rejection ...........................................286
36.4 Post-Transplant Infections................286
36.5 Long-Term Management ..................287
36.6 Drug Interactions and Perioperative
Management..............................................288
Obstetric Medicine and Women's Health......291
37.1 The Internist in Women's Health and
Pregnancy...................................................291
37.2 Physiologic Adaptations of Pregnancy
...................................................................291
37.3 Hypertensive Disorders of Pregnancy
................................................................... 292
37.4 Venous Thromboembolism in
Pregnancy .................................................. 293
37.5 Diabetes in Pregnancy ...................... 293
37.6 Thyroid Disorders.............................. 294
37.7 Other Chronic Disease in Pregnancy. 294
37.8 Menopause and Hormone Therapy.. 295
37.9 Contraception................................... 295
37.10 Common Women's Health Issues for
the Internist............................................... 296
Travel Medicine and Tropical Infectious
Diseases......................................................... 300
38.1 The Pretravel Consultation ............... 300
38.2 Fever in the Returned Traveler......... 301
38.3 Malaria.............................................. 302
38.4 Enteric Fever..................................... 303
38.5 Arboviral Infections........................... 303
38.6 Rickettsial and Spirochetal Infections
................................................................... 304
38.7 Parasitic and Chronic Infections ....... 304
38.8 Tuberculosis and Emerging Infections
................................................................... 305
Ophthalmology and Otolaryngology for the
Internist ......................................................... 307
39.1 The Internist at the Interface............ 307
39.2 The Red Eye ...................................... 307
39.3 Acute Vision Loss.............................. 308
39.4 Ocular Manifestations of Systemic
Disease....................................................... 309
39.5 Dizziness and Vertigo........................ 309 Textbook of Internal Medicine 2026
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39.6 Hearing Loss and Tinnitus.................310
39.7 Rhinosinusitis and Sore Throat .........311
39.8 Epistaxis.............................................311
Health Systems, Quality, and Medical Ethics.314
40.1 Why This Chapter..............................314
40.2 The U.S. Health System.....................314
40.3 Quality and Safety.............................315
40.4 Medical Ethics...................................316
40.5 Common Ethical Challenges..............316
40.5.1 Refusal of Treatment .................316
40.5.2 Futility ........................................317
40.5.3 Disclosure of Error and Adverse
Events.....................................................317
40.5.4 Conflicts of Interest....................317
40.6 Physician Wellbeing ..........................317
Musculoskeletal Medicine and Sports Injuries
for the Internist..............................................321
41.1 Structured Musculoskeletal Assessment
...................................................................321
41.2 Shoulder Disorders.............................322
41.3 Elbow, Wrist, and Hand .....................323
41.4 Hip and Pelvis.....................................324
41.5 Knee ...................................................325
41.6 Ankle and Foot...................................326
41.7 Low Back Pain ....................................326
41.8 Osteoporosis and Bone Health ..........327
41.9 Sports Injuries and Return to Play .....328
Pain Medicine for the Internist......................331
42.1 Classification and Mechanisms of Pain
...................................................................331
42.2 Assessment and Measurement..........332
42.3 Multimodal Analgesia........................ 332
42.4 Opioid Therapy: Principles and Pitfalls
................................................................... 333
42.5 Neuropathic Pain Syndromes............ 335
42.6 Fibromyalgia and Nociplastic Pain..... 335
42.7 Cancer and End-of-Life Pain............... 335
42.8 Perioperative and Acute Pain
Management ............................................. 336
Nutrition and Obesity Medicine .................... 339
43.1 Nutritional Assessment...................... 339
43.2 Nutritional Requirements and Therapy
................................................................... 340
43.3 Micronutrient Deficiencies................ 340
43.4 Obesity as a Chronic Disease ............. 342
43.5 Pharmacotherapy of Obesity............. 342
43.6 Bariatric and Metabolic Surgery ........ 344
43.7 Dietary Patterns and Evidence-Based
Nutrition .................................................... 344
Normal Laboratory Reference Values ........... 348
A.1 Hematology ........................................ 348
A.2 Chemistry............................................ 349
A.3 Endocrinology..................................... 350
A.4 Arterial Blood Gas............................... 350
Drug Formulary for Common Inpatient
Conditions...................................................... 352
B.1 Cardiovascular .................................... 352
B.2 Antimicrobials (Common Empiric
Regimens) .................................................. 353
B.3 Gastroenterology, Endocrine, and Other
................................................................... 354
Clinical Formulas and Equations.................... 355 Textbook of Internal Medicine 2026
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C.1 Renal and Electrolyte ..........................355
C.2 Acid-Base.............................................355
C.3 Pulmonary...........................................355
C.4 Cardiovascular.....................................356
C.5 Hepatic and Infectious Disease...........356
C.6 Endocrine ............................................356
ACLS Algorithms.............................................358
D.1 Adult Cardiac Arrest: Shockable Rhythms
(VF/Pulseless VT) ....................................... 358
D.2 Adult Cardiac Arrest: Non-Shockable
Rhythms (Asystole, PEA)............................ 358
D.3 Bradycardia with a Pulse .................... 358
D.4 Tachycardia with a Pulse .................... 358
D.5 Post-Cardiac-Arrest Care .................... 359