Harrison's Principles of Internal Medicine

Citation

Loscalzo, J., Fauci, A. S., Kasper, D. L., Hauser, S. L., Longo, D. L., Jameson, J. L., Holland, S. M., & Langford, C. A. (Eds.). (2025). Harrison's Principles of Internal Medicine (22nd ed., Vols. 1–2). McGraw Hill.

Chapter Summary

The 22nd edition is a two-volume work of roughly 4,000 pages, with 505 chapters in 20 parts. The publisher says the edition was modified extensively in structure and content and uses a standardized format for each disease chapter. Many parts are further divided into numbered sections.

Part 1: The Profession of Medicine (Chapters 1–13)

The opening part covers "The Practice of Medicine", promoting good health, vaccine opposition and hesitancy, decision-making in clinical medicine, precision medicine, screening and prevention, safety and quality of health care, "The Value of the Physical Examination in Modern Medicine", physician well-being, diagnostic error, racial and ethnic disparities, ethical issues, and palliative and end-of-life care.

Part 2: Cardinal Manifestations and Presentation of Diseases (Chapters 14–70)

A symptom-first part in nine sections: pain (including chest discomfort, abdominal pain, headache and back pain), alterations in body temperature, nervous system dysfunction (syncope, dizziness, weakness, coma, dementia, sleep disorders), eyes, ears, nose and throat, circulatory and respiratory functions (dyspnea, cough, edema, palpitations, exercise intolerance), gastrointestinal, renal and urinary, skin, and hematologic alterations.

Parts 3–4: Pharmacology; Oncology and Hematology (Chapters 71–123)

Two chapters on clinical pharmacology and pharmacogenomics come first. Oncology and hematology then follow in three sections: neoplastic disorders (Chapters 73–100), hematopoietic disorders (101–119) and disorders of hemostasis (120–123).

Part 5: Infectious Diseases (Chapters 124–242)

The largest part, divided into many sections. It begins with the approach to the patient with an infectious disease, microbial pathogenesis and genomics, then clinical syndromes, therapy for bacterial diseases, and organism groups from gram-positive and gram-negative bacteria through mycobacteria, spirochetes, viruses, fungi, protozoa and helminths.

Parts 6–8: Disorders of the Cardiovascular System; Respiratory System; Critical Care Medicine (Chapters 243–318)

Cardiovascular disorders are arranged in five sections from introduction and diagnosis (physical examination, electrocardiography, imaging, catheterization) through rhythm disorders, heart, muscle, valve and pericardial disease, to coronary and peripheral vascular disease. The respiratory part divides into diagnosis and diseases, and critical care covers respiratory critical care, shock and cardiac arrest, and nervous system disorders in critical care.

Parts 9–11: Kidney and Urinary Tract; Gastrointestinal System; Immune-Mediated, Inflammatory, and Rheumatologic Disorders (Chapters 319–387)

The kidney part runs from the approach to the patient and kidney physiology through acute kidney injury, chronic kidney disease, dialysis and transplantation to glomerular, tubulointerstitial and inherited disease. The gastrointestinal part has sections on the alimentary tract, nutrition, liver and biliary disease, and the pancreas. The immune part moves from the immune system in health and disease to immune-mediated injury and disorders of the joints.

Parts 12–13: Endocrinology and Metabolism; Neurologic Disorders (Chapters 388–468)

Endocrinology and metabolism includes endocrinology, sex- and gender-based medicine, obesity, diabetes mellitus and metabolic syndrome, bone and mineral disorders, and intermediary metabolism. Neurologic disorders begin with diagnosis and neuroimaging, then central nervous system disease, nerve and muscle disorders, myalgic encephalomyelitis/chronic fatigue syndrome, and psychiatric and addiction disorders.

Parts 14–19: Poisoning; Environmental Exposures; Genes, the Environment, and Disease; Global Medicine; Aging; Consultative Medicine (Chapters 469–492)

A group of shorter parts: heavy metals, drug overdose and envenomation; altitude, diving, cold and heat injury and the health effects of climate change; principles of human genetics, gene and cell therapy and the microbiome; global health and emerging infections; the biology of aging and care of the geriatric patient; and medical consultation, medical disorders during pregnancy and evaluation before non-cardiac surgery.

Part 20: Emerging Topics in Clinical Medicine (Chapters 493–505)

Thirteen chapters on newer areas: point-of-care ultrasound, behavioral economics, complementary and integrative therapies, placebo and nocebo effects, epigenetics, circadian biology, network medicine, emerging neurotherapeutics, machine learning and augmented intelligence, metabolomics, circulating nucleic acids as liquid biopsies, protein folding disorders, and approaches to diseases of unknown etiology.

Key Concepts

Parts 1–4

• Cardinal manifestations: chapters organized by presenting symptom, intended to link the physiology of a symptom to the diseases that cause it.
• Decision-making and diagnosis: chapters on clinical decision-making and on reducing diagnostic error (Chapters 4 and 10).
• Precision medicine and screening (Chapters 5–6), pharmacogenomics (Chapter 72).

Parts 5–20

• Approach to the patient: the opening chapter of many parts (Chapters 124, 243, 295, 311, 319, 332, 388, 433).
• Differential diagnosis schemas and decision trees: the publisher stresses clear schemas for building a differential diagnosis, along with algorithms and diagnostic trees.
• Emerging methods: network medicine, metabolomics and machine learning in Part 20.

Critical Analysis

Strengths

• Symptom-first access. Part 2 lets a reader start from a presenting complaint such as dyspnea, syncope or fever of unknown origin and move to the disease chapters, so the book can be entered from the bedside problem as well as from the diagnosis.
• Consistent disease format and visual support. The publisher cites a standardized disease-chapter format, more than 3,000 clinical, pathological and radiographic photographs, decision trees and schematics, and curated atlases.
• Mechanisms alongside management. The publisher presents the book as a source on applied pathophysiology that also covers specific treatment regimens and current guidelines.
• Breadth beyond single organs. Parts on genes and the environment, global medicine, aging and emerging topics extend the scope past organ-based disease chapters.

Limitations

• Very large. About 4,000 pages across two volumes and 505 chapters make it a reference for consultation, not a text to be read through.
• A new structure. Because the structure was modified extensively in this edition, notes or page references from earlier editions will not carry over directly.
• Many contributors. Most chapters name specific authors, so style and depth differ across parts, as in any multi-author reference.
• Emerging topics are not core. Part 20 is useful for orientation, but most of its chapters go beyond what a clinical course will examine.

Where It Fits in the Course

Harrison's is one of two large reference works on the clinical medicine list, alongside Goldman-Cecil Medicine. Both cover adult internal medicine in full. Harrison's puts cardinal manifestations in a dedicated early part and has 505 chapters in 20 parts, whereas Goldman-Cecil runs 409 chapters in 30 parts organized by specialty. Neither is a first book.

Beginners start smaller. Clinical Medicine: Lecture Notes is a concise guide for students starting on the wards, organized around history, examination and diagnosis. Macleod's Clinical Examination teaches the history and examination skills. Davidson's Principles and Practice of Medicine is a one-volume textbook of internal medicine and the more practical first pass. The Oxford Handbook of Medical Sciences summarizes the scientific foundations. Harrison's belongs after these, as the deeper source for mechanisms and for differential diagnosis from a symptom.

How to Use This Book

The book is for readers who have completed preclinical sciences (pathology, pharmacology, physiology): clinical students, residents and practising physicians.

• Begin with Part 1 (especially Chapters 4, 8 and 10) for reasoning and the physical examination.
• Use Part 2 for presenting problems: pick the symptom, read the chapter, then follow it to the organ-system part.
• Read the approach chapter first in each system part, then the specific disease chapters.
• Treat Part 5 as reference, starting with Chapters 124 and 127 on approaching an infected, febrile patient.
• Dip into Parts 16 and 20 for genetics and newer methods when a topic comes up.
• Check the date of guideline-based sections against current guidance.