Study guide
3.3 Inflammatory Bowel Disease
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
3.3 Inflammatory Bowel Disease
Key Takeaways Explain This Topic AI
Crohn disease including Crohn colitis is enumerated under small intestinal disease, while ulcerative colitis is enumerated under colonic and anorectal disease.
Ulcerative colitis is continuous and mucosal from the rectum proximally; Crohn disease is skip-lesion, transmural and may involve any segment from mouth to anus.
Corticosteroids are induction agents only, and a patient requiring repeated steroid courses needs a steroid-sparing maintenance agent.
Latent tuberculosis and hepatitis B must be excluded before starting anti-tumor necrosis factor therapy.
Primary sclerosing cholangitis is associated chiefly with ulcerative colitis and independently increases colorectal cancer risk, mandating more frequent surveillance colonoscopy.
Last updated: August 2026
Intestinal and colorectal disorders tested on the ABIM examination encompass inflammatory bowel disease, malabsorptive enteropathies, functional bowel disorders, diverticular disease, and evidence-based colorectal cancer screening.
- 1. Inflammatory Bowel Disease (IBD)
- Crohn Disease vs. Ulcerative Colitis
Clinical / Pathologic Feature Crohn Disease (CD) Ulcerative Colitis (UC)
Anatomic Distribution Anywhere from mouth to anus ; terminal ileum involved in 70–80%; rectum is frequently spared . Confined to colon only ; begins in rectum and extends contiguously/proximally ; pancolitis in ~20%.
Pattern of Inflammation Discontinuous ("skip lesions") with normal intervening mucosa. Continuous and uniform mucosal erythema and ulceration without skip areas.
Depth of Mural Involvement Transmural (mucosa to serosa), leading to sinus tracts, fistulas, and strictures. Mucosal and submucosal only (does not extend through muscularis propria unless toxic megacolon).
Macroscopic Appearance Cobblestone mucosa , deep linear/serpiginous "knife-like" fissures, aphthous ulcers, creeping mesenteric fat. Diffuse erythema, granularity, friability, superficial mucosal ulcerations, inflammatory pseudopolyps .
Histopathology Noncaseating granulomas (pathognomonic, present in ~30%), transmural lymphoid aggregates. Crypt abscesses (neutrophils in crypt lumens), crypt architectural distortion, mucin depletion; no granulomas.
Clinical Complications Fistulas (enterocutaneous, enterovesical, perianal), strictures/bowel obstruction, perianal abscesses/skin tags. Toxic megacolon , severe hemorrhage, fulminant colitis, colonic perforation.
Serologic Markers ASCA positive (anti- Saccharomyces cerevisiae antibodies; ~60%), p-ANCA negative. p-ANCA positive (perinuclear antineutrophil cytoplasmic antibodies; ~70%), ASCA negative.
Smoking Association Smoking worsens disease course and increases recurrence. Smoking appears protective (ex-smokers have increased risk/severity).
Extraintestinal Manifestations (EIMs)
Activity Parallels Luminal Bowel Inflammation:
Erythema Nodosum: Tender, red, subcutaneous nodules on pretibial surfaces (correlates with flare; resolves with IBD control).
Peripheral Arthritis (Type 1 Pauciarticular): Asymmetric, large joint involvement (<5 joints; resolves with IBD control).
Episcleritis: Scleral injection, burning, and irritation without vision loss.
Aphthous Stomatitis: Painful oral mucosal ulcers.
Activity Independent of Luminal Bowel Inflammation:
Pyoderma Gangrenosum: Violaceous, undermined, necrotizing cutaneous ulcers with ragged borders (most common on shins). Critical clinical rule: Do NOT surgically debride due to pathergy (worsening of ulcer); treat with systemic corticosteroids or anti-TNF therapy (Infliximab).
Ankylosing Spondylitis & Sacroiliitis: Strongly associated with HLA-B27 ; causes chronic inflammatory lower back pain and morning stiffness; progresses independently of IBD.
Uveitis: Deep ocular pain, photophobia, headache, and blurred vision; requires immediate ophthalmology evaluation and topical/systemic steroids.
Primary Sclerosing Cholangitis (PSC): Autoimmune cholestatic destruction of intra/extrahepatic bile ducts; 70–80% of PSC patients have coexisting UC. Progresses independently of colectomy.
Metabolic & Malabsorptive Complications (Predominantly Crohn Disease):
Nephrolithiasis (Calcium Oxalate Stones): Terminal ileal inflammation/resection impairs bile acid resorption, leading to unabsorbed luminal fatty acids that bind calcium. Free unchelated oxalate is hyperabsorbed in the colon, producing enteric hyperoxaluria and calcium oxalate kidney stones.
Gallstones (Cholesterol Stones): Interruption of the enterohepatic circulation of bile salts causes bile to become supersaturated with cholesterol.
Macrocytic Anemia: Vitamin B12 deficiency due to terminal ileal disease/resection.
Toxic Megacolon Crisis Management
Toxic Megacolon is a life-threatening, non-obstructive colonic dilatation (transverse colon diameter > 6 cm >6\text{ cm} > 6 cm on abdominal radiograph/CT) accompanied by systemic toxicity.
Jalan Diagnostic Criteria: Radiographic colonic dilation > 6 cm >6\text{ cm} > 6 cm PLUS at least 3 of:
- Fever > 38.6 ∘ C >38.6^\circ\text{C} > 38. 6 ∘ C ( > 101.5 ∘ F >101.5^\circ\text{F} > 101. 5 ∘ F )
- Tachycardia > 120 bpm >120\text{ bpm} > 120 bpm
- Leukocytosis > 10 , 500 / μ L >10,500/\mu\text{L} > 10 , 500/ μ L with left shift
- Anemia
PLUS at least 1 sign of systemic toxicity: Dehydration, altered mental status, electrolyte abnormalities, or hypotension.
Emergency Management Protocol:
Complete bowel rest (NPO) and Nasogastric (NG) tube decompression .
Aggressive IV fluid resuscitation and correction of hypokalemia/hypomagnesemia (hypokalemia worsens colonic atony).
Discontinue all antimotility agents (narcotics, anticholinergics, loperamide, diphenoxylate-atropine).
Initiate IV Broad-Spectrum Antibiotics (e.g., Ceftriaxone + Metronidazole or Piperacillin-tazobactam) to prevent sepsis from bacterial translocation.
Initiate High-Dose IV Corticosteroids (Methylprednisolone 60 mg IV daily or Hydrocortisone 100 mg IV q8h).
Urgent Colorectal Surgery Consultation: If no clinical improvement within 24 to 72 hours , or if peritonitis, colonic perforation, or worsening necrosis develops, immediate Subtotal Colectomy with End Ileostomy is mandatory.
Loading diagram... IBD & Celiac Diagnostic and Cancer Surveillance Algorithm
Medical Pharmacotherapy for IBD Step-Up Approach: 5-ASA (UC) ➔ Corticosteroids (Induction Only) ➔ Immunomodulators / Biologics / Small Molecules (Maintenance)
5-Aminosalicylates (5-ASAs):
Oral Mesalamine (2.4–4.8 g/day) and Topical Mesalamine (rectal suppository 1 g daily for proctitis; rectal enema 4 g daily for left-sided colitis). First-line for induction and maintenance of mild-to-moderate UC. (Minimal to no efficacy in Crohn disease).
Sulfasalazine: Requires supplemental Folic Acid (1 mg daily) due to inhibition of dihydrofolate reductase.
Corticosteroids:
Oral Prednisone (40–60 mg daily), IV Methylprednisolone (60 mg daily), or Oral Budesonide (9 mg daily; ileocecal-release for mild-to-moderate ileal/right-colon CD, or Budesonide MMX for UC). Budesonide has extensive first-pass hepatic metabolism (~90%), resulting in fewer systemic glucocorticoid side effects.
Core ABIM Rule: Corticosteroids are used for INDUCTION OF REMISSION ONLY . They must NEVER be used for maintenance therapy due to lack of mucosal healing and high risks of osteoporosis, avascular necrosis, cataracts, and opportunistic infections.
Immunomodulators (Thiopurines):
Azathioprine (2.0–2.5 mg/kg/day) and 6-Mercaptopurine (6-MP) (1.0–1.5 mg/kg/day).
Mandatory Pre-Treatment Testing: Measure Thiopurine Methyltransferase (TPMT) and NUDT15 enzymatic activity or genotype. Patients with homozygous deficiency accumulate cytotoxic 6-thioguanine nucleotides (6-TGN), causing fatal bone marrow aplasia and severe leukopenia.
Adverse effects: Pancreatitis (dose-independent), hepatotoxicity, myelosuppression, and increased long-term risk of non-Hodgkin lymphoma and non-melanoma skin cancer .
Biologics & Targeted Small Molecules:
Anti-TNF Agents: Infliximab (IV), Adalimumab (SQ), Golimumab (SQ), Certolizumab pegol (SQ). First-line for moderate-to-severe IBD.
Anti-Integrin: Vedolizumab (monoclonal antibody targeting α 4 β 7 \alpha_4\beta_7 α 4 β 7 integrin, blocking leukocyte homing selectively to the gut mucosa; gut-specific mechanism with lower risk of systemic immunosuppression/infections).
Anti-IL-12/23 & Anti-IL-23: Ustekinumab (targets p40 subunit of IL-12 and IL-23), Risankizumab , and Mirikizumab (targets p19 subunit of IL-23).
JAK Inhibitors (Oral): Tofacitinib , Upadacitinib (indicated for moderate-to-severe UC and CD; black box warnings for major adverse cardiovascular events [MACE], thrombosis, and serious infections; administer recombinant zoster vaccine prior to initiation).
S1P Receptor Modulator (Oral): Ozanimod (sphingosine-1-phosphate receptor modulator; requires baseline EKG to rule out conduction abnormalities and baseline ophthalmologic exam to rule out macular edema).
Mandatory Pre-Biologic Screening: All patients initiating anti-TNF or advanced biologic/small molecule therapies must be screened for Latent Tuberculosis (Interferon-Gamma Release Assay [IGRA] / T-Spot or TST + Chest Radiograph) and Hepatitis B (HBsAg, Anti-HBc total, Anti-HBs).
Colorectal Cancer Surveillance in IBD
Initiation of Surveillance: Perform high-definition colonoscopy with chromoendoscopy (using methylene blue or indigo carmine dye spray with targeted biopsies) starting 8 years after the onset of symptoms in patients with pancolitis or left-sided colitis (disease extending proximal to the rectum).
Special Exception for Concomitant PSC: In patients with coexisting Primary Sclerosing Cholangitis (PSC) , surveillance colonoscopy must begin immediately at the time of PSC diagnosis , regardless of IBD disease duration.
Surveillance Frequency: Repeat colonoscopy every 1 to 2 years thereafter.