16.5 Gastrointestinal & Hepatobiliary Infections: Fulminant C. difficile, Typhlitis, CMV Colitis & Abscesses

ABIM Critical Care Medicine Study Guide Exam

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1 Chapter 1: Exam Orientation: Format, Blueprint & Study Strategy

1.1 ABIM Critical Care Medicine Exam: Format, Blueprint & Study Strategy

2 Chapter 2: Acute Respiratory Failure & ARDS

2.1 ARDS Definition, Pathophysiology & Phenotypes 2.2 Lung-Protective Mechanical Ventilation 2.3 Refractory ARDS: Prone Positioning, Neuromuscular Blockade & VV-ECMO

3 Chapter 3: Obstructive Airways, Pulmonary Vascular & Pleural Emergencies

3.1 Severe Asthma & COPD Exacerbations in the ICU 3.2 Massive & Submassive Pulmonary Embolism 3.3 Pulmonary Hypertension & Right Ventricular Failure in the ICU 3.4 Massive Hemoptysis, Complex Pleural Effusions & Thoracic Drainage

4 Chapter 4: Airway, Parenchymal & Nonthrombotic Pulmonary Emergencies

4.1 Airway Management, Upper-Airway Obstruction & Artificial-Airway Complications 4.2 Diffuse Alveolar Hemorrhage, Interstitial Lung Disease, Pulmonary Vasculitis & Noncardiogenic Edema 4.3 Severe Community-Acquired & Viral Pneumonia 4.4 Nonthrombotic Embolism (Air, Fat, Amniotic Fluid, Tumor, Septic) & Acute Chest Syndrome

5 Chapter 5: Mechanical Ventilation Modes, Dyssynchrony & Liberation

5.1 Mechanical Ventilator Modes & Advanced Breath Delivery 5.2 Patient-Ventilator Dyssynchrony & Waveform Analysis 5.3 Ventilator Liberation, Spontaneous Breathing Trials & Post-Extubation Support

6 Chapter 6: Shock Syndromes & Hemodynamic Principles

6.1 Shock Classification, Cellular Pathophysiology & Biomarkers 6.2 Hemodynamic Monitoring: Arterial Lines, CVP & Pulmonary Artery Catheter 6.3 Dynamic Assessment of Fluid Responsiveness & Resuscitation Targets

7 Chapter 7: Vasoactive Therapies & Mechanical Circulatory Support

7.1 Vasopressors & Inotropes: Pharmacology & Clinical Titration 7.2 Temporary Mechanical Circulatory Support: IABP, Impella & TandemHeart 7.3 Venoarterial ECMO (VA-ECMO) & Differential Hypoxemia 7.4 Post-Cardiac Arrest Care, Targeted Temperature Management & Neuroprognostication

8 Chapter 8: Acute Kidney Injury & Renal Replacement Therapy

8.1 KDIGO AKI Classification, Etiologies & Diagnostic Evaluation 8.2 Continuous Renal Replacement Therapy (CRRT) vs Intermittent Hemodialysis 8.3 Indications & Timing for RRT in Critical Illness: AKIKI & STARRT-AKI

9 Chapter 9: Electrolyte, Acid-Base & Endocrine Emergencies

9.1 Severe Dysnatremias: Hyponatremia, Hypernatremia & Osmotic Demyelination 9.2 Potassium, Calcium, Magnesium & Phosphate Disorders 9.3 Complex & Mixed Acid-Base Disorders: Boston vs Copenhagen vs Stewart 9.4 Endocrine Crises: DKA, HHS, Thyroid Storm, Myxedema Coma & Adrenal Crisis

10 Chapter 10: Glycemic Control, Hyperammonemia, Pituitary & Adrenal Disorders

10.1 ICU Glycemic Control & Severe Hypoglycemia 10.2 Non-Hepatic Hyperammonemia & Metabolic Encephalopathy 10.3 Pituitary Emergencies, Adrenal Excess & Critical Illness-Related Corticosteroid Insufficiency

11 Chapter 11: Acute Coronary Syndromes & Cardiac Arrhythmias

11.1 Acute Coronary Syndromes & Mechanical Complications of Myocardial Infarction 11.2 Critical Tachyarrhythmias: Atrial Fibrillation with RVR, VT & VF 11.3 Critical Bradyarrhythmias, Conduction Blocks & Temporary Cardiac Pacing

12 Chapter 12: Acute Heart Failure, Valvular & Pericardial Emergencies

12.1 Acute Decompensated Heart Failure & Cardiogenic Pulmonary Edema 12.2 Acute Valvular Regurgitation & Prosthetic Valve Emergencies 12.3 Pericardial Tamponade & Acute Aortic Syndromes

13 Chapter 13: Myocardial Disease, Hypertensive & Cardiac Device Emergencies

13.1 Fulminant Myocarditis, Stress & Peripartum Cardiomyopathy, and Hypertrophic Cardiomyopathy 13.2 Hypertensive Emergencies & Ruptured Abdominal Aortic Aneurysm 13.3 Implanted Cardiac Devices, LVAD Emergencies & Electrical Storm

14 Chapter 14: Sepsis & Systemic Infectious Diseases

14.1 Sepsis-3 Definitions & Surviving Sepsis Campaign 2026 Guidelines 14.2 Refractory Septic Shock & Adjunctive Therapies 14.3 Multidrug-Resistant Pathogens & Antimicrobial Stewardship in the ICU

15 Chapter 15: ICU-Acquired & Severe Focal Infections

15.1 Hospital-Acquired & Ventilator-Associated Pneumonia 15.2 Central Line-Associated Bloodstream Infections & Catheter-Associated UTIs 15.3 Intra-Abdominal Sepsis, Necrotizing Soft Tissue Infections & CNS Infections

16 Chapter 16: Focal, Special-Host & Systemic Infections

16.1 CNS Infections Beyond Bacterial Meningitis: Encephalitis, Brain Abscess & Epidural Abscess 16.2 Infections in the Immunocompromised Host, Tropical & Bioterror Infections 16.3 Infective Endocarditis, Device Infections & Other Focal Cardiovascular Infections 16.4 Antimicrobial Pharmacokinetics, Allergy, Toxicity & Infection Prevention 16.5 Gastrointestinal & Hepatobiliary Infections: Fulminant C. difficile, Typhlitis, CMV Colitis & Abscesses

17 Chapter 17: Neurocritical Care & Coma

17.1 Coma, Altered Mental Status & Acute Delirium in the ICU 17.2 Status Epilepticus & Non-Convulsive Status Epilepticus 17.3 Acute Ischemic Stroke & Intracranial Hemorrhage

18 Chapter 18: Cerebrovascular Syndromes, Encephalopathy & Withdrawal States

18.1 Cerebral Venous Sinus Thrombosis, PRES & Reversible Cerebral Vasoconstriction Syndrome 18.2 Alcohol & Sedative Withdrawal, Wernicke Encephalopathy & Drug-Induced Encephalopathy

19 Chapter 19: Intracranial Hypertension & Neuromuscular Weakness

19.1 Intracranial Pressure Monitoring, Cerebral Perfusion & Tiered ICP Management 19.2 Acute Neuromuscular Respiratory Failure, ICU-Acquired Weakness & Brain Death Determination

20 Chapter 20: Traumatic Brain Injury, Spinal Cord Injury & Toxin-Mediated Paralysis

20.1 Traumatic Brain Injury Management & Paroxysmal Sympathetic Hyperactivity 20.2 Acute Spinal Cord Injury, Neurogenic Shock & Autonomic Dysreflexia 20.3 Toxin-Mediated Paralysis & Neuromuscular Crises: Botulism, Tetanus, Tick Paralysis & Myasthenic Crisis

21 Chapter 21: Gastrointestinal, Hepatic & Abdominal Emergencies

21.1 Acute Upper & Lower Gastrointestinal Bleeding in the ICU 21.2 Acute Liver Failure & Severe Acute Pancreatitis 21.3 Abdominal Compartment Syndrome & Acute Mesenteric Ischemia

22 Chapter 22: Luminal GI Emergencies & Complications of Cirrhosis

22.1 Esophageal, Gastric & Bowel Emergencies: Perforation, Obstruction, Ogilvie Syndrome & Colonic Ischemia 22.2 Complications of Cirrhosis: Alcohol-Associated Hepatitis, Hepatorenal Syndrome & Pulmonary Vascular Syndromes

23 Chapter 23: Trauma, Burns & Perioperative Critical Care

23.1 Polytrauma Resuscitation, Damage Control & Massive Transfusion 23.2 Severe Burn Injury, Inhalation Injury & Environmental Emergencies 23.3 Perioperative Critical Care for High-Risk Surgical Patients

24 Chapter 24: Thoracic Trauma, Environmental Injury & Obstetric Critical Care

24.1 Thoracic Trauma: Flail Chest, Pulmonary Contusion, Great Vessel & Tracheobronchial Injury 24.2 Environmental Injury: Drowning, Diving, Altitude, Heat, Cold, Electrical & Radiation 24.3 Obstetric & Genitourinary Emergencies and the Physiology of Pregnancy

25 Chapter 25: Transplantation, Donor Management & Post-Cardiac Surgery Care

25.1 Solid Organ Transplant Recipients & Deceased Donor Management 25.2 Post-Cardiac Surgery Critical Care: Bleeding, Tamponade, Low Output & Vasoplegia

26 Chapter 26: Hematologic Emergencies, Toxicology, Critical Ultrasound & ICU Liberation

26.1 Hematologic Emergencies in the ICU: HIT, DIC, TMA & Anticoagulant Reversal 26.2 Critical Care Toxicology, Toxidromes & Specific Antidotes 26.3 Critical Care Point-of-Care Ultrasound (POCUS) 26.4 ICU Liberation, Analgosedation, Goals of Care & Critical Care Ethics

27 Chapter 27: Transfusion Medicine, Hematologic & Oncologic Disorders

27.1 Transfusion Medicine: Products, Thresholds, Reactions & Apheresis 27.2 Red and White Cell Disorders, Hemoglobinopathies, Factor Deficiencies & Hypercoagulable States 27.3 Oncologic Emergencies, Hematopoietic Cell Transplant Complications & Cellular Therapy Toxicity

28 Chapter 28: Clinical Pharmacology, Adverse Drug Reactions & Specific Poisonings

28.1 Pharmacokinetic Principles, Dose Adjustment & Drug Interactions in Critical Illness 28.2 Adverse Drug Reactions: Anaphylaxis, Severe Cutaneous Reactions & Hyperthermic Syndromes 28.3 Specific Poisonings: Sodium-Channel Blockers, Lithium, Valproate, Theophylline, Iron, Sulfonylureas & Methemoglobinemia

29 Chapter 29: Ethics, Research Methods, Administration & Abdominal Ultrasound

29.1 Advance Care Planning, Nonbeneficial Treatment, Informed Consent & Confidentiality 29.2 Critical Care Research Methods, Statistics, IRB Oversight & Quality Improvement 29.3 Abdominal, Vascular & Procedural Point-of-Care Ultrasound

16.5 Gastrointestinal & Hepatobiliary Infections: Fulminant C. difficile, Typhlitis, CMV Colitis & Abscesses

Key Takeaways Explain This Topic AI

Fulminant Clostridioides difficile infection is treated with vancomycin 500 mg four times daily enterally plus intravenous metronidazole 500 mg every 8 hours, with rectal vancomycin added when ileus is present.

Surgical options for fulminant C. difficile infection are subtotal colectomy with end ileostomy, or diverting loop ileostomy with colonic lavage, and should be considered before multiorgan failure is established.

Neutropenic enterocolitis (typhlitis) is managed medically with bowel rest, broad-spectrum antibiotics covering gram-negative bacteria and anaerobes, and surgery only for perforation or uncontrolled bleeding.

Spontaneous bacterial peritonitis is diagnosed by an ascitic neutrophil count of at least 250 cells/µL and is treated with a third-generation cephalosporin plus albumin 1.5 g/kg then 1 g/kg on day 3.

Amebic liver abscess is usually a single right-lobe lesion treated with metronidazole plus a luminal agent, without drainage unless it is very large, left-lobed, or fails to respond.

Last updated: October 2026

Fulminant Clostridioides difficile Infection

Severity grading :

Non-severe : white cell count below 15,000/µL and creatinine below 1.5 mg/dL.

Severe : white cell count of 15,000/µL or more, or creatinine of 1.5 mg/dL or more.

Fulminant : hypotension or shock, ileus , or toxic megacolon .

Clues in the ICU : a very high white cell count (sometimes above 40,000/µL), a rising lactate, paradoxically absent diarrhea when ileus develops, abdominal distension with a dilated colon on imaging (a transverse colon diameter above 6 cm), and marked hypoalbuminemia from protein-losing colopathy.

Treatment of fulminant disease :

Vancomycin 500 mg enterally four times daily (oral or by nasogastric tube).

Plus intravenous metronidazole 500 mg every 8 hours .

Plus rectal vancomycin (500 mg in 100 mL saline as a retention enema every 6 hours) when ileus prevents enteral delivery.

Fidaxomicin is preferred for non-fulminant disease (it lowers recurrence) but has less data in fulminant disease.

Stop the inciting antibiotic if possible, avoid antimotility agents, and avoid proton pump inhibitors where feasible.

Bezlotoxumab reduces recurrence in selected high-risk patients; fecal microbiota-based therapy is for recurrent, not fulminant, disease.

Surgery : involve surgery early. Options are subtotal colectomy with end ileostomy or diverting loop ileostomy with colonic lavage and antegrade vancomycin . Indications include perforation, megacolon, worsening organ failure, and failure of medical therapy; operating after multiorgan failure is established carries very high mortality. A rising lactate (above about 5 mmol/L) and a white cell count above 50,000/µL mark poor prognosis.

Neutropenic Enterocolitis (Typhlitis)

Host : profound neutropenia after induction chemotherapy, typically 1 to 2 weeks after cytotoxic therapy.

Presentation : fever, right lower quadrant pain, diarrhea (sometimes bloody), and distension. Mortality is high.

Imaging : CT shows cecal and ascending colon wall thickening (above about 4 mm), pericolic fat stranding, and sometimes pneumatosis.

Management is medical : bowel rest, nasogastric decompression if obstructed, intravenous fluid, and broad-spectrum antibiotics covering enteric gram-negative bacteria, anaerobes, and Pseudomonas (piperacillin-tazobactam or a carbapenem). Add antifungal therapy for persistent fever. Transfuse for cytopenias; G-CSF is often used to accelerate recovery.

Avoid antimotility agents, routine colonoscopy (perforation risk), and rectal examinations.

Surgery is reserved for perforation, uncontrolled bleeding, or clinical deterioration despite maximal therapy. Distinguish it from C. difficile colitis and from appendicitis.

CMV Colitis and Other Viral Gastrointestinal Disease

Host : transplant recipients, advanced HIV, and patients on steroids or biologics; CMV also complicates severe ulcerative colitis.

Presentation : diarrhea (often bloody), abdominal pain, fever, and sometimes perforation or massive bleeding.

Diagnosis : endoscopy with biopsy showing inclusion bodies and positive immunohistochemistry ; blood CMV PCR can be negative in isolated gastrointestinal disease.

Treatment : intravenous ganciclovir (then valganciclovir), reduce immunosuppression where possible, and monitor for neutropenia. Foscarnet for resistant or ganciclovir-intolerant disease.

Other causes: norovirus outbreaks in units, adenovirus in transplant recipients, HSV esophagitis, and Candida esophagitis in immunocompromised hosts.

Liver and Biliary Infections

Condition Features Management

Pyogenic liver abscess Fever, right upper quadrant pain, elevated alkaline phosphatase; polymicrobial from biliary or portal sources; Klebsiella pneumoniae invasive syndrome (often with metastatic infection including endophthalmitis) Percutaneous drainage plus antibiotics (a beta-lactam-beta-lactamase inhibitor or a cephalosporin plus metronidazole) for 4 to 6 weeks; look for a colonic source

Amebic liver abscess Travel or residence in an endemic area; usually a single right-lobe lesion ; positive Entamoeba histolytica serology; "anchovy paste" contents without organisms Metronidazole (or tinidazole) plus a luminal agent (paromomycin); drainage only for very large lesions, left-lobe lesions threatening pericardial rupture, uncertain diagnosis, or failure to improve

Acute cholangitis Charcot triad (fever, jaundice, right upper quadrant pain); Reynolds pentad adds hypotension and confusion Antibiotics plus urgent biliary decompression (ERCP, or percutaneous transhepatic drainage)

Acute cholecystitis and acalculous cholecystitis Acalculous disease occurs in critically ill, fasting patients on vasopressors or parenteral nutrition; ultrasound shows wall thickening, sludge, and pericholecystic fluid Antibiotics plus percutaneous cholecystostomy in patients who cannot tolerate surgery

Infected pancreatic necrosis Usually after the first week; gas in the collection, clinical deterioration Antibiotics with good pancreatic penetration (carbapenem, or a fluoroquinolone plus metronidazole) and a step-up approach : percutaneous or endoscopic drainage first, then minimally invasive necrosectomy; delay intervention beyond about 4 weeks when possible. Prophylactic antibiotics for sterile necrosis are not recommended

Spontaneous bacterial peritonitis Cirrhosis with ascites; fever, pain, encephalopathy, or kidney injury, sometimes without symptoms Diagnostic paracentesis with an ascitic neutrophil count of 250 cells/µL or more ; third-generation cephalosporin plus albumin 1.5 g/kg on day 1 and 1 g/kg on day 3 to prevent kidney injury; secondary prophylaxis with norfloxacin or trimethoprim-sulfamethoxazole

Secondary bacterial peritonitis Polymicrobial, very high protein and LDH in ascites, low glucose; a perforation Imaging and surgical source control (antibiotics alone fail)

Other Intra-Abdominal Infections to Recognize

Diverticulitis with perforation : Hinchey III and IV disease needs operative management; abscesses larger than about 3 to 4 cm are drained percutaneously.

Emphysematous cholecystitis and pyelonephritis : gas-forming infection in diabetes, with high mortality; urgent drainage or surgery.

Appendicitis in the ICU : often delayed and perforated at presentation.

Ogilvie syndrome with colonic ischemia : distinguish mechanical obstruction from pseudo-obstruction before giving neostigmine.

Enteric fever and Yersinia : travel or ileocecal disease that mimics appendicitis.

Note

Any intra-abdominal infection that is not improving within 48 to 72 hours of appropriate antibiotics implies inadequate source control . Reimage and reintervene rather than broadening antibiotics reflexively.