33.3 Acute Nausea, Vomiting & Foodborne Illness

ABFM Family Medicine Certification Study Guide Exam

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1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

1.1 Exam Blueprint, FMCLA vs. One-Day Exam & Board Scoring 1.2 Clinical Reasoning, Test-Taking Strategy & Ambiguity Management 1.3 Evidence-Based Medicine & Clinical Practice Guidelines in Primary Care

2 Chapter 2: Healthcare Systems, Practice Management & Quality

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3 Chapter 3: Ethics, Law, Biostatistics & Health Equity

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4 Chapter 4: Lifestyle Counseling & Behavior Change

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5 Chapter 5: Nutrition, Physical Activity & Chronic Disease Prevention

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6 Chapter 6: Routine Adult Immunizations

6.1 ACIP Adult Respiratory Vaccines: Influenza, COVID-19, RSV & Pneumococcal 6.2 ACIP Adult Non-Respiratory Vaccines: Tdap, Shingrix, HPV & Hep B 6.3 Immunizations in Special Populations: Pregnancy, Asplenia & Immunocompromise

7 Chapter 7: Pediatric Health Maintenance & Surveillance

7.1 Newborn Examination & Early Postnatal Care 7.2 Well-Child Care, Developmental Surveillance & Milestones 7.3 Pediatric & Adolescent Screening: Vision, Hearing, Anemia & Lead 7.4 Pediatric Oral Health, Dental Screening & Fluoride

8 Chapter 8: Behavioral Health & Safety Screening

8.1 Primary Care Depression, Anxiety & Behavioral Health Screening 8.2 Domestic Violence, Intimate Partner Violence & Firearm Safety 8.3 Occupational Health & Recreational Safety Counseling

9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

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10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

10.1 Breast Cancer Screening & Risk-Assessment 10.2 Cervical Cancer Screening & ASCCP Algorithms 10.3 Skin Cancer Clinical Assessment & Counseling

11 Chapter 11: Adult Cancer Screening: Colorectal, Lung & Prostate

11.1 Colorectal Cancer Screening Modalities & Intervals 11.2 Lung Cancer Screening with Low-Dose CT 11.3 Prostate Cancer Screening & Shared Decision-Making

12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

12.1 Sexual Health Counseling & Risk-Reduction Strategies 12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis 12.3 Bloodborne Infectious Disease Screening: HIV & Hepatitis C

13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

13.1 Preconception Planning & Comprehensive Contraception Management 13.2 Lactation Support & Breastfeeding Counseling 13.3 Preoperative Medical Evaluation & Pre-Participation Sports Exam

14 Chapter 14: Emergent Cardiovascular Conditions

14.1 Acute Coronary Syndromes & Myocardial Infarction 14.2 Acute Chest Pain Risk Stratification & Triage 14.3 Acute or Critical Valvular Heart Emergencies

15 Chapter 15: Cardiac Arrhythmias, Heart Failure & Hypertensive Crises

15.1 Acute Atrial & Ventricular Arrhythmias 15.2 Acute Decompensated Heart Failure & Cardiogenic Shock 15.3 Hypertensive Emergency & Urgency Management

16 Chapter 16: Vascular & Thromboembolic Emergencies

16.1 Pulmonary Embolism & Deep Vein Thrombosis 16.2 Acute Aortic Syndromes & Peripheral Vascular Emergencies 16.3 Critical Limb Ischemia & Acute Arterial Occlusion

17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

17.1 Acute Ischemic Stroke & Intracranial Hemorrhage 17.2 Syncope Evaluation & Status Epilepticus 17.3 Acute Delirium, Encephalopathy & Severe Confusion

18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury 18.2 Thunderclap & Acute Severe Secondary Headaches 18.3 Acute Ophthalmologic Emergencies

19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

21.1 Major Trauma Resuscitation & Initial Assessment 21.2 Burn Assessment, Inhalation Injury & Resuscitation 21.3 Laceration Management, Complex Wounds & Animal Bites

22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

24.1 Diabetic Ketoacidosis & Hyperosmolar Hyperglycemic State 24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias 24.3 Severe Calcium Abnormalities & Acute Adrenal Crisis

25 Chapter 25: Hematologic, Urologic & Dental Emergencies

25.1 Severe Symptomatic Anemias & Coagulopathic Emergencies 25.2 Testicular Torsion, Priapism & Acute Urinary Retention 25.3 Urgent Odontogenic Infections & Dental Trauma

26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

27.1 Primary Acute Headaches: Migraine, Tension & Cluster 27.2 Concussion & Minor Closed Head Injury Evaluation 27.3 Transient Ischemic Attack Evaluation & ABCD2 Risk Scoring

28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

28.1 Peripheral Neuropathies: Bell's Palsy, Carpal Tunnel & Radiculopathy 28.2 Acute Tinnitus, Sudden Sensorineural Hearing Loss & Cerumen Impaction 28.3 Acute Dizziness, Benign Paroxysmal Positional Vertigo & Vestibular Neuritis

29 Chapter 29: Acute Upper Respiratory Tract Infections

29.1 Acute Viral Rhinosinusitis vs. Bacterial Rhinosinusitis 29.2 Acute Pharyngitis: Group A Streptococcus & Centor Criteria 29.3 Acute Otitis Media, Otitis Externa & Serous Effusion

30 Chapter 30: Acute Lower Respiratory Infections & Cough

30.1 Influenza, COVID-19 & Viral Respiratory Syndromes 30.2 Acute Bronchitis & Lower Respiratory Tract Infections 30.3 Ambulatory Community-Acquired Pneumonia

31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

31.1 Allergic Rhinitis & Acute Non-Anaphylactic Allergic Reactions 31.2 Acute Dyspnea in Ambulatory Care 31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

32.1 Palpitations Evaluation & Arrhythmia Triage in Primary Care 32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis 32.3 Ambulatory Hypotension & Orthostasis Evaluation

33 Chapter 33: Acute Upper Gastrointestinal Conditions

33.1 Peptic Ulcer Disease & Gastritis 33.2 Dysphagia, Esophagitis & Acute Esophageal Disorders 33.3 Acute Nausea, Vomiting & Foodborne Illness

34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

39.1 Atopic Dermatitis, Contact Dermatitis & Eczematous Flares 39.2 Non-Infectious Rashes: Urticaria, Drug Eruptions & Erythema Multiforme 39.3 Cutaneous Malignancies & Premalignant Lesions: AK, BCC, SCC & Melanoma

40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

40.1 Rotator Cuff Pathology, Tendinopathy & Shoulder Impingement 40.2 Lateral & Medial Epicondylitis, Olecranon Bursitis & Elbow Sprains 40.3 Wrist & Hand Soft-Tissue Injuries: De Quervain, TFCC & Finger Sprains

41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

41.1 Meniscal Tears, Ligamentous Knee Injuries & Patellofemoral Pain 41.2 Ankle Sprains, Ottawa Ankle Rules & Achilles Tendinopathy 41.3 Plantar Fasciitis, Shin Splints & Overuse Syndromes

42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

45.1 Uncomplicated UTI, Pyelonephritis & Acute Urethritis 45.2 Hematuria Workup & Glomerulonephritis 45.3 Nephrolithiasis & Acute Urinary Tract Obstruction

46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

54.1 Medical & Behavioral Management of Obesity & Incretin Mimetics 54.2 Osteoporosis & Metabolic Bone Disease: DEXA, FRAX & Antiresorptives 54.3 Nutritional Deficiencies: Vitamin D, B12, Iron & Malnutrition

55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

33.3 Acute Nausea, Vomiting & Foodborne Illness

Key Takeaways Explain This Topic AI

The etiologic differential diagnosis of acute nausea and vomiting spans gastrointestinal mechanical and inflammatory conditions, central neurologic pathologies (elevated intracranial pressure, vestibular labyrinthitis, migraine), metabolic crises (diabetic ketoacidosis, acute adrenal crisis, uremia), toxicologic exposures (digoxin toxicity, chemotherapy, cannabis hyperemesis), and pregnancy.

Foodborne illness toxidromes are classified by incubation periods: rapid onset within 1 to 6 hours indicates preformed enterotoxins with prominent emesis and minimal fever (Staphylococcus aureus from mayo/deli meats; Bacillus cereus emetic cerulide toxin from reheated fried rice); intermediate onset (8 to 16 hours) causes abdominal cramps and watery diarrhea (Clostridium perfringens in buffet meats; Bacillus cereus diarrheal toxin); and longer onset (>16 to 72 hours) signifies invasive bacterial enteritis (Salmonella, Campylobacter, STEC) or Norovirus (24-48 hours, cruise ships, alcohol-resistant).

In patients with acute bloody diarrhea and suspected Shiga toxin-producing E. coli (STEC / O157:H7), antimicrobial agents and antimotility drugs (loperamide) are ABSOLUTELY CONTRAINDICATED because bactericidal lysis induces massive Shiga toxin release, significantly precipitating Hemolytic Uremic Syndrome (HUS: microangiopathic hemolytic anemia, thrombocytopenia, and acute oliguric renal failure).

Oral rehydration therapy (ORT) utilizing standard reduced-osmolarity glucose-electrolyte solutions (WHO-ORS) exploits the intact sodium-glucose cotransporter-1 (SGLT-1) in the small intestinal brush border to drive fluid absorption, representing first-line treatment for mild-to-moderate dehydration; intravenous isotonic crystalloid resuscitation is reserved for severe dehydration, hemodynamic shock, altered mental status, or intractable emesis.

Antiemetic pharmacotherapy selection requires vigilance for major adverse profiles: ondansetron (5-HT3 antagonist) causes dose-dependent QTc prolongation; promethazine (phenothiazine) carries boxed warnings for severe tissue necrosis with intravenous extravasation and fatal respiratory depression in children <2 years; metoclopramide (D2 antagonist) carries a boxed warning for irreversible tardive dyskinesia with chronic use (>12 weeks) and can cause acute extrapyramidal dystonic reactions that must be treated immediately with intravenous diphenhydramine or benztropine.

Last updated: October 2026

Neurobiology of Nausea & the Emetic Reflex

Vomiting (emesis) is a complex, coordinated somatic reflex regulated by the central nervous system, involving retrograde peristalsis, contraction of abdominal wall musculature and the diaphragm, elevation of the soft palate, closure of the glottis, and relaxation of the lower esophageal sphincter and gastric cardia.

Central Integration & Receptor Populations

The central neural orchestration of vomiting involves two primary anatomic structures in the brainstem:

The Vomiting Center (Central Pattern Generator) :

Located in the lateral reticular formation of the medulla oblongata .

Integrates afferent neuronal signals from multiple peripheral and central pathways and coordinates the efferent somatic motor response via cranial nerves V, VII, IX, X, and XII, as well as spinal nerves supplying the diaphragm (phrenic nerve) and abdominal musculature.

The Chemoreceptor Trigger Zone (CTZ) :

Located in the area postrema in the caudal floor of the fourth ventricle.

Anatomical Pearl : The area postrema lies outside the blood-brain barrier , possessing fenestrated capillaries that allow direct exposure to circulating chemical toxins, emetogenic drugs (chemotherapy, opioids, digoxin), metabolic derangements (uremia, ketoacidosis), and hormones.

Receptor Profile : Richly concentrated with Dopamine D2 , Serotonin 5-HT3 , Neurokinin-1 (NK1 / Substance P) , and Opioid mu receptors.

Major Afferent Input Pathways

Vagal & Splanchnic Gastrointestinal Afferents : Enterochromaffin cells in the duodenal mucosa release massive amounts of serotonin (5-HT) in response to luminal toxins, mechanical distention, chemotherapy, or radiation, stimulating 5-HT3 receptors on primary vagal sensory afferents that project directly to the solitary tract nucleus (NTS) and CTZ.

Vestibular System : Motion, labyrinthine inflammation, or inner ear pathology transmits signals via cranial nerve VIII to the vestibular nuclei and cerebellum, signaling through Histamine H1 and Muscarinic M1 receptors.

Higher Cortical Centers : Limbic system, amygdala, and cerebral cortex transmit signals related to repulsive odors, anticipatory nausea, intense pain, extreme anxiety, and increased intracranial pressure (ICP) .

Differential Diagnosis of Acute Nausea & Vomiting

A disciplined organ-system approach is vital to prevent diagnostic anchoring on acute viral gastroenteritis:

Organ System Category Specific Etiologies Key Clinical Features & Discriminating Signs Decisive Diagnostic Workup

Gastrointestinal: Luminal Obstruction • Small Bowel Obstruction (SBO); • Gastric Outlet Obstruction (GOO); • Paralytic Ileus Crampy paroxysmal pain, early profuse bilious or feculent emesis, obstipation, high-pitched hyperactive bowel sounds (early) or absent (ileus), prior abdominal surgery Upright abdominal radiograph (air-fluid levels, dilated loops >3 cm); CT abdominopelvis with IV contrast (identifies transition point)

Gastrointestinal: Acute Inflammation • Acute Pancreatitis; • Acute Cholecystitis / Cholangitis; • Acute Appendicitis; • Acute Gastroenteritis Severe continuous epigastric pain radiating to back; RUQ pain with positive Murphy sign; periumbilical migrating to RLQ pain (McBurney point); fever, nausea Serum lipase (≥3x ULN); RUQ transabdominal ultrasound (gallstones, wall >3 mm, pericholecystic fluid); CT abdomen/pelvis

Central Nervous System • Elevated Intracranial Pressure (ICP) ; • Intracranial Hemorrhage / Mass; • Vestibular Neuritis / BPPV; • Migraine Headache Projectile vomiting WITHOUT preceding nausea ; early morning headache awakening patient from sleep; papilledema; Cushing triad (bradycardia, irregular respirations, hypertension); true room-spinning vertigo with nystagmus Urgent non-contrast Head CT or Brain MRI; fundoscopic exam; Dix-Hallpike maneuver (vestibular)

Endocrine & Metabolic • Diabetic Ketoacidosis (DKA) ; • Acute Adrenal Crisis (Addisonian) ; • Uremia / Acute Kidney Injury; • Hypercalcemia Polyuria, polydipsia, Kussmaul respirations (deep/rapid), fruity acetone breath, abdominal pain; profound refractory hypotension, skin hyperpigmentation; lethargy, pruritus, pericardial friction rub Blood glucose ≥200 mg/dL (or known diabetes), anion gap metabolic acidosis, serum/urine ketones; hyponatremia, hyperkalemia, hypoglycemia, random cortisol / cosyntropin stimulation test; BUN/Cr, serum calcium

Toxicologic & Pharmacologic • Medications (NSAIDs, antibiotics, opioids); • Digoxin Toxicity ; • Chemotherapy; • Cannabis Hyperemesis Syndrome (CHS) Anorexia, nausea, yellow-green visual halos (xanthopsia), bidirectional VT; chronic daily cannabis use, cyclical severe morning nausea/vomiting alleviated compulsively by scalding hot showers Serum digoxin level, serum potassium, ECG; clinical history of cannabis cessation resulting in permanent symptom resolution

Pregnancy-Related • Hyperemesis Gravidarum; • Pre-eclampsia / HELLP syndrome Intractable vomiting, >5% pre-pregnancy weight loss, ketonuria, volume depletion; third trimester RUQ pain, hypertension, proteinuria, elevated transaminases Urine pregnancy test (beta-hCG), electrolytes (hypokalemic hypochloremic metabolic alkalosis), AST/ALT, platelets, LDH

Foodborne Illness Toxidromes: Classification by Incubation Period

The incubation period—the precise elapsed time between food ingestion and the onset of initial symptoms—is the most decisive clinical differentiator in foodborne illness outbreaks: FOODBORNE ILLNESS INCUBATION SPECTRUM

• 0 Hours 1 to 6 Hours 8 to 16 Hours >16 to 72 Hours
• ───┼──────────────┼────────────────────────┼──────────────────────┼──────────>
• Ingestion PREFORMED TOXINS INTERMEDIATE TOXINS INVASIVE / VIRAL
• S. aureus • C. perfringens • Salmonella (12-72h)
• B. cereus (emetic) • B. cereus (diarrheal)• Campylobacter (2-5d)
• (Violent emesis, (Severe cramps, watery • STEC / O157:H7 (3-8d)
• minimal/no fever) diarrhea, NO emesis) • Norovirus (24-48h)
• (Inflammatory / bloody)
• 1. Rapid-Onset Preformed Enterotoxins (Incubation: 1 to 6 Hours)

Characterized by direct ingestion of preformed, heat-stable exotoxins present in contaminated food prior to consumption. Because the toxin is already synthesized, symptom onset is abrupt and explosive, dominated by violent, repetitive vomiting and nausea , while fever is typically absent and diarrhea is mild:

Staphylococcus aureus :

Pathophysiology : Enterotoxins A through E are heat-stable proteins that resist boiling for 30 minutes and withstand gastric acid and peptic enzymatic breakdown. Toxins stimulate local neural vagal receptors in the gut wall, triggering the central vomiting reflex.

Classic Food Reservoirs : Foods prepared by human food handlers and subsequently kept unrefrigerated at room temperature: mayonnaise-based salads (potato salad, egg salad, macaroni salad, tuna salad) , cream-filled pastries, custards, sliced processed deli meats, and unpasteurized dairy.

Course : Abrupt onset 1 to 6 hours (peak 2 to 4 hours) post-ingestion; violent projectile emesis, abdominal cramping, and prostration. Resolves spontaneously within 12 to 24 hours.

Bacillus cereus (Emetic Syndrome) :

Pathophysiology : Produces cerulide , a small, ring-shaped, heat-stable, acid-resistant dodecadepsipeptide enterotoxin that binds 5-HT3 receptors and activates vagal afferents.

Classic Food Reservoir : Reheated fried rice ("fried rice syndrome") or pasta dishes. Spores survive boiling of rice; if cooked rice is left cooling at room temperature, spores germinate into vegetative forms that synthesize cerulide. Flash-frying or rapid reheating kills the vegetative bacteria but fails to inactivate the heat-stable cerulide toxin.

Course : Explosive vomiting and nausea within 1 to 5 hours of eating; afebrile; resolves within 24 hours.

2. Intermediate Incubation: Toxin Produced In Vivo (Incubation: 8 to 16 Hours)

Characterized by ingestion of bacterial vegetative cells or spores that survive gastric passage, colonize the small intestine, and synthesize enterotoxins in vivo . Manifests primarily with intense, crampy abdominal pain and profuse watery diarrhea , while vomiting is rare or absent :

Clostridium perfringens (Type A) :

Pathophysiology : Anaerobic, spore-forming Gram-positive rod. Spores survive cooking; when large quantities of cooked food are allowed to cool slowly or held at warm temperatures (40°C to 50°C), spores germinate into vegetative cells. Ingestion of >10^8 vegetative cells leads to sporulation in the alkaline small intestine, releasing Clostridium perfringens enterotoxin (CPE) , which disrupts enterocyte tight junctions and causes large-volume secretory fluid loss.

Classic Food Reservoirs : Catered buffet meats, institutional gravies, stews, poultry, and steam-table casseroles served at banquets, school cafeterias, or nursing homes.

Course : Severe lower abdominal cramps and profuse watery diarrhea starting 8 to 16 hours after ingestion; afebrile; emesis is absent in >80%; resolves in 24 to 48 hours.

Bacillus cereus (Diarrheal Syndrome) :

Pathophysiology : Ingestion of bacterial cells that produce a heat-labile enterotoxin (HBL/Nhe) in the small intestine, stimulating the adenylate cyclase-cyclic AMP system.

Classic Food Reservoirs : Contaminated meats, vegetables, puddings, and vanilla sauces held at lukewarm temperatures.

Course : Watery diarrhea and abdominal cramps starting 8 to 16 hours post-consumption; emesis is distinctly uncommon.

3. Longer Incubation: Invasive Bacterial & Viral Enteritis (Incubation: >16 to 72 Hours)

Characterized by bacterial invasion of intestinal enterocytes or viral mucosal destruction, producing inflammatory diarrhea, systemic fevers, and high morbidity:

Salmonella enterica (Non-Typhoidal) :

Incubation : 12 to 72 hours.

Sources : Undercooked poultry, raw eggs, unpasteurized milk, handling of reptiles (turtles, lizards, snakes) , amphibians, and backyard poultry.

Clinical Manifestations : Inflammatory enteritis with nausea, vomiting, fever, abdominal cramping, and loose watery to bloody stools.

Antimicrobial Rule : In healthy, immunocompetent hosts, antibiotics are strictly withheld because they do not shorten symptom duration and prolong fecal bacterial shedding (asymptomatic carrier state). Antibiotic therapy (oral ciprofloxacin or azithromycin) is indicated only for high-risk patients : infants aged <3 months, adults aged >50 years with suspected atherosclerosis (risk of endovascular aortic graft seeding), patients with sickle cell disease (risk of Salmonella osteomyelitis), prosthetic joints, or severe immunosuppression.

Campylobacter jejuni :

Incubation : 2 to 5 days.

Sources : The leading bacterial cause of diarrheal illness in the US. Undercooked poultry, unpasteurized milk, contaminated municipal water.

Clinical Manifestations : Prodrome of high fever and myalgias, followed by severe periumbilical or RLQ abdominal cramping that frequently mimics acute appendicitis ( pseudoappendicitis ), and profuse watery to grossly bloody diarrhea.

Post-Infectious Sequelae : Guillain-Barré Syndrome (GBS) via molecular mimicry between C. jejuni lipooligosaccharides and human peripheral nerve GM1 gangliosides (ascending symmetric paralysis; ~1 in 1,000 cases); Reactive arthritis (HLA-B27).

Treatment : Oral azithromycin (500 mg daily for 3 days) for severe, persistent, or immunocompromised patients (fluoroquinolones avoided due to >30% resistance).

Shiga Toxin-Producing Escherichia coli (STEC / EHEC O157:H7) :

Incubation : 3 to 8 days.

Sources : Undercooked ground beef, unpasteurized apple cider, contaminated leafy greens (spinach, romaine lettuce), and petting zoos.

Clinical Manifestations : Severe, crampy abdominal pain and watery diarrhea that rapidly becomes profusely bloody within 24 to 48 hours, characteristically occurring with little or no fever .

CRITICAL CONTRAINDICATION : Antimicrobial therapy and antimotility drugs (loperamide) are ABSOLUTELY CONTRAINDICATED ! Antibiotics trigger bacterial SOS stress responses and cellular lysis, causing massive release of preformed Shiga toxins (Stx1 and Stx2) into the intestinal lumen. Subsequent systemic absorption binds endothelial Gb3 receptors in the renal microvasculature, precipitating Hemolytic Uremic Syndrome (HUS) —the lethal triad of microangiopathic hemolytic anemia (schistocytes), thrombocytopenia, and acute oliguric renal failure. Treatment is strictly supportive with aggressive intravenous isotonic crystalloid hydration.

Norovirus (Caliciviridae) :

Incubation : 24 to 48 hours.

Epidemiology : The leading cause of non-bacterial gastroenteritis and foodborne disease outbreaks across all age groups. Hallmark outbreaks in closed, crowded settings: cruise ships, nursing homes, hospitals, schools, and military barracks .

Transmission & Resistance : Extremely low infectious dose (<20 viral particles); aerosolized vomitus droplets and fomite transmission. Norovirus is non-enveloped and highly resistant to alcohol-based hand sanitizers ; hand hygiene must be performed with soap and warm running water, and environmental surfaces disinfected with sodium hypochlorite (bleach).

Course : Sudden onset of projectile vomiting, watery non-bloody diarrhea, and low-grade fever lasting 24 to 48 hours.

Clinical Dehydration Assessment & Oral Rehydration Therapy (ORT)

Accurate clinical assessment of intravascular volume status dictates whether a patient can be managed with oral rehydration or requires emergent intravenous resuscitation.

Clinical Dehydration Classification

Assessment Parameter Mild Dehydration (<5% Weight Loss) Moderate Dehydration (5% to 10% Weight Loss) Severe Dehydration (>10% Weight Loss)

Mental Status Alert, active, thirsty Restless, irritable, fatigued, thirsty Lethargic, stuporous, somnolent, or comatose

Heart Rate & Pulse Normal heart rate and pulse volume Tachycardia; normal to slightly decreased pulse volume Marked tachycardia; weak, thready, or impalpable pulses

Blood Pressure Normal systolic and diastolic BP Normal BP; orthostatic drop (>20 mmHg drop in SBP or >10 mmHg in DBP) Hypotension (SBP <90 mmHg); unrecordable in shock

Mucous Membranes Moist lips and tongue Dry lips, tacky buccal mucosa Parched, cracked lips and oral mucosa

Tears & Eyes Normal tearing; normal eye contour Decreased tearing; slightly sunken orbits Absent tears; deeply sunken eyes and sunken fontanelle

Skin Turgor Instantaneous skin recoil (<1 second) Slow skin recoil (1 to 2 seconds) Very slow skin recoil (>2 seconds / 'tenting')

Capillary Refill Normal (<2 seconds) Prolonged (2 to 3 seconds) Markedly prolonged (>3 to 4 seconds), cool mottled extremities

Urine Output Normal or slightly decreased Oliguria; concentrated dark amber urine Oliguria (<0.5 mL/kg/hr) to complete anuria

Oral Rehydration Therapy (ORT): Physiological Foundation

The SGLT-1 Cotransporter : The sodium-glucose cotransporter-1 (SGLT-1) on the apical brush border of enterocytes couples the transport of one sodium ion with one glucose molecule from the intestinal lumen into the cell cytoplasm. This creates an osmotic gradient that drives passive transcellular and paracellular water absorption.

Physiological Resilience : Crucially, the SGLT-1 cotransporter remains intact and fully operational even during cholera, enterotoxigenic bacterial infections, and rotavirus/norovirus gastroenteritis when passive mucosal pathways are overwhelmed by secretory fluxes.

WHO Reduced-Osmolarity ORS Formulation :

Osmolarity: 245 mOsm/L (prevents osmotic diarrhea caused by hyperosmolar formulations like apple juice or commercial sports drinks);

• Sodium: 75 mEq/L (or mmol/L);
• Glucose: 75 mmol/L (13.5 g/L);

Potassium: 20 mEq/L ; Chloride: 65 mEq/L ; Citrate: 10 mmol/L (corrects metabolic acidosis).

Administration Protocol :

Mild-to-moderate dehydration: Administer 50 to 100 mL/kg of ORS over 3 to 4 hours , supplemented with 10 mL/kg for each diarrheal stool and 2 mL/kg for each episode of emesis.

In vomiting patients, give ORS in small, frequent aliquots (5 to 10 mL via spoon or oral syringe every 2 to 5 minutes), gradually increasing the volume as vomiting subsides.

Indications for Intravenous Hydration :

• Severe dehydration (>10% volume loss) or hemodynamic shock (hypotension, thready pulse);
• Altered mental status, stupor, or coma (high aspiration risk with ORT);
• Intractable, repetitive vomiting despite antiemetic administration;

Paralytic ileus or suspected mechanical bowel obstruction.

IV Regimen : 20 mL/kg bolus of isotonic crystalloid (Lactated Ringer's or normal saline) administered rapidly over 15 to 30 minutes, repeated until vital signs, pulse volume, and mental status normalize.

Antiemetic Pharmacotherapy: Mechanisms, Dosages & Critical Toxicities

Antiemetic medications provide targeted symptom relief, facilitating oral rehydration and preventing hospitalization, but each class carries distinct neurochemical adverse profiles:

Comparison of Antiemetic Drug Classes

Drug Class & Agent Dosing & Route Mechanism of Action Clinical Indications Major Toxicities & Black Box Warnings

Serotonin 5-HT3 Antagonist :; Ondansetron (Zofran) 4 to 8 mg PO (or ODT) or IV every 8 hours prn Selective competitive antagonism of 5-HT3 receptors on vagal afferents and in the area postrema (CTZ) Acute gastroenteritis, post-operative emesis, chemotherapy-induced nausea • Dose-dependent QTc prolongation (risk of Torsades de Pointes; avoid single IV doses >16 mg; caution in congenital long QT, hypokalemia, hypomagnesemia); • Headache (15-20%), constipation; • Serotonin syndrome when combined with SSRIs/SNRIs

Phenothiazine :; Promethazine (Phenergan) 12.5 to 25 mg PO, PR, or deep IM every 4 to 6 hours prn Antagonism of dopamine D2 receptors in CTZ; potent central H1-histamine and M1-muscarinic blockade Motion sickness, labyrinthitis, severe nausea and vomiting • BLACK BOX WARNING: Severe tissue injury, chemical gangrene, and limb amputation with IV extravasation (deep IM is preferred; IV requires severe dilution, slow piggyback into large-bore vein); • BLACK BOX WARNING: Fatal respiratory depression in children aged <2 years (strictly contraindicated); • Sedation, anticholinergic toxidrome, lowered seizure threshold

Dopamine D2 Antagonist / Prokinetic :; Metoclopramide (Reglan) 10 mg PO or IV TID-QID (30 min before meals & bedtime) Central D2 receptor blockade in CTZ PLUS peripheral prokinetic upper GI effect (sensitizes gastric smooth muscle to acetylcholine, accelerating gastric emptying) Diabetic gastroparesis, GERD, acute nausea, migraine-associated nausea • BLACK BOX WARNING: Tardive Dyskinesia (potentially irreversible choreoathetoid movements of face/tongue; risk increases with treatment duration >12 weeks ); • Acute Extrapyramidal Symptoms (EPS) : Acute dystonic reactions (torticollis, oculogyric crisis, trismus); • Hyperprolactinemia (galactorrhea, amenorrhea, gynecomastia)

First-Generation Antihistamines :; • Meclizine ; • Dimenhydrinate • Meclizine 25 to 50 mg PO daily to BID; • Dimenhydrinate 50 to 100 mg PO q4-6h Blocks H1 receptors in vestibular nuclei and solitary tract; significant central anticholinergic activity Motion sickness, vestibular neuritis, labyrinthitis , benign paroxysmal positional vertigo (BPPV) • Marked drowsiness, sedation, impaired driving ability; • Anticholinergic toxicity: dry mouth, blurred vision, acute urinary retention (caution in elderly males with BPH), closed-angle glaucoma exacerbation

Anticholinergic :; Scopolamine (Transderm Scop) 1.5 mg transdermal patch applied post-auricular every 72 hours (apply ≥4 hours prior to travel) Competitive antagonist of central and peripheral muscarinic acetylcholine (M1) receptors in vestibular pathway Prevention of motion sickness and post-operative nausea/vomiting • Anticholinergic side effects: dry mouth, drowsiness, cycloplegia (blurred near vision); • Anisocoria / unilateral dilated pupil if patch residue is transferred by fingers into the eye; • Acute confusion / delirium in elderly patients

Caution

Emergency Management of Metoclopramide-Induced Acute Dystonia :

If a patient develops an acute extrapyramidal dystonic reaction (such as spasmodic torticollis, facial grimacing, or oculogyric crisis) following metoclopramide administration, immediately administer Intravenous Diphenhydramine (25 to 50 mg IV) or Intravenous Benztropine (1 to 2 mg IV) . These anticholinergic agents restore the striatal dopaminergic-cholinergic balance, terminating muscle spasms within 5 to 10 minutes.

Loading diagram... Clinical Decision Algorithm for Foodborne Illness & Acute Emesis