Gastroenteritis (viral and bacterial)MANAGEMENT

GASTROINTESTINAL PRESENTATIONS · 12 SECTIONS

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529 items

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01Approach to the Critical Patient/attcp54

Immediate priorities

›Initial stabilization and triage

›Airway patency and aspiration risk

›Active vomiting with altered mental status

›Ongoing hematemesis

›Breathing and oxygenation

›SpO2 target 92% or higher

›Respiratory fatigue from severe metabolic acidosis

›Circulation and perfusion

›Shock index concern

›Capillary refill delay

›Point-of-care glucose

›Hypoglycemia risk with poor intake

›Hyperglycemia as alternative diagnosis

Risk stratification

›High-risk features

›Hemodynamic instability

›SBP under 90 mmHg adult

›Age-adjusted hypotension pediatric

›Severe dehydration

›Lethargy or altered mental status

›Anuria or minimal urine output

›Invasive bacterial diarrhea concern

›Bloody diarrhea

›Severe abdominal pain

›Severe systemic illness

›Sepsis criteria

›Immunocompromised state

Infection control

›Isolation and precautions

›Contact precautions for suspected infectious diarrhea

›Norovirus outbreak setting

›Diapered or incontinent patients

›Soap-and-water hand hygiene triggers

›Suspected norovirus

›Suspected Clostridioides difficile

Initial resuscitation

›Fluid and symptom control pathway

›Oral rehydration trial if stable

›Small frequent sips

›Early antiemetic to enable ORS

›IV fluids if unable to tolerate PO or shock

›Isotonic crystalloid bolus strategy

›Reassessment after each bolus

Early diagnostic decision points

›Testing thresholds

›No routine labs for mild self-limited illness

›Short duration

›No red flags

›Escalate testing for severe or high-risk illness

›Significant dehydration

›Blood in stool

Consultation triggers

›Escalation and specialty involvement

›Surgery trigger

›Peritoneal signs

›Concern for appendicitis or obstruction

›ICU trigger

›Persistent shock after fluids

›Severe acidosis with end-organ dysfunction

02History/hx46

Core symptom pattern

›Symptom characterization

›Diarrhea profile

›Watery volume and frequency

›Blood or mucus

›Vomiting profile

›Frequency and bilious content

›Inability to keep fluids down

›Timeline

›Onset time and peak severity

›Duration over 7 days

Exposure and epidemiology

›Exposure risks

›Sick contacts

›Household cluster

›Daycare or school exposure

›Food exposures

›Undercooked poultry or eggs

›Unpasteurized dairy or juice

›Water exposures

›Untreated well or stream water

›Recent swimming in lakes or pools

›Travel exposures

›Recent international travel

›Cruise ship exposure

High-risk history

›Complicating factors

›Dehydration indicators

›Dizziness or syncope

›Oliguria

›Medication and healthcare exposures

›Recent antibiotics within 8 weeks

›Recent hospitalization or long-term care exposure

›Comorbidities

›Chronic kidney disease

›Inflammatory bowel disease

›Immunocompromise

›Transplant

›Chemotherapy

Focused differentials in history

›Alternative diagnosis clues

›Predominant localized abdominal pain

›RLQ pain

›Severe constant pain out of proportion

›Genitourinary symptoms

›Dysuria

›Flank pain

›Neurologic or toxin concern

›Neurologic symptoms after fish ingestion

›Severe symptoms within 6 hours of meal

03Physical Exam/exam33

Vital signs and perfusion

›Severity assessment

›Vital signs trend

›Fever pattern

›Tachycardia

›Perfusion markers

›Capillary refill time

›Peripheral temperature

›Orthostasis when safe

›Postural tachycardia

›Postural hypotension

Hydration assessment

›Dehydration findings

›General appearance

›Lethargy or irritability

›Weak cry or poor interaction pediatric

›Mucous membranes and tears

›Dry mucosa

›Reduced tears pediatric

›Skin and eyes

›Decreased skin turgor

›Sunken eyes pediatric

›Urine output surrogate

›Dry diaper over 6 to 8 hours infant

›Minimal urine adult

Abdominal and systemic exam

›Abdomen and complications

›Abdominal tenderness pattern

›Diffuse mild tenderness

›Localized guarding

›Peritoneal signs

›Rebound

›Rigidity

›Extraintestinal findings

›Rash suggesting viral syndrome

›Arthritis suggesting reactive process

04Differential Diagnosis/ddx40

Primary gastroenteritis categories

›Infectious gastroenteritis

›Viral gastroenteritis

›Norovirus infection

›Rotavirus infection pediatric

›Bacterial gastroenteritis

›Campylobacter enteritis

›Salmonella gastroenteritis

›Protozoal gastroenteritis

›Giardia infection

›Cryptosporidiosis

Life-threatening mimics

›High-risk alternate diagnoses

›Surgical abdomen

›Appendicitis ICD-10 K35

›Bowel obstruction ICD-10 K56

›Severe systemic infection

›Sepsis ICD-10 A41.9

›Meningitis ICD-10 G03.9 in infants with vomiting

›Vascular and ischemic

›Mesenteric ischemia ICD-10 K55.9

›Aortic catastrophe with abdominal pain

Important specific entities

›Targeted infectious considerations

›Inflammatory dysentery

›Shigellosis ICD-10 A03

›Entamoeba histolytica colitis ICD-10 A06.0

›Shiga toxin producing E. coli

›STEC enteritis ICD-10 A04.3

›Hemolytic uremic syndrome ICD-10 D59.3 risk

›Clostridioides difficile infection

›CDI ICD-10 A04.7

›Fulminant colitis risk

Noninfectious diarrhea

›Noninfectious causes

›Inflammatory bowel disease flare

›Ulcerative colitis ICD-10 K51

›Crohn disease ICD-10 K50

›Medication-related diarrhea

›Metformin effect

›Magnesium-containing laxatives

›Endocrine and metabolic

›Thyrotoxicosis ICD-10 E05.90

›Adrenal crisis ICD-10 E27.2

05Laboratory Tests/lt45

Core labs for severity and complications

›Baseline assessment for moderate to severe illness

›Basic metabolic panel

›Sodium and potassium derangements

›Hypokalemia with vomiting and diarrhea

›Hypernatremia pediatric dehydration

›Creatinine for AKI

›Prerenal azotemia pattern

›CKD baseline comparison

›Serum glucose

›Hypoglycemia pediatric risk

›Hyperglycemia alternative diagnosis

›Venous blood gas if severe

›Metabolic acidosis assessment

›Bicarbonate level estimate

›Lactate if shock

Infection and inflammatory evaluation

›Labs when systemic illness or invasive diarrhea concern

›Complete blood count

›Leukocytosis support for bacterial or stress response

›Hemoglobin and platelets baseline for HUS risk

›Blood cultures triggers

›High fever and toxicity

›Immunocompromised or suspected enteric fever

Stool studies

›Stool testing indications

›Multiplex stool PCR panel

›Severe illness

›Public health or outbreak setting

›Stool culture with susceptibilities

›Dysentery

›Immunocompromised host

›Shiga toxin assay

›Bloody diarrhea

›HUS concern

›Clostridioides difficile testing

›3 or more unformed stools in 24 hours with risk factors

›Recent antibiotics or healthcare exposure

›Ova and parasites

›Diarrhea over 14 days

›Travel or daycare exposure

Pitfalls and interpretation

›Common limitations

›Mild viral gastroenteritis

›Normal labs do not exclude dehydration

›Fever absence does not exclude bacterial disease

›Stool PCR overdiagnosis

›Detection without causation

›Clinical correlation requirement

06Diagnostic Tests/dt39

Scoring Systems

›Severity scoring and bedside tools

›Clinical Dehydration Scale pediatric

›General appearance component

›Eyes and mucous membranes component

›Tears component

›Association with dehydration severity and ORS failure risk

›Gorelick dehydration scale pediatric

›Physical signs count approach

›Application in ED triage

›Sepsis screening framework

›qSOFA adult limitations in ED

›Pediatric sepsis recognition based on age-adjusted vitals

MRI

›MRI role in vomiting and diarrhea presentations

›Alternative diagnosis evaluation

›Inflammatory bowel disease complications

›Pregnancy appendicitis pathway

›Limited role in uncomplicated gastroenteritis

›Time and availability constraints

›Motion artifact with active vomiting

›CT abdomen pelvis indications

›Surgical abdomen concern

›Localized peritonitis

›Obstruction symptoms

›Severe abdominal pain disproportionate

›Mesenteric ischemia concern

›Toxic megacolon concern

›Complicated colitis concern

›Severe CDI

›IBD flare with systemic toxicity

Ultrasound (or US)

›Ultrasound applications

›Appendicitis assessment

›RLQ pain with vomiting

›Pediatric first-line imaging

›Biliary pathology assessment

›RUQ pain with vomiting

›Gallbladder wall and stones

›POCUS volume status adjunct

›IVC assessment limitations

›Lung ultrasound for alternative diagnosis in dyspnea

07Disposition/dispo33

Discharge criteria

›Safe discharge features

›Stable vital signs

›No persistent tachycardia after rehydration

›Afebrile or improving fever pattern

›Oral intake adequacy

›Tolerating ORS or fluids after antiemetic

›No intractable vomiting

›No high-risk features

›No bloody diarrhea with systemic toxicity

›No severe abdominal tenderness

›Reliable follow-up and return ability

›Caregiver understanding pediatric

›Access to re-evaluation

Admission criteria

›Inpatient indications

›Severe dehydration

›Ongoing large volume losses

›AKI or significant electrolyte abnormality

›Persistent inability to tolerate oral fluids

›Failed ORS despite antiemetic

›Recurrent ED visits

›Invasive infection concern

›Bacteremia risk group

›Severe dysentery

›Social and safety concerns

›Frailty or poor supports

›Unsafe home situation

ICU criteria

›Critical care indications

›Shock requiring vasoactive support

›Persistent hypotension after adequate fluids

›Rising lactate with organ dysfunction

›Fulminant colitis concern

›Toxic megacolon features

›Severe CDI with ileus

08Treatment/t139

Rehydration strategy

›Fluid replacement and targets

›Oral rehydration solution

›Early initiation for mild to moderate dehydration

›Frequent small volumes

›Continued feeding pediatric

›ORS composition principle

›Glucose-sodium cotransport mechanism

›Avoid high-sugar drinks worsening diarrhea

›IV isotonic crystalloids

›Adult bolus approach

›0.9% sodium chloride 1 L IV

›Repeat 500 mL to 1 L based on response

›Reassessment after each bolus

›Ringer lactate 1 L IV

›Repeat 500 mL to 1 L based on response

›Preference in significant acidosis consideration

›Pediatric bolus approach

›0.9% sodium chloride 20 mL/kg IV

›Repeat up to 60 mL/kg with reassessment

›Escalate for shock physiology

›Ringer lactate 20 mL/kg IV

›Repeat up to 60 mL/kg with reassessment

›Monitor for ongoing losses

Antiemetics

›Vomiting control to enable hydration

›Ondansetron oral

›Adult 4 mg PO

›Repeat 4 mg PO once after 8 hours if needed

›QT prolongation risk in susceptible patients

›Pediatric 0.15 mg/kg PO

›Maximum 8 mg PO

›Single-dose strategy for ORS success

›Ondansetron IV

›Adult 4 mg IV

›Repeat 4 mg IV once after 8 hours if needed

›ECG consideration with risk factors

›Pediatric 0.15 mg/kg IV

›Maximum 8 mg IV

›Prefer oral when possible

Antidiarrheals and adjuncts

›Symptom control and safety

›Loperamide

›Adult 4 mg PO once

›2 mg PO after each loose stool

›Maximum 16 mg per day

›Avoid loperamide triggers

›Bloody diarrhea

›Suspected inflammatory colitis or CDI

›Bismuth subsalicylate adult

›524 mg PO every 30 to 60 minutes as needed

›Maximum 8 doses per day

›Salicylate contraindications

›Avoid in pediatrics

›Reye syndrome risk

›Viral illness in children

›Probiotics

›Limited benefit in acute infectious diarrhea

›Modest duration reduction in some studies

›Avoid in severe immunocompromise

Empiric antibiotics

›When antibiotics help

›Indications for empiric therapy

›Moderate to severe travelers diarrhea

›Frequent stools with functional impairment

›Fever or blood in stool

›Dysentery with systemic symptoms

›High fever

›Severe tenesmus

›Suspected cholera with severe dehydration

›Profuse rice-water diarrhea

›Outbreak or endemic exposure

›Avoid antibiotics triggers

›Suspected STEC infection

›Bloody diarrhea with minimal fever

›HUS risk

›Mild noninvasive watery diarrhea

›Self-limited course

›Supportive care preferred

›Adult empiric regimens

›Azithromycin

›1 g PO single dose

›Preferred for dysentery and South Asia travel

›Macrolide resistance local variation

›500 mg PO daily for 3 days

›Alternative to single dose

›Nausea risk with 1 g dose

›Ciprofloxacin

›750 mg PO single dose

›Avoid with high fluoroquinolone resistance regions

›Tendinopathy and QT risk

›500 mg PO twice daily for 3 days

›Alternative regimen

›Avoid in pregnancy when possible

›Rifaximin

›200 mg PO three times daily for 3 days

›Noninvasive travelers diarrhea only

›Avoid with fever or blood in stool

›Pediatric empiric regimens

›Azithromycin

›10 mg/kg PO daily for 3 days

›Maximum 500 mg per day

›Preferred for travelers diarrhea dysentery concern

›20 mg/kg PO single dose

›Maximum 1 g

›Consider in selected settings

Targeted antimicrobial therapy

›Common pathogen-directed therapy

›Shigella suspected or confirmed

›Azithromycin adult 500 mg PO daily for 3 days

›Local resistance patterns consideration

›Public health notification in outbreaks

›Ceftriaxone adult 2 g IV daily

›Severe illness or unable to take PO

›Typical duration 3 to 5 days

›Campylobacter severe disease

›Azithromycin adult 500 mg PO daily for 3 days

›Greatest benefit early in disease course

›Fluoroquinolone resistance common in some regions

›Azithromycin pediatric 10 mg/kg PO daily for 3 days

›Maximum 500 mg per day

›Consider with dysentery or high fever

›Nontyphoidal Salmonella high-risk host

›Ciprofloxacin adult 500 mg PO twice daily

›Typical duration 3 to 7 days

›Bacteremia risk groups only

›Ceftriaxone adult 2 g IV daily

›Severe infection or bacteremia

›Typical duration 7 to 14 days for bacteremia

Clostridioides difficile management

›CDI treatment pathway

›Nonsevere initial episode

›Fidaxomicin 200 mg PO twice daily for 10 days

›Preferred when available per major guidelines

›Lower recurrence compared with vancomycin in trials

›Vancomycin 125 mg PO four times daily for 10 days

›Alternative first-line

›Avoid antimotility agents

›Severe or fulminant CDI concern

›Vancomycin 500 mg PO or NG four times daily

›Add rectal vancomycin if ileus

›Early surgical consultation for toxic megacolon concern

›Metronidazole 500 mg IV every 8 hours

›Adjunct in fulminant disease

›Not preferred as monotherapy for initial nonsevere disease

09Special Populations/sp30

Pregnancy

›Pregnancy-specific considerations

›Maternal and fetal risks

›Lower threshold for IV fluids with persistent vomiting

›Fetal monitoring consideration in viable gestation with severe illness

›Medication safety

›Ondansetron risk-benefit individualized

›Avoid tetracyclines when possible

›Antibiotic selection

›Azithromycin preferred for travelers diarrhea when needed

›Avoid fluoroquinolones when alternatives exist

Geriatric

›Older adult considerations

›Higher complication risk

›AKI with modest volume loss

›Delirium with dehydration

›Medication risks

›QT prolongation interactions

›Diuretic and ACE inhibitor effect on volume status

›Disposition threshold

›Lower threshold for observation

›Home support assessment

Pediatrics

›Pediatric considerations

›Dehydration recognition

›Weight change when available

›Capillary refill and mental status emphasis

›Feeding guidance

›Continue breastfeeding

›Early return to age-appropriate diet after rehydration

›Red flags

›Bilious vomiting

›Bloody stool in young infant

10Background/b30

Epidemiology

›Burden and common etiologies

›Viral predominance in community gastroenteritis

›Norovirus as common cause of outbreaks

›Rotavirus reduced in vaccinated populations

›Bacterial patterns

›Campylobacter common in poultry exposure

›Salmonella associated with eggs poultry reptiles

›Seasonality and settings

›Winter vomiting illness pattern for norovirus

›Daycare and long-term care outbreaks

Pathophysiology

›Mechanisms of diarrhea and vomiting

›Secretory diarrhea physiology

›Increased chloride secretion and water loss

›Minimal fecal leukocytes

›Inflammatory diarrhea physiology

›Mucosal invasion and cytokine response

›Blood and fecal leukocytes

›Dehydration and electrolyte loss

›Hypokalemia from stool losses

›Metabolic acidosis from bicarbonate loss

Therapeutic Considerations

›Rationale for key therapies

›Oral rehydration effectiveness

›Glucose-sodium cotransport intact in most diarrheas

›Reduced need for IV fluids in mild to moderate dehydration

›Antibiotic stewardship

›Limited benefit in most noninvasive gastroenteritis

›Harm potential with STEC and HUS risk

›Antiemetic use

›Improved ORS success with single-dose ondansetron pediatric

›QT risk management in susceptible patients

11Patient Discharge Instructions/pdi20

Copy discharge instructions

›Home care and return precautions

›Hydration plan

›Oral rehydration solution preferred

›Small frequent sips after vomiting

›Diet guidance

›Resume regular diet as tolerated

›Avoid high-sugar drinks and alcohol

›Contagion reduction

›Hand hygiene with soap and water if vomiting illness

›Avoid food preparation for others while symptomatic

›Return to ED immediately

›Blood in stool

›Severe or worsening abdominal pain

›Signs of dehydration

›Confusion or fainting

›Persistent vomiting with inability to keep fluids down

›Fever with worsening condition

›Follow-up timing

›Primary care follow-up if symptoms over 3 days without improvement

›Earlier follow-up for infants older adults pregnancy immunocompromise

12References/r20

Clinical guidelines and evidence sources

›Major guideline sources

›IDSA Clinical Practice Guidelines for Infectious Diarrhea

›Stool testing indications and pathogen-specific management framework

›High-risk host considerations

›ACG Clinical Guideline for Acute Infectious Diarrhea in Adults

›Empiric antibiotic criteria and travelers diarrhea approach

›Supportive care and antimotility cautions

›CDC guidance for norovirus and foodborne illness

›Outbreak control and isolation considerations

›Hand hygiene recommendations

›SHEA IDSA Clostridioides difficile guidelines

›Fidaxomicin and vancomycin first-line recommendations

›Fulminant CDI management pathway

Evidence levels and recommendation framing

›Recommendation grading conventions

›IDSA strong versus conditional recommendations based on evidence certainty

›Stewardship emphasis for empiric antibiotics

›Testing escalation for severe or high-risk illness

›Class I IIa IIb convention for supportive care in critical illness contexts

›Class I isotonic crystalloid for hypovolemic shock

›Class IIa antiemetic to enable oral rehydration in selected patients

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed June 16, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.