Gastroenteritis, Bacterial and Viral
Kathy R. Reese and Cheryl A. Glass
Definition
A.Bacterial and viral gastroenteritis is an acute inflammation of the gastrointestinal (GI) mucosa of the middle or lower intestine. It is primarily an acute, self-limited illness that resolves in a week or less. The illness is usually accompanied by nausea, vomiting, diarrhea, fever, and generalized abdominal pain but can occur with diarrhea alone. Immunocompromised patients can develop unremitting or fatal symptoms from gastroenteritis.
Incidence
A.Gastroenteritis is very common, occurring in all age groups. Epidemic outbreaks of bacterial gastroenteritis occur in groups who have ingested contaminated food. Viral excretion can begin before symptoms. Gastroenteritis is responsible for an estimated eight million healthcare visits and 250,000 hospitalization a year.
TABLE 14.11 Infectious Agents Causing Gastroenteritis
Pathogenesis
A.Gastroenteritis is commonly due to infectious agents—viruses, bacteria, and parasites (see Table 14.11). There are four viral agents: rotavirus, norovirus, enteric adenovirus, and astrovirus. Exotoxins produced by some organisms induce hypersecretion or increased peristalsis, resulting in diarrhea or vomiting. Bacteria such as Escherichia coli and Salmonella penetrate and invade the gastric mucosa and lead to diarrhea accompanied by fever and fecal leukocytes. Viruses destroy enterocytes of the upper jejunal villi, often producing secondary lactose intolerance.
Predisposing Factors
A.Travel to areas where cholera or Giardia is epidemic:
1.Ingestion of raw or undercooked seafood or drinks containing cholera-contaminated ice or water.
2.Ingestion of Giardia—contaminated water supplies.
B.Ingestion of food contaminated with Salmonella or Shigella. Foods that are often implicated are domestic fowl and eggs, custard-filled pastries, processed meats, foods warmed on steam tables, poultry, red meat, raw seafood, raw milk, rice, and bean sprouts due to the following:
1.Inadequate cooking time and temperatures.
2.Poor hygiene, lack of handwashing.
3.Improper storage of food.
4.Ingestion of fruits and vegetables contaminated by an infected person or by animal products.
C.Infection by person-to-person spread:
1.Day care centers: Rotavirus can be found on toys and hard surfaces.
2.Overcrowded environment, inadequate healthcare or education.
3.Schools/dormitories.
4.Nursing homes.
5.Banquet halls, cruise ships.
D.Contact with Salmonella-infected turtles, iguanas, and other reptiles.
E.Seasonal outbreaks:
1.Rotavirus and astrovirus occur from October to April.
2.Adenovirus occurs throughout the year.
3.Norovirus occurs throughout the year but tends to increase in cooler months (December–February).
Common Complaints
A.Abrupt onset of nausea and vomiting.
B.Abrupt onset of diarrhea.
C.Fever, sometimes.
Other Signs and Symptoms
A.Explosive flatulence.
B.Cramping abdominal pain.
C.Abdominal tenderness.
D.Frequent watery diarrhea.
E.Mucoid stools with or without blood.
F.Tenesmus.
G.Myalgia.
H.Headache.
I.Weakness.
J.Malaise.
Subjective Data
A.Review onset, duration, and course of symptoms, including presence of abdominal pain and frequency of bowel movements (BMs). Ask the patient if anyone else in the family has the same symptoms.
B.Ask the patient about travel history, including travel by cruise ships or travel to foreign countries and camping with ingestion of water from streams, springs, or untreated wells. Inquire regarding exposure to animals.
C.Ask the patient about crowded or unsanitary living conditions, use of day care centers, and institutional living.
D.Take a 24-hour diet history, including ingestion of prunes or beans.
E.Review diarrhea history:
1.How many stools?
2.How frequent are the diarrhea stools?
3.What color is the stool?
4.Does the stool contain mucus?
5.Has there been blood in the stool?
6.Does the patient have tenesmus (constant feeling for the need to pass stool)?
F.Inquire about other symptoms, such as fever or respiratory problems.
G.If the patient is an infant, ask caregiver about activity level, irritability, sleep pattern, fluid intake, and number of wet diapers.
H.Review drug history intake, including laxatives, antacids, antibiotics, quinine, or anticancer
medications.
I.Has the patient been vaccinated with the rotavirus vaccine?
Physical Examination
A.Check temperature, pulse, respirations, blood pressure (BP), and weight:
1.Bacterial infections: Temperatures between 101°F and 102°F.
2.Viral infections: Temperatures of 103°F and above.
3.Note hypotension and tachycardia.
B.Inspect:
1.Inspect general appearance; note if the patient is very ill.
2.Assess hydration status. Signs of dehydration:
a.Mild: Slightly dry buccal mucous membranes, increased thirst, decreased urine output.
b.Moderate: Sunken eyes, loss of skin turgor, dry buccal mucous membranes, decreased urine output.
c.Severe: Signs of moderate dehydration and one or more of the following: rapid thready pulse, tachypnea, lethargy, and postural hypotension.
C.Auscultate the abdomen for bowel sounds; note hyperactive bowel sounds, absent or hypoactive bowel sounds (common with botulism), and borborygmi.
D.Palpate the abdomen for diffuse tenderness, slight distenion, masses, rebound tenderness, and spasm.
E.Rectal exam: Check for masses, fissures, inflammation, perianal erythema, or stool in ampulla.
F.Neurologic exam:
1.Check for dizziness, difficulty swallowing, and other neurologic signs.
2.Neurologic signs and symptoms indicate botulism and require emergency intervention.
Diagnostic Tests
A.No immediate lab tests are required if dehydration is absent or mild and the patient feels well except for frequent diarrhea.
B.Complete blood count (CBC) with differential: Serologic studies may fail to differentiate between bacterial and viral pathogens.
C.Sedimentation rate: Elevated with infections or inflammation
D.Electrolytes, sodium, chlorides, potassium, and blood urea nitrogen (BUN).
E.Blood gases to assess acid–base balance, if indicated.
F.Blood cultures, if indicated.
G.Stool for guaiac, leukocytes, ova, and parasites; test specimens three times, every other day. Stool guaiac is usually negative in viral infections, positive in invasive bacterial infections. Large numbers of white cells in stool suggest inflammatory or invasive diarrhea, such as occurs with Shigella, Salmonella, Campylobacter, invasive E. coli, or Entamoeba. Mononuclear cells in stool are characteristic of salmonellosis.
H.Stool culture if blood or mucus, fever more than 24 hours, or leukocytes are present.
I.Special cultures for Campylobacter and cholera are required.
J.Urinalysis: Excludes urinary tract infection (UTI) as cause of nonspecific diarrhea; urine specific gravity to assess dehydration.
K.Sigmoidoscopy: Skip bowel prep with gross blood, large numbers of leukocytes in stool, or severe illness.
L.Culture food from suspected foci for Salmonella.
M.Real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) is the most widely used assay for detecting norovirus in stool, vomitus, and environmental specimens. The best detection is in stool specimens.
Differential Diagnoses
A.Gastroenteritis, bacterial and viral.
B.Acute viral hepatitis.
C.Acute appendicitis.
D.Cholecystitis.
E.Irritable bowel disease (IBD; ulcerative colitis [UC]/Crohn’s disease [CD]).
F.Pelvic inflammatory disease (PID).
G.Bowel obstruction for other causes.
H.Colorectal cancer (CRC).
I.Irritable bowel syndrome (IBS).
J.Microscopic colitis.
K.Malabsorption syndrome.
L.Postcholecystectomy syndrome.
M.Medication-induced.
N.Laxative abuse.
Plan
A.General interventions:
1.Meticulous handwashing is the single most important measure to decrease transmission. Hand sanitizers are an option when access to soap or clean water is limited.
2.Advise the patient to begin bed rest with progression to regular activities.
3.If the patient is diapered and/or incontinent, tell the patient or caregiver to adhere strictly to contact precautions. Alcohol-based handwashing may decrease the spread.
4.Diaper-changing areas should be separate from food preparation areas.
5.Chlorine-based disinfectants inactivate rotavirus and may prevent disease transmission from contact with environmental surfaces.
B. 
See Section III: Patient Teaching Guide Diarrhea.
C.Dietary management:
1.There are no specific dietary restrictions for patients diagnosed with acute gastroenteritis. As tolerated food intake should be advised. Small meals and low-residue foods are better tolerated. Soup, saltines, broiled or boiled salted starches (oats/cereal/potatoes), and bananas are good choices.
2.Hydration is one of the most important factors in the prevention of complications. For most patients, use of sports drinks, diluted juices, or broth is sufficient. Oral rehydration solutions may be implemented for moderate to severe cases.
3.See section Nausea and Vomiting Diet Suggestions
of Appendix B.
D.Pharmaceutical therapy:
1.The primary treatment for viral gastroenteritis is fluid replacement. There are no specific antiviral pharmaceutical therapies. Intravenous (IV) rehydration of fluids and electrolytes may be required in severe dehydration as evidenced by dry mucous membranes, hypotension, tachycardia, or mental status changes.
2.Antibiotics may or may not be prescribed according to the bacterial source. Antimicrobial therapy is not indicated for uncomplicated (noninvasive) gastroenteritis because therapy does not shorten duration of the disease and can prolong duration of excretion of Salmonella organisms.
3.Antidiarrheal therapy delays transit time and can reduce the severity and duration of abdominal cramping; however, it may prolong the course of some bacterial diarrhea such as Shigella and E. coli. In otherwise healthy patients younger than 65 years of age, if diarrhea is moderate to severe or if clinical signs of dehydration are evident, short term (1–2 days) use of loperamide may be used to facilitate oral rehydration.
4.An antiemetic such as ondansetron, which does not cause sedation, may be useful for 1 to 2 days if vomiting is severe enough to prevent oral rehydration.
5.Review all medications, herbal, and over-the-counter (OTC), to decrease or deprescribe other medications that may be triggering diarrhea.