Gastroenteritis Diarrhea, vomiting, cramping –Increased fluid output, more than 4-5, watery bowel movements per day Acute diarrhea – symptoms for less than 2 weeks –Exception: C. diff sx can last longer
Pathophysiology Viruses damage the small intestinal villi, decreasing intestinal surface area and unmasking ongoing fluid secretion by enteric crypts Rotavirus produces an enterotoxin that induces secretion and contributes to the watery diarrhea
Pathophysiology Invasive bacteria cause mucosal ulceration and abscess formation with an inflammatory response (WBCs in stool) Bacterial toxins may influence enteric and extraenteric cellular processes (HUS, etc) Other noninvasive bacteria and protozoa adhere to the gut wall, causing inflammation
Patient Evaluation Duration of symptoms Quantity (frequency of stools) Quality (watery) Fever Hematochezia – visible blood in stool S/S of dehydration Other sx: N/V, abd pain, tenesmus, anorexia Recent travel, recent abx use, hepatitis risk Other family members sick? Ability to take PO fluids
Physical Exam Jaundice Hydration status – check for signs of dehydration Stool Guaiac – occult blood Abdominal tenderness, bowel sounds Mental status
Oral Rehydration Replace water, salt, sugars lost due to diarrhea, vomiting In mildly dehydrated patient, it is first line therapy before IV rehydration. Formulas are based on patient weight, degree of dehydration 75 ml/kg over 4 hrs every 2 min
Enteric Illness, categories Non-specific gastroenteritis Gastroenteritis with bloody diarrhea Extraintestinal illness Non-infectious causes of GI symptoms
Nonspecific Gastroenteritis Diarrhea without high fever or bloody stool May have: cramps, low grade fever, headache, malaise, dehydration, N/V Etiology: Viral (Norwalk-like viruses, Rotavirus), protozoal (giardia, crypto), foodborne toxins (S. aureus), traveller’s diarrhea, noninfectious causes.
Gastroenteritis with bloody diarrhea Bloody stools with fever, +/- vomiting: Consider Salmonella, Shigella, Campylobacter (bacterial) Bloody stools without fever: Could be above or E. coli 0157:H7.
GI illness with Extraintestinal Disease Jaundice: Hepatitis A (we’ll get there in a little bit) Meningitis: Listeria, salmonella Arthritis: Campylobacter, salmonella Flaccid paralysis and cranial neuropathies: C. botulinum (Botulism) HUS: E. coli 0157:H7
Noninfectious causes of GI sx Otitis media, Group A Streptococcal infection, irritable bowel syndrome, inflammatory colitis, stress, medications, gallbladder disease, peptic ulcer disease
Staphylococcal Food Toxin S/S: Vomiting, severe cramping, low grade fever, diarrhea (no blood in stool) Incubation: VERY short – 30 minutes to a few hours. Complications: None, spontaneous recovery Diagnosis: No specific test available. Clinical dx.
Staphylococcal Food Toxin Treatment: Supportive – rest, hydration, compazine or other antiemetic for persistent vomiting Origin: Toxin producing S. aureus strains, usually from human skin, inoculate food, multiply at room temp. Toxins not destroyed by reheating. Other toxin producing bacteria: Clostridium perfringens, Bacillus cereus.
Staphylococcal Food Toxin Prevention –Decrease food handling –Do not allow foods to sit at room temp. for long periods –Glove use by food handlers –Exclude persons from food handling when obvious skin infections are present.
Salmonella Agent: Multiple subtypes of Salmonella species (S. enteritidis, S. typhimurium are most common) Reservoir: Birds (chickens, turkeys), reptiles, others Occurrence: Common Transmission: Undercooked meat/eggs, cross contamination by meat juices, unpasteurized milk, handling reptiles
Salmonella Incubation: 6-72 hours (usually 10-12) Diagnosis: Stool culture Clinical: Diarrhea, often bloody, fever, cramps, vomiting Complications (elderly, immunocomp.): Arthritis, meningitis, sepsis. Treatment: Usually supportive. Quinolones if severe or if immunocompromised.
Campylobacter Agent: C. jejuni Reservoir: Poultry, cattle, others Occurrence: Common Transmission: Undercooked poultry, cross contamination, unpasteurized milk Incubation: 3-5 days Diagnosis: Stool culture
E. Coli 0157:H7 Agent: As above Reservoir: Cattle (and foods contaminated with cow feces) Occurrence: Less common than Salmonella and Campy, but increasing Transmission: Ingestion of undercooked beef, cross contamination, unwashed contaminated fruits & veggies, person to person, water contamination. HIGHLY transmissible.
E. Coli 0157:H7 Incubation: 2-7 days Clinical: Watery diarrhea progressing to bloody diarrhea after a few days. Fever usually absent. Cramps, vomiting. Complications: 5-10% of kids younger than 5 will develop HUS, a life threatening multisystem disease. Can occur in adults.
E. Coli 0157:H7 Diagnosis: Stool culture, toxin assay Treatment: Supportive. Antibiotics usually avoided (can increase HUS) Prevention: Thorough cooking of ground beef, avoid cross contamination with beef juices, wash fruits/veggies, pasteurization. Early diagnosis will prevent person to person transmission.
Shigella Agent: S. sonnei, S. flexneri, others Reservoir: Humans Transmission: Person to person, foodborne, flies. Clinical: Fever, bloody diarrhea, cramps, vomiting. Patients often appear toxic. Diagnosis: Stool culture
Shigella Complications: Sepsis, meningitis Treatment: Quinolones, hydration Communicability: Extremely high Prevention: Early diagnosis and isolation, hand washing, food and water hygiene Occurrence: Rare locally, high in third world countries.
Clostridium difficile Most common antibiotic associated diarrhea- due to changes in colonic bacterial fermentation of carbohydrates Colitis associated with toxin produced by C. diff. Hospitalized, immunocompromised are most susceptible
Clostridium difficile Antibiotics disrupt the normal flora, C. diff. flourishes (carried asymptomatically by 3-8% healthy adults). Any abx can trigger, but most common are: cephalosporins, penicillins, clindamycin, flouroquinolones Sx start during or after abx therapy, may be delayed 8 weeks Easily transmitted in hospital setting
Clostridium difficile Toxins (A- enterotoxin & B-cytotoxin) have effect on colon- secretes fluid, develops pseudomembranes (discrete yellow-white plaques), easily dislodged. Diagnosed by C. diff toxins in stool. EIA rapid toxin A & B. Treat with Metronidazole 500 mg po tid x10- 14 d. D/c other abx if possible. Infection control measures to reduce spread in hospital settings.
Viral Gastroenteritis Most common cause of infectious diarrhea in US Infect epithelium of small intestine Diarrhea is watery WBC’s and visible blood are rare 4 categories: Rotavirus, Claicivirus (norovirus), Astroviurs, Enteric Adenovirus.
Rotavirus Most common cause of diarrhea in young children Highly contagious: fecal-oral. Incubation 1-3 days, lasts 4-8 days Dehydration and hospitalization common in young children Diagnose by EIA antigen in stool Treat with oral rehydration or IV Oral vaccine now available (controversial)
Calcivirus Infect older children and adults Nonspecific, self-limiting Large water-borne and food-borne outbreaks occur, fecal-oral Incubation 24-48 hrs, lasts 12-60 hrs No commercial tests to diagnose Treatment supportive (oral rehydration)
Giardiasis Agent: Giardia lamblia Reservoir: Human and animal stool Occurrence: Very common Transmission: fecal-oral, contaminated water or food Incubation: 3-10 days
Giardiasis Clinical: Persistent or recurring diarrhea, bloating, cramps, steatorrhea (frothy fatty stool), weight loss. No blood in stool. Diagnosis: Ova and parasite slide or direct antigen test. Treatment: Metronidazole or other antiparasitic Prevention: Water filtration, avoid drinking untreated surface water.
Traveler’s Diarrhea Usually caused by endemic bacteria, not one specific agent. Most common is E. coli. Usually benign, self-limiting Prophylactic abx for immunocomp. Treat with flouroquinolone if bloody diarrhea and fever
Liver Function Tests Serum Aminotransferases (ALT and AST). ALT usually >8x upper limit of normal Serum and urine Bilirubin. (N either sensitive nor specific for viral hepatitis) Serum Alkaline Phosphatase Additionally: LDH, GGTP, Albumin, Prothrombin Time
Lab and Physical Findings In viral hepatitis ALT is usually higher than AST, as opposed to alcoholic hepatitis Many people are entirely asymptomatic or mildly symptomatic with jaundice (especially HBV and HCV infections) Children <6yrs with acute HAV infection are usually asymptomatic, rarely jaundiced Table p 238-239 Wallach.
Acute Viral Hepatitis Any combination of: malaise, fever, nausea, vomiting, abdominal pain or fullness, diarrhea, myalgias, headache. Can have +/- jaundice, dark urine AND abrupt, dramatic elevation of ALT/AST Hepatitis serologies to diagnose, discussed in lab lecture.
Hepatits A Most common cause of acute viral hepatitis Small RNA picornavirus About 30 day incubation Fecal-oral transmission Epidemics or sporadic cases Source: contaminated water, food (shellfish) No chronicity, no carrier state
Hepatitis A Most children asymptomatic, most adults symptomatic Low mortality Excreted in feces up to 2wks before illness, rarely after first week of illness Only viral hepatitis causing spiking fevers Viremia intermittent
Hepatitis A Vaccine Available since the mid 1990’s Recommended for: –children 12-23 months –International travelers –People who live or work where there are outbreaks –Some other high risk groups
Hepatitis A Treatment Symptomatic treatment (rest, fluids, etc) Avoid strenuous physical exertion, alcohol and hepatotoxins IG given to close contacts Vaccination of close contacts
Hepatitis B Second most common cause of acute viral hepatitis dsDNA Hepadnaviridae Most complex hepatitis virus Infective particle made up of viral core plus an outer surface coat Transmission: sexual, parenteral, perinatal
Hepatitis B Can become chronic (5-10% of acute), may result in cirrhosis, hepatocellular ca Often asymptomatic or nonspecific symptoms Incubation 6-12 weeks If recover from HBV infection, will be immune
Hepatitis B Vaccination Available since the 1980’s Routine childhood vaccine (3 doses) –Given at birth to babies of HBsAg pos mothers Anti-HBs response Other high risk groups Post exposure prophylaxis: HBIG and start vaccine
Hepatitis B Treatment HBIG given within 7 days of exposure Initiation of HBV vaccine series Symptomatic treatment (rest, fluids, etc) Avoid strenuous physical exertion, alcohol and hepatotoxins
Hepatitis C Single-stranded RNA flavivirus 6 major subtypes with varying genotypes Primarily transmitted by blood –Injection drug use >50% of cases –Posttransfusion, hemodialysis, tattoos, body piercing –Sexual and vertical transmission uncommon, but increased risk with multiple sex partners. –HIV patients at increased risk
Hepatitis C Incubation period: 6-7 weeks avg, ranges from 2-26 weeks Clinical illness often mild, asymptomatic Chronicity common: >70%, may progress to cirrhosis, carcinoma Leading cause of liver transplant No protective antibody response
Hepatitis C Prolonged viremia Aminotransferases will be elevated off and on (can have ALT >7x normal) Diagnose with Anti-HCV EIA
Hepatitis C Treatment Interferon or peginterferon for 6-24 weeks decreases risk of chronicity May reserve treatment for those that do not clear virus in 3-4 months (monitor HCV-RNA). Clearance more likely in symptomatic than asymptomatic pts. Liver transplantation in acute liver failure
Hepatitis C NO immunization No post exposure prophylaxis Chronicity common Different genotypes respond differently to therapy
Other Hepatitis Viruses Hepatitis D (Delta). –Due to ssRNA virus. –Always associated with Hepatitis B. –Acute or chronic. –Often severe, high mortality. Hepatitis E. Due to ssRNA virus. –Rare, occurs in endemic areas.
Chronic Hepatitis HBV – 5-10% of acute infections HCV - >70% of acute infections HDV – with HBV coinfection or superinfection
Chronic Hepatitis Elevated aminotransferases for more than 6 months May lead to cirrhosis, hepatocellular carcinoma Liver transplantation indicated for end- stage disease