Lecture 2 Infections Gi Tract (2)Presentation Transcript
Gastroenteritis, Infections of the GI Tract, and Diarrhea
Gastroenteritis is a nonspecific term for various pathologic states of the gastrointestinal tract.
The primary manifestation is diarrhea, but it may be accompanied by nausea, vomiting, and abdominal pain.
A universal definition of diarrhea does not exist, although patients seem to have no difficulty defining their own situation.
Although most definitions center on the frequency, consistency, and water content of stools
Defined as- Inflammation of the mucous membrane of both the stomach and intestine, usually causing nausea, vomiting, and diarrhea.
Acute gastroenteritis usually causes profuse watery diarrhea, often c nausea and vomiting, but without localized findings.
Between cramps, the abdomen is completely relaxed.
Cause of Gastroenteritis
Infectious agents usually cause acute gastroenteritis.
These agents cause diarrhea by adherence, mucosal invasion, enterotoxin production, and/or cytotoxin production.
These mechanisms result in increased fluid secretion and/or decreased absorption.
This produces an increased luminal fluid content that cannot be adequately reabsorbed, leading to dehydration and the loss of electrolytes and nutrients.
An endemic viral infection of young children
(6 mo-12 yrs)
is especially widespread during winter,
caused by strains of rotavirus ;
the incubation period is 2-4 days,
with symptoms lasting 3-5 days,
including abd. pain, diarrhea, fever, and vomiting.
Tx = Fluids (PO vs. IV)
An epidemic, highly communicable but rather mild disease of sudden onset,
caused by the epidemic gastroenteritis virus (especially Norwalk agent),
with an incubation period of 16-48 hrs
and a duration of 1-2 days,
affects all age groups;
infection is associated with some fever, abd. cramps, nausea, vomiting, diarrhea, and headache,
Causes of Vomiting and Diarrhea
G astrointestinal- Obstruction, Dymotility, Inflammation, Malabsorption, Lactose Intolerance, GI bleeding
A ppendicitis or aorta
S pecific diseases- Glaucoma, Torsion (ovary/testicle)
R x (prescription)-medication side effects
O bstetrics and Gynecology-pregnancy, preeclampsia, Hyperemesis gravidarum
E ndocrine or metabolic-thyrotoxicosis, DKA, Adrenal insufficiency
N eurologic-Vestibular, Migraine, encephalopathy, Hydrocephalus, Increased ICP (neoplasms, subdural, epidural, or subarrachnoid hemorrhage, cerebral edema)
E nvironmental-Food poisoning, envenomation, high altitude, acute radiation
R enal-Obstructive uropathy, renal colic
I nfection- gastroenteritis (viral, bacterial, parasitic), pyelonephritis, pneumonia (pertussis, Legionella), PID, Meningitis, Hepatitis, colitis, HIV
T umors-gastrinoma, thyroid ca, villous adenoma
I schemia- MI, Mesenteric ischemia, ischemia colitis
S upratentorial- Bulemia, psychosocial stress
Salmonella, Shigella, and Campylobacter species are the top 3 leading causes of bacterial diarrhea worldwide, followed closely by Aeromonas species
Acute symptoms may follow a wide variety of infectious & chemical agents
Ingestion may occur as a result of person to person contact, more commonly via water or food
The majority of food borne illnesses are caused by staphylococcus aureus from contaminated food being allowed to stand, producing endotoxins.
Salmonella & Clostridium follow staph poisoning as most common. They are found in meats.
Invasive Infection : The organism enters the mucosal cells, destroys them, causing diarrhea usually with blood in the stool.
Enterotoxic syndromes: The organisms do not invade the mucosa, but produce enterotoxins of which act as chemical mediators causing hypersecretion of the fluid. Little damage to the tissue is done.
Gastroenteritis Key Symptoms
Abdominal cramps (#1)
Profuse watery stools
Small volume stools
Bloody mucoid stools
Suprapubic pain relieved by BM
History of suspicious food eaten within the last 48 hrs, eating an unusual food (special fish) in a restaurant, or preparing food in an unconventional container (copper). Or a hx of similar illness in others who ate with the patient.
Physical Exam Findings
Diarrhea causing dehydration
Fever- usually indicates organism invasion
Hypotension- usually indicates dehydration and electrolyte imbalance
Rectal Exam- “to bleed or not to bleed”
Hemoccult of stool
CBC; If WBC count is elevated increased likelyhood of bacterial infection.
(If eosinophils present r/o parasitic infection).
If C. Difficile is suspected request cytotoxin of stool
With the exception of Giardiasis, amebiasis, C. difficile, salmonellosis, & shigellosis, practically all only need fluid replacement, glucose, and electrolyte control (IV NS, pedialyte)
Chemical poisons : onset immediate after ingestion of food like Ciguatera or scromboid (scrombotoxin found in fish)
Staphylococcal food poisoning : onset within hrs after eating contaminated food
Salmonella & Shigella infection : onset usually within 24-48 hrs (bacillary dysentery)
Giardiasis infection : onset of symptoms after one week with recurrent diarrhea.
Incubation period (cont.)
Clostridium difficile: Antimicrobial use within the last 2 weeks
Botulism : Associated Neurological symptoms after eating canned food. Symptoms within 24 hrs.
A h/o homosexuality : r/o AIDS, Shigella, Campylobacter jejuni, Salmonella, protozoalike Entamoeba, cryptosproidia, candida, giardiasis, and many others
Gastrointestinal Infectious Disorders
Hemorrhagic Colitis (E. coli O157:H7)
Pseudomembranous Colitis (C. difficile)
Enterotoxigenic E. coli
N/V/D/ abd cramps
This is the leading cause of viral gastroenteritis in the United States
Various caliciviruses, other than Norwalk virus, are likely responsible for many outbreaks of previously unidentified viral gastroenteritis.
This is the leading cause of gastroenteritis in children (> in winter), but can also be found in adults. Rotavirus may cause severe dehydration.
Severe Dehydration=thirst, oliguria, anuria, cramps, weakness, decrease turgor
Circulatory collapse= cyanosis, stupor, renal tubular necrosis, death
Metabolic Acidosis may be severe b/c of lost bicarbinate
Dx: stool cx,
Fecal Leukocytes (WBC’s) absent
Tx: Maintain fluid and electrolyte balance.
Tetracycline or doxycycline reduces duration of symptoms
Dysentery (bloody diarrhea)
Only need to ingest small inoculum
Fecal-Oral spread, and contaminated foods, also flies act as mechanical vectors
Epidemics occur c overcrowding and insufficient sanitation, and reinfection possible.
Young children- acute onset of sx: f/n/v/d/abd pain/distention
Within 3 days diarrhea becomes severe and bloody, often with pus, and mucus.
Dehydration can cause death; otherwise acute ds. resolves within several days. (Adults have milders sx)
Dx: stool cx, proctoscopy,
Fecal Leukocytes (WBC’s) PRESENT
Fluid replacement is critical
Bactrim or Cipro can shorten course of severe ds
DO NOT GIVE ANTI-DIARRHEALS, may prolong course
1. Gastroenteritis is most common form of Salmonellosis
2. Enteric Fever- Typhoid Fever
Eating foods produced from infected animals; meat, milk, poultry, eggs, and drinking contaminated water; and from fecal-oral trans.
Incubation period 8-48 hrs
Asymptomatic or symptoms develop within 2 days of eating infected food.
N/cramps/watery or bloody diarrhea/fever/ and sometimes vomiting
lasting 1-4 days
Dx: stool cx, Presence of fecal WBC’s variable
supportive (IV hydration)
Antibiotics usually not necessary for Salmonella gastroenteritis (Bactrim, Amp, or Cipro indicated in pt’s c increased risk of mortality, Typhoid fever, or Bacteremia)
Escherichia coli O157:H7
Produces a toxin that damages GI mucosa and vascular endothelial cells (vessels), other organs, particularly the kidneys.
Organism has bovine reservoir: unpasteurized milk and undercooked beef; Fecal-oral transmission also possible
S/S: Acute, severe abd cramps and watery diarrhea progresses to bloody diarrhea; low grade fever, uncomplicated lasts ~1wk; but complicated cases=high fever, hemolytic uremic syndrome (HUS) or thrombocytopenic purpura (TTP)
Dx: Stool cx; fecal leuks usually absent
Tx: Supportive (IV hydration), Abx do not help ; complications require aggressive management
Caused by antibiotic therapy which changes balance of normal intestinal flora, causing overgrowth of pathogen (most common causes clindamycin, ampicillin, and cephalosporins, although any can be cause)
Hospitalized pt’s on Abx at greatest risk
Usually within 2 wks after starting Abx, but may be as long as 6 wks after.
Illness often mild, but severe bloody diarrhea with abd cramps, fever, and dehydration may occur.
Dx: C. difficile toxin in stool is diagnostic; stool cx or sigmoidoscopy with visualization of pseudomembranes
Tx: D/C Abx if possible , may be sufficient
Metronidazole or PO vancomycin in more severe cases
Most commonly caused by bacteria (80%), Enterotoxigenic E. coli, Shigella, Campylobacter jejuni being the most common pathogens.
Chronic watery diarrhea
Up to 10 or more loose stools per day, usually without blood or mucus.
Fever is rare
Self limiting within 1-5 days
Dx: stool cx for pt’s c f/dysentery, and those that don’t respond to abx
Tx: mostly symptomatic therapy (IV hydration)
If high fever, or dysentery tx c Cipro (not antidiarrheals)
Prevention: Prophylaxis is recommended for those with significant underlying ds.
Pepto-bismol is effective, but may interfere with the absorption of other medications (tetracycline/doxycycline) used for malaria prophylaxis, and it also carries the same toxicity as other salicylates (Reyes Syndrome) and turns the tongue and stool black, so it is rarely used.
General Bacterial Overgrowth Treatment
Usually self limiting
Correct the anatomic defect when possible.
Empiric antibiotic trial can be used as a diagnostic and therapeutic maneuver.
Ciprofloxacin (or combo c Metronidazole)
(However often not necessary, unless dysenteric)
Protozoal infection signs/symptoms
Wheezing or hemoptysis due to pulmonary migration of larva (lofflers syndrome)
Passage of parasites
Bowel obstruction (as found in taenia and ascarisis)
Travel to underdeveloped areas
Outbreak of associated illness (Giardia, Trichinella)
Daycare exposure (Giardia)
Homosexual behavior (Giardia, Entamoebia)
Diet: uncooked foods
Excessive gas or abdominal distention
Fecal smears (look for WBC’s, RBC’s, ova & parasites)
CBC: eosinophilia , iron deficiency
Graham’s Test: scotch tape test
Chemotherapeutic agents for each parasite
Etiology: Enterobius Vermicularis
Outbreaks common in schools
Transmission by fecal-oral ingestion
Key symptom is rectal pruritis
Test is scotch tape test
Treatment: Vermox , Antiminth (one dose, then repeat in one week)
Etiology: Giardia Lamblia
Most common water borne infection
Abd. Pain & cramps
Fatty, greasy, foul smelling stool (steatorrhea)
Test: Microscopic exam of stool for cysts (also the ELISA antigen test)
It is an upper GI parasite and stool examination can be negative
Treatment: Metronidazole (Flagyl)
Etiology: Entamoeba hitolytica
Found in 4% of the population
Found mostly in cecum & ascending colon, invading the mucosa. Can travel to liver, lung, brain
Asymptomatic to diarrhea
Flatus, fever, hepatitis
Shoulder pain due to hepatitis
No symptoms – no signs
Pulmonary (pneumonia- emphysema)
Examine stool for cyst –trophozoites
Most common intestinal helminth
Etiology: Ascaris lumbricoides (the large intestine round worm)
Transmitted by contaminated food
Human feces as fertilizer
Pulmonary phase (Loffler’s syndrome)
Intestinal phase (eggs in stool)
Penetrate the intestine & invade liver, lung, heart
Tx: Albendazole and Pyrantel pamoate
Cestodes (segmented worms)
Adults live in GI tract, larvae can be found in almost any organ (neuro, muscle, eye) (cysticercosis )
Fish, beef, pork, dog , cats, fleas, snakes, birds, and other mammals can carry the tapeworm larva, humans can be the definitive host or the intermediate host
From 5mm to over 25 meters in length
Humans are the only host for this whipworm and one of the most common parasitic infections in the U.S.