GI

Diarrhea and Gastroenteritis

Consistency is much more important than frequency to define diarrhea…

Types

  1. Watery, osmotic (e.g, Laxative-induced diarrhea),
  2. secretory (eg, microscopic colitis)
  3. Functional – mucus (typically from irritable bowel syndrome)
  4. Inflammatory – blood +/- pus (eg, IBD as in Chron’s and UC, some invasive bacteria)
  5. Fatty (steatorrhea)

Case Approach:

Two main questions to answer are:
  1. Acute or Chronic
  2. Watery (non-bloody) or Bloody

Blood and WBCs in stool

Salmonella: contaminated poultry and eggs; more common in patients with SCD and achlorhydria
 
Campylobacter jejuni: most common cause, rarely associated with GBS
 
E. coli  O157:H7 — undercooked hamburger meat; hemolytic uremic syndrome (HUS)
 
Shigella: 2nd most common association with HUS
 
Vibrio parahaemolyticus: shellfish and cruise ships
Vibrio vulnificus: raw shellfish, h/o liver disease, iron overload and bullous skin lesions
                          * may cause invasive, life-theratening disease in immunocompromised patients or those with liver disease
 
Yersinia enterocolitica: high affinity for iron, hemochromatosis, blood transfusions; can mimic appendicitis or Chron’s disease
               tends to infect the cecum rather than distal colon
 
Clostridium difficile:  previous antibiotic use;  white and red cells in stool
Clostridium botulinum :   infected canned foods
Clostridium perfringens:  meats taht have been contaminated with spores by being unrefrigerated
 The major protozoan associated with blood in the stool is Entamoeba histolytica.

No Blood and WBCs in stool

  • Viral
  • Giardia lamblia
  • Cryptosporidiosis/ isospora: AIDS with CD4 <50-100; detected by modified acid fast stain (treat underlying AIDS, nitazoxanide which is superior to paromomycin)
  • Bacillus cereus: vomiting –  warmed or slowly re-heated fried rice
  • Staphylococcus: vomiting
Dx
  • The best initial test is for  blood and/or fecal leukocytes with methylene blue testing
  • Stool lactoferrin has greater sensitivity and specificity compared with stool leukocytes
  • The most accurate test = stool culture to determine the specific type
  • Modified acid-fast test for cryptosporidiosis because routine fecal O/P does not reliably pick up
  • ELISA stool antigen test for Giardiasis (90% sensitivity); 3 fecal O/P for Giadria has lesser sensitivity (80%) than single stool antigen test
Tx
  • supportive
  • consider antibiotics only when abdominal pain, blood in the stool, and fever
  • best initial empirical = ciprofloxacin or other fluoroquinolones +/- metronidazole
  • TMP/SMX for Isopora
  • Doxycycline for Vibrio vulnificus
  • Rifaximin for traveler’s diarrhea

Giardia lamblia

  • flagellated protozoan, often acquired during hiking/ camping activities, by drinking unpurified water from streams
  • affects small bowel (duodenum and proximal jejunum) producing upper GI symptoms such as frequent burping, bloating, distention, flatus, and loose, nonbloody, foul-smelling and fatty diarrhea (steathorrhea).
Dx:
  • duodenal aspirate/ biopsy/ immunoassay
  • stool for parasites/ eggs
  • stool ELISA
Tx-
  •   metronidazole/ Tinidazole
**Giardiasis is the only common primary infection causing chronic malabsorption.

Pseudomembranous colitis

caused by C. difficile; Gram +ve superbug whose spores are contagious (fecal-oral or from the environment)
Girotra’s triad
  1. Increasing abdominal pain/distention and diarrhea
  2. Leukocytosis > 18,000
  3. Hemodynamic instability
Tx
  • Stop the causative antibiotic (if possible)
  • No treatment if asymptomatic
  • Metronidazole for symptomatic cases
  • Vancomycin may be better in severe disease
  • Consider surgery (urgent colectomy) if complications such as toxic megacolon developed; raised LDH and in deteriorating patient

Initial evaluation of Chronic diarrhea

Fat:
  • most useful screening test is stool for fat (Sudan red stain)
  • confirm with 72-hour stool for fecal fat (gold standard for steatorrhea)
  • Steatorrhea is most prominent with pancreatic insufficiency; all require a sweat chloride (to rule out CF and Schwachman-Diamond $)
  • Serum trypsinogen may also be used
  • Screen for carbohydrate malabsorption — measure reducing substances in stool (Clinitest)
  • Breath hydrogen test
  • Protein loss — difficult to evaluate directly
  • Screen with spot stool alpha-1 anti-trypsin level

Differential Diagnoses of Chronic Diarrhea

  1. most common infectious cause = Giadiasis
  2. most common congenital cause with malabsorption = cystic fibrosis
  3. most common anomaly cause with incomplete bowel obstruction + malabsorption= malrotation

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