1. DIARRHEA

2. Diarrhea
Abnormally liquid or unformed(loosely) stools, an increased frequency as a symptom
Decrease in stool consistency, an increase in stool volume, an increase in number of bowel movements, or any combination of these three changes
Is a sign, a quantitative increase in stool water or weight of >200–225 ml or g/day

3. Individuals consuming higher fiber diet … normally have a stool weight of up to 400 g/24 h
Thus clinician must clarify what means by diarrhea

4. acute if <2 weeks , Persistent 2–4 weeks, chronic if >4 weeks in duration
DDx : stool totaling <200 g/day
Pseudodiarrhea :frequent passage of small volumes of stool … with rectal urgency, tenesmus, or a feeling of incomplete evacuation … IBS or proctitis

5. Fecal incontinence :involuntary discharge of rectal contents … neuromuscular disorders or structural anorectal problems ,diarrhea and urgency especially if severe
Overflow diarrhea … in nursing home patients due to fecal impaction that is readily detectable by rectal examination
A careful history and physical examination generally allow these conditions to be discriminated from true diarrhea

6. ACUTE DIARREA
More than 90% of cases …. Infectious …accompanied by vomiting, fever, and abdominal pain
The remaining 10% :medications, toxic ingestions, ischemia, food indiscretions, and other conditions

7. Infectious Agents
Fecaloral transmission or, ingestion of food or water contaminated with pathogens from human or animal feces
In the immunocompetent person … resident fecal microflora, containing >500 taxonomically species …. are rarely the source of diarrhea
Disturbances of flora by antibiotics … diarrhea … reducing digestive function or pathogens overgrowth, Clostridium difficile

8. Acute infection …. when the ingested agent … bypasses host’s mucosal immune and nonimmune defenses (gastric acid, digestive enzymes, mucus secretion, peristalsis, and suppressive resident flora)
Dx :Established clinical associations with specific enteropathogens

9. 1. Travelers
Nearly 40% of tourists to endemic regions of Latin America, Africa, and Asia
most commonly due to enterotoxigenic or enteroaggregative Escherichia coli ,Campylobacter, Shigella, Aeromonas, norovirus, Coronavirus, and Salmonella
Visitors to Russia (especially St. Petersburg) : Giardia
Visitors to Nepal may acquire Cyclospora
Campers, backpackers, and swimmers in wilderness areas :Giardia
Cruise ships : norovirus

10. 2. Consumers of certain foods
picnic, banquet, or restaurant … Salmonella, Campylobacter, or Shigella from chicken
undercooked hamburger …enterohemorrhagic E. coli (O157:H7)
Bacillus cereus : fried rice or other reheated food
Staphylococcus aureus or Salmonella .. mayonnaise or creams;
Salmonella from eggs; Listeria from uncooked foods or soft cheeses;
Vibrio species, Salmonella, or acute hepatitis A … seafood, especially if raw

11. 3. Immunodeficient persons
Primary immunodeficiency (e.g., IgA deficiency, common variable hypogammaglobulinemia, chronic granulomatous disease)
Secondary immunodeficiency states(e.g., AIDS, senescence, pharmacologic suppression)
AIDS, opportunistic infections, such as by Mycobacterium species, certain viruses (CMV , HSV , adenovirus), and protozoa (Cryptosporidium, Isospora belli, Microsporida, and Blastocystis hominis)

12. Agents transmitted venereally per rectum (e. g
Agents transmitted venereally per rectum (e.g., Neisseria gonorrhoeae, Treponema pallidum, Chlamydia)…. may contribute to proctocolitis
In hemochromatosis are especially prone to invasive, even fatal, enteric infections with Vibrio species and Yersinia … avoid raw fish

13. 4. Daycare attendees and their family members :Shigella, Giardia, Cryptosporidium, rotavirus
5. Institutionalized persons …. hospitals and long-term care facilities … variety of microorganisms ,C. difficile(no antibiotic use and may be acquired in the community)

15. Yersinia invades the terminal ileal and proximal colon mucosa and may cause especially severe abdominal pain with tenderness mimicking acute appendicitis.
Infectious diarrhea with systemic manifestations
Reactive arthritis (Reiter’s syndrome), arthritis, urethritis, and conjunctivitis may accompany or follow infections by Salmonella, Campylobacter, Shigella, and Yersinia.
Yersiniosis may lead to an autoimmune-type thyroiditis, pericarditis, glomerulonephritis
Hemolytic-uremic syndrome :enterohemorrhagic E. coli (O157:H7) and Shigella , high mortality rate

16. Postinfectious IBS syndrome … complication of infectious diarrhea
Acute gastroenteritis may precede … celiac disease or Crohn’s disease
Acute diarrhea ,major symptom viral hepatitis, listeriosis, legionellosis, and toxic shock syndrome

17. Other Causes : Side effects medications(antibiotics, cardiac antidysrhythmics, antihypertensives, NSAIDs, certain antidepressants, chemotherapeutic agents, bronchodilators, antacids, and laxatives
Colonic diverticulitis and graft-versus-host disease, Occlusive or nonocclusive ischemic colitis, organophosphate insecticides; amanita and other mushrooms; arsenic , Acute anaphylaxis to food ingestion, IBD

18. APPROACH TO THE PATIENT:
Depends on its severity and duration and on various host factors
Most episodes of acute diarrhea are mild and self-limited
Indications for evaluation : profuse diarrhea with dehydration, grossly bloody stools, fever ≥38.5°C (≥101°F), duration >48 h without improvement, recent antibiotic use, new community outbreaks, associated severe abdominal pain in patients >50 years, and elderly (≥70 years) or immunocompromised patients

19. In moderately severe febrile diarrhea with fecal leukocytes (or fecal leukocyte proteins, such as calprotectin) or with gross blood, a diagnostic evaluation might be avoided …. an empirical antibiotic trial

20. Severe acute infectious diarrhea
microbiologic analysis of the stool & Workup includes cultures for bacterial and viral pathogens, direct inspection for ova and parasites, and immunoassays for certain bacterial toxins (C. difficile), viral antigens (rotavirus), and protozoal antigens (Giardia, E. histolytica)

21. Persistent diarrhea
Giardia ,C. difficile (especially if antibiotics administered), E.histolytica, Cryptosporidium, Campylobacter, IBD, noninfectious acute diarrhea such as ischemic colitis, diverticulitis, or partial bowel obstruction
Stool studies, flexible sigmoidoscopy with biopsies and upper endoscopy with duodenal aspirates and biopsies , abdominal CTscanning

22. Brainerd diarrhea : an increasingly recognized, an abrupt-onset diarrhea that persists for at least 4 weeks, but may last 1–3 years, and is thought to be of infectious origin
It may be associated with subtle inflammation of the distal small intestine or proximal colon

24. TREATMENT
Fluid and electrolyte replacement are of central importance to death(IV & Oral)
Profoundly dehydrated patients, especially infants and the elderly, require IV rehydration.
Loperamide(antimotility and antisecretory) :moderately severe nonfebrile and nonbloody diarrhea
Such agents should be avoided in febrile dysentery, which may be exacerbated or prolonged .

25. Bismuth subsalicylate may reduce of vomiting and diarrhea but should not be used to treat immunocompromised patients or with renal impairment because risk of bismuth encephalopathy

26. Antibiotics indication: moderately to severely ill patients with febrile dysentery empirically without diagnostic evaluation(quinolone), giardiasis(metronidazole) , immunocompromised, mechanical heart valves or recent vascular grafts, elderly
Bismuth subsalicylate may reduce the frequency of traveler’s diarrhea
Selection of antibiotics and dosage(specific pathogens, geographic patterns of resistance, and conditions found)

27. Antibiotics prophylaxis :traveling to high-risk countries in whom with immunocompromise, IBD, hemochromatosis, or gastric achlorhydria
Ciprofloxacin, azithromycin, or rifaximin may reduce bacterial diarrhea in such travelers by 90%
rifaximin is not suitable for invasive disease, but rather as treatment for uncomplicated traveler’s diarrhea.

28. CHRONIC DIARRHEA
Diarrhea >4 weeks …. evaluation to exclude serious underlying pathology
Most of the causes are noninfectious

29. Secretory diarrhea
Derangements in fluid and electrolyte transport across the enterocolonic mucosa ,watery, large-volume fecal outputs ,typically painless and persist with fasting
no malabsorbed solute, stool osmolality with normal endogenous electrolytes without fecal osmotic gap

30. Medications: stimulant laxatives(senna, cascara, bisacodyl, ricinoleic acid [castor oil], ethanol)
Bowel resection, mucosal disease, or enterocolic fistula : worsen with eating ,disease (Crohn’s ileitis) or resection of <100 cm TI
Hormones :carcinoid tumors , Gastrinoma, pancreatic cholera(VIPoma), Medullary carcinoma of the thyroid, Systemic mastocytosis, Large colorectal villous adenoma
Congenital defects in ion absorption : congenital chloridorrhea

31. Osmotic diarrhea
ingested, poorly absorbable, osmotically active solutes, ceases with fasting or with discontinuation of the causative agent
Osmotic laxative :magnesium-containing antacid, stool osmotic gap (>50 mosmol/L): serum osmolarity (typically 290 mosmol/kg) – (2 × [fecal sodium + potassium concentration]).

32. Carbohydrate malabsorption: acquired or congenital defects in brush-border disaccharidases and other enzymes ..osmotic diarrhea with a low pH
Wheat and FODMAP intolerance 
nonceliac gluten intolerance
impaired intestinal or colonic barrier function and intolerance of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs)

33. Steatorrheal Causes
Fat malabsorption … greasy, foulsmelling, difficult-to-flush diarrhea with weight loss and nutritional deficiencies due to concomitant malabsorption of amino acids and vitamins
Quantitatively, steatorrhea is defined as stool fat exceeding the normal 7 g/d; rapid-transit diarrhea may result in fecal fat up to 14 g/d; daily fecal fat averages 15–25 g with small-intestinal diseases and is often >32 g with pancreatic exocrine insufficiency

34. Steatorrheal Causes
Intraluminal maldigestion: Chronic pancreatitis, cystic fibrosis; pancreatic duct obstruction; somatostatinom , Bacterial overgrowth ,cirrhosis or biliary obstruction
Mucosal malabsorption : celiac disease, Tropical sprue , Whipple’s disease, Abetalipoproteinemia
Postmucosal lymphatic obstruction: congenital intestinal lymphangiectasia or acquired lymphatic obstruction secondary to trauma, tumor, cardiac disease or infection

35. Inflammatory Causes Idiopathic inflammatory bowel disease
Primary or secondary forms of immunodeficiency selective IgA deficiency ,common variable hypogammaglobulinemi
Eosinophilic gastroenteritis
Other causes: radiation enterocolitis, chronic graft-versus-host disease, Behcet’s syndrome, Cronkhite-Canada syndrome

36. Dysmotility Causes :Rapid transit … Hyperthyroidism ,carcinoid syndrome, certain drugs (prostaglandins, prokinetic agents), Diabetic diarrhea
Factitial Causes : Munchausen syndrome (deception or self-injury for secondary gain)