The epidemiology and etiology of diarrhea

1. The epidemiology and etiology of diarrhea

2. Diarrhea in young children • 3-4 episodes /child / year • 3200 000death/ year • Causes about 30% of infant death in developing countries • 80% death due to diarrhea occur in first years of life • Diarrhea is an important cause of malnutrition

3. Three clinical types of diarrhea • Acute watery diarrhea dehydration ,potassium loss • Bloody diarrhea tissue damage, toxemia • Persistent diarrhea malnutrition

4. Host factorsthat increase susceptibility to diarrhea • Failing to breast - feed until at least 2 years • Malnutrition • Measles • immunosuppression

5. Behavioral risk factors for diarrhea • Inadequate breast feeding • Using feeding bottles • Eating food hours after cooking it • Drinking contaminated water • Not washing soiled hands • Not disposing of feces

6. Prevention of diarrhea( host factors) • Breast feed at least 2 years • Give plenty of good food ,start at age 4-6month • Immunize against measles

7. Fluids for home therapy • ORS solution • Water • Food - based fluids soup rice water Yoghurt drink Glucose water

8. Age of diarrhea • Most diarrhea episodes occur during the first 2 years of life • Incidence is highest in the age group 6-11 month • Declining levels of maternally acquired antibodies • The lack of active immunity in the infant • The introduction of food

9. seasonality • In temperate climate ; bacterial diarrhea occur more frequently during the warm season whereas the peak Viral diarrhea particularly rotavirus is during the winter • In the tropical areas; rotavirus diarrhea occurs throughout the year and increasing in cool month Whereas bacterial diarrheas peak during warmer ,rainy season • The incidence persistent diarrhea follows the same seasonal pattern as that acute watery diarrhea

10. Etiology of diarrhea • Rotavirus • Enterotoxigenic Escherichia coli • Shigella • Campylobacter jejuni • cryptosporidium • Vibrio cholera • salmonella (Non thyphoid ) • Entropathogenic Escherchia coli

11. Pathogenic mechanisms ( viruses) • Replicate within the villous epithelium of small bowel • Patchy epithelialcell destruction and villous shortening • The Loss of normally absorptive villous cells • Replacement immature , secretary ,crypt- like cells • Loss of disaccharides , especially lactose

12. Pathogenic mechanisms )bacteria) • Mucosal adhesionto avoid being swept away Entrotoxicogenic E.coli ,vibrio .cholera • Toxins that cause secretion that reduce the absorption of Naand increase the secretion of chloride Entrotixigenic E.coli , v.cholera • Mucosal invasionoccurs in the colon and distal ileum and destroying mucosal epithelial cells and cause bloody diarrhea Shigella ,C.jejuni ,entroinvasive E. coli and salmonella

13. Pathogenic mechanisms )protozoa) • Mucosal adhesionand cause shortening of the villi G,lambelia , cryptosporidum • Mucosal invasion in the colon or ileum and causing micro absess and ulcer E, histolitica

14. Campilobacter jejuni • C,jejunicauses disease mostly in infants • C,jejunialso infects animals and spread by contact with their • feces or consumption of contaminated food , milk , or water • C,jejuni can cause watery diarrhea or dysentery • Fever may be preset and episodes are not sever and last 2-5 days • Erythromycin shorten the illness

15. cryptosporidium • This parasite causes diarrhea in infants immunodeficient patients , and a variety of domestic animals • Infection is frequent in developing countries • Most episodes of illness occur in the first year of life • Diarrhea is usually neither severe nor prolonged • Diarrhea is sever in malnutrition , or AIDS , immunodeficient patients

16. Prevention of diarrhea • Give only breast milk for first 4-6 month • Do not use feeding bottle • Prepare and store food safely • Use clean water for drinking • Wash hands when soiled • Dispose of faeces safely

17. Treatment of acute diarrhea the main points • Replace lost water and salt • Continue to feed

18. Benefit of antibiotics in acute diarrhea • Helpful for patients with ; 5-15% Bloody diarrhea Suspected cholera with severe dehydration • No practical value for others because ; 85-95% Ineffective for pathogen Pathogen not known

19. Treatment acute diarrhea other points • Only give antibiotic for ; Bloody diarrhea Suspected cholera with severe dehydration • Only give anti protozoals ; No response to treatment for shigella Proven amebiasis

20. Treatment of diarrhea • Replacement of fluids and electrolytes • Feeding should be continued in all types of diarrhea • Antimicrobial and anti parasitic agents should not be used

21. Treatment of diarrhea • Antimicrobial and anti parasitic agents should not be used exception is ; • Dysentery • Suspected cholera with sever dehydration • Persistent diarrhea when trophozoites or cysts of giardia or trophozoites of E,hystolytica are seen in feces or intestinal fluid or pathogenic enteric bacteria are identified by stool culture

22. Pathophysiology of watery diarrhea

23. Pathophysiology of watery diarrhea • Normally absorption and secretion of water and electrolytes occur throughout the intestine • Water and electrolytes are simultaneously absorbed by the villi and secreted by the crypts • More than 90% of the fluid entering the small intestine is absorbed • Only 100-200cc of water excreted each day in formed stools

24. Absorption and secration  Villus • Active absorption of Na • Na absorbed with glucose and aminoacids  Crypt ; • Active secretion of choloride

25. Pathophysiology of watery diarrhea • Watery diarrhea is caused by a disturbance in the mechanism of transport of water and electrolytes in the small intestine • Intestinal transport mechanisms are also the basis for the management of diarrhea

26. Intestinal absorption water and electerolytes Absorption water from the small intestine is caused by osmotic gradients that created when Na are actively absorbed

27. Mechanisms of the watery diarrhea • There are several mechanisms for Na absorption • Na is linked to the absorption of chloride ion • Absorbed directly as Na ion • Exchanged for hydrogen ion • Or linked to the absorption of organic substances such as glucose or certain amino acids

28. Intestinal secretion of water and electrolytes • Secretion of water and electrolytes normally occurs in the crypts • Na is transported from the ECF into the epithelial cell • Na is then pumped back into the ECF by Na k ATPase • Secretory stimuli cause chloride ions to pass through the luminal membrane of the crypt cells into the bowel lumen • Osmotic gradient that causes water and electrolytes to flow passively from the ECF into the bowel

29. Mechanisms of the watery diarrhea • There are two principal mechanisms ; • Secretion • Osmotic action  intestinal infection can cause diarrhea by both mechanisms. • Secretory diarrhea is more common • Both mechanisms may occur in a single individual

30. Secretory diarrhea • There is abnormal secretion of water and electrolytes into the small bowel • Absorption Na by the villi is impaired • Secretion chloride in the crypt cell cotinuous or increased • fluid secretion and Loss water and Na as watery stools , and dehydration

31. Causes of secretory diarrhea • Toxicogenic bacteria • Vibrio cholerae • E,choli • Campilobacter • Shigella • Salmonella  Enteric viruses • ritaviruse

32. Osmotic diarrhea • Water and electrolytes move rapidly across the epithelium of small bowel mucosa to maintain osmotic balance • Diarrhea can occur when a poorly absorbed osmotically active substance is ingested

33. Osmotic diarrhea • If the substance is isotonic solution causing diarrhea but not dehydration (lactose , glucose , magnesium sulfate ) • If non absorbed substance is hypertonic solution water move from the ECF into the gut ,that causes diarrhea with dehydration and hypernatremia

35. Causes of osmotic diarrhea Product unabsorbed solution • Milk lactose ,small organic acids • Sweetened drink sucrose , glucose • Laxative salts magnesium sulfate

37. Isotonic dehydration  This is the most type of dehydration  Losses of water and Na are in the same proportion • There is a balanced deficit of water and Na • Serum Na concentration is normal (130-150 m mol / l ) • Serum osmolality is normal (275-295) • Hypovolemia occurs as a result of loss of extra cellular fluid

38. Hypernatremic dehydration  There is loss of water excess of Na  It is usually results from ; ingestion of hypertonic fluid that not efficiently absorbed Insufficient intake of water or low –solute drink • There is a deficit of water and Na deficit of water is greater • Serum Na concentration is elevated (>150 mmol/l) • Serum osmolality is elevated (>295m osmol/l ) • Thirst is severe and the child is very irritable • Sezures may occur (Na >165 mmol /l)

39. Hyponatremic dehydration There is loss of Na excess of water It is usually from ; drink large amounts of water or hypotonic fluid with low Na IV infusion 5%glucose without Na • There is deficit of water and Na but the deficit of Na is greater • Serum Na concentration is low (<130 mmol /l) • Serum osmolality is low (<275 mosmol /l) • The child is lethargic , infrequently seizures

40. Metabolic acidosis • during diarrhea a large amount of bicarbonate may be lost in the stool if the kidneys have normal function much of lost bicarbonate is replaced • when patients have hypovolemia ; Excessive production of lactic acid there is poor renal flow and fail the compensating mechanism  Serum bicarbonate concentration is reduced (<10 mmol/l)  Arterial PH is reduced (<7.10)  Breathing become deep and rapid  Vomiting is increased

41. Metabolic acidosis • Serum bicarbonate concentration is reduced (<10 mmol/l) • Arterial PH is reduced (<7.10) • Breathing become deep and rapid  Vomiting is increased

42. Metabolic effect of watery diarrhea • Loss of water and salt hypovolemia shock • Excess loss of bicarbonate acidosis • Excess loss of K K deplation

43. hypokalemia  Patients with diarrhea often develop K depletion  When K and bicarbonate are lost together hypokalemia does not usually develop • The signs of hypokalemia may include ; • General muscular weakness • Cardiac arrhythmias • Paralytic ileus

44. Oral rehydration therapy • ORT is based on the principle that intestinal absorption of Na is enhanced by the active absorption of glucose and aminoacids

45. Oral rehydration therapy • ORT is based on the principle that intestinal absorption of Na is enhanced by the active absorption of glucose and aminoacids • This process is normal during secretory diarrhea • If patients with secretory diarrhea drink an isotonic salt solution without glucose or aminoacids Na is not absorbed • When a balanced isotonic solution of glucose and salt is given glucose linked Na absorption occurs and this is accompanied by the absorption of water

46. ORS • an osmolality similar to or less than plasma • The concentration of Na should be sufficient to replace the Na deficit • The ratio of glucose to Na should be at least 1:1 • The concentration K should be 20 mmol/l • The concentration base should be 10 mmol /l for citrate or citrate or 30 mmol/l for bicarbonate • Na= 90 k=20 Cl=80 Hco3=30 Glucose =111

47. When ORT is not effective • Severe repeated vomiting • Severe diarrhea >15 cc /kg /h • Glucose malabsorption

48. ORT inappropriate for • paralytic ileus • abdominal distension • initial treatment of Severe dehydration because fluid must be replaced very rapidly • Patients who are unable to drink

49. Assessing the patient with diarrhea • Ask, look and feel for dehydration • General condition? • Well , alert? • Restless ,irritable? • floppy,lethargic, or unconscious?

50. Assessing the patient with diarrhea • Eyes:normal? Sunken? Very sunken and dry? • Tear: have tear? • Mouth and tongue: wet? dry?very dry? • Thirst: drinks normal?drinks eagerly?drinks poorly? • Skinpinch: immediately? Slowly(>2se) ? very slowly? • Additional sign: anterior fontanel?pulse? Breathing?