Definition of Chronic Diarrhea depends on weight. If they are infants/tollders than it defined as 10g/kg/day and if they are children it is greater than 200g/day for more than 14 days. The other ways to describe is if they have loose,watery stools for than 3 times per day.
FUNCTIONAL DIARRHEA
This is not necessary pathological, it is due to the child taking in too much carbonated drinks such as juices and sodas. The key is that the diarrhea occurs in the day and worsens as the day drags on. It will painless, no blood, no Failure to Thrive and they will otherwise be healthy without dehydration.
OSMOTIC DIARRHEA and SECRETORY DIARRHEA is a very common classification system that is used. Osmotic Diarrhea is when a non-absorbable substance in the gut becomes osmotically active and draws out water from the enterocytes into the gut. ALso it goes into the colon intact and then bacteria produce organic acid and ferments the food and therefore the pH will be much lower and watery.
In Secretory Diarrhea there is a toxin which activates cAMP and cGMP which activates channels which cause fluid to rush out of the enterocyte into the gut. In cAMP there is Cholera Toxin, Labile Toxin, Shigella and Shiga-like toxin. cGMP is caused by Stabile Toxin (ST). There are certain laboratory and clinical features do seperate them and we can discuss them one by one. Secretory tends to be much more perfuse. Fasting response is another differentiated feature to distinguish chronic diarrhea. When the patient begins fasting, the diarrhea stops. However, in secretory diarrhea the diarrhea continues with fasting. Another feature is reducing substances in the stool. This tests the presence of carbohydrates which will be present with osmotic diarrhea. Also in osmotic diarrhea the pH will less than 5. The osmotic gap is determined by adding Na and K and multiplying by 2 and subtracting from serum osmolality. If gap is greater than 125 and if less than 50 than you are looking at secretory.
Inhertied trasport protein can lead to similar conduciton, however, it will be much more chronic. The two most common is Na/H exchange and Cl/HCO3 exchange.
INFECTIOUS CAUSES
Generally infections clear up before two weeks. Post-Enteritis syndrome cause damage to the gut wall which leads to diarrhea as the gut wall damage clears up. Parasites such as Giardia Lamblia damages the gut wall, Entamoeba Histolytica which will cause bloody diarrhea.
IMMUNODEFICIENCY
HIV, IgA Deficiency, Chronic Variable Immunodeviciency can also cause chronic diarrhea
AUTOIMMUNE
Celiac's disease, Ulcerative Colitis, Crohns Disease, Allergic Enteropathy associated with cowmilk protein. Eosinophilic enteropathy which is an allergy to a substance. Finally there is autoimmune enteropathy associated with Diabetes Mellitus and IPEX syndrome.
STEATORRHEA
This is when there is ifnding fo fat in stool. Steatorrhea is caused by defieincy in pancreas and deficiency of bil acid. Cystic Fibrosis, Familial Chronic Pancreatitis with trypsin enzyme. Schwackmann Diamonds Syndrome, Pearson, Johanson Blizzard are all associated with. Bile Acid are important for absorbing fat. Chornic cholestasis, Terminal Ileal resection which is reabsorbing bile. Bacterial overgrowth causing conjugation of bile. Bile acid Sequestratnt such as cholestyramine. There is a parimry malabsorption where bile transporter is missing.
MOTILITY
Depressed motility in Diabetes Mellitus, Malnutrition, Scleroderma, Hirschsprung.
TUMORS
Gastrinoma may cause chronic diarrhea. VIPoma may also lead to chronic diarrhea in children with the associated tumor.
DECREASED SURFACE AREA.
Classically caused by post-surgical removed of gut and flattening of the brush border.
EVALUATION
Must take an accurate history such as quantity, color, timings, frequently, time of day. Nutrition and also water intake is important to ask about to make sure it is maintained well.
EXAMINATION
Pay attention to the growth of the patient. The dehydration status. stool exam grossly if there is liquid, blood or mucus is seen. Microscopic examination may find WBC and other inflammatory markers. Ova Parasites may also be present. Occult Blood and pH, electrolytes are also important to find osmotic gap.
Secondly you may want to do Cl test, laxatives. Hydrogen Breathe test to test for CH malabsorption. anti-TTG Celiac Disease test. Endoscopy, biopsy and barium. Finally you want to look for tumors such as VIP and Gastrin