pathophysiologic mechanisms diare refkas

8/12/2019 Pathophysiologic Mechanisms DIARE REFKAS

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Pathophysiologic mechanisms: osmotic, secretory, dysmotilityassociated, and inflammatory.

** Osmotic diarrhea is caused by a failure to absorb a luminalsolute, resulting in secretion of fluids and net water retention

across an osmotic gradient. This outcome can result from eithercongenital or acquired disease and is best exemplified by the

common disorder of lactose malabsorption. Other carbohydratesmay be malabsorbed, either because of dissacharidase

deficiencies or because the absorptive capacity of the intestinefor that sugar may be overwhelmed by excessive consumption,

eg, fructose and sorbitol. issacharidase deficiencies, such as

lactase deficiency, are rarely congenital but more often are aresult of gut mucosal in!ury secondary to some process later ininfancy, such as an enteritis. Pure osmotic diarrhea should cease

when the offending dietary nutrients are removed.** "ecretory diarrhea occurs when there is a net secretion of

electrolyte and fluid from the intestine without compensatoryabsorption. #ndogenous substances, induce fluid and electrolytesecretion into the lumen even in the absence of an osmotic

gradient. $hildren with a pure secretory diarrhea will thereforecontinue to experience diarrhea even while fasting. Typically,

secretagogues affect ion transport in the large and small bowelboth by inhibiting sodium and chloride absorption and by

stimulating chloride secretion via cystic fibrosis %$&'transmembrane regulator activation. #xamples of secretory

diarrhea include multiple congenital diarrheal disordersassociated with identified genetic mutations that affect gut

epithelial ion transport. $ongenital chloride diarrhea %$$' isone such disorder

** dysmotility typically occurs in the setting of intact absorptiveabilities. (ntestinal transit time is decreased, the time allowed for

absorption is minimi)ed, and fluid is retained within the lumen.igh+amplitude propagated contractions caused motilitydisorders of the gut and have been found to be more frequent in

patients with diarrhea predominant irritable bowel syndrome

%("'. -lthough diarrhea+predominant (" may be diagnosed in



older adolescents, toddlers commonly present with chronicnonspecific diarrhea %$"'. $hanges in small intestinalmotility also have been implicated in causing $"

** (nflammatory diarrhea may encompass all of thepathophysiologic mechanisms. (nflammation with resultant

in!ury to the intestine may lead to malabsorption of dietarymacronutrients which, in turn, creates a luminal osmotic

gradient. -dditionally, particular infectious agents may inducesecretion of fluid into the lumen, and blood in the gut may alter

intestinal motility. iseases such as inflammatory bowel disease%(' and celiac disease exemplify this inflammatory

mechanism

Feeding during diarrhoea

Intestinal infection does affect the digestive and absorptive

function of the gut, and diarrhoea is a symptom of this

malfunction. The degree and extent of mucosal damage is

influenced by:

• Age – infants under 3 - months of age may be expected to

have more severe intestinal in!ury from gut infection.

• Type and site of infection " viral diarrhoea involves the

mucosal villi and can be expected to affect digestion and

absorption, #hile toxigenic diarrhoea $e.g. cholera% does not

affect the mucosal structure. Infection in the upper small gut

affects digestion and absorption more than that in the colon.

• &re-existing medical condition that affects the patient's

recovery $e.g. (I)%.• &re-existing nutritional state and lac* of breast-feeding "

malnutrition results in predisposition to mucosal atrophy, and

superimposed gut infection increases the ris* of maldigestion

$e.g. lactose intolerance%.

The state of nutrition should be assessed in each child #ith

diarrhoea.



In a #ell-nourished child, infection-induced mucosal damage

may recover rapidly #ithout a need for modified feeds.37 , 38

+nce rehydrated, the child's usual feeds should be

reintroduced. At first, it may be necessary to give smaller

volumes more freuently to avoid vomiting the diarrhoea may

continue for a short #hile. Initially, the child may be unable to

ta*e full feeds and may lose #eight, but the aim is to achieve

full-volume feeding #ithin - / days. There is no need to

dilute or other#ise modify the usual feeds, provided that they

are tolerated.

There is no need for feed change in the usual case.

0reast mil* is a hypotonic fluid that can be utilised

simultaneously for hydration maintenance and feeding breast-

feeding should continue and even be increased during

diarrhoea. +ther mil* formulas should not be used to hydrate

the patient because of the high solute load, but after recovery

from diarrhoea, extra food should be offered for nutritional

recovery.

In malnourished children, acute gastroenteritis may be moresevere, and recovery may be delayed. 1reater vigilance is

needed in suspecting possible maldigestion and malabsorption.

2hildren should be monitored until full recovery from

diarrhoea and resumption of #eight gain.

Persisting diarrhoea $longer than / #ee*s after acute onset

diarrhoea% is a more serious condition it is associated #ith

nutritional deterioration and much of the mortality from

diarrhoea. mall intestinal mucosal in!ury or bacterialovergro#th should be suspected and diagnosed by appropriate

means if: (i) the persisting diarrhoea is associated #ith #eight

loss and a continued need for rehydration fluids (ii) the child

is under months of age or is malnourished, or (iii) a

complication such as lactose intolerance exists. 4eed

modification and substitution is usually reuired.

&ersisting diarrhoea is associated #ith deterioration of

nutritional state, and must be managed actively to enable



digestive and nutritional recovery

ANTIBIOTICS are not typically recommended or acute

gastroenteritis e!cept or patients "ith a pro#en or

highly suspicious diagnosis o a parasite$%iardia or patients

"ith dysentery and the ollo"ing& less than '

months o age( systemic illness( pro#en or high suspicion o

Shigella)

The use of antibiotics would only be !ustified in:/ (mmunocompromised patients.

/ -ll cases of acute diarrhoea by Shigella, Vibrio cholerae, and

the ma!ority of those produced by enteroinvasive andenteropathogenic E. coli and by Clostridium difficile./ "ome cases of infection by Campylobacter, by Yersinia in

cases of serious disease, by Salmonella in infants withbacteraemia, and in all patients younger than 0 months.

ZINC A very recent publication has established that zinc inhibits

cAMP-induced, chloride-dependent fluid secretion byinhibiting basolateral potassium !" channels# specificity of Znto cAMP-activated ! channels, because zinc did not bloc$ thecalcium Ca"-mediated ! channels# Zinc also improves theabsorption of %ater and electrolytes, improves regeneration ofthe intestinal epithelium, increases the levels of brush borderenzymes, and enhances the immune response, allo%ing for a better clearance of the pathogens# zinc inhibits to&in-inducedcholera, but not 'scherichia coli heat-stable, enteroto&in-induced, ion secretion in cultured Caco-( cells# Zinc plays animportant role in modulating the host resistance to infectiousagents and reduces the ris$, severity, and duration of diarrhealdiseases# It also plays a critical role in metallo-enzymes,polyribosomes, and the cell membrane and cellular function,giving credence to the belief that it plays a central role incellular gro%th and in the function of the immune system



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CONT+A,IN-ICATIONS TO O+A. +/01-+ATION

AN- A-2ISSION C+IT/+IA

O#er 4 dehydrated 5determined 6y "eight or estimation

Signs o shoc

Ileus or intestinal o6struction 5pro#en or suspected

Comatose or unconscious

9na6le to tolerate O+T$N%T rehydration 5persistent

#omiting 9nclear diagnosis

Signiicant psychosocial situation

A stool specimen should be examined for #hite blood cells in

any child #ho appears toxic #ith high fever and diarrhea. The

finding of #hite blood cells should prompt further investigationto rule out invasive bacterial disease. The presence of gross

blood in the diarrheal stool also suggests a more serious

infection, so children #ith bloody diarrhea should undergo a

rectal s#ab or stool culture

I a patient has "orsening diarrhea "ith the

resumption o lactose,containing products( consider

checing stool or p0 and reducing su6stances) 1rossly

0loody tools, high fever, foreign travel, or specific pathogencommunity outbrea*

STOO. ST9-I/S may 6e considered 6ased on the clinical

situation: C) di to!in( culture( ;BC( O<P( %iardia

antigen may 6e considered 6ut are not recommended i a

#irus is the most o6#ious source) +ota#irus antigen

testing is rarely re=uired( e!cept or epidemiology studies

and cohorting purposes

The most common symptoms of a pathogenic bacterial infection

are prolonged diarrhea, bloody diarrhea, mucus in the stool,

abdominal pain and cramping, and nausea. If diarrhea lasts more

than a fe# days, it may lead to complications such

as dehydration and electrolyte imbalance - dangerous

conditions, especially in children and the elderly. 5ehydration

can cause symptoms such as dry s*in, fatigue, and light-

http://labtestsonline.org/glossary/dehydration

http://labtestsonline.org/glossary/dehydration



headedness.

everely affected people may reuire hospitali6ation to replace

lost fluids and electrolytes. (emolytic uremic syndrome is a

serious complication characteri6ed by the destruction of red blood cells and *idney failure that may occasionally arise from

an infection #ith a toxin-producing strain of the

bacteria Escherichia coli. The condition is most freuently seen

in children, the elderly, and those #ith #ea*ened immune

systems.

stool culture is done to identify bacteria or viruses that may be

causing an infection. Tell your doctor if you have recently ta*enantibiotics, traveled out of the country, or had a recent test #ith

contrast material.

4ind the cause of symptoms, such as severe or bloody

diarrhea, an increased amount of gas, nausea, vomiting,

loss of appetite, bloating, abdominal pain and cramping,

and fever.

4ind and identify certain types of bacteria, viruses, fungi, or

parasites that are causing infections or diseases, such asfood poisoning, inflammation of the large intestine

$colitis%, cholera, and typhoid.

Identify a person #ho may not have any symptoms of disease

but #ho carries bacteria that can spread infection to others.

This person is called a carrier. A person #ho is a carrier

and #ho handles food is li*ely to infect others.

4ind out if treatment for an infection has been effective.

2hildren infected #ith highly contagious organisms capable of

causing serious illness such as E. coli 0157:H7 , Shigella, or

Salmonella typhi. 2hildren #ith E. coli 0157:H7 or Shigella

shall be excluded from child care until t#o stool cultures are

negative. 2hildren #ith Salmonella typhi shall be excluded from

child care until three stool cultures are negative. (istory

suggestive of food poisoning, recent travel abroad or blood in

http://labtestsonline.org/understanding/analytes/e-coli/tab/sample

http://www.webmd.com/hw-popup/antibiotics

http://www.webmd.com/hw-popup/contrast-material

http://www.webmd.com/hw-popup/food-poisoning

http://www.webmd.com/ibd-crohns-disease/colitis-guide/ulcerative-colitis-overview-facts

http://www.webmd.com/hw-popup/cholera

http://www.webmd.com/hw-popup/typhoid-fever

http://labtestsonline.org/understanding/analytes/e-coli/tab/sample

http://www.webmd.com/hw-popup/antibiotics

http://www.webmd.com/hw-popup/contrast-material

http://www.webmd.com/hw-popup/food-poisoning

http://www.webmd.com/ibd-crohns-disease/colitis-guide/ulcerative-colitis-overview-facts

http://www.webmd.com/hw-popup/cholera

http://www.webmd.com/hw-popup/typhoid-fever



the stool, #ith or #ithout mucus. A stool should also be sent if

the child is systemically un#ell, or has severe or prolonged

diarrhoea

2eta6olic pro6lems and electrolyte distur6ances

These occur because of the loss of sodium, bicarbonate and

potassium associated #ith #atery stools. The electrolyte

status o patients #ith severe diarrhoeal dehydration,

circulatory disturbances or metabolic acidosis should be

ascertained.

> 2eta6olic acidosis is almost al#ays present if the patient hassignificant dehydration, and is identified by more rapid deep

respirations #ith a clear chest on auscultation. 7nless

metabolic acidosis is severe, sodium bicarbonate is usually not

reuired, as rehydration allo#s for correction. 8ehydration

fluid contains al*ali in the form of citrate or bicarbonate. A

#ide anion gap may suggest the possibility of severe *etosis,

salicylate intoxication or lactic acidosis.

• 9arge amounts of potassium are lost in diarrhoeal stools.etabolic acidosis is associated #ith further urinary potassium

loss. In acidosis, a shift of intracellular potassium to the

extracellular compartment results in a spurious elevation of the

serum level, despite intracellular potassium loss. All children

suffering from severe diarrhoea should receive oral potassium

chloride: /; mg <-hourly if under year of age, and /;= mg

<-hourly if over year of age, until dehydration and acidosis

are corrected.> Sodium disturbances occur freuently. odium content of the

stool #ater varies from plasma-li*e in secretory diarrhoea

$such as cholera%, to very lo# in pure osmotic diarrhoea. In

general, serum sodium is inversely related to the state of the

intracellular #ater compartment, i.e. raised serum sodium

reflects intracellular dehydration. (ypo- and hypernatraemia

management should follo# recommended guidelines ho#ever,

#here +8T is possible, the process of rehydration usuallyallo#s metabolic homeostasis to be re-established.



> Blood glucose disturbances occur in severely ill young

children as a result of glycogen depletion #ith lac* of inta*e,

or in association #ith the stress response of dehydration. 0lood

glucose estimation should be performed by finger-pric* test in

all dehydrated children.

5ehydrated or malnourished children are li*ely to have a

metabolic disturbance.

erum electrolytes are sometimes useful in assessing children

#ith moderate to severe dehydration and #ho reuire

intravenous $I)% or nasogastric $>1% fluids

??? &8+0I+TI2

Microflora of the large intestine normally ferment residual

carbohydrate and produce short chain fatty acids (SCFAs). This

reduces the luminal pH and discourages intestinal pathogens.

The SCFAs also enhance colonic water absorption. In acute

diarrhoea, as intestinal microflora is altered, production ofSCFAs is reduced and there is increased water loss. The use of

probiotics early in the course of diarrhea from acute viral

gastroenteritis may reduce its duration by one day in other#ise

healthy infants and young children

(o#ever, the evidence does not support the routine use of

probiotics to prevent infectious diarrhea. )a*sin pentavalen

rotavirus more effective than the use of probiotics in preventing

the most common form of acute infectious diarrhea in infants.shortening in the duration of the diarrhoea. - moderate clinical

benefit of some probiotics has been shown in the treatment ofacute watery diarrhoea, mainly by rotavirus in infants and youngchildren77. This effect seems to be: moderate in reducing

diarrhoea by 7=>06 hours? strain dependent with LactobacillusGG most effective?

@I>2 A>5 +8



It recommends zinc salt along %ith lo% osmolarity )*+, %ithreduced levels of glucose and salt, during acute diarrhea, %hich reduces the duration and severity of the episode andzinc supplementation given for .-/ days lo%ers the

incidence of diarrhea#

Pharmacokinetics of Zinc in Diarrhea[12]

Absorption

0he molecular %eight of elemental zinc is 12#34 and zinc

sulfate is (54#2# Crude zinc sulfate is also $no%n as %hite

6itriol# 'ach gram of zinc sulfate represents 3#2 millimoles of

Zn# Its solubility is in .#1 ml of %ater and it is insoluble inalcohol# Zinc and its salts are poorly absorbed from the

gastrointestinal tract 7I0" only (. to 3.8", duodenum, and

ileum# 'ndogenous zinc is reabsorbed in the ileum and colon,

creating enterohepatic circulation#

Distribution

After absorption zinc is bound to protein metallothionein inthe intestines# Zinc is %idely distributed throughout the body#

It is primarily stored in *9Cs, :9Cs, muscles, bones, +$in,

!idneys, ;iver, Pancreas, retina, and prostate# 0he e&tent of

binding is 1. - 4.8 to plasma albumin, 3. - /.8 to alpha (

macroglobulins or transferring, and 8 to amino acids li$e

histidine and cysteine# Pea$ plasma concentration occurs in

appro&imately t%o hours#Elimination

Zinc is e&creted mainly in the feces <.8" and only traces are

found in the urine, as the $idney plays a small role in

regulating the body Zn content#

Convincing evidence for the clinical importance of zinc hascome from the randomized controlled trials *C0s" evaluatingthe impact of zinc supplementation during acute and

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3113371/#ref12

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3113371/#ref12



persistent diarrhea#

== - >aily supplementation of zinc had an effect on the clinicalcourse of acute diarrhea, that is, fre?uency of stool, stool

amount, and duration of acute diarrhea- >uring acute shigellosis sho%ed that zinc therapy %asassociated %ith enhanced antigen-specific antibody responses#0he bactericidal antibody titers against +higella increased theproportions of 9 cells and plasma cells, as also higherlymphocyte proliferation responses in the peripheralcirculation, during the early convalescent phase of shigellosis#@or all these reasons, it is clear that zinc supplementationshould be given as an adunct to antimicrobial AM" treatmentin bloody diarrhea

pathophysiologic mechanisms diare refkas

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