Jamil Altwaije r lina abdullah References WALKERS PEDIATRIC GASTROINTESTINAL DISEASE PATHOPHYSIOLOGY DIAGNOSIS MANAGEMENT SIXTH EDITION Nelsons textbook 20 ID: 919429
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Slide1
Malabsorption
Aseel
Jamil
Al-twaije
r
lina
abdullah
Slide2References
WALKER’S PEDIATRIC GASTROINTESTINAL DISEASE PATHOPHYSIOLOGY • DIAGNOSIS •
MANAGEMENT
SIXTH EDITION
Nelson:s
textbook 20
th
edition
Slide3For Normal Digestion & Absorption; the followings are needed:1-Intact Mucosa 2-Normal Motility [coordinated
peristalisis
]
3- Intact secretions 4- Pancreatic secretionsIf any Defect it will lead to
Malabsorption
Slide4What steps are involved in digestion and absorption?Three phases are involved:
Luminal phase - Dietary fats, proteins and carbohydrates are hydrolyzed and solubilized, largely by pancreatic and biliary secretions.
Mucosal phase - Terminal hydrolysis of carbohydrate and peptides occurs and fats are processed and ;then packaged for cellular export.
Removal phase - Absorbed nutrients enter the vascular or lymphatic circulation.
Thus defect in any of these phases leads to
malabsorption
.
Slide5Lipid DigestionThe most common dietary lipids are triglycerides, which are made up of a glycerol molecule bound to three fatty acid chains. Small amounts of dietary cholesterol and phospholipids are also consumed.
The three lipases responsible for lipid digestion are lingual lipase, gastric lipase, and
pancreatic lipase
. However, because the pancreas is the only consequential source of lipase, virtually all lipid digestion occurs in the small intestine. Pancreatic lipase breaks down each triglyceride into two free fatty acids and a
monoglyceride
. The fatty acids include both short-chain (less than 10 to 12 carbons) and long-chain fatty acids
Slide6Slide7The digestion of protein starts in the stomach, where
HCl
and pepsin break proteins into smaller polypeptides, which then travel to the small intestine. Chemical digestion in the small intestine is continued by pancreatic enzymes, including chymotrypsin and trypsin, each of which act on specific bonds in amino acid sequences. At the same time, the cells of the brush border secrete enzymes such as
aminopeptidase
and
dipeptidase
, which further break down peptide chains. This results in molecules small enough to enter the bloodstream
Slide8Slide9Slide10Slide11Slide12Slide13Slide14Chronic Diarrhea
Persistent or chronic diarrhea refers to a pattern of loose stools (with orwithout an increase in stool frequency) that lasts for at least two weeks.
This definition, supported by the World Health Organization (WHO)
"
Slide15APPROACH TO THE CHILD WITH PERSISTENT
DIARRHEA
The starting point in the approach to the child with persistent diarrhea is
the evaluation of weight curve, age at onset, pattern of stools and
association with other signs or symptoms.69
A careful history and physical examination are needed for optimal
diagnostic approach.
A family history of atopic or autoimmune diseases points toward
allergy or autoimmunity. The same is often true for children with cystic
fibrosis or IBD. However, CDDs are very frequently inherited as
autosomic
recessive manner and some specific diseases are more frequent
in ethnic groups where consanguineous marriages are common, or in some
geographic areas due to founder effects.62,68 A familiar history of early
onset chronic diarrhea,
polyhydramnios
, and/or dilated bowel loops at
ultrasound examination during pregnancy is highly suggestive of CDDs
and diarrhea often dates to early neonatal period.
Slide16Does an Acute Gastrointestinal Infection Lead to Malabsorption?
Slide17Classifying the type of diarrhea may be done with either a trial of fasting or by analysis of stool electrolytes while on a complete diet.
In fact, the majority of patients with
abnormal intestinal histology have a mixed form of diarrhea that has both
osmotic and secretory components.
Slide18Slide19Slide20Slide21Slide22Disorders of Carbohydrate absorption
Slide23Slide24Carbohydrate intolerance of all forms is characterized by diarrhea thatsubsides shortly after carbohydrates are reduced or eliminated from the
diet. Therefore, abnormal carbohydrate assimilation results in the presence
of major osmotic forces in colonic luminal fluid derived from oligosaccharides, lactose, sucrose
or glucose.
Unabsorbed carbohydrates are fermented by the resident colonic
microflora
to gas (hydrogen,
methane, and carbon dioxide) and volatile short-chain fatty acids such as acetate, butyrate, and propionate. A proportion of these SCFAs are absorbed across the colonic epithelium by poorly defined diffusion and transporter-mediated mechanisms.
Slide25Slide26Glucose–galactose
malabsorption
(GGM) is a rare autosomal recessiveDisorder that causes severe life- threatening diarrhea and dehydration during the neonatal period
Diarrhea is most frequently detected during the first several weeks of life in breastfed
or bottle-fed children, and will result in severe metabolic acidosis and
hyperosmolar dehydration. Diarrhea ceases at bowel rest and resumes
when the child receives the same feeding again, protein
hydrolysate
or
elemental diet (amino acid–based formula). If not properly diagnosed in a
timely manner and if dietary management is not implemented, GGM is frequently fatal.
several formulas are available for managing GGM patients
during early infancy, including Ross Carbohydrate Free Formula
Slide27Lactase deficiency
Slide28Slide29Slide30Fructose malabsorption
Fructose is the primary monosaccharide found in fruits and fruit juices.
Fruit juices that contain a high proportion of fructose to glucose or an
excessive amount of the
nonabsorbable
carbohydrate sorbitol have been
associated with infant diarrhea and abdominal pain
Fructose
malabsorption
can be assessed by either placing the patient on a
fructose elimination diet or performing a fructose breath hydrogen test.
Fructose given at 1 g/kg body weight or a maximum of 25 g can be used to
perform these studies1
Slide31Patients experiencing significant fructose-induced diarrhea should either
reduce or eliminate their dietary fructose load to resolve symptoms.
Because fructose
malabsorption
is generally limited to early infancy, attempts to reintroduce fructose should be considered as patients enter into the school-aged years
Slide32DISORDERS OF AMINO ACID AND PEPTIDEASSIMILATION
Hartnup’s
Disease
Hartnup’s
disease and
iminoglycinuria
)
are two other autosomal recessive disorders that have been well
characterized clinically.
Hartnup’s
disease is characterized by a
malabsorption
and renal excretion of neutral amino acids (neutral
aminoaciduria) and a heterogeneous set of symptoms ranging from a
pellagra-like rash to neurologic disorders
Slide33Slide34Slide35Slide36Slide37Slide38DISORDERS OF FAT ASSIMILATION
The clinical consequences of disorders of fat assimilation include
failure to thrive,
steatorrhea, and neurologic deficits that result from the
malabsorption
of fat-soluble vitamins
Because pancreatic exocrine function in particular is not fully formed during early infancy, fat absorption in this age group primarily depends on the action of gastric lipase.
A congenital deficiency of pancreatic lipase is an exceedingly rare autosomal recessive disorder that leads to fat
malabsorption
Slide39Slide40Fatty acid and
diglyceride
are the products of triglyceride hydrolysis,
and their solubilization to the aqueous phase of luminal content requires
adequate levels of conjugated bile salts, and therefore various disorders of
intrahepatic and
extrahepatic
cholestasis will impede the delivery of
luminal bile salts and result in fat
malabsorption
.
Slide41Abetalipoproteinemia
Abetalipoproteinemia
(ABL) (MIM #200100) is the classic and most
wellcharacterized
disorder of fat absorption and results from failure to
reassemble dietary fat in the form of β-lipoproteins.
Patients generally present shortly after birth with failure to thrive and
steatorrhea
and if untreated will develop irreversible neurologic problems in late infancy.
Slide42Clinical ManifestationsThe typical clinical presentation is often failure to thrive, emesis, and low volume
diarrhea. Poor growth despite adequate caloric intake is an early
clinical characteristic that should hasten the assessment of a possible
defect of fat
malabsorption
. In the long term, patients may develop an
aversion to fatty meals as a way to diminish their diarrheal symptoms. The
first evidence of neuromuscular abnormalities is frequently the loss of
deep tendon reflexes, which results from prolonged vitamin E deficiency;
additional neuromuscular manifestations, including retinitis
pigmentosa
,
ataxia, and
spinocerebellar
degeneration, may be mistaken for various
forms of
Friedreich
ataxia.
Slide43Serum samples should be analyzed for evidence of β-lipoprotein (VLDL
and chylomicron) deficiencies.
Slide44Cystic fibrosisCystic fibrosis results in impairment of pancreatic
exocrine function and generalized
malabsorptive
symptoms, as pancreaticenzymes hydrolyze dietary fats and complex carbohydrates.119 However,
disorders of pancreatic insufficiency are not associated with
malabsorption
of either
monosaccharides
(glucose,
galactose
, or fructose) or amino acids.
Slide45Slide46Slide47Slide48Slide49Slide50DISORDERS OF MINERAL AND ELECTROLYTE ABSORPTION AND SECRETIONCongenital Chloride Diarrhea
The most common cause of severe congenital secretory diarrhea in the
presence of normal intestinal mucosa is the autosomal recessive disorder
congenital chloride diarrhea
Clinical Manifestations
The earliest clinical symptoms may occur in utero with severe
polyhydramnios
and dilated loops of small bowel detectible by ultrasonography that may resemble a distal intestinal obstruction.150 The
severity of the
polyhydramnios
frequently leads to preterm labor or planned premature delivery by cesarean section. Patients with CCD generally present during the first weeks of life with severe life-threatening secretory diarrhea. The serum electrolytes prior to treatment are unique
among the various congenital diarrheal disorders and include metabolic alkalosis,
hypochloremia
, hypokalemia, and
hyponatremia
.
Slide51A diagnosis of CCD is suggested if fecal chloride concentration is high
(>90
mmol
/L) and exceeds the concentration of cations
(Na+ and K+)
The mainstay of therapy is life-long enteral administration of
KCl
and
NaCl
supplements, in the range of 2.8
mmol
/kg/d for infants, However, occasional assessment of serum and
urine electrolyte and pH balance is recommended to optimize the
Cl
– replacement doses.
Slide52