Encyclopedia of Health and Medicine

M–N
malabsorption
Inadequate absorption of NUTRI-
ENTS into the BLOOD circulation from the SMALL
INTESTINE during digestion, also called malabsorption
syndrome. Malabsorption may result from
damage to the small intestine that restricts the
surface area of the intestinal mucosa (lining) or
may develop as a consequence of digestive
enzyme deficiencies. CELIAC DISEASE, LACTOSE INTOL-
ERANCE, CYSTIC FIBROSIS, GASTROENTERITIS, and
INFLAMMATORY BOWEL DISEASE (IBD) are among the
more common causes of malabsorption. Conditions
affecting the PANCREAS, LIVER, and GALLBLAD-
DER can result in secondary malabsorption.
Untreated malabsorption characteristically causes
NUTRITIONAL DEFICIENCIES and MALNUTRITION.
The diagnostic path may include stool analysis,
blood tests, and URINALYSIS. The gastroenterologist
may perform an ENDOSCOPY with biopsy when preliminary
test findings are inconclusive. Treatment,
which often includes a combination of dietary and
medical management methods, targets any underlying
condition. Secondary malabsorption generally
goes away when the underlying condition
improves. Severe malabsorption with malnutrition
requires PARENTERAL NUTRITION (intravenous solutions)
to replenish the body’s nutrients. Malabsorption
related to enzyme deficiencies often
resolves with dietary changes alone.
See also BORBORYGMUS; DIET AND HEALTH; DIGESTIVE
ENZYMES; NUTRITIONAL NEEDS; PANCREATITIS; SHORT
BOWEL SYNDROME; SMALL BOWEL TRANSPLANTATION;
STEATORRHEA; WHIPPLE’S DISEASE.
meconium The first stool a newborn passes,
made up of AMNIOTIC FLUID, BILE, and mucus. Meconium
resembles tar in consistency and color. Its
passing is a key indictor of the infant’s health and
gastrointestinal patency (clear passage). Infants
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with healthy gastrointestinal systems pass their
first meconium stools within 24 hours of birth and
may continue to pass meconium for two or three
days. An infant that fails to pass meconium within
24 hours may have a congenital malformation of
the gastrointestinal tract such as BOWEL ATRESIA. A
complication common in infants who have CYSTIC
FIBROSIS, a genetic disorder that affects multiple
body systems, is meconium ILEUS in which
impacted meconium obstructs the bowel. Enemas
often relieve the impaction; when they do not,
surgery is necessary.
See also CHILDBIRTH; CONGENITAL ANOMALY; ENEMA.
nasogastric aspiration and lavage The clinical
term for the procedure commonly called “pumping
the STOMACH.” In nasogastric aspiration and
lavage, the health-care provider inserts a narrow
tube (catheter) through the NOSE, down the back
of the THROAT and the ESOPHAGUS, and into the
stomach. The stomach’s contents are then sucked
through the tube. The health-care provider may
also use the tube to instill a rinsing solution, often
a mixture of liquid and activated charcoal, into the
stomach to absorb and neutralize remaining gastric
content. Nasogastric aspiration and lavage is
most commonly an emergency treatment for
ingested toxins, including DRUG OVERDOSE, though
also can help diagnose gastric bleeding.
See also GASTROINTESTINAL BLEEDING; INGESTED
TOXINS.
nausea A sensation of queasiness and the feeling
of being about to vomit. Though nausea feels as
though it arises from the gastrointestinal tract, the
signals that initiate its sensations originate in two
areas of the BRAIN, the chemoreceptor trigger zone
and the emetic (VOMITING) center. These areas are