the bowel. This requires surgical repair and ANTIBI-
OTIC MEDICATIONSto prevent PERITONITIS. Most peo-
ple return to full and regular activities the day
after diagnostic endoscopy and within a few
weeks after endoscopic operations.
See also ANTIBIOTIC PROPHYLAXIS; ARTHROSCOPY;
BRONCHOSCOPY; CANCER PREVENTION; CYSTOSCOPY; MINI-
MALLY INVASIVE SURGERY; SURGERY BENEFIT AND RISK
ASSESSMENT.
enema The instillation of fluid into the RECTUM
through the ANUSto stimulate a BOWEL MOVEMENT.
An enema may relieve CONSTIPATIONor be part of
the preparation to cleanse the COLONfor diagnostic
procedures or surgery. Frequent enemas may
result in dependence on them for bowel move-
ments. Eating a diet high in fiber helps promote
healthy bowel motility to prevent constipation.
Doctors sometimes prescribe enemas containing
hydrocortisone (a corticosteroid medication) to
treat ulcerative COLITIS, a form of INFLAMMATORY
BOWEL DISEASE (IBD), to deliver the medication
directly to the sites of INFLAMMATION.
See also CORTICOSTEROID MEDICATIONS; LAXATIVES.
enteritis See GASTROENTERITIS.
esophageal atresia A CONGENITAL ANOMALY in
which the ESOPHAGUSfails to form properly and
does not connect to the STOMACH. The esophagus
may stop short at any location from the back of
the THROATto the top of the stomach or may
extend to the stomach but not connect. Often
there is also a tracheal–esophageal fistula (opening
between the TRACHEA and the esophagus) that
allows excessive air to enter the stomach and can
permit saliva as well as gastric secretions to enter
the LUNGS. These anomalies require emergency
intervention. The risk of ASPIRATIONis especially
serious, as fluids in the lungs can quickly lead to
INFECTIONand PNEUMONIA.
Treatment requires surgery, the nature and tim-
ing of which depend on where the esophagus
ends. The doctor may surgically insert a feeding
tube into the stomach to instill breast milk or for-
mula for feeding, as well as a nasogastric tube into
the portion of esophagus extending from the
throat to suction saliva. Because the esophagus
elongates as the child grows, doctors sometimes
delay complete surgical reconstruction for 6 to 18
months. The feeding and suction tubes remain in
place until the surgery, sometimes a series of oper-
ations over several months, is complete.
The esophagus forms very early in PREGNANCY, at
about 30 gestational days. Nearly always
esophageal atresia and any related anomalies show
up on prenatal ULTRASOUNDso both doctors and par-
ents can make treatment decisions before the
infant’s birth. Esophageal atresia tends to occur as
one of numerous congenital anomalies that may
involve the spine, HEART, other parts of the gastroin-
testinal system, the kidneys, and the extremities, a
constellation doctors refer to as VACTERL. Doctors
often use MAGNETIC RESONANCE IMAGING(MRI) or COM-
PUTED TOMOGRAPHY(CT) SCANto thoroughly examine
the infant for these anomalies.
See also ANAL ATRESIA; BIRTH DEFECTS; BOWEL ATRE-
SIA; CONGENITAL HEART DISEASE; VACTERL.esophageal cancer Malignant growths in the
ESOPHAGUS. CANCERof the esophagus takes one of
two forms: ADENOCARCINOMAor squamous cellCAR-
CINOMA. Adenocarcinoma is the more common
form and nearly always originates near the
esophageal entry to the STOMACH. Esophageal ade-
nocarcinoma is nearly always a progression of
BARRETT’S ESOPHAGUS, a condition in which the tis-
sue structure of the esophagus changes to resem-
ble that of the intestines. Adenocarcinoma can
develop only in this altered tissue. Squamous cell
carcinoma can develop anywhere along the
esophagus and is more common in people who
smoke. However, smoking, particularly in combi-
nation with excessive ALCOHOLconsumption, is a
major risk factor for either form of esophageal
cancer. People who have untreated GASTROE-
SOPHAGEAL REFLUX DISORDER(GERD) or ACHALASIAalso
face increased risk, as these conditions expose the
esophagus to repeated irritation and INFLAMMATION.
Though five-year survival rates have increased
fourfold since the 1960s, esophageal cancer
remains among the most deadly cancers because it
shows few symptoms until the cancer is quite
advanced.Symptoms and Diagnostic Path
The most common symptom is difficulty swallow-
ing (dysphagia), particularly the sensation of food40 The Gastrointestinal System