F

familial adenomatous polyposis (FAP) A genetic
disorder in which hundreds of intestinal polyps
grow in the RECTUMand COLON. FAP is an extreme
risk for early-onset COLORECTAL CANCER. This auto-
somal dominant disorder results from a defective
gene, inherited from one parent, in which there is
a MUTATION of the adenomatous polyposis coli
(APC) GENE. The ACP gene regulates the proteins
that inhibit adenomas (abnormal growths arising
from epithelial cells, the cells that form the surface
layer of SKINand membranes) in the intestinal
mucosa. The mutation of the ACP gene blocks
these proteins, allowing adenomas, called intes-
tinal polyps when they occur in the colon, to
flourish. In FAP polyps are generally abundant by
late ADOLESCENCE, with COLORECTAL CANCERdevelop-
ing before age 40.
The rapid and prolific growth of FAP-associated
intestinal polyps significantly favors their evolu-
tion to malignancies, manifesting primarily as colo-
rectal adenocarcinomas though may also occur in
other sections of the gastrointestinal tract, notably
the DUODENUM. FAP polyps and malignancies sel-
dom show early symptoms; family history is the
most important diagnostic factor. Signs of FAP
include specific dental anomalies and retinal
changes that are apparent in childhood. CANCER
experts recommend screening COLONOSCOPYannu-
ally beginning in early adolescence, and every
three to six months when polyp growth becomes
pronounced.
Colonoscopy allows the gastroenterologist to
remove large intestinal polyps and polyps showing
DYSPLASIA (cellular changes indicating that ADE-
NOMA-TO-ADENOCARCINOMA TRANSITION is under
way). Studies suggest some NONSTEROIDAL ANTI-
INFLAMMATORY DRUGS(NSAIDS) may slow the growth
of adenomas, reducing the number and size of the

polyps. However, these medications do not alter

the course of the disease, and surgery to remove

the most heavily involved sections of intestine

ultimately becomes the therapeutic solution.

Doctors often recommend prophylactic total

bowel resection (removal of the colon and rectum)

to eliminate the potential for colorectal cancer.

Presently this is the only means to prevent FAP

from developing into colorectal cancer. Advances

in GENE THERAPYshow the greatest potential for less

invasive and more effective treatments in the

future. Participation in clinical research studies that

are evaluating investigational treatments may pre-

sent other treatment opportunities.

See also ADENOMA; CANCER PREVENTION; CANCER

RISK FACTORS; CELL STRUCTURE AND FUNCTION; GENETIC

DISORDERS; HEREDITARY NONPOLYPOSIS COLORECTAL CAN-

CER(HNPCC); ILEOANAL RESERVOIR; ILEOSTOMY; INHERI-

TANCE PATTERNS.

fatty liver See STEATOHEPATITIS.

fecal impaction Hardened pieces of feces, also

called stool, that lodge in the COLONor RECTUM.

Fecal impaction typically occurs as a consequence

of chronic CONSTIPATIONor reduced bowel motility

(movement of digestive waste through the colon)

and is most common in people who are confined

to bed for extended periods of time. Those who

take narcotic PAIN medications or ANTIDIARRHEAL

MEDICATIONS may also develop fecal impaction.

Symptoms may include extended time without a

BOWEL MOVEMENT, lower abdominal cramping or

pain, and DIARRHEAfrom stool leaking around the

impaction. DIGITAL RECTAL EXAMINATION(DRE) allows

the doctor to make the diagnosis. Treatment may

include manual removal of the impaction or

ENEMA to soften the impaction and stimulate

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