Encyclopedia of Health and Medicine

C–D
cystinuria An inherited genetic disorder in
which the KIDNEYS do not properly reabsorb amino
acids collectively called cystine. The excessive
excretion of cystine to the URINE causes crystalline
calcifications, commonly called stones, to form in
the kidneys, ureters, and BLADDER. Most people
learn they have the GENE MUTATION, which is autosomal
recessive, during analysis of the calcifications.
Doctors have known of cystine calcifications
in the bladder since the early 1800s. Researchers
identified cystinuria as hereditary in the early
1900s and discovered the first effective medication
to reduce the formation of cystine calcifications,
penicillamine, in the early 1960s. In the late 1990s
researchers identified the mutated genes as
SLC3A1 on CHROMOSOME 2 and SLC7A9 on chromosome
19.
Pain in the side or back, often on only one side,
is the typical symptom of an occlusive (blocking)
calcification. The urine may also smell of sulfur
(rotten eggs) The diagnostic path may include
ULTRASOUND, COMPUTED TOMOGRAPHY (CT) SCAN, or
MAGNETIC RESONANCE IMAGING (MRI) of the abdomen
to visualize the calcifications. Laboratory analysis
of fragments filtered from the urine identifies their
composition as cystine, confirming the diagnosis.
Most of the time the stones pass on their own,
though the process often is painful. Doctors usually
prescribe ANALGESIC MEDICATIONS for PAIN relief
during the time a stone is passing. Occasionally
treatments such as EXTRACORPOREAL SHOCK WAVE
LITHOTRIPSY (ESWL), which uses high-frequency
sound waves to break the calcification into fragments,
or surgery (percutaneous nephrolithotomy)
are necessary to remove an obstructive and
impacted stone.
Because there are as yet no treatments to correct
the gene mutation, the cystine calcifications
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recur throughout life. Penicillamine, which binds
with cystine in the urine to form a compound that
easily dissolves in water, remains the medication
urologists most often prescribe to reduce the formation
of stones. The urologist may also prescribe
medications to increase the alkalinity of the urine,
such as potassium citrate, which helps dissolve
cystine. It is important for people who have
cystinuria to drink enough water to maintain good
urine output, which dilutes the concentration of
cystine and pass it from the body before it forms
calcifications. Other lifestyle modifications include
decreasing dietary sodium and protein consumption
(protein is the source of the cystine).
See also ENDOSCOPY; FANCONI’S SYNDROME; GENE
THERAPY; HYPEROXALURIA; INHERITANCE PATTERNS;
NEPHROLITHIASIS; SURGERY BENEFIT AND RISK ASSESS-
MENT; UROLITHIASIS.
cystitis INFLAMMATION of the BLADDER. The most
common cause of cystitis is bacterial INFECTION,
called URINARY TRACT INFECTION (UTI). Other
pathogens, such as fungi (yeasts) and viruses, also
can cause infectious cystitis. Nonpathogenic causes
of cystitis include irritation of the lining of the bladder,
which may occur with excessive consumption
of irritating substances such as CAFFEINE, high-acid
foods, or certain medications. Cigarette smoking is
a significant bladder irritant. RADIATION THERAPY,
CHEMOTHERAPY, and AUTOIMMUNE DISORDERS also may
cause cystitis. Interstitial cystitis is a chronic condition
the hallmark of which is inflammation of the
bladder along with a constellation of symptoms for
which there are no clearly identifiable causes.
Symptoms and Diagnostic Path
The symptoms of cystitis may include
• DYSURIA (burning or PAIN with URINATION)