Encyclopedia of Health and Medicine

196 The Urinary System
dures for other health concerns. Doctors diagnose
most others in the course of identifying the causes
for conditions that affect the kidneys. When
symptoms do occur, they generally represent a
consequential condition such as nephrolithiasis.
The diagnostic path includes blood and urine tests
to assess kidney function. Diagnostic imaging procedures
such as COMPUTED TOMOGRAPHY (CT) SCAN or
renal ULTRASOUND can provide visual evidence of
the fused kidneys. Diagnostic prenatal ultrasound
often detects horseshoe kidney in the unborn
child.
For the most part horseshoe kidney of itself
presents no unusual health risks. The fused kidneys
are prone to the same conditions that affect
kidneys in general. Treatment targets any conditions
affecting the kidney. The urologist or
nephrologist may suggest surgery (nephroplasty)
to separate the kidneys and establish normal positioning
of the ureters and the blood supply.
Watchful waiting, with routine medical care to
monitor kidney function and health, is appropriate
for many people who have no symptoms of
kidney disease. Researchers do not know what
causes horseshoe kidney to occur. One child born
with horseshoe kidney does not increase the likelihood
that other children will also have the
anomaly; the condition appears to be entirely random.
See also EPISPADIAS; HYPOSPADIAS; TURNER’S SYN-
DROME.
hydronephrosis A circumstance in which the
renal pelvis, the portion of the kidney that collects
URINE for passage from the kidney via the URETER,
dilates and enlarges. Hydronephrosis results from
conditions of the kidney that slow or block the flow
of urine, causing urine to back up into or pool in
the renal pelvis. Such conditions may include
obstructive NEPHROLITHIASIS (kidney stones that
block the ureter), NEUROGENIC BLADDER (in which the
BLADDER fails to respond to the normal neurosensory
signals that regulate URINATION and becomes
overly full), and VESICOURETERAL REFLUX (urine
washes back into the ureters from the bladder).
Unilateral hydronephrosis, which affects only
one kidney, is the more common presentation.
Bilateral hydronephrosis, which affects both KID-
NEYS, often indicates CONGENITAL ANOMALY of kidney
or ureteral structure though may develop as a
consequence of conditions such as HYPERTENSION
(high BLOOD PRESSURE), DIABETES and BENIGN PROSTA-
TIC HYPERPLASIA (BPH) that constricts the urethra
and slows the flow of urine during urination.
The symptoms of hydronephrosis may include
• abdominal or back PAIN
• DYSURIA (discomfort or burning with urination)
• URINARY FREQUENCY
• URINARY URGENCY
• signs of INFECTION such as FEVER and cloudy or
bloody urine
Some people may have no symptoms, with the
hydronephrosis showing up during evaluation of
other medical concerns or in PREGNANCY. The diagnostic
path begins with urinalysis and blood tests
to evaluate kidney function and usually includes
an abdominal X-RAY, ULTRASOUND, COMPUTED TOMOG-
RAPHY (CT) SCAN, INTRAVENOUS PYELOGRAM (IVP), or
MAGNETIC RESONANCE IMAGING (MRI) examination to
visualize the kidneys. Treatment targets the
underlying disease process to restore the free flow
of urine. Untreated hydronephrosis results in permanent
damage to the kidney that may lead to
RENAL FAILURE.
See also HEMATURIA; HORSESHOE KIDNEY; NEPHRITIS;
NOCTURIA; URINARY TRACT INFECTION (UTI).
hypercalciuria Excessive excretion of calcium in
the URINE. About 80 percent of people who have
kidney stones (NEPHROLITHIASIS) or BLADDER stones
(UROLITHIASIS) have hypercalciuria. In most people
the circumstance appears a combination of factors
that typically include high dietary calcium intake,
insufficient water consumption (resulting in low
urine volume), and physical inactivity. The water
and citrate content of the urine normally allows
most of the calcium the KIDNEYS extract from the
BLOOD to dissolve and pass from the body. When
urine volume and citrate concentration are low,
calcium in the urine combines with other minerals
(usually oxalate or phosphate) to form crystalline
structures. Over time these structures harden or
calcify (called calculi). Inactivity contributes to calculus
formation because it allows mineral sediments
to settle, facilitating their crystallization.