INTRODUCTION
Polycystic renal disease is a wide
spectrum of renal abnormalities in which the kidney
contains many cysts; these are often small and are
associated with the kidneys appearing large. These
anomalies cover two familial disorders, Infant Polycystic
Kidney Disease IPCKD (Type I Cystic Disease of Potter/
Congenital Hepatic Fibrosis complex) and Adult Polycystic
Kidney Disease APCKD (Type III Cystic Disease of
Potter). The classification of problems into infantile
and adult types reflects the wide spectrum of timing
of renal failure.
The infant type is autosomal recessive
with a recurrence risk of 25%. Renal disease is well
developed by births. The adult type is autosomal
dominant with a recurrence risk of 50%. This type
has a variable expression and usually presents in
later life but can present in-utero. One in 1,000
people carries the mutant gene (located on chromosome
16) which can be detected on DNA analysis. APCKD
is more prevalent in the general population that
IPCKD and is one of the most common causes of chronic
renal failure. Other associated anomalies include
cardiac malformations and cystic lesions in the liver,
pancreas, spleen, and gonads.
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ANTENATAL
Infantile and adult types can present
in fetal life and the diagnosis rests upon the appearance
of the kidneys, which are echogenic (bright) on ultrasound
due to the tiny cysts, and large. Both kidneys are
equally affected and all parameters of the kidney
are large. In infantile type the kidney outline is
smooth but can be bosselated in adult type. Echogenic
kidneys can occur for a number of other reasons and
in the absence of reduced liquor, or abnormal measurements
great caution should be exercised to reaching this
diagnosis. Maternal serum AFP may be raised due to
defective kidney re-absorption.
A variable degree of oligohydramnios
may occur. When severe bilateral renal disease results
in oligohydramnios, the bladder should not be seen,
and if a normal bladder is present, the diagnosis
is in doubt. If the liquor volume is normal until
24 weeks pulmonary hypoplasia is extremely unlikely,
and the general strategy will be to await the delivery
of the baby and make a postnatal assessment. Liquor
volume can be used as a guide to the renal function
after delivery, but the kidneys in fetal life have
little requirement to concentrate urine, and renal
failure after birth can follow even when the liquor
volume has been normal.
A team approach is required both to
establish the diagnosis and to manage the situation.
Genetic and paediatric input are vital, but even
after expert consultation a wide spectrum of possible
outcome is likely to be given.
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POSTNATAL
IPCKD generally has a poor prognosis,
depending on pulmonary status. In severe cases infants
die in the neonatal period as a consequence of oligohydramnios
sequence resulting in bilateral pulmonary hypoplasia.
The immediate care of a neonate who has been diagnosed
during pregnancy as having renal problems is to ensure
adequate respiratory function. Once breathing has
been established, the kidneys can be assessed by
ultrasound scan. The images will be easier to obtain
than during pregnancy, and the prenatal findings
will be rapidly superseded by postnatal information,
including the urine output and appearance of the
kidneys and bladder on ultrasound. Renal function
tests over a period of time will establish how well
the kidneys function in concentrating urine, with
rising values of urea, creatinine and potassium indicating
renal failure. Renal biopsy may be required to establish
the diagnosis.
APCKD has a variable expression, with many patients
asymptomatic until their 40s. The long-term prognosis
is dependent upon the extent of irreversible renal
damage. In both types of polycystic kidney disease,
renal failure is managed by dialysis and transplantation.
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WEST MIDLANDS DATA
Information to follow
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