ADULT POLYCYSTIC KIDNEY DISEASE
Category: Urology
Abstract : Autosomal dominant (adult) polycystic kidney disease
(ADPKD) Definition Autosomal dominant inherited disorder leading to the
development of multiple expanding renal parenchymal
cysts. Epidemiology Incidence is 0.1%; 95% are bilateral. Symptoms
manifest in the 4th decade. ADPKD accounts for 10% of all cases of renal
failure. Pathology The kidneys reach an enormou
Autosomal dominant (adult) polycystic kidney disease
(ADPKD)
Definition
Autosomal dominant inherited disorder leading to the
development of multiple expanding renal parenchymal
cysts.
Epidemiology
Incidence is 0.1%; 95% are bilateral. Symptoms
manifest in the 4th decade. ADPKD accounts for 10% of all cases of renal
failure.
Pathology
The kidneys reach an enormous size due to multiple
fluid-filled cysts and can easily be palpated on abdominal examination.
Expansion of the cysts results in ischaemic atrophy of the surrounding renal
parenchyma, and obstruction of normal renal tubules. End-stage renal failure is
inevitable and occurs around the age of 50 yrs.
Associated
disorders
10 - 30% incidence of Circle of Willis berry aneurysms (associated
with subarachnoid haemorrhage); cysts of the liver (33%), pancreas (10%), and
spleen (<5%); renal adenoma; cardiac valve abnormalities; aortic aneurysms
and diverticular disease.
Aetiology
PKD-1 gene defects (chromosome 16)
account for 90% of cases; PKD-2 gene defects (chromosome 4) cause 10%, and now a
third gene, PKD-3 is also implicated. Pathogenesis theories include intrinsic
basement membrane abnormalities; tubular epithelial hyperplasia (causing tubular
obstruction and basement membrane weakness), and alterations in the supportive
extracellular matrix due to defective proteins, all of which may cause cyst
formation.
Presentation
Positive family history (50% inheritance);
palpable abdominal masses; flank pain (due to mass effect, infection, stones, or
following acute cystic distension due to haemorrhage or obstruction);
macroscopic (and microscopic) haematuria; UTI; and hypertension (75%). Renal
failure may present with lethargy, nausea, vomiting, anaemia, confusion, and
seizures.
Differential diagnosis
Renal tumours; simple cysts; von
Hippel - Landau syndrome (cerebellar and retinal haemangioblastomas; renal,
adrenal, and pancreatic cysts); tuberous sclerosis (adenoma sebaceum, epilepsy,
learning difficulties, with polycystic kidneys and renal
tumours).
Investigation
This depends on the presenting symptoms.
-
For suspected UTI culture urine.
- For haematuria urine cytology, flexible
cystoscopy, and renal ultrasound. On ultrasound the kidneys are small and
hyperechoic, with multiple cysts of varying size, many of which show
calcification. If the nature of the cysts cannot be determined with certainty on
ultrasound, arrange a renal CT.
- Renal failure will be managed by a
nephrologist. Anaemia may occur, though ADPKD may cause increased erythropoietin
production and polycythaemia.
- Renal imaging (ultrasound and CT are useful
for investigation of complications).
Treatment
The aim is to preserve
renal function as long as possible (control hypertension and UTI). Infected
cysts (abscesses) should be drained. Persistent, heavy haematuria can be
controlled by embolisation or nephrectomy. Progressive renal failure requires
dialysis and, ultimately, renal transplantation.
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