Renal - Polycystic kidney disease

Question 1

Autosomal dominant polycystic kidney disease (ADPKD)

Answer 1

MC inherited kidney disorder
More common in white than black populations
4-10% of patients requiring dialysis or transplantation
Almost all cases caused by mutations in PKD1 or PKD2 genes
- PKD 1 mutations account for about 85% of cases and cause earlier renal failure cf. PKD2
- Median age of onset is middle age 50-60s for both PKD1 and PKD2 mutations

Question 2

Renal abnormalities in PKD

Answer 2

Multiple cysts in both kidneys - main clinical feature
Visible on USS, CT or MRI
Cysts fluid filled and prone to secondary complications
- distended cysts can cause chronic pain
- bleeding into a cyst –> acute pain + haematuria
- infection –> abscess

Renal stone formation common - caused by urinary stasis due to cysts
HTN common, can occur before renal function deteriorates
- reason unclear
Progressive renal failure common, but odes not occur in all patients - rate of deterioration also varies
- By aged 50, 50% have renal failure

Question 3

Extra renal manifestations of PKD

Answer 3

50% have cysts in the liver
- liver function usually normal, but large cysts can cause liver damage and abdominal problems
Cysts occur in spleen, pancreas, and others usually asymptomatic
Intracranial symptoms increased 4 fold in ADPKD - rupture —> SAH
- non invasive angiographic screening every 5 years
Cardiac valve incompetence - mitral and tricuspid
Anaemia less common in renal failure caused by ADPKD
- sustained EPO production by the kidneys

Question 4

Diagnosis of PKD

Answer 4

PC - haematuria or pain in loin or abdomen
Diagnosis more commonly made during investigation for abnormal renal function, hypertension, UTI or stones
FHx common
Examination - large palpable kidneys (sometimes liver and spleen) and HTN
USS most common method for screening relatives

Question 5

Treatment of PKD

Answer 5

No specific treatment
HTN and infection treated as normal
Renal failure –> dialysis or transplantation
Increased fluid intake to 3L/ day - suppresses vasopressin release, ?improves prognosis

Question 6

Juvenille PKD

Answer 6

Children can present with either ADPKD or autosomal recessive PKD (ARPKD)

• much rarer cf. AD variant
• caused by mutation in PKHD1 gene - encodes fibrocystin (membrane protein), localised to cilia in renal epithelial cells in the collecting duct and in developing ureteric bud

Question 7

Ultrasound diagnostic criteria

Answer 7

two cysts, unilateral or bilateral, if aged < 30 years
two cysts in both kidneys if aged 30-59 years
four cysts in both kidneys if aged > 60 years

Question 8

Other renal cystic disorders

Answer 8

VHL syndrome 
Tuberous sclerosis 
Medullary sponge kidney
Acquired cystic disease 
Simple cysts

Question 9

von Hippel-Lindau syndrome

Answer 9

Autosomal dominant condition, localised on chromosome 3
Renal cysts are premalignant (>50%), prophylactic bilateral nephrectomy is often necessary
Patients also at risk of multiple spinocerebellar haemangioblastomas, retinal angiomas, pancreatic cysts and phaeochromocytomas

Question 10

Tuberous sclerosis

Answer 10

Dominantly inherited (either chromosome 9 or 16), patients develop epilepsy, learning diasbility, hamartomas, renal cysts and angiomyolipomas (usually do not require surgery)
Skin lesions include shagreen patches, ash-leaf spots and adenoma sebaceum

Question 11

What is medullary sponge kidney?

Answer 11

Sporadic;
Cysts develop from ectatic collecting ducts
Calcify leading to classic nephrocalcinosis associated with MSK
Patients have a benign course, except that renal calculi and upper tract UTI are commonly associated

Question 12

Causes of acquired cystic disease

Answer 12

Cystic change is common in kidneys of dialysis patients, and especially in scarred kidneys
Most cysts develop from proximal tubules;
Present in >5% of patients at the onset of RRT and in >80% after 10 years dialysis
Malignant chance can occur, low incidence

Question 13

Simple cysts

Answer 13

Fluid filled, solid or multiple, usually harmless
Often incidental finding on USS; can grow considerably
Occasionally require percutaneous drainage because of persistent loin pain
Very common, affecting 2% of patients aged <50 years (incidence increases with age)
Bosniak system used to classify malignant risk of renal cysts (cyst wall thickening, calcification, septation, solid components); Bosniak I is simple, Bosniak IV malignant