Renal cysts
Key points
Multicystic dysplastic kidney (MCDK)
Ureteric bud does not contact metanephros - causes ureteral atresia and MCDK
Associated with Meckel-Gruber and Apert syndrome
60-70% involute by age 10
By definition should not have any solid renal tissue - and should have 0% function on DMSA
Often diagnosis just from USS
Indications for nephrectomy:
Large in infancy
Hypertension (MDT decision) - but not often associated with it- Historical association were likely errors confusing cystic kidneys with functioning tissue with MCDK
If not involuting < 5cm after age 10
Uncertain diagnosis - e.g. Some solid tissue
No indication for nephrectomy to prevent malignancy in pure MCDK
Cysts can be aspirated to aid nephrectomy
Multilocular cyst
Also called cystic nephroma
Needs DMSA
Often uncertainty about diagnosis so often nephrectomy performed
Simple cysts
Often asymptomatic and incidental
Conservative management - serial USS for 3 years
Make sure not early Polycystic Kidney disease
If symptomatic - can be deroofed
Patients on dialysis can develop cystic kidneys
Polycystic Kidney Disease
Autosomal recessive form (ARPKD) 1:10-40,000 (infancy, severe)
Autosomal dominant form (ADPKD) 1:200-1000 (Presents in later life)
Genetics
ARPKD - PKHD1 gene chromosome 6
ADPKD - PKD1 gene chromosome 16 in most, then PKD2 gene on chromosome 4
Antenatal features
ARPKD often visible on antenatal USS
If oligohydramnios present, indicates severe disease
Associations
ADPKD - berry aneurysm
10% adults on renal replacement therapy have ADPKD
History and Examination
ARPKD - enlarged kidneys, may cause mass effect
ADPKD - often presents later in life with haematuria, hypertension, loin pain
Management
Antihypertensives
ARPKD - May need bilateral nephrectomy to give space for peritoneal dialysis + transplant
Unilateral nephrectomy to prevent diaphragmatic splinting
ADPKD - may need nephrectomy to control hypertension
Tolvaptan - vasopressin 2 antagonist delays cyst development and renal failure
Outcome
ARPKD - mortality highest in 1st month of life - due to respiratory failure
Standard scenario
Child with incidental finding of renal cyst
Differentials:
1. MCDK
2. Cystic nephroma (Multilocular cyst) (DICER)
3. Simple cyst
4. Polycystic kidneys
5. Cystic Wilms
History:
Cysts on antenatal scans
Symptoms of pain, mass, haematuria
Family history of PKD, tumours
Examination:
Palpable mass
Blood pressure
Urine dip
Investigations:
Renal function
USS often sufficient
DMSA - should show 0% in MCDK
Genetics: PKD1, DICER
Urology MDT
Indications for nephrectomy/deroofing?
References
Essentials of Pediatric Urology, 3rd edition, 2022, Chapter 10 Cystic Renal disease