Consequences of a congenital monokidney in patients with MCKD

According to the hyperfiltration hypothesis, a low number of nefrons in any
human subject will lead to hyperfiltration in the remaining nefrons and this
may be associated with systemic hypertension, proteinuria and
glomerulosclerosis. Children with a MCKD are born with an enlarged congenital
monokidney just as children with unilateral renal agenesis..Unknown is whether
these children have a monokidney with normal number of nefrons (hypertrophy) or
a monokidney with a higher number of nefrons (hyperplasia) The patients
according to the hyperfiltration hypothesis are at risk to develop
hypertension, protienuria and glomerulosclerosis.
In 2008 the group of Schreuder1 concluded that there is microalbuminuria and/or
hypertension present in 50% of patients with congenital solitary kidneys.
According to them this warrants a systematic follow-up of blood pressure,
proteinuria and renal function in all patients with congenital monokidneys
especially in patients with a low birth weight.
In 2005 Valentini et. al.2 have done a case report about a 10-year old female
patient in whom a high index of suspicion of renovascular hypertension existed.
Initially she was thought to have unilateral renal agenesis, because only a
solitary kidney could be visualizes on both ultrasound and renal scintygraphy.
But on MRI investigation she was found also to have an atrophic kidney. A
nephrectomy was performed which resulted in complete resolution of her
hypertension. It was hypothesised that this remnant kidney could potentially be
producing renin and could be responsible for her hypertension.
Schreuder used patients for his study with renal agenesis. The potential
confounder as described above was not taken into account. In our patient group
this potential confounder is eliminated because all dysplastic remnants have
been removed. A systematic review of H. Narchi3 witch included 29 studies with
a total of 1115 children concludes there is a mean probability of a child with
unilateral MCKD that is managed conservatively of developing hypertension of
5.4 per 1000. Their study could not make firm recommendations on the frequency
and duration of blood pressure measurement for these children.
There is sparse information involving the follow-up of children with MCKD.
Especially not when they are treated with a nephrectomy. Our population is the
largest known population of MCKD patients treated with a nephrectomy. It will
ad vital information for future generations of MCKD patients.Is regular
follow-up needed in patients with a congenital monokidney? Is the hypertension
found in children managed conservatively due to the potential confounder? Does
hypertension, proteinuria and glomerulosclerosis occur in our group?

Primary Objective: Mapping the consequences of a congenital monokidney on
kidney function for children with MCKD.
Secondary Objective(s):
- Giving recommendations about follow-up for children treated with nephrectomy
for MCKD.
- Defining better blood test for quantification of kidney function.
- Defining better urine test for quantification of kidney function.
- Quantification of the kidney overgrowth associated with nephrectomy for
children with MCKD.

Follow-up study.
Patients are asked to come for control to the Wilhelmina Children*s hospital.
Before the control they are asked to fill in a questionnaire and to participate
in the study. The setting will be the Wilhelmina Children*s hospital. The extra
time investment for the patient is estimated at 30 min. The duration of the
total study is estimated at 6 months.

The extra burden for the patients is minimal. The burden is an out patient
clinic control with physical examination, ultrasound of the kidney, blood and
urine sample. The benefit of the study for the patient is that its renal
function will be better monitored. The study is also group related, because
recent recommendations suggest a 2-yearly check-up. This to *catch* potential
renal failure in an early stage. If the minor participants do not participate,
the group will be too small.