1. Background
Renal cystic diseases are an important cause of chronic kidney disease (CKD). They have
been classified in various ways, but from a clinical perspective it is perhaps most useful
to separate them into genetic such as (autosomal dominant polycystic kidney disease and
autosomal recessive polycystic kidney disease) and non-genetic disorders such as multicystic
dysplasia (MCDK) since this approach guides evaluation and management (1).
It is estimated that 70% of cases of kidney disease in childhood are congenital with
possibility of genetic basis (2). In the
kingdom of Saudi Arabia (KSA) due to the high rate of consanguineous marriages, this
percentage is preassembly even higher particularly for disease with an autosomal recessive
transmission (3, 4). There are few published epidemiological studies on the actual
incidence of various genetically transmitted diseases in KSA. Mattoo et al. reported two
decades back that children in KSA probably have higher incidence of polycystic kidney
disease (5).
Unilateral multicystic dysplastic kidney (MCDK) is one of the commonest abnormalities
detected by antenatal ultrasound (6) and the
second most frequent cause of a palpable abdominal mass in infants (7). Al-Ghwery et al. reported 35 cases from the Kingdom of Saudi
Arabia (KSA) with good prognosis on conservative management (8).
2. Objectives
In this study we report the pattern renal cystic disease in children referred to a tertiary
teaching hospital. We also look at the outcome of MCDK.
3. Patients and Methods
We have retrospectively reviewed our database of Pediatric nephrology unit at King
Abdulaziz University Hospital (KAUH) between 2006 and 2014. We have included all children
with cystic kidney diseases. We evaluated children with MCDK with follow up duration more
than 6 months as a separate group. We reviewed their medical and electronic files.
We recorded epidemiological data, history of consanguinity and data of height, blood
pressure, creatinine at presentation and on the last follow up. We have calculated estimated
glomerular filtration rate (e-GFR) using Schwartz formula (9). Hypertension was defined as blood pressure (BP) above 95
centile for age, height and sex.
At presentation and on the last follow up, we have staged CKD into stage 1 to 5, according
to calculated e-GFR (10). We recorded the need
for renal replacement therapy (RRT), its modalities and duration. The results were expressed
as mean ± standard deviation (SD).
Ethical approval was obtained for this study from the local ethical approval committee of
Faculty of Medicine at King Abdulaziz University.
4. Results
Fifty five children (30 males) were diagnosed as cases of renal cystic diseases. Seventeen
(30.1%) stopped following in less than 6 months. Nine (52.9%) of subjects were Saudis and
eight (47.1%) were non-Saudis. The Mean (SD) age at presentation to our hospital was 2.3
(3.6) years. The mean (SD) age at the last follow up was 5.7 (4.97) year. History of
consanguinity between parents was positive in 25 (96.2%) children, negative in one child and
unknown in 29 patients. Following the initial ultrasound (US) studies, children were
classified into 25 children as multicystic dysplastic kidney disease (MCDK), 22 as
polycystic kidney disease (PKD), 4 as nephronophthisis and 4 as renal cyst (Table 1).
Table 1.Summary of Clinical Data of Different Categories at Presentation After Excluding
Those With Less Than 6 Months Follow Up
| Diagnosis | Number (Males) | Mean Age (SD) at Presentation, y | Mean Initial Creatinine (SD), µmol/L | Mean Initial GFR (SD), mL/min/1.73 m2 | Protein-Uria (Dipstick Analysis) | Hypertension, % |
|---|---|---|---|---|---|---|
| 16 (12) | 0.92 (2.2) | 53 (27) | 57.4 (35.2) | Negative = 15, Trace = 1 | 1 (6.25) | |
| 17 (7) | 2.4 (3.2) | 194.4 (296.3) | 35.7 (27.3) | Negative = 12, Trace = 2, +1 = 2, +2 = 1 | 15 (88.2) | |
| 3 (1) | 9.3 (3.5) | 302.7 (354) | 42.2 (46.8) | Negative = 2, Trace = 1 | 2 (66) | |
| 2 (1) | 8 (7.1) | 38.5 (13.4) | 114.6 (7.1) | Negative = 2 | 0 (0) |
On the last follow up of 38 children who had more than 6 months follow up; 4 children had
died and 34 had different stages of CKD; 16 children had stage I, 7 children stage II, 6
children stage III, 2 children stage IV, and 7 children were in stage V CKD. Four children
received renal replacement therapy (2 hemodialysis and 2 renal transplantation) (Table 2). Seventeen (30.1%) children were lost to
follow up before 6 months; 9 (52.9%) were Saudis and 8 (47.1%) were from other
nationalities.
Table 2.Clinical Data of Different Groups at the Last Follow up
| Diagnosis | Duration of Follow up, y | Last Creatinine, Umol/L | Mean Last GFR (SD), mL/min/M2 | Stage of CKD | Protein-Uria | RRT |
|---|---|---|---|---|---|---|
| 3.4 (1.97) | 33.9 (13.5) | 103.9 (16.3) | Stage 1 = 13, Stage 2 = 3 | Negative = 15, Trace = 1 | None = 16 | |
| 3.2 (1.98) | 201.4 (166.3) | 35.1 (31.5) | Stage 1 = 1, Stage 2 = 2, Stage 3 = 6, Stage 4 = 2, Stage 5 = 6 | Negative = 12, Trace = 2, +1 = 2, +2 = 1 | None = 15, Hemodialysis = 2 | |
| 3.7 (0.6) | 216.7 (271.3) | 61.3 (41.8) | Stage 2 = 2, Stage 5 = 1 | Negative = 1, Trace = 2 | Transplantation = 2, None = 1 | |
| 2.3 (1.1) | 28 (11.3) | 146.6 (15) | Stage 1 = 2 | Negative = 2 | None = 2 |
When we analyzed MCDK as a separate group, 11 children had nuclear study (DMSA:
dimercaptosuccinic acid scan) which confirmed the diagnosis. 9 children had less than 6
months follow up duration (7 were lost to follow up) and therefore were excluded. On last
follow up 9 out of 16 children, had involutes of their kidneys as shown by the US, at mean
age of 2.6 (1.3) years.
At initial presentation, MCKD was the commonest type of pediatric cystic kidney disease
occurring in KAUH accounting for 45.5% of the cases with male to female ratio of 3:1.
However, only 16 cases had follow up of 6 months. Their Mean (SD) age at presentation was
0.92 (2.2) years. Mean (SD) of their initial serum creatinine (SD) was 53 (27) umol/L.
Initial urine analysis showed negative proteinuria in 93.8% of the cases and trace proteins
in one (6.2%) child. Also, initial blood pressure was measured and was normal in 93.8% of
the cases and only one case was hypertensive. All children except one were diagnosed
antenatally.
Table 2 gives a summary of children with
MCKD. Patients were followed up for the duration of 3.4 (1.97) years. Last creatinine was
33.9 (13.5) µmol/L. Twenty five percent were in stage I CKD and did not progress while the
other 75% of the cases had regressed to stage I CKD (75%) and stage II CKD (25%).
5. Discussion
In this retrospective analysis of a single center experience, we observed that MCDK was the
commonest renal cystic disease with the majority diagnosed antenatally. This is similar to
previous reports (6, 7). The estimated incidence of MCKD is approximately 1 in 3640
births (11). More than 90% of our cohort were
diagnosed antenatally which is in line with previous observation that MCDK is usually
diagnosed early in life and more often with routine use of prenatal ultrasonography. This
also reflects the improvement in antenatal services in the Kingdom of Saudi Arabia (KSA)
over the last two decades (12, 13).
A considerable number of our children with MCDK were lost to follow up and this could be
explained by the possibility of relaxation of the parents after counseling about the good
prognosis of this condition. Some reports previously suggested that once the diagnosis of
MCDK is made, no urological follow-up is needed. The primary care provider should monitor
patients with MCDK for hypertension, abdominal mass and urinary tract infection (14). Recent reports indicate that a substantial
proportion of children with single functioning kidney develop renal injury during childhood,
at median age of 12.8 years. Therefore, close follow-up of albuminuria, blood pressure and
eGFR are warranted to identify chronic kidney disease in its early stages (15). The importance of the long term follow up
should be stressed to the parents, despite of good prognosis of MCDK.
In the majority of cases, a unilateral MCDK will completely involute over time (16). We have observed that as 56% of MCDK cases
were involuted at mean age of 2.6 (1.3) years. This is similar to previous reports
emphasizing that most MCDK kidneys undergo involution during the first five years of life
(16-18). The other study showed that 33% of the MCDK kidneys had completely involuted
at 2 years of age, 47% at 5 years, and 59% at 10 years (19). There is usually compensatory hypertrophy of the
contralateral kidney which maintains normal kidney function (17). Al-Ghwery et al. from the central province of KSA reported
that 86% of children with MCDK had a complete or partial involution of the affected kidneys
at mean age of 43.6 months (8).
Hypertension is very rare in children with MCDK and a recent systematic review of 29
studies revealed that only six cases in 1115 eligible patients were hypertensive (20). Resolution of hypertension is usually
achieved by nephrectomy (21), but hypertension
may persist even after removal of MCDK (22).
Hypertension could be rennin mediated (23) and
can be transient in infants where there are difficulties in measurement of BP (24, 25). It is still uncertain how often and for how long children with a unilateral
MCDK need to be assessed for hypertension. We measured the blood pressure at the initial
presentation and regularly after that. On the last follow up, the majority were normotensive
with only one case with high BP readings.
Children with MCKD are increasingly managed conservatively and are followed up throughout
childhood because they are perceived to be at increased risk of developing Wilms’ tumor.
This risk is still poorly defined and somewhat controversial. Therefore, the strategy and
the duration of follow up do not seem to be based on evidence. The development of a registry
for children with MCKD would increase the precision of their risk estimate to develop Wilms’
tumor (6).
Isolated unilateral MCDK has good prognosis, bad prognosis is linked to its association
with other anomalies as well as to bilateral MCDK when end stage kidney disease will be a
risk (26).
The majority of children with PKD in our cohort were hypertensive and their CKD progressed.
This is expected and similar to previous reports from other parts of the world (1).
Our study has several limitations which include the retrospective nature of the study,
small number of patients and rather short duration of follow up.
5.1. Conclusion
MCKD is the commonest renal cystic disease in children and it has good prognosis on
conservative management.
