Material and Method: We retrospectively assessed 20 children with unilateral multicystic dysplastic kidney between January 2005 and December 2009. Mean duration of follow-up was 35 ± 8.7 months. All children with multicystic dysplastic kidney underwent nephrectomy. Patient characteristics, the pathology findings, associated urinary tract anomalies and results of management were reviewed.
Results: Abdominal ultrasound, voiding cystourethrography and renal scintigraphy revealed vesicoureteral reflux in 3 (15%) children, ureteropelvic junction obstruction in 3 (15%) children, and a duplex system in the contralateral kidney in 1 (5%) child. Blood pressure values, serum urea, creatinine and urinalysis were within normal range in all children during follow-up.
Conclusion: A conservative approach to children with multicystic dysplastic kidney has been advocated, but surgical removal is also another management modality on the basis of risk of hypertension, mass effect, potential for malignant change, and cost of repeated ultrasound examination.
All children with MCDK underwent nephrectomy in this series. The indication for nephrectomy was hypertension in 4 patients, abdominal mass in 6 patients, and recurrent urinary infection in other patients. The diagnosis of MCDK was confirmed by histopathology in all children who underwent nephrectomy. Histopathologically, variably sized cysts replaced the renal parenchyma in the sections. Characteristically, large cysts were lined by flattened cuboidal epithelium (Figure 1) and an intervening parenchyma that was fibrotic with islands of cartilage and rare glomeruli. Frequently glomeruli appeared immature and aberrantly formed (Figure 2). Primitive or dysplastic ducts were lined with columnar epithelium and surrounded by collars of spindle cells (Figure 3). Immature cartilage was seen (Figure 4). Blood pressure values, serum urea, creatinine and urinalysis were within normal range in all children.
Figure 1: Dysplastic kidney containing multiple cysts (H&E; x100).
Figure 2: Aberrantly formed glomeruli (H&E; x40).
Figure 3: Primitive-appearing tubules surrounded by condensed mesenchymal cells (H&E; x100).
Various etiological factors have been held responsible for MCDK. Teratogens, such as in utero viral infections and medications, have also been implicated. In one study, 1–3% of children with congenital kidney malformations had amniotic fluid that produced cultures positive for enterovirus, cytomegalovirus or adenovirus[14]. A series of four infants with MCDK and epileptic mothers treated during pregnancy with antiepileptic drugs raises the possibility that medications may be a contributing factor[15].
Many concurrent urinary tract abnormalities have been described in patients with MCDK. The most common and potentially significant urologic defect seen is VUR to the contralateral kidney. The largest study, with 143 patients that underwent a VCUG, describes a VUR incidence of 19% to the contralateral kidney and 16% to the MCDK[1]. Contralateral VUR was seen in 15% of the children in our series. Other urinary tract abnormalities, such as contralateral UPJ obstruction are often seen in patients with MCDK. In our series, contralateral UPJ obstruction was seen in 15% of the children. According to the literature it has been described in 7–15% of individuals with MCDK[16].
The natural history is unclear and many studies have shown that MCDK tends to involute. Complete involution rates vary from 19–74% over 9 months to 10 years. This involution may be so severe that the affected kidney disappears in subsequent sonograms[1,17]. In patients with complete MCDK involution, 92% had compensatory hypertrophy of the contralateral kidney[18]. In one long-term, prospective study of 33 children with a MCDK, 24% had compensatory hypertrophy at birth, and 52% demonstrated compensatory hypertrophy in later childhood, with a mean follow-up duration of 4.9 years[19].
Another management question in MCDK disease is frequency of hypertension and has been provided as a reason for nephrectomy of the affected kidney[20,21]. Furthermore, case reports have described how MCDK patients with hypertension were cured by nephrectomy of the involved kidney[22]. In a study of 887 patients with MCDK, only 6 (0.7%) had hypertension[23]. In another series of 20 patients older than 11 years who had MCDK, only 2 had hypertension and the blood pressure was not controlled by nephrectomy in these patients[22].
Of greater concern is the potential for malignant degeneration in a MCDK. Most case reports have been of Wilms tumor, renal cell carcinoma and urothelial carcinomas that developed in a MCDK[25,26]. The incidence of Wilms tumor developing in MCDK is greater than fourfold, citing an incidence of 1 in 8000 general population and 1 in 2000 in the MCDK population. This fourfold increase does not make a case for prophylactic nephrectomy[27]. In our series there were no patients with malignant degeneration. Flank pain as an adult is another risk of MCDK that is left in situ, and in such cases the pain usually responds to nephrectomy[23]. This was the main indication for nephrectomy in our series.
Identification of MCDK in newborns has dramatically increased with the use of fetal ultrasound[28]. If MCDK is suspected on prenatal ultrasound, a postnatal ultrasound will confirm the diagnosis and screen for other urinary tract abnormalities[29]. Recent improvements regarding the natural history of MCDK, especially with regard to prenatal diagnosis and conservative management, have changed the approach to this anomaly. Until the mid- 1980s, the management of MCDK patients often consisted of nephrectomy. Since then, with the improvements in fetal US, such management has been replaced by clinical and sonographic follow-up of the patients. Some studies have shown that conservative management seems to be a safe option; the prevalence of complications is negligible and most of the affected units have partial or complete involution on US. Recently, a comparative study between surgical and conservative treatments has not revealed any significant difference in the frequency of complications for the patients[30].
A conservative approach to children with MCDK has been advocated, but others have suggested surgical removal on the basis of risk of hypertension, mass effect, potential for malignant change, and cost of repeated US examination. According to our experience, the conservative approach is a reliable method for patients who can attend regular followup. Nephrectomy can be undertaken if any complication occurs. Children with MCDK therefore need a protocol of initial investigation and regular follow-up, even if the MCDK is removed, to determine the growth and function of the contralateral kidney.
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