Postnatal outcome of prenatally-detected “simple” renal cysts: Are they really simple?
Introduction
Solitary “simple” renal cysts detected on prenatal ultrasound scans have a reported incidence of approximately 1 in 1100 pregnancies [1]. Simple renal cysts found postnatally in childhood and in adulthood are usually asymptomatic and only require treatment when they become symptomatic or complex. We hypothesised that prenatally-detected cysts would therefore have the same outcome. The aim of our study was to elucidate the natural history of simple renal cysts detected prenatally and establish whether their postnatal outcome is really “simple”.
Section snippets
Methods
We performed a retrospective review of all antenatally-diagnosed simple renal cysts in a single tertiary referral centre (Centre for Fetal Care, Queen Charlotte's and Chelsea Hospital, London) between January 2005 and December 2016. A simple renal cyst was defined as a solitary, non-septated, non-communicating cyst in an otherwise normal kidney [2]. In the United Kingdom, an anomaly scan is performed at 18–20 weeks gestation. Anomaly scans were initially performed by sonographers, and any
Results
Simple renal cysts were identified in 28 fetuses at a median gestational age of 23 (20–36) weeks (Table 1). Cysts were bilateral in 2 (7%) and unilateral in 26 fetuses (14 left-sided, 12 right-sided), giving a total of 30 cysts. Median maximum diameter was 15 (4–35) mm at initial diagnosis and 17.5 (4–100) mm across all prenatal scans. No other abnormalities were identified on initial anomaly scans.
Discussion
Our study has shown that prenatally-detected “simple” renal cysts may pose a diagnostic challenge, even when being apparent on repeat prenatal scans performed by experienced specialists. Although it is likely that the cases later diagnosed as hydronephrosis and urinomas were never cysts in the first place – it is still worth noting that what appears to be a cyst, may not in fact be one. However, the intriguing finding is that in 5 (17%) cases, the affected kidney was subsequently found to be
Conclusion
We attempt to elucidate the natural-history of prenatally-detected “simple” cysts. The outcome is not always “simple”, especially those approaching larger than 20 mm in diameter over their prenatal course. A solitary cyst in an otherwise normal kidney may in fact be a step in the evolution of a multicystic dysplastic kidney, occasionally resulting in involution of the entire kidney. At the other end of the spectrum, it may in fact be a “simple” self-resolving entity, or an asymptomatic finding
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Declaration of competing interest
None declared.
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