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Renal Cyst Evolution in Childhood
TAKE-HOME MESSAGE
- Renal cysts are an uncommon finding in children; however, their presence is associated with a degree of clinical uncertainty owing to the potential for polycystic kidney disease or malignant transformation. The likelihood of either in this clinical context is not well-defined. Among 87 children (25% under 1 year of age) with a simple or minimally complex renal cyst discovered on ultrasound, the rate of eventual diagnosis of autosomal dominant polycystic kidney disease and autosomal recessive polycystic kidney disease was 13% and 1%, respectively. Although 3.5% underwent surgical intervention (due to increasing size and complexity of the cyst), no patients had malignant transformation, and 12% had complete resolution of the cyst.
- According to these data, simple or minimally complex renal cysts do not typically require additional treatment nor do they develop into polycystic kidney disease.
– Joshua Cohn, MD
abstract
This abstract is available on the publisher's site.
Access this abstract now Full Text Available for ClinicalKey SubscribersIntroduction
Children with renal cysts often undergo ultrasound (US) monitoring to identify malignant transformation or polycystic kidney disease (PKD). However, the utility of ongoing surveillance is uncertain.
Objective
To assess the natural history of simple or minimally complex cysts and the proportion of progression to autosomal dominant polycystic kidney disease (ADPKD), autosomal recessive polycystic kidney disease (ARPKD) or malignancy.
Study Design
Institutional review board approved retrospective chart review at one institution between 2004-2014. Eligible patients had ≤3 simple or minimally complex cyst(s) discovered on US without an initial diagnosis of multicystic dysplastic kidney, genitourinary malignancy, ADPKD, or ARPKD. Patient demographics and cyst details were recorded at identification and follow-up visits. Logistic regression was used to examine univariate association between diagnosis of ADPKD/ARPKD and each recorded variable.
Results
We identified 87 eligible patients. 22 patients were identified antenatally or in the first year of life; the remaining 65 were identified at >1 year of age, median 7.6 years (IQR: 4.2, 10.6). The majority (60/87, 69%) had a solitary cyst at initial US. The median length of follow-up was 4.1 years (IQR: 1.9, 6.8) with median 3 follow-up US (IQR: 2, 5). Eleven patients (12.6%) were diagnosed with ADPKD. One patient (1.2%) was diagnosed with ARPKD. There were a median 2 follow-up US (IQR:1,4) over a a median of 2.2 years (IQR:1.0, 3.9) to obtain diagnoses of ADPKD or ARPKD. No patients developed malignancy.
Discussion
Our results reveal that children identified to have a small number of simple or minimally complex renal cysts on initial US are unlikely to require additional treatment for these cysts, as transformation to PKD or malignant condition is rare. Supporting this are results from literature that although simple cysts in childhood may evolve over time, most do not require any surgical or invasive treatment in the long term. Limitations include retrospective design and single institution.
Conclusions
ADPKD/ARPKD diagnosis occurs early in follow-up evaluation in children with simple or minimally complex cysts. Malignant transformation did not occur in any patients in this study.
Additional Info
Disclosure statements are available on the authors' profiles:
Rediger and colleagues from Ottawa offer guidance for a problem common to pediatric urologists, surgeons, nephrologists, and general pediatricians: namely, what to do about the incidental finding of isolated renal cysts in children. Multicystic kidneys, polycystic kidney disease (PKD), and complex cysts are distinct conditions, although they sometimes overlap with what, at first, appears to be a single renal cyst or a few simple renal cysts. Furthermore, responsible physicians are reluctant to offer life-long guarantees of safety after initial discovery or short-term follow-up of renal cysts. This problem is similar to that imposed by incidentalomas discovered in various organs with computed tomography or magnetic resonance imaging. More generally, this is the matter of too much information, or TMI.
Genitourinary imaging by ultrasonography came of age as a practical urologic tool in the 1980s. I recall those early days when, at Walter Reed Army Medical Center, we experimented with crude B-mode ultrasonography to interrogate testes for tumors or viability. Coincidentally, it was around that time, 1981 to be specific, when Gordon Sumner wrote the lyrics to a song called Too Much Information:
“Too much information running through my brain,
Too much information driving me insane...”
The world is even more replete with incidental information since Sting and The Police recorded that song in their album Ghost in the Machine. The quality and precision of ultrasound interrogation now reveals increasingly tiny anatomic details, anomalies, and imperfections that cause patients great anxiety, and far worse, drives parents of children with simple renal cysts to near-insanity with unnecessary worry.
This Canadian study noted the generally accepted 0.22% prevalence of simple renal cysts, that being roughly 1 in 500 studies. They screened their practice over a 10-year period for all patients coded for renal cystic conditions. Finding 695 children, the authors performed the grunt work of manual chart review to identify 87 with one to three renal cysts without clear etiology. Interestingly, most of these (n = 65) were identified after 1 year of age; so, they were either missed antenatally or developed subsequently. With a median follow-up of 4.1 years and median of three sonograms, the authors identified 11 patients (12.6%) to have PKD, all but 1 being autosomal-dominant, whereas PKD in the single autosomal-recessive patient was evident at 13 days of age based on CT results. Nearly half of the autosomal-dominant PKD patients had positive family histories for the condition.
Of 12 patients who underwent further detailed imaging, the Ottawa team prudently limited them to a single CT or MRI. No patients had a renal biopsy, while 3 underwent surgical intervention related to cyst enlargement, complexity, or suspected Wilms’ tumor. The pathology in the child with suspected tumor revealed autosomal-recessive PKD. A total of 10 patients (11.5%) underwent cyst resolution.
This excellent review of 87 patients gives confidence that most children with isolated renal cysts in families without a positive history of renal problems will have little to worry about. Most children, however, does not mean all children, and this observational study with a median of 4.1 years’ follow-up is hardly a lifetime. Although the article abstract discourages routine surveillance beyond 2 to 3 years of age, the conclusion in the body of the paper more wisely notes that “the clinician could consider” a repeat sonogram in late adolescence. Certainly, neither prolonged yearly sonograms nor more extensive imaging is warranted in most of these children; but, until simple cysts conclusively disappear, the diagnosis of a renal cyst should be listed among the relevant problems and comorbidities that populate modern electronic medical records, and, more importantly, that diagnosis should flash through our brains even in the shrinking intervals during which we consider the sum-totals of our patients. Rediger et al. have nicely informed us that we no longer need over-react to isolated renal cysts; however, the diagnosis should not be tossed into the TMI dustbin.