The power of a systematic review is only as good as the question being posed. In his review of the risk of hypertension in children with multicystic kidney disease (MCKD), Narchi misses the wider context.¹ There may be more than one relationship between the diagnosis of MCKD and blood pressure (BP). Perhaps the component in the mind of the author is that a multicystic dysplastic kidney might in itself be a cause of hypertension. This seems unlikely if the affected kidney is non-functioning and contains no renal elements. His review supports this presumption, although exceptions are clearly reported.² The majority of non-functioning multicystic dysplastic kidneys involute, so that a proportion of individuals who had MCKD originally are diagnosed later as having unilateral renal agenesis (RA), technically a misnomer in this case. It would make more sense to widen the enquiry to include this category.

An important consideration is the role of the contralateral kidney in the regulation of BP in these patients. Firstly, the contralateral kidney will prove to be radiologically abnormal in about a quarter of cases of MCKD or RA. Coarse focal scarring, hydronephrosis, or hypoplasia would be expected to have an impact on BP depending on the nature of the abnormality.

Radiologically normal solitary kidneys can also predispose to hypertension. Although they are significantly larger than normal paired kidneys and their complement of nephrons is unknown, there are good reasons to …