Weeping sponge kidney: an unusual phenomenon that should be considered in cases of severe renal haemorrhage.

To describe the clinical presentation, imaging evaluation, endovascular management, and outcomes of multifocal renal capsular haemorrhage, "weeping sponge kidney", and to identify associated risk factors and the pathophysiological mechanism behind this condition. This is a case series in which clinical information for each of the cases was collected retrospectively from electronic patient notes as well as the radiology information and picture archiving and communication systems. Four consecutive cases were included in the series. All of the cases were treated successfully with embolisation. Three of the four patients had chronic renal failure with renal atrophy, which are patient factors that appear to be associated with multifocal renal capsular haemorrhage. Based on the procedural findings and the published literature, a pathophysiological mechanism is described to explain this condition and the relevance of the collateral arterial supply to the kidney in such cases is discussed. Small subcapsular haematomas are usually self-limiting but in patients with renal failure, there may be an increased risk of developing a weeping sponge kidney, which can be life-threatening. The endovascular treatment for multifocal haemorrhage differs from that for a single bleeding point, especially if preservation of renal function is not a priority.

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