Star fruit intoxication with acute kidney injury

Editor – I read with great interest the article by Mike Jones (Clin Med June 2012 pp 287–9) on recognising acute kidney injury (AKI). I would like to highlight a less common but important cause of AKI associated with star fruit nephrotoxicity.

Star fruit (Averrhoa carambola) is a popular fruit in tropical and subtropical countries, and its consumption is high in Asia, central America and tropical west Africa. Over the years, multiple case series have reported its nephro- and neurotoxicity in chronic kidney disease patients and, more recently, even in people with normal renal function.¹ This potentially fatal condition can be easily missed unless such history of star fruit intake is specifically sought, especially in patients with AKI with no apparent etiology.

The amount of fruit ingested which causes toxicity can be as low as approximately 25 ml, or half a fruit. However, its association with severity of symptoms is poor.² In patients with impaired renal function, a large amount of star fruit ingestion on an empty stomach appears to be a risk factor for toxicity. Onset of symptoms is within a few hours, commonly with intractable hiccups, vomiting and insomnia. In cases of moderate to severe intoxication, neuropsychiatric manifestations such as psychomotor agitation, mental confusion and seizure can occur, which may progress rapidly to coma and refractory status epilepticus, resulting in death.^1–3

Star fruit nephrotoxicity is believed to be due to its high oxalate content, which could cause acute obstructive oxalate nephropathy, as found on renal biopsy of affected patients.¹ Experimental study in rats has suggested that oxalate crystals may provoke AKI by inducing apoptosis of renal epithelial cells.⁴ Prompt treatment with intensified haemodialysis and haemoperfusion, close monitoring and supportive care has been proposed as an effective therapeutic approach. Peritoneal dialysis is ineffective in this condition, especially when there is neurological involvement.² Interestingly, it was reported that intoxicated patients with initial normal renal function had recovered without any dialysis given,¹ which suggests that baseline renal function is a prognostic factor of renal recovery.

In conclusion, star fruit intoxication may be life-threatening and this diagnosis should be considered in patients with unexplained AKI, especially if associated with neuropsychiatric symptoms. Emergency renal replacement therapy may be required for the management of this potentially treatable condition.