Star fruit toxicity: a cause of both acute kidney injury and chronic kidney disease: a report of two cases
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Star fruit (Averrhoa carambola) is commonly consumed as a herbal remedy for various ailments in tropical countries. However, the dangers associated with consumption of star fruit are not commonly known. Although star fruit induced oxalate nephrotoxicity in those with existing renal impairment is well documented, reports on its effect on those with normal renal function are infrequent. We report two unique clinical presentation patterns of star fruit nephrotoxicity following consumption of the fruit as a remedy for diabetes mellitus—the first, in a patient with normal renal function and the second case which we believe is the first reported case of chronic kidney disease (CKD) due to prolonged and excessive consumption of star fruits.
The first patient is a 56-year-old female diabetic patient who had normal renal function prior to developing acute kidney injury (AKI) after consuming large amount of star fruit juice at once. The second patient, a 60-year-old male, also diabetic presented with acute on chronic renal failure following ingestion of a significant number of star fruits in a short duration with a background history of regular star fruit consumption over the past 2–3 years. Both had histologically confirmed oxalate induced renal injury. The former had histological features of acute tubulo-interstitial disease whilst the latter had acute-on-chronic interstitial disease; neither had histological evidence of diabetic nephropathy. Both recovered over 2 weeks without the need for haemodialysis.
These cases illustrate the importance of obtaining the patient’s detailed history with respect to ingestion of herbs, traditional medication and health foods such as star fruits especially in AKI or CKD of unknown cause.
KeywordsStar fruit Nephrotoxicity Oxalate nephropathy
acute kidney injury
chronic kidney disease
Star fruit (Averrhoa carambola), locally known as “Kamaranka”, is believed to have originated from Ceylon and Moluccas and is now a popular fruit in tropical and subtropical countries . This plant has both nutritional as well as medicinal uses . In Sri Lanka, traditional use of the plant is common for conditions such as diabetes mellitus due to its hypoglycaemic effects . Despite the frequency of use, the dangers of consumption of star fruit are not known to many. Star fruit induced nephrotoxicity, manifesting as acute kidney injury (AKI) and neurological impairment in individuals with previous renal impairment is well documented [4, 5]. However, AKI developing in individuals with normal renal function is rare . We report two unique cases of star fruit nephrotoxicity whereby the first patient had normal renal function prior to developing AKI. We believe the second patient is the first reported case of chronic kidney disease (CKD) due to prolonged consumption of star fruit.
Case report 1
A 56-year-old female with well controlled diabetes mellitus for 12 years and no history of diabetic nephropathy presented with generalized weakness and lethargy for 12 days duration.
Case report 2
Star fruit is a rich source of oxalates. Nephrotoxicity leading to AKI is a result of both tubular obstruction by calcium oxalate crystals as well as apoptosis of the renal tubular epithelial cells . Risk factors for developing toxicity have been described as previously impaired renal function, ingestion of large amount of fruits or ingestion on an empty stomach . The symptoms are known to occur within hours of ingestion with the most well described being hiccups, nausea, vomiting and neuropsychiatric manifestations such as insomnia or seizures. Demonstration of oxalate crystals obstructing the tubules is diagnostic of star fruit induced nephropathy. Some patients with AKI can be managed without renal replacement therapy, but the majority require early renal replacement therapy in the form of haemodialysis or haemoperfusion [6, 9]. Peritoneal dialysis is ineffective especially in the presence of neurological manifestations .
Of the cases we report here, the first patient had consumed a large volume of star fruit juice at one sitting. It has been reported that even a volume of 25 ml would be adequate to cause nephrotoxicity . In the literature, most reported cases with oxalate induced nephrotoxicity had underlying renal dysfunction due to other causes and developed acute-on-chronic renal failure which has been described as potentially lethal . This case is unique in that she developed AKI with underlying normal renal function. There were only two other similar cases reported in literature [6, 8].
The second patient developed acute on CKD due to star fruit toxicity with prior mildly deranged renal functions. In the absence of clinical evidence of diabetic retinopathy and histological evidence of diabetic nephropathy, the pre-existing renal dysfunction cannot be attributed to diabetes mellitus. Histology of the renal biopsy also confirmed presence of chronic tubuo-interstitial renal disease. Detailed history did not reveal any other aetiology except the fact that he had prolonged consumption of moderate volumes of star fruit with recent ingestion of a large quantity over the course of 4 days. Accordingly, it could be postulated that the prolong consumption of star fruit had led to recurrent occult renal damage resulting in chronic interstitial nephritis and CKD. We believe this is the first reported case of its kind in the literature. It has been shown that calcium oxalate is one of the most reactive crystals and can evoke an inflammatory response leading to interstitial fibrosis, loss of nephrons, and eventually to chronic renal failure which further validates this point .
It is imperative that a history with respect to ingestion of foods such as star fruits is inquired especially in patients with AKI or CKD of unknown cause. Moreover, medical professionals should advise patients with CKD or those on dialysis to avoid eating star fruit. Even individuals with normal renal function should be careful not to ingest star fruits in excessive quantities since the second report shows that even regular moderate ingestion is harmful.
Written informed consent was obtained from both patients for publication of this case report and accompanying images (Additional file 1).
NN, AWMW, RAA, TJ and AM were the physicians who treated the patient in this report. SW and NVIR performed the histopathological analysis of the renal biopsies. All authors participated in preparation and discussions of about the manuscript and approved the final version. Written consent for publication was obtained. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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