Acute oxalate nephropathy induced by star fruit in rats

Secondary oxalate nephropathy and kidney transplantation

PURPOSE OF REVIEW

Secondary hyperoxaluria is associated with poor kidney allograft outcomes after the kidney transplant. Calcium oxalate (CaOx) deposition is common in early allograft biopsies leading to acute tubular necrosis and poor kidney allograft function. Though treatment options for secondary hyperoxaluria are limited, it is crucial to identify patients at increased risk of oxalate nephropathy after the transplant.

RECENT FINDINGS

Recent data suggest that significant changes in renal replacement therapies and dietary modifications in high-risk patients can prevent kidney allograft damage from the calcium oxalate deposition leading to improve allograft outcomes.

SUMMARY

The accurate and timely diagnosis of secondary oxalate nephropathy in kidney transplant recipients is paramount to preserving graft function in the long-term. This review will discuss the incidence, risk factors, prevention, and management of oxalate nephropathy in the kidney allograft.

Nephrotoxicity and neurotoxicity following star fruit (Averrhoa carambola) ingestion: a narrative review

In recent times, star fruit (Averrhoa carambola) nephrotoxicity and neurotoxicity have been increasingly reported, both in individuals with pre-existing renal disease and those with previously normal renal function. We summarise the clinical findings of star fruit toxicity in humans and outline the important pathogenetic insights provided by animal studies. Google Scholar, EMBASE, Scopus and PubMed were searched from 1995 through July 2020 for case reports/series on renal or neurological manifestations of star fruit toxicity in humans and mechanisms of star fruit toxicity in animal studies. Ten case series and 28 case reports in humans (total number of individuals=136) were included and 8 animal studies were analysed. Ninety-four (69.1%) patients had prior renal impairment. Renal histology showed acute oxalate nephropathy with tubulointerstitial nephritis or tubular necrosis. Neurotoxicity manifestations ranged from hiccups to status epilepticus. Oxalate and caramboxin are considered the main substances causing nephrotoxicity and neurotoxicity. Caramboxin inhibits GABA binding and activates the glutamatergic receptors. Haemodialysis improved outcomes in neurotoxicity. Nephrotoxicity and neurotoxicity need to be looked for with star fruit toxicity, both in individuals with abnormal or normal renal function. Once star fruit intoxication is identified, early renal replacement therapy should be considered. Further studies on the mechanisms of star fruit toxicity are needed.

Mechanisms of star fruit (Averrhoa carambola) toxicity: A mini-review

The star fruit (Averrhoa carambola) is consumed in high amounts in Asia and Central/South America. It contains oxalic acid and caramboxin. In some individuals, its ingestion may lead to nephrotoxicity and neurotoxicity. The nephrotoxic effect is due to oxalate deposition in renal tubules resulting in acute tubular necrosis and interstitial nephritis. Although uraemic encephalopathy secondary to acute kidney injury may play a role, a shift to an excitatory state of the central nervous system (CNS) by caramboxin through activation of excitatory neuroreceptors and inhibition of GABA receptors leads to mental confusion, seizures and status epilepticus seen with star fruit intoxication. In this mini-review, we discuss the mechanisms of star fruit-related toxicity.

N-acetylcysteine protects against star fruit-induced acute kidney injury

Background: Star fruit (SF) is a popular fruit, commonly cultivated in many tropical countries, that contains large amount of oxalate. Acute oxalate nephropathy and direct renal tubular damage through release of free radicals are the main mechanisms involved in SF-induced acute kidney injury (AKI). The aim of this study was to evaluate the protective effect of N-acetylcysteine (NAC) on SF-induced nephrotoxicity due to its potent antioxidant effect.

Materials and methods: Male Wistar rats received SF juice (4 mL/100 g body weight) by gavage after a 12 h fasting and water deprivation. Fasting and water deprivation continued for 6 h thereafter to warrant juice absorption. Thereafter, animals were allocated to three experimental groups: SF (n = 6): received tap water; SF + NAC (n = 6): received NAC (4.8 g/L) in drinking water for 48 h after gavage; and Sham (n = 6): no interventions. After 48 h, inulin clearance studies were performed to determine glomerular filtration rate. In a second series of experiment, rats were housed in metabolic cages for additional assessments.

Results: SF rats showed markedly reduced inulin clearance associated with hyperoxaluria, renal tubular damage, increased oxidative stress and inflammation. NAC treatment ameliorated all these alterations. Under polarized light microscopy, SF rats exhibited intense calcium oxalate birefringence crystals deposition, dilation of renal tubules and tubular epithelial degeneration, which were attenuate by NAC therapy.

Conclusions: Our data show that therapeutic NAC attenuates renal dysfunction in a model of acute oxalate nephropathy following SF ingestion by reducing oxidative stress, oxaluria, and inflammation. This might represent a novel indication of NAC for the treatment of SF-induced AKI.

Acute kidney injury associated with ingestion of star fruit: Acute oxalate nephropathy

Starfruit (Averrhoa carambola) and its juice are popular in the Indian subcontinent as an indigenous medicine. Oxalate concentration in this fruit and it's freshly prepared juice is very high. We present a report of patients presenting with acute kidney injury due to oxalate nephropathy admitted in a single center. All patients had history of ingesting star fruit. Patients became symptomatic after 10-12 h of eating and main symptoms were pain abdomen and decrease in urine output. Three patients needed hemodialysis. All improved with complete renal recovery. Taking star fruit in large amount on an empty stomach and in a dehydrated state is a risk factor for nephrotoxicity.

Nephropathy in dietary hyperoxaluria: A potentially preventable acute or chronic kidney disease

Hyperoxaluria can cause not only nephrolithiasis and nephrocalcinosis, but also renal parenchymal disease histologically characterized by deposition of calcium oxalate crystals throughout the renal parenchyma, profound tubular damage and interstitial inflammation and fibrosis. Hyperoxaluric nephropathy presents clinically as acute or chronic renal failure that may progress to end-stage renal disease (ESRD). This sequence of events, well recognized in the past in primary and enteric hyperoxalurias, has also been documented in a few cases of dietary hyperoxaluria. Estimates of oxalate intake in patients with chronic dietary hyperoxaluria who developed chronic kidney disease or ESRD were comparable to the reported average oxalate content of the diets of certain populations worldwide, thus raising the question whether dietary hyperoxaluria is a primary cause of ESRD in these regions. Studies addressing this question have the potential of improving population health and should be undertaken, alongside ongoing studies which are yielding fresh insights into the mechanisms of intestinal absorption and renal excretion of oxalate, and into the mechanisms of development of oxalate-induced renal parenchymal disease. Novel preventive and therapeutic strategies for treating all types of hyperoxaluria are expected to develop from these studies.

Nephrotoxicity of alternative medicine practice

The use of alternative medicine is highly prevalent around the world; in many areas, this is so because of lack of access to, or trust in, Western medicine, and also because they are considered "natural" and therefore safe. The kidney is an organ vulnerable to toxic insults by virtue of its anatomy and function. Reports of nephrotoxicity associated with alternative medicine use encompass all forms of renal dysfunction, ranging from electrolyte abnormalities and proteinuria to acute and CKD, renal failure, and death. In countries where intensive care and dialysis support are not available, mortality is high. Mechanisms of alternative medicine-associated kidney injury include direct nephrotoxicity, which may be augmented by underlying predisposing conditions such as dehydration; contamination, or adulteration of remedies; inappropriate use or preparation of a remedy; or interactions with other medications. The use of alternative medicines is underreported to clinicians. Because many patients strongly believe in the powers of alternative medicines, it is important that alternative medicines not be demonized as a whole, but that their use and consequences be closely observed and reported to build a more comprehensive understanding of their impact in our clinical practice and to foster research on the potential harm or, in some cases, possible benefits.

Sustained low-efficiency daily diafiltration with hemoperfusion as a therapy for severe star fruit intoxication: a report of two cases

Over the past decade, star fruit (Averrhoa carambola) intoxication decreased in the Taiwanese society due to improved public education on chronic kidney disease (CKD). Various complications including hiccups, altered levels of consciousness, coma, and seizures have been reported in individuals with renal failure who ingested fresh star fruit or star fruit juice. A high mortality rate (from 33 to 80%) was observed in patients with altered levels of consciousness, despite prompt dialysis and supportive care. According to previous case reports, the proposed treatment of choice for severe star fruit intoxication may be continuous renal replacement therapy with or without hemoperfusion. We report two cases of star fruit intoxication with stage V CKD (one case is predialysis) presenting with coma and generalized tonic-clonic seizures. The two patients were treated with sustained low-efficiency daily diafiltration (SLEDD-f) and charcoal hemoperfusion. Status epilepticus was controlled fairly quickly after treatment with SLEDD-f and hemoperfusion. However, the outcomes in this report are still poor (both remained comatose; one of two patients died). Currently, there are no data for the use of SLEDD-f with hemoperfusion for severe star fruit intoxication. SLEDD-f with charcoal hemoperfusion may play a role in managing refractory status epilepticus in patients with severe star fruit poisoning.

Severe encephalopathy after ingestion of star fruit juice in a patient with chronic renal failure admitted to the intensive care unit

Star fruit (Averrhoa carambola) is a popular tropical fruit that is usually consumed as fresh fruit or fruit juice. Consumption of star fruit by patients with chronic renal failure can lead to neurologic symptoms. The present report describes the clinical course, management, and outcome of a patient with chronic renal failure admitted to an intensive care unit after ingestion of star fruit juice 2 days before hospital admission. A case of nausea, vomiting, intractable hiccups, and severe encephalopathy along with mental confusion, disorientation, agitation, and seizures in a 53-year-old woman is presented. The patient's ventilatory pattern worsened, with development of dyspnea and tachypnea, which resulted in her transfer to an intensive care unit. Although hemodialysis was performed and the septic shock was adequately treated, the patient died on the fifth day after hospital admission. The susceptibility of patients with chronic renal failure to star fruit and the severity of intoxication are poorly known by intensivists. This case demonstrates that star fruit consumption should be considered as a cause of rapid deterioration in the renal function of patients with underlying chronic renal failure, potentially resulting in a fatal outcome.

Acute kidney injury associated with the use of traditional medicines

The use of traditional medicine is common worldwide, with rates of use of over 80% in some populations. Considering the large number of people using traditional remedies throughout the world, it does seem that most do so without major adverse effects. Nevertheless, many folk medicines can cause kidney injury. Drug-induced nephrotoxicity reportedly contributes to up to 26% of cases of hospital-acquired acute kidney injury (AKI) and 18% of cases of community-acquired AKI globally, and folk remedies account for up to 35% of cases of AKI in the developing world. The kidney is highly susceptible to toxic insults because its intrinsic functions expose it to exceptionally high concentrations of any particular toxic substance. Clinical syndromes of nephrotoxicity can be defined according to the predominant regions of the kidney affected by the toxin, and reversibility of the injury is likely related to the severity and nature of the injury and also to the duration of toxin exposure. In countries with well-developed health-care systems, a large proportion of patients with nephrotoxicity will recover at least some renal function with adequate supportive care and dialysis. Health-care practitioners in all countries should be aware of the high prevalence of the use of alternative therapies and should be proactive in obtaining this information from patients. In poorer countries, where large proportions of the population rely on traditional medicine, attempts should be made to integrate traditional healers into the health-care system.

Mechanisms of star fruit-induced acute renal failure

We have previously discovered that star fruit can induce oliguric acute renal failure. To investigate the mechanisms of star fruit-associated acute oxalate nephropathy, the nephrotoxic effect of star fruit was examined in both cellular experiments and animal models. We evaluated renal function, pathological changes in kidney tissues and apoptotic effects using terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) assay in four groups of rats -- a control group (CG), fed with tap water (1); a star fruit group (SG), fed with star fruit juice naturally containing 0.2M oxalate (2); and oxalate groups (OxG), fed with 0.2M (3) or 0.4M (4) oxalate solution. The effects of both star fruit juice and oxalate on MDCK cells were also analyzed by flow cytometry. We found that the mean creatinine clearance was significantly lower in the SG, 0.2M OxG and 0.4M OxG. Dose-dependent apoptotic effects were evident from the TUNEL assay, and flow cytometry analysis of treated MDCK cells showed dose- and time-dependent effects. Our findings suggest that star fruit juice produces acute renal injury, not only through the obstructive effect of calcium oxalate crystals, but also by inducing apoptosis of renal epithelial cells, which may be caused by the levels of oxalate in the fruit.

The role of oxalate in star fruit neurotoxicity of five-sixths nephrectomized rats

To investigate the role of oxalate in star fruit neurotoxicity, rats were given star fruit or oxalate after a sham operation or modified five-sixths nephrectomy; namely, star fruit (SC) or oxalate (OxC) for sham-operated rats and star fruit (SNx), calcium gluconate treated star fruit juice (SCaNx), or oxalate (OxNx) for nephrectomized rats. After feedings, none of the rats in SC, OxC, and SCaNx groups developed movement disorders or died, while all rats in SNx group and OxNx group presented movement disorders and two rats in SNx group and four rats in OxNx group died within minute to hour after development of myoclonic jerk and/or tonic-clonic convulsion. The plasma oxalate levels rose significantly only in the SNx group and OxNx group that also presented clusters of generalized spike-waves in the electroencephalographic recordings. In conclusion, oxalate may play a key role in star fruit neurotoxicity in nephrectomized rats and probably in uremic patients.

Food Poisoning

Food poisoning is encountered throughout the world. Many of the toxins responsible for specific food poisoning syndromes are no longer limited to isolated geographic locations. With increased travel and the ease of transporting food products, it is likely that a patient may present to any emergency department with the clinical effects of food poisoning. Recognizing specific food poisoning syndromes allows emergency health care providers not only to initiate appropriate treatment rapidly but also to notify health departments early and thereby prevent further poisoning cases. This article reviews several potential food-borne poisons and describes each agent's mechanism of toxicity, expected clinical presentation, and currently accepted treatment.

Hemoperfusion as an Effective Alternative Therapy for Star Fruit Intoxication: A Report of 2 Cases

This report describes 2 cases of star fruit intoxication successfully treated with charcoal hemoperfusion (CHP). Common clinical characteristics of the reported cases included persistent hiccup, consciousness disturbance, coma, need for ventilator support, and admission to an intensive care unit. The optimum treatment for star fruit intoxication has been controversial, with modality, dose, and appropriate timing of extracorporeal therapy debated. Analysis of the 2 reported cases shows several advantages of CHP, including increased extraction efficiency, rapid recovery of consciousness, decreased time of intensive care unit admission, and good clinical tolerance. CHP may provide an alternative treatment modality in cases with life-threatening star fruit intoxication with poor response to intensified hemodialysis.

Electrophysiological effects of the aqueous extract of Averrhoa carambola L. leaves on the guinea pig heart

This work aims to describe some electrophysiological changes promoted by the aqueous extract (AEx) from Averrhoa carambola leaves in guinea pig heart. The experiments were carried out on isolated heart or on right atrium-ventricle preparations. In 6 hearts, the extract induced many kinds of atrioventricular blocks (1st, 2nd, and 3rd degrees); increased the QT interval from 229+/-23 to 264+/-19 ms; increased the QRS complex duration from 27+/-3.1 to 59+/-11 ms, and depressed the cardiac rate from 136+/-17 to 89+/-14b pm. Furthermore, it decreased the conduction velocity of atrial impulse (17+/-3%); reduced the intraventricular pressure (86+/-6%), and increased the conduction time between the right atrium and the His bundle (27+/-6.5%). The conduction time from the His bundle to the right ventricle was not altered. Atropine sulfate did not change either the electrocardiographic parameters or the intraventricular pressure effects promoted by the A. carambola AEx. Based on these results, the popular use of such extracts should be avoided because it can promote electrical and mechanical changes in the normal heart.

Management of Star Fruit—Induced Neurotoxicity and Seizures in a Patient with Chronic Renal Failure

An 84-year-old Asian woman with hypertension and chronic renal failure was evaluated for incoherent speech, followed by intermittent interruptions of consciousness, and then status epilepticus after ingesting one star fruit (Averrhoa carambola) each day for 3 days. Conventional first-line anticonvulsants and hemodialysis were administered without significant control of the patient's seizures. Treatment was started with propofol, an intravenous agent that induces anesthesia with rapid onset and elimination from the central nervous system; this resulted in complete control of the seizures. Propofol may be an effective alternative when dialysis and conventional first-line anticonvulsants are unsuccessful in treating the symptoms of neurotoxicity.

Non-convulsive status epilepticus and consciousness disturbance after star fruit (Averrhoa carambola) ingestion in a dialysis patient

Star fruit ingestion may induce severe neurological complications in chronic renal failure patients. We present a case on maintenance dialysis therapy who developed a consciousness disturbance without convulsion after eating star fruit. The symptoms became aggravated after haemodialysis. The brain computed tomography scan showed no abnormal findings, but the electroencephalogram found active focal sharp waves in the left central regions and diffusion-weighted magnetic resonance imaging also showed hyperintense lesions in the left central regions that were compatible with non-convulsive status epilepticus. His condition improved dramatically after anticonvulsant therapy and regular haemodialysis. The patient was discharged 20 days later without neurological sequela.

Star fruit intoxication in uraemic patients: case series and review of the literature

Star fruit, belonging to the Oxalidaceae family, species Averrhoa carambola, is a popular fruit among Orientals. There have been reports of hiccup, confusion, and occasional fatal outcomes in uraemic patients after ingestion of star fruit. An excitatory neurotoxin from star fruit has been implicated although the exact nature of this toxic substance has not been identified. A group of seven patients is described from the dialysis centres at Queen Mary and Tung Wah Hospitals who developed symptoms including hiccup, confusion, vomiting, impaired consciousness, muscle twitching and hyperkalaemia shortly after ingestion of star fruit. Symptoms of most patients resolved after intensified dialysis or spontaneously, and no mortality was observed. The close temporal relationship of ingestion of star fruit and onset of symptoms strongly suggests the existence of a causal relationship between the two. It is recommended that uraemic patients should totally abstain from star fruit due to these rare but potentially fatal complications. The clinical manifestations of other reported series and current evidence for the possible candidate(s) of the neurotoxin are discussed.