acute oxalate nephropathy ( aon ) in cases of secondary oxalosis is the result of excessive oxalate accumulation because of increased ingestion , increased production , or decreased excretion of oxalate . the kidney is the primary organ for oxalate excretion and increased oxalate load may result in renal insufficiency . increased dietary intake of oxalate is fairly uncommon ; however , there have been case reports in the literature describing excessive intake of star fruit ( averrhoa carambola ) juice and peanut intake leading to oxalate nephropathy . irumban puli ( averrhoa bilimbi ) is a local fruit in south india which has high oxalic acid content . excessive ingestion of fruit juice can lead to increased serum oxalate level which can cause deposition of calcium oxalate crystals in renal tubules and cause acute renal failure ( arf ) . we present a series of cases from five hospitals in the state of kerala who developed arf due to aon after consumption of i. puli juice . a 38-year - old man , who was working abroad and came to india on a vacation , underwent a health check up , which showed normal renal functions and hypercholesterolemia . he consumed a glass of i. puli fruit juice daily for 4 days for control of hypercholesterolemia . after 4 days , the patient developed abdominal discomfort , nausea , and loss of appetite . he presented to our center with the above - mentioned symptoms ; he had normal urine output . on examination , the patient was conscious , oriented , blood pressure 150/90 mmhg ; he had no edema , and his systems were normal . investigations showed severe renal failure with serum creatinine of 6.4 mg / dl , with normal hemogram and liver function tests ; urine analysis showed no albuminuria , and microscopy showed oxalate crystals . the patient underwent two sessions of hemodialysis , following which a left percutaneous kidney biopsy was done . kidney biopsy showed acute tubular necrosis with many polarizable fractured crystals in the tubular lumina ( calcium oxalate crystals ) [ figure 1a and b ] . the oxalate content of the fruit was 25.1 mg per 100 g of the fruit , when analyzed in our lab by spectrophotometry method . his renal functions improved to normal in 6 weeks ( serum creatinine : 0.9 mg / dl ) . ( a ) renal tubules showing features of acute tubular necrosis with fractured crystals in the lumen ( lm : h and e , 40 ) , tubules with necrosis ( bold arrow ) , intratubular fractured crystals ( thin arrow ) ; ( b ) calcium oxalate crystals under polarized light ( arrow ) ; ( c ) urine microscopy showing calcium oxalate crystals ( envelope - shaped ) a 57-year - old man , known to have type 2 diabetes mellitus ( on diet control ) and dyslipidemia ( on statins ) presented to us with a history of anorexia , nausea , and fatigue for 2 weeks after intake of i. puli fruit juice for 5 days ; he was oliguric . he had a normal hemogram , with serum creatinine : 9.3 mg / dl , serum cholesterol : 180 mg / dl . urine analysis showed 1 + protein , and microscopic examination of the urine sample showed plenty of oxalate crystals . he was initiated on hemodialysis and subsequently underwent a left percutaneous kidney biopsy which showed acute tubular necrosis with intra tubular calcium oxalate crystals . eight out of 10 patients had plenty of oxalate crystals in urine ; all the patients had severe renal failure with serum creatinine ranging from 5.5 to 12.3 mg / dl . seven patients required hemodialysis in view of severe renal failure ; the remaining three patients were treated conservatively and renal functions returned to normal . all the patients showed acute tubular necrosis with polarizable tubular crystals consistent with oxalate crystals [ figure 1 ] . the time taken for serum creatinine to reach the normal level ranged from 2 to 6 weeks . a 38-year - old man , who was working abroad and came to india on a vacation , underwent a health check up , which showed normal renal functions and hypercholesterolemia . he consumed a glass of i. puli fruit juice daily for 4 days for control of hypercholesterolemia . after 4 days , the patient developed abdominal discomfort , nausea , and loss of appetite . he presented to our center with the above - mentioned symptoms ; he had normal urine output . on examination , the patient was conscious , oriented , blood pressure 150/90 mmhg ; he had no edema , and his systems were normal . investigations showed severe renal failure with serum creatinine of 6.4 mg / dl , with normal hemogram and liver function tests ; urine analysis showed no albuminuria , and microscopy showed oxalate crystals . the patient underwent two sessions of hemodialysis , following which a left percutaneous kidney biopsy was done . kidney biopsy showed acute tubular necrosis with many polarizable fractured crystals in the tubular lumina ( calcium oxalate crystals ) [ figure 1a and b ] . the oxalate content of the fruit was 25.1 mg per 100 g of the fruit , when analyzed in our lab by spectrophotometry method . his renal functions improved to normal in 6 weeks ( serum creatinine : 0.9 mg / dl ) . ( a ) renal tubules showing features of acute tubular necrosis with fractured crystals in the lumen ( lm : h and e , 40 ) , tubules with necrosis ( bold arrow ) , intratubular fractured crystals ( thin arrow ) ; ( b ) calcium oxalate crystals under polarized light ( arrow ) ; ( c ) urine microscopy showing calcium oxalate crystals ( envelope - shaped ) a 57-year - old man , known to have type 2 diabetes mellitus ( on diet control ) and dyslipidemia ( on statins ) presented to us with a history of anorexia , nausea , and fatigue for 2 weeks after intake of i. puli fruit juice for 5 days ; he was oliguric . he had a normal hemogram , with serum creatinine : 9.3 mg / dl , serum cholesterol : 180 mg / dl . urine analysis showed 1 + protein , and microscopic examination of the urine sample showed plenty of oxalate crystals . he was initiated on hemodialysis and subsequently underwent a left percutaneous kidney biopsy which showed acute tubular necrosis with intra tubular calcium oxalate crystals . eight out of 10 patients had plenty of oxalate crystals in urine ; all the patients had severe renal failure with serum creatinine ranging from 5.5 to 12.3 mg / dl . seven patients required hemodialysis in view of severe renal failure ; the remaining three patients were treated conservatively and renal functions returned to normal . all the patients showed acute tubular necrosis with polarizable tubular crystals consistent with oxalate crystals [ figure 1 ] . the time taken for serum creatinine to reach the normal level ranged from 2 to 6 weeks . arf can occur as a result of acute oxalate nephropathy due to the deposition of calcium oxalate crystals within the renal tubules . primary hyperoxaluria is a group of autosomal recessively inherited enzyme deficiencies that lead to the increased urinary excretion of oxalate . in type 1 primary hyperoxaluria , there is a reduction of alanine glyoxylate aminotransferase activity in the liver , leading to an accumulation of oxalate . type 2 primary hyperoxaluria occurs due to a mutation of glyoxylate reductase / d - glycerate dehydrogenase , leading to the excretion of increased amounts of l - glyceric acid as well as oxalate . secondary hyperoxaluria can occur due to increased dietary intake of oxalate , increased absorption of oxalate from the bowel ( also known as enteric hyperoxaluria ) , and increased production of oxalate . enteric hyperoxaluria results mainly from fat malabsorption , which leads to increased absorption of soluble oxalate from the colon . this reduces the normal calcium oxalate precipitation in the feces , thereby allowing the absorption of soluble oxalate from the gut . enteric hyperoxaluria occurs in orlistat therapy , roux - en - y gastric bypass surgery , celiac disease , and crohn 's disease . increased production of oxalate is mainly due to increased levels of oxalate precursors , more commonly glyoxylate , which is associated with ethylene glycol ingestion , and less commonly ascorbic acid . a. bilimbi ( commonly known as bilimbi , i. puli , chemmeen puli , bimbul ) is a fruit - bearing tree of the genus averrhoa , family oxalidaceae . the fruits are fairly cylindrical with five broad rounded longitudinal lobes , and are produced in clusters [ figure 2 ] . a. bilimbi fruits are very sour , and are used in the production of vinegar , wine , pickles , jams , and jellies and in the preparation of south indian dishes . averrhoa bilimbi tree with fruits a. bilimbi had been advocated for the treatment of hyperlipidemia , hypertension , and diabetes by different communities . in indonesia , the fruit is used to treat hypertension and the decoction of the leaves is used for the management of diabetes . in india , the leaves , flowers , and fruits have been used by some communities to treat hypercholesterolemia , hypertension , and diabetes . in rats the fruit is also used to treat tinea versicolor , beri - beri , cough , mumps , rheumatism , and scurvy . the high levels of oxalic acid found in bilimbi are probably responsible for its extremely low ph ( 0.9 - 1.5 ) . the oxalate content of the fruit was found to be 25.1 mg/100 g of fruit when analyzed in our lab ; this is very high compared to other fruits [ table 2 ] . oxalate content of various fruits various renal and neurological side effects like muscle weakness , intractable hiccups , mental confusion , seizures after ingestion of star fruit ( a. carambola ) have been documented . a. bilimbi , which belongs to the same family , causing acute tubular necrosis due to high oxalate content has not been described before . oxalic acid has a direct toxic effect on the renal tubules and interstitium , facilitates the development of oxalate crystals which are endocytosed by renal epithelial cells and promote a proliferative response . these crystals also stimulate specific genes in renal tubular cells , including the connective tissue growth factor gene leading to interstitial fibrosis . i. puli ( a. bilimbi ) is a traditional ingredient of various south indian dishes , and is also used in various other south east asian countries as a local remedy for various ailments like hypertension , diabetes , and dyslipidemia . when used in high concentrations , the fruit juice can lead to arf due to acute tubular necrosis , owing to its high oxalate content , which results in intratubular oxalate crystal deposition . we conclude that it is not safe to consume high oxalate - containing fruits in large quantities .
irumban puli ( averrhoa bilimbi ) is commonly used as a traditional remedy in the state of kerala . 
 freshly made concentrated juice has a very high oxalic acid content and consumption carries a high risk of developing acute renal failure ( arf ) by deposition of calcium oxalate crystals in renal tubules . 
 acute oxalate nephropathy ( aon ) due to secondary oxalosis after consumption of irumban puli juice is uncommon . 
 aon due to a. bilimbi has not been reported before . 
 we present a series of ten patients from five hospitals in the state of kerala who developed arf after intake of i. puli fruit juice . 
 seven patients needed hemodialysis whereas the other three improved with conservative management .