it is characterized by tubular crystalline deposits of calcium oxalate leading to acute and chronic tubular injury , interstitial fibrosis , and progressive renal insufficiency .
a 54-year - old male was seen in our nephrology clinic for progressive increase in his serum creatinine from 1.38 to 3.66 mg / dl over 9 months .
there was no history of fever , diarrhea , steatorrhea , urinary tract symptoms , renal stones , or use of nephrotoxic agents .
his past medical history included hypertension for 15 years , type 2 diabetes for 11 years , obstructive sleep apnea , depression , and treated cellulitis .
he had undergone a duodenal switch procedure for morbid obesity ( body mass index > 50 kg / m ) 20 months earlier .
subsequently , he had lost more than 100 kg of body weight , and there was significant improvement in the control of blood pressure , sleep apnea , and blood sugar .
his serum creatinine was 1.38 mg / dl and urinalysis was normal at the time of surgery .
laboratory investigations showed hemoglobin of 9.9 g / dl , white cell count of 6.9  10/l , blood urea nitrogen of 51.82 mg / dl , and serum creatinine of 3.66 mg / dl .
urinalysis showed 5 - 10 white cells / hpf and 1 - 2 white cell casts without any proteinuria or hematuria .
ultrasound of kidneys showed normal sized kidneys with a few small bilateral calculi without any evidence of obstruction .
the kidney biopsy [ figures 1 and 2 ] demonstrated 13 glomeruli of which six were globally sclerosed .
the tubular interstitial compartment showed foci of tubular damage with deposition of translucent crystals of different shapes which are predominantly intraluminal with few intracellular and focal interstitial distributions . under polarized light
, the deposits appeared strongly birefringent forming fan - like , sheaf - like , or irregular shapes consistent with calcium oxalate crystals .
the immunofluorescence was negative and electron microscopy did not show any electron dense deposits but did reveal tubular damage with intratubular crystal deposition .
his 24-h urinary oxalate level was found to be significantly elevated at 98.7 mg / day ( normal range upto 40 mg / day ) .
large intraluminal translucent crystals of calcium oxalate , tubular epithelial degeneration ( foamy cytoplasm , pyknosis , karyorrhexis , indistinct cell borders , dilated lumina ) , lymphocytic infiltration in the interstitium ( h and e , 400 ) large intraluminal translucent crystals of calcium oxalate , tubular epithelial degeneration , multinucleated foreign body giant cell reaction ( h and e , 400 ) a diagnosis of oxalate nephropathy secondary to enteric hyperoxaluria post - duodenal switch operation was made and he was started on low - oxalate , low - fat diet , with high - fluid intake ( > 3 liters per day ) .
in addition , he was prescribed calcium citrate 1000 mg tid with meals as an oxalate binder .
he was also started on cholestyramine 4 g twice daily and repeat urine oxalate improved markedly to 63 mg / day and his serum creatinine stabilized .
we report a case of oxalate nephropathy occurring in the second - year post - duodenal switch surgery for morbid obesity .
estimates from the national center for health statistics show that the prevalence of obesity in the usa exceeds 30% in most age groups across both genders .
presently , gastric banding , roux - en - y gastric bypass surgery ( rygb ) , and duodenal switch operation are the commonly practiced bariatric surgeries .
there is evidence for significant benefit in terms of improvement in hypertension control diabetes , dyslipidemia , urinary albumin excretion , markers of atherosclerosis , and progression of chronic kidney disease ( ckd ) after weight reduction surgeries .
. with increasing numbers of rygb and duodenal switch operations being performed , the complication of oxalate nephropathy is coming to light .
oxalate nephropathy is progressive in nature and has a poor prognosis . with rygb or duodenal switch surgery
, the patient has an increased absorption of oxalates from colon leading to enteric hyperoxaluria .
the increase in oxalate absorption and subsequent excretion in this setting is related to fat malabsorption leading to unavailability of free calcium for binding oxalate in gut , and unabsorbed bile salt - induced increased colonic permeability to small molecules , such as oxalate . in 2005 , nelson et al .
park et al . measured 24-h urinary collections in 45 patients after bariatric surgery over 2 years and reported that bariatric surgery was almost uniformly associated with increased urinary oxalate and calcium oxalate super saturation .
other important potential factors contributing to nephrolithiasis in this population were decreased urinary volume and decreased urinary citrate . in a large group of 4,639 rygb patients ,
the incidence of nephrolithiasis was 7.7% compared with an incidence of 4.6% in an equally large control group of obese patients who had not undergone an operation .
until now , only a few case reports of oxalate nephropathy have been reported after bariatric surgery . in a mayo clinic series of 60 cases of post - rygb , only two had oxalate nephropathy and both reached end - stage renal disease ( esrd ) .
nasr et al . have reported the largest series of oxalate nephropathy with 11 cases diagnosed post - rygb of which eight reached esrd .
the diagnosis of oxalate nephropathy should be suspected in any patient who presents with sub - acute or chronic renal failure following bariatric surgery .
a 24-h urine collection for oxalate excretion to look for hyperoxaluria and a kidney biopsy is needed for confirming the diagnosis of oxalate nephropathy .
it is not uncommon to find other renal lesions such as hypertensive glomerulosclerosis , diabetic nephropathy , or obesity - associated focal segmental glomerulosclerosis concomitantly due to the co - morbidities of these patients .
a low - fat diet is recommended to reduce the binding of calcium by free fatty acids .
the use of calcium salts to bind oxalate is the mainstay of therapy , though there is little published on the efficacy of this approach .
calcium citrate may be preferable to calcium carbonate as there is almost universally concomitant hypocitraturia .
but the risk of increased aluminum absorption and worsening of bone disease should be kept in mind , especially if the patient has advanced ckd .
cholestyramine may also be helpful as the presence of bile salts in the colon may increase colonic permeability to organic acids such as oxalate .
though bariatric surgeries have significant benefits in terms of mortality and morbidity , it is important that the clinician be aware of post - procedure risk of developing secondary enteric hyperoxaluria , nephrolithiasis , and renal failure due to oxalate nephropathy .
 obesity is a major public health issue all over the world . 
 bariatric surgery is increasingly becoming popular as a surgical treatment for morbid obesity . 
 nephrologists need to be aware of possible renal complications after bariatric surgery . 
 we report a 54-year - old male patient who presented with progressive worsening of renal function following a duodenal switch procedure for morbid obesity , and he was found to have oxalate nephropathy on renal biopsy . 
Introduction
Case Report
Discussion
Conclusion