Nephrolithiasis after bariatric surgery for obesity

Incidence of Symptomatic Cholelithiasis Following Laparoscopic Roux-en-Y Gastric Bypass Is Comparable to Laparoscopic Sleeve Gastrectomy: A Cohort Study

BACKGROUND

A few comparative studies have assessed the incidence of symptomatic cholelithiasis after laparoscopic sleeve gastrectomy (LSG) and laparoscopic Roux-en-Y gastric bypass (LRYGB). However, they have shown inconsistent results. The present study has been designed based on comparing LSG and LRYGB regarding the incidence of symptomatic cholelithiasis and determining factors related to symptomatic cholelithiasis development after these procedures.

METHODS

This retrospective cohort study was conducted on 1163 patients aged ≥ 18 years old who underwent LRYGB (n = 377) or LSG (n = 786) from July 2006 to November 2019. The participants had no previous history of gallstones. A Cox-proportional hazard regression was used to assess associations between the types of procedures and the risk of symptomatic cholelithiasis. The univariable and then multivariable analysis were used to reveal the predictors of symptomatic cholelithiasis.

RESULTS

The mean person-time follow-up was 34 months (95% CI: 32.2 to 36.1 months). The incidence of symptomatic cholelithiasis was 8.3% over the follow-up period. There was no significant association between the risk of symptomatic cholelithiasis development and the type of surgical procedure (HR: 1.35, 95% CI: 0.75 to 2.41). Females had a 2.3-fold higher risk of symptomatic cholelithiasis than males, according to the multivariable Cox regression (HR: 2.31, 95% CI: 1.23 to 4.33). In addition, there was an inverse association between the administration of UDCA and the incidence of symptomatic cholelithiasis (HR: 0.13, 95% CI: 0.01 to 0.99). Our findings indicated that age, baseline body mass index (BMI), percentage of weight loss (%WL) after three and six months following surgery, postoperative pregnancy, and obesity-related comorbidities did not predict the risk of symptomatic cholelithiasis.

CONCLUSION

The present study illustrates no significant differences between LRYGB and LSG regarding symptomatic cholelithiasis occurrence. Our findings indicate that administration of UDCA has a protective effect against symptomatic cholelithiasis while, female gender is the main predictor of symptomatic cholelithiasis.

Jejunal-Ileal Bypass and its Complications: Case Report and Review of the Literature

Herein, we describe an interesting case of a patient who underwent a jejunal-ileal bypass (JIB). She presented to the hospital with gastrointestinal bleeding after which her hospital course was complicated by electrolyte abnormalities. She was a 76-year-old Caucasian female with a past medical history of hypertension, type II diabetes, atrial fibrillation on warfarin, chronic obstructive pulmonary disease (COPD) treated with 3 liters of oxygen at home, obstructive sleep apnea, and morbid obesity, with history of an unknown type of bariatric procedure done in the 1970s. Her upper endoscopy showed a normal esophagus, stomach, and duodenum despite her history of bariatric surgery. Her colonoscopy revealed stenotic terminal ileum and an incidental colonic anastomosis at 35 cm from the anal verge with spot tattoo ink of unknown significance. Also noted were moderate internal hemorrhoids and large external hemorrhoids which were likely the source of her bleeding. Post endoscopy she had marked derangement in electrolytes, specifically hypocalcemia, hypomagnesemia, and hypo-phosphatemia. 

JIB was first popularized in the 1960s for the treatment of obesity. There are two variations of the procedure, colloquially known as the Scott bypass and the Payne bypass. Our patient underwent the Scott JIB. The relatively longer intestinal tract combined with her ileal stenosis may explain her 50 years of relatively stable adaptation. It is imperative that treating physicians have a keen understanding of anatomy and physiology to adequately care for the long-term needs of these patients. 

Nephrolithiasis after bariatric surgery: A comparison of laparoscopic Roux-en-Y gastric bypass and sleeve gastrectomy

INTRODUCTION

Laparoscopic Roux-en-Y gastric bypass (LRYGB) is known to increase risk for calcium oxalate nephrolithiasis due to hyperoxaluria; however, nephrolithiasis rates after laparoscopic sleeve gastrectomy (LSG) are not well described. Our objective was to determine the rate of nephrolithiasis after LRYGB versus LSG.

METHODS

The electronic medical records of patients who underwent LRYGB or LSG between 2001 and 2017 were retrospectively reviewed.

RESULTS

1,802 patients were included. Postoperative nephrolithiasis was observed in 133 (7.4%) patients, overall, and 8.12% of LRYGB (122/1503) vs. 3.68% of LSG (11/299) patients (P < 0.001). Mean time to stone formation was 2.97 ± 2.96 years. Patients with a history of UTI (OR = 2.12, 95%CI 1.41-3.18; P < 0.001) or nephrolithiasis (OR = 8.81, 95%CI 4.93-15.72; P < 0.001) were more likely to have postoperative nephrolithiasis.

CONCLUSION

The overall incidence of symptomatic nephrolithiasis after bariatric surgery was 7.4%. Patients who underwent LRYGB had a higher incidence of nephrolithiasis versus LSG. Patients with a history of stones had the highest risk of postoperative nephrolithiasis.

Ten years of follow-up of bilio-intestinal bypass: is malabsorption necessary for long-term metabolic results?

BACKGROUND

Bilio-intestinal bypass (BIBP) is an uncommon bariatric procedure. In 1999, a prospective trial was started at our institution to evaluate the effectiveness of BIBP. Trial was interrupted in 2006 due to high rate of complications. The aim of the present paper was to retrospectively review 10-year outcomes of BIBP.

METHODS

Retrospective review of bariatric database was performed to find patients that had undergone BIBP from 1999 to 2006. Data collected were as follows: age, gender, body weight, body mass index (BMI), percentage of excess weight loss (%EWL), remission from weight-related diseases, complications, and deaths at 1,3, 5, 7, and 10 years. Quality of life was evaluated using "BAROS" questionnaire.

RESULTS

From May 1999 to September 2006, 86 patients underwent BIBP. The mean age was 34.9 ± 22.4 years, and the initial weight and BMI were 141.2 ± 40.4 kg and 49.8 ± 15.5 kg/m², respectively. After 10 years, the mean %EWL and BMI were 72.6 ± 18.7 and 31.2 ± 5.6 kg/m². Almost all patients had diarrhea after surgery. Bloating syndrome occurred in 24% of patients, 48% had nephrolithiasis, and 20.9% had cholelithiasis. Remission from diabetes and hypertension was obtained in 75% and 80% of patients. Mortality was 3.2% and reoperation rate was 14.5%.

CONCLUSIONS

Malabsorption plays a determinant role to obtain a long-lasting treatment for obese patients. However, BIBP is not recommendable due to high rate of complications and metabolic disorders.

Prospective evaluation of urinary incontinence in severely obese adolescents presenting for weight loss surgery

BACKGROUND

Obesity has been associated with daytime urinary incontinence (UI), likely due to increased intra-abdominal pressure.

OBJECTIVES

To assess incontinence symptoms in severely obese adolescents before and 3 years after bariatric surgery.

SETTING

Tertiary care pediatric hospitals in the United States.

METHODS

The Teen-Longitudinal Assessment of Bariatric Surgery is a prospective, multicenter study designed to evaluate efficacy and safety of bariatric surgery in adolescents. Patients<19 years of age undergoing bariatric surgery at 5 centers between 2007 and 2012 were enrolled. Trained study staff collected baseline and postoperative anthropometric and clinical data. Presence and severity of UI were determined by standardized interview.

RESULTS

A total of 242 patients (76% female) were evaluated at baseline. The mean age was 17.1 years at baseline, and 72% were of white race. The preoperative median body mass index was 50.5 kg/m2. At baseline, 18% of females and 7% of males reported UI. Prediction analysis at baseline indicated that females, white race, and increasing body mass index had greater odds for UI. UI prevalence in females and males decreased to 7% and 0%, respectively, at 6 months after surgery (P<.01) and remained stable out to 36 months postoperatively. Furthermore, older patients were less likely to achieve 3-year UI remission or improvement.

CONCLUSIONS

In adolescents undergoing bariatric surgery, UI was more common in females than in males. Incontinence status significantly improved by 6 months and was durable to 3 years after surgery, suggesting that bariatric surgery favorably affects anatomic or physiologic mechanisms of bladder control in both males and females.

Bariatric Surgery and Kidney-Related Outcomes

The prevalence of severe obesity in both the general and the chronic kidney disease (CKD) populations continues to rise, with more than one-fifth of CKD patients in the United States having a body mass index of ≥35 kg/m². Severe obesity has significant renal consequences, including increased risk of end-stage renal disease (ESRD) and nephrolithiasis. Bariatric surgery represents an effective method for achieving sustained weight loss, and evidence from randomized controlled trials suggests that bariatric surgery is also effective in improving blood pressure, reducing hyperglycemia, and even inducing diabetes remission. There is also observational evidence suggesting that bariatric surgery may diminish the long-term risk of kidney function decline and ESRD. Bariatric surgery appears to be relatively safe in patients with CKD, with postoperative complications only slightly higher than in the general bariatric surgery population. The use of bariatric surgery in patients with CKD might help prevent progression to ESRD or enable selected ESRD patients with severe obesity to become candidates for kidney transplantation. However, there are also renal risks in bariatric surgery, namely, acute kidney injury, nephrolithiasis, and, in rare cases, oxalate nephropathy, particularly in types of surgery involving higher degrees of malabsorption. Although bariatric surgery may improve long-term kidney outcomes, this potential benefit remains unproved and must be balanced with potential adverse events.

Nephrolithiasis after bariatric surgery: A review of pathophysiologic mechanisms and procedural risk

Obesity alone is a known risk factor for nephrolithiasis, and bariatric surgery has been linked to a higher incidence of post-operative new-onset nephrolithiasis. The mean interval from bariatric surgery to diagnosis of nephrolithiasis, ranges from 1.5 to 3.6 years. The stone risk is greatest for purely malabsorptive procedures, intermediate for Roux-en-Y gastric bypass and lowest for purely restrictive procedures (laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy) where it approaches or is reduced below that of non-operative obese controls. A history of nephrolithiasis and increasing age at the time of surgery are both associated with an increased risk of new stone formation post-operatively. The underlying pathophysiologic changes following bariatric surgery include increased colonic absorption of oxalate leading to hyperoxaluria, hypocitraturia and increased urinary calcium oxalate supersaturation, which predispose to stone formation. The majority of incident stones are medically managed, with some requiring interventions in the form of lithotripsy or ureteroscopy.

Nutritional Management of Kidney Stones (Nephrolithiasis)

The incidence of kidney stones is common in the United States and treatments for them are very costly. This review article provides information about epidemiology, mechanism, diagnosis, and pathophysiology of kidney stone formation, and methods for the evaluation of stone risks for new and follow-up patients. Adequate evaluation and management can prevent recurrence of stones. Kidney stone prevention should be individualized in both its medical and dietary management, keeping in mind the specific risks involved for each type of stones. Recognition of these risk factors and development of long-term management strategies for dealing with them are the most effective ways to prevent recurrence of kidney stones.

Biochemical consequences of bariatric surgery for extreme clinical obesity

Obesity, defined as a body mass index over 30 kg/m2 for adults, poses a major healthcare challenge with important economic, personal and social consequences. Although public health measures, lifestyle change and pharmacological therapies have an important role in the management of obesity, patients with established morbid obesity (body mass index over 40 kg/m2) may also require bariatric surgery. Bariatric or metabolic surgery is associated with effective and enduring weight loss but is also known to improve glucose homeostasis, blood pressure and dyslipidaemia. Patients who have bariatric surgery need lifelong clinical follow-up to identify and prevent nutritional deficiencies and other complications. Clinical biochemistry laboratories have an important role in the nutritional assessment of obese patients and in the identification of complications following bariatric surgery. The aim of this article is to review the different bariatric procedures available and to summarize their complications, especially nutrient deficiencies and those of particular relevance to clinical biochemistry laboratories.

Kidney stones are common after bariatric surgery

Obesity, a risk factor for kidney stones and chronic kidney disease (CKD), is effectively treated with bariatric surgery. However, it is unclear whether surgery alters stone or CKD risk. To determine this we studied 762 Olmsted County, Minnesota residents who underwent bariatric surgery and matched them with equally obese control individuals who did not undergo surgery. The majority of bariatric patients underwent standard Roux-en-Y gastric bypass (RYGB; 78%), with the remainder having more malabsorptive procedures (very long limb RYGB or biliopancreatic diversion/duodenal switch; 14%) or restrictive procedures (laparoscopic banding or sleeve gastrectomy; 7%). The mean age was 45 years with 80% being female. The mean preoperative body mass index (BMI) was 46.7 kg/m(2) for both cohorts. Rates of kidney stones were similar between surgery patients and controls at baseline, but new stone formation significantly increased in surgery patients (11.0%) compared with controls (4.3%) during 6.0 years of follow-up. After malabsorptive and standard surgery, the comorbidity-adjusted hazard ratio of incident stones was significantly increased to 4.15 and 2.13, respectively, but was not significantly changed for restrictive surgery. The risk of CKD significantly increased after the malabsorptive procedures (adjusted hazard ratio of 1.96). Thus, while RYGB and malabsorptive procedures are more effective for weight loss, both are associated with increased risk of stones, while malabsorptive procedures also increase CKD risk.

Prospective evaluation of urinary metabolic indices in severely obese adolescents after weight loss surgery

BACKGROUND

Observational studies in obese adults have found abnormal urinary metabolic indices that predispose to nephrolithiasis. Few studies have been performed in severely obese adolescents.

OBJECTIVES

To assess urinary stone risk factors in severely obese adolescents and in those undergoing 2 types of weight loss surgery.

SETTING

Children's hospital, United States.

METHODS

A prospective cross-sectional study was performed to assess urinary metabolic profiles in severely obese adolescents who either have not undergone any gastrointestinal surgery or who have undergone Roux-en-Y gastric bypass (RYGB) or vertical sleeve gastrectomy (SG). Twenty-four-hour urine collections were performed at home and evaluated at a central laboratory. Established normal reference ranges for adults were used in the analysis. A linear regression analysis was performed assessing the relationship of the study group with each of the outcomes.

RESULTS

A total of 55 samples were analyzed from 14 severely obese adolescents and from 17 severely obese adolescents after bariatric surgery (RYGB, 10; SG, 7). Median body mass index was similar between the RYGB and SG groups. The median 24-hour excretion of oxalate was significantly elevated in the RYGB group. Calcium and uric acid excretion and the median supersaturation of calcium oxalate, calcium phosphate, and uric acid were similar among all groups.

CONCLUSIONS

Elevated excretion of oxalate in the urine of severely obese adolescents and in those who have undergone RYGB may portend increased risk for kidney stone formation. Larger longitudinal studies are needed to verify these findings and to determine the clinical risk of developing stone disease in these patient populations.

Enteric hyperoxaluria: an important cause of end-stage kidney disease

Hyperoxaluria is a frequent complication of inflammatory bowel diseases, ileal resection and Roux-en-Y gastric bypass and is well-known to cause nephrolithiasis and nephrocalcinosis. The associated prevalence of chronic kidney disease and end-stage kidney disease (ESKD) is less clear but may be more consequential than recognized. In this review, we highlight three cases of ESKD due to enteric hyperoxaluria following small bowel resections. We review current information on the pathophysiology, complications and treatment of this complex disease.

Obesity, metabolic syndrome and diabetes mellitus after renal transplantation: prevention and treatment

The prevalence of the metabolic syndrome in dialysis patients is high and further increases after transplantation due to weight gain and the detrimental metabolic effects of immunosuppressive drugs. Corticosteroids cause insulin resistance, hyperlipidemia, abnormal glucose metabolism and arterial hypertension. The calcineurin inhibitor tacrolimus is diabetogenic by inhibiting insulin secretion, whereas cyclosporine causes hypertension and increases cholesterol levels. Mtor antagonists are responsible for hyperlipidemia and abnormal glucose metabolism by mechanisms that also implicate insulin resistance. The metabolic syndrome in transplant recipients has numerous detrimental effects such as increasing the risk of new onset diabetes, cardiovascular disease events and patient death. In addition, it has also been linked with accelerated loss of graft function, proteinuria and ultimately graft loss. Prevention and management of the metabolic syndrome are based on increasing physical activity, promotion of weight loss and control of cardiovascular risk factors. Bariatric surgery before or after renal transplantation in patients with body mass index >35 kg/m(2) is an option but its long term effects on graft and patient survival have not been investigated. Steroid withdrawal and replacement of tacrolimus with cyclosporine facilitate control of diabetes, whereas replacement of cyclosporine and mtor antagonists can improve hyperlipidemia. The new costimulation inhibitor belatacept has potent immunosuppressive properties without metabolic adverse effects and will be an important component of immunosuppressive regimens with better metabolic risk profile. Medical treatment of cardiovascular risk factors has to take potential drug interactions with immunosuppressive medication and drug accumulation due to renal insufficiency into account.

Enteric oxalate nephropathy in the renal allograft: an underrecognized complication of bariatric surgery

Enteric hyperoxalosis is a recognized complication of bariatric surgery, with consequent oxalate nephropathy leading to chronic kidney disease and occasionally end-stage renal failure. In patients with prior gastrointestinal bypass surgery, renal allografts are also at risk of oxalate nephropathy. Further, transplant recipients may be exposed to additional causes of hyperoxalosis. We report two cases of renal allograft oxalate nephropathy in patients with remote histories of bariatric surgery. Conservative management led to improvement of graft function in one patient, while the other patient returned to dialysis. Interpretation of serologic, urine and biopsy studies is complicated by oxalate accumulation in chronic renal failure, and heightened excretion in the early posttransplant period. A high index of suspicion and careful clinicopathologic correlation on the part of transplant nephrologists and renal pathologists are required to recognize and treat allograft oxalate nephropathy. As the incidence of obesity and pretransplant bariatric surgery increases in the transplant population, allograft oxalate nephropathy is likely to be an increasing cause of allograft dysfunction.

Impact of stone disease: chronic kidney disease and quality of life

This article reviews the impact of stone disease on chronic kidney disease and renal function; evaluating the natural progression of disease as well as the impact of surgical interventions. The impact of stone disease, medical therapy, and surgical therapy for stones on quality of life is discussed.

Subclinical celiac disease and crystal-induced kidney disease following kidney transplant

Decreased kidney function from kidney deposition of calcium oxalate has been described previously in inflammatory bowel disease and after jejuno-ileal and Roux-en-Y gastric bypass surgeries. Although celiac disease is the most prevalent bowel abnormality associated with intestinal malabsorption, its relationship to high kidney oxalate burden and decreased kidney function has not been established. We report a case of subclinical celiac disease and hyperoxaluria that presented with loss of kidney function as a result of high oxalate load in the absence of overt diarrhea, documented intestinal fat malabsorption, and nephrolithiasis. Subclinical celiac disease is commonly overlooked and hyperoxaluria is not usually investigated in kidney patients. We propose that this entity should be suspected in patients with chronic kidney disease in which the cause of kidney damage has not been clearly established.

The impact of renal function on outcomes of bariatric surgery

The effect of CKD on the risks of bariatric surgery is not well understood. Using the American College of Surgeons National Surgical Quality Improvement Program Participant Use File, we analyzed 27,736 patients who underwent bariatric surgery from 2006 through 2008. Before surgery, 34 (0.12%) patients were undergoing long-term dialysis. Among those not undergoing dialysis, 20,806 patients (75.0%) had a normal estimated GFR or stage 1 CKD, 5011 (18.07%) had stage 2 CKD, 1734 (6.25%) had stage 3 CKD, 94 (0.34%) had stage 4 CKD, and 91 (0.33%) had stage 5 CKD. In an unadjusted analysis, CKD stage was directly associated with complication rate, ranging from 4.6% for those with stage 1 CKD or normal estimated GFR to 9.9% for those with stage 5 CKD (test for trend, P<0.001). Multivariable logistic regression demonstrated that CKD stage predicts higher complication rates (odds ratio for each higher CKD stage, 1.30) after adjustment for diabetes and hypertension. Although patients with higher CKD stage had higher complication rates, the absolute incidence of complications remained <10%. In conclusion, these data demonstrate higher risks of bariatric surgery among patients with worse renal function, but whether the potential benefits outweigh the risks in this population requires further study.

Hyperoxaluria: a gut-kidney axis?

Hyperoxaluria leads to urinary calcium oxalate (CaOx) supersaturation, resulting in the formation and retention of CaOx crystals in renal tissue. CaOx crystals may contribute to the formation of diffuse renal calcifications (nephrocalcinosis) or stones (nephrolithiasis). When the innate renal defense mechanisms are suppressed, injury and progressive inflammation caused by these CaOx crystals, together with secondary complications such as tubular obstruction, may lead to decreased renal function and in severe cases to end-stage renal failure. For decades, research on nephrocalcinosis and nephrolithiasis mainly focused on both the physicochemistry of crystal formation and the cell biology of crystal retention. Although both have been characterized quite well, the mechanisms involved in establishing urinary supersaturation in vivo are insufficiently understood, particularly with respect to oxalate. Therefore, current therapeutic strategies often fail in their compliance or effectiveness, and CaOx stone recurrence is still common. As the etiology of hyperoxaluria is diverse, a good understanding of how oxalate is absorbed and transported throughout the body, together with a better insight in the regulatory mechanisms, is crucial in the setting of future treatment strategies of this disorder. In this review, the currently known mechanisms of oxalate handling in relevant organs will be discussed in relation to the different etiologies of hyperoxaluria. Furthermore, future directions in the treatment of hyperoxaluria will be covered.

Bariatric surgery and renal function

Obesity causes a significant healthcare burden and has been shown to be an important risk factor in the development of cardiovascular disease, type 2 diabetes, and increasingly chronic kidney disease. Bariatric surgery is the most effective treatment for obesity and has been shown to drastically improve both blood pressure and diabetic control. However, the interaction of bariatric surgery and renal function is less clear. This review focuses on the effect of bariatric surgery on renal function both in the acute situation, with respect to acute kidney injury, and also on changes in renal function parameters post-bariatric surgery weight loss. The interaction of obesity, bariatric surgery, and nephrolithiasis as a precipitant of acute kidney injury will also be considered. The role of bariatric surgery in pre- and post-renal transplant recipients is discussed as well as possible mechanisms underlying the improvement in renal function.

Fat malabsorption and increased intestinal oxalate absorption are common after Roux-en-Y gastric bypass surgery

BACKGROUND

Hyperoxaluria and increased calcium oxalate stone formation occur after Roux-en-Y gastric bypass (RYGB) surgery for morbid obesity. The etiology of this hyperoxaluria is unknown. We hypothesized that after bariatric surgery, intestinal hyperabsorption of oxalate contributes to increases in plasma oxalate and urinary calcium oxalate supersaturation.

METHODS

We prospectively examined oxalate metabolism in 11 morbidly obese subjects before and 6 and 12 months after RYGB (n = 9) and biliopancreatic diversion-duodenal switch (BPD-DS) (n = 2). We measured 24-hour urinary supersaturations for calcium oxalate, apatite, brushite, uric acid, and sodium urate; fasting plasma oxalate; 72-hour fecal fat; and increases in urine oxalate following an oral oxalate load.

RESULTS

Six and 12 months after RYGB, plasma oxalate and urine calcium oxalate supersaturation increased significantly compared with similar measurements obtained before surgery (all P ≤ .02). Fecal fat excretion at 6 and 12 months was increased (P = .026 and .055, 0 vs 6 and 12 months). An increase in urine oxalate excretion after an oral dose of oxalate was observed at 6 and 12 months (all P ≤ .02). Therefore, after bariatric surgery, increases in fecal fat excretion, urinary oxalate excretion after an oral oxalate load, plasma oxalate, and urinary calcium oxalate supersaturation values were observed.

CONCLUSION

Enteric hyperoxaluria is often present in patients after the operations of RYGB and BPD-DS that utilize an element of intestinal malabsorption as a mechanism for weight loss.

[Bariatric surgery, calcium oxalate urinary stones and oxalate nephropathy]

Bariatric surgery is now recognized as a sure and effective way for weight reduction in morbid obesity. However some procedures induce intestinal malabsorption leading to enteric hyperoxaluria. So bariatric surgery could place these patients not only at risk for nephrolithiasis but also for oxalate induced nephropathy and chronic renal failure. Because of the growing incidence of obesity worldwide, physicians and patients should be aware of such potential complications. There is no mean to discuss this treatment because of its spectacular efficiency on obesity and its comorbidities. But it is necessary to choose the surgical technique according to the risk factors of the patients. Following surgery, preventive treatment strategies are indicated, such as modified dietary lifestyle and specific drugs as we suggested to limit or even avoid these complications. However observance could fail in the long term. In case of oxalate nephropathy, surgery may be proposed to restore the intestinal tract but with the risk of overweight relapse. To illustrate this matter, we report here significant observations of three patients, which, having successfully benefited from the same bariatric surgery, have presented lithiasic complications for two of them and oxalate nephropathy leading to chronic renal failure and hemodialysis for the third.

Primary care of the renal transplant patient

There has been a remarkable rise in the number of kidney transplant recipients (KTR) in the US over the last decade. Increasing use of potent immunosuppressants, which are also potentially diabetogenic and atherogenic, can result in worsening of pre-existing medical conditions as well as development of post-transplant disease. This, coupled with improving long-term survival, is putting tremendous pressure on transplant centers that were not designed to deliver primary care to KTR. Thus, increasing numbers of KTR will present to their primary care physicians (PCP) post-transplant for routine medical care. Similar to native chronic kidney disease patients, KTRs are vulnerable to cardiovascular disease as well as a host of other problems including bone disease, infections and malignancies. Deaths related to complications of cardiovascular disease and malignancies account for 60-65% of long-term mortality among KTRs. Guidelines from the National Kidney Foundation and the European Best Practice Guidelines Expert Group on the management of hypertension, dyslipidemia, smoking, diabetes and bone disease should be incorporated into the long-term care plan of the KTR to improve outcomes. A number of transplant centers do not supply PCPs with protocols and guidelines, making the task of the PCP more difficult. Despite this, PCPs are expected to continue to provide general preventive medicine, vaccinations and management of chronic medical problems. In this narrative review, we examine the common medical problems seen in KTR from the PCP's perspective. Medical management issues related to immunosuppressive medications are also briefly discussed.

The Medical Management of Urolithiasis

Urolithiasis is increasing in prevalence and causes substantial morbidity and economic burden. Aside from “acute” stone episodes, urolithiasis should be regarded as a systemic disorder and investigated fully. Practical guidance is given for the medical investigation, diagnosis and treatment of urolithiasis. A single episode of urolithiasis should prompt a review of potential risk factors for recurrent disease and appropriate baseline investigations should be performed. Further biochemical tests may then be directed appropriately and allow individualised advice and treatment to be given to the patient with urolithiasis.

Diabetes and obesity: therapeutic targeting and risk reduction - a complex interplay

Obesity is a major risk factor for the development of diabetes and predisposes individuals to hypertension and dyslipidaemia. Together these pathologies increase the risk for cardiovascular disease (CVD), the major cause of morbidity and mortality in type 2 diabetes mellitus (T2DM). Worsening trends in obesity and T2DM raise a serious conundrum, namely, how to control blood glucose, blood pressure, and lipids when many antidiabetic agents cause weight gain and thereby exacerbate other cardiovascular risk factors associated with T2DM. Further, evidence suggests that some established antihypertensive agents may worsen glucose intolerance. Many patients who are obese, hypertensive, and/or hyperlipidaemic fail to achieve blood pressure, lipid and glycaemic goals, and this failure may in part be explained by physician reluctance to utilize complex combination regimens for fear of off-target effects. Thus, a clear need exists for clinicians to understand the risks and benefits of different pharmacologic, and indeed non-pharmacologic, options in order to maximize treatment outcomes. While intensive lifestyle modification remains an elusive gold standard, newer diabetes targets, including the incretin axis, may offer greater cardiovascular risk reduction than other antidiabetes therapies, although definitive clinical trial data are needed. The glucagon-like peptide-1 (GLP-1) receptor agonists exenatide and liraglutide and the dipeptidyl peptidase-4 (DPP-4) inhibitors sitagliptin and vildagliptin effectively lower HbA1c; exenatide and liraglutide reduce weight and blood pressure and improve lipid profiles. Sitagliptin and vildagliptin are weight neutral but also appear to improve lipid profiles. Integration of incretin therapies into the therapeutic armamentarium is a promising approach to improving outcomes in T2DM, and perhaps even in reducing complications of T2DM, such as co-morbid hypertension and dyslipidaemia. Additional long-term studies, including CVD end-point studies, will be necessary to determine the appropriate places for incretin-based therapies in treatment algorithms.

Hypocitraturia and hyperoxaluria after Roux-en-Y gastric bypass surgery

PURPOSE

Roux-en-Y gastric bypass surgery is associated with an increased risk of nephrolithiasis but obesity itself is a known risk factor for kidney stones. To assess the mechanism(s) predisposing to nephrolithiasis after Roux-en-Y gastric bypass we compared urinary tract stone risk profiles in patients who underwent the procedure and normal obese individuals.

MATERIALS AND METHODS

In this cross-sectional study urine and serum biochemistry was evaluated in 19 nonstone forming patients after Roux-en-Y gastric bypass and in 19 gender, age and body mass index matched obese controls without a history of nephrolithiasis.

RESULTS

Compared with obese controls surgical patients had significantly higher mean +/- SD urine oxalate (45 +/- 21 vs 30 +/- 11 mg daily, p = 0.01) and lower urine citrate (358 +/- 357 vs 767 +/- 307 mg daily, p <0.01). The prevalence of hyperoxaluria (47% vs 10.5%, p = 0.02) and hypocitraturia (63% vs 5%, p <0.01) was significantly higher in surgical patients, who also had significantly lower urine calcium than obese controls (115 +/- 93 vs 196 +/- 123 mg daily, p = 0.03). The calcium oxalate urine relative supersaturation ratio was not significantly different between the 2 groups.

CONCLUSIONS

Almost half of patients with Roux-en-Y gastric bypass without a history of nephrolithiasis showed hyperoxaluria or hypocitraturia. This prevalence was significantly higher than in body mass index matched controls. These risk factors were negated by lower urine calcium excretion in patients with Roux-en-Y gastric bypass.

Gastric band placement for obesity is not associated with increased urinary risk of urolithiasis compared to bypass

PURPOSE

Obesity is associated with multiple health risks. Bariatric surgery is a treatment for clinically severe obesity and is known to increase urolithiasis risk. However, trends in risk over time are not well characterized. Moreover little attention has been devoted to laparoscopic gastric band placement. A comparison of urinary risk of urolithiasis after the Roux-en-Y and gastric banding procedures was performed.

MATERIALS AND METHODS

We evaluated 24-hour urine collections from 39 subjects (11 male and 28 female, mean age 51 years) after bariatric surgery. Of these subjects 27 underwent Roux-en-Y gastric bypass and 12 had gastric banding procedures. Mean time since surgery was 3.4 and 2.1 years for the Roux-en-Y gastric bypass and gastric banding groups, respectively.

RESULTS

Urine volume was low in both groups (less than 1.5 l daily). Urinary calcium excretion was lower (p = 0.001) in the Roux-en-Y gastric bypass (100 mg daily) vs the gastric banding group (191 mg daily). After Roux-en-Y gastric bypass surgery 48% had a urinary oxalate of 45 mg daily or more compared to 25% after gastric banding. Urinary citrate was less than 370 mg daily for 14 subjects in the Roux-en-Y gastric bypass and 1 in the gastric banding group. All patients were taking calcium supplements. Dietary intake of high oxalate foods did not correlate with urinary oxalate excretion or with hyperoxaluria.

CONCLUSIONS

Our study confirms the risk of urinary stones following the Roux-en-Y gastric bypass procedure as a result of hyperoxaluria, low urine volume and hypocitraturia. Those with gastric banding placement had low urine volumes. Future studies should elucidate the effect of nutrition and/or pharmacological therapy on stone risk of both surgeries as their incidence increases.

The effect of gastric banding on kidney stone disease

OBJECTIVES

To evaluate the likelihood of being diagnosed with, or treated for, an upper urinary tract calculus after gastric banding. Bariatric surgical procedures are being increasingly utilized in the treatment of patients with morbid obesity. Certain malabsorptive bariatric procedures have been associated with an increased risk for kidney stone formation. However, the kidney stone risk of gastric banding, a restrictive bariatric procedure, is unknown.

METHODS

We identified 201 patients who underwent gastric banding and a control group of 201 obese patients who did not have bariatric surgery in a national private insurance claims database within a 5-year period from 2002-2006. All patients had at least 2 years of continuous claims data follow-up. Our 2 primary outcomes were the diagnosis and the surgical treatment of a urinary calculus.

RESULTS

After gastric banding, the diagnosis of an upper urinary tract calculus occurred in 3 subjects (1.49%), as compared with 12 subjects (5.97%) in the comparison cohort (P = .0179). One subject in each cohort (0.50%) underwent a surgical procedure for the treatment of an upper urinary tract (P = 1.0000).

CONCLUSIONS

Gastric banding is not associated with an increased risk for kidney stone disease or kidney stone surgery in the postoperative period. Additional long-term studies are required to confirm these findings.

Prospects for dietary therapy of recurrent nephrolithiasis

The goal of this article is to propose a randomized controlled trial (RCT) that tests a hypothesis that dietary manipulation prevents recurrent kidney stones. Dietary interventions based on epidemiologic and pathophysiologic data are reviewed. The only diet trial successful in preventing stones showed that calcium intake of 1,200 mg/d, accompanied by restriction of animal protein, salt, and oxalate ingestion, was superior to 400 mg of calcium and restricted oxalate intake. This study may be worth repeating in women and in a society in which salt restriction might be less effective (eg, United States). The net result of diet trials establishes significant positive effects on urine chemistries, but these have not yet shown efficacy with regard to stone recurrence. Oxalate restriction alone could be effective, but many questions regarding which populations to study are not defined, and dietary oxalate's contribution to stone formation is disputed. Would such a study be limited to patients identified as having high dietary oxalate intake or high intestinal oxalate absorption? Would colonization with Oxalobacter formigenes influence the result? The increased prevalence of stones is linked to weight gain and obesity, making weight loss a possible therapy to prevent stones. Randomized trials show that diets consisting of low-fat content or low-caloric content cause modest weight loss and might be effective in reducing stone formation. Because the efficacy of thiazides in the prevention of stones in patients with hypercalciuria is clear, I propose dietary comparison of higher calcium intake to thiazides for the prevention of calcium-based kidney stones.

Oxalate nephropathy complicating Roux-en-Y Gastric Bypass: an underrecognized cause of irreversible renal failure

BACKGROUND AND OBJECTIVES

The most common bariatric surgery is Roux-en-Y gastric bypass (RYGB), which has been associated with hyperoxaluria and nephrolithiasis. We report a novel association of RYGB with renal insufficiency as a result of oxalate nephropathy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Eleven cases of oxalate nephropathy after RYGB were identified from the Renal Pathology Laboratory of Columbia University. The clinical features, pathologic findings, and outcomes are described.

RESULTS

Patients were predominantly white (72.7%) with a mean age of 61.3 yr. Indications for RYGB included morbid obesity (eight patients) and reconstruction after total gastrectomy for gastric cancer (three patients). All 11 patients had a history of hypertension, and 9 were diabetic. Patients presented with acute renal failure, often superimposed on mild chronic renal insufficiency (n = 7), at a median of 12 mo after RYGB. The mean creatinine at baseline, at discovery of acute renal failure, and at biopsy was 1.5, 5.0, and 6.5 mg/dl, respectively. Renal biopsies revealed diffuse tubular degenerative changes, abundant tubular calcium oxalate deposits, and varying degrees of tubulointerstitial scarring. In addition, seven biopsies had underlying diabetic glomerulosclerosis and two had glomerulosclerosis attributable to obesity and hypertension. Eight of 11 patients rapidly progressed to ESRD and required hemodialysis at a mean of 3.2 wk after renal biopsy. The remaining three patients were left with significant chronic kidney disease.

CONCLUSIONS

Oxalate nephropathy is an underrecognized complication of RYGB and typically results in rapid progression to ESRD. Patients with pre-existing renal disease may be at higher risk for this complication.