Surgical Weight Loss Considerations and Nutritional Implications for Patients with Renal Disease

| May 17, 2011 | 0 Comments

by Linda Bartholomay, BS, RD, LRD

Ms. Bartholomay is Manager of Outpatient Nutrition Therapy, Sanford Health, Fargo, North Dakota.

Financial disclosure: Ms. Bartholomay reports no conflicts of interest relevant to the content of this article.
Bariatric Times. 2011;8(5):8–13

Weight loss surgery has demonstrated effectiveness for the treatment of diabetes, obesity, and hypertension; all of which are noted to be primary causes of chronic kidney disease and eventual end stage renal disease. Weight loss can help limit the progression or resolve chronic kidney disease. As the number of patients in the United States with chronic kidney disease and end stage renal disease increases, weight loss surgery is becoming more recognized as a treatment option either to help deminish progression of chronic kidney disease or to prepare for kidney transplant if weight loss is needed to qualify for transplant candidacy. This article presents some unique considerations for renal patients with the various weight loss procedures; both on nutrition status and potential vitamin/mineral deficiencies or excesses. Monitoring lab values are also recommended to help determine optimal vitamin/mineral supplementation before and after surgery.

Weight loss surgery has shown benefits to many chronic diseases, such as diabetes, hypertension, lipid abnormalities, and also to chronic kidney disease (CKD). But is weight loss surgery for those with end-stage renal disease (ESRD) a good option? That was my question when I first saw a patient in the clinic who was on dialysis, but was seeking gastric bypass to lose weight to be able to have a kidney transplant. What would happen after surgery? How would we modify her diet and supplements after surgery?

According to data from The National Health and Nutrition Examination Survey (NHANES) from 1999 to 2004, the prevalence of chronic kidney disease was 16.8 percent in the United States. Not treated or inadequately treated, CKD can necessitate eventual dialysis or transplantation. Primary causes of CKD are noted to be diabetes, hypertension, and obesity.[1] With the rate of diabetes and obesity in this country increasing, it is not likely that that we will run out of patients with CKD anytime soon.

Healthcare Cost—benefits versus risks
Treating ESRD is costly. As of the end of 2007, the cost of treating patients with ESRD amounted to $35.32 billion annually from both public and private spending. In 2006, the average annual cost for a Medicare ESRD patient on dialysis was $43,335.[2]

Consider the potential annual healthcare cost savings if fewer patients required dialysis.

Additionally, kidney transplantation for those approaching dialysis or already on dialysis would certainly improve quality of life. Transplant numbers are also increasing each year. From 2005 to 2007, there were 53,012 kidney transplants performed in the United States.3 This represents a 20-percent increase from 2000 and a 45-percent increase from 1995.

Transplant recipients without obesity tend to have better outcomes, such as improved patient and graft survival, compared to patients with obesity. So, potential recipients need to lose weight to meet the standard of body mass index (BMI) of 35kg/m2 or less. Is weight loss surgery a safe and cost-effective way to reach the desired BMI?[4,5]

Weight loss surgery costs are actually decreasing due to efficiencies and improved outcomes. One study, which examined hospital payments for bariatric surgery procedures, found that payments fell from $29,563 to $27,905 from 2002 to 2006. In addition, complication rates have dropped during this same time, despite the fact that patients having the procedures were older and sicker.[6]

For patients with CKD, weight loss has been shown to improve renal parameters.[7] In a study done by the University of Cincinnati College of Medicine,[8] nine out of 45 patients with established renal disease, had resolution, improvement, or stabilization of kidney function after gastric bypass. Two patients already on dialysis at the time of surgery were able to discontinue dialysis for 27 and seven months, respectively. The remaining patients had stable renal function for 2 to 5 years postoperatively. Weight loss surgery, thus, can decrease overall healthcare costs by delaying the progression of disease or delaying the need for dialysis or kidney transplantation.[8] More long-term studies are needed to analyze effects of bariatric surgery on CKD and progression to ESRD.[9]

Weight loss surgery in patients with renal disease does carry some risks.[10] One must consider the potential for malabsorption of not only nutrients, but also antirejection medications.[11] For patients who are undergoing dialysis, there are no studies that have looked at the optimal vitamin/mineral supplementation plan for patients with ESRD following bariatric surgery.

Types of surgery
The type of surgical procedure done is also an important factor to consider. Laparoscopic adjustable gastric banding (LAGB) is a restrictive, but not malabsorptive procedure. Laparoscopic Roux-en-Y gastric bypass (RYGB) is both a restrictive and malabsorptive procedure. Newer on the playing field, laparoscopic sleeve gastrectomy (LSG), is also promoted as a restrictive procedure without malabsorption effects.
Roux-en-Y gastric bypass. Roux-en-Y gastric bypass (RYGB) surgery has the advantage of established long-term efficacy for weight loss and reductions of obesity-related comorbities (i.e., type 2 diabetes mellitus, lipid abnormalities, and hypertension). It is relatively safe, and weight loss results are reported typically as a loss of 60 to 80 percent of excess body weight (EBW). It combines elements of restrictive, hormonal, and malabsorptive procedures.[12] Maximum weight loss with RYGB is usually achieved by 12 to 18 months following surgery.[13]

Laparoscopic adjustable gastric banding. Laparoscopic adjustable gastric banding (LAGB) has been around for a number of years in other countries. It was approved for use in the United States in 2001. It is strictly a restrictive procedure. Weight loss is generally slower than gastric bypass (an average of 2 pounds per week) and yields a decrease of approximately 44 to 68 percent of EBW at four years.[13] Adjustments of the band require more office visits after surgery (around 10 in the first year) and an annual upper gastrointestinal test. Band slippage is a risk that can be serious  and may even require a second surgery for gastrectomy or conversion to RYGB. The gastric banding option for kidney transplant patients is questionable due to the presumed predisposition to infection presented by a foreign body (i.e., the band) in immunosuppressed patients after transplant.[14]

Laparoscopic sleeve gastrectomy. LSG combines restrictive and hormonal components. It is a newer procedure and is not universally covered by third-party payers (including Medicare). The sleeve was previously reserved as the first part of a staged operation for patients with super obesity with the plan of converting to RYGB once a reasonable weight loss was achieved Recent studies show weight loss with this procedure to be comparable to RYGB with a similar percentage of EBW loss. Thus, a second surgery may not be required for many patients.[15–17]

Biliopancreatic diversion and biliopancratic diversion with duodenal switch. Biliopancreatic diversion (BPD) and biliopancratic diversion with duodenal switch (BPD DS) is the most malasborptive procedure. It is both restrictive and malabsorptive. Long-term weight loss is estimated at 61 to 73 percent EBW loss after two years. However, this procedure carries some significant potential complications, including anastomotic stenosis, protein-calorie malnutrition, and small bowel obstruction. Patients undergoing this procedure are at a much higher risk of vitamin/mineral deficiencies.[13]

Possible Issues with Various Procedures for Renal Disease
Experience with patients who have undergone LAGB has shown that it is possible for patients to consume too many calories by consuming liquids with meals or eating high-calorie foods. This procedure does not produce “dumping” symptoms that are more common with RYGB patients after eating high-sugar/fatty foods.[13] So, for patients who have a tendency to eat these types of foods or to snack frequently, this procedure can be less effective than others.

With RYGB being a malabsorptive procedure, there is potential for poor absorption of many nutrients. Additionally, some dialysis patients have difficulty maintaining a good nutritional status (e.g., adequate serum albumin and hemoglobin), and this type of surgery may present increased risk for malnutrition.

Renal stones. There is an increased prevalence of kidney stones following gastric bypass procedures. Frequent kidney stones are linked with worsening of renal function and may contribute to development of CKD in patients with otherwise normal renal function prior to surgery.
Kidney stones are associated with higher levels of oxalate in urine. It appears that provision of oral calcium and oral citrate supplements can decrease risk for stone formation in weight loss surgery patients. Although provision of calcium citrate is common in many patients post weight loss surgery, calcium citrate is not given to and is not safe for patients with chronic renal failure due to increased serum levels of aluminum that can accompany this particular supplementation.

Restrictive procedures (e.g., banding and gastric sleeve) do not appear to hold this same risk for development of kidney stones. In a recent study, patients who had a restrictive procedure for weight loss had urinary oxalate levels similar to levels found in nonstone forming and stone-forming controls. Levels of urinary oxalate were significantly lower than in patients who underwent RYGB.[18–21]

Nutrient Issues
Protein. Post weight loss surgery patients are encouraged to achieve and maintain an adequate protein intake. This can be a challenge for any patient with the small size of the stomach pouch and food intolerances after surgery.[13] For patients with ESRD on dialysis, maintenance of protein adequacy is a common problem. For patients with CKD nearing dialysis, predialysis diet prescriptions frequently recommend limited protein. Protein recommendations should be individualized based on comorbid chronic conditions and laboratory measures of protein stores.[22]
Renal diet versus post weight loss surgery diet. Foods normally encouraged as part of a healthy diet for bariatric patients may be limited on CKD diet. Lab values need to be monitored frequently. For patients with CKD and/or ESRD, recommendations for limiting protein and minerals should be adjusted based on laboratory measures.

One common nutrition issue for CKD patients is elevated serum phosphorus. Foods high in phosphorus include whole grains, beans/legumes, nuts, and milk. Following weight loss surgery, patients are generally encouraged to consume these foods to help meet protein, fiber, and some vitamins/mineral needs.

Elevated serum potassium may necessitate a decreased intake of certain fruits and vegetables in addition to milk/dairy products.
Thus, limiting certain foods due to high serum levels of phosphorus or potassium may necessitate a decrease in foods also high in protein, further contributing to potential protein inadequacy.[22,23]

Minerals/vitamins. The optimal supplementation of vitamins and minerals is not really known for patients with ESRD on dialysis who have also had bariatric surgery. However, in March 2008, the American Society for Metabolic and Bariatric Surgery (ASMBS) published nutrition guidelines for the surgical weight loss patient.[24] This paper addressed optimal methods for nutrition assessment of pre- and post-weight loss surgery patients. Supplementation guidelines for vitamin/minerals for the three most common types of weight loss surgery were provided based on studies available at the time. Specific recommendations for patients following sleeve gastrectomy were not given. The article stated, “As advances are made in the field of bariatrics and nutrition, updates regarding supplementation suggestions are expected.”[24] Later that same year, a retrospective study of 137 RYGB patients published in the American Journal of Clinical Nutrition Studies concluded that nutritional deficiencies following bariatric surgery cannot be prevented by provision of a standard multiple vitamin preparation.[25]

In several studies, deficient levels of vitamins and minerals have been found in patients prior to bariatric surgery. Vitamins identified included vitamin B12, folate, vitamin A and vitamin D (25 OH). Minerals that were deficient included zinc, ferritin (iron stores), selenium, and magnesium. Additionally, low levels of albumin and hemoglobin have also been identified preoperatively. These same nutrients were frequently deficient at one year postoperatively, but many were improved compared to preoperative levels.[26,27]

Most weight loss surgery patients are told to take a “good” multivitamin with mineral supplement. Some nutrients have commonly been supplemented at higher levels than found in a multivitamin, including iron, vitamin B12, and calcium. Vitamin D is also frequently supplemented at higher than recommended dietary allowance (RDA). Deficient nutrients that have been previously under-recognized include copper, magnesium, thiamine, zinc, vitamin K, and vitamin B6.[28–30]

Multiple vitamin and mineral supplements vary greatly. Standard chewable forms may not be as “complete” as nonchewable multiple vitamins with minerals. It is necessary to compare products, especially as new products developed specifically for weight loss surgery patients are being developed. Dietitians should know the contents of the supplements taken and look for any nutrients provided in insufficient amounts.
Vitamin D. Vitamin D has been a hot topic among researchers for a number of years. It is now recognized that patients with obesity are more likely to have insufficient serum 25 OH vitamin D. Many patients are already deficient in vitamin D at the time of weight loss surgery.
Hypovitaminosis D and bone loss are common in patients after gastric bypass. In one study, to correct the serum 25 OH levels, the mean supplementation provided was 6,472IU of vitamin D per day.31 However, the Institute of Medicine released Dietary Reference Intakes for Calcium and Vitamin D, 2011.32 It suggested the upper safe level for vitamin D is 4,000 IU/day. This recommendation was made for the general “healthy” population and not specific to patients with obesity. In fact, the report does note that serum levels of vitamin D are frequently low in individuals with obesity.[32]

This fat-soluble vitamin can be difficult to replete and maintain adequate levels. Serum 25-OH D3 may rise by 1ng/mL for every 100IU of additional vitamin D provided. Some studies indicate that vitamin D3 (cholecalciferol), derived from animal or microbial sources, is more effective for repletion that provision of vitamin D2 (ergocalciferol), which is derived from plants. Optimal 25-OH D3 levels are thought to be greater than 32ng/mL.[33] Obtaining serum 25 OH vitamin D levels is the best way to know if the amount of vitamin D being supplemented is adequate.

Patients with ESRD are no longer able to convert 25 OH vitamin D to its active form (1-25 OH vitamin D). Routine supplementation of vitamin D (D3 or D2) in patients with ESRD on dialysis was not common due to the assumption that supplementation of either form of vitamin D would result in hypercalcemia. Supplementation with vitamin D3 in order to replete 25 OH vitamin D levels does not cause hypercalcemia. Adequate 25 OH vitamin D levels are required to maintain normal parathyroid hormone (PTH) levels.[34,35] In addition, restoring vitamin D to normal range may also have an epoetin-sparing effect.[36]

Hemodialysis patients with vitamin D deficiency who were not supplemented to reach normal levels had a higher incidence of mortality compared to those who were supplemented, and had the highest serum 25 OH vitamin D or 1,25 D levels.[36]

Signs of vitamin D insufficiency or deficiency are not obvious. Rickets and osteomalacia are two bone-related deficiency conditions. Other signs may be more subtle, including muscle pain or arthritis pain. In the elderly population, muscle weakness and cognitive impairment have been improved by increased vitamin D intake.[37,38]

Iron. Iron deficiency is very common after gastric bypass, occurring in 33 to 50 percent of patients. Serum ferritin is the most sensitive marker for storage iron, and thus can be used by the provider as an early indicator of iron deficiency. Heme iron is the form found in animal protein and is the most effectively absorbed. However, intolerance of red meats (good heme iron sources) and other meats can be a problem in many patients. The duodenum and proximal jejunum are the primary sites of iron absorption, and in gastric bypass, the duodenum is bypassed.[13]

Nonheme (plant) or inorganic forms of iron are relatively inexpensive and readily available over the counter. Supplementation with ferrous forms of iron is common practice in post-weight loss surgery patients. Inorganic forms of iron can cause gastrointestinal disturbances, such as constipation and its associated discomfort. Adequate stomach acid is needed for absorption of nonheme iron and there is decreased hydrochloric acid production with all of the types of bariatric surgery. Proton pump inhibitors (PPIs) are commonly used in weight loss surgery patients, thus decreasing stomach acid production.[39]

It is common practice to recommend separating iron supplements from calcium supplements by 1 to 2 hours due to competition for absorption in the gastrointestinal tract. However, in a study examining the effect of adding a calcium-rich food to a meal containing both heme and nonheme forms of iron, there were several useful observations. The addition of a calcium-rich food did not impair absorption of either heme or nonheme iron. Heme iron absorption may take longer and continue further down the intestine than nonheme iron. Provision of a nonheme iron supplement appears to be effectively absorbed if given with a heme form of iron (generally a meal consisting of meat).[40] Consumption of vitamin C (ascorbic acid) or a source of food high in vitamin C is frequently recommended to provide an acidic environment to improve nonheme supplement forms of iron.[24]

In renal bariatric patients, anemia management could be an even bigger challenge. In patients with CDK, iron deficiency is common and anemia management is complex. In patients with CKD who are not on dialysis, provision of either oral iron or intravenous (IV) iron may delay the need for erythropoiesis-stimulating medications. Patients on hemodialysis are less able to absorb oral iron due to elevated serum levels of hepcidin, which also impairs ability to recycle iron in the normal reticuloendothelial system. IV iron is more effective in hemodialysis patients to increase ferritin and decrease the need for erythropoetic-stimulants.[41,42]

B vitamins. Deficiency of vitamin B12 (cobalamin) has been recognized as a common problem in bariatric surgery patients for many years. Increased provision of vitamin B12 is part of the supplementation plan for gastric bypass patients due to decreased production of intrinsic factor. In the gastric sleeve patient, the fundus of the stomach is removed, and it is presumed that less intrinsic factor is made with this procedure.[43]
Deficiency of vitamin B12 can cause pernicious anemia, nerve degeneration and peripheral neuropathy. Pernicious anemia is a condition in which the body does not make enough of a protein called “Intrinsic Factor,” which is required for absorption of B12. Besides weight loss surgery, other common causes of pernicious anemia include a weakened stomach lining (atrophic gastritis) and autoimmune conditions where the body attacks the cells of the stomach that make intrinsic factor. Provision of 500mcg or more oral or sublingual B12 is usually sufficient to prevent deficiency; however, some patients may require monthly injections of B12 to maintain desirable levels. Stomach acid is required to absorb naturally occurring cobalamin; however, forms that are added to foods or used in supplements do not require acid for absorption.[43]

Thiamine (B1) can be deficient in weight loss surgery patients who have lost weight very rapidly or who have frequent vomiting.[13] Serious effects of thiamine deficiency include Wernicke’s encephalopathy, affecting gait, and peripheral neuropathy. If not caught quickly, repletion of thiamine levels may not completely reverse the symptoms. It may take 3 to 6 months for symptoms to resolve after repletion. Daily supplementation is advised as the body has limited stores of thiamine. IV repletion is effective with doses of 100mg for 3 to 14 days followed by an oral supplement maintenance dose of around 20 to 100mg per day to maintain adequate stores.[44]

Most prescription and over-the-counter renal vitamin preparations contain B vitamins at levels at or above the RDA. Some may also contain vitamin E, iron, and trace minerals. These supplements do vary, so careful selection of an appropriate product is desirable.

Other minerals. Necessary for making red blood cells, copper is essential. In addition, copper is a cofactor in enzymes involved with vascular and skeletal tissues. It is absorbed in the duodenum and proximal jejunum. Deficiency of this mineral can mimic symptoms of vitamin B12 deficiency, including gait disturbances, peripheral neuropathy, muscle weakness, and anemia.[45] Cases of patients with optic neuropathy and myopathy due to copper deficiency have been documented.[46] Hemodialysis does not remove copper; however, levels should be monitored in hemodialysis patients who have had gastric bypass as deficiency has been reported. Measurement of not only serum copper, but also ceruloplasm is recommended to detect deficiencies.[47]

Zinc is an important mineral involved in more than 300 enzyme systems in the body and necessary for proper immune function. It has been found to be deficient in many gastric bypass patients. Signs of deficiency include taste acuity changes, loss of appetite, loss of hair, or skin changes. If meat intake is low, zinc, iron, and copper may be be at risk for deficiency. Deficiency of zinc is difficult to detect since serum zinc represents less than 0.1 percent of total zinc stores.[13]

Zinc is not removed during hemodialysis. Provision of too much supplemental zinc can interfere with activity of copper in the body. Doses of 50mg or more per day can be problematic for copper metabolism.[43]

Vitamin K. A number of studies examining vitamin K are emerging due to its effect with bone health and prevention of vascular calcification.[48] This nutrient is frequently avoided in patients on warfarin therapy; however, adequacy and consistency of vitamin K intake are important for stable PT-INRs.[49] PT-INR is a lab test done to determine how long it takes for the blood to clot (prothrombin time). Variability in clotting time can put patients at risk for excessive bleeding if on warfarin.[49] In CKD patients, cardiovascular disease is a risk and a significant cause of mortality.[50]

Calcium and vitamin D have long been identified as big players in the prevention of osteoporosis. Osteopenic changes can occur rapidly in patients after gastric bypass. However, vitamin K is a cofactor necessary for activation of osteocalcin, a hormone that allows calcium to get into bone. Insufficient vitamin K and subsequently inadequate levels of osteocalcin, could impact calcium deposits in blood vessels and even the kidney. Both vitamin D and vitamin K deficiencies have been associated with vascular calcification in CKD patients.[51–55]

Matrix Gla protein (MGP) is vitamin K dependent. It acts as a calcification inhibitor in the vascular system. Adequate levels of MGP may play a significant role in prevention of vascular calcification.[52,53,56]

In a study reported in 2004, more than half of the patients four years post BPD were shown to be deficient in vitamin K. As noted in the ASMBS article, prothrombin time has been used as an indicator for deficiency and patients post RYGB had levels suggestive of deficiency compared to LAGB patients and controls.[24] This may not only be an issue for patients who have malabsorptive bariatric procedures. There was a case report of fetal cerebral hemorrhage resulting from maternal vitamin K deficiency following gastric adjustable banding.[57]

It is reasonable to evaluate food intake in patients with hemodialysis following weight loss surgery, as some foods that may be discouraged due to elevated serum potassium or phosphorus levels may also be those that are a good sources of vitamin K.

Calcium. Serum calcium is monitored closely in patients with ESRD. There is a delicate interplay between serum calcium, ionized calcium, serum phosphorus, PTH, and vitamin D. Because of this, it is desirable for the dietitian to work with the nephrologist to determine need for and adequacy of calcium supplementation. Some phosphate binders are calcium based and can be a problematic by elevating serum calcium levels too much. Using a noncalcium containing phosphate binder may be preferable in hemodialysis patients. Monitoring bone mineralization markers may be of assistance in this determination.[31,53]

Vitamin A. Studies of vitamin and mineral deficiencies occurring after bariatric surgery are numerous. However, the next question to ask is  “how much is too much?” In the renal dialysis population, toxicity of vitamin A is a concern as they may have levels higher than people without renal disease even without supplementation.[43]

A study published in 2010 looked at vitamin and mineral levels in gastric sleeve patients. They noted multiple vitamin and mineral deficiencies and hypervitaminosis A was found in 26 (48%) of their 60 study participants. In addition, thiamine and vitamin B6 levels were elevated in about 30 percent of participants. The levels of B vitamins were not considered to be harmful.[58]

High levels of preformed vitamin A (retinol) can lead to problems, such as ataxia, alopecia, dry skin, and liver problems. They can affect bone health by causing resorption of bone.[43,58] In the study by Aarts EO et al,[58] a multiple vitamin that included the RDA for vitamin A was recommended three times per day. A multiple vitamin provided three times a day is in excess of recommended supplementation guidelines published by the ASMBS.[24] This study does not state how much of the vitamin A was preformed (retinol) versus betacarotene. Serum levels of vitamin A did not did not exceed 4 µmol/L after one year of supplementation.[58]

Medication Issues
With the unpredictability of absorption of vitamin and minerals following weight loss surgery, it seems reasonable to be concerned about the reliability of medication absorption for renal patients. In such a patient, can one count on the medication absorption necessary to prevent organ rejection after a kidney transplant?

A pilot study published in 2008 examined the pharmacokinetics of three modern immunosupressants (mycophenoic acid, tacrolimus, and sirolimus) after gastric bypass patients with ESRD and post-kidney transplant.[59] They found that significant differences in dosages were required for RYGB patients compared with nonbypass population. There was significant interpatient variability in the RYGB patients group.
Researchers at the University of Oslo studied pharmacokinetics of atorvastatin in 12 patients with morbid obesity before and following gastric bypass surgery.[60] Variable affects were seen in uptake of the statin. Researchers concluded that retitration of atorvastatin (compared to presurgical dose) is necessary following surgery to provide the lowest effective dose on an individual basis.

A small study of patients who had weight loss surgery following renal transplantation showed no alterations in the dosages of immunosuppressant medications that were needed post-bariatric surgery.[61]

Other Supplements
A number of studies have examined various supplements to aid in weight loss. There are a couple of candidates with relevance to both renal disease and weight loss.

One of these substances is acetyl L carnitine. This protein is made of two amino acids, lysine, and methionine. It is available primarily from meat protein, but is also synthesized in the body. However, some conditions and medications may interfere with its metabolism and may even cause secondary deficiency.[62]

Carnitine is needed for metabolism of fat by the mitochondria. Insufficiency can mean a decreased ability to burn dietary and stored fat. For any patient, symptoms of potential insufficiency include the following: 1) excessive fat storage, 2) low muscle tone, 3) increased appetite (unable to make adequate ATP from food consumed), 4) poor exercise endurance, 5) increased fatigue, 6) excessive sleeping, 7) muscle pain with exertion, 8) elevated triglycerides, 9) low or unpredictable blood sugar levels (resulting from inability to effectively use stored fat for energy), and 10) cardiomyopathy. Hemodialysis patients with insufficient L-carnitine may have difficulty maintaining adequate red blood cell production.[62]
Provision of acetyl L carnitine has been shown to help with a variety of symptoms, including diabetic neuropathy, insulin resistance in metabolic syndrome, improved lipid parameters, improved exercise endurance, improved blood sugar levels, and improvement in memory.[62,63]

L-carnitine has been studied in the hemodialysis population. There is tissue depletion related to hemodialysis duration and extent of disease. In several studies, provision of L-carnitine in hemodialysis patients decreased need for erythropoetin to maintain hemoglobin levels. It has also been shown to have a protein sparing effect in hemodialysis patients.[64,65

In a study of children on hemodialysis, provision of l-carnitine reduced triglycerides, free fatty acids, total cholesterol, and increased HDL-C. Hemodialysis patients generally require IV administration of L-carnitine; however, a few studies have used oral L-carnitine. In addition to decreased need for erythropoietin, quality-of life-indicators have also improved with L-carnitine administration.[66–68]

The majority of L-carnintine is found in muscle and brain tissue; thus, serum levels of L-carnitine do not reflect muscle stores. A trial of oral L-carnitine in doses of 50mg/kg/day[67] or a typical dosage in adults of 3,000mg per day may be worth trying to see if energy levels improve in patients trying to lose weight. Patients may be better able to manage appetite if they are able to effectively burn stored fat. More research regarding acetyl-L-carnitine supplementation, specifically in post-weight loss surgery patients, would be helpful.

A second supplement showing benefit in postoperative weight loss was found as an unexpected consequence of its use. In a study[69] initially designed to see the impact on intestinal bacterial overgrowth and vitamin B12 levels, researchers found an additional impact on weight loss. Compared to control subjects, the probiotics provided in this study not only improved bacterial overgrowth and B12 levels compared to pre-operative levels, but also improved initial weight loss in postoperative patients during the initial three months after surgery.[69]

Two small studies[70,71] examined the effect probiotics have on reduction of uremic toxins in patients with stages 3 and 4 CKD. The authors found a reduction in blood urea nitrogen (BUN), but not creatinine. Longer duration studies with larger numbers of CKD patients are needed to determine effectiveness and safety of probiotics in the long term. The safety of use of probiotics in renal post-weight loss surgical patients remains a subject for further studies.

In patients with CKD or ESRD, weight loss surgery can certainly add complexity to care following surgery. For that reason, careful consideration of the type of procedure recommended for these patients is warranted. Careful and frequent monitoring by a dietitian can help patients improve or maintain nutritional status, prevent deficiencies, and avoid toxicities.

Although the sleeve gastrectomy surgery is not universally covered by third-party payers, it may be a good choice for patients who plan to have a kidney or organ transplant after achieving desired weight loss. Weight loss results to date do seem to be comparable to standard gastric bypass. Although, not promoted as a malabsorptive procedure, there still may be differences in absorption of nutrients and medications following sleeve gastrectomy.[58] Resolution of diabetes is reportedly similar to that of RYGB.[14]

AGB may be a good option for highly motivated patients; however, complications may still occur. Long-term issues include erosion of stomach, band slippage, and need for esophageal dilatation. These can all result in band removal or require additional surgery.[71] Food intolerances can also occur and have been a major reason for subsequent band removal.[72] Weight loss results for AGB are reportedly less than gastric bypass at one year post-surgery. So, for patients seeking weight loss to qualify as a transplant candidate, consideration for rate of weight loss may be a deciding factor in the choice of the different weight loss surgery procedures.

RYGB remains the most common weight loss procedure done today. It is becoming more cost effective, and, over the past decade, post-surgical complications appear to be declining.

Regardless of the type of weight loss procedure done, careful monitoring for nutrient deficiencies is needed. Medication adjustments may be required immediately following surgery and also over time. Ideally, a standard vitamin and mineral regimen for post-weight loss surgery with patients who have CKD or ESRD is desired. Yet, even with a standard recommended regimen, monitoring for deficiencies and toxicities over time seems prudent in all patients following weight loss surgical procedures.[24,74]

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