Introduction

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the USA with an estimated prevalence of 30% [1]. It encompasses a spectrum of diseases ranging from simple hepatic steatosis to steatosis with hepatocyte inflammation and ballooning (non-alcoholic steatohepatitis or NASH). The incidence of NAFLD has increased by a factor of 5 since 1997, with the most exponential increase in younger adults aged 18–39 years old [2]. Up to 30% of patients with NAFLD will eventually develop NASH, with 15–25% of NASH patients developing advanced cirrhosis [3]. Untreated, NASH may lead to advanced fibrosis and cirrhosis and ultimately hepatic complications including portal hypertension, hepatocellular cancer (HCC), and the need for liver transplantation [4,5,6].

Obesity is the most common risk factor for NAFLD with up to 75% of patients that are overweight and 90–95% of patients with morbid obesity affected by NAFLD [7, 8]. Additionally, there is a high prevalence of NAFLD in patients with type 2 diabetes mellitus (T2DM), with some studies citing up to 33–66% with T2DM having concomitant NAFLD [9, 10]. T2DM and obesity are the two most important risk factors for the development of advanced fibrosis and cirrhosis in patients with NAFLD [11]. Additionally, the severity of fibrosis progression is related to the degree of insulin resistance, T2DM, and central obesity with 5–20% fibrosis progression in 10 years [12, 13].

Metabolic syndrome (that includes three of the following: hypertension, insulin resistance, central obesity, elevated serum triglycerides (TG), and low high-density lipoprotein (HDL) cholesterol) [14] is also a risk factor for NAFLD, with prevalence rates ranging from 36 to 63% [15,16,17].

The presence of metabolic syndrome also increases the risk of severe fibrosis by an odds ratio of 3.5 (95% confidence interval (CI) 1.1–11.2) [18]. Some conditions also have emerging associations with NAFLD and include hypothyroidism, obstructive sleep apnea, hypopituitarism, and hypogonadism [19].

Patients with NAFLD are at risk for both liver- and non-liver-related events. One study that prospectively studied 458 NAFLD patients with F3 and F4 fibrosis found that those with F3 fibrosis had an increased risk of major vascular events and non-hepatic malignancies (9 and 10% respectively) while those with F4 cirrhosis were at increased risk of hepatic decompensation and the development of HCC [20]. NAFLD is an independent risk factor for death with increasing mortality with increased metabolic comorbidities and associated with cardiovascular events, especially in those without metabolic comorbidities [2]. Additionally, it has been associated with the development of chronic kidney disease and even increased risk of colon cancers [21, 22].

Given the increase in obesity and NAFLD, there has been a significant increase in liver transplantation (LT) for NASH since 2001 from 1.2 to 9.7% in 2009. By 2025, it is expected that 25 million Americans will be diagnosed with NASH with 20% progressing to cirrhosis making NASH the leading new indication for LT, surpassing hepatitis C (which is highly treatable now with effective direct-acting antiviral therapies) [23, 24]. However, given the comorbidities associated with NAFLD as discussed, unique challenges arise in the management of these patients pre-, peri-, and post-LT. Additionally, some of these patients may benefit from bariatric surgical procedures at the time of LT.

Although multiple medical therapies are in clinical trial development for the treatment of NASH and NAFLD, currently, there are no FDA-approved drug therapies for the treatment of NAFLD and NASH. Diet, exercise, and risk factor modification remain the cornerstone of treatment. There have been studies that have shown that weight loss of at least 3–5% of body weight can improve steatosis with 7–10% body weight reduction needed to reverse steatohepatitis and fibrosis [25, 26•]. However, long-term sustained weight loss is difficult to achieve in clinical practice, with only about 3–6% of subjects achieving this goal [27, 28]. Additionally, preliminary data also do suggest that aggressive risk factor modification may have an added benefit to the treatment of NAFLD [29,30,31]. Any intervention done to treat NAFLD should also improve comorbid risk factors, especially truncal obesity and insulin resistance [13].

Because sustained weight loss with diet and exercise alone is often difficult to achieve, many have turned to bariatric surgery as an option. We will review the current literature on the various types of bariatric surgery and its long-term efficacy and also discuss the emerging role of bariatric endoscopy in the treatment of NAFLD. In addition, we will review the role of LT in NAFLD and its unique challenges that need to be addressed in the care of these patients.

Bariatric Surgery

Although weight loss through hypocaloric diet and exercise can reverse the hepatic changes seen in NAFLD and NASH including early-stage fibrosis [26•], sustained weight loss is difficult to achieve through diet and exercise alone [32]. Because of this, bariatric surgery has emerged as an option that is increasingly utilized over the last several decades with achieved weight loss to be three times greater than that seen with behavior modification or pharmaceutical therapy over a 10-year period [33]. Introduced first in the 1950s, surgical techniques, volumes, and outcomes have evolved and improved since this time. Indications for bariatric surgery according to the National Institutes of Health include a BMI greater than 40 kg/m2 or in those with a BMI greater than 35 kg/m2 with other high-risk comorbidities including diabetes, hyperlipidemia, OSA, and cardiovascular disease [34].

The hypothesis surrounding the mechanism in which bariatric surgery induces weight loss is evolving. Previously, surgery was thought to be related to either a restrictive or malabsorptive process [35]. Restrictive surgeries reduce stomach size and consequently limit meal size and caloric intake and adjustable gastric banding (AGB) and vertical sleeve gastrectomy (SG). Malabsorptive surgery involves rearranging intestinal anatomy and bypassing variable intestinal lengths to minimize the absorptive surface, for example, jejunoileal bypass representing the most extreme form of malabsorptive surgery (and is no longer performed given its significant morbidity and mortality from severe weight loss, electrolyte disturbances, and rarely hepatic failure) [13]. Combinations of restrictive and malabsorptive procedures include Roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion (BDP). However, increasingly, it is thought that bariatric surgery induces physiological changes in gut peptide levels (increases in gut peptides such as GLP-1, PYY, CCK, and amylin, and decrease in ghrelin in the case for RYGB) and circulating bile acids [35]. Surgery also changes intestinal morphology and the microbiome and alters gastrointestinal signals to the brain and other tissue (such as the pancreas and liver) from a metabolic and neuronal perspective that results in weight loss [35].

Currently, RYGB and SG are the two most commonly performed surgeries in the USA, with SG rates on the rise since 2011 (18% in 2011 to 59% in 2017) [36]. In RYGB, suturing of the proximal stomach creates a small gastric pouch and connects to the mid-jejunum. The remaining distal stomach and proximal intestine remain but are bypassed without a digestive or nutritional role [35]. In SG, the stomach is resected along the greater curvature with about 80% being removed but with unchanged intestinal anatomy. Weight loss and resolution of metabolic parameters with SG and RYGB appear comparable [37].

Other surgical techniques include AGB where a 30-cc gastric pouch is created by placing a band around the upper stomach just below the gastroesophageal junction. A subcutaneous port linked to the band allows for the injection of saline, thereby modifying the degree of gastric constriction [38]. Given that the AGB is minimally invasive and allows for adjustability after surgery makes the gastric band an attractive option for some. However, its use has sharply declined from 35% in 2011 to 2.8% in 2017 because it produces less weight loss than other bariatric procedures with higher reoperation rates than RYGB [36, 37]. BPD with duodenal switch entails a SG with similar intestinal routing as in RYGP but the intestinal limb is bypassed to a greater extent with creation of an ileoduodenostomy [13]. Although this procedure produces more weight loss than RYGB, it also causes greater macro- and micronutrient deficiencies and can often lead to malnutrition and currently accounts for less than 1% of current bariatric procedures [36].

Effects of Bariatric Surgery on Mortality, Cardiovascular Disease, and Malignancy

There are established short- and long-term benefits in patients with medically complicated obesity who undergo bariatric surgery with durability of weight loss and remission and prevention in comorbid disease, including T2DM, hypertension, dyslipidemia, cardiovascular disease, and malignancy risk even up to 12 years post-surgery [33, 39, 40, 41••, 42,43,44]. The effects of bariatric surgery in the non-transplant setting are well established. In the Swedish Obese Subjects (SOS) study, patients that underwent bariatric surgery achieved greater maximal weight loss in 1–2 years post-surgery with the greatest loss of 32% achieved in those undergoing RYGB with sustained weight loss after 10 years [33]. Additionally, overall mortality was decreased in those undergoing weight loss surgery with the 0.71 hazard ratio (HR, p = 0.01) after adjusting for sex, age, and other risk factors with myocardial infarction and cancer being the most common causes of death [33]. Bariatric surgery also reduced the number of cardiovascular deaths in addition to the total first-time cardiovascular events (including myocardial infarction or stroke) [40].

Cancer incidence after bariatric surgery has also been found to be lower compared to matched controls. In a study looking at 6781 morbidly obese patients matched for age and sex, patients who underwent bariatric surgery had a 76% decrease in overall cancer incidence, especially that of breast cancer (reduced by 82%) [45]. Similar studies have reported decreases in overall cancer mortality of 60% at 7 years and 46% at 12.5 years and a 24% decrease in overall cancer incidence [46]. This effect is especially seen in females with hormone-related tumors [47]. These effects of bariatric surgery on cardiovascular and cancer mortality are especially important given that patients with NAFLD are at greatest risk of death from these causes.

Effects of Bariatric Surgery on NAFLD and NASH

In addition to improved mortality and cardiovascular risk, bariatric surgery also provides promising changes in those with NAFLD and NASH [13]. The decrease in adiposity seen after bariatric surgery is important given that adiposity is associated with insulin resistance, which in turn is associated with hepatic steatosis [48]. About 25% of patients undergoing bariatric surgery have NASH with incident cirrhosis found in about 1–2% of patients [13]. The initial experiences of bariatric surgery resulting in large amounts of weight loss with jejunoileal bypass, BPD, and RYGB with extended Roux limbs resulted in severe hepatic dysfunction with steatohepatitis and cholestasis, and even deadly hepatic failure [13, 49, 50]. Since that time, however, outcomes have improved.

Earlier smaller studies in patients undergoing AGB [51,52,53] and RYGB [54,55,56,57,58] showed promising effects on NAFLD and metabolic parameter improvements. A 2015 meta-analysis looked at the effects of bariatric surgery on several NAFLD histological features and found improvement in steatosis (50.2%), fibrosis (11.9%), ballooning (67.7%), and lobular inflammation (50.7%) in 16 studies in addition to liver enzymes including ALT, AST, alkaline phosphatase (ALP), and gamma-glutamyltransferase (GGT) [59].

A study conducted from 1994 through 2013 in France prospectively studied 109 morbidly obese patients undergoing bariatric surgery [60••]. Sixty-four percent underwent gastric bypass, 30% underwent gastric bands, 5.5% underwent sleeve gastrectomies, and 1 patient (0.9%) underwent biliointestinal bypass. NASH resolved in 85% of patients (95% CI 76–92%) with improvements in BMI, ALT, GGT, and insulin resistance index values at 1 year. Notably, compared to previous studies, fibrosis also decreased in 34% of patients (95% CI 24–45%). Those undergoing gastric banding had less weight loss and more persistent NASH than those undergoing RYGB (BMI change 6.4 vs 14.0; persistent NASH 30.4 vs 7.6% respectively).

One of the largest prospective studies linking clinical data with liver biopsy at the time of bariatric surgery with 5-year follow-up looked at 381 adult patients with severe obesity [61]. The majority of patients underwent gastric band (56%) with 23% and 21% having biliointestinal bypass and RYGB respectively [61]. Twenty-nine percent of patients had severe steatosis with only 4.1% with advanced fibrosis (F3–F4) at index biopsy. At 5 years following surgery, there were significant decreases in steatosis (37 to 16%), the NAFLD fibrosis score (1.97 to 1), ballooning (0.2 to 0.1), and percentage of patients with probable or definite NASH (27 to 15%) with parallel improvements in insulin resistance [61]. Severe insulin resistance was also most closely associated with persistent steatosis and ballooning. However, there was also a small but statistically significant increase in mean fibrosis score at 5 years, from 0.27 ± 0.55 to 0.36 ± 0.59, p = 0.001. Ninety percent of patients with fibrosis worsening increased from F0 to F1. The clinical significance of this finding is unclear given that 5 years only 0.5% had bridging fibrosis (F3) with 96% of patients with F1. Worsening fibrosis after RYGB has been reported in 2 other studies in 2 patients, with both developing perisinusoidal fibrosis [62, 63].

SG is now the most commonly used bariatric surgical procedure, but there are limited data on its effects on NAFLD. A retrospective review looking at 236 patients undergoing SG found overall improved weight loss with decreases in BMI from 45 to 29.7 at 1 year and 31.6 at 3 years. Using liver tests as a surrogate marker for NASH in 87 patients, the study found improvements in AST, ALT, triglyceride levels, and HDL levels at 6 and 12 month follow-ups [64]. Another smaller study compared 14 RYGB and 9 SG and found similar weight loss with both; however, all aspects of the NAFLD activity score improved significantly after RYGB but only steatosis and total score improved after SG [65]. Although fibrosis improved in both groups, greater effects were seen in RYGB.

The BariScan in Germany looked at the effects of SG (n = 59) and RYGB (n = 41) on NAFLD between 2012 and 2015 [66••]. However, liver biopsy was not done in this study and instead NAFLD was assessed using laboratory-based fibrosis scores and transient elastography. Significant improvements were seen across all liver fibrosis scores with improvements in liver stiffness (12.9 ± 10.4 vs 7.1 ± 3.7 kPa, p < 0.001) at median follow-up of 12.5 months. Similar to the previous study [65], RYGB showed greater fibrosis improvements than SG after adjusting for baseline liver stiffness.

Bariatric Surgery in Patients with NAFLD Cirrhosis

Few studies have examined reported bariatric surgery outcomes in patients with NAFLD cirrhosis. A 2015 meta-analysis found 122 patients in 11 studies with cirrhosis undergoing bariatric surgery, including BPD (n = 15, 12%), RYGB (n = 51, 42%), SG (n = 41, 34%), and AGB (n = 15, 12%) [67]. All patients had compensated cirrhosis and only 7 (n = 6%) had portal hypertension. The analysis found an overall complication rate of 21% with a 6.5% risk of liver decompensation. The early surgery-related mortality rate was 1.6% and the late surgery-related mortality rate was 2.45% and found only in those undergoing BPD (n = 3/15, 20%) and RYGB (3.9%, n = 2/51) but not in those undergoing VSG or AGB.

A larger study not included in the previous meta-analysis looking at inhospital mortality for patients undergoing surgery between 1998 and 2007 in the USA and found patients with compensated (n = 3888) or decompensated cirrhosis (n = 62) had significant higher mortality rates than those without cirrhosis (n = 670,950; 0.9% and 16.3% vs 0.3%, p = 0.002) with an adjusted odds ratio of mortality of 2.17 (95% CI 1.03–4.55) for compensated patients and 21.2 (95% 5.39–82.9) for decompensated cirrhosis compared to non-cirrhotics [68]. Mortality improved with increasing surgical volumes (> 100 surgeries/year).

This evidence shows that although bariatric surgery can be a safe option in patients with compensated cirrhosis, the risks and benefits of the surgery, type of surgical procedure, and patient selection are of paramount importance [32]. Additionally, pre-operative biopsies may be necessary in those at risk for NAFLD and advanced fibrosis, especially given that normal liver function tests such as ALT may not reliably exclude those with NASH [69].

Given the overall markedly positive evidence, the most recent AASLD guidelines on NAFLD management recommend that although it is premature to consider foregut bariatric surgery a specific option for the treatment of NASH, it can be considered in otherwise eligible obese patients with NAFLD and NASH [32]. NASH alone is currently not an indication for bariatric surgery based on NIH criteria [34] but it may be possible that this will change in the future given the histological and metabolic reversal seen. The optimal surgical procedure remains unclear. Additionally, hepatic function should be closely monitored following surgery given the potential, albeit small risk, for worsening fibrosis [70].

The Emerging Role of Bariatric Endoscopy

Over the past decade, bariatric endoscopy is emerging as a potential treatment option for obesity. Bariatric endoscopy can be used as the initial weight loss before bariatric surgery, as primary treatment for obesity or diabetes, or as a bridge to other interventions such as orthopedic surgery or even LT [71, 72]. Endoscopic therapies may also offer added advantages of reversibility, repeatability, and cost-effectiveness over bariatric surgery but these have to be balanced to the amount of weight loss and procedure durability [72, 73]. Most endoscopic therapies are indicated for patients with a BMI between 30 and 40 kg/m2 who have failed lifestyle or pharmacological interventions or who do not want to undergo bariatric surgical procedures [72].

Intragastric balloons (IGBs) have been found to be effective at total body weight loss with percent loss ranging from 6.8 to 14% at 6 months [72]. A single-blinded randomized controlled pilot study examined IGBs in 18 patients with NASH who were randomized either to sham or to real IGB placement for 6 months [74]. The IGB group had significantly decreased BMI and NAFLD activity score compared to the sham-treated group. There were no significant differences in median steatosis, inflammation, ballooning, or fibrosis in both groups. Additionally, a recent systematic review of 10 studies with 504 patients found ALT, GGT, and BMI all decreased with IGB therapy (− 10.02 U/l, − 9.82 U/l, and 4.98 kg/m2 respectively) [75]. There were also improvements in hepatic steatosis from baseline after 6 months as measured by magnetic resonance imaging fat fraction with lower NAS. Although preliminary results are promising, there has been recent question of their long-term safety data as the FDA has reported 12 deaths occurring (7 in the USA) in patients with liquid-filled intragastric balloon systems since 2016 [76]. Further trials regarding the safety and efficacy of IGBs are needed in this area to recommend IGBs for the treatment of NAFLD.

Endoscopic sleeve gastroplasty (ESG) decreases the size of the gastric cavity to facilitate weight loss. In a study of 248 patients with baseline BMI 37.8 kg/m2, ESG was found to achieve weight loss of up to 2 years [77] and also delay gastric emptying, improve insulin resistance, and induce early satiation [78]. Although not specifically looked at for the treatment of NAFLD, 91 patients undergoing ESG from 2013 to 2016 lost 14.4%, 17.6%, and 20.9% of their total body weight at 6, 12, and 24 months respectively with only one adverse event of a perigastric leak [79]. Additionally, at 1 year, there were significant reductions in ALT and metabolic parameters including HgA1c, blood pressure, waist circumference, and serum triglycerides. Given these promising results, future prospective studies looking at the role of ESG in the treatment of NAFLD are warranted.

Liver Transplantation and NAFLD

LT secondary to NASH has become the second most common indication for liver transplant in the USA in 2013 and will likely surpass hepatitis C in the coming years as the leading indication for transplant [23, 80, 81•]. Patients with NASH, however, have risk factors for poor post-operative outcomes including T2DM, obesity, cardiovascular disease, and chronic kidney disease [82]. In addition, NASH patients were significantly older with higher BMIs and lower GFRs [81•]. They also had lower MELD scores and were less likely to undergo LT with decreased 90-day survival on the waitlist as compared to patients with hepatitis C or alcoholic liver disease [81•]. A recent meta-analysis of 9 studies on 717 patients with NASH and 3520 patients without undergoing LT found similar 1-, 3-, and 5-year survival rates but also found that patients with NASH had a greater mortality from cardiovascular complications (OR 1.65, 95% CI 1.01–2.70, p = 0.05) or sepsis (OR 1.71; 95% CI, 1.17–2.50; p = 0.006) after transplant [83]. Given these findings and their inherent metabolic profile, there are many considerations that arise in patients with NASH that undergo LT in the pre and post setting.

In addition to the effect of NAFLD on LT recipients, the increasing prevalence of NAFLD in the general population also directly impacts the quality and quantity of the donor liver pool available for LT [84]. Graft steatosis can affect graft function (specifically placing recipients at risk for primary graft non-function or delayed graft function) and subsequent outcomes, with more than 30% macrovesicular steatosis being an independent risk factor for impaired 1-year graft survival [85, 86].

NAFLD, Obesity, and Pre-liver Transplantation

Obesity, more commonly found in patients with NAFLD and NASH, brings unique challenges in LT. First, from a surgical perspective, a higher BMI may make the surgery more technically challenging with increased operative times, increased intensive care unit length of stay, and increased infectious and biliary complications [87]. Additionally, a study looking at 161 patients with compensated cirrhosis found that higher BMI increases the risk of clinical decompensation independent of portal pressure and liver function (15% in those with normal BMI, 31% in overweight, 43% in obese patients, p = 0.011) [88]. As a result, NASH patients with higher BMI are at increased risk of clinical decompensation with higher MELD scores while awaiting LT [88, 89]. A previous study looking at the UNOS database from 1988 through 1996 concluded that morbidly obese patients had higher risk of primary graft non-function in addition to immediate and 1-, 2-, and 5-year mortality rates (mostly due to cardiovascular events at 5 years) [90]. However, more recent data indicate that when corrected for ascites, higher BMI had no effect on early or late patient and graft survival [91].

Although there is no universal upper limit BMI cutoff that disqualifies patients from LT and such rules are specific to institutions, some weight loss prior to LT is ideal with benefits in the post-LT as well. Additionally, pre- and post-LT weight and BMI have also been found to be the most important predictors of metabolic syndrome following liver transplantation (Fig. 1) [92]. Bariatric surgery at the time or post-LT is increasingly being utilized in patients with NASH. One study looked at the effectiveness of a multidisciplinary protocol for LT patients with a BMI > 35 including intensive lifestyle counseling and combined LT and SG for patients who failed to lose weight prior to LT [93••]. In the 34 patients who achieved adequate weight loss and underwent LT alone, 62% (n = 21) gained weight to BMI > 35 in the post-LT period with 35% (n = 12) developing T2DM and overall 3 deaths and 3 graft losses. In the 7 patients who underwent combined LT and SG, mean BMI post-LT was 29 and no posttransplant T2DM was observed (Fig. 2) [93••]. One patient developed a gastric leak and 1 had excess weight loss but allograft and patient survival were excellent. A systematic review of 11 studies with 56 patients undergoing LT and bariatric surgery (2 before, 2 simultaneous, and 7 after LT) found that SG (79%) was the most common procedure followed by RYGB (18%) [94]. There were no post-operative deaths within 30 days with a 1-year mortality rate of 5.3%. These early results show that SG may be a helpful adjunct to LT in obese patients but future studies are needed to determine optimal timing. There is also likely an evolving role for bariatric endoscopy in this setting.

Fig. 1
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Predictors of posttransplant metabolic syndrome

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Fig. 2
figure 2

Impact of simultaneous sleeve gastrectomy

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Bariatric surgery alters drug metabolism and this is important given the need for immunosuppression in the post-LT period. The effects of bariatric surgery on the pharmacokinetics of common immunosuppression agents vary greatly between SG and RYGB. The overall effect of RYGB is of decreased absorption and slower metabolism. Drug exposure, as measured by area under the curve (AUC), is reduced by 40–50% for tacrolimus, mycophenolate, and mTOR inhibitors in RYGB. The relative effects of sleeve gastrectomy vs RYGP are summarized in Table 1 [97].

Table 1 Metabolic effects of immunosuppression
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Another key consideration in the pre-operative LT assessment is cardiovascular risk, given its higher prevalence in patients with NASH [98]. The risk for peri-operative cardiovascular mortality is higher in patients with NASH cirrhosis compared to alcohol (OR 4.12, 95% CI 1.91–8.90) even after controlling for risk factors including age, sex, BMI, smoking, history of CAD, or metabolic syndrome [99]. It is currently unclear whether patients with NASH should be more intensively screened during their LT assessment, especially given that dobutamine stress echocardiography has been shown to have poor predictive value for coronary artery disease in NASH compared to patients with alcohol cirrhosis [100], but careful attention should be paid to identifying cardiovascular disease prior to LT [32].

NAFLD and Post-liver Transplantation

Several studies have shown excellent patient and graft survival outcomes in patients with NASH cirrhosis undergoing LT [23, 83]. Patients with severe obesity (BMI > 35) and pre-transplant hemodialysis have worse outcomes with decreased graft and overall survival [24]. In addition to cardiovascular risk previously mentioned, patients with NASH are also at increased risk for renal impairment both pre- and post-LT with one study showing 31% of patients developed stage 3b chronic kidney disease within 2 years compared to 8% of non-NASH patients independent of BMI, T2DM, and tacrolimus levels [101]. Additionally, the frequency of simultaneous liver-kidney transplantation is also disproportionally increasing in NASH cirrhosis compared to other etiologies with poorer outcomes [102].

It is important to remember that the agents for immunosuppression following liver transplantation have very specific and diverse effects on key aspects of the metabolic syndrome (Table 2) that occur independent of weight and BMI [95, 96, 103,104,105]. These medications also put patients at risk for recurrent NASH in the transplant setting. Bariatric surgery and associated weight loss may not fully negate the effects of immunosuppression on aspects of the metabolic syndrome.

Table 2 Impact of gastric sleeve vs Roux-en-Y gastric bypass on immunosuppression pharmacokinetics
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Recurrent NASH in the allograft is common post-LT but likely an uncommon cause of mortality or graft loss given excellent 5-year graft survival [23]. In 257 patients transplanted for either cryptogenic or NASH cirrhosis, 8% developed hepatic steatosis at 1 year with up to 33% at 10 years (compared to 3 and 10% respectively for those transplanted for other indications) [95]. NASH developed in 5% of this cohort but overall survival was not affected. Similar results have been seen in previous studies and found that NASH with progressive fibrosis is rare (5% of LT recipients at 5 years) [103, 105, 106]. This further underscores the importance of maintaining patients on the lowest effective doses of calcineurin inhibitors and rapamycin inhibitors.

Conclusions

The increasing NAFLD prevalence mirrors the global obesity epidemic and presents challenges in the management of these patients. There is an increasing use of bariatric surgery and an evolving role of bariatric endoscopy in patients with NAFLD pre- and post-LT. Such interventions not only aid in sustained weight loss but also improve metabolic parameters associated with liver disease, cardiovascular risk, and overall mortality. Further studies are needed to confirm which surgical procedures, timing, and NASH patients will receive most benefit. Additionally, as NAFLD will become the leading indication for liver transplantation in the USA in the near future, key challenges arise in the management of these patients pre-, peri-, and post-operatively. Optimal evaluation and management of obesity, metabolic parameters, cardiovascular risk, and chronic kidney disease remain challenges with continued need for refinement.