Navigating liver transplantation after malabsorptive bariatric surgery: A new risk of rejection

Abstract

Obesity and its complications, including metabolic dysfunction-associated steatohepatitis, are now major drivers of liver transplantation (LT) worldwide. Therefore, transplant surgeons are increasingly encountering patients who have undergone bariatric surgery prior to LT. Past reports suggested bariatric surgery does not adversely affect LT outcomes such as perioperative complications or survival. However, emerging evidence indicates a nuanced reality. Chang et al recently published a study in World Journal of Transplantation, that LT recipients with previous malabsorptive bariatric surgery (primarily Roux-en-Y gastric bypass) experienced a markedly higher incidence of acute cellular rejection compared to matched controls without bariatric surgery. Potential mechanisms - especially altered pharmacokinetics of immunosuppressants due to surgically modified anatomy - are explored. We consider the need for meticulous therapeutic drug monitoring and tailored immunosuppressive strategies in post-bariatric surgery transplant recipients. While the new data do not suggest changes in one-year survival, the increased early rejection risk signals a need for heightened vigilance. Transplant centers should be aware of this at-risk cohort and may consider proactive measures such as closer drug level monitoring, optimized immunosuppressant formulations, and multidisciplinary care. Ultimately, as bariatric surgery and transplantation continue to intersect, understanding and addressing the unique challenges in these patients will be critical to improving long-term graft outcomes.

Key Words: Metabolic dysfunction-associated steatotic liver disease; Liver fibrosis; Liver transplantation; Bariatric surgery; Acute cellular rejection; Immunosuppression management; Therapeutic drug monitoring

Core Tip: Malabsorptive bariatric surgery (for example, Roux-en-Y gastric bypass and duodenal switch) is increasingly common among liver transplant candidates. Chang et al report significantly higher rates, frequency, and earlier onset of biopsy-proven acute cellular rejection in recipients with prior malabsorptive anatomy, despite comparable perioperative outcomes and one-year survival. This editorial explores plausible mechanisms-especially impaired absorption of oral immunosuppressants-and outlines pragmatic strategies: Intensified therapeutic drug monitoring, dose and formulation adjustments (including extended-release tacrolimus), and multidisciplinary nutrition-pharmacy support to reduce rejection and protect long-term graft function.

This editorial refers to “Increased risk of rejection in liver transplant recipients with a history of malabsorptive bariatric surgery” by Chang J et al, 2025; https://dx.doi.org/10.5500/wjt.v15.i4.110957.

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INTRODUCTION

The global obesity epidemic continues to reshape both bariatric surgery practice and the demographic profile of liver transplantation (LT). In the United States, adult obesity prevalence has reached approximately 40% in recent years[1], paralleling a sustained increase in metabolic/bariatric procedures-an estimated 280000 in 2022 alone[2]. Within this growth, malabsorptive procedures such as Roux-en-Y gastric bypass (RYGB) and duodenal switch-procedures that divert segments of the small intestine-have retained or regained prominence; nearly one-quarter of operations in 2022 were RYGB or similar malabsorptive procedures[2]. This epidemiologic reality is directly relevant to transplantation. Obesity-driven liver disease, particularly metabolic dysfunction-associated steatotic liver disease [MASLD; encompassing metabolic dysfunction-associated steatohepatitis (MASH)], is now a leading indication for LT alongside alcohol-related liver disease[3]. In 2023, annual United States LT volume surpassed 10000 for the first time[4], and an increasing fraction of recipients present with a history of bariatric surgery[3,5]. Bariatric surgery is also being deployed in advanced liver disease to mitigate perioperative risk and slow disease progression[3,6]. Life-course data further underscore the pipeline pressure on adult programs: MASLD has emerged as the most common chronic liver disease in children, with a substantial proportion demonstrating inflammatory phenotypes and metabolic comorbidities at presentation[1,4]. Projections suggest that the burden of non-alcoholic steatohepatitis/MASH-related cirrhosis will nearly double by 2050, generating thousands of additional transplant candidates[7].

In a recent issue of the World Journal of Transplantation, Chang et al[5] reported a retrospective cohort study. Against this backdrop, earlier work offered cautious reassurance. Small retrospective series in the 2010s reported that prior bariatric surgery did not significantly worsen LT outcomes with respect to perioperative complications, graft survival, or patient survival[6,8]. Safwan et al[8] observed comparable one- and two-year outcomes among 11 recipients with prior bariatric procedures (mostly RYGB) vs non-bariatric counterparts, and a nationwide French analysis of 39 recipients likewise found no excess post-LT mortality or graft loss compared with matched obese controls[6]. These data supported the feasibility of LT after bariatric surgery, with some suggestion that sustained weight loss may attenuate weight recidivism and recurrent steatohepatitis in the graft[8]. Technical complexities (e.g., biliary reconstruction in altered anatomy) are well described but generally manageable with experienced teams[8]. The residual uncertainty has centered on whether malabsorptive anatomy exerts subtler, pharmacology-mediated effects on immunosuppression and rejection.

MALABSORPTIVE BARIATRIC SURGERY AND IMMUNOSUPPRESSION: A DOUBLE-EDGED SWORD

Malabsorptive operations permanently alter gastrointestinal anatomy in ways that plausibly affect both nutrient and drug absorption[9]. RYGB creates a small gastric pouch and bypasses the duodenum and proximal jejunum-sites central to the absorption of many orally administered agents. Consistent with pharmacologic first principles, systematic evaluations show that RYGB can meaningfully reduce systemic exposure (area under the concentration-time curve) for a substantial fraction of medications, with magnitude and direction varying by compound[10]. Immunosuppressants, with narrow therapeutic indices and complex absorption-metabolism profiles, are especially vulnerable. Tacrolimus-the cornerstone calcineurin inhibitor in LT-undergoes variably efficient intestinal uptake and extensive first-pass metabolism, yielding relatively low bioavailability even in normal anatomy[11,12]. Bypassing the duodenum and proximal jejunum after RYGB can therefore lead to decreased and erratic tacrolimus absorption[11,13]. In a pilot study of transplant recipients with prior gastric bypass, Rogers et al[11] demonstrated substantially lower tacrolimus trough levels and exposure compared with non-bypass comparators, necessitating higher doses to reach target concentrations[11,13]. These observations are concordant with clinical experience that post-bariatric patients frequently require intensified therapeutic drug monitoring (TDM) and tailored dosing to maintain adequate immunosuppression[10,14].

Importantly, not all bariatric procedures share this pharmacokinetic liability. Purely restrictive operations such as sleeve gastrectomy (SG) preserve intestinal length; in a prospective study of obese patients, SG was associated with increased tacrolimus exposure [higher area under the curve (AUC) and peak concentrations], plausibly reflecting accelerated gastric emptying and weight-loss-related metabolic changes[12,15]. This contrast strengthens the specific biological plausibility that malabsorptive anatomy-rather than gastric restriction per se-poses the principal challenge to post-LT immunosuppressive management[11].

Historically, direct links between prior bariatric surgery and post-LT rejection were sparse. Many centers reported routine immunosuppression in RYGB patients without obvious early complications; difficulties achieving tacrolimus targets were described more often in kidney transplant case series than in LT cohorts[14]. In the LT literature, a prevailing narrative held that intestinal bypass “did not complicate immunosuppressive management”[7], a view based largely on small samples and limited pharmacokinetic scrutiny. The recent analysis by Chang et al[5] materially alters that risk calculus.

NEW EVIDENCE: INCREASED REJECTION RISK AFTER MALABSORPTIVE BARIATRIC SURGERY

Chang et al[5] performed a single-center retrospective cohort study focusing on LT recipients with prior malabsorptive bariatric surgery (predominantly RYGB; one duodenal switch). Twelve such recipients transplanted between 2005-2024 were compared with 25 matched controls without bariatric history; matching accounted for age, sex, model for end-stage liver disease at listing, and primary liver disease to support clinical comparability[5]. The principal finding is compelling: Biopsy-proven, clinically treated acute cellular rejection occurred significantly more often in the post-bariatric group-66.7% vs 24% in controls (P = 0.012)[5]. Rejection was not only more frequent (1.0 vs 0.28 episodes per patient, P < 0.01) but also occurred earlier, with Kaplan-Meier analysis demonstrating a significantly shorter time to first rejection episode (P = 0.002)[5]. In propensity-score analyses, the malabsorptive group exhibited a substantially higher average risk of rejection relative to matched controls (average increase approximately 41.7%, 95%CI: 3.0%-80.3%)[5].

Crucially, these rejection differences arose despite comparable perioperative parameters. Operative characteristics (including cold ischemia time), postoperative complications, and length of stay did not differ meaningfully between groups; all transplants used standard techniques, and vascular anastomoses were uneventful in both cohorts[5]. One-year patient and graft survival were similarly excellent (100% vs 96%)[5]. Thus, the signal appears specific to immunologic control rather than surgical risk-consistent with a pharmacokinetic mechanism attenuating effective immunosuppression in malabsorptive anatomy.

Within the malabsorptive cohort, Chang et al[5] did not report clear demographic or clinical differences between recipients who developed acute cellular rejection and those who did not, likely reflecting the limited power of a 12-patient series. In contrast, earlier, smaller series such as Safwan et al[8] described relatively low rejection rates among recipients with prior bariatric surgery despite similar Roux-en-Y predominance, suggesting that some individuals with bypass anatomy can maintain adequate immunosuppressant exposure under close monitoring. This heterogeneity underscores the need to better define which anatomic configurations, pharmacokinetic profiles, and adherence patterns confer relative protection vs vulnerability, so that surveillance intensity and adjunctive strategies can be targeted to those at highest risk.

MECHANISTIC CONSIDERATIONS: ALTERED DRUG ABSORPTION AND BEYOND

The parsimonious mechanistic explanation is subtherapeutic immunosuppressant exposure resulting from altered absorption kinetics in bypassed intestine[9]. Tacrolimus, maintained universally alongside mycophenolate mofetil (MMF) in the Chang cohort, is notable for inter- and intra-individual variability even with intact anatomy[11,13]. RYGB superimposes reduced absorptive surface area, altered luminal pH, modified bile acid flux, and accelerated transit, any of which can impair dissolution, solubility, and mucosal uptake[9,12]. MMF, whose active moiety is absorbed predominantly in the small intestine, likely encounters analogous constraints[10]. If combined tacrolimus and MMF exposure fall below pharmacodynamic thresholds, alloimmune activation becomes more probable, manifesting as earlier and more frequent acute rejection.

Chang et al[5] found no differences in other determinants of rejection risk-donor quality proxies, ischemia times, or surgical complications-supporting a pharmacologic rather than technical explanation. Although their retrospective design limited standardized pharmacokinetic assessment, prior studies provide triangulating evidence: Comprehensive reviews describe multi-factorial exposure decrements after RYGB (solubility, bypassed segments, potential shifts in intestinal metabolism)[9]; tacrolimus absorption, while possible from duodenum through colon, relies heavily on proximal small intestine[11]; and case-level experiences in kidney transplant recipients document persistent subtherapeutic troughs despite high oral dosing and formulation switches, occasionally necessitating metabolic inhibitors to raise levels[2,14,16].

Alternative or adjunctive pathways merit acknowledgment[17]. Bariatric surgery reshapes gut microbiota and mucosal immune milieus; theoretical effects on systemic immune tone or antigen presentation cannot be excluded. Micronutrient deficiencies-fat-soluble vitamins (including vitamin D), trace elements, or protein malnutrition-may modulate innate and adaptive immunity as well as wound healing. The present study integrated dietetic assessment and support, likely reducing the prevalence of overt malnutrition[5], but subtle deficiencies could remain clinically relevant. Demographic skew (e.g., the predominance of female recipients in the malabsorptive group) may confound immune outcomes in some settings, though sex was matched here[5]. Nonetheless, the weight of evidence-coupled with the temporal patterning of early rejection-most strongly implicates pharmacokinetic insufficiency as the driver[2,16].

CLINICAL IMPLICATIONS: MANAGING THE POST-BARIATRIC LIVER TRANSPLANT RECIPIENT

The translational message is clear: An increased propensity for acute rejection in recipients with malabsorptive anatomy necessitates proactive, protocolized, and increasingly individualized management across the pre-, peri-, and post-transplant continuum.

Enhanced therapeutic drug monitoring: Centers should adopt lower thresholds for intensified TDM of calcineurin inhibitors in this cohort[16]. Early post-LT phases warrant more frequent tacrolimus troughs-and, where feasible, limited sampling strategies to estimate exposure (AUC)-with rapid adjustment to target ranges. Variability that might otherwise be observed conservatively should prompt intervention in bypass patients. Extending monitoring to MMF active metabolites is reasonable when clinically indicated[5].

Dose and formulation optimization: Anticipating reduced bioavailability, clinicians may consider higher initial tacrolimus dosing with expedited titration[11]. The use of extended-release tacrolimus (e.g., Envarsus XR^®/Advagraf^®), which shifts absorption distally (ileum/colon), is mechanistically attractive for RYGB anatomy[12]. While once-daily formulations demonstrate non-inferiority in general LT populations[5,15], their specific advantage in post-bariatric recipients remains to be proven[18]. In refractory cases, alternative routes (e.g., administration via a jejunal feeding access if present) or judicious use of metabolic inhibitors (e.g., azoles) to increase tacrolimus exposure may be considered-with vigilant toxicity surveillance[19].

Immunosuppressive regimen modifications: If therapeutic calcineurin levels are difficult to sustain, induction with an intravenous agent (e.g., basiliximab) may buffer early alloimmune risk while oral regimens are optimized. mTOR inhibitors are also orally absorbed and not exempt from malabsorption concerns, but pharmacokinetic profiles differ[10]; individualized regimen design remains essential[20]. Belatacept offers the conceptual benefit of IV delivery but is not widely adopted in LT due to rejection concerns in trials.

Multidisciplinary support and nutrition: Integrated care with transplant hepatology/surgery, bariatric specialists, pharmacists, and dietitians is pivotal[21]. Correcting protein-calorie deficits and micronutrient abnormalities supports both drug handling and immune competence. Patient education should enforce adherence and consistency with food intake, as high-fat meals can depress tacrolimus absorption[11].

It bears emphasis that higher rejection incidence in the Chang et al’s cohort[5] did not translate into excess early mortality or graft loss; all episodes were managed successfully, and one-year survival was preserved. Nonetheless, each rejection event carries morbidity, resource utilization, and potential long-term consequences. Prevention via anticipatory pharmacologic strategies is preferable to rescue therapy[12].

Beyond anatomy and drug handling, traditional recipient-level risk factors for rejection remain highly relevant in this post-bariatric population. Large cohort studies in unselected adult LT recipients have shown that younger recipient age, female sex, acute liver failure, autoimmune indications, donor-recipient sex discordance, and biliary complications are associated with higher rates of acute cellular rejection[22-24]. Accordingly, pre-transplant evaluation of candidates with prior malabsorptive procedures should integrate age, sex, comorbidities such as diabetes or chronic kidney disease, and prior sensitizing events, alongside bariatric anatomy. Patients who accumulate multiple risk factors may warrant more intensive early surveillance, consideration of induction therapy, and tighter TDM thresholds than those with lower baseline immunologic risk[24].

In parallel, the overall philosophy of care for this group should move decisively from “one size fits all” to truly individualized, full-process management. This begins with explicit recognition at the time of listing that prior malabsorptive bariatric surgery constitutes a high-risk feature, prompting careful nutritional optimization and a tailored immunosuppression plan before LT. Intraoperatively and in the early postoperative period, collaboration between transplant surgeons, hepatologists, bariatric surgeons, pharmacists, and nutrition specialists is essential to anticipate anatomical challenges, secure reliable enteral access when appropriate, and align drug delivery routes with the altered gastrointestinal anatomy. Early reports of multidisciplinary bariatric-transplant programs suggest that such coordinated care can safely deliver bariatric interventions in LT recipients, with acceptable complication profiles and metabolic benefit[3,6,25].

Implementing this degree of individualization inevitably raises questions of cost and feasibility. More frequent clinic visits, intensive drug-level monitoring, and use of extended-release tacrolimus or alternative delivery routes increase short-term healthcare utilization. Recent cost analyses indicate that a single episode of acute rejection following LT imposes a substantial economic burden. Specifically, studies estimate the mean direct hospital cost for such an event at approximately US$12000 (primarily attributed to medication and laboratory expenses in Turkey[26]) and within the range of US$14000–$22000 in the United States, based on data derived from kidney transplant recipients[27,28]. From a systems perspective, this economic burden supports investment in preventive strategies; however, from the patient perspective, travel time, lost work, and variability in insurance coverage for newer immunosuppressive formulations may limit adherence to intensive protocols.

Patient willingness and capacity to engage with such close follow-up are therefore central determinants of real-world success. Structured education, involvement of social work and financial counseling, and shared decision-making can help align monitoring intensity with each patient’s values and resources. At present, there are no dedicated studies evaluating the cost-effectiveness or patient-reported outcomes of highly individualized post-LT pathways specifically in recipients with prior bariatric surgery, and we identify this as a key area for future health-services research.

FUTURE DIRECTIONS AND RESEARCH NEEDS

While Chang et al[5] provide a critical signal, the small sample (12 malabsorptive recipients) and single-center design call for confirmation. A multicenter registry capturing bariatric history, surgical anatomy, immunosuppressive regimens, and standardized pharmacokinetics would enable robust risk quantification and adjustment for center effects. Procedure-specific analyses are essential: Current data imply that SG and RYGB are not equivalent with respect to drug exposure[15,20]. Prospective pharmacokinetic trials in post-bariatric LT recipients-with protocolized serial tacrolimus and MMF levels in the first 3-6 months-should define dose-exposure relationships, variability, and optimal target ranges for this anatomy[29]. Comparative studies of immediate-release vs extended-release tacrolimus (and granule formulations) in malabsorptive anatomy could be practice-changing[2].

Equally important is delineating the long-term sequelae of early rejection in this cohort. Does early under-immunosuppression predispose to chronic ductopenic rejection or accelerated allograft fibrosis? Modern LT has reduced chronic rejection incidence, but cumulative alloimmune injury remains relevant[5]. Longitudinal follow-up with histologic and non-invasive fibrosis assessment will be instructive[30].

Finally, the field should reconsider the timing and selection of bariatric procedures in candidates likely to require LT. For patients with cirrhosis and severe obesity, SG may offer weight-loss benefits with fewer malabsorptive pharmacologic liabilities[3]. Strategies including simultaneous or early post-LT bariatric surgery warrant careful patient selection and interdisciplinary planning[3,6,25]. As pediatric MASLD contributes an increasing pipeline of young adults with progressive disease, early, non-invasive risk stratification and metabolic interventions may modify trajectories and future LT complexity[31,32].

CONCLUSION

The convergence of obesity, bariatric surgery, and LT is creating a distinct clinical phenotype within transplant programs. Chang et al[5] highlight a specific vulnerability-heightened risk of acute cellular rejection-in recipients with malabsorptive surgical anatomy, most plausibly mediated by reduced and variable immunosuppressant exposure. For transplant hepatologists and surgeons, two imperatives follow: Avoid complacency (these are not “routine” post-LT patients) and act preemptively (protocolize intensified TDM, optimize formulations and dosing, and align multidisciplinary support). With research-informed adjustments-and, ultimately, tailored protocols for malabsorptive anatomy-centers can preserve the excellent survival observed to date while minimizing alloimmune risk. The observed rejection signal is a warning and an opportunity: To refine immunosuppression, fortify interdisciplinary care, and protect the longevity of the allograft for an evolving patient population.