Allocation of the kidney for candidates needing dual organ transplantation is determined by allocation of the primary organ (ie, liver in liver-kidney transplantation, pancreas in pancreas-kidney transplantation, and heart in heart-kidney transplantation). As a result, the wait time for a deceased donor kidney in dual organ transplantation is considerably less than for kidney alone transplantation.
Assessment of renal function in patients with cirrhosis
Serum creatinine or creatinine-based equations overestimate true glomerular filtration rate (GFR).
Cystatin C (CystC) has been extensively studied as an alternative endogenous marker of kidney function in cirrhotic patients because it is independent of muscle mass.
Limited studies suggest that CystC-based determinations had a better performance than serum creatinine-based equations.
Of the GFR estimation equations examined (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]-creatinine, CKD-EPI-CystC, and CKD-EPI-creatinine-CystC, and the 4- and 6-variable Modification of Diet In Renal Disease [MDRD], and Hoek formulas), CKD-EPI-CystC equation was shown to have the best performance irrespective of the severity of ascites and level of kidney dysfunction.1
CystC-based equations may enable clinicians to more accurately assess renal function in liver transplant candidates. However, it should be noted that
The superior performance of CystC over creatinine in cirrhotic patients with a GFR <80 mL/min has not been consistently demonstrated.2
CystC levels may be increased in high cell turnover states (such as hyperthyroidism, steroid use, malignancy, advanced age, gender and ethnicity, fat mass, and diabetes, among others).3
CystC is not yet readily available in many centers.
Renal clearance of inulin or radioisotopes such as technetium-99m mercaptoacetyltriglycine (99mTcMAG3) remains the gold standard for evaluating renal function in cirrhotic patients. However, it is seldom performed in clinical practice because it is cumbersome and costly.
Evaluation for simultaneous liver and kidney transplantation
Simultaneous liver and kidney transplantation (SLKT) is a well-established therapeutic option for suitable candidates with both end-stage kidney disease (ESKD) and end-stage liver disease.
In liver transplant candidates with acute kidney injury (AKI) superimposed on chronic kidney disease (CKD) or in those with sustained severe AKI due to hepatorenal syndrome or acute tubular necrosis (particularly those requiring renal replacement therapy), it is often difficult to predict the degree of renal function recovery after a successful orthotopic liver transplant. Therefore, assessing whether such patients would benefit from SLKT at the time of the liver transplant can be challenging.3,4
Historically, no well-defined guidelines for dual organ listing exist. Hence, the decision to list liver candidates with concurrent CKD or sustained AKI for simultaneous liver-kidney versus liver alone transplant was made at the discretion of the transplant physicians.3,4
In August 2017, the United Network for Organ Sharing/Organ Procurement Transplantation Network (UNOS/OPTN) committees set forth well-defined criteria for SLKT listing.5 Patients are categorized into those with CKD, AKI, or metabolic disease (summarized in Table 16-1 and briefly discussed in the following text).
Patients are eligible for SLKT listing if they fall into one of the following three categories5:
Preexisting CKD defined as a measured or calculated creatinine clearance (CrCl) or GFR of ≤60 mL/min for greater than 90 consecutive days prior to listing and at least one of the following: (1) Candidate has initiated chronic dialysis as an ESKD patient, (2) Most recent measured or calculated CrCl or GFR ≤30 mL/min, (3) On a date after registration on the kidney waiting list, measured or calculated CrCl or GFR ≤30 mL/min
TABLE 16-1 The 2018 United Network for Organ Sharing/Organ Procurement Transplantation Network Eligibility Criteria for Simultaneous Liver-Kidney Transplantation (SLKT)
OLT candidates with CKD
OLT candidates with sustained AKI
OLT candidates with metabolic disease
Preexisting CKD defined as measured or calculated CrCl or GFR ≤60 mL/min for greater than 90 consecutive days prior to listing
Sustained AKI defined as AKI present for at least 6 consecutive weeks (must be documented in patient’s medical records every 7 d)
CKD defined above and at least one of the following criteria must be present:
Patient has begun regular dialysis as an end-stage kidney disease patient.
Most recent measured or calculated CrCl or GFR ≤30 mL/min
On a date after registration on the kidney waiting list, measured or calculated CrCl or GFR ≤30 mL/min
Sustained AKI defined above and at least one of the following criteria must be present:
AKI requiring acute dialysis or
Measured or calculated CrCl or GFR ≤25 mL/min or
Any combination of no. 1 and 2
At least one of the following diagnoses must be present:
Atypical hemolytic uremic syndrome (aHUS) from mutations in factor H and possibly factor I
Familial nonneuropathic systematic amyloid
Abbreviations: AKI, acute kidney injury; SLKT, simultaneous liver kidney transplant; CrCl, creatinine clearance; CKD, chronic kidney disease; GFR, glomerular filtration rate; OLT, orthotopic liver transplant.
Sustained AKI defined as AKI present for at least 6 consecutive weeks (must be documented at least once every 7 days) and at least one of the following at the time of evaluation: (1) GFR of ≤25 mL/min, (2) AKI requiring acute dialysis, or (3) a combination of 1 and 2.
Confirmed diagnosis of metabolic disease and at least one of the following diagnoses: hyperoxaluria, atypical hemolytic uremic syndrome (HUS) from mutations in factor H or factor I, familial nonneuropathic systemic amyloid, methylmalonic aciduria
Avoidance of organ transplant futility: Wait-listed SLKT candidates whose condition deteriorates while awaiting dual organ transplant should be reassessed at regular intervals to avoid futile transplants.6
Safety net prioritization for liver recipients with nonrecovery of renal function7:
Recipients of liver alone transplant whose renal function does not recover (GFR remains ≤20 mL/min or dialysis dependent) between 60 and 365 days after a successful liver transplant are given a degree of “increased priority” in being offered a deceased donor kidney.
The transplant program must register the patient for a kidney transplant between 60 and 365 days after a liver transplant.
To remain eligible, the transplant program must confirm at least once every 30 days that the eligibility criteria continues to be met. Once the transplant program has confirmed eligibility over a duration of 90 days, the candidate will remain eligible for this priority until the candidate is removed from the kidney waiting list and the transplant program will no longer need to provide updated data.
The implementation of the safety net may relieve the clinicians’ pressure to perform SLKT when a liver alone transplant may suffice.
Note: Safety net eligible patients will be prioritized above the local adult waitlisted patients for donor kidneys with KDPI >20% (defined in chapter 6). However, highly sensitized kidney alone transplant candidates, zero HLA-ABDR mismatches, prior living donors, and pediatric kidney alone transplant candidates are still given priority over these patients (Table 16-2).