Beyond the Surgery: Comprehensive Monitoring in Organ Transplant Recipients

By: Alexandre “Sasha” Vlassov, Director, R&D, Thermo Fisher Scientific

In 2024, a record-breaking 48,149 organ transplants were performed in the United States [1]. Organ transplantation is a complex medical procedure that involves replacing a failing organ with a healthy one from a donor (living or deceased), transforming lives and offering a second chance for those with terminal organ failure. Pioneered by the first successful kidney transplant in the 1950s, modern advancements, particularly effective immunosuppressive drugs, have increased success rates and made it a common treatment. The process is supported by a network of organ donation and recovery programs, though challenges remain, including long waiting lists, geographic disparities in access, underuse of available organs, and ongoing ethical concerns for donors and recipients.

The Process: From Donor to Recipient

Donation: Organ donation can come from either a deceased donor or a living donor, who can donate organs like a kidney or a liver portion.
Allocation: A national system, like the United Network for Organ Sharing (UNOS), manages the organ waiting list, considering factors such as medical urgency, blood type, and geographic location for organ distribution.
Transplantation: The donated organ is surgically transplanted into the recipient to replace the damaged one, a procedure that significantly improves quality of patients life and longevity.

Key Medical Advances

Surgical Techniques: Early kidney transplants in the 1950s marked the start of solid organ transplantation.
Immunosuppression: The discovery of effective immunosuppressive drugs in the late 1970s was a critical breakthrough, reducing the rate of organ rejection and making transplantation a more routine procedure.

Post-Transplant Monitoring

After an organ transplant, rigorous post-transplant monitoring helps ensure the long-term viability of the new organ and the patient’s overall health. It is a proactive approach that allows the medical team to promptly identify complications like organ rejection and infection, adjust medications and their doses, and manage the patient’s recovery. Monitoring has traditionally relied on invasive biopsies and blood tests for organ function, but recent molecular diagnostics are beginning to offer minimally invasive, and non-invasive alternatives – which provide valuable information, at the early stages [2-4].

The Purpose of Post-Transplant Monitoring

Prevent and detect organ rejection: The primary goal of post-transplant care is to stop the recipient’s immune system from attacking and damaging the transplanted organ, known as allograft rejection. Monitoring is used to detect early warning signs before irreversible damage occurs.
Balance immunosuppression: Transplant recipients must take immunosuppressive drugs (such as tacrolimus) for the rest of their lives, to prevent organ rejection. Monitoring helps doctors find the right balance, and help to ensure the immunosuppressant dose is high enough to stop organ rejection but not so high that it increases the risk of infection or causes toxicity.
Manage infections: Because immunosuppressive medications significantly weaken the immune system, transplant recipients are at a higher risk of opportunistic infections. Monitoring for viral pathogens like Cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella-zoster virus (VZV), and BK virus, as well as opportunistic bacteria and fungi, is critical to prevent or quickly treat infections.
Improve long-term outcomes: Continuous monitoring is vital for improving patient and graft survival rates over time. By identifying and managing potential issues early, the medical team can help provide personalized treatment and support.

Common Monitoring Methods

Standard Monitoring

Biopsies: For many years, a biopsy of the transplanted organ was commonly used for diagnosing rejection. While highly informative, it is an expensive and invasive procedure with risks like bleeding and infection.
Blood and urine tests: These tests measure the function of the transplanted organ.
- Kidney transplant (which are about half of organ transplants): Monitoring includes checking for creatinine and blood urea nitrogen (BUN) levels. While useful, these indicators can be non-specific and may only reveal damage after it has occurred.
- Liver transplant: Liver function tests measure markers like bilirubin and transaminase levels to detect liver damage.
- Vital signs and patient reporting: Patients are taught to monitor their temperature, blood pressure, and weight daily at home and report any concerning symptoms, which can be early indicators of rejection or infection.

Emerging Molecular and Non-Invasive Methods

Donor-specific antibodies (DSAs): The development of DSAs can predict antibody-mediated rejection. Monitoring for these antibodies is a standard part of post-transplant surveillance in many medical centers.
Donor-derived cell-free DNA (dd-cfDNA): This blood test measures the amount of cell-free DNA from the donor that is circulating in the recipient’s bloodstream. Elevated levels can signal that the transplanted organ is experiencing injury or rejection, frequently before function-based tests show the change.
Gene expression profiling: Blood tests that analyze gene expression may help distinguish between a stable organ and one at risk of rejection.
Urinary exosomes: In kidney transplantation, analyzing exosomes or extracellular vesicles, found in urine can provide a non-invasive way to screen for allograft rejection by examining the mRNA they contain. According to El Fekih 2025 [5], Exosomal mRNA gene signatures identified patients with different stages and classes of kidney rejection, including early stage and significant inflammation, enabling improved decision-making and patient management and may reduce unnecessary biopsies.
Remote patient monitoring (RPM): Using Bluetooth-enabled devices and digital platforms, healthcare teams can remotely track a patient’s vital signs and symptoms. This technology allows for real-time data analysis and earlier intervention, which has been shown to reduce hospital readmissions [6, 7].

The Future of Post-Transplant Monitoring

The field is rapidly evolving toward more personalized and non-invasive monitoring of transplanted organs. Advances in technology, including artificial intelligence and machine learning, are assisting with analysis of complex data from new diagnostic platforms to help improve patient care. By integrating conventional methods with innovative molecular assays, clinicians can achieve a more comprehensive and precise view of a patient’s transplant status, enabling more effective, timely and personalized treatment strategies. This evolution in post-transplant monitoring allows for extended graft survival, and can reduce complications for transplant recipients.