Organ Transplant – Indications, Lab Tests, and Medications

What is Organ Transplantation?

Organ transplantation is a surgical procedure that involves replacing a failed organ with a healthy organ donated by another individual.  Organ transplantation is often reserved as a last resort therapeutic option in certain individuals with end-stage organ disease.  It is generally an option for individuals that have a life expectancy of 10 or more years.  Patients frequently have to undergo a series of laboratory tests, including screening for infectious diseases (e.g., HIV, CMV, hepatitis B and C, tuberculosis) and other conditions before being considered a transplant candidate.  Individuals are also commonly tested for illicit drug use and screened for coexisting psychological disorders such as suicidality.

Patients that meet the criteria are placed on a transplant list and often establish medical care at a tertiary referral hospital.

What are the Indications for Organ Transplant?

Organ transplantation is indicated in individuals with end-stage organ disease that meet certain criteria.  Solid organs that are commonly transplanted include the heart, lungs, liver, pancreas, and kidney.  As medicine advances, other organs are beginning to be transplanted, such as the uterus.  Bone marrow transplant is an example of a non-solid organ transplant.

Patients with advanced heart disease such as cardiomyopathy and congestive heart failure are often “bridged” to heart transplantation.  These individuals may receive chronic home infusions of pressor medications to help keep their blood pressure elevated and organs perfused until a heart is available. Your cardiac surgeon will occasionally recommend a surgical placement of a left ventricular assist device (LVAD).

Patients with end-stage kidney disease are also often bridged to kidney transplantation.  They typically receive a hemodialysis catheter or arteriovenous fistula to undergo dialysis three times per week.  Dialysis machines act like the kidneys by filtering blood and balancing fluid and electrolyte levels.

Patients receiving lung transplantation often have respiratory failure and require continuous oxygen therapy.  Occasionally, these individuals need assisted ventilation with a breathing machine (mechanical ventilation).  Individuals with cirrhosis and end-stage liver disease are typically managed with medications to treat liver disease symptoms and complications.  They frequently receive therapeutic paracentesis and occasionally require a TIPS procedure before liver transplantation.  Those with fulminant liver failure typically require urgent liver transplantation.

What are Laboratory Tests Ordered in Organ Transplant Recipients?

Commonly ordered blood tests in transplant recipients typically include a CMP (comprehensive metabolic panel), CBC (complete blood cell count), and thyroid function studies (TSH, free T4).  A urine analysis, pregnancy test (in women of reproductive age), and urine drug screen are also normally obtained.  Urine is also sent for bacterial culture.  Your doctor may order blood tests evaluating for exposure to certain viruses such as human immunodeficiency virus (HIV), cytomegalovirus (CMV), and viral hepatitis (types A, B, and C).  They will also test for tuberculosis with a purified protein derivative (PPD) skin test, serum quantiferon, and chest x-ray.

Imaging is obtained in patients undergoing an organ transplant as well.  The type of imaging and body part being imaged depends on the specific organ being transplanted.  For example, individuals undergoing a cardiac transplant frequently receive an echocardiogram (ultrasound of the heart) and CT scan of the chest.  They also usually receive an electrocardiogram (EKG) and undergo physiologic studies such as pulmonary function tests and stress tests.  Your cardiologist will often perform a right and left heart catheterization to measure various hemodynamic parameters before surgery.

What are the Complications of Organ Transplant?

Organ transplant recipients are at increased risk of infection due to the immunosuppressive nature of the treatment.  Individuals can develop common viral or bacterial infections, but these infections may be more severe and complicated than infected individuals with competent immune systems.  Patients can also develop nosocomial infections in the hospital due to organisms such as Methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa.  This is particularly problematic in patients with prolonged hospitalization or those requiring mechanical ventilation.

Furthermore, patients on immunosuppressive therapy are susceptible to rare (opportunistic) infections that individuals with intact immune systems do not ordinarily suffer.  Potential organisms include fungal infection such as Aspergillus and Candida species.  Patients may also develop PJP (Pneumocystis jiroveci pneumonia), life-threatening pneumonia characterized by severe hypoxemia (low blood oxygen levels), and difficulty breathing.  Patients with PJP often require endotracheal intubation and mechanical ventilation.  Cytomegalovirus (CMV) is another potential opportunistic organism that can lead to colitis (inflammation of the colon) and retinitis (inflammation of the retina), the latter of which can result in blindness.

Patients receiving immunosuppressive therapy are also at risk of developing certain cancers such as skin cancers, squamous cell carcinoma of the eye, anogenital cancers, lung cancer, Kaposi sarcoma, and lymphoproliferative disorders.

What Medications are Commonly Prescribed for Organ Transplant Recipients?

Transplant recipients are typically treated with immunosuppressive agents as well as antibiotics for prophylaxis against opportunistic infection.  Prophylactic antibiotics often include Bactrim (trimethoprim-sulfamethoxazole) for prophylaxis against Pneumocystis pneumonia (PJP), as well as Listeria monocytogenes and Toxoplasma gondii.  Cytomegalovirus prophylaxis is typically achieved with intravenous Cytovene (ganciclovir) or Valcyte (oral valganciclovir).  Prophylaxis against herpes simplex and varicella-zoster infection is typically accomplished with Zovirax (acyclovir) or Valtrex (valacyclovir).  Occasionally, individuals receive antifungal medications for prophylaxis against fungal infections due to Aspergillus, Histoplasma, or Candida species.

Immunosuppressive therapy typically consists of a 2-3 drug regimen consisting of a calcineurin-inhibitor (e.g., cyclosporine or tacrolimus), an antimetabolite (e.g., mycophenolate mofetil), and corticosteroids that are slowly tapered over a year.  Here are the most commonly used agents:

•         Corticosteroids such as Deltasone (oral prednisone)
•       Imuran (azathioprine)
•         Cellcept (mycophenolate mofetil)
•       Neoral (cyclosporine)
•       Prograf (tacrolimus)
•       Afinitor (everolimus)
•       Rapamune (sirolimus)
•         Nulojix (belatacept)

References:

1.     Hart A, Smith JM, Skeans MA, et al. Kidney. Am J Transplant 2016; 16 Suppl 2:11. - https://www.ncbi.nlm.nih.gov/pubmed/26755262
2.     Danziger-Isakov L, Kumar D, AST Infectious Diseases Community of Practice. Vaccination in solid organ transplantation. Am J Transplant 2013; 13 Suppl 4:311. -  https://www.ncbi.nlm.nih.gov/pubmed/23465023
3.     Fishman JA. Infection in solid-organ transplant recipients. N Engl J Med 2007; 357:2601. - https://www.nejm.org/doi/full/10.1056/NEJMra064928
4.     Penn I. Cancers complicating organ transplantation. N Engl J Med 1990; 323:1767. - https://www.nejm.org/doi/full/10.1056/NEJM199012203232510