Medical Terms & Explanations

Heard a lot of jargon? Find an explanation here for the medical terms you’ve heard from the doctor or read online. If you need a particular acronym explained, click here for list of common kidney transplant-related acronyms.

A ⋅ B ⋅ C ⋅ D ⋅ E ⋅ F ⋅ G ⋅ H ⋅ I ⋅ J ⋅ K ⋅ L ⋅ M ⋅ N ⋅ O ⋅ P ⋅ Q ⋅ R ⋅ S ⋅ T ⋅ U ⋅ V ⋅ W ⋅ X ⋅ Y ⋅ Z


Acronyms & Abbreviations


Acute kidney injury (AKI) – Essentially, a person’s kidneys stop working; this may be temporary or it could become permanent.

Allograft – a medical term for a transplanted organ from a donor.

Antibody – a protein released by white blood cells (part of the immune system) into the blood.  These proteins help the body fight infections and destroy foreign substances in the body. Because a transplanted organ comes from another person’s body, the immune system recognizes it as “foreign” and makes antibodies against the transplanted organ.

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Blood type – there are four major types of blood: type A, type B, type AB, and type O. These types are based on tiny markers on the surface of blood cells. Usually, people can only receive an organ transplant from a donor with the same blood type as them or with a “compatible” blood type. If they don’t have a compatible blood type, a person might still be able to receive a transplant organ from this incompatible donor at certain transplant centers.

A chart of compatible blood types can be found here:

Body mass index (BMI) – a measure of body mass based on height and weight. It is used to estimate the amount of body fat that a person has. A BMI of 18.5-24.9 is considered normal. A higher BMI is considered overweight (BMI 25-29.9) or obese (BMI ≥ 30). A lower BMI is considered underweight (BMI < 18.5).

To calculate your BMI, click here:

Brain death (DBD) – a person is declared brain dead when their brain is no longer functioning at a level considered “alive” and this loss of function is irreversible. There are many tests that are done to ensure that someone is brain dead. These include checking whether a person tries to breathe on their own and checking whether a person has any brain stem reflexes (a type of reflex that goes through brain pathways). There are many other tests that are also used. It is accepted by physicians, members of the clergy, and most everyday people around the world that a person is dead when his or her brain is dead.

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Cardiac death (DCD) – a person is declared dead by cardiac death when their heart stops beating.

Cell – a tiny building block of the human body.  All parts of the human body are made up of cells.

Chronic kidney disease (CKD) – a gradual, irreversible loss of kidney function over time. There are stages of kidney disease based on how much kidney function a person has left. If a person’s kidney function continues to decrease, they may develop end-stage renal disease, also known as kidney failure.

Clinical psychologist – a person who evaluates and cares for the mental and behavioral health of individuals and families. In organ transplantation, either a clinical psychologist or a social worker helps assess patients with kidney failure to see if they would be able to take care of an organ transplant, if they received one. This could include whether they take medications regularly and have social support to help them recover from surgery. Clinical psychologists and social workers also help to evaluate living organ donors, including discussing what is involved in donating an organ and making sure donors have reasonable expectations for their recovery and the recipient’s recovery. After the transplant, clinical psychologists and social workers can also provide support to recipients and living donors.

Cold ischemia time (CIT) – the amount of time that a donor’s organ is out of their body and on ice while it is waiting to be put into the recipient’s body. The term “ischemia” means that the organ is not getting oxygen, because there is no blood being pumped through it. A shorter cold ischemia time usually means the organ will start working faster once it is in the recipient’s body.

Computed tomography (CT) scan – a type of imaging that uses x-rays and allows the medical team to see “slices” of a person’s body. Compared to a normal x-ray image, a CT scan gives more detail. CT scans are also known as CAT scans. You can view an example of a CT scan here.

Creatinine (Cr) – a chemical in the blood that comes mostly from the breakdown of muscles. Creatinine in the blood is filtered out by the kidneys and is used as a marker of kidney function.  When a person’s kidneys aren’t working as well, the level of creatinine in their blood rises.

Cytomegalovirus (CMV) – a virus that commonly affects transplant recipients because their immune systems are weakened by immunosuppression medications. CMV can cause many different types of infections, including infections of the lung, the intestines, and the liver. It can also make organ transplants not function as well. Since many people become infected with CMV without realizing it, all potential transplant donors and recipients are tested for CMV before the organ transplant occurs.

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Deceased donor (DD) – a person who has been declared dead by brain death or cardiac death and whose organs are healthy enough to be used for organ transplant. A single deceased donor can donate multiple organs, including their kidneys (2), liver, heart, and lungs (2).

Delayed graft function (DGF) – when a transplant recipient needs dialysis within the first week (7 days) after transplant. Essentially, the transplanted organ needs extra time to wake up and start working.

Desensitization – another name for plasmapheresis. Using a machine similar to a hemodialysis machine, antibodies are removed from a person’s body to lower the chance that they will reject an organ transplant.

Diabetes mellitus (DM) – often just called diabetes, this is when a person’s body can’t react properly to sugar in the person’s blood.  Usually, a person’s pancreas will release insulin which allows their cells to pull sugar out of their blood to use for energy. In a person with diabetes, either the pancreas can’t produce insulin (Type I) or the body doesn’t respond properly to insulin (Type II). As a result, the person’s blood sugar doesn’t stay at normal levels. Diabetes mellitus is one of the top causes of chronic kidney disease and end-stage renal disease.

Dialysis – a method of filtering the blood outside of the body that tries to mimic what healthy kidneys would do. This includes removing extra fluid from the blood (which would usually leave the body as urine) and also balancing the chemicals (electrolytes) in the blood. There are two types of dialysis: hemodialysis and peritoneal dialysis.

Dialysis catheter – a tube that is placed into a person’s vein (a type of blood vessel). Within the catheter are two smaller tubes: one is used to pull blood out of the person’s body (where it can then go to a hemodialysis machine) and the other is used to return blood to the person’s body after it has been filtered.

Dialysis fistula – A surgeon connects an artery and a vein during surgery to form a dialysis fistula. Arteries carry blood away from the heart to the rest of the body, so that it can deliver oxygen; veins carry blood from all over the body back to the heart. When an artery and a vein are connected, the blood in that area flows in a different pattern. Over time, this makes the part of the blood vessel around this connection grow larger. A dialysis fistula is usually made when a person needs long-term hemodialysis (for more than a few weeks or months). The needles for hemodialysis are placed in the dialysis fistula.

Donor – In transplant, the donor is the person whose healthy organ is taken out and used for the transplant surgery. There are both deceased donors and living donors.

Donor service area (DSA) – a geographic region in the United States in which a local organization facilitates deceased-donor organ transplants. The United States is split into 58 DSAs, and the organizations that manage them are called organ procurement organizations (OPOs). Each hospital is within one of the 58 DSAs. If a potential deceased donor is identified by a hospital, they notify the OPO that oversees their DSA.

Donor-specific antibody (DSA) – antibodies that a person forms against specific HLA antigens. If a recipient has donor-specific antigens against a living donor, the transplant team may try to get rid of them before the transplant using treatments like plasmapheresis.

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End-stage renal disease (ESRD) – the medical term for kidney failure. A person with end-stage renal disease needs help filtering their blood (from dialysis or a kidney transplant) in order to stay alive.

Estimated post-transplant survival (EPTS) – a score that is calculated for all adults waiting for a kidney transplant that predicts how long a person’s transplant is likely to last. The lower the EPTS score, the longer the transplanted kidney is expected to function. The EPTS score is based on a person’s time on dialysis, age, and whether they have diabetes or have already had an organ transplant in the past.

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Glomerular filtration rate (GFR) – a measurement of how well the kidneys are working. This is usually estimated using a patient’s creatinine level, which is measured on a blood test, as well as their age, sex, race, and certain other characteristics.

Graft – another name for a transplanted organ.

Graft failure – when a transplanted organ (or graft) stops working. This can happen suddenly or it can happen slowly over time. This is also called “graft loss”.

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Hemodialysis (HD) – a type of dialysis that uses a dialysis fistula or a dialysis catheter to get access to a patient’s blood. The patient’s blood is run through a machine and then returned back into the patient’s body. The machine acts like an artificial kidney and filters the blood, but it does not perform other functions of the kidney. See Kidney Basics for more information on the many functions of the kidney.

Hemoglobin A1C (HbA1c or A1C) – an estimate of how well-controlled a person’s blood sugar has been over the past three months. This is a common test for patients with diabetes.

Hepatitis C virus (HCV) – a virus that mostly affects a person’s liver. Unlike other viruses that harm the liver, hepatitis C usually causes chronic (long-term) liver problems rather than an acute (sudden-onset) illness. After many years, HCV can cause scarring in a person’s liver, called cirrhosis. All potential organ donors are tested for HCV before they can donate an organ.

Human immunodeficiency virus (HIV) – a virus that infects a person’s immune system. If the HIV infection causes a lot of damage to the person’s immune system, they can develop Acquired Immunodeficiency Syndrome (AIDS). All potential organ donors are tested for HIV before they can donate an organ.

Human leukocyte antigens (HLA) – proteins on the surface of white blood cells (the cells in the body that fight infection). These help determine how closely two people “match”. For more information about matching, see Compatibility.

Hypertension (HTN) – a medical term for high blood pressure.  This is when the blood in a person’s blood vessels (the tubes that transport blood around the body) are under a higher than normal pressure. This puts a person at a higher risk for kidney damage and strokes. If a person has hypertension for many years, they can develop chronic kidney disease and eventually end-stage renal disease.

Hypotension – a medical term for low blood pressure. This is when the blood in a person’s blood vessels (the tubes that transport blood around the body) is at a lower pressure than normal. If a person’s blood pressure is too low, not enough blood and oxygen get to their organs, including their brain. When this happens, a person’s organs stop working normally, so it is important to increase their blood pressure to normal as quickly as possible.

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Immune system – the body system that protects us against foreign substances. Usually, these foreign substances are bacteria, viruses, or parasites that cause infections. However, the immune system also recognizes organ transplants as “foreign” and can attack the transplanted organ. When you hear about white blood cells and antibodies, these are part of the immune system.

Immunosuppression – the process of making a person’s immune system weaker than normal. Some people become immunosuppressed because of infections such as HIV or as a side effect of cancer treatments. After an organ transplant, transplant recipients take medications that weaken their immune system so they don’t reject their new organ.

Incompatible – this means that some of the tiny markers on the surface of a donor’s cells don’t match some of the markers on a recipient’s cells. This may be due to different blood types, HLA types, or other marker mismatches. A recipient may also have antibodies to some of the markers on a donor’s cells, which can increase the risk of organ rejection after a transplant. Essentially, people are incompatible if there is a high chance that the recipient’s body will notice that there is someone else’s organ inside of it. The chance of the body rejecting a transplanted organ increases as people have more mismatches, because these are clues for the body that something doesn’t belong there.

Incompatible kidney transplant – an organ transplant from a living donor to a recipient, despite the fact that they are incompatible. In order for this transplant to succeed, the recipient has an extra treatment in preparation, usually something called plasmapheresis/desensitization, and receives extra immunosuppression after the transplant. For more about different types of living donor kidney transplants, including incompatible transplants, see our Types of Living Donor Kidney Transplants page.

Independent living donor advocate (ILDA) – The role of the ILDA is to promote the best interest and to advocate for the rights of the living donor. All donors will meet with the ILDA. The ILDA will assist the living donor in understanding information regarding the informed consent and evaluation process, the surgical procedure, medical and psychosocial risks and the benefit and need for follow-up in six months, one year, and two years post-donation.

Induction therapy – a combination of immunosuppression medications given to a transplant recipient immediately after the transplant to reduce the risk of rejection. In other words, when an organ is first put into a recipient’s body, there is a high risk that the body will recognize the new organ as being foreign. Induction therapy uses higher doses of strong immunosuppressive medications to try and prevent rejection. After a period of induction therapy, a transplant recipient is switched to maintenance therapy.

Intravenous (IV) – in a vein. Usually, this term is used when a needle is placed into a vein to deliver fluids or medicines. The nurse might say that a person is receiving these fluids or medicines “IV”, or through their vein. In some cases, a person might receive a contrast dye IV before getting a CT scan.

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Kidney Allocation System (KAS) – a revised system used since December 2014 to determine how deceased-donor kidneys are distributed to recipients. KAS was designed to give people more equal access to kidney transplants.

For more information on KAS, click here:

Kidney donor profile index (KDPI) – tells you how long a deceased donor kidney is expected to function relative to all of the kidneys recovered in the US in the last year.

Kidney donor risk index (KDRI) – combines donor factors to summarize the risk of graft failure after kidney transplant into a single number

Kidney transplant (KT) – a surgery where a kidney from one person (either a deceased donor or a living donor) is put into another person with end-stage renal disease (kidney failure). The recipient will need to take medications called immunosuppressants because the kidney is from another person’s body. If the recipient was on dialysis before the transplant, they can stop dialysis after a successful kidney transplant.

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Living donor (LD) – A person who is alive when they donate an organ, usually a kidney or a part of their liver. Living donors are healthy and undergo a lot of medical tests before they are allowed to donate an organ.

Living kidney donation – A kidney transplant where the kidney comes from a living donor.

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Magnetic resonance imaging (MRI) – a type of image produced using a magnetic field. Images produced from an MRI scan give a lot of detail about soft tissues like a person’s brain and intestines (“guts”). MRI scans take longer than CT scans but do not use any radiation. Click here for an example of an MRI.

Maintenance therapy – the combination of immunosuppression medications that a transplant recipient takes long-term to prevent organ rejection.

Matching – how many of the little markers on a person’s cells match the markers on their donor’s cells. This includes blood type, HLA type, and other markers. The closer the match between a donor and recipient, the less likely the recipient is to reject the transplant.

Model for End-Stage Liver Disease (MELD) – a score used to prioritize who gets a liver transplant. It is calculated based on several laboratory tests of a person’s blood, including their creatinine, bilirubin, and INR. In the last few years, the calculation of MELD score has been revised and now includes a person’s sodium level.

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Nephrectomy – surgery to take out one kidney, as is done in living kidney donation.

Nephrologist – a physician (medical doctor) who studies and treats kidney disease. In short, a “kidney doctor”.

Nephrology – the branch of medicine that involves studying the kidneys and treating kidney diseases.

Non-directed donor – a person who wants to donate a kidney but does not have a specific recipient in mind. These donors work with a transplant center to find a recipient. Non-directed donors choose whether or not they want to meet their recipient. Non-directed donors have also been called anonymous donors or altruistic donors.

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Organ procurement organization (OPO) – an organization that facilitates deceased-donor organ transplants within its local region, or donor service area (DSA). The United States is split into 58 DSAs, so there are 58 OPOs that manage these regions. When a hospital identifies a potential deceased donor, they contact their OPO.

Oxygen – the part of the air that we breathe that is needed by the body. Oxygen is used by the body as it makes energy out of the food we eat. We breathe in oxygen and breathe out carbon dioxide.

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Paired kidney donation (PKD) – also known as a paired kidney exchange, this is when two or more living donorrecipient pairs swap donor kidneys so that the recipients can get the best-matched kidney possible. In other words, if donor A wanted to give to recipient B and donor C wanted to give to recipient D, but both pairs were incompatible, donor A could give to recipient D and donor C could give to recipient B. (A ⇒ B and C ⇒ D becomes A ⇒ D and C ⇒ B).

Panel reactive antibody (PRA) – a measure of how sensitized a person is. This is measured on a scale of 0-100% and represents what percent of donors they are incompatible with (based on HLA matching). A person with a 0% PRA can receive any organ of a compatible blood type, while a PRA of 99% means that only 1% of organs are likely to work for that recipient.

Peritoneal dialysis (PD) – a type of dialysis that requires a tube (peritoneal dialysis catheter) placed through the skin into a patient’s belly. Fluid is put into the patient’s belly, where it helps to filter out waste products that would normally be removed by the kidney. In some cases, a machine is used to cycle fluid into and out of the patient’s belly, often overnight while they sleep.

Plasmapheresis – a process similar to hemodialysis in which blood is taken out of the body, filtered, and put back into the body. However, the part of the blood that is filtered out is different in plasmapheresis than in hemodialysis. In plasmapheresis, the machine filters out antibodies, which are a part of the person’s immune system. Plasmapheresis helps to desensitize a patient. This reduces the likelihood that a person will reject an organ transplant from a donor who is incompatible.

Preemptive kidney transplant – a kidney transplant that is performed before the recipient has to start dialysis.

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Recipient – In transplant, the recipient is the person whose organ is not working and who needs a new organ. The recipient gets a new organ from a donor.

Rejection – when a transplant recipient’s body recognizes the transplanted organ (or graft) as a foreign thing and attacks it. The body recognizes the transplanted organ as something that shouldn’t be there because of markers on the surface of the organ’s cells that do not match the markers in the rest of the recipient’s body. Acute rejection is when the body suddenly mounts a big attack on the transplanted organ. Chronic rejection is when the body slowly damages the transplanted organ over time. Both of these can result in graft failure.

Renal – indicates that something is related to the kidney. For example, “renal failure” means failure of the kidney to work properly.

Renal replacement therapy (RRT) – another name for dialysis.

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Sensitized – when a recipient has antibodies that may make it difficult for them to receive a transplant. This is because they will be incompatible with many donors. Essentially, recipients who are sensitized are more likely to reject certain organs, so we don’t want to give them those organs. Instead, we try to find an organ that they are less likely to reject, so that their transplant works for a long time. However, this can limit the pool of organs that they can receive, so they may wait longer for an organ transplant.

Social worker – a member of the transplant team who works with recipients and living donors before and after transplant. The social worker helps to create a plan for how the transplant will fit into a recipient’s or donor’s life, including helping patients find financial support, figure out who will care for them as they recover from surgery, determine how they will get medications and if they need help paying for them, and much more. In addition, either a social worker or clinical psychologist helps assess patients with kidney failure to see if they would be able to take care of an organ transplant, if they received one. This could include whether they take medications regularly and have social support to help them recover from surgery. Social workers and clinical psychologists also help to evaluate living organ donors, including discussing what is involved in donating an organ and making sure donors have reasonable expectations for their recovery and the recipient’s recovery. After the transplant, social workers and clinical psychologists can also provide support to recipients and living donors. The social worker may also act as the independent living donor advocate (ILDA) on the transplant team.

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Transplant – a surgery where an organ is taken from one person’s body and put into another person’s body. The transplanted organ is sometimes called a “graft”.

Transplant center – a hospital where experienced surgeons perform organ transplants.

Transplant team – a group of healthcare professionals including surgeons, nurses, physician’s assistants (PAs), coordinators, social workers, and other members who make sure that the evaluation process, surgery, and recovery are safe and successful.

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Ultrasound – an image produced using sound waves. This is the same type of imaging that is done to see a baby in a pregnant woman’s belly, although it is often called a sonogram in those situations. Usually, some jelly is put on a person’s skin and a probe (a rubber rectangle with a flat end) gets placed against the skin. This probe emits sound waves, although you can’t hear them. Unlike other imaging types, ultrasound shows you an image in real time, meaning you can see blood flow and organs move. Ultrasound does not use any radiation. For an example of an ultrasound click here.

United Network for Organ Sharing (UNOS) – a national organization that oversees organ transplantation and organ donation in the United States. This includes managing the national transplant waiting list, matching donors and recipients, and managing the database where transplant patients’ information is recorded. UNOS also helps to educate both healthcare providers and the public about organ transplantation.

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Common Acronyms

A1C – short for Hemoglobin A1C

AKI – acute kidney injury

BMI – body mass index

CIT – cold ischemia time

CKD – chronic kidney disease

CMV – cytomegalovirus

CPRA – calculated panel reactive antibody

Cr – creatinine

CT – computed tomography (scan)

DBD – donation after brain death

DCD – donation after cardiac death

DD – deceased donor

DGF – delayed graft function

DM – diabetes mellitus

DSA – donor service area or donor-specific antibody

eGFR – estimated glomerular filtration rate

EPTS – estimated post-transplant survival

ESRD – end-stage renal disease

GFR – glomerular filtration rate

HCV – hepatitis C virus

HD – hemodialysis

HIV – human immunodeficiency virus

HLA – human leukocyte antigen

HTN – hypertension

ILDA – independent living donor advocate

IV – intravenous

KAS – kidney allocation system

KDPI – kidney donor profile index

KDRI – kidney donor risk index

KT – kidney transplant

LD – living donor

MELD – Model for End-Stage Liver Disease

MRI – magnetic resonance imaging

OPO – organ procurement organization

PD – peritoneal dialysis

PKD – paired kidney donation, also known as “kidney exchange” or “kidney swap”

PRA – panel reactive antibody

RRT – renal replacement therapy

UNOS – United Network for Organ Sharing

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