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PH words and terms to know

Find definitions and explanations for some of the technical terms and concepts that you may come across when learning about PH on this site or discussing it with your healthcare provider.

504 plan

A 504 plan requires any United States school that receives federal funding to accommodate the needs of any child with a physical or mental impairment that affects major life activities. A 504 plan is unique to each child’s situation. For children with PH, accommodations might include excused bathroom breaks or trips to the drinking fountain.
504 plans for PH


ACR stands for albumin-to-creatinine ratio. Your ACR may be measured in a urine test as a way to look for high levels of albumin (a type of protein), which is a sign of kidney damage.

AGT (enzyme)

An enzyme found in the liver. In someone with PH1, this enzyme is either missing or doesn’t work correctly.

AGXT (gene)

The gene that provides instructions for making the liver enzyme AGT. PH1 is caused by mutations to this gene.


A condition in which you have a low number of red blood cells. Blood cells carry oxygen to your body’s tissues, so when you have a low number of red blood cells, your body’s tissues get less oxygen. Having anemia can make you feel tired and weak.

Calcium oxalate

A substance that is made up of a combination of oxalate and calcium. Calcium oxalate crystals form in the kidneys when there is an overabundance of oxalate. These crystals can deposit in kidney tissue (a condition called nephrocalcinosis, or calcification of the kidney) and can also clump together to form kidney stones.


A disease of the heart muscle that makes it harder for your heart to pump blood to the rest of your body. Cardiomyopathy can lead to heart failure.


Certain inherited diseases, such as PH, occur when an individual inherits 2 mutated copies of a particular gene—1 mutated copy from each parent. Individuals who inherit 1 mutated copy of the gene and 1 functional copy of the gene are called carriers. Although carriers may not show signs or symptoms of the disease, they can still pass on the mutated copy of the gene to their children.
How PH runs in families

Chronic kidney disease (CKD)

CKD is a condition in which kidney function gradually declines over time.

CKD is divided into stages based on how well your kidneys are functioning. Your kidney function is measured by testing something called estimated glomerular filtration rate, or eGFR. If your eGFR number is low, your kidneys are not working as well as they should. Ranges for eGFR by CKD stage are listed below, but note that ranges will differ based on your age, gender, race, and other factors.

There are 5 stages of chronic kidney disease:

Stage 1

Kidney damage with normal kidney function, eGFR of 90 or higher

Stage 2

Kidney damage with mild loss of kidney function, eGFR of 60 to 89

Stage 3a

Mild to moderate loss of kidney function, eGFR of 45 to 59

Stage 3b

Moderate to severe loss of kidney function, eGFR of 30 to 44

Stage 4

Severe loss of kidney function, eGFR of 15 to 29

Stage 5

Kidney failure, eGFR less than 15

Clinical trial

Clinical trials are research studies using human volunteers (also called participants), which are conducted to learn more about the treatment, diagnosis, and/or prevention of diseases or conditions. In some clinical trials, participants may receive a specific treatment for a specific disease or condition. The researchers try to determine how safe the drug is and how well it works. For example, investigators may give a drug to participants who have high blood pressure to see whether the drug lowers their blood pressure.
US clinical trials in PH

CT scan/CAT scan

A procedure that uses a computer linked to an x-ray machine to create a 3-dimensional view of tissues and organs, such as the kidneys. It is also called a computed tomography scan.


A treatment that filters wastes, including oxalate, and extra fluid from your blood when your kidneys have lost most of their ability to do the job themselves. There are 2 types of dialysis: hemodialysis and peritoneal dialysis.

Learn more about dialysis from the National Institutes of Health or the American Association of Kidney Patients.


eGFR stands for “estimated glomerular filtration rate.” Your eGFR is a measure of how well your kidneys are doing their job of filtering out wastes. Measuring your eGFR is the best way to figure out how well your kidney is functioning and to determine your kidney disease stage.


Enzymes are proteins that turn one substance into another. When an enzyme is missing or not working correctly, too much of one of these substances will often build up.

Extracorporeal shock wave lithotripsy

Also called ESWL, this is a nonsurgical technique for treating stones in the kidney or ureter (the tube going from the kidney to the bladder) using high-energy shock waves. Stones are broken into fragments that are small enough to pass out of the body in urine.

Although it is still often used, some sources suggest that ESWL may not be the preferred
treatment for people with PH. This is because PH kidney stones are harder than other kinds of kidney stones, so they are not broken up as well with ESWL. Because of this, ESWL could leave larger fragments behind, which can grow into new kidney stones. Finally, ESWL can have a low success rate for removing stones in children.

Learn more about ESWL from the National Kidney Foundation.

Gastronomy tube

Also called a G-tube, this is a tube that is surgically placed in the abdomen to allow direct access to the stomach for supplemental hydration, feeding, or medication.

Learn more about G-tubes from the Children’s Hospital of Philadelphia.

Gene mutations

Mutations are alterations in the DNA sequence of a gene. As a result of these changes, the mutated gene has the wrong DNA instructions and either can’t make proteins or makes proteins that don’t work correctly.


Genes are pieces of DNA that contain instructions for building the proteins that make up everything in your body, from enzymes to cells to organs. Genes pass from parents to offspring.

Genetic carrier

See carrier


A substance that the liver makes during the process of metabolism.

GRHPR (enzyme)

An enzyme found in the liver. This enzyme is missing in someone with PH2.

GRHPR (gene)

The gene that provides instructions for making the liver enzyme GRHPR. PH2 is caused by mutations to this gene.


A treatment that filters wastes, including oxalate, and water from your blood that is needed when your kidneys can no longer do the job of filtering on their own. During hemodialysis, your blood goes through a filter, also called a dialyzer or “artificial kidney,” outside your body. The dialysis machine pumps blood through the filter, removes wastes from your blood, and returns the filtered blood to your body.


Passed on from parent to offspring via genes.

HOGA (enzyme)

An enzyme found in the liver. This enzyme is missing in someone with PH3.

HOGA1 (gene)

The gene that provides instructions for making the liver enzyme HOGA. PH3 is caused by mutations to this gene.


A condition in which there is too much oxalate in a person’s urine. (Hyper means too much, oxal stands for oxalate, and uria stands for urine.)

Hyperoxaluria can have different causes. Primary hyperoxaluria has a genetic cause, while secondary hyperoxaluria can be caused by excess oxalate from the diet or gastrointestinal disease.


See hereditary

Kidney failure

An advanced stage of chronic kidney disease, defined as when your kidney is functioning at less than 15% of normal function. People in this advanced stage of kidney disease need dialysis or a kidney transplant. Sometimes kidney failure is also called renal failure or end-stage kidney disease.

Get more information about kidney failure.

Kidney stone

Hard deposits made of minerals and salts that form inside your kidneys. Kidney stones can affect any part of your urinary tract, from your kidneys to your bladder. Kidney stones are also sometimes called renal calculi, nephrolithiasis, or urolithiasis.

Lactate dehydrogenase (LDH)

A protein (enzyme) found in the liver that converts excess glyoxylate into oxalate.


The process by which your body breaks down what you eat and drink through chemical reactions, converting it into energy.


Related to the kidneys. For example, a nephrologist is a type of healthcare provider who specializes in diseases and conditions that affect the kidneys, and nephrolithiasis is another word for kidney stones.


A condition in which calcium builds up in the kidneys, causing them to harden; in PH, this is caused by deposits of calcium oxalate crystals. Although nephrocalcinosis itself may or may not have signs and symptoms, these calcium oxalate deposits cause kidney damage, inflammation, and infection, reducing the kidney’s filtering ability and leading to a decline in kidney function.


Another word for kidney stones.


A healthcare provider who specializes in diagnosing and treating disorders of the kidneys.


Oxalate is a naturally occurring molecule found in plants and humans. It’s not a required nutrient, has no known function in humans, and is usually filtered out by the kidneys and leaves the body in the urine as a waste product. When the kidneys fail to filter out enough oxalate, it can build up, causing kidney stones and kidney damage.

Percutaneous nephrolithotomy

Also called PCNL, this is a kidney stone removal procedure that involves using instruments to access the kidney through a small incision in the back. This procedure is usually used for larger kidney stones.

Learn more about percutaneous nephrolithotomy from the National Kidney Foundation and the Cleveland Clinic.

Peritoneal dialysis

A treatment for kidney failure that uses the lining of your abdomen, or belly, to filter your blood inside your body. A healthcare provider will surgically place a plastic tube into the abdomen before beginning treatment. During the treatment, the abdominal area is slowly filled with a liquid called dialysate through this tube. Extra fluid and waste products, including oxalate, are drawn out of your blood and into the dialysate.

Primary hyperoxaluria

Primary hyperoxaluria, or PH, is a family of rare genetic disorders in which the liver produces too much oxalate, which can then cause kidney stones, kidney damage, and, in some cases, damage to other organs.


Another term for vitamin B6.

Rare disease

A disease affecting fewer than 200,000 people in the United States.


Related to the kidneys.

RNAi therapy

Also called RNA interference therapy, this is a treatment that interferes with messenger RNA, the chemical messengers in your cells that give instructions for making proteins. By interfering with messenger RNA, RNAi treatments prevent these proteins from being made. RNAi therapy is often confused with gene therapy but differs both in how it works and how long it lasts: RNAi therapy is reversible, while gene therapy (the permanent modification of DNA) can be permanent. An RNAi therapy for PH1 has been approved by the US Food and Drug Administration. RNAi therapy is also being investigated in PH2 and PH3.

Systemic oxalosis

A condition that occurs when the kidneys lose their ability to filter out enough oxalate and other substances that are harmful to the human body. When this happens, calcium oxalate crystals travel to other tissues, such as the heart, bones, retina, and skin, where they can cause additional damage.


The duct or tube that connects the kidney to the bladder.


Also known as URS, this is a kidney stone removal procedure that uses small instruments to gain access to the stone via the ureter (the tube connecting your kidney to your bladder). The instruments are then used to grab the stone and pull it free. If the stone is large, it may be broken up first into smaller pieces.

Learn more about ureteroscopy from the National Kidney Foundation and the Cleveland Clinic.


When stones occur anywhere in the urinary system, including the kidneys and bladder.


A healthcare provider who specializes in diagnosing and treating disorders of the urinary tract.

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