Doctor-Reviewed Health Guides: Conditions, Procedures & Health News

A renal MAG3 scan is a nuclear imaging test that shows how well each kidney works and how urine drains. A radioactive tracer called MAG3 is injected into a vein, and a gamma camera follows it. It helps diagnose blockages and hydronephrosis. It's safe for children and adults and takes about one to two hours.

Keratometry is an eye test that measures the curve of the cornea, the clear front surface of the eye. Its main use is to diagnose astigmatism, and it's also used to fit contact lenses and choose the right lens implant for cataract surgery. A typical cornea measures about 43 diopters. The test is painless and has no risks.

Corneal topography is a painless eye test that maps the shape of the cornea, the clear dome at the front of the eye, using color-coded maps. Nothing touches the eye. It helps diagnose and track astigmatism and keratoconus and is essential for planning LASIK, cataract surgery or a cornea transplant. You may need to stop wearing contacts beforehand.

Fetal heart rate monitoring checks the speed and pattern of a baby's heartbeat during pregnancy and labor to make sure the baby is getting enough oxygen. A normal baseline fetal heart rate is 110 to 160 beats per minute. Monitoring can be external or internal. An abnormal tracing doesn't always mean the baby is in danger.

Lymphangiography (lymphography) is an imaging test that uses injected dye with X-ray or MRI to show the lymphatic vessels and lymph nodes, which regular imaging can't see well. It's used to find lymphatic leaks, evaluate lymphedema, check lymphoma and map lymph vessels before surgery. Your skin, urine and stool may look discolored for a while afterward.

An amylase test is a blood or urine test that measures amylase, a digestive enzyme made by the pancreas and salivary glands that breaks down carbohydrates. It's mainly used to help diagnose and monitor pancreatitis and other pancreas problems. High amylase often points to a pancreas problem but can have other causes, so it's often checked with lipase.

A cardiac PET scan is a nuclear imaging test that uses a small amount of radioactive tracer and a PET scanner to make 3D images showing how well blood flows to the heart muscle and how healthy the muscle cells are. It helps diagnose coronary artery disease. Fast for 4 hours and avoid caffeine for 24 hours beforehand.

A hemodynamic test checks how well the heart pumps and how blood moves through the body, most often to find the cause of fainting (syncope) or a circulation problem. It combines EKG monitoring, blood pressure checks, an echocardiogram and nuclear imaging. Plan for about three hours. It isn't done during pregnancy or breastfeeding.

Retinoscopy is an eye test that uses a handheld light and the reflection from the retina to measure refractive errors, such as nearsightedness, farsightedness and astigmatism, and work out a glasses prescription. Because you don't have to answer questions, it's useful for babies, young children and people who can't communicate easily. It's quick and has almost no risks.

A pathology report is a document written by a pathologist, a doctor who examines tissue and fluid samples under a microscope, describing what they found and giving a diagnosis. For cancer, it includes the tumor type, grade, stage, margins and lymph node findings. Results take a week or longer. Ask your provider about any terms you don't understand.

A core needle breast biopsy is a minimally invasive procedure that uses a hollow needle to remove several small cylinders of breast tissue so a pathologist can check for breast cancer. It's done when a lump is felt or imaging shows something abnormal. The biopsy takes about 15 to 20 minutes. Results usually take 7 to 10 days.

Carrier screening is a genetic test that shows whether you carry a gene change for an inherited condition you could pass to your children. It's done with a blood, saliva or cheek swab sample, ideally before pregnancy. If both partners carry the same recessive condition, each pregnancy has a 25% chance of an affected child.

A bubble study is an ultrasound test that uses bubbles in shaken salt water to show how blood moves through the heart and lungs. It looks for abnormal openings (shunts), most often a patent foramen ovale (PFO). It's often done after an unexplained stroke. If bubbles appear on the left side of the heart, a shunt is likely.

A transcranial Doppler (TCD) is a painless ultrasound test that measures the speed of blood flow in the brain's arteries by sending sound waves through the skull. It helps diagnose and monitor stroke and TIA, narrowed brain arteries and stroke risk in children with sickle cell anemia. The test takes 30 to 60 minutes and uses no radiation.

Ovarian reserve testing estimates how many eggs you have left compared with others your age. It usually combines blood tests for AMH and FSH with an antral follicle count on a transvaginal ultrasound. It's most useful when planning IVF or egg freezing. It doesn't measure egg quality and can't tell you whether you'll get pregnant naturally.

Retinal imaging is a group of tests that use special cameras and scanners to take detailed pictures of the back of the eye, including the retina, macula and optic nerve. It helps detect and track diabetic retinopathy, macular degeneration, glaucoma and retinal detachment. You'll usually get dilating drops, so plan for a ride home.

A liquid biopsy is a blood test that looks for signs of cancer shed by a tumor into the bloodstream. It's mainly used in advanced cancer to track response to treatment and find gene changes that point to targeted therapies. It isn't reliable enough to diagnose cancer on its own; a tissue biopsy remains the gold standard.

Urine cytology is a lab test that looks at cells in the urine to find cancer or precancer cells. It helps detect bladder cancer and other urinary tract cancers and is often ordered for blood in the urine. It's good at finding high-grade cancers but often misses low-grade cancers, so it's used with cystoscopy and imaging.

A heavy metal test measures the levels of potentially toxic metals in the body, most often lead, mercury, arsenic, cadmium and chromium. It's ordered for symptoms of heavy metal poisoning or after a known exposure. It usually uses blood or a 24-hour urine sample. Avoid seafood for 48 hours and imaging contrast for 96 hours beforehand.

Dental impressions are molds or digital scans of the teeth and gums that create an exact copy of the mouth. Dentists use them to plan treatment and make custom-fit crowns, bridges, dentures, aligners and mouthguards. They're taken with putty in a tray or with a handheld scanner. Impressions don't hurt, though putty can trigger gagging in some people.

A ceruloplasmin test is a blood test that measures ceruloplasmin, a protein made by the liver that carries copper through the body. It's mainly used to check for Wilson disease, an inherited condition in which copper builds up in the liver and brain, and to look for copper deficiency. No preparation is needed.

A DHEAS test (DHEA sulfate test) is a blood test that measures dehydroepiandrosterone sulfate, a hormone made mostly by the adrenal glands. It helps check adrenal gland function and find causes of androgen excess. High DHEAS can point to PCOS, congenital adrenal hyperplasia or an adrenal tumor; low DHEAS can point to Addison's disease.

The sweat test (sweat chloride test) is the main test used to diagnose cystic fibrosis (CF). It measures how much chloride (salt) is in the sweat. A chloride level above 60 mmol/L means CF is likely, below 40 means CF is unlikely, and 40 to 60 may need repeat and genetic testing.

A hematocrit (Hct) test is a blood test that measures the percentage of the blood made up of red blood cells. It's part of a routine complete blood count (CBC). Typical adult ranges are about 41–50% for males and 36–44% for females. A low hematocrit can point to anemia; a high one can come from dehydration.