High blood pressure, or hypertension, is caused by different things in children than in adults -- and is far less common.

First of all, it's important to be sure that the child really has hypertension. If too small a cuff was used, it can give a reading that's higher than the actual blood pressure. This happens often. Most pediatricians' offices have several different cuff sizes.

If the correct cuff was used, and the child's blood pressure really is high (the norms vary by age), then the most common causes in the 1- to 6-year age group are:

• Kidney disease
• Renovascular disease, a problem with the blood vessels of the kidney
• Endocrine problems, such as thyroid disease or pheochromocytoma (a tumor that produces excess adrenalin-like chemicals)
• Coarctation of the aorta, a birth defect of the major artery coming out of the heart
• Essential hypertension -- this is the kind most common in adults. It's quite rare in children, unless they are obese or have a family history of high blood pressure.

High blood pressure can also be caused temporarily by stress or anxiety. On occasion, a medication, such as Sudafed, will raise blood pressure. Hypertension can also be caused by drinking caffeinated beverages.

Generally, if the blood pressure is a little high the doctor will check it again to be sure. If it stays high, your child's doctor will likely pursue a diagnostic evaluation looking for signs of the above conditions. This will include a detailed history, physical exam, and blood tests. It may also include an ultrasound of the kidney or echocardiogram of the heart.