Your child’s doctor will try to find out what is causing their hypertension, and how severe it is.

Hypertension may be primary or secondary.

Primary hypertension

Sometimes there is no known cause of hypertension. This is called primary hypertension or essential hypertension. It is more common in adults than children and is usually linked to eating a high-salt diet or being overweight. There are often no early symptoms.

Secondary hypertension

Sometimes hypertension is caused by another condition, often affecting the kidneys. This is called secondary hypertension. It is more common in children than adults.

Some causes are short-term and can get better with treatment. Others are long-term conditions that need ongoing care.

Short-term causes include:

• a urinary tract infection (UTI) - germs (usually bacteria) get into the urine and travel into the urinary system. In serious cases, this infection can travel into the kidney. This is called pyelonephritis.
• glomerulonephritis - a group of conditions where the kidney filters (glomeruli) are damaged or inflamed (swollen)
• a side-effect of some medicines, such as a high dose of steroids
• a problem with the endocrine system (the glands that control many of the body's functions)

Long-term causes include:

• chronic kidney disease (CKD) - damaged kidneys cannot remove enough water and salt from the body
• renal scarring - damage to the kidneys, often from previous urinary tract infections that reached the kidney. Scarring can raise blood pressure over time
• problems in the urinary system that a child is born with, where one or more parts do not develop or grow normally. These include:
  • Posterior urethral valves – a blockage in the back part of the urethra nearest the bladder in some boys
  • Posterior urethral valves – a blockage between the kidney and the ureter
  • Vesicoureteric reflux (VUR) and reflux nephropathy – when urine backs up towards the kidneys
  • Renal dysplasia – one or both kidneys do not form properly
  • Renal hypoplasia – one or both kidneys are smaller than normal
• cystic kidneys - where fluid-filled sacs called cysts form in the kidney. These are not cancerous. Conditions that cause cystic kidneys include
  • autosomal recessive polycystic kidney disease (ARPKD)
  • autosomal dominant polycystic kidney disease (ADPKD)
  • multicystic dysplastic kidney
• renovascular disease - a problem with the blood vessels that carry blood to the kidney