High blood pressure may seem like something that only adults get, after years of smoking, overeating and little exercise. But children can develop it too -- and just as in adults, uncontrolled high blood pressure can pose serious risks to children's hearts, brains and lives.
While medications may help some children with high blood pressure, surgery is the best option for those with renal artery obstructions, causing a rare but especially dangerous form of hypertension. That's the conclusion of a new study published in the Journal of Vascular Surgery by a University of Michigan Cardiovascular Center team that is among the world's most experienced at treating such children.
Called pediatric renovascular hypertension, the disease is caused by narrowings, or stenoses, in the blood vessels that lead to the kidneys.
It's often diagnosed only after children don't respond to blood pressure medications, or after they experience symptoms such as failing to gain weight at a normal pace or having unexplained fatigue. For some kids, the diagnosis comes only after a stroke.
The condition, which is the third most common cause of serious hypertension in children, often develops as a result of developmental narrowings in the renal arteries, the name for vessels that bring blood to the kidneys. In some children, the nearby section of the aorta — the largest blood vessel in the body — also has narrowings. Children who have a genetic disease called neurofibromatosis are especially at risk.
The kidneys play a major role in regulating blood pressure, by filtering waste from the blood and releasing hormones. But if the blood vessels that feed them become narrowed or partially blocked, the kidneys retain fluids and send out a hormone called renin that causes blood vessels throughout the body to constrict, thereby increasing blood pressure.
Fortunately, the new study shows that 97 percent of children who have surgery for renovascular hypertension will respond positively, and 70 percent will be cured completely. In the hands of the right team, the researchers say, children can survive the arduous operation and go on to have a normal life.
"This is a rare condition, but one that can be catastrophic if it's not found and treated appropriately," says lead author James C. Stanley, M.D., a U-M vascular surgeon who has operated on dozens of children with the condition in the past 40 years. "But the good news is that it is highly treatable with the help of an experienced diagnostic, surgical, and medical team."
Stanley, the Handleman Research Professor of Vascular Surgery at U-M and a director of the U-M Cardiovascular Center, co-authored the report with U-M pediatric kidney specialists, interventional radiologists and vascular surgeons who make up the Michigan Pediatric Renovascular Group. Together, they treat children at the clinics, operating rooms and intensive care unit of the C.S. Mott Children's Hospital, as well as U-M Cardiovascular Center diagnostic facilities.
The 97 children analyzed for the study had a total of 162 operations at U-M in the last 43 years. It is the world's largest study of the condition to date. The patients in the study came to U-M from all over the national and the world, referred by their own doctors after multiple medications failed to help.
Stanley and his colleagues use advanced imaging techniques to diagnose the condition, and to guide the surgeons who use deft surgical techniques to reconstruct the narrowed blood vessels which are often only a few millimeters wide. Both minimally invasive angiography techniques, and non-invasive MRI and CT imaging, can be used to assess the condition.
In the paper, the U-M team describes in detail the surgical approach that yielded such high success rates for their patients. Because children are still growing, they cannot be treated using the artificial graft devices and stents that are often used in treating adult kidney blood vessels. As a result, surgeons often have to use a length of blood vessel taken from elsewhere in the child's body to get around the blockage.
In some patients, the persistently high blood pressure has damaged one kidney too much to allow it to be saved, and it must be removed.
Once a child has had surgery to correct their kidney blood flow, they can sometimes go off the blood pressure medications that had been used to try to control their hypertension. But others will still need medicines, or even further surgery, says Stanley.
In addition to improvements in renal hypertension treatment, Stanley has hopes that better blood pressure screening of children will lead to more cases being detected before disastrous consequences arise. He looks back to decades ago, when U-M vascular surgeon William Fry, M.D. was one of the first to report that intractable hypertension in children could be a cause of mental developmental delays — a finding that led to more routine blood pressure testing of children during well-baby doctor visits.
Recent national guidelines call for children to have their blood pressure measured beginning at age 3 - and starting at younger ages for children who were born prematurely or have heart defects. Even if it turns out that a child's high blood pressure is linked to their family history, their obesity or the medications they take for some other condition, children and their parents can take steps to reduce blood pressure through diet, weight loss, and exercise.