It doesn’t seem possible that high blood pressure numbers can damage kidneys. But the way kidneys work can give you an understanding of the reason.
Below is an infographic explaining the important filtration parts of the kidneys–nephrons.
In the kidneys, the delicate structures called nephrons are filtering wonders. The blood moves into the capillaries of the kidneys and into part of these structures called glomerulus, a cluster of capillaries. Surrounding this cluster is a two layer sac called a Bowman’s capsule which is really a part of the tubule. Ultrafiltration occurs here. The blood pressure in each of these clusters forces out the excess water and waste leaving the blood cells in the capillaries.
If your blood pressure is too high, it damages these tiny capillaries. The damage occurs silently, without your awareness. When you do experience symptoms, the symptoms may seem random. Mayo Clinic’s website lists the symptoms as
Loss of appetite
Fatigue and weakness
Changes in how much you urinate
Decreased mental sharpness
Muscle twitches and cramps
Swelling of feet and ankles
Chest pain, if fluid builds up around the lining of the heart
Shortness of breath, if fluid builds up in the lungs
High blood pressure (hypertension) that’s difficult to control
And these symptoms usually don’t show up until damage has already been done. The kidneys and blood pressure connection is yet another reason to have your blood pressure checked, urine checked and institute lifestyle changes.