Hypertensive Kidney Disease

The kidney is essentially a filter made of blood vessels, so pressure in the circulation is transmitted directly to it. Years of raised pressure thicken and narrow the small arteries running through the kidney, and the filtering units they supply shrink and scar for lack of blood.

The relationship works in both directions, and that is the difficulty. The kidney controls blood pressure by managing salt, water and a set of hormones. A damaged kidney manages those less well, so the pressure rises further, which damages more of the kidney. Left unbroken, this loop tightens slowly over a decade or more.

The damage is silent for most of that time. High blood pressure causes no sensation at all until it is extreme, and the kidney has so much spare capacity that a substantial amount can be lost before any blood test moves. Most people learn about it from a routine test taken for another reason.

Risk is higher if the pressure has been high for many years, if it has been poorly controlled, if you also have diabetes, and in people of African descent. It is one of the two commonest causes of kidney failure worldwide.

The centrepiece is the blood pressure measurement itself, done properly. Your doctor will use the correct cuff size, have you sitting quietly for five minutes with your back supported and your feet on the floor, and take readings in both arms and then standing. A single reading in a busy clinic decides nothing, so expect to be asked to record readings at home over some weeks, or to wear a monitor for twenty-four hours.

The examination then looks for what the pressure has already done elsewhere. Your doctor listens to the heart for the changes that come with a thickened muscle, feels the pulses in the legs, listens over the abdomen for the sound of a narrowed kidney artery, checks the ankles for fluid, and looks into the back of the eye, where the small vessels can be seen directly and mirror what is happening in the kidney.

They are also asking whether something other than plain hypertension is at work. High pressure beginning before forty, pressure that resists three or more medicines, or kidney function that falls suddenly all prompt a search for a specific cause, since some of those are correctable.

The kidney damage already present does not reverse; the scarred filters are gone. What is achievable, and achievable for most people, is halting or slowing what happens next, and the whole of the treatment is aimed at that.

Getting the pressure to target usually takes two to three months of adjustment, and most people need more than one medicine to do it. Expect a review every two to four weeks while doses are being changed, then every three to six months once stable. Kidney function and potassium are rechecked one to two weeks after any change.

A small rise in the creatinine figure when a blood pressure medicine is started often alarms people. Up to a point it is expected, it reflects the pressure inside the kidney coming down, and your nephrologist is watching for it. Do not stop a medicine on your own because of a number.

The daily part is yours. Salt is the single biggest lever available in an Indian kitchen: pickles, papad, packaged snacks and added table salt are where most of it comes from. Home readings, brought to each visit, are the most useful thing you can hand your doctor.