Hypertension & chronic kidney disease

The Foundation for IgA Nephropathy

Hypertension Notebook

Hypertension & chronic kidney disease

Hypertension, is the medical term for high blood pressure. Hypertension, on its own, is the second most common cause of end-stage renal failure, next to diabetes. It is common for all types of chronic kidney disease to eventually cause hypertension (approx. 80% of chronic kidney disease patients develop hypertension at some point). The reason for this is two-fold. With reduced kidney function, there may be a certain amount of clinical and sub-clinical fluid retention in the body, due to poor elimination of fluids and poor control of sodium. Perhaps more importantly, the kidneys are a major component in the body's regulation of blood pressure. As such, the kidneys have their own ability to raise blood pressure via release of a hormone called renin. Release of renin triggers a cascade of events all over the body which eventually cause constriction of the blood vessels (vasoconstriction). This cascade of events is called the renin-angiotensin-system, or RAS for short. When the kidneys sense that the glomeruli (the actual filters in the kidneys) are not getting the blood perfusion that they need (this means good, adequate blood flow within the glomeruli), they cause release of more renin, and blood pressure is eventually raised throughout the body. Since chronic kidney disease does affect blood perfusion within the glomeruli, chronic kidney disease is almost always accompanied by hypertension to some extent, even if there is no fluid retention. Some high blood pressure medications work by inhibiting the renin-angiotensin-system specifically, and these are therefore most effective in the context of chronic kidney disease.

Special info for IgAN patients

Hypertension is very common with IgAN nephropathy, especially when you get to about 50% kidney function or less. It can also sometimes be severe and difficult to control. With blood pressure medications, doctors have to balance how low they can get your blood pressure and what medications you can tolerate in order to achieve that level. As IgAN progresses, it's not uncommon to need 2 or 3 different blood pressure medications, or more, and sometimes, the best that can be achieved may not reach the target BP given in the guidelines. Another problem is that, if you don't have regular check-ups, high blood pressure can creep up on you as you progress with IgAN without you realising it. This is because high blood pressure has no symptoms that you can notice, as such, and you can have fairly severe high blood pressure without even knowing it. Since in the early years with IgAN, when it's still mild, there are few symptoms, it's easy to be complacent about it and not see a doctor regularly. This is especially true for those IgAN patients who never have visible blood in the urine. High blood pressure is just as bad for your kidneys as the IgAN itself, and even worse if severe, so, have your family doctor check it at least a couple of times per year. Don't let severe hypertension creep up on YOU.

A few things to keep in mind

It is common for people to monitor their own blood pressure at home with electronic blood pressure machines. If you do this, you may be able to spot trends in your BP that are not apparent when BP is only measured in the doctor's office. However, if you do this, it's important for you to realize that blood pressure varies during the day according to circadian rhythm, activities, etc. These variations are normal, and one should not panic if the BP measures as being elevated at various times. What matters most is your average resting blood pressure, not isolated measurements. Circadian rhythm is a known phenomenon. According to this rhythm which repeats itself daily, the majority of people will experience lower BP at night (systolic BP, the higher number, will usually dip by about 10%, while diastolic, the lower number, will dip by about 15%. However, some people may not experience this nightly drop in blood pressure. Within the hypertensive specialty, these are referred to as "non-dippers". Conversely, BP will be higher at certain times within the day, notably in the morning after rising, when BP will typically be higher. Don't let these normal variations cause anxiety over your blood pressure. Also, you should realize that the most common blood pressure medications used for renal patients will not typically lower your BP very much on their own. A typical BP reduction from an ACE inhibitor in this context is about 4 points for systolic (that's the higher figure), so, don't expect a huge drop in BP.

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