Kidney Disease and Cardiovascular Disease
Kidney disease and kidney failure is often associated with cardiovascular disease as a cause or as a consequence.
The term chronic renal insufficiency denotes to the stage where damage to the kidney impairs renal function that are detectable by some blood tests, however no obvious systemic manifestations are apparent. In chronic renal failure, the renal dysfunction progresses and results in some biochemical as well as physical manifestations that are obviously evident on blood tests. Patients often progress to the tail end of the spectrum, called end-stage renal disease (ESRD), where dialysis or renal transplantation would be necessary to sustain life.
Diabetes is the commonest cause for renal failure and ESRD causing microscopic vascular abnormalities that can in turn significantly increase the risk of cardiovascular disease.
A less common, but often under-diagnosed problem, called Renal Artery Stenosis can either cause high blood pressure and/or renal failure and accentuate the effects of high blood pressure and kidney disease on cardiovascular disease.
Renal Artery Stenosis (RAS) is caused by narrowing of the main renal (kidney) artery either as a primary event (see below) or as a part of a more diffuse process of atherosclerosis or hardening and narrowing of arteries due to cholesterol deposits.
Either way, narrowing of the blood vessel causes a decrease in the blood flow to the kidney. This in turn causes the kidney to release a substance called Renin, that initiates a series of chemical events that result in high blood pressure or better known as Renovascular Hypertension (RVH).The effects of RVH are many-fold:
- The high blood pressure experienced by patients with RVH can be severe and often difficult to control requiring the use of multiple drugs.
- As the disease progresses, the kidney itself shrinks in size with an associated decrease in function. The clinical and biochemical effect of this is often offset by a corresponding INCREASE in size of the other kidney, as the body attempts to maintain kidney function. However, as the disease progresses, the other kidney is at risk for developing damage from the hypertension and ultimately can lead to chronic renal failure.
- Chronic high blood pressure and kidney dysfunction are know independent risk factors for heart disease and cardiovascular death.
Another unusual form of RVH, seen almost exclusively in young women, is known as Fibromuscular dysplasia (FMD) and affects the muscular lining of the renal artery and causing a focal narrowing and secondary hypertension.
Signs and Symptoms
RVH may be suspected if:
- A marked difference in kidney size seen on imaging (ultrasound, CT, MRI). It is normal to have a slight difference in size, however a marked difference is highly suspicious
- Intolerance of specific blood pressure medications "” angiotensin-I (ACE-I) inhibitors or angiotensin receptor blockers (ARBs) "” with a sudden worsening of renal function
- Multiple medications (>3) are needed for blood pressure control
- New onset of high blood pressure in a patient over 55 or sudden worsening of blood pressure in a patient who was previously well-controlled on 1 or 2 blood pressure medications
- Sudden episodes of labored breathing due to fluid accumulation in the lungs
Diagnosis
RAS can be easily diagnosed using non-invasive studies such as ultrasound, MRI and some simple blood tests
