11. RENAL HYPERTENSION

Question 1

RENAL HYPERTENSION definition?

Answer 1

Renal disease contributes to two important
endogenous causes of secondary hypertension: renal parenchymal disease (as a result of the primary
injury of the functional renal parenchyma – nephrogenic hypertension), accounting for 2% to 4% of
hypertensive patients, and renovascular (vasorenal) hypertension - is due to some anomalies and
changes of the renal vasculature (renal arterial stenosis),

Question 2

Injury of the renal parenchyma?

Answer 2

Hypertension during parenchyma injury is one of the most common types of the secondary
hypertension. An increased blood pressure is mostly the first sign of the original renal disease.
a drop in the Na+ excretion. The increased volume of the circulating blood will lead
to an increased venous return into the heart. That is why the central venous pressure is increasing
and the ventricular filling is increased as well. As a result of these changes there will be an increment
of the cardiac output and the systemic arterial blood pressure – this is known as a volume
hypertension.

Question 3

Injury of the renal parenchyma
(The volume hypertension occurs)?

Answer 3

The volume hypertension occurs in acute glomerulonephritis. It is usually transient – and after the
acute stage the blood pressure returns to normal values. But hypertension may manifest later, after
several years when additionally to the glomerular lesions some changes in the arteries and the
arterioles arrive. In such cases there is already a combination of the volume and the resistance
hypertension. In patients with the tubulointerstitial diseases of the kidneys, the hypertension is less
common as that in the glomerulonephritis. The cause lies in the lower ability of the reabsorption of
water based on the primary injury of the tubules.

Question 4

Injury of the renal parenchyma
(Another mechanism)?

Answer 4

Another mechanism, by which the renal disease can result in an increased blood pressure is the
resistance mechanism. The mechanism of the resistance hypertension is explained as the result of
the effect of the pressor and depressor substances that are formed in the kidneys. One of the pressor
substances that is incorporated in the regulation of the blood pressure in the physiological but
mainly in the pathological conditions is the renin–angiotensin–aldosterone system.

Question 5

Injury of the renal parenchyma
( decisive role of the renin–angiotensin system (RAS))?

Answer 5

The decisive role of the renin–angiotensin system (RAS) in the pathogenesis of hypertension is
assumed in renal infarction, and in unilateral renal affection, and it is absolute and very aggressive in
cases of renal tumor that secretes rennin. In cases of bilateral parenchymal diseases of the kidneys,
the level of the plasma rennin activity (PRA) is only slightly increased, or it might even be normal,
what on the other hand does not exclude the role of this factor in the pathogenesis, mainly when we
are dealing with a consequent increase of the plasma volume.

Question 6

Injury of the renal parenchyma
(Lowering the vasopressor function)?

Answer 6

Lowering the vasopressor function of the kidney explains the hypertension that accompanies renal
diseases, which are presented with prominent destruction of the renal medulla, which produces the
depressor substances (prostaglandins): chronic interstitial nephritis, pyelonephritis, obstructive
uropathies, and polycystic kidneys.

Question 7

Renovascular hypertension (vasorenal hypertension)?

Answer 7

Renovascular hypertension results from a narrowing of the renal artery. The cause of its narrowing
lays in many pathological processes, most commonly they are atherosclerosis and fibromuscular
hyperplasia. As a result of the classical experiments with hypertension in animals it was considered
sure till recent time that the cause of hypertension in those animals was due to renin – angiotensin system, that is activated by renal ischemia (i.e. by the lower pressure amplitude in the renal vascular
area) caused by the drop in the kidneys perfusion. However, later on there appeared many pieces of
evidence which deny a direct relationship between this system and a chronic clinical or experimental
hypertension. The course of renovascular hypertension is similar to the course of the essential
hypertension, however it is usually more serious and a malignant deterioration is frequent. What is
specific for this type of hypertension is a progressive ischemic post stenosis renal atrophy. From the
mentioned above it is clear that two mechanisms share the pathogenesis of the renal hypertension.
The volume (hyporenin) mechanism and the resistance (hyperrenin) mechanism. According to the
type of renal disease, the anatomical and functional renal injury, and the stage of this disease both
those mechanisms can alternate with each other or interact with each other. In certain cases one of
them has the primary role that will promote the whole mechanism, in other cases it is the factor that
maintains the hypertension. Apart from the mentioned factors the hemodynamic changes caused by
anemia play an important role in the pathogenesis of renal hypertension that accompanies chronic
renal insufficiency.