This document summarizes hypertension and its relationship to the kidneys. It discusses how essential hypertension is mainly caused by abnormal sodium retention and genetic predisposition. It also notes that low birth weight can result in fewer nephrons and later hypertension. The kidneys play a key role in maintaining blood pressure through pressure natriuresis, which allows excess salt to be excreted by inhibiting reabsorption when blood pressure is high. For patients with essential hypertension, diuretics are often the first choice of treatment since salt retention is a major factor, but they can cause side effects like hyponatremia and gout. The document emphasizes monitoring blood pressure and kidney function for patients on antihypertensive medications.

1. Hypertension and kidney
Dr.Suresh Kumar

2. Introduction
 Essential Hypertension is mainly due to abnormal retention of sodium
 There is also genetic predisposition to HTN and progress has been
made to identify the genes responsible for HTN
 A number of studies also showed low birth weight causes deficient
number of nephrons which in turn causes HTN
 Obesity per se if not superimposed by low birth weight may be the
cause for HTN
 Recent development of devices to disrupt the plexus of renal
sympathetic nerves in the adventitia of renal arteries has also become
a point of interest in Rx of HTN

3. Hypertension and kidney
 The driving force for Glomerular filtration is the blood pressure and
kidneys with inbuilt mechanisms to maintain blood pressure offer a
survival advantage
 Blood pressure is the product of cardiac output and peripheral
resistance
 Cardiac output largely depends on the blood volume which is mainly
salt and water , the peripheral resistance is determined by the state
of tone in resistance vessels
 Vasoconstriction is the immediate response to hypotension , but all
vasoconstrictor stimuli also initiate mechanisms to retain salt and
water
 So long term maintanence of blood pressure is mainly dependant on blood
volume.

4.  Ancient man has discovered SALT as a preservative and an ingredient as food
, and now its use has become excess that body could not handle it
 The only way excess salt can be excreted is to shut off the pathways for
reabsorption
 The most effective tool for excretion is pressure natriuresis
 High blood pressure in arterioles is transmitted to renal peritubular
capillaries and interstitium and inhibits re absorption of sodium and water
by proximal tubule leading to natriuresis
 As juxta medullary glomerular arterioles are less capable of constriction in
response to HTN vasa recta and medullary interstitium even have high
pressure
 Increased sheer stress in vasa recta causes release of NO which inhibits
sodium transporters in Medullary tubules.
 Pressure Natriuresis limits sodium retention and returns BP to baseline

5. Genetic
 There is strong genetic predisposition to HTN
 Having one Hypertensive in a family increases the risk of other members of having HTN
 Inheritance of HTN is a dominant trait
 A genetic predisposition to HTN coupled with a excessive salt intake leads to HTN and
what we call essential HTN is salt related in susceptible individuals
 It is clear that incidence of salt sensitive HTN increases with Age
 Age is associated with stiffening of arteries and arterioles , it is likely that such
senescent arterioles interfere with pressure natriuresis and it causes increased incidence
of HTN
 The KIDNEY is therefore the cause of the most ESSENTIAL HTN even when renal function is
quite normal
 In addition most renal diseases are associated with either sodium retention or with over
action of RENIN angiotensin system or both and are the major cause of Secondary HTN.

6. Developmental origins of health and disease
 It has been found that low birth weight predispose to HTN in adult hood.,
particularly if those people become over weight later.
 Infants with LBW Or SGA have smaller number of nephrons than those with
normal birth weight
 When fetal nutrition's is compromised the brain and heart receive more
nutrients than kidney
 Nephron number has been found reduced in LBW infants
 Every KILOGRAM of birth weight corresponds to 2,57,426 Glomeruli.
 Low nephron numbers are associated with large glomeruli and single nephron
Hyper filtration so total glomerular filtration is normal but hyperfiltration
progressively damages kidney and leads to CKD.

7.  These kidneys with deficient number are unable to excrete the excessive
quantities of Sodium
 The Blood pressure Natriuresis set point is reset ever higher and leading to
Hypertension
 This is a significant cause of HTN especially in developing countries

8. Obesity and HTN
 Many factors have been described like
 Significantly Hyperactivity of Renin Angiotensin System
 Sympathetic System
 Hyperinsulinemia
 Vasoconstriction and Sodium Retention
 Pro Inflammatory Cytokines and Oxidative Stress  endothelial
Dysfunction and Increase arterial stiffness
 Sleep apnea also causes release of such cytokines , inflammation
and HTN
 Leptins

9. Renal sympathetic System
 The kidney is well supplied with sensory nerves that transmit both chemical
and mechanical information to the autonomic nervous system through a post –
ganglionic sympathetic plexus in renal arterial adeventitia
 The composition of the interstitial fluid and its hydrostatic pressure are both
monitored and its alterations influence the Hypothalamus create pain
senstations and promote sympathetic outflow to HEART and Kidney
 Sympathetic stimulations raises BP by increased renal vascular resistance ,
stimulating renin release from Juxta glomerular cells and increasing tubular
sodium reabsorption
 In healthy individuals stimulation of afferent nerves modulate sympathetic
nerve outflow both to ipsilateral and contralateral kidneys, reducing
vasoconstriction , and sodium reabsorption thereby reducing HTN

10.  But in many renal diseases this effect is lost and leading to vasoconstriction
and retention of water and salt  Increased Blood Pressure
 Increased afferent nerve stimulation could also act on Hypothalamus to
release vasopressin and cause HTN and water retention.
 Under normal circumstances , sympathetic system has little effect on kidneys
however when anxiety and stress exists renal vascular resistance increases
and salt, water retention increases causing HTN

11. Effect of hypertension on the kidney
 Benign arteriolar nephrosclerosis predominantly affects
the arterioles leading to their thickening and reduction
of lumen  consequent ischemic changes in glomeruli
renal failure develops slowly
 Malignant HTN : overhelms renal auto regulation and
pressure is transmitted to the glomeruli before
arteriosclerosis can occur to protect them
 Fibrinoid necrosis dominates the picture , hematuria and
Proteinuria can be marked and renal failure develops rapidly

12. Diuretics for Essential HTN
 Since salt retention is the major factor in causing essential HTN , the obvious
first choice of therapy is DIURETIC
 Hyponatremia is the common side effect of it
 However MILD hyponatremia ( Sr.Na+ : 130-135 mEqL ) is not such a harmless
condition
 It causes instability of gait
 Attention deficit
 Confusion
 Increased chances of FALL Increased fractures
 Osteoporosis

13.  Gout : as diuretics are excreted by organic anion transporters
which also transport URIC ACID and diuretics compete with URIC
ACID Hyper Uricemia  GOUT
 Torsemide have the greatest effect
 Though they cause this effect only in susceptible individuals : high
serum uric acid causes endothelia dysfunction , inflammation and
oxidative stress and stimulates RES
 Net result is glomerular Hyper filtration and renal interstitial fibrosis
and Faster progression of Renal Failure

14. Precautions
 Most anti-hypertensives act by inhibitory compensating mechanisms that
should raise BP when we assume in ERECT posture
 So we should make it a point in monitoring BP in both LYING and ERECT
posture in every patient who is on treatment
 The target blood pressure should be 140/90 mmhg in all hypertensives
 130/80 in all patients with renal failure
 Monitor urine protein and Renal Function test at regular intervals of time

15. Thank You