Secondary Hypertension

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Secondary Hypertension

Specific cause can be found only in 5-10% of the people with hypertension. It is usually seen in people who develop hypertension at an early age or have no family history of the disease. The causes are:

  • Kidney related:Kidney diseases are the most common cause of secondary hypertension. The common causes are :
    • Infection of the kidney
    • Kidney damage due to long standing diabetes
    • Renovascular stenosis (Reno=kidney, vascular=blood vessel, stenosis=blockage) leads to low blood flow to the kidneys. The kidneys then release certain chemicals (like Renin) to raise the blood pressure.
    • Tumors of kidney or allied organs that produce excessive amounts of Renin (a chemical released by kidneys which increases blood pressure).
    • Polycystic renal disease (a congenital birth defect in which the kidney and other organs like lung, liver contain many balloon-like spaces filled with a clear fluid)
    • Miscellaneous: scarring of the kidney
  • Hypertension associated with pregnancy:Some women may develop high blood pressure during the last months of pregnancy, this is termed as Toxemia of Pregnancy.
  • Neurological  
    • Psychogenic
    • Riley-Day syndrome (a rare disease)
    • Polyneuritis (inflammation of nerves that fail to control proper arterial wall tension properly)
    • Lead poisoning
    • Raised intracranial pressure (high fluid pressure within brain cavity)
    • Spinal cord damage (acute)
    • Diencephalic syndrome (brain damage)
  • Steroid Activity
    • Adrenal gland hyperfunction: This is a gland situated above each kidney. Its hyperfunction may give rise to high blood pressure.
      • Cushing’s disease and syndrome
      • Primary hyperaldosteronism
      • Congenital or hereditary adrenogenital syndromes
      • Pheochromocytoma: (An abdominal tumor that off and on secretes a lot of Adrenaline-like chemical to increase blood pressure suddenly)
  • Others  
    • Coarctation of aorta (constriction of the main arterial trunk just after it comes out of the left heart)
    • Increased intravascular blood volume (too much intravenous fluid administration)
    • Polycythemia rubra vera (a condition where there is too much red blood cells)
    • Vasculitis (inflammation of arterial walls causing constriction that raises blood pressure) e.g. Polyarteritis nodosa, Systemic lupus erythematosus
    • Hypercalcemia (high blood calcium levels)
    • Drugs (glucocorticoids, cyclosporine, cocaine, amphetamines)
    • Alcohol withdrawal

Diagnosis of secondary hypertension

There are many causes of secondary hypertension. Some clinical findings may point towards some specific causes of secondary hypertension. These may include :

  • Abrupt and marked rise of blood pressure in an individual aged 25 to 50 years may indicate need to exclude renovascular hypertension (hypertension due to kidney vessel disease) and pheochromocytoma (a tumor in the abdomen that releases sudden amounts of Adrenaline type hormone to suddenly raise blood pressure).
  • Palpitation, anxiety attacks, unusual sweating, increased blood sugar and weight loss points towards pheochromocytoma.
  • An abnormal blood flow sound (bruit) near the umbilicus points towards renal artery stenosis (obstruction in the artery supplying blood to kidneys: this causes reduced blood supply to kidneys that releases Renin to raise blood pressure).
  • A mass felt on one or both upper flanks may mean polycystic kidney disease (Kidney mass is replaced by small sacs filled with fluid), to be confirmed by an abdominal ultrasound examination or intravenous pyelogram.
  • Therapeutic failure : Non responsive to initial drug therapy also points towards secondary hypertension.

Investigations required for various conditions are

Chronic kidney failure   

  • Blood tests show elevated level of creatinine or urea nitrogen
  • Urine examination shows presence of protein
  • Ultrasound of abdomen may show kidneys to be small and shrunken 
  • Glomerular Filtration Rate

Pheochromocytoma

  • Measuring the levels of Adrenaline /Nor-Adrenaline and their degradation products in blood and /or urine.
  • Certain suppressive tests

Cushing’s Syndrome

  • Blood test shows low potassium and high sodium levels
  • Urine test shows the reverse: high potassium and low sodium
  • Urine excretion level of hormone degradation products may be done
  • Specialized tests like Dexamethasone challenge tests may help rule out Cushing’s Syndrome

Kidney blood vessel disease

  1. Specific abnormalities seen in Rapid sequence intravenous pyelogram
  2. The digital subtraction angiogram (picturization of kidney blood vessels by injecting dye into the kidney arterial system)
  3. The Captopril Challenge renal scan
  4. Renal duplex ultrasound
  5. Renal vein Renin determinations

Primary Aldosteronism

  • Blood tests show low potassium.
  • Blood and Urine levels of Aldosterone are high
  • The level and activity of renin is low
  • Specialized tests to study aldosterone levels in kidney veins