Hypertension: A cause of kidney disease
Hypertensive kidney disease is a medical condition in which the kidneys are damaged through exposure to chronically elevated blood pressure. It is one of the main causes of kidney failure, and its associated morbidity, mortality and reduced man hours of productivity, in our population. Additionally, the only effective therapy for end-stage renal disease is renal replacement therapy in the form of dialysis and renal transplantation. While these options are available locally, they are costly and access to them is inequitably distributed across the island. Given these realities, it behoves us to become aware of hypertensive kidney disease, its mechanisms, treatment and prevention as we strive towards the ultimate goal of reducing its impact on our population.
Under ideal circumstances, the pressure blood exerts as it courses through the body’s arterial system is approximately 120/80. The top figure (systolic pressure) represents the pressure wave which propagates outwards along the arteries and throughout the entire arterial system after the heart contracts, while the bottom figure (diastolic pressure) represents the pressure in the vessel after the contraction has ended and the vessel wall has recoiled.
Unfortunately, however, hypertensive patients typically have average blood pressures which are significantly in excess of 130/90 mm of mercury (the standard unit of measuring blood pressure) and neither the blood vessels nor the organs and tissues are designed to withstand such persistently elevated blood pressures. In the kidneys, the consequence of this is trauma to the walls of the small arteries within the kidney, which consequently become thickened, stiff and less elastic. Scar tissue accumulates within the vessel walls and various proteins are deposited vessels along and within them. Additionally, the capillaries become scarred; some become completely replaced by fibrous tissue.
Over a period of months to years, therefore, these filtering units of the kidneys are gradually destroyed, kidney function declines, and toxins which would normally be passed out in urine (such as urea, potassium, creatinine and organic compounds) accumulate in the bloodstream and the body.
In the early stages, the condition is asymptomatic. However, as the concentration of toxins rises, other organ systems begin to be affected. Typical symptoms of kidney disease including weakness, lethargy, loss of appetite, nausea, vomiting and drowsiness develop and progress. Additionally, protein (predominantly albumin) is spilled in the urine causing the blood levels to drop, which in turn causes limb and facial swelling. Further decline in kidney function results in the development of anaemia (low blood count) and worsening symptoms. At this stage the patient is said to be in chronic kidney failure and intervention is essential to prolonging life and to prevent further complications.
Focus on prevention
Given the costs, morbidity and mortality associated with hypertension related kidney disease, efforts should be directed at preventing it, delaying its onset, and reducing the rate of its progression. This can be achieved by:
1. Controlling the blood pressures
2. Initiating specific scientifically validated interventions
Studies have shown that treating the blood pressures to a goal of less than 130/80 is effective at achieving the above objectives. This can be attained through a combination of lifestyle modification strategies (healthy diet, exercise, weight management, stress management, smoking cessation) and, where necessary, pharmacotherapy. Lifestyle modification by itself is only effective in patients with mildly elevated blood pressures. Additionally, it requires time and discipline in order to be effective.
A wide variety of effective anti-hypertensive medications are available in Jamaica. Most are well tolerated and inexpensive and many are covered by the National Health Fund (NHF) and the Jamaica Drug for the Elderly Programme (JADEP). Fortunately too, several convenient once-a-day drug options are also available.
Unfortunately, some hypertensive patients will inevitably progress to developing end-stage kidney disease. Such patients will require a multidisciplinary team approach to management which involves their family physician, dietician, internist, cardiologist and nephrologist, as well as a support system of friends and family members. Management plans must be individualised but often involve renal replacement therapies such as dialysis and/or renal transplantation.
In summary, hypertensive kidney disease represents a challenging complication of hypertension. However, patients can be reassured that prompt recognition by their physician, aggressive blood pressure control, and the initiation of appropriate therapies, including lifestyle modification strategies, can significantly reduce the morbidity, mortality and costs associated with this condition thereby lessening its impact on our population.
Dr Handel Emery is a consultant cardiologist at The Heart Foundation of Jamaica.