Clinical Queries: Nephrology最新文献

Secondary hypertension, i.e. where a definite cause for hypertension can be found, is not uncommon in clinical practice and accounts for about 5% cases of hypertension. Common causes of secondary hypertension include renal parenchymal disease, renovascular hypertension, Conn Syndrome and pheochromocytoma. In Asian countries, aortoarteritis is still a common cause of secondary hypertension among young patients, especially females. Early diagnosis and appropriate treatment may significantly alter the natural history of the disease with substantial improvement in prognosis. Whenever a patient is diagnosed with hypertension, every effort should be made to rule out any possible secondary cause for the hypertension. Suspicion of secondary hypertension should be high in early or late onset hypertension, resistant hypertension, accelerated hypertension and in patients with markedly elevated blood pressure with severe target organ damage. Reno-vascular hypertension can be evaluated by non-invasive modalities like Ultrasound Doppler, MR angiography and CT angiography. If primary aldosteronism is suspected, patients should undergo screening with plasma rennin/aldosterone ratio and MRI for the detection of morphological adrenal abnormalities. Patient suspected of pheochromocytoma shows an increase in plasma or urinary catecholamines, but CT and MRI are needed to localize the tumours. Targeted testing should be done in all these patients to rule out any possible cause for secondary hypertension. Careful and thorough clinical evaluation and simple algorithms are needed to avoid unnecessary tests in making the diagnosis of secondary forms of hypertensions more accurately and promptly. Correcting the cause of secondary hypertension can lead to cure, avoiding the need for long-term medical therapy.

Hypertension is an epidemic affecting one billion people and is the commonest risk factor for death throughout the world. World health statistics 2012 has estimated the prevalence of hypertension to be 29.2% in males and 24.8% in females. Approximately 90 percent for men and women who are non hypertensive at 55 or 65 years will develop hypertension by the age of 80–85. Hypertension is not limited to rich population and affects countries across all income groups. Out of total 58.8 million deaths worldwide in year 2004, high blood pressure was responsible for 12.8% (7.5 million deaths). World over hypertension is responsible for 51% of cerebrovascular disease and 45% of ischemic heart disease deaths. Unlike the popular belief that hypertension is more important for high-income countries, people in low- and middle-income countries have more than double the risk of dying of hypertension.

Understanding epidemiology of hypertension will significantly help in decreasing the burden of associated morbidity and mortality. In America, with the help of programs such as National High Blood Pressure Education Program (NHBPEP), the awareness about hypertension has improved from 51 percent in the period 1976–1980 to 70 percent in 1999–2000 and as a result hypertension related morbidity and mortality has substantially improved. Since 1972, age-adjusted death rates from stroke have decreased by about 60% and that by coronary heart disease has decreased by about 50 percent. Recent WHO initiative on non communicable diseases is expected to decrease hypertension related mortality and morbidity globally.

Renovascular hypertension is among the most common causes of secondary hypertension. Fibromuscular dysplasia and atherosclerotic involvement of the renal artery are the commonest etiology behind renovascular hypertension. Its diagnosis requires a high degree of clinical suspicion followed by rationale investigations and their proper interpretation else it may be misdiagnosed as essential hypertension. The therapeutic approach of the patient with renovascular hypertension is currently a matter of great debate. In any case optimal medical therapy with antihypertensive, lipid-lowering, and platelet-inhibiting drugs should be instituted. Current evidence suggests that endovascular interventions may benefit a subset of patients with significant stenosis. Prospective, randomized and controlled studies with clearly defined clinical endpoints are needed to better define the absolute and relative indications of angioplasty in renal artery stenosis.

CKD is leading cause of secondary hypertension. Prevalence of hypertension in Indian urban population is appox. 20–40% whereas in CKD its prevalence is much higher depending on stage of CKD reaching about 90% in ESRD. Hypertension, besides proteinuria is one of important factor in progression of CKD and CVD risk. Thus it has pivotal role in outcome of CKD and ESRD patients. Large number of studies has shown that effective control of blood pressure retards progression of renal disease and lower blood pressure targets have more favorable outcome, especially in proteinuric patients. The cardiovascular mortality is much higher in CKD than general population, but there are no large studies in CKD population to ascertain optimal blood pressure in reducing cardiovascular mortality in this group. The understanding of hypertension and target blood pressure level to be achieved in CKD and ESRD patients in terms of retarding the progression of renal disease and reducing the CVD events in this population has been discussed with the available evidences.

Renovascular hypertension is the most common cause of secondary hypertension. Imaging plays an important role in establishing the diagnosis in these cases. Digital subtraction angiography (DSA) is the gold standard investigation in suspected cases. Colour Doppler Ultrasound (CDUS) is a very effective and cheap screening tool. CT angiography and MR angiography are effective and comparable alternatives to DSA. Captopril scintigraphy and renal vein renin sampling are used in selected patients in whom the functional significance of the renal artery stenosis is to be determined.

Where at one hand, the vast majority of hypertensive patients succumb to the complications of hypertension like atherosclerosis, cerebrovascular diseases and congestive heart failure, a subset of these have an exacerbation in this gradual course that needs acute management in the blood pressure control and plays a role in short term outcomes. These hypertensive crises are now encountered more frequently, in more diverse and aging population than in earlier times.

Despite the recognized unmet need of timely evaluation and management, fewer than 10% receive the recommended investigations and appropriate treatment often gets delayed. This review emphasizes the therapeutic implications of correct diagnosis, various treatment options and targets in different clinical circumstances.

Nicardipine, clevidipine, esmolol and fenoldopam have emerged as potentially superior drugs in most hypertensive emergencies as compared to other conventional drugs. For hypertensive urgencies, blood pressure lowering at a gradual pace with oral drugs & adequate follow up are two important facets of management, making sure that the blood pressure has been lowered out of a potentially dangerous range.

Impact of optimal management of hypertensive crisis should translate into lesser target organ damage and eventually fewer complications of stroke, myocardial infarction, or congestive heart failure.

Hypertensive nephropathy is one of the common causes of end-stage renal disease. Hypertension is intimately linked with the kidney as kidney diseases may lead to increased blood pressure and hypertension can be the cause of renal disease. Majority cases of hypertension are primary or essential. Renal parenchymal diseases and renovascular hypertension are important causes of secondary hypertension. Fibrous dysplasia and atherosclerosis constitute majority cases of renovascular hypertension. Renal diseases with hypertension has been divided in to the benign nephrosclerosis and malignant nephrosclerosis. Benign nephrosclerosis is characterized by hyaline arteriolosclerosis and intimal fibrosis and reduplication of internal elastic lamina of arcuate and interlobular arteries. Malignant hypertensive nephropathy is characterized by hyerplastic arteriolitis and fibrinoid necrosis of arterioles and glomeruli.