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Disorders of phosphorus metabolism

Normal phosphorus physiology 1. What is the difference between phosphate and phosphorus and how are they measured in clinical medicine? Phosphorus is a critical element in physiology. Phosphorus is an essential component of bone (hydroxyapatite), DNA, lipid membranes (phospholipids), signal molecules (phosphorylation activates numerous enzymes), and chemical energy storage (adenosine triphosphate and creatine phosphate). In the serum, phosphorus circulates as phosphate, PO 4 −3 usually with…

Hypocalcemia and hypercalcemia

1. What is calcium homeostasis? Calcium homeostasis refers to the regulation of the calcium concentration in the extracellular fluid. Normal serum calcium concentration varies between laboratories, but is usually 8.5 to 10.5 mg/dL (2.1 to 2.6 mmol/L) and it represents the sum of the three circulating fractions: 45% protein bound (albumin ∼80%, globulins ∼20%), 15% complexed to anions (citrate, bicarbonate, lactate, phosphate), and 40% free, or…

Hypokalemia and hyperkalemia

1. Describe normal potassium balance. Approximately 98% of total body potassium resides inside cells, making it the most abundant cation in the intracellular fluid (ICF). The total body stores approximately 3000 mEq or more (approximately 50 to 70 mEq/kg body weight) of K + , with the skeletal muscle cells providing the biggest storage site for intracellular K + . ICF concentration of potassium is approximately…

Dysnatremias

1. What are dysnatremias? The term dysnatremia applies when an aberration in plasma sodium concentration is present. Changes in plasma sodium concentration can result in fluid shifts between the intra- and extracellular compartments of the body. In the healthy state, the body’s osmoregulatory system maintains the plasma sodium concentration between 135 and 145 mEq Failure of this system begets an imbalance of free water intake and…

Genetic disorders of sodium transport

1. What is the difference between mendelian (or monogenic) forms of hypertension and essential hypertension? Essential hypertension has a multifactorial etiology, including demographic and environmental (dietary) factors, and genetic predisposition, which results from multiple gene–gene and gene–environment interactions. Large genome-wide association studies among various populations mapped many gene loci for essential hypertension; however these loci have been predicted to have a very small effect on individual…

Volume disorders and assessment

Volume 1. What is meant by volume? Physicians use the terms “volume” and “extracellular fluid volume” interchangeably. Because sodium is largely restricted to the extracellular fluid (ECF), total body sodium determines the ECF volume. Therefore changes in total body sodium lead to changes in ECF volume. A typical Westerner consumes about 150 mmol of sodium chloride per day. Let’s consider the hypothetical case of adding 150…

Nonpharmacologic treatment of hypertension

1. What nonpharmacologic strategies can be used to treat hypertension? Several nonpharmacologic strategies are available to improve blood pressure control among essential hypertensive patients. By extension, similar strategies may be effective among patients with chronic kidney disease. These strategies include salt restriction, weight loss, exercise, moderation of alcohol intake, and treatment of obstructive sleep apnea (OSA). 2. How effective is salt restriction? Although some experts recommend…

Pharmacologic treatment of hypertension

1. When is pharmacologic treatment of hypertension indicated? When an individual’s blood pressure (BP) does not fall below goal after a suitable period of intensive lifestyle modifications, antihypertensive drug therapy is universally recommended. There is general agreement that antihypertensive drug therapy is one of the major reasons for the decline in stroke and coronary heart disease mortality over the past 50 years. Compared to placebo or…

Hypertensive emergencies

1. How does a “hypertensive emergency” differ from “hypertensive urgency”? A “hypertensive emergency” is a clinical situation in which severely elevated blood pressure is associated with acute, progressive target-organ damage that needs to be treated immediately with a safe and controlled reduction of blood pressure. “Hypertensive urgencies” (if they truly exist; see Question 15 below) are characterized by elevated blood pressures in a patient who has…

Resistant hypertension

1. What is resistant hypertension (RH)? Is it the same as refractory hypertension? Hypertension is considered resistant if the blood pressure (BP) cannot be reduced below target levels ( Box 67.1 ) in patients who are compliant with an optimal triple-drug regimen that includes a diuretic typically with an angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) plus calcium channel blocker (CCB), or those…

Other forms of secondary hypertension

1. Besides renovascular and the traditional endocrine causes of hypertension, what are eight uncommon, but important, causes of secondary hypertension? Obstructive sleep apnea (typically causing hyperaldosteronism) Drug-induced hypertension (especially nonsteroidal antiinflammatory drugs, steroids, and/or other immunosuppressants) Thyroid disorders (hypothyroidism more commonly than hyperthyroidism) Coarctation of the aorta (typically manifested as different blood pressures in the arms or a lower blood pressure in the legs) Hyperparathyroidism (hypertension…

Endocrine hypertension

Hyperaldosteronism 1. What is hyperaldosteronism? Hyperaldosteronism is a disorder with a characteristic set of signs and symptoms resulting from excessive effects of aldosterone or a similar mineralocorticoid agent, which typically include: Hypertension: usually unresponsive to angiotensin converting-enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), or direct renin inhibitors Intravascular volume expansion Hypokalemia 2. Describe the most common subtypes or causes of hyperaldosteronism. Hyperaldosteronism can be either primary…

Renovascular disease

1. What clinical syndromes are associated with renal artery stenosis? Renovascular hypertension, progressive loss of kidney function from ischemic nephropathy, and recurrent episodes of flash pulmonary edema (meaning acute/abrupt onset pulmonary edema) are the clinical syndromes typically associated with renal artery stenosis. However, renal artery stenosis can also be completely asymptomatic. In the case of renovascular hypertension, hemodynamically significant unilateral orbilateral renal artery stenosis leads to…

Kidney parenchymal hypertension

1. What is the epidemiology of hypertension? Hypertension remains a common disease among Americans. Data from the National Health and Nutrition Examination Survey reveal that 29% of Americans are hypertensive; this prevalence rate has remained stable for the past 15 years. African Americans bear the highest burden, as over 41% are hypertensive. Other racial groups (i.e. Whites, Asians, and Hispanics) demonstrate hypertension prevalence of 25% to…

Primary hypertension

1. How is hypertension defined and classified? The Eighth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (Joint National Committee 8), published in 2014, continues to classify hypertension by the degree of blood pressure (BP) elevation ( Table 62.1A and B ). The measurement must be based on the average of at least two seated measurements on each…

Primary care of the kidney transplant recipient

1. What are the risk factors for cardiovascular disease (CVD) in patients receiving a kidney transplant? See Table 61.1 . Table 61.1. Risk Factors for Cardiovascular Disease TRADITIONAL TRANSPLANT RELATED CONDITIONAL Age Immunosuppression Homocysteine Male sex CKD CRP Family history Proteinuria AGEs Obesity Anemia Diabetes Hypertension Hyperlipidemia Tobacco abuse AGEs , Advanced glycosylated end products; CKD, chronic kidney disease; CRP, C-reactive protein. 2. Are statins beneficial…

Posttransplant infections

1. What type of infections do kidney transplant recipients develop? Donor-derived infections Recipient-derived infections Nosocomial-acquired infections Community-acquired infections 2. Is there any pattern to infections that occur post transplantation? Yes. Karuthu et al. reviewed this recently, including the timing of infections post transplant. Infections occur in a generally predictable pattern after kidney transplantation. See Fig. 60.1 First month post transplant: Nosocomial and surgery-related infections are the…

Posttransplant malignancies

1. Are transplant recipients at greater risk for the development of malignancies? Yes. The chronic exposure to immunosuppressive agents increases the long-term risk of malignancy by two to threefold compared with the general population of the same age and sex. Kidney transplant recipients have the cancer risk of a nontransplanted individual 20 to 30 years older than them. If a recipient had a cancer prior to…

Rejection of the kidney transplant

1. How to evaluate acute kidney injury (AKI) in the kidney transplant patient? See Fig. 58.1 . When deciding the baseline kidney function and using the serum creatinine (Scr), the clinician must be careful. The ideal baseline Scr is based on the most recent trend when the patient was in a steady state. Time after transplantation is also critical in sorting through the differential diagnosis of…

Immunosuppression

1. What is the goal of immunosuppression? The central goal of immunosuppression is to prevent rejection of the renal allograft. The intensity of immunosuppression must be weighed against the undesired consequences of immunodeficiency, such as infection or cancer. Close monitoring, knowledge, and expertise are required to balance the efficacy and toxicity of kidney transplantation immunosuppression. 2. What are the classes of immunosuppressive therapies used in kidney…