Annual Review of Medicine - Volume 45, 1994

The oropharynx and esophagus convey swallowed materials from the mouth to the stomach and protect the airways from aspiration. These functions are subserved by complex neuromuscular interactions that coordinate the timing of the peristaltic contractions of the swallowing organs. The oropharynx and upper esophagus are composed of striated muscle, whereas the distal esophagus is composed of smooth muscle. The central nervous system completely controls peristalsis in the striated muscle organs. In the distal esophagus, neuromuscular mechanisms intrinsic to the esophagus control peristalsis. Diseases of the striated muscle, of the smooth muscle, or of the nervous system can lead to a derangement of peristalsis and disrupt the propulsion of swallowed materials to the stomach.

At least two different genes, which have been mapped to chromosomes 4 and 16, cause autosomal dominant polycystic kidney disease, a disorder with renal and extrarenal manifestations. Although gene-linkage testing is possible, the disease is diagnosed mainly through ultrasonography. Renal disease is characterized clinically by hypertension, acute and chronic pain, and variable progression to end-stage renal disease. Extrarenal manifestations include liver cysts, which may lead to complications; ruptured intracranial aneurysms; cardiac valvular disease; colonic diverticula; and inguinal hernias. Disease management is directed at minimizing and treating the complications of this illness.

Acute myocardial infarction results from the cessation of myocardial blood flow caused by thrombotic occlusion of a coronary artery. Rapid restoration of blood flow to the ischemic myocardium minimizes cardiac damage and improves early and long-term morbidity and mortality. Chest pain is the first symptom of myocardial infarction, but in some patients with silent ischemia, the disease can be diagnosed only in retrospect. In symptomatic patients, myocardial infarction should be accurately and promptly diagnosed so that reperfusion therapy can begin immediately. Electrocardiography is the simplest diagnostic modality. Although regional ST-segment elevation is specific, it is not sensitive. In contrast, new computerized algorithms for electrocardiographic analysis and serial monitoring increase sensitivity without decreasing specificity. In the emergency room, echocardiography is used to diagnose patients with no prior history of coronary artery disease whose electrocardiograms proved nondiagnostic.

Time-consuming perfusion nuclear studies are inferior to echocardiography but may nevertheless enable physicians to diagnose myocardial infarction in the emergency room. Although the presence of excess creatine kinase is a sign of myocardial necrosis, its increase is delayed for a few hours after coronary occlusion. Doctors can diagnose myocardial infarction as early as two hours after coronary occlusion with the help of simpler automatic assays of MB-creatine kinase mass that use monoclonal antibodies. Other investigational markers of myocardial necrosis include myoglobin and troponin. Elevation of a circulating protein marker also signifies established necrosis, but physicians hope to achieve reperfusion through therapy before irreversible damage occurs.

Cancers are thought to develop as a result of sequential mutations of genes important in the control of cellular growth. Recently investigators identified a number of genetic defects that affect oncogenes and tumor-suppressor genes and that provide insight into the biology of benign and malignant thyroid neoplasms. Future implications for thyroid tumor diagnosis and prognosis are considered in this chapter.

Carotid arteriosclerotic disease is the most readily treatable type of lesion leading to stroke. Its management involves lowering those risk factors over which the patient has control. Patients should regulate hypertension, quit smoking, seek medical attention for treatable cardiac abnormalities, and take steps to reduce increased blood lipids. For symptomatic carotid disease, regardless of whether surgery is offered, platelet inhibitors are obligatory. The recommended dose is 650 mg aspirin per day (or up to 1300 mg, if tolerated). For patients whose symptoms continue despite aspirin therapy or who are aspirin intolerant, ticlopidine is the only recommended platelet inhibitor.

Cerebral arterial bypass surgery is not an effective treatment for carotid arteriosclerosis. Carotid endarterectomy helps patients with ≥ 70% stenosis as determined by strict arteriographic measurements. We do not yet have sufficient data to determine whether endarterectomy would benefit patients with lower levels of carotid stenosis or asymptomatic patients with any degree of stenosis.

Renal insufficiency, which is present initially in almost half of patients with multiple myeloma, usually results from myeloma kidney or hypercalcemia. Neither the class of light chain nor the isoelectric point plays an important role in kidney failure. Acute renal failure must be treated with appropriate fluids and with electrolytes and hemodialysis if necessary. Plasma exchange may be helpful, but has not been proven as such. The presence of a nephrotic syndrome and a monoclonal κ or λ light chain in the urine almost always indicates primary amyloidosis (AL) or light-chain deposition disease. Amyloid fibrils must be distinguished from the fibrils of immunotactoid glomerulopathy.

Intestinal transplantation is often the only alternative form of treatment for patients dependent on total parenteral nutrition for survival. Although a limited number of intestinal transplantations have been performed, results with FK 506 immunosuppression are comparable to those for other organ transplants. The impact of successful intestinal transplantation on gastroenterology will likely be similar to the impact of kidney and liver transplantation on nephrology and hepatology.

Recent advances in cell isolation techniques have greatly enhanced our understanding of the phenotype and function of hematopoietic stem cells in mice and humans. Many clinical studies have established the efficacy of using peripheral blood stem cells to supplement or replace bone marrow transplantation as a therapeutic modality for several types of malignancies. This new approach to malignant disease management, perhaps in combination with posttransplantation cytokine therapy, promises to completely alter the clinical course of bone marrow transplantation.

Collagenous and lymphocytic colitis are newly recognized causes of choric watery diarrhea that typically affect middle-aged patients. Although endoscopic studies are normal, inflammatory changes and (in the case of collagenous colitis) collagen deposition occur histologically in the colonic mucosa. The pathogenesis of these disorders remains a mystery, but the possible causes are intriguing. Patients may experience spontaneous remissions and relapses, but treatment with sulfasalazine or prednisone is usually effective for patients with distressing symptoms.

Demonstrated associations between postmyocardial infarction ventricular arrhythmias and a higher subsequent risk of both sudden and all-cause mortality have prompted a search for effective and safe treatment modalities. Recently completed clinical trials have provided a rationale for treatment recommendations in some specific settings. Beta-blocking therapy is recommended for postinfarction patients with frequent or complex ventricular premature beats. In contrast, calcium antagonist therapy is not helpful in these cases, and Class I antiarrhythmic therapy is actually harmful. Early indications of benefit from Class III antiarrhythmic therapies, particularly amiodarone, are under evaluation in large trials. Patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) occuring late after myocardial infarction require therapy. Viable therapeutic methods include individualized antiarrhythmic therapy selected by the noninvasive approach, individualized antiarrhythmic therapy selected by the invasive approach, empiric amiodarone therapy, transcatheter or surgical ablative therapy (for VT), and use of an implantable cardioverter defibrillator. Clinical trial data have yet to determine which of these approaches is most effective under which circumstances. Postinfarction patients with nonsustained VT are the focus of several ongoing treatment trials. Early data suggest that risks requiring specific therapy are reached only by those patients who also have significant left ventricular dysfunction. The presence of inducible sustained ventricular tachycardia at an electrophysiologic study may further risk stratify such patients. High-risk patients with nonsustained ventricular tacycardia, left ventricular dysfunction, and inducible sustained ventricular tachycardia should participate in ongoing clinical trials. In the absence of this opportunity, intensive treatment should be considered.

Heart transplantation in children with complex congenital heart disease or cardiomyopathies has become an effective form of therapy for patients with no other surgical options. Because pediatric pulmonary transplantation is a relatively new procedure, long-term follow-up data are not yet available. However, the intermediate-term results of pediatric lung transplantation appear similar to those for heart and lung transplantation. Children represent a particularly difficult patient group for transplant of thoracic organs, and recipients must be selected carefully. Additionally, physicians must pay close attention to multiple medical conditions relating to the underlying disease process in order to achieve optimal results.

The molecular basis for several hereditary disorders of connective tissues has been elucidated in recent years. In this chapter, we discuss recent advances in the molecular characterization of a number of these disorders and examine their clinical applications.

Hirudin is the most potent and specific known inhibitor of thrombin, the enzyme that plays a key regulatory function in hemostasis and blood coagulation. The importance of thrombosis in cardiovascular disease has recently highlighted the limitations of existing antithrombotic drugs and the potential value of direct thrombin inhibition as an effective approach to antithrombotic therapy. Hirudin and a small peptidomimetic analog—hirulog—are being developed as alternatives to heparin for the treatment of unstable angina, for prevention of abrupt closure and restenosis following coronary angioplasty, for prevention of deep vein thrombosis after major orthopedic surgery, and as an adjunct to fibrinolytic therapy. Direct thrombin inhibitors have several potential advantages over heparin: They can inhibit thrombin bound to clots or extracellular matrices, which are relatively resistant to heparin; they do not require antithrombin III as a cofactor, which may lead to a more predictable dose response; and they are not inhibited by activated platelets, which release platelet factor 4 and other molecules that neutralize heparin. The results of early clinical studies suggest that hirudin and hirulog may be more efficacious and more predictable and may have fewer bleeding complications than heparin for several clinical indications.

Diabetic vascular complications affect both micro- and macrovasculature, primarily in the retina, renal glomeruli, and multiple sites in the macrovessels. This review presents a summary of the abnormal function found in vivo and in cultured vascular cells exposed to elevated levels of glucose. We also discuss the various biochemical hypotheses that have been proposed to explain the adverse effects of hyperglycemia on vascular cells.

Hypercalcemia is the most common metabolic complication of cancer. Malignancy-associated hypercalcemia (MAHC) can be divided into two syndromes, humoral hypercalcemia of malignancy (HHM) and local osteolytic hypercalcemia (LOH), based on whether a circulating hormone or local paracrine factors mediate accelerated bone resorption. Over the past decade, studies have shown that parathyroid hormone-related protein is the cause of the HHM syndrome, and recent data suggest that this protein may also play a paracrine role in some patients with local osteolytic hypercalcemia. Study of the regulation of parathyroid hormone-related protein gene expression is beginning to shed some light on the molecular mechanisms responsible for this common clinical problem.

The nephrotic syndrome is a consequence of urinary loss of intermediate-sized plasma proteins and the resulting homeostatic responses to those losses. Plasma protein composition is changed greatly. Pathphysiologic changes are a consequence of the nature of the proteins lost and of the proteins that are increased in plasma to replace them. Plasma oncotic pressure (π) falls because of the replacement of relatively small plasma proteins by larger ones. Decreased π increases transudation of fluid into the interstitum and favors edema. This is exacerbated by causing renal insensitivity to atrial natriuretic factor (ANF), primary renal sodium retention, and plasma volume expansion. Many proteins lost in the urine, such as erythopoietin and IgG, are not defended by increased synthesis. Their loss may result in reduced immunity, anemia, and endocrinopathies. Albumin synthesis can be increased by dietary protein augmentation; however, urinary protein losses also increase, offsetting any palliative effect of increased albumin synthesis on albumin stores. The synthesis of many other proteins secreted by the liver is also increased, causing an elevation in plasma levels of several large proteins, including lipoproteins and elements of the coagulation cascade. This results in hyperlipidemia and, in conjunction with the urinary loss of smaller proteins that impede coagulation, a hypercoagulable state. Lipoprotein catabolism is also reduced as a consequence of proteinuria contributing to increased lipid levels.

The thalassemias are extremely heterogeneous in terms of their clinical severity, and their underlying pathophysiology relates directly to the extent of accumulation of excess unmatched globin chains: α in βthalassemia and βin the αthalassemias. However, the accumulation of each separate globin chain affects red cell membrane material properties and the state of red cell hydration very differently. These observations presumably account for the varying extent of ineffective erythropoiesis and peripheral blood hemolysis in the major variants of thalassemia.

Psychotic illnesses (schizophrenia and schizoaffective and affective psychosis) have a lifetime prevalence of 2–3% and probably occur at a similar rate in all human societies. No etiologically significant environmental precipitants have been identified, and this suggests that these diseases are primarily genetic. Brain studies reveal that in schizophrenic patients, development of cerebral asymmetry is arrested, which may be associated with a small reduction in cortical mass. Episodes of illness can be ameliorated by dopamine (in particular D2) antagonists, drugs that are antipsychotic rather than merely antischizophrenic. The discovery of at least five dopamine receptor subtypes and their genes paves the way for new approaches to treatment. However, whether psychotic patients undergo a primary disturbance of dopaminergic transmission remains unclear.

Pharmacologic therapy of recurrent nephrolithiasis continues to be the mainstay of the strategy to prevent recurrence. This approach persists even in the face of increasing evidence of a marked benefit of mere entry into a nonpharmacologic diet and fluid modification protocol at a clinic specializing in the evaluation and therapy of recurrent nephrolithiasis (the “Stone Clinic effect”). This review examines the role of diet in the pathogenesis of various forms of nephrolithiasis and the effectiveness of dietary therapy in preventing new stone formation. Recent and older evidence support a primary role for modification of diet, particularly diet protein and sodium intake, in the prevention of recurrent nephrolithiasis.