ESSENTIALS OF DIAGNOSIS
Inadequate intake of energy and/or protein, increased nutrient losses, or increased nutrient requirements.
Kwashiorkor: caused by protein deficiency
Marasmus: caused by combined protein and energy deficiency.
Protein–calorie malnutrition may be mild, moderate, or severe.
Protein loss correlates with weight loss.
35–40% total body weight loss can be fatal.
Protein–energy malnutrition occurs as a result of a relative or absolute deficiency of energy and protein. It may be primary, due to inadequate food intake; secondary, as a result of other illness and associated inflammation; or a combination of both. For many developing nations, primary protein–energy malnutrition remains a significant health problem. There are two distinct syndromes: kwashiorkor, which is caused by a deficiency of protein in the presence of adequate energy, and marasmus, which is caused by combined protein and energy deficiency.
In industrialized societies, malnutrition is more often a sequela of other diseases/illnesses, than to pure starvation. Although there is no universally accepted definition of malnutrition, there are a number of internationally recognized malnutrition assessment tools that have been developed in an effort to standardize malnutrition identification and promote nutrition interventions. Examples include the Subjective Global Assessment (SGA), the American Society for Parenteral and Enteral Nutrition (ASPEN) and Academy of Nutrition and Dietetics (AND) Criteria, and the European Society for Parenteral and Enteral Nutrition (ESPEN) Criteria. The ASPEN/AND criteria are widely used and unique in that they recognize the role of inflammation in the development of malnutrition and therefore propose an etiology-based diagnostic approach.
Protein–energy malnutrition affects every organ system. The most obvious results are loss of body weight, adipose stores, skeletal muscle mass and functional status. Weight losses of 5–10% are usually tolerated without loss of physiologic function, whereas losses of 35–40% of body weight can result in severe complications and death. In starvation, preservation of lean body mass is the goal, therefore loss of adipose tissue typically occurs first. In contrast, inflammation results in extreme catabolism with negative nitrogen balance that causes significant wasting of lean body mass.
As protein–energy malnutrition progresses, organ dysfunction develops. Hepatic synthesis of serum proteins decreases, and depressed levels of circulating proteins are observed. Cardiac output and contractility are decreased, and the ECG may show decreased voltage and a rightward axis shift. Autopsies of patients who die with severe undernutrition show myofibrillar atrophy and interstitial edema of the heart.
Respiratory function is affected primarily by weakness and atrophy of the muscles of respiration. Vital capacity and tidal volume are depressed, and mucociliary clearance is abnormal. The GI tract is affected by mucosal atrophy and loss of villi of the small intestine, resulting in malabsorption. Intestinal disaccharidase deficiency and mild pancreatic insufficiency also occur. This may be further exacerbated by the presence of inflammation.
Changes in immunologic ...