from the osmotic effects of malabsorbed carbohydrates or the secretory effects of malabsorbed bile acids. Increased gaseousness with excessive belching or flatulence and abdominal bloating and/or distention occurs commonly and typically results from the fermentation of malabsorbed carbohydrates by colonic microbiota. Although weight loss is prevalent in individuals with severe forms of malabsorption, those with less severe forms may not present with weight loss. The pattern of weight loss also may vary, with some individuals losing weight early on in the process with subsequent stabilization, and others with progressive weight loss. Abdominal pain, aside from cramping associated with defecation, is not a common complaint among those with malabsorption. Major exceptions include individuals with chronic pancreatitis or Crohn disease who have undergone multiple bowel resections. Nausea, emesis, borborygmi, and anorexia (or hyperphagia) also may be seen occasionally. In addition to the classic symptoms of steatorrhea noted, other characteristics of stool output should be noted, including typical volumes, number of stools per day, characteristics (e.g., watery, semiformed), presence of visible food, incontinence, and temporal characteristics (e.g., stool outputs in relation to meals).
TABLE 75.1 SYMPTOMS AND LABORATORY EVALUATION OF SPECIFIC NUTRIENT MALABSORPTION
include information regarding timing of symptom onset; bowel habits and stool characteristics; presence of growth failure, delayed sexual maturation, and weight loss or gain; associated gastrointestinal and other systemic symptoms; presence of concomitant chronic systemic, gastrointestinal, pancreaticobiliary, or liver disorders; prior surgery to the gastrointestinal tract; history of radiation exposure to the gut; travel history; diet; prescription, alcohol, and illicit drug use; high-risk sexual behavior; and family history. Pertinent aspects on examination to identify include muscle wasting, skin rash/lesions, oral lesions, edema, abdominal distention, tenderness, and organomegaly and other potential signs of micronutrient deficiencies. Together with the history and examination, initial “routine” blood tests such as a complete blood count, chemistry panel, prothrombin time, magnesium, ferritin, folate, and vitamin B12 may provide evidence in support of the presence of malabsorption and further focus the investigative testing required to identify the specific malabsorptive process involved. Celiac serology also should be considered as a first-line diagnostic test in patients suspected of having malabsorption (see the chapter on celiac disease). Stool testing for occult blood and chronic infectious etiologies also should be considered at this stage.
TABLE 75.2 CAUSES OF MALABSORPTION
test (5), which involves the measurement of breath CO2 following the ingestion of radiolabeled triolein, a triglyceride. Despite their simplicity and reportedly good test characteristics, none of these tests appears to be widely used in the United States.