Malabsorption and Maldigestion

The pancreatic disease, with severe fibrosis and cystic changes on pathologic examination (Figure 140-1), is present in the severe mutations, and accounts for the PI of these patients. CFTR in the pancreas is localized to the luminal surface of ductular cells, and malfunction of this channel, which is known to transport both chloride and bicarbonate ions, leads to acidic and viscous secretions blocking pancreatic exocrine outflow. With screening for pancreatic function in early life, about 40% of infants have pancreatic sufficiency (PS) (defined as < 7% loss of ingested fat on a 72-hour fecal fat collection), but by the age of about 5 years, this has declined to approximately 15% of cases. This screening for pancreatic function is not an easy task, as the methods of checking for PS are difficult or invasive. The standard clinical test is a 72-hour fecal fat measure (Van de Kamer et al, 1949). Loss of any stool during collection would favour a more normal report of fecal fat loss. In addition to stool collection, a diet record of weighed food ingested should be obtained for 5 days, with the stool collection occurring during the last 3 days. The average daily fat lost t, ■. ;

FIGURE 140-1. Pathologic examination of pancreatic disease.

in the stool is then assessed as a percent of the average daily fat ingested. The normal value is fecal loss of < 7 % of ingested fat. Patients with PI will have a loss of fat usually in the range of 20 to 50%. This testing should be performed on all patients at the time of diagnosis to assess pancreatic function. It should also be repeated on patients who are initially assessed as having PS when there is a change in GI symptoms or any faltering of growth.

Other testing for pancreatic function includes the use of a monoclonal antibody based enzyme-linked immunoas-say test for human pancreatic elastase 1 in the stool. An aliquot from a 24-hour stool collection is assayed. Human elastase 1 is not present in porcine pancrease supplemental enzymes, so this test is convenient to perform while the patient is receiving pancreatic enzyme supplements. This test is both sensitive (96%) and specific (100%) for CF patients with PI when compared with healthy subjects and those with nonpancreatic diseases (Gullo et al, 1997; Soldan et al, 1997). It is also somewhat more acceptable than a 72hour fecal fat for those asked to perform the test. This test will sort patients into those that have PS and those who have PI, and can be used to judge the requirement for pancreatic enzymes. More recently it has also been used to track the decline in exocrine pancreatic function in PS CF patients (Walkowiak et al, 2003). It cannot be used to test for the efficacy of enzyme therapy, or to monitor the effect of changes or additions to therapy, such as the use of acid suppressants. A 72-hour fecal fat is needed for this.

A further test for pancreatic function, the pancreatic stimulation test, involves insertion of a nasoduodenal tube and the administration of secretagogues (secretin/chole-cystokinin) to stimulate the flow of pancreatic juice. The collected secretions can then be assessed for pH and enzyme content. Technical challenges make these tests very demanding, and patients with PS have a significant chance of being misclassified as having PI (Schibli et al, 2003); therefore, this is not usually performed in the clinical setting, but is very useful for research clinical investigations. Endoscopic aspiration of pancreatic fluid following secretin stimulation is not recommended as it has even greater potential for mis-classification of pancreatic functional status.

Nutrition

The majority of CF patients have PI, and consequent steat-orrhea and azotorrhea, and are predisposed to gross malnutrition. We know that the growth failure of children and youth with CF is not intrinsic to the disease, but remediable with provision of sufficient energy and protein along with supplemental pancreatic enzymes as needed. There is also evidence that improved nutrition helps stabilize lung function, improves quality of life, and may prolong life. Estimates of energy requirements for patients with CF are clearly higher than normal and should be based on weight gain and body fat stores. The quality of the diet can fit with normal recommendations for nutrient mix, recognizing the importance of fat as the most energy dense nutrient, and the one that makes our food most palatable. Formerly recommended restrictions on fat intake to improve GI discomfort and other symptoms should be entirely abandoned. Pancreatic replacement enzymes on the market at present are derived from pig pancreas (eg, trade names Pancrease, Cotazym, Creon, Ultrase), although newer crystalline synthetic enzymes are in trials. The appropriate use of enzymes has been carefully examined in the last decade since the first appearance of fibrosing colonopathy. The Consensus Statement (Borowitz et al, 2002,) of the Cystic Fibrosis Foundation recommends the following dosing guidelines: Infants: 2,000 to 4,000 Units lipase per 120 mL formula or breast feed

Children < 4 years: 1,000 to 2,500 Units lipase per kg per meal

Children and adults: 500 to 2,500 Units lipase per kg per meal

Plus: half the standard meal dose with snacks Or

Enzyme dose < 10,000 Units lipase per kg per day Beyond these recommendations, lipase dosing based on grams of fat in the diet is a rational approach. Standards of care support a maximum dose of4,000 U lipase per gram fat per day (Fitzsimmons et al, 1998). This cut off keeps doses of lipase well below those reported with colonic strictures. The differential diagnosis of patients with ongoing abdominal complications while taking the maximum enzyme dose is listed in Table 140-2.

As most of the enzymes in clinical use are enteric coated to protect them from stomach acid, use of an H2RA or PPI to raise duodenal pH can enhance enzyme function. The best test of improved absorption is a 72-hour fecal fat measure.

Monitoring success in treating malabsorption and malnutrition is done in children by the careful assessment of growth throughout childhood and adolescence. For adults, maintenance of a normal and stable body mass index (BMI) should be sought. We want our young patients to achieve normal growth, not only when compared with the National Center for Health Statistics (NCHS)/Centers for

TABLE 140-2. Differential Diagnoses of Patients With Ongoing Abdominal Complaints While Taking the Maximum Enzyme Dose

Lactose intolerance Giardiasis Biliary disease Short bowel syndrome Bacterial overgrowth Enteric bacterial infection Celiac disease Crohn's disease Fibrosing colonopathy

Disease Control and Prevention (CDC) growth curves (CDC Web site, <http://www.cdc.gov/growthcharts>), but when assessed by growth potential as estimated by mid-parental height. Diligence should be taken in obtaining accurate heights with a wall-mounted stadiometer, and weights with minimal standard clothing, and plotting the values on the CDC growth charts, including values for head circumference and weight for height or BMI. As well as the standard measures, the Consensus Report on Nutrition (Borowitz et al, 2002) recommends mid-arm circumference and triceps skinfold be measured annually as a marker of body composition. Special vigilance on growth and nutritional status should be given at the time of diagnosis, during infancy, and during the pubertal growth spurt. We are much closer now to achieving normal growth of our patients when comparing height and weight to population standards, but there is room still for improvement.*

Along with the loss of macronutrients, pancreatic insufficient patients are at risk for deficiencies in fat-soluble vitamins (A, D, E, and K), and essential fatty acids, and for the consequences of these deficiencies particularly on bone mineral accretion, neurological function, and membrane integrity. Patients with PI are routinely supplemented with fat-soluble vitamins at between one and two times the normal. Much work on essential fatty acid levels (linoleic acid [18:2n-6] and alpha-linolenic acid [18:3n-3], and the longer products, arachidonic acid [20:4n-6] and eicos-apentanoic acid [20:5n-3] and docosahexanoic acid [22:6n-3]) has been done. Although recommendations for routine supplementation have not been made, assurance of intake of these fatty acids within the high fat diet is a prudent recommendation. The quality of supplemental dietary fat should be assessed by the dietitian to minimize saturated and trans fatty acids. As well, an emphasis on medium chain triglycerides as a source of energy is unnecessary. Routine annual monitoring of fat-soluble vitamin levels (vitamin A, 25-OH-D, a-tocopheral and prothrombin time) is currently recommended. Other micronutrients including iron, calcium and zinc, although clearly essential, have no specific recommendations, except for a yearly hemoglobin and hematocrit as surrogates for iron nutriture, and ensuring at least normal intake of the others.

Nutrition support for those starting to fall below channel (percentile line) on the growth curves can be enhanced in a step-wise fashion as required, including oral supplementation, nasogastric (NG) feeds for short term gain, and surgically-placed enteral tube feeds for long term nocturnal nutrition support (gastrostomy or jejunostomy tubes). There is some evidence that oral supplements merely replace food (Pencharz and Durie, 2000), but with some patients weight gain occurs. The energy provided by these additional supplements is often > 50% of the patients total

*Editor's Note: This same attention to growth should be exercised when caring for prepubescent adolescents with Crohn's disease.

energy intake. However, with increased severity of pulmonary disease, increased inflammation and anorexia, patients are not able to ingest the required additional energy, but do tolerate enteral infusions, usually provided overnight. This care is an additional significant burden for families and requires a lot of support and encouragement from the care team.

Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

Get My Free Ebook


Post a comment