These symptoms can range from mild to severe and include chronic, watery, acidic diarrhea; intestinal gas and bloating; nausea; and abdominal pain.Infants may not show symptoms of CSID until they begin to eat sucrose- and starch-containing foods such as juices, solid foods, and medications sweetened with sucrose. Chronic, watery diarrhea and failure to thrive are the most common symptoms in infants and toddlers. Other symptoms include abdominal distention, gassiness, colic, irritability, excoriated buttocks, severe diaper rash due to acidic diarrhea, indigestion, and vomiting.Adults with CSID are usually lean, with a low body-mass index and an aversion to eating carbohydrates and “sweets.” Because CSID is an inherited condition, patients with CSID often have close relatives who also experience chronic diarrhea. Determining the cause of chronic gastrointestinal symptoms may take a long time because the symptoms can be common to many gastrointestinal conditions. One diagnostic method, considered the gold standard for diagnosing CSID, measures the level of activity of four intestinal enzymes that digest compound sugars, also called disaccharides. The four disaccharides digested in the small intestine are lactose, sucrose, maltose, and isomaltose.This diagnostic method, called a disaccharidase assay, is conducted on tissue samples taken from the small intestine during an endoscopic procedure, also called an upper GI (gastrointestinal) examination.
Diet modification
The level of ability to digest sucrose or starch sugars is unique to each person who is living with CSID and depends on many factors, including the following:
The individual level of function of the digestive enzyme sucrase-isomaltase
How well the other functions of the gastrointestinal tract are working
How much sucrose and starch sugars are consumed
If a person has any other health issues that may affect digestionFor these reasons, a restriction diet needs to be specific for each patient who has CSID. Before making any changes to the diet, it is important for a patient to speak with a healthcare provider, especially if the patient is underweight or not gaining weight as would be expected. It is also advised that the patient work with a registered dietitian or nutritionist who can help identify the foods that can be tolerated and those that cannot be tolerated. A registered dietitian or nutritionist can also help the patient plan a diet that will meet the nutritional needs for normal growth and development. Vitamins, minerals, and additional supplements may be needed to meet all nutritional needs. Epidemiology
The highest prevalence rates are seen in the Inuit populations of Greenland (5–10%), Alaska (3–7%), and Canada (about 3%). European descent prevalence ranges from 0.2% to 0.05%. There is a lower prevalence reported in African Americans and Hispanics compared to Caucasians. See also
Fructose malabsorption
Digestive system diseases
Lactose intolerance

References
External links
"Congenital sucrase-isomaltase deficiency". Genetic Home Reference. US National Library of Medicine.