Fat malabsorption in children

Introduction to pediatric fat malabsorption Fat malabsorption, also known as steatorrhea, is a syndrome caused by digestion and malabsorption of fat, which can be seen in many diseases such as pancreas, liver, gallbladder and intestinal diseases. The dysentery caused by intestinal lesions is accompanied by the absorption of other nutrients, which is called malabsorption syndrome. The small intestine is the main place to absorb various nutrients. Nutrients, especially fat, can not be absorbed by the small intestine due to various reasons, leading to diarrhea, malnutrition, weight loss, etc., called malabsorption syndrome. One of the types of diseases in the past is unknown, called idiopathic malabsorption syndrome or celiacisease, which is now known to be caused by allergies to gluten in wheat. basic knowledge The proportion of illness: 0.005% Susceptible people: children Mode of infection: non-infectious Complications: malnutrition, stunting

Causes of fat malabsorption in children

(1) Causes of the disease

Pancreatic disease (25%):

Pancreatic diseases cause decreased or lack of pancreatic exocrine secretion, intestinal absorption of fat digestion, fat diarrhea, pancreatic lipase secretion is often less than 10% of normal, severe steatorrhea is mainly seen in congenital cystic fibrosis, chronic Children with pancreatitis and pancreas.

Intestinal disease (20%):

Various reasons lead to reduced intestinal absorption area, mucosal surface lesions, intestinal wall infiltration and enzyme defects, etc., can affect the normal intake, processing and absorption of fat in the small intestine, found in intestinal infectious diseases, intestinal parasitic diseases, inflammatory Enteropathy (Crohn's disease, ulcerative colitis), short bowel syndrome, intestinal lymphatic obstruction (lymphosarcoma, Hodgkin's disease, intestinal tuberculosis, etc.).

Metabolism and other causes (18%):

Endocrine disorders, such as adrenal insufficiency, hypoparathyroidism; intestinal malabsorption syndrome due to other causes, Wolman's disease; hypogammaglobulinemia, immunoglobulin A heavy chain disease, no beta lipoproteinemia Connective tissue disease (scleroderma) and the like.

Reduced bile secretion (10%):

Biliary obstruction caused by various reasons, such as congenital biliary atresia, biliary tract infection; various liver diseases, such as cholestatic hepatitis, advanced cirrhosis.

In the above fat absorption process, any obstacle occurs in any part, which can cause malabsorption and lead to steatorrhea.

(two) pathogenesis

The fat in food is mostly triacylglycerol. When it enters the duodenum together with protein, it can promote the release of the cholestyramine (cholecystokinin), which promotes pancreatic secretion, gallbladder contraction and Oddi sphincter opening. After bile salt emulsification, it is easily catalyzed by water-soluble pancreatic lipase to decompose into monoglyceride and free fatty acid. The bile salt molecule has hydrophilic and lipophilic two poles, several bile salt molecules are enclosed, and the hydrophilic end Outward, the lipophilic end is inward, and the monoglyceride and the free fatty acid can be surrounded to form a water-soluble, micrometer (micelles) having a diameter of about 5 nm. The water-soluble property can prevent the particles from penetrating into the surface of the intestinal mucosa without movement (unstirred). In the liquid layer, the fat in the microparticles is absorbed by the brush-like edge of the intestinal mucosal epithelial cells by passive diffusion. The bile salts are still left in the intestinal lumen, and most of them are absorbed by the end of the ileum and enter the intestinal hepatic circulation, which can be reused.

The monoglyceride that enters the epithelial cells decomposes into fatty acids in the cells, and the fatty acid re-synthesizes triacylglycerol in the endoplasmic reticulum, and together with the phospholipid cholesterol and protein (apoprotein) synthesized by the cells, constitutes a relatively stable chylomicron. Lymphatic lymphatics and blood circulation.

Obstacles in any part of the above fat absorption process can cause malabsorption due to malabsorption, more common in various obstructive or reflux jaundice, including congenital biliary obstruction and toxic hepatitis infection, due to such children Lack of bile in the intestine, fat can not be emulsified; secondly seen in intestinal diseases, such as various intestinal infections, limited ileitis, ulcerative colitis, celiac disease (caliac disease), intestinal fistula, Major bowel resection and intestinal lymphatic obstruction (such as Hodgkin's disease, lymphosarcoma, intestinal tuberculosis and "exudative bowel disease", etc.), so-called exudative bowel disease with diarrhea, steatorrhea, edema and hypoproteinemia As the main performance, the intestinal lymphoid tissue is abnormal, so that the serum protein can be poured into the intestine. It can be proved by 131I-labeled albumin tracer and stool examination. The steatorrhea caused by lack of trypsin is found in congenital cystic fibrosis. Intestinal malabsorption syndrome due to abnormal metabolism and other causes is also a type of steatorrhea.

Pediatric fat malabsorption prevention

1. Actively prevent and treat malnourished diseases.

2, active treatment of various obstructive or reflux jaundice, treatment of various intestinal infectious diseases.

3, enhance physical fitness, improve their own immunity: pay more attention to rest, participate in physical exercise, eat more fresh fruits and vegetables rich in vitamins.

Pediatric fat malabsorption complications Complications, malnutrition, developmental delay

It is complicated by malnutrition, growth retardation, fat-soluble vitamin deficiency and mineral deficiency.

1. Malnutrition is due to insufficient intake of energy and/or protein, resulting in poor nutritional status or failure to maintain normal growth and development, mainly in infants under 3 years of age. There are three types of clinical common: lack of energy supply, manifested as significant weight loss, subcutaneous fat reduction is called weight loss; lack of protein supply, characterized by edema called edema, between the two Weight loss - edema type.

2. Stunting refers to the phenomenon of slowing down or abnormal order during growth and development. The incidence rate is between 6% and 8%. In normal internal and external environments, children can develop normally, and all factors that are not conducive to children's growth and development can affect their development to varying degrees, resulting in children's growth retardation.

3. Fat-soluble vitamins include vitamins A, D, E, and K. They are insoluble in water and soluble in lipids and fatty solvents. Fat-soluble vitamins coexist in the food with lipids and are absorbed along with the lipids. The absorbed fat-soluble vitamin is transported in the blood by specifically binding to lipoproteins and certain specific binding proteins. The fat-soluble vitamins A, D, E, and K have certain biological functions, and once they are lacking, the corresponding symptoms will appear.

Symptoms of fat malabsorption in children Common symptoms Growth slow fat diarrhea weight loss keratoconjunctival dryness weight loss loss of appetite diarrhea hypoproteinemia vitamin deficiency dehydration

1. General performance

Children with poor appetite, poor development, weight loss, weight loss, mental fatigue, crying, malnutrition, severe diarrhea can cause dehydration, electrolyte imbalance.

2. Diarrhea

Mainly manifested as steatorrhea, increased fecal volume and frequency, typical stool color, grayish white, oily, large amount, stench, fat can float on the water surface, with abdominal distension, abdominal pain, mental fatigue and crying.

3. Abdominal fullness

Because the intestinal storage does not digest food, and the intestinal muscles are weak, the gas is accumulated in the intestinal lumen.

4. Fat-soluble vitamin deficiency

Prolonged course of disease, prolonged course of fat malabsorption caused by extensive intestinal mucosal disease can cause fat-soluble vitamin deficiency, such as vitamin A deficiency eye disease, can show beating spots, corneal dryness, etc.; vitamin D deficiency can cause rickets, hand and foot sputum; vitamin E can cause proximal muscle atrophy; vitamin K causes bleeding tendency, prolonged prothrombin time, can cause hypoproteinemia, edema, nutritional anemia and intestinal dermatitis.

5. Other

Due to extensive absorption of intestinal tract, it is often accompanied by other nutrient absorption disorders, causing corresponding manifestations, such as hypoproteinemia, edema, nutritional anemia, intestinal dermatitis and secondary micronutrient deficiencies.

Pediatric fat malabsorption examination

1. Check fecal fat under the microscope

(1) Sultan III staining microscopy: Place the feces on a slide, add a few drops of 95% ethanol, and stain with Sudan III saturated ethanol (95%) solution. The neutral fat is yellow or orange round ball. In addition, put the feces on the slide, add a few drops of 36% acetic acid and Sudan III solution, mix the cover slides thoroughly, put them on the alcohol lamp and gently heat until boiling, after cooling, microscopic examination, fatty acid can be dyed into orange balls, mirror There are many lower fat globules. For example, if there are more than 6 visual fields per low magnification, it often indicates excessive fecal fat. This method is simple, but the sensitivity is poor. The medium and severe steatorrhea is positive.

(2) Take 1 drop of each of saturated saline solution of normal saline and scarlet dye, add a little stool to the slide, and cover with a cover glass to see the round bubble-shaped neutral fat and crystalline fatty acids, such as specimen 1/ 4 or more dyed red, for the test strong positive (or), for severe steatorrhea.

2. Iodine oil tolerance test

Give the child oral iodized oil (hydroiodide with poppy oil to make the iodine content up to 40%). The iodine is tightly combined with the unsaturated fatty acid in the vegetable oil. After dissolving in the digestive tract, it is dissociated and discharged from the urine. After 12 to 18 hours, the urine was collected and diluted in 7 tubes for urine. Each tube was 0.5 ml each, and 3 drops of freshly prepared 1% starch suspension were added for semi-quantitative iodine test, such as tube 4 (1: 8 dilution) or above shows blue is positive, indicating that the fat absorption of the digestive tract is normal, and those with a history of iodine allergy are hanged.

3. Determination of serum carotene

Carotene is the predecessor of vitamin A. The serum carotene content can reflect the absorption of fat indirectly. Under normal diet, the normal value of serum -carotene is 0.37~1.3mol/L (2070g/dl) for infants, 0.74 for children. ~ 2.42mol / L (40 ~ 130g / dl), in mild diarrhea, this lipoprotein is not easy to absorb, such as eating carrots or other carotenoid-rich foods in the diet, such as significantly lower, can be considered to have fat malabsorption , fat malabsorption often drops to 1 ~ 2g / L, this result is not affected by the amount of vitamin A, but eat more green, yellow vegetables, fruit sick children can appear false negative, not eating such food diseases Infants, such as infants under 8 months, may be false positives.

4. Fecal fat theorem to determine and calculate fat absorption rate

If the above simple method cannot be solved, the fat content of food and feces can be measured, and the absorption coefficient can be calculated.

The child consumes a normal diet containing a certain amount of fat every day. The fat calorie card accounts for at least 35% of the total calorie, for 5 days. The whole feces are collected every day for 3 days, and the fat absorption rate is calculated.

Fat absorption coefficient = [intake total fat (g) - total fat excretion (g)] / total fat intake (g) x 100%.

The rate of absorption in normal premature infants is 60% to 75%; in infants with full-term infants, 80% to 85%; the coefficient of normal children over 1 year old is 95% or higher, and the absorption rate is significantly lower, which can be diagnosed as fat malabsorption. Accurate, but the operation process is complicated, and it is often difficult for small children to collect feces. Sultan III staining microscopy and serum carotene screening methods can be used.

5. Blood test

Peripheral blood smear can detect small cell hypopigmentation or large cell anemia. It should be considered that there is no -lipoproteinemia in the erythrocyte, the serum cholesterol and triglyceride are low, and there is no lipoprotein, Shwachman-Diamond. The syndrome has peripheral neutropenia.

6. N-benzoyl-L tyrosine-p-carbamic acid BT-PABA test

It is a reliable and simple method for diagnosing pancreatic exocrine function. The principle is that chymotrypsin secreted by the pancreas can hydrolyze BT-PABA amino acid peptide bonds, while PABA is used as a marker in the intestinal lumen, and is absorbed into the blood circulation, excreted from the urine, pancreas When the secretion decreased, the PABA content in blood and urine decreased. To avoid false positives, the fruits and sulfonamides, chloramphenicol, diuretics, and traditional Chinese medicines were taken 3 days before the test. BT-PABA 250mg was taken on an empty stomach. After 2 hours, venous blood was taken or left for 6 hours. Urine, determination of PABA content, significantly lower, suggesting that pancreatic exocrine function is low.

7. Dextrose absorption and excretion test

Sugar is a kind of pentose sugar. It is absorbed by the jejunum after oral administration. It is not metabolized in the body and is excreted in the urine. Under normal renal function, the absorption and excretion of xylose can reflect the absorption function of the small intestine. Oral xylose is 14.5g/m2. , the maximum does not exceed 25g, after 1h test xylose blood concentration, normal >25mg / dl; can also take xylose 1g (10% solution), followed by drinking water l00 ~ 200ml, collect 5h urine test xylose, normal discharge > 0.25g For example, blood or urinary xylose is significantly reduced, suggesting that the jejunal mucosa has extensive damage, and it can be indirectly inferred that fat malabsorption is caused by intestinal mucosal damage, and has nothing to do with simple pancreatic exocrine or bile salt deficiency.

8. Vitamin B12 absorption test

In the Schilling test, after the combination of vitamin B12 and internal factors, it is absorbed from the end of the ileum. After the vitamin B12 is stored in the body, the excess B12 is excreted from the urine. In the test, the muscle is injected with a sufficient amount of vitamin B12 to saturate the body. Oral radionuclide 60Co (60Co) labeled vitamin B12 trace, leaving 24h urine test for vitamin B12 emission, such as discharge less than 5% of intake, such as sick children without internal factor deficiency, suggesting that the ileal mucosa has Extensive injury, including surgical resection, intestinal bile salts are reduced to deoxycholic acid or lithocholic acid by bacteria, and most of them are reabsorbed by the end of the ileum. After liver treatment, they can be re-extracted into the intestine through the biliary tract to help fat absorption. When there is extensive damage at the end of the ileum, it often indicates the absorption of bile salts and the decrease of bile salt pool. The fat malabsorption may be related to the lack of bile salts.

9. Duodenal drainage check

The content of bile acid, pancreatic lipase and trypsin can be directly measured, and the trophozoite can be found by microscopic examination of Giardia infection drainage liquid. The bacterial culture colony count can help to diagnose the excessive reproduction of bacteria in the upper part of the small intestine.

10. Small intestinal mucosa biopsy

Biopsy can be performed by endoscopic or oral biopsy catheter for small intestinal mucosa. Direct observation of mucosal lesions, diagnosis of celiac disease, no beta lipoproteinemia, enteric dermatitis, intestinal lymphatic dilatation, milk or beans Protein allergy, tropical stomatitis diarrhea and Giardia can be helpful, and biopsy specimens can measure disaccharidase activity, fat malabsorption with disaccharidase activity decline, often suggesting that intestinal mucosal lesions are more extensive.

B-ultrasound, electrocardiogram and X-ray examination are routinely used to assist diagnosis and differential diagnosis. For example, abdominal B-ultrasound can detect abnormalities in the pancreas and biliary tract. Foreign pancreatic cystic changes are a common cause of steatorrhea. It is reported that the amount of sodium chloride in sweat is increased in this disease.

Diagnosis and differential diagnosis of pediatric fat malabsorption

diagnosis

According to the characteristics of clinical manifestations, relying on laboratory tests to confirm the diagnosis.

When clinical suspected steatorrhea, it should first be confirmed by laboratory examination whether it is steatorrhea, quantitative determination of fecal fat, is the only more accurate method, but the operation is complicated, it is difficult to collect feces, you can first use Sudan III staining microscopy Screening with serum carotene determination method, after clearing of steatorrhea, the cause should be further confirmed by medical history, physical examination and necessary laboratory tests. N-benzoyl-L tyrosine-p-carbamic acid BT-PABA test is A reliable and simple method for diagnosing pancreatic exocrine function; fecal Sudan III stained fecal fat is mainly composed of neutral fat, pancreatic steatorrhea should be considered; fatty acid is the main, often suggesting intestinal mucosal lesions; D-xylose absorption and excretion test results such as Blood or urine xylose is significantly reduced, suggesting that the jejunal mucosa has extensive damage. It can be inferred that fat malabsorption is caused by intestinal mucosal damage, but not related to simple pancreatic exocrine or bile salt deficiency.

Differential diagnosis

Different from other malabsorption syndromes:

1. Sugar malabsorption (Sugar malabsorption) In normal human lactose, it is absorbed by glucose and galactose by the lactase of the small intestinal mucosa. The lactose deficiency in the small intestinal mucosa is caused by various reasons, so that the lactose characteristic in milk cannot be Fully hydrolyzed and absorbed in the small intestine, causing lactose malabsorption, sugar malabsorption can be divided into two major categories, primary and secondary, causing diseases of primary glucose malabsorption, congenital lactose malabsorption, Sucrose-isomaltase deficiency, glucose-galactose malabsorption, and the like. Diseases that cause damage to intestinal mucosal epithelial cells and brush borders, such as viral enteritis, chronic diarrhea, protein-calorie malnutrition, immunodeficiency disease, and small bowel surgery, can cause secondary glucose malabsorption.

Those with clinical signs and symptoms of glucose malabsorption are called sugar intolerance. The clinical manifestation is that children have osmotic diarrhea after eating dairy foods. They are watery stools, no increase in fecal fat, and acid smell. There are foams, often abdominal discomfort, abdominal distension, increased exhaustion, severe water, electrolytes and acid-base balance disorders, once you stop eating dairy foods or remove intolerant sugars, diarrhea symptoms can be quickly relieved, this One of the characteristics of this disease.

Laboratory examination of sugar malabsorption:

(1) The stool pH is often <5.5, suggesting that the sugar is poorly absorbed.

(2) Fecal reducing sugar determination: Clinitest test paper, modified class reagent or lead acetate method can be used for reducing sugar determination, such as 0.005 indicating poor glucose absorption.

(3) sugar-expiratory test, the normal person can completely absorb most of the absorbable sugar before reaching the colon, and the intestinal bacteria fermentation metabolism is not absorbed by the sugar exhaled by the human body. The only source of hydrogen in this method can be used to determine the malabsorption of sugar in the small intestine. Before and after ingesting some test sugar, the hydrogen or 14CO2 in the breath is measured. After the test sugar is ingested, the expiratory hydrogen is raised or called. A decrease in gas 14CO2 indicates poor absorption of sugar for the test.

(4) Determination of disaccharidase activity in small intestinal mucosa biopsy: in patients with poor glucose absorption, one or several disaccharidase activities were reduced.

(5) lactose tolerance test: lactose tolerance test: oral lactose 50g, blood glucose measurement every 30min, a total of 2h, normal people after oral lactose, than the fasting blood glucose increased by 1.1mmol / L (20mg / dl) or more; lactase Lack of blood glucose curve is low, and lactose intolerance appears. This test has been used for several times because it requires multiple blood draws.

2. Protein malabsorption Protein malabsorption is rare. It is usually caused by fat or sugar malabsorption when the intestinal mucosa is extensively damaged. The clinical manifestation is that the color of the stool is light, and there is a smell of stinky eggs. Symptoms associated with hypoproteinemia, such as edema, ascites, etc., while urine protein is often negative.

Laboratory examination of protein malabsorption:

(1) Total serum protein, albumin decreased and no urine protein increased.

(2) intravenous injection of 25 ~ 50U 51Cr (chromium) labeled albumin, and then measured the discharge rate of 51Cr in the feces within 96h, the normal value is 0.001 ~ 0.007, such as increased discharge, suggesting protein absorption.

(3) Determination of 1 antitrypsin in feces, 1 antitrypsin is not decomposed in pancreatic enzyme, even if it is excreted into feces, it is stable, so the protein can be obtained by measuring the concentration of 1 antitrypsin in blood and feces. The extent of leakage, the normal value of dry manure is 0.8-1.0 mg, and >2.6 mg is malabsorption of protein.

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