Gastroenterology Chapter 7 Maldigestion and Malabsorption

9. Maldigestion and Malabsorption: The Malassimilation Syndromes

page 206

Normal digestion and absorption of foods is essential for life and well-being. Given the length of the gastrointestinal tract, the number of organs involved in digestion, and the large number of nutrients that must be taken into our bodies, it is not surprising to find a large number of disease states that impair the processes of food digestion and absorption. Clinical malassimilation occurs in only one of two ways: (1) through intraluminal disorders (maldigestion of food) and (2) through intramural disorders (malabsorption of food).

9.1 Clinical Manifestations

page 206

The list of diseases that can cause malassimilation is long (Table 3), necessitating logical history-taking.

Clinical suspicion, as always, comes from the patient's history and physical examination.

TABLE 3. Classification of malassimilation syndromes
Defective intraluminal digestion	Defective intramural absorption
Mixing disorders Postgastrectomy Pancreatic insufficiency Primary Cystic fibrosis Secondary Chronic pancreatitis Pancreatic carcinoma Pancreatic resection Reduced intestinal bile salt concentration Liver disease Hepatocellular disease Cholestasis (intrahepatic or extrahepatic) Abnormal bacterial proliferation in the small bowel Afferent loop stasis Strictures Fistulas Blind loops Multiple diverticula of the small bowel Hypomotility states (diabetes, scleroderma, intestinal pseudo-obstruction) Interrupted enterohepatic circulation of bile salts Ileal resection Ileal inflammatory disease (regional ileitis) Drugs (by sequestration or precipitation of bile salts) Neomycin Calcium carbonate Cholestyramine	Inadequate absorptive surface Intestinal resection or bypass Mesenteric vascular disease with massive intestinal resection Regional enteritis with multiple bowel resections Jejunoileal bypass Mucosal absorptive defects Biochemical or genetic abnormalities Celiac disease Disaccharidase deficiency Hypogammaglobulinemia Abetalipoproteinemia Hartnup disease Cystinuria Monosaccharide malabsorption Inflammatory or infiltrative disorders Regional enteritis Amyloidosis Scleroderma Lymphoma Radiation enteritis Eosinophilic enteritis Tropical sprue Infectious enteritis (e.g., salmonellosis) Collagenous sprue Nonspecific ulcerative jejunitis Mastocytosis Dermatologic disorders (e.g., dermatitis herpetiformis) Lymphatic obstruction Intestinal lymphangiectasia Whipple's disease Lymphoma

A patient with malassimilation may have symptoms and signs of specific nutrient deficiencies or those of the underlying disease process itself (e.g., Crohn's disease). Furthermore, considering that malassimilation usually involves multiple nutrients, the symptoms and signs of a malassimilation state can vary from a straightforward presentation to myriad symptom complexes (Table 4 and Table 5).

TABLE 4. Clinical signs and symptoms of malassimilation
	Clinical sign or symptom	Deficient nutrient

General	Weight loss Loss of appetite, amenorrhea, decreased libido	Calorie Protein energy
Skin	Psoriasiform rash, eczematous scaling Pallor Follicular hyperkeratosis Perifollicular petechiae Flaking dermatitis Bruising Pigmentation changes Scrotal dermatosis Thickening and dryness of skin	Zinc Folate, iron, vitamin B₁₂ Vitamin A Vitamin C Protein energy, niacin, riboflavin, zinc Vitamin K Niacin, protein energy Riboflavin Linoleic acid
Head	Temporal muscle wasting	Protein energy
Hair	Sparse and thin, dyspigmentation Easy to pull out	Protein
Eyes	History of night blindness Photophobia, blurring, conjunctival inflammation Corneal vascularization Xerosis, Bitot's spots, keratomalacia	Vitamin A Riboflavin, vitamin A Riboflavin Vitamin A
Mouth	Glossitis Bleeding gums Cheilosis Angular stomatitis Hypogeusia Tongue fissuring Tongue atrophy Scarlet and raw tongue Nasolabial seborrhea	Riboflavin, niacin, folic acid Vitamin C, riboflavin Riboflavin Riboflavin, iron Zinc Niacin Riboflavin, niacin, iron Niacin Pyridoxine
Neck	Goiter Parotid enlargement	Iodine Protein
Thorax	Thoracic 'rosary'	Vitamin D
Abdomen	Diarrhea Distention Hepatomegaly	Niacin, folate, vitamin B₁₂ Protein energy Protein energy
Extremities	Edema Softening of bone Bone tenderness Bone ache, joint pain Muscle wasting and weakness Muscle tenderness, muscle pain Hyporeflexia	Protein, thiamine Vitamin D, calcium, phosphorus Vitamin D Vitamin C Protein, calories Thiamine Thiamine
Nails	Flattening, brittleness, luster loss, spooning Transverse lines	Iron Protein
Neurologic	Tetany Paresthesias Loss of reflexes, wrist drop, foot drop Loss of vibratory and position sense, ataxia Dementia, disorientation	Calcium, magnesium Thiamine, vitamin B₁₂ Thiamine Vitamin B₁₂ Niacin
Blood	Anemia Hemolysis	Iron, vitamin B₁₂, folate Phosphorus

The patient who gives a history of progressive weight loss, polyphagia, excessive flatus, diarrhea, bulky and foul-smelling stools, food particles or fat in the stool, abdominal distention, muscle wasting, bone pain, bleeding, weakness, tetany, paresthesia, glossitis, cheilosis or dermatitis is giving you the "classical" history of severe intestinal malassimilation. Rarely will you hear such a history from a patient in North America. It is far more common to see patients who will have vague symptoms for which there is some abnormality in their blood chemistry that alerts you to the presence of disease.

Early symptoms of the disease may easily be overlooked, and a severely malnourished state may come to exist. Often a patient will have noticed "early" symptoms, which will become apparent only when questioned directly. Hence, the physician must inquire about minor changes in bowel habits occurring before the onset of weight loss, hyperphagia, pain, anorexia or gross changes in bowel habits. Subtle changes in stool volume or bulk (manifested by a slight increase in the number of bowel movements per day), consistency or odor are early manifestations of malassimilation. A slight increase in the frequency of stools occurring at a time when the patient is mildly anorexic occurs a long time before disease becomes clinically apparent. An early increase in bulk of the stool is caused by increased water and gas content and leads to an inability to flush the stool easily.

TABLE 5. Specific vitamin and mineral deficiencies
Vitamin/mineral		Clinical manifestation

Vitamin A	Eyes	Night blindness Xerosis (dry bulbar conjunctiva) Bitot's spots (conjunctiva plaques) Keratomalacia (corneal ulceration)
	Skin	Hyperkeratosis
Vitamin B₁₂	Hematologic, neurologic systems	Anemia Nonreversible loss of vibratory and position sense Paresthesia
	Gastrointestinal	Diarrhea
Vitamin C	Skin	Perifollicular papules (brittle hair) Perifollicular hemorrhages Gum bleeding Skin purpura, ecchymosis
Vitamin D	Bone	Bone pain and softening Joint pain Rickets Proximal myopathy
Vitamin K		Bruising Bleeding
Vitamin B₆ (Pyridoxine)	Skin	Seborrheic dermatitis Cheilosis Glossitis
Niacin		Dermatitis Diarrhea Dementia
Thiamine	CVS CNS	Congestive heart failure Wernicke's encephalopathy Wernicke-Korsakoff syndrome
Zinc	Skin	Acrodermatitis enteropathica Alopecia
	Taste	Hypogeusia
Folate	Hematologic, neurologic systems	Anemia Reversible loss of position and vibratory sense

CVS = cardiovascular system; CNS = central nervous system

It is not uncommon for the patient to think the toilet is malfunctioning because several flushings are needed to remove the stool. A greasy character and truly rancid odor are indicative of increased stool fat, but are often absent until late. These complaints are often readily passed over by the busy physician. At such time, physical findings are usually absent, but hyperactive bowel sounds may be noted, especially in small intestinal disease. If symptoms are intermittent or if they progress slowly over many years, patients may exhibit vague, seemingly unrelated symptoms such as chronic fatigue and depression, long before the physician considers the possibility of serious organic disease.

9.2 Manifestations of Carbohydrate Malassimilation

page 209

Carbohydrate malassimilation will result in both specific and generalized symptoms. Specific to the maldigestion and malabsorption of carbohydrates are diarrhea and excess flatus. Unfortunately, everyone has flatus, and a definition or measure of excessive "wind" is lacking. Malabsorbed carbohydrates that enter the colon are fermented by colonic bacteria to gases (CO₂, H₂ and CH₄) and organic acids (Figure 12). These organic acids produce diarrhea by acting directly on colonic epithelium to stimulate fluid secretion and by their osmotic effect, which further draws water into the lumen. The presence of organic acids in the stool reduces the pH below 6 and suggests carbohydrate malassimilation. The gas produces flatulence, with associated borborygmi and abdominal distention. The presence of intraluminal H₂ gas, eventually absorbed into the circulation and exhaled, forms the basis of the hydrogen breath test to detect carbohydrate malabsorption. Physical examination often reveals a distended tympanitic abdomen with hyperactive bowel sounds. Stools seem to float on the water because of their increased gas content (not because of their fat content).

Generally, lack of carbohydrate as an energy source will result in decreased plasma insulin levels, increased plasma glucagon and cortisol levels and decreased peripheral T₄-to-T₃ conversion. Given sufficient time, the body will enter a state of oxidative metabolism: fat and muscle will be catabolized. Physical examination may reveal signs of weight loss from both fat stores and lean body mass. The patient will be weak and will easily develop fatigue. Fat loss will generally be noted as sunken cheeks and flat buttocks, with wrinkled or loose skin indicative of loss of subcutaneous fat stores. The loss of muscle mass is easily noted as thenar mass reduction and sunken soft tissues between the extensor tendons on the dorsum of the hands. There may be direct evidence of a reduced metabolic rate secondary to decreased T₃ conversion. The patient will often be mentally slowed.

9.3 Manifestations of Fat Malassimilation

page 211

Failure to digest or absorb fats results in a variety of clinical symptoms and laboratory abnormalities. These manifestations are the result of both fat malassimilation per se and a deficiency of the fat-soluble vitamins. In general, loss of fat in the stool deprives the body of calories and contributes to weight loss and malnutrition. More specific is the action of unabsorbed long-chain fatty acids, which act on the colonic mucosa to cause diarrhea by an irritant effect on the colon. In addition, fatty acids bind calcium, which would normally be available to bind oxalate. In fat malabsorption, oxalate is not bound to calcium and remains free (undissociated) within the colonic lumen, where it is readily absorbed. This results in oxaluria and calcium oxalate kidney stones. This occurs in Crohn's disease more readily than in other cases of fat malabsorption (steatorrhea).

Failure to absorb the fat-soluble vitamins A, D, E and K also results in a variety of symptoms. Vitamin K deficiency presents as subcutaneous, urinary, nasal, vaginal and gastrointestinal bleeding. Deficiencies in factors II, VII, IX and X produce defective coagulation. Vitamin A deficiency results in follicular hyperkeratosis. Vitamin E deficiency leads to a progressive demyelination of the central nervous system. Malabsorption of vitamin D causes rickets and osteopenia, as discussed later.

9.4 Manifestations of Protein Malassimilation

page 212

Severe loss of body protein may occur before the development of laboratory abnormalities. Impaired protein synthesis from liver diseases and excessive protein loss in renal disease can further aggravate protein deficiencies. Clinically, protein deficiency results in edema and diminished muscle mass. Since the immune system is dependent upon adequate proteins, protein deficiency can manifest as recurrent or severe infections. Protein deficiency in children results in growth retardation, mental apathy and irritability, weakness and muscle atrophy, edema, hair loss, deformity of skeletal bone, anorexia, vomiting and diarrhea. Protein-calorie malnutrition is known as marasmus, whereas protein malnutrition by itself is known as kwashiorkor.

CONTINUE to see part 2 of this subsection