AUTHOR: Fred F. Ferri, MD
Definition
Malabsorption is the diminished intestinal absorption of dietary nutrients. The majority of malabsorption is due to either congenital or acquired defects in the membrane transport system, absorption, and brush border processing in the intestinal epithelium.
Synonym
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Physical Findings & Clinical Presentation
- Most commonly nonspecific symptoms such as abdominal flatulence and distention are seen.
- Due to the osmotic load from maldigestion/malabsorption, watery diarrhea may be present. In the case of fat digestive disorder, steatorrhea ensues.
- Weight loss is very common, but many patients are able to compensate by increased caloric load. Diffuse disease often has much more pronounced weight loss.
- Chronic protein malabsorption can cause hypoalbuminemia, leading to edema and ascites.
- Both microcytic and macrocytic anemia can result from micronutrient deficiency (iron/B12). These patients can be pale and present with fatigue.
- Bleeding disorders from vitamin K deficiency can lead to ecchymosis, melena, and hematuria.
- Vitamin D deficiency can lead to bone disorders. Secondary hyperparathyroidism can be a presenting feature.
- Electrolyte and vitamin deficiency can lead to neurologic disorders such as ataxia, weakness, and neuropathy, and may have positive Chvostek or Trousseau sign.
- Autoimmune disease-specific dermatologic findings such as alopecia, pellagra, erythema nodosum, pyoderma gangrenosum, cheilosis, glossitis, and aphthous ulcers may be present.
- Cardinal clinical features of specific malabsorptive disorders are summarized in Table 1.
TABLE 1 Cardinal Clinical Features of Specific Malabsorptive Disorders
| Disorder | Cardinal Clinical Features | ||
|---|---|---|---|
| Adrenal insufficiency | Skin darkening, hyponatremia, hyperkalemia | ||
| Amyloidosis | Renal disease, nephrotic syndrome, cardiomyopathy, neuropathy, carpal tunnel syndrome, macroglossia, hepatosplenomegaly | ||
| Bile acid deficiency | Ileal resection or disease, liver disease | ||
| Carcinoid syndrome | Flushing, cardiac murmur | ||
| Celiac disease | Variable symptoms: Dermatitis herpetiformis, alopecia, aphthous mouth ulcers, arthropathy, neurologic symptoms, and (life-threatening) malnutrition; elevated liver biochemical test levels, mild iron deficiency | ||
| Crohn disease | Arthritis, aphthous mouth ulcers, episcleritis, uveitis, pyoderma gangrenosum, erythema nodosum, abdominal mass, fistulas, perianal fistulae, primary sclerosing cholangitis (PSC), laboratory signs of inflammation | ||
| CF | Chronic sinopulmonary disease, meconium ileus, distal intestinal obstruction syndrome (DIOS), elevated sweat chloride | ||
| Cystinuria, Hartnup disease | Kidney stones, dermatosis | ||
| Diabetes mellitus | Long history of diabetes and diabetic complications | ||
| Disaccharidase deficiency | Bloating and cramping, intermittent diarrhea | ||
| GI fistulas | Previous intestinal surgery or trauma, Crohn disease | ||
| Glucagonoma | Migratory necrolytic erythema, enlarged gallbladder | ||
| Hyperthyroidism, hypothyroidism | Symptoms and signs of thyroid disease | ||
| Hypogammaglobulinemia | Recurrent infections | ||
| Intestinal ischemia | Other ischemic organ manifestations; abdominal pain with eating (chronic mesenteric ischemia) | ||
| Lymphoma | Enlarged mesenteric or retroperitoneal lymph nodes, abdominal mass, abdominal pain, fever | ||
| Mastocytosis | Urticaria pigmentosum, peptic ulcer | ||
| Mycobacterium avium complex infection | AIDS | ||
| Pancreatic insufficiency | History of pancreatitis, abdominal pain, or alcoholism; large-volume fatty, oily stools; passage of orange oil | ||
| Parasitic infection | History of travel to endemic areas | ||
| PBC | Jaundice, itching | ||
| Scleroderma | Dysphagia, inability to open the mouth widely, Raynaud phenomenon, skin tightening | ||
| SIBO | Previous intestinal surgery, motility disorder (scleroderma, pseudo-obstruction), small intestinal diverticula, strictures | ||
| Tropical sprue | History of travel to endemic area | ||
| Tuberculosis | Specific history of exposure, living in or travel to endemic area, immunosuppression, abdominal mass or intestinal obstruction, ascites | ||
| Whipple disease | Lymphadenopathy, fever, arthritis, cerebral symptoms, heart murmur (pulmonary valve), oculomasticatory myorhythmia | ||
| ZES | Peptic ulcers, diarrhea |
AIDS, Acquired immunodeficiency syndrome; CF, cystic fibrosis; GI, gastrointestinal; PBC, primary biliary cholangitis; SIBO, small intestinal bacterial overgrowth; ZES, Zollinger-Ellison syndrome.
From Feldman M et al: Sleisenger and Fordtran’s gastrointestinal and liver disease, ed 10, Philadelphia, 2016, Elsevier.
Etiology
- Can be congenital or acquired.
- Disease-specific etiology. Mechanisms of malabsorption, malabsorbed substrates, and representative causes are summarized in Table 2.
TABLE 2 Mechanisms of Malabsorption, Malabsorbed Substrates, and Representative Causes
| Pathophysiologic Mechanism | Malabsorbed Substrate(s) | Representative Causes |
|---|---|---|
| Maldigestion | ||
| Conjugated bile acid deficiency | Fat Fat-soluble vitamins Calcium Magnesium | Hepatic parenchymal disease Biliary obstruction SIBO with bile acid deconjugation Ileal bile acid malabsorption CCK deficiency |
| Pancreatic insufficiency | Fat Protein Carbohydrate Fat-soluble vitamins Vitamin B12 (cobalamin) | Congenital defects Chronic pancreatitis Pancreatic tumors Inactivation of pancreatic enzymes (e.g., ZES) |
| Reduced mucosal digestion | Carbohydrate | Congenital defects Acquired lactase deficiency |
| Protein | Generalized mucosal disease (e.g., celiac disease, Crohn disease) | |
| Intraluminal consumption of nutrients | Vitamin B12 (cobalamin) | SIBO Helminthic infections (e.g., Diphyllobothrium latum infection) |
| Malabsorption | ||
| Reduced mucosal absorption | Fat Protein Carbohydrate Vitamins Minerals | Congenital transport defects Generalized mucosal diseases (e.g., celiac disease, Crohn disease) Previous intestinal resection or bypass Infections Intestinal lymphoma |
| Decreased transport from the intestine | Fat Protein | Intestinal lymphangiectasia Primary Secondary (e.g., solid tumors, Whipple disease, lymphomas) Venous stasis (e.g., from heart failure) |
| Other Mechanisms | ||
| Decreased gastric acid and/or intrinsic factor secretion | Vitamin B12 | Pernicious anemia Atrophic gastritis Previous gastric resection |
| Decreased gastric mixing and/or rapid gastric emptying | Fat Calcium Protein | Previous gastric resection Autonomic neuropathy |
| Rapid intestinal transit | Fat | Autonomic neuropathy Hyperthyroidism |
CCK, Cholecystokinin; SIBO, small intestinal bacterial overgrowth; ZES, Zollinger-Ellison syndrome.
From Feldman M et al: Sleisenger and Fordtran’s gastrointestinal and liver disease, ed 10, Philadelphia, 2016, Elsevier.
