ANOREXIA

Physiology is the most appropriate basic science to use in developing a list of the causes of anorexia. A good appetite depends on a psychic desire for food; a happy GI tract that is secreting hydrochloric acid, pancreatic and intestinal enzymes, and bile in the proper amounts; a smooth absorption of food; a smooth transport of food and oxygen to the cell; and an adequate uptake of food and oxygen by the cells. Examining each of these physiologic mechanisms provides a useful recall of the differential diagnosis of anorexia.

1. Psychic desire for food. This may be impaired in functional depression, psychosis, anorexia nervosa, and organic brain syndromes (e.g., cerebral arteriosclerosis, senile dementia, and tumors).
2. GI disease. Esophagitis, esophageal carcinoma, gastritis, gastric and duodenal ulcers, gastric carcinoma, intestinal parasites, regional enteritis, intestinal obstruction, ulcerative colitis, diverticulitis, chronic appendicitis, and colonic neoplasm are the most important diseases to consider here. Many drugs increase acid production (e.g., caffeine) and cause gastritis (e.g., aspirin, corticosteroids, and reserpine) or interfere with intestinal motility and cause anorexia.
3. Decreased pancreatic enzymes. Pancreatitis, fibrocystic disease, pancreatic carcinomas, and ampullary carcinomas are considered here.
4. Proper bile secretion. Gallstones, cholecystitis, cholangitis, liver disease, and carcinoma of the pancreas and bile ducts must be considered here.
5. Smooth absorption of food. Celiac disease and the many other causes of malabsorption are brought to mind in this category.
6. Smooth transport of food and oxygen. Anything that interferes with oxygen and, food reaching the cell may be considered, here. Pulmonary diseases that interfere with the intake of oxygen or release of CO2 are recalled here, as are anemia and CHF.
7. Uptake of food and oxygen by the cell. This will be decreased in diabetes mellitus (when there is no insulin to provide the transfer of glucose across the cell membrane); in hypothyroidism (when the cell metabolism is slow so uptake of oxygen and food is also slow) in adrenal insufficiency, where the proper relation of sodium (Na+), chloride (Cl−), and potassium (K+) is interfered with; in uremia, hepatic failure, and other toxic states from drugs that interfere with cell metabolism; and in histotoxic anoxia, where the uptake of oxygen by the cell is impaired (e.g., cyanide poisoning). Chronic infections like pulmonary tuberculosis may also produce anorexia by this mechanism.

ANOREXIA

Approach to the Diagnosis

Loss of appetite usually is related to one of four things: a psychiatric disorder, an endocrine disorder, a malignancy, or a chronic disease. If the general physical examination is normal, it is wise to get a psychiatric consult at the onset. Alternatively, one may order a psychometric test such as the MMPI (Minnesota Multiphasic Personality Inventory).

The organic causes of anorexia are usually associated with significant weight loss. The combination with anorexia of other symptoms and signs will help make the diagnosis. Anorexia with jaundice points to hepatitis or liver neoplasm as the cause. Anorexia with nonpitting edema would suggest hypothyroidism. Anorexia with dysphagia would suggest an esophageal neoplasm. Anorexia with tanning of the skin would suggest adrenal insufficiency.

The initial workup of anorexia includes a CBC; sedimentation rate; urinalysis; chemistry panel; stool for occult blood, ovum, and parasites; chest x-ray; and flat plate of the abdomen. If hypothyroidism is suspected, a free thyroxine index (FT4) and thyroid-stimulating hormone–sensitive assay (S-TSH) text is ordered. If liver disease is suspected, a liver profile or hepatitis profile may be ordered. If malabsorption syndrome is suspected, one can order a d-xylose absorption test or quantitative stool fat analysis. If CHF is suspected, a circulation time is a good screening test. If pancreatic carcinoma or other GI malignancy is suspected, a CT scan of the abdomen may be ordered. It is best to consult a gastroenterologist before ordering these expensive tests. He or she can decide if endoscopic procedures or other studies would be more useful before ordering a CT scan.

Other Useful Tests

1. Fever chart (chronic infectious disease)
2. Serum amylase and lipase (pancreatic carcinoma)
3. Carcinoembryonic antigen (CEA) (GI neoplasm)
4. Schilling test (pernicious anemia)
5. Barium enema (colon neoplasm)
6. Upper GI series and esophagram (GI malignancy, cardiospasm)
7. Small-bowel series (regional enteritis, neoplasm)
8. Sonogram (hepatic cyst, pancreatic cyst)
9. Esophagoscopy (carcinoma)
10. Gastroscopy (gastric ulcer or malignancy)
11. Colonoscopy (colonic neoplasm)
12. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) assays (anorexia nervosa, hypopituitarism)

Book Source Details

• Book Title: Differential Diagnosis in Primary Care
• Author(s): R. Douglas Collins
• Year of Publication: 2007
• Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.

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