Differential Diagnosis in Primary Care, 4th Edition

Diarrhea, Chronic

The differential diagnosis of diarrhea may be approached from either an anatomic or a physiologic basis. The anatomic approach is used in Table 22. In the stomach and duodenum, pernicious anemia and Zollinger–Ellison syndrome are prominent causes. A carcinoma may form a fistula with the transverse colon and cause diarrhea. Viral gastroenteritis, and Giardia infection may also be prominent causes.

Liver and biliary tract diseases of all types may cause diarrhea (steatorrhea) by decreasing the secretion of bile. Ampullary carcinoma and cirrhosis are illustrated here, but one should not forget the diarrhea of chronic cholecystitis. The pancreas is the source of important digestive enzymes; as a result, chronic pancreatitis and pancreatic carcinomas may be associated with diarrhea (steatorrhea) in adults, whereas cystic fibrosis should be considered in children. The pancreatic islet cell tumors may secrete gastrin or vasoactive intestinal peptide, causing diarrhea.

Most of the lesions causing diarrhea are in the small intestine. Thus, cholera, Salmonella, Staphylococci, typhoid, and tuberculosis attack here. The carcinoid syndrome, various polyps (especially Peutz–Jeghers), and regional ileitis are also important causes. Toxins and drugs (see Table 22) are common causes acting here, as are pellagra and other vitamin deficiencies and food allergies. Systemic autoimmune diseases such as scleroderma and Whipple disease are also important. Mesentery artery insufficiency or obstruction should be considered both here and in the colon.

A wide variety of etiologic agents cause diarrhea by their action on the colon.

·     V—Vascular diseases include ischemic colitis.

·     I—Infectious agents such as bacillary dysentery (Shigella), Escherichia coli, Campylobacter, Yersinia, and amebiasis may ulcerate or inflame the colon.

·     N—Neoplasms such as carcinomas and polyps cause chronic irritation and exudates from the colon with hypermotility and diarrhea.

·     D—Degenerative lesions of the muscularis that cause diverticulosis and allow overgrowth of bacteria and chronic inflammation may lead to diarrhea, but this may be classified under the idiopathic category as well.

·     I—Intoxicating substances, osmotic cathartics, and antibiotics (by allowing overgrowth of bacteria and fungi) may involve the colon (e.g., pseudomembranous colitis). Mucous colitis or irritable bowel syndrome may best be classified as idiopathic.

·     C—Congenital lesions of the colon include the solitary diverticulum of the cecum, malrotation (more frequently associated with intestinal obstruction), and familial polyposis.

·     A—Autoimmune disease of the colon is common and includes both ulcerative colitis and granulomatous colitis.

·     T—Trauma is not a common cause of diarrhea anywhere in the intestinal tract, but certainly surgically induced fistulas may occur in the colon or anywhere else.

·     E—Endocrine disorders do not usually affect the colon directly.

Having considered the local causes of diarrhea, do not forget reflex diarrhea from diseases of other organs, such as pyelonephritis, salpingo-oophoritis, and central nervous system diseases.

Using Table 23, the reader can develop the differential diagnosis of diarrhea with physiology. Diarrhea may result from increased intake of fluids or bulk foods; hyposecretion of enzymes necessary for digestion of food; hypersecretion of gastrointestinal (GI) fluids and enzymes; malabsorption of various substances, particularly protein and fat; exudations of pus induced by granulomatous or ulcerative colitis and Salmonella or Shigella infections; hypermobility from stimulation by cathartics, various hormones (e.g., vasoactive intestinal peptides and gastrin), and hypomobility from autonomic dysfunction as occurs in diabetic neuropathy.

Approach to the Diagnosis

Whichever method is applied (anatomic or physiologic), most causes of diarrhea can be recalled before interviewing the patient. Then one can proceed to ask the right questions to eliminate each suspected cause. Are other members of the family affected? Is there a history of recent travel abroad? Combinations of symptoms and signs will assist greatly in narrowing the differential diagnosis. For example, chronic diarrhea and copious mucous without blood suggests irritable bowel syndrome. Chronic diarrhea with mucous and blood suggests ulcerative colitis.

 

TABLE 22. Diarrhea—Anatomic Classification

 

V

I

N

D

I

C

A

T

E

 

Vascular

Inflammatory

Neoplasm

Degenerative and Deficiency

Intoxication and Idiopathic

Congenital

Autoimmune Allergic

Trauma

Endocrine

Stomach and Duodenum

 

Viral gastroenteritis Parasite

Carcinoma with fistula into intestines

Pernicious anemia Iron deficiency

Uremia
Antacid

   

Surgery (e.g., blind loop)

Zollinger–Ellison syndrome

Liver and Biliary Tract

Chronic cholecystitis and lithiasis

Neoplasm obstructing bile ducts

Cirrhosis

Cirrhosis

Pancreas

 

Chronic pancreatitis

Pancreatic carcinoma
Islet cell adenoma

 

Radiation

Cystic fibrosis

Pancreatic cholera

Small Intestine

Mesenteric artery insufficiency

Cholera
Botulism
Staphylococcus
Salmonella
Escherichia coli
Parasites
Tuberculosis

Carcinoid
Polyp
Sarcoma
Lymphoma

Pellagra
Pyridoxine deficiency

Sprue
Cathartic
Mercurial
Reserpine
Antibiotic
Alcohol
Other drugs

Peutz–Jehgers diverticulum (Meckel)

Regional ileitis
Whipple disease
Scleroderma

Fistula

Hypoparathyroidism
Hyperthyroidism
Addison disease

Large Intestine

Mesenteric artery insufficiency

Shigella
Amebiasis
Other parasites

Polyp
Carcinoma and other neoplasms

Mucus colitis
Diverticulosis
Antibiotic
Hypervitaminosis
Uremia

Familial polyposis

Ulcerative colitis
Granulomatous colitis
Food allergy

     

Physical examination is often unrewarding but it may disclose a hepatic, rectal, or pelvic source for the diarrhea; it may also indicate that the diarrhea is a sign of a systemic disease (e.g., scleroderma or hyperthyroidism). Rectal examination may reveal a fecal impaction. A warm stool examination for pus, pH (acid stool suggests lactase deficiency), fat and meat fibers, blood, ova, and parasites is most essential. Stool for immunoassay for lactoferrin may indicate bacterial infection. A stool culture is done. Proctoscopy (immediately if there is blood) followed by colonoscopy, barium enema, and upper GI series is usually necessary in all cases.

Other Useful Tests

1. CBC (malabsorption syndrome)

2. Cathartic stool examination (intestinal parasites)

3. Small-bowel series (malabsorption syndrome)

4. Duodenal aspiration (giardiasis, Strongyloides)

5. Lactose tolerance test (lactase deficiency)

6. D-Xylose absorption test (malabsorption syndrome)

7. Serum gastrin (gastrinoma)

8. Urine 5-hydroxyindoleacetic acid (5-HIAA) (malabsorption syndrome, carcinoid tumor)

9. Mucosal biopsy (malabsorption syndrome)

10.   Colonoscopy and biopsy (ulcerative colitis, amebic colitis, granulomatous colitis)

11.   Stool for Giardia antigen (giardiasis)

12.   Human immunodeficiency virus (HIV) antibody titer (AIDS)

13.   Angiogram (ischemic colitis)

14.   Culture for Clostridium difficile (pseudomenbranous colitis)

15.   Glucose tolerance test (diabetic enteropathy)

16.   Stool for clostridium difficile toxin B.

Case Presentation #15

A 54-year-old white man complained of chronic diarrhea for the past year. He had also noted frequent indigestion and heartburn and occasional midepigastric pain.

Question #1. Utilizing the methods provided above, what is your list of possibilities at this point?

Further history reveals that he has had occasional black stools and does not abuse alcohol or drugs. His physical examination is unremarkable, but stools test positive for occult blood. Fasting failed to elliminate the diarrhea.

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Question #2. What is your diagnosis now?

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