Diarrhea, Chronic - Approach

Chronic diarrhea is usually > 4 weeks and is often non-infectious (not in our case). Before you launch into a list of various causes first consider the following:
a) exclude iatrogenic problem: medications or surgery
b) Then check for
-blood per rectum: (directs you to do a colo + bx)
-features of malabsorption: ( think eval of SB: imaging, biopsy, aspirate)
-pain aggravated before BM, relieved with BM, sense of incomplete evacuation: suspect IBS: (do just a limited screen for organic dz.)
-no blood, features of malabsorption: consider functional diarrhea--> dietary exclusion: lactose, sorbitol

Focused Physical Exam:
a) clues of malabsorption or IBD, e.g. anemia, dermatitis herpetiformis, edema or clubbing, flushing, EN, oral ulcers
b) features of autonomic neuropathy or collagen-vascular disease in pupils, orthostasis, skin, hands or joints?
c) abdominal mass or ttp
d) abnormalities of rectal mucosa, rectal defects, or altered anal sphincter functions? (if you don't look you will never know)

Classes of chronic diarrhea by mechanism:
1. secretory: watery, large volume, persist with fasting, typically painless
--> VIPomas, chronic ETOH, bowel resecction, addison, cholera

2. inflammatory: fever, pain , bleeding
--> IBD, lymphocytic and collagenous colitis, eosinophilic GE, xrt, GI Cancer, infection (invasive bac, virus, parasites)

3. osmotic: ceases when you fast or stop agent
--> osmotic laxative, lactase, nonabsorble carbs

4. steatorrheal: greasy, foul-smelling stools. >7g/day of fat
--> mucosal malabsorption (celiac sprue, whipple's, ischemia), intraluminal maldigestion (pancreatic exocrine insufficiency, bacterial overgrowth, bariatric surgery)

5. dysmotile
--> IBS, hyperthyroid, prokinetic drugs, post-vagotomy, visceral neuromyopathies

6. factitial
--> eating d/o, Munchausen

7. iatrogenic
--> bariatric surgery, ileal resection, cholecystectomy, vagotomy, fundoplication

Irritable bowel syndrome is very common.
To diagnose recurrent abdominal pain and discomfort must be present for >=3 days/month x 3 months + 2 out of 3 of the following regarding the pain: (ROME criteria)
- better with BM
- onset occurs with change of frequency of stool
- onset with change in form of stool

Supportive findings for IBS are:
- altered stool passage
- mucuorrhea
- sense of incomplete evacuation

Amoebic Colitis, from E. Histolytica is best tested for on stool looking for EIA detection. Once the serum Ab is positive it remains positive despite treatment- so that isn't helpful in our patient to look for recurrence. There may be +/- fecal leuks and + FOBT. On pathology there are focal ulcerations of the colon and mucosal thickening with flask-shaped ulcers and PAS+ staining.

Pearls:
O&P can be negative in patients with just amoebic liver abscess.
Your LFTS may be normal except for slightly elevated alk phosphatase.

Amebiasis is treated with metronidazole or tinidazole, followed by a luminal agent to prevent relapse, such as paramycin or diloxanide.

(Katharine Cheung MD, 10/2/10)