When does laxative use cross the line to abuse?

Laxative abusers: Two patient groups (both will deny laxative ingestion): bulemia nervosa (typically women 18-40), & surreptitious laxative abusers (usually women 40-60). "irritant" purgatives cause: melanosis coli (reversible pigmenting of colon lining), cathartic colon ("floppy" colon with limited muscle tone), & soap or chemical colitis (acute inflammation within hours of "cleansing" enema). Suspects need eval.