Final answer:
The adverse effect of lactulose, a medication used to treat hepatic encephalopathy, that is causing excessive stools in the client is excessive diarrhea.
Step-by-step explanation:
The adverse effect of lactulose, a medication used to treat hepatic encephalopathy, that is causing excessive stools in the client is excessive diarrhea. Lactulose is a type of osmotic laxative that draws water into the bowel, softening the stool and increasing the frequency of bowel movements. This side effect is expected and commonly seen with lactulose treatment.