Diarrhea is defined as an increase in the frequency and fluidity of stools. For most patients, diarrhea means the passage of loose stools. Although loose stools are often accompanied by an increase in the frequency of bowel movements, most patients do not classify frequent passage of formed stools as diarrhea. Because stool consistency is difficult to quantitate, many investigators use frequency of defecation as a quantitative criterion for diarrhea. By this standard, passage of more than two “loose” bowel movements per day is considered abnormal.
Some authors also incorporate stool weight in the definition of diarrhea. Normal stool weight averages approximately 80 g/day in women and 100 g/day in men. The upper limit of normal stool weight (calculated as the mean plus two standard deviations) is approximately 200 g/day. Normal stool weight depends on dietary intake, and some patients on high-fiber diets exceed 200 g/day without reporting that they are having diarrhea. Thus stool weight by itself is an imperfect criterion for diarrhea.
Criteria for Diagnosis of Diarrhea
|Criterion||Normal Range||Diarrhea, if:|
|Increased stool frequency||3 to 14 stools per week||> 2 stools per day|
|More liquid stool consistency||Soft—formed stools||Loose—unformed|
|Increased stool weight|
0 to 240 g/24 h
0 to 180 g/24 h
> 240 g/24 h
> 180 g/24 h
What other disorder may be described as diarrhea?
Occasionally patients with fecal incontinence describe that problem as diarrhea, even when stools are formed. Physicians must be careful to distinguish fecal incontinence from diarrhea, because incontinence is usually due to problems with the muscles and nerves regulating continence and not just to passage of unusually voluminous or liquid stools.