Diarrhea is one of the most common abnormal manifestations of gastrointestinal (GI) dysfunction in the intensive care unit (ICU); the reported incidence is between 2% and 63%.1 Diarrhea is best defined as bowel movements that, owing to increased frequency, abnormal consistency, or increased volume, cause discomfort to the patient or the caregiver. This definition demonstrates the subjectivity in diagnosing diarrhea, a fact that complicates interpretation of the literature and limits applicability of guidelines. The impact of diarrhea on patient care in the ICU, including its cost in morbidity and mortality, is unknown. However, it is undeniable that diarrhea remains a persistent problem in many ICUs.
To date, clinicians are lacking a consistent scale or index that allows a reliable and practical way of measuring stool volume, consistency, and frequency. In its absence, the bedside nurse remains the most reliable person to diagnose the presence of diarrhea.
Bowel movements with normal physiologic volume, consistency, and frequency are the result of a GI tract that integrates motility, secretion, and absorption of fluids and adapts to the quality of the food bolus given. The result is a fecal bolus that is produced once or twice every 24 hours and has consistency and fluidity within the boundaries of normal.
Diarrhea results when there is a disorder of GI physiology or when GI tract function is incapable of handling the food bolus. There are several classifications of diarrhea, suggesting that no classification is ideal at helping the clinician plan for patient care. Perhaps the most useful approach is to classify diarrhea according to alterations of physiologic events: