Stool pH is diet dependent and is based on bacterial fermentation in the small intestine. Carbohydrate fermentation changes the pH to acid; protein breakdown changes the pH to alkaline.
Stool pH testing is done to evaluate carbohydrate and fat malabsorption and assess disaccharidase deficiency. Breast-fed infants have slightly acid stool; bottle-fed infants have slightly alkaline stools.
Neutral to slightly acid or alkaline: pH 7.0–7.5 depending on diet
Newborns (0–28 days): pH 5.0–7.0 (With bottle-fed newborns and infants, the pH will be slightly alkaline [≥7.0], whereas in breast-fed newborns, the pH will be slightly acidic [≤7.0].)
Collect a random, fresh stool specimen following the procedure for Collection and Transport of Random Specimens. Observe standard precautions.
Refrigerate specimen.
Increased pH (alkaline)
Secretory diarrhea without food intake
Colitis
Villous adenoma
Antibiotic use (impaired colonic fermentation)
Decreased pH (acid)
Carbohydrate malabsorption
Fat malabsorption
Disaccharidase deficiency (intestinal)
Pretest Patient Care
Explain purpose of test, procedure for stool collection, and interfering factors.
Advise the patient to avoid barium procedures and laxatives for 1 week before stool specimen collection.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. If abnormal pH is found, assess dietary patterns and antibiotic use. Counsel the patient regarding abnormal findings; explain the need for possible further testing.
Monitor as appropriate for malabsorption syndrome.
Order a stool reducing substance test if disaccharidase deficiency is suspected (see Stool Reducing Substances Test).
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.