Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
Most episodes of diarrhea are mild and of short duration and do not need to be brought to the attention of a doctor. The doctor should be consulted when there is:
High fever (temperature greater than 101 F or 38.3 C
Moderate or severe abdominal pain or tenderness
Bloody diarrhea that suggests severe intestinal inflammation
Diarrhea in persons with serious underlying illness for whom dehydration may have more serious consequences, for example, persons with diabetes, heart disease, and AIDS
Severe diarrhea that shows no improvement after 48 hours.
Moderate or severe dehydration
Prolonged vomiting that prevents intake of fluids orally
Acute diarrhea in pregnant women because of concern for the health of the fetus
Diarrhea that occurs during or immediately after completing a course of antibiotics because the diarrhea may represent antibiotic-associated infection with C. difficile that requires treatment
Diarrhea after returning from developing countries or from camping in the mountains because there may be infection with Giardia (for which there is treatment)
Diarrhea that develops in patients with chronic intestinal diseases such as colitis, or Crohn's disease because the diarrhea may represent worsening of the underlying disease or a complication of the disease, both requiring treatment
Acute diarrhea in an infant or young child in order to ensure the appropriate use of oral liquids (type, amount, and rate), to prevent or treat dehydration, and to prevent complications of inappropriate use of liquids such as seizures and abnormal blood electrolytes
How is the cause of diarrhea diagnosed?
Acute diarrhea: Acute diarrhea usually requires few tests.
Measurement of blood pressure in the upright and supine (lying) positions can demonstrate orthostatic hypotension and confirm the presence of dehydration. If moderate or severe dehydration or electrolyte deficiencies are likely, blood electrolytes can be measured.
Examination of a small amount of stool under the microscope may reveal white blood cells indicating that intestinal inflammation is present and prompting further testing, particularly bacterial cultures of stool and examination of stool for parasites.
If antibiotics have been taken within the previous two weeks, stool should be tested for the toxin of C. difficile.
Testing stool or blood for viruses is performed only rarely, since there is no specific treatment for the viruses that cause gastroenteritis.
If there has been recent travel to undeveloped countries or the mountains, stool may be examined under the microscope for Giardia and other parasites.
There are also immunologic tests that can be done on samples of stool to diagnose infection with Giardia.
Chronic diarrhea: With chronic diarrhea, the focus usually shifts from dehydration and infection (with the exception of Giardia, which occasionally causes chronic infections) to the diagnosis of non-infectious causes of diarrhea. (See the prior discussion of common causes of chronic diarrhea.)
This may require X-rays of the intestines (upper gastrointestinal series or barium enema), or endoscopy (esophagogastroduodenoscopy or EGD, or colonoscopy) with biopsies. Examination of the small intestine via a camera-containing capsule or specialized endoscopy also can be done.
Fat malabsorption can be diagnosed by measuring the fat in a 72 hour collection of stool.
Sugar malabsorption can be diagnosed by eliminating the offending sugar from the diet or by performing a hydrogen breath test. Hydrogen breath testing also can be used to diagnose bacterial overgrowth of the small intestine.
An under-active pituitary or adrenal gland and an overactive thyroid gland can be diagnosed by measuring blood levels of cortisol and thyroid hormone, respectively.
Celiac disease can be diagnosed with blood tests and a biopsy of the small intestine.