The decision of whether to do lab tests will depend on what the -tool looks like (Is there a little blood or a lot? Is it bright red or brown? Is it occasional or persistent?) and on how your child appears.
In general, if there is blood only around the edges of the stool id an anal fissure is suspected, tests are not done. If there is only a small amount of blood mixed into the stool (sometimes along with mucus) and your child looks otherwise well, tests are generally not done.
If the blood in the stool is persistent, increasing, bright red, or associated with fever, or if your child appears ill, tests will be done. These may include stool tests, blood tests, and imaging (X ray or ultrasound).
Different stool tests yield different kinds of information. The presence of blood can be documented (called heme positive stools). Signs of irritation in the bowel include the presence of white blood cells (a sign of inflammation) or eosinophils (markers of allergy). Stool cultures will identify specific infections. Some of these tests require separate stool samples collected in specific containers. Naturally, if your child is still in diapers, the samples are easier to collect. In general, stool samples need to be fresh. This is why even when you bring a diaper to the doctor’s office, you may need to collect the stool another time.
If blood tests are done — and this is an infrequent occurrence— they generally include a complete blood count and a blood culture. Sometimes an electrolyte panel and liver function tests are run to assess whether other organs are affected. Specific problems such as celiac disease, food allergy, or inflammatory bowel disease may be identified with blood tests.
An X ray or ultrasound (or both) may be done to take a picture of the intestine. Neither of these studies is perfect, but both can show contrast between solid, liquid, and gas, creating an image of what is going on inside. An X ray is especially helpful if the doctor suspects an obstruction somewhere along the intestinal tract.
In some cases, intestinal bleeding may need to be evaluated with pictures of the inside of the intestinal walls. A gastroenterol-ogist (a doctor specializing in the intestinal tract) will take these pictures using a tiny camera. When a camera is inserted into the stomach via the mouth, the procedure is called endoscopy; when it is inserted into the large intestine via the anus, it is called colonoscopy. This technique allows for clear pictures of the bowel, but it is quite invasive and therefore is used only when necessary.