Ask the Doctors: SIBO similar to IBS, but in small intestine

Dear Doctors: I've been seeing a lot of news stories lately about people who thought they had irritable bowel syndrome, but then it turned out to be something called "SIBO." I've never heard of that before. Can you please explain what it is? How do you know if you have it? Can it be cured?

Dear Reader:

You're asking about a condition called small intestinal bacterial overgrowth, often shortened to SIBO. It's similar to irritable bowel syndrome, or IBS, in that it is also related to the gut. However, IBS affects the large intestine and, as the name of the condition states, SIBO involves the small intestine.

Both IBS and SIBO share many of the same symptoms. These include loss of appetite, abdominal pain or cramping, abdominal bloating, nausea, an overproduction of gas and alternating bouts of constipation and diarrhea. People with SIBO may also have vitamin deficiencies, despite eating a balanced diet. A deficit of vitamin B12 is common. Both SIBO and IBS can range from mild, with minimal symptoms, to severe enough to interfere with activities of daily life.

SIBO occurs when the optimal balance of bacteria in the small intestine is disturbed. That's the "overgrowth" in the name of the condition. This includes an abnormal increase in the numbers of bacteria living in the small intestine and the presence of specific types of bacteria that don't normally live in that portion of the bowel. As this altered population of bacteria goes to work fermenting the food that leaves the stomach and enters the small intestine, it causes the unpleasant and often painful symptoms we discussed earlier.

It's not yet clear what triggers SIBO. Structural issues may allow bacteria from the large bowel to mistakenly migrate across the muscular valve that separates it from the small bowel. Something known as low motility is also believed to be a contributing factor. That's a slower-than-normal rate at which food moves through the gastrointestinal tract. Certain medical conditions — including Crohn's disease, Parkinson's disease and diabetes — can contribute to low motility. Low levels of stomach acid can play a role in allowing bacteria to proliferate. Some cases of SIBO have been linked to gastric surgery for weight loss.

Diagnosis begins with a medical history and detailed information about the person's symptoms. When SIBO is suspected, a test to measure the concentrations of methane and hydrogen in the breath is the next step. A more definitive, but also more invasive, test involves retrieving a tissue sample for later examination from the small intestine during an endoscopy.

SIBO has a wide range of potential causes, so treatment can be a challenge. It typically begins with the use of certain types of antibiotics to control the overgrowth of bacteria. Patients may also be asked to interrupt treatment that includes antacids, and to use medications to improve motility.

A promising area of research into both SIBO and IBS is the use of fecal transplants. However, this remains in the experimental stage. At this time, the use of fecal transplants is not approved by the Food and Drug Administration for the treatment of SIBO.

Dear Doctors:

Can you please talk about rat bite fever? Our son got bitten by a baby rat while he was cleaning out his garage, and he didn't see a doctor. It turned out that he was OK, but I'm worried about what could have happened. What should he have done?

Dear Reader:

Close contact with wild rodents or the places where they live poses a health risk. Mice and rats can be infected with a range of bacteria and viruses, and they can transmit disease through their feces, urine and saliva. Among these many illnesses is the one you're asking about — rat bite fever.

Rat bite fever is caused by two different bacteria. In the United States, the bacterium is called Streptobacillus moniliformis. In Asia, the disease is caused by a bacterium known as Spirillum minus. People can become infected if they are scratched or bitten by a rat. The bacteria can also be transmitted through food or water contaminated with the waste products of infected rodents. This causes a closely related illness known as Haverhill fever. In either case, the resulting illness can be serious, or even fatal, if it goes untreated. Symptoms can begin as soon as three days after coming into contact with the bacteria. However, in some cases it can take up to three weeks for symptoms to manifest.

As the name of the disease suggests, it often begins with a fever. Additional symptoms include headache, muscle pain, nausea and vomiting. It's common for the fever to be followed in a few days by a rash on the hands or feet. About half of infected individuals also develop pain and swelling in one or more joints. Haverhill fever follows a similar pattern, but it often includes sore throat and swollen lymph nodes, as well as vomiting that is more severe.

When rodent contact and subsequent symptoms point to rat bite fever, the diagnosis is confirmed via a culture of a sample of blood or joint fluid. While immediate treatment with antibiotics is highly successful in curing the disease, it's possible to experience lingering fatigue and joint pain.

It's when rat bite fever goes untreated that serious complications can occur. These include abscesses, which are pockets of infected fluid, often in the abdomen, and infections of the major organs, including the heart, liver, lungs and brain. About 10 percent of untreated cases result in death.

Any kind of bite from a rodent, whether wild or domesticated, must be taken seriously. As soon as possible, you should gently but thoroughly wash the area with soap and warm water. It's also important to seek medical care. Rodent bites are puncture wounds and can easily become infected. You may be advised to get a tetanus shot, or possibly undergo a precautionary course of antibiotics. Keep an eye out for the symptoms we already discussed, as well as general signs of infection. This includes fever, redness or swelling at the site of the injury, pus formation and skin that's warm to the touch. If any of these develop, seek immediate medical care.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health.