Referral of the month - abdominal symptoms
Consultant gastroenterologist Dr Penny Nield responds to this case of a 61-year-old woman with suspected post-infective IBS
Dear Dr Nield
I’d appreciate your opinion regarding this normally very fit 61-year-old lady.
She returned from holiday in Cuba about a year ago, where she suffered what sounds like a bout of traveller’s diarrhoea.
Since that time, she has suffered persistent gastrointestinal symptoms – bloating, nausea, some colicky abdominal pains usually relieved by defaecation and a change in her bowel habit with alternating constipation and diarrhoea. There has been no associated rectal bleeding or weight loss.
She notices that certain foods and stress aggravate her symptoms and she also describes her stools as difficult to flush at times. Bloods, including coeliac screen, were normal and so too were stool tests for microscopy, culture and sensitivity, ova, cysts and parasites, and faecal calprotectin.
She has no relevant past medical history and is on no medication.
There are a number of possible issues here which I’d appreciate your advice on:
- The story sounds very much like post-infective irritable bowel syndrome. Would it be reasonable to treat it as such even though, technically, she fulfils NICE guidance for two week referral to exclude colonic cancer? NICE makes no comment on duration of symptoms but presumably if they are quite longstanding and the patient is otherwise well, cancer is unlikely?
- I did wonder whether she might have picked up giardiasis. How reliable is the stool test in excluding this? Could she still be getting symptoms from giardia at this point? Is there a role for an empirical trial of metronidazole?
- If malabsorption is a possibility, how should this be investigated?
Many thanks for your extremely comprehensive and helpful letter regarding this lady and for your summary of her investigations and results.
As you say, the symptoms that you describe are certainly very typical of post-infective irritable bowel syndrome (IBS), which is common and may affect anywhere from 4-32% of people after a significant episode of infective gastroenteritis. The longevity of symptoms can be extremely variable, but tends to be influenced by the severity of the initial illness, as well as the pathogen (longer when bacteria and protozoa compared to viruses) and presence of any pre-existing psychiatric comorbidity. Although most people tend to recover from episodes of infective gastroenteritis within days or weeks, it is well documented that a significant cohort may continue to experience IBS-type symptoms for a number of years and sometimes indefinitely. Such symptoms may be exacerbated by certain foods (acquired lactose intolerance may occur in up to 40% of patients, with variable persistence) and stress, as well as a likely perturbation in the gut microbiota.
Obviously it is important, particularly in a woman of this lady’s age, and who was previously well, to consider other possible diagnoses. However, given the duration of her symptoms, as well as the absence of red flag symptoms or abnormalities in her blood and stool tests, it is relatively unlikely that there is a sinister underlying cause. I assume she has not had significant nocturnal symptoms that may lead one to look for alternative causes? It may be prudent to organise a faecal occult blood specimen for further reassurance, as suggested in the NICE guidance, and to maintain a high level of clinical suspicion, but at this stage I would not consider it necessary to refer her under the two week rule to exclude colon cancer.
The risk of long-term persistence of IBS symptoms is generally lower in those who report an episode of preceding gastroenteritis, although there are a number of studies reporting significant intermittent symptoms over a number of years, even when there is a clear history of initial infection. It is often useful to explain to patients that the recovery process after gastroenteritis is often erratic, with good and bad days, the former of which gradually increase over time.
In relation to your second question, Giardia lamblia is the most common food and water-transmitted protozoan intestinal pathogen contracted by international travelers, as well as in the UK. Although the majority of people clear the infection, either with no symptoms or after a self-limited illness, a proportion will have ongoing gastrointestinal manifestations, some of which (e.g. persisting anorexia and weight loss) may be associated with chronic infection. Stool microscopy to diagnose Giardia can be variable in its detection, due to the intermittent excretion of Giardia cysts; so Giardia may be detected in only 50-70% of cases where a single specimen is provided, but in 90%, where there are three separate specimens to analyse. Alternative methods of diagnosis include stool antigen detection assays, which are more sensitive than microscopy but variable in availability and accuracy. It is also possible to diagnose Giardia by means of gastroscopy and distal duodenal biopsies, as the cysts and trophozoites may adhere to the small intestinal brush border, even when not detectable in the stool.
Given that your patient does not have ongoing symptoms of weight loss, anorexia or abnormal blood test results, it is relatively unlikely that she has persisting infection with Giardia. However, given her ongoing symptoms, it would be reasonable to administer an empirical course of treatment for Giardia - a single 2g dose of tinidazole is usually well tolerated and is as effective as a five day course of metronidazole.
Malabsorption may be associated with a number of gastrointestinal infections, with manifestations ranging from a transient lactose intolerance, resulting from disruption of the tips of villi and brush border enzyme activity (common after viral gastroenteritis), to malabsorption of fats, sugars, carbohydrates and vitamins seen in infections such as giardia and tropical sprue, as a consequence of the subtotal villous atrophy seen in these conditions. Symptoms may be non-specific, including abdominal bloating, borborygmi and mild nausea, but malabsorption should always be considered where there is ongoing weight loss, regardless of whether there is any change in bowel habit.
Lactose malabsorption can be diagnosed using hydrogen/methane breath tests, but in practice can often be managed by a trial of reduction in dairy intake and assessment of improvement of symptoms.
There is no single test to confirm global malabsorption, but it is often associated with hypoalbuminemia and deficiencies of iron, vitamin A, B12, and folate, which should be tested for as a preliminary screen. If there is clinical or biochemical suspicion of malabsorption and no improvement in symptoms after empirical treatment with tinidazole or metronidazole, patients should be referred in to the gastroenterology service for further investigations.
In summary, it sounds very much like your patient is suffering from post-infective IBS, which may gradually resolve over the next few months or years. However, given her age, it is important to consider other diagnoses if there is any clinical concern or red flag features.
I would suggest the following:
- Faecal occult blood testing
- Further stool testing to exclude persisting Giardia, or an empirical treatment with tinidazole or metronidazole
- Time-limited trial of reduction of dairy products in her diet
If you have any concerns regarding her ongoing symptoms, please do get in touch, or I would be delighted to see her in my clinic.
Dr Penny Neild
Dr Penny Nield is a consultant gastroenterologist at St. George’s University Hospitals NHS Trust