Doctor's Review: Medicine on the Move

October 21, 2021


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Case study: IBS-C

A confident diagnosis and an integrated approach ensure long-term success

Brent, a 44-year-old small-business owner, visits his family physician because his business is suffering a downturn and it's causing him to be “stressed out.” His symptoms include muscle and joint aches, insomnia, palpitations, and sweating, as well as constipation with bloating and gas. Brent's family and friends constantly tell him he has to learn to relax and that things will get better. The family physician prescribes lorazepam (2 mg qhs, 4 weeks) to help him sleep.

At follow up one month later, Brent reports his sleep has improved, but he's still suffering from other symptoms. His major concern is the ongoing gastrointestinal (GI) symptoms: bloating, gas, abdominal pain, and decreased bowel frequency, from “once daily like clockwork,” to once every four days. He’s had bouts of these problems since his teens, but never told a doctor before, due to embarrassment.

Over the years, Brent tried numerous home treatments without success. First, he raised his fibre intake through both diet and psyllium powder, which increased his bowel movements slightly but made his bloating, gas and pain worse. He tried over-the-counter polyethylene glycol, but found it worked too well—after his second dose, he woke up at 4 a.m. with soiled pyjamas. He self-medicated with bisacodyl which relieved his constipation, but caused cramping severe enough that his wife made him go to the emergency room thinking he might have a bowel obstruction.

Frustrated, Brent recently consulted a naturopath for colonic irrigation, after hearing a relative’s glowing testimonial. The naturopath, however, suggested he get a colonoscopy first, to rule out colon cancer, which Brent is also worried about.

Making a firm diagnosis

Guidelines insist that IBS-C can be confidently diagnosed solely by the presence of symptoms meeting diagnostic criteria (Table 1) and absence of alarm features (Table 2), based on the history and physical.1 The history should also include questions about foods that seem to trigger IBS symptoms. Studies have shown a higher prevalence of celiac disease and lactose intolerance in IBS vs healthy patients.1 Small carbohydrates known as FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols), found in wheat and dairy foods, and many fruits, vegetables and legumes, may cause bloating and gas due to osmotic effects and fermentation in the bowel.2 Finally, assessing the patient’s emotional state is important, since anxiety and depression are common comorbidities, and stress is a known trigger of IBS symptoms.3

Routine diagnostic testing isn’t recommended—the yield is generally low and similar to that in healthy patients. Like Brent, many IBS patients are concerned about colon cancer, yet, in some studies, the prevalence of bowel malignancy is lower in IBS than in age-matched controls, probably because such patients are health-conscious and follow screening guidelines. Alarm features do require appropriate investigations to rule out organic causes, but even then, positive findings are unlikely.1

That said, selected diagnostic tests can be useful in in IBS-C without alarm features (Table 3). Their main value lies in boosting your confidence in the diagnosis of IBS-C.2 I see nothing wrong in doing tests to convince patients no sinister disease has been overlooked, since their buy-in to the diagnosis of IBS is so important for successful therapy.

No need for alarm

Brent’s recurrent GI symptoms, especially abdominal pain and constipation, are consistent with IBS-C. His family physician confirms the diagnosis using the Rome III symptom criteria, and rules out organic disease based on Brent’s lack of alarm features, and normal/negative results on the above diagnostic tests. Brent also reports that onions and legumes cause severe bloating, gas and abdominal pain, suggesting FODMAP sensitivity.

Weighing the treatment options

The overall goal of treatment in IBS is to help patients feel qualitatively better, with no specific targets. Patients need to know that, although IBS is usually a chronic, lifelong condition, their best chance of long-term benefits is to work with their physicians to implement a combination of lifestyle, diet, behavioural and/or medical interventions.2

Exercise increases colon transit speed and stool frequency, and a randomized controlled trial of an exercise program showed benefits over usual care in improving overall IBS symptoms.2 Fibre, particularly psyllium, can provide overall symptom relief, but may worsen bloating and abdominal discomfort, and adherence may be difficult. Low-FODMAP diets are promising, but more research is needed to define their role. Referral to a dietitian is recommended. Psychological therapies, including cognitive behavioural therapy, hypnosis and dynamic psychotherapy, can effectively improve IBS symptoms, but evidence quality is low.3

We know laxatives can improve constipation, but few studies have looked at their effects in IBS-C. In reviewing trials of polyethylene glycol in IBS-C, the ACG concluded that it doesn’t improve overall symptoms or pain. Tricyclic antidepressants and selective serotonin reuptake inhibitors effectively relieve global symptoms and abdominal pain in IBS-C, but side effects and patients’ reluctance to take psychotropics may limit their use.3

Linaclotide is a prosecretory agent with visceral analgesic effects. High-quality trials show that is an effective option for IBS-C, improving both abdominal symptoms (pain, discomfort, cramping, bloating) and bowel habits (frequency, consistency, straining). Stool frequency typically increases within the first week, while abdominal symptoms may take several weeks to improve. The main side effect of linaclotide is diarrhea, which tends to occur in the first few days, if at all. Patients who get diarrhea should decide with their physician whether to stop the drug.2,3

Many happy endings

Relieved to hear that he doesn’t have a serious illness, Brent resolves to take charge of his health. He sees a dietitian to try a low-FODMAP diet, based on his sensitivity to onions and legumes, and agrees to take linaclotide, which reduces his abdominal pain and constipation dramatically. Within a few months, his IBS has improved overall, and his bowel symptoms have stabilized, but not resolved completely. However, his muscle aches are now more bothersome than ever. The family doctor realizes that Brent probably has an underlying generalized anxiety disorder, and recommends cognitive behavioural therapy.

Table 1: Diagnostic criteria for irritable bowel syndrome (IBS)3

Rome III
- Recurrent abdominal pain or discomfort ≥3 days/month in past 3 months
- Symptom onset ≥6 months before diagnosis
- Associated with ≥2 of the following:
- Improvement after defecation
- Change in stool frequency
- Change in stool form/appearance
- Subtyped according to predominant bowel habit:
- Constipation (IBS-C)
- Diarrhea (IBS-D)
- Mixed (IBS-M)
- Unclassified (IBS-U)

American College of Gastroenterology
- Abdominal discomfort associated with altered bowel habits ≥3 months

Table 2: Alarm features1

- onset after age 50
- blood in stools
- severe or progressively worsening symptoms
- weight loss
- iron-deficiency anemia
- nocturnal symptoms
- family history of colorectal cancer, inflammatory bowel disease or celiac disease

Table 3: Selected diagnostic tests in IBS-C

- Celiac disease screening, lactose intolerance testing (higher prevalence of these conditions in IBS)
- Complete blood count (anemia)
- Colonoscopy (colon cancer)
- Blood glucose (diabetes)
- Serum calcium (hypercalcemia)
- Thyroid function (hypothyroidism)
- Abdominal ultrasound (bloating due to ascites)

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