In a 29‑year‑old woman with crampy abdominal pain, bloating and difficulty passing stool, no fever and a negative typhoid test, what is the most likely diagnosis and appropriate management?

Most Likely Diagnosis: Irritable Bowel Syndrome (IBS)

In a 29-year-old woman presenting with crampy abdominal pain, bloating, and difficulty passing stool without fever or evidence of infection, the most likely diagnosis is irritable bowel syndrome with constipation (IBS-C), and management should focus on making a positive clinical diagnosis without extensive investigation, followed by dietary modification and symptom-directed therapy. 1

Diagnostic Approach

Making a Positive Diagnosis

• IBS should be diagnosed based on the presence of abdominal pain associated with altered bowel habit (constipation in this case) and bloating, without requiring extensive testing in the absence of alarm features. 1

• The British Society of Gastroenterology emphasizes that restrictive diagnostic criteria like Rome IV are rarely used in primary care and may be unnecessarily limiting—a positive diagnosis based on typical symptoms is appropriate. 1

• Bloating is highly suggestive of IBS when present alongside abdominal pain and altered bowel habit, even though it is not required for Rome IV criteria. 1

Essential Baseline Investigations

Perform these tests at the initial visit to exclude organic disease:

• Full blood count, C-reactive protein (or ESR), and coeliac serology (tissue transglutaminase IgA with total IgA) 1

• Faecal calprotectin is NOT indicated in this case because the patient has constipation-predominant symptoms; this test is reserved for patients with diarrhoea and age <45 years 1

Alarm Features That Would Require Colonoscopy

This patient does not have alarm features, but you must actively exclude:

• Age >50 years (she is 29) 2
• Rectal bleeding 2
• Unintended weight loss 2
• Iron deficiency anaemia 2
• Nocturnal symptoms 2
• Family history of colorectal cancer or inflammatory bowel disease 2
• Short symptom duration (<3 months) suggesting new-onset disease 2

Since this patient has none of these features and is under 45 years with typical IBS symptoms, colonoscopy is not indicated. 3

Management Strategy

Patient Education and Reassurance

• Provide a clear explanation that IBS is a disorder of gut-brain interaction with a benign prognosis, emphasizing that symptoms can be managed but there is no cure. 1

• The British Society of Gastroenterology stresses that patients often feel their symptoms are dismissed or trivialised—acknowledge the impact on daily life and validate the diagnosis. 1

• Explain that treatments aim to improve quality of life and are likely to be necessary long-term. 1

First-Line Dietary Modifications

• Trial dietary fibre modification: For IBS-C, soluble fibre (e.g., psyllium/ispaghula husk) may improve stool consistency and ease passage, while insoluble fibre (bran) should be avoided as it can worsen bloating. 1

• Limit caffeine intake, as caffeine can worsen gastrointestinal symptoms through effects on motility. 4

• Avoid foods high in simple sugars and high-fat foods, which can exacerbate bloating and abdominal discomfort. 4

• Consider a trial of a low-FODMAP diet if bloating is particularly troublesome, ideally under dietitian supervision, as this has evidence for reducing IBS symptoms. 1

Pharmacological Management for IBS-C

• Osmotic laxatives (polyethylene glycol/macrogol) are first-line for constipation in IBS-C to improve stool frequency and consistency. 1

• Antispasmodics (e.g., hyoscine butylbromide, mebeverine, peppermint oil) can be used for abdominal cramping pain on an as-needed basis. 1

• Avoid stimulant laxatives routinely, as they may worsen cramping pain. 1

Psychological Therapies

• Consider gut-directed cognitive behavioural therapy (CBT) or hypnotherapy early rather than waiting for multiple drug failures, particularly if symptoms are significantly impacting quality of life. 3

• The British Society of Gastroenterology emphasizes that psychological factors, employment impact, and health beliefs all influence symptom management and should be addressed. 1

Follow-Up Plan

• Arrange follow-up in 4-6 weeks to assess response to initial dietary and pharmacological interventions. 1

• Reassess if symptoms worsen or new alarm features develop (rectal bleeding, weight loss, nocturnal symptoms), which would then warrant colonoscopy. 2, 3

• Avoid repeated investigations for reassurance purposes, as colonoscopy does not provide reassurance to IBS patients and diverts from effective symptom management. 3

Common Pitfalls to Avoid

• Do not delay making a positive diagnosis of IBS while pursuing extensive investigations in the absence of alarm features—this prolongs patient anxiety and delays effective management. 1

• Do not trivialise or dismiss symptoms—patients with IBS report that lack of empathy from clinicians is a major barrier to effective care. 1

• Do not use the term "functional" in a dismissive way—frame IBS as a real disorder of gut-brain interaction with validated treatment options. 1

• Do not order colonoscopy for reassurance in young patients without alarm features—the yield is extremely low and it does not improve patient outcomes. 3

Why This Is NOT Gastroenteritis

• The absence of fever, acute onset, vomiting, and watery diarrhoea makes acute gastroenteritis extremely unlikely. 4

• The negative typhoid test and chronic nature of symptoms (implied by "difficulty passing stool" rather than acute diarrhoea) further exclude infectious aetiologies. 5, 6

• Gastroenteritis typically presents with acute watery or bloody diarrhoea, not constipation and chronic bloating. 4