Should I have a stool test to investigate my gastrointestinal symptoms and potential fecal impaction?

Stool Testing and Diagnostic Approach for Your Symptoms

Based on your clinical presentation—severe pain relieved by bowel movement, subsequent constipation, fibromyalgia, and prior IBS diagnosis without formal testing—you should undergo targeted laboratory screening rather than routine stool testing, unless alarm features develop. 1

Your Symptoms Do Not Currently Warrant Infectious Stool Testing

Your presentation describes constipation-related pain (relieved by defecation) followed by hard, difficult-to-pass stools—this is a mechanical/functional problem, not an infectious diarrheal illness. The 2017 Infectious Diseases Society of America guidelines are clear that stool testing for pathogens is indicated when patients have:

• Fever with diarrhea 2
• Bloody or mucoid stools 2
• Severe abdominal cramping with diarrhea 2
• Signs of sepsis 2

You have none of these features. Your symptoms reflect constipation/possible fecal impaction, not infectious diarrhea. 3, 4

The Appropriate Diagnostic Workup for Your Situation

Initial Screening Tests You Should Request

Since you have a presumptive IBS diagnosis without formal testing, the American Gastroenterological Association recommends the following screening panel: 1

• Complete blood count (CBC) to screen for anemia and inflammatory processes 1
• C-reactive protein (CRP) or ESR to assess for occult inflammation 1
• Celiac serology (anti-endomysial antibodies or anti-tissue transglutaminase IgA with total IgA) as celiac disease can mimic IBS 1
• Stool occult blood test (Hemoccult) for screening purposes 1

Additional Testing Based on Your Specific Features

• Fecal calprotectin if you are under age 45 to exclude inflammatory bowel disease 1
• Serum albumin if chronic symptoms suggest malabsorption 2
• Colonoscopy is recommended if you are over age 50 or have a family history of colorectal cancer 2, 1

Addressing the Fecal Matter on Your Prior X-ray

The spot of fecal matter seen on your previous x-ray is highly relevant to your current symptoms. Fecal impaction is a common complication of chronic constipation and can cause:

• Severe lower back and leg pain (from rectal distension and nerve compression) 3, 4
• Paradoxical diarrhea or fecal incontinence (overflow around the impaction) 5
• Relief of pain after bowel movement (as you experienced) 3

Post-treatment evaluation after fecal impaction resolves should include colonic evaluation by flexible sigmoidoscopy, colonoscopy, or barium enema to exclude underlying structural causes. 3 This was likely never done after your prior x-ray finding.

Critical Alarm Features That Would Change This Approach

You should seek immediate comprehensive evaluation if you develop: 1

• Fever or significant unintentional weight loss 1
• Rectal bleeding or black tarry stools 1
• Nocturnal symptoms that wake you from sleep 1
• Anemia on blood testing 1
• Elevated inflammatory markers (CRP, ESR, or fecal calprotectin) 1

Common Pitfalls to Avoid

Do not accept "IBS" as a diagnosis without proper exclusion of organic disease. The American Gastroenterological Association emphasizes that IBS is a diagnosis of exclusion requiring at minimum: CBC, inflammatory markers, celiac serology, and stool occult blood testing. 2, 1 Your prior diagnosis appears to have been made without this workup.

Do not ignore the constipation pattern. Severe constipation requiring manual disimpaction or causing systemic symptoms can lead to serious complications including stercoral ulcers, perforation, and peritonitis. 4, 6 Your episode of severe pain relieved by bowel movement suggests significant fecal loading.

Recommended Action Plan

1. Request the screening laboratory panel outlined above from your primary care physician 1
2. Consider imaging evaluation (abdominal x-ray or CT) if severe constipation recurs to assess for fecal impaction 3, 4
3. Undergo colonoscopy if age-appropriate (>50 years) or if screening labs are abnormal 2, 1
4. Establish a constipation prevention plan including increased dietary fiber (30 gm/day), increased water intake, and review of medications that may contribute to constipation 4