Irritable Bowel Syndrome vs Colorectal Cancer
Irritable Bowel Syndrome and Colorectal Cancer are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Irritable Bowel Syndrome vs Colorectal Cancer at a glance
- Irritable Bowel Syndrome: Disorder of gut-brain interaction with recurrent abdominal pain and altered bowel habits without structural disease.
- Colorectal Cancer: Adenocarcinoma arising from adenomatous or sessile serrated polyps; preventable with screening.
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Side-by-side comparison
| Feature | Irritable Bowel Syndrome | Colorectal Cancer |
|---|---|---|
| At a glance | Disorder of gut-brain interaction with recurrent abdominal pain and altered bowel habits without structural disease. | Adenocarcinoma arising from adenomatous or sessile serrated polyps; preventable with screening. |
| Classic presentation | Young woman with chronic abdominal pain relieved by defecation, alternating bowel habit, and bloating — exam normal.; Recurrent abdominal pain related to defecation (relief or worsening); Change in stool frequency or form; Bloating, distension; Mucus in stool; Symptoms worsened by stress and certain foods (FODMAPs); Sensation of… | Older adult with iron-deficiency anemia of unclear source (right colon), or change in bowel habit with rectal bleeding (left colon/rectum).; Right-sided (cecum/ascending): occult bleeding → iron-deficiency anemia, fatigue, weight loss; large lumen tolerates mass before obstruction; Left-sided (descending/sigmoid): change in stool… |
| Workup / key labs | Rome IV: Recurrent abdominal pain on average ≥1 day/week in the last 3 months, associated with ≥2 of: (1) related to defecation, (2) change in stool frequency, (3) change in stool form. Symptom onset ≥6 months prior to diagnosis. Subtypes by predominant stool form using Bristol Stool Scale: IBS-C, IBS-D, IBS-M, IBS-U.; CBC (exclude… | Histologic confirmation by colonoscopic biopsy. Staging by AJCC 8th edition TNM. Screening modalities (USPSTF: average-risk adults 45-75): colonoscopy every 10 yr, FIT annually, FIT-DNA (Cologuard) every 3 yr, flexible sigmoidoscopy every 5-10 yr ± FIT annually, CT colonography every 5 yr.; CBC (microcytic anemia); BMP, LFTs (liver… |
| Imaging | Colonoscopy — NOT routinely required for typical IBS without alarm features; perform if age ≥45 (CRC screening), alarm features, family history of IBD/CRC, or refractory symptoms; Random colonic biopsies if chronic watery diarrhea (microscopic colitis) | Colonoscopy with biopsy — DIAGNOSTIC; tattoo lesion for surgical localization; CT chest/abdomen/pelvis with contrast — staging (M assessment); Rectal cancer: pelvic MRI (T and N staging), endorectal ultrasound (early T staging); PET-CT not routine; selected cases for equivocal metastases; Mismatch repair (MMR) or MSI testing on all CRCs… |
| First-line treatment | Establish therapeutic relationship; educate that IBS is a real, chronic, manageable condition; Dietary modification: regular meals, adequate fiber (soluble — psyllium); trial of low-FODMAP diet under dietitian guidance; Exercise, sleep hygiene, stress management; Cognitive behavioral therapy and gut-directed hypnotherapy (strong evidence) | Multidisciplinary team approach; Stage-directed therapy (see by_subtype); Curative-intent surgery is the cornerstone for non-metastatic disease; Lifestyle and risk factor counseling |
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