Irritable bowel syndrome differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

[Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as [differential dx1], [differential dx2], and [differential dx3].

OR

[Disease name] must be differentiated from [[differential dx1], [differential dx2], and [differential dx3].

Differentiating X from other Diseases

• [Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as [differential dx1], [differential dx2], and [differential dx3].
• [Disease name] must be differentiated from [[differential dx1], [differential dx2], and [differential dx3].

• As [disease name] manifests in a variety of clinical forms, differentiation must be established in accordance with the particular subtype. [Subtype name 1] must be differentiated from other diseases that cause [clinical feature 1], such as [differential dx1] and [differential dx2]. In contrast, [subtype name 2] must be differentiated from other diseases that cause [clinical feature 2], such as [differential dx3] and [differential dx4].

Differentiating Irritable Bowel Syndrome from other Diseases

American Gastroenterological Association Guidelines for Diagnosis of IBS

The American Gastroenterological Association has published a set of guidelines for tests which physicians should perform prior to diagnosing irritable bowel syndrome. The following tests are meant to exclude other causes, such as infection and colon cancer.

1. History and physical examination
2. Diagnostic testing
   1. CBC
   2. Chemistry panel
   3. Sedimentation rate
   4. Stool for O & P
   5. Stool for occult blood
   6. Flexible sigmoidoscopy
   7. IF > 50, colonoscopy or barium enema and sigmoidoscopy
   8. For diarrhea predominant:
      1. Small bowel radiograph
      2. Lactose/dextrose H2 breathing test
   9. For constipation predominant:
      1. Fiber trial
   10. For pain predominant:
       1. Plain film of abdomen

Diseases with similar symptoms

• Celiac disease
• Diverticulitis
• Endometriosis
• Gallstones
• Gastroesophageal reflux disease (GERD)
• Inflammatory bowel disease
• Lactose intolerance
• Thyroid disease

The table below summarizes the findings that differentiate watery causes of chronic diarrhea

Cause			Osmotic gap		History	Physical exam	Gold standard	Treatment
			< 50 mOsm per kg	> 50 mOsm per kg*
Watery	Secretory	Crohns	+	-	Abdominal pain followed by diarrhea	Abdominal tenderness when palpated in severe disease Blood seen on rectal exam Fever Tachycardia Hypotension	Colonoscopy with biopsy	Topical mucosamine and corticosteroids are preferred Mesalamine and sulfasalazine are used for remission
		Hyperthyroidism	+	-	Excessive sweating Heat intolerance Increased bowel movements	Lump in the neck Proptosis Tremors Increased DTR	TSH with T3 and T4	Carbimazole and methimazole Beta blockers like propylthiouracil Iodine-131
		VIPoma	+	-	Watery diarrhea Dehydration (thirst, dry skin, dry mouth, tiredness, headaches, and dizziness) Lethargy, muscle weakness Nausea, vomiting Crampy abdominal pain Weight loss Flushing	Tachycardia Rash Facial flushing Abdominal distention Abdominal tenderness in the right upper abdominal quadrant	Elevated VIP levels Followed by imaging	Sandostatin or chemotherapy for malignant tumors Surgical removal of the tumor
	Osmotic	Lactose intolerance	-	+	Abdominal pain Bloating Diarrhea Flatulence	Abdominal tenderness	Intestinal biopsy	Avoidance of dietary lactose Substitution to maintain nutrient intake Regulation of calcium intake Use of enzyme lactase
		Celiac disease	-	+	May be asymptomatic Vague abdominal pain Diarrhea Weight loss Malabsorption / steatorrhea Bloatedness	Abdominal pain and cramping Abdominal distention Tetany Mouth ulcers Dermatitis herpetiformis Signs of the fat-soluble vitamins A, D, E, and K deficiency	IgA tissue transglutaminase Ab	Gluten-free diet
	Functional	Irritable bowel syndrome	-	-	Abdominal pain or discomfort recurring at least 3 days per month in the past 3 months and associated with 2 or more of the following: Improves with defecation Onset associated with change in frequency of stool Onset associated with change in appearance of stool 25% of bowel movements are loose stools History of straining is also common	Abdominal tenderness Hard stool in the rectal vault	Clinical diagnosis ROME III criteria Pharmacologic studies based criteria	High dietary fiber Osmotic laxatives such as polyethylene glycol, sorbitol, and lactulose Antispasmodic drugs (e.g. anticholinergics such as hyoscyamine or dicyclomine)

Irritable bowel syndrome must be differentiated from diseases that cause abdominal pain and chronic diarrhea. The table below summarizes the findings that differentiate watery causes of chronic diarrhea:

Cause	Osmotic gap		History	Physical exam	Gold standard for diagnosis
	< 50 mOsm per kg	> 50 mOsm per kg*
Zollinger-Ellison syndrome	+	-	Abdominal pain and diarrhea Dyspepsia Upper or Lower gastrointestinal bleeding	Abdominal tenderness Hematochezia Hematemesis Tachycardia Hypotension	Gastrin levels
Crohn's disease	+	-	Abdominal pain followed by diarrhea	Abdominal tenderness when palpated in severe disease Blood seen on rectal exam Fever Tachycardia Hypotension	Colonoscopy with biopsy
Hyperthyroidism	+	-	Excessive sweating Heat intolerance Increased bowel movements	Lump in the neck Proptosis Tremors Increased DTR	TSH with T3 and T4
VIPoma	+	-	Watery diarrhea Dehydration (thirst, dry skin, dry mouth, tiredness, headaches, and dizziness) Lethargy, muscle weakness Nausea, vomiting Cramping abdominal pain Weight loss Flushing	Tachycardia Rash Facial flushing Abdominal distention Abdominal tenderness in the right upper abdominal quadrant	Elevated VIP levels Followed by imaging
Lactose intolerance	-	+	Abdominal pain Bloating Diarrhea Flatulence	Abdominal tenderness	Intestinal biopsy
Celiac disease	-	+	May be asymptomatic Vague abdominal pain Diarrhea Weight loss Malabsorption/steatorrhea Bloatedness	Abdominal pain and cramping Abdominal distention Tetany Mouth ulcers Dermatitis herpetiformis Signs of the fat-soluble vitamins A, D, E, and K deficiency	IgA tissue transglutaminase Ab
Irritable bowel syndrome	-	-	Abdominal pain or discomfort recurring at least 3 days per month in the past 3 months and associated with 2 or more of the following: Improves with defecation Onset associated with change in frequency of stool Onset associated with change in appearance of stool 25% of bowel movements are loose stools History of straining is also common.	Abdominal tenderness Hard stool in the rectal vault	Clinical diagnosis ROME III criteria Pharmacologic studies based criteria

Differential Diagnosis of Irritable Bowel Syndrome

The differential diagnosis of Irritable bowel Syndrome based on predominant symptoms is as follows:

Differential Diagnosis for Constipation predominant symptoms	Clinical features	Diagnosis
Strictures due to diverticultis,inflammatory bowel disease, ischemia or cancer	Obstipation, constipation	Barium enema, flexible sigmoidoscopy, colonoscopy, CT scan
Hypothyroidism	Fatigue, increased sensitivity to cold, dry skin, constipation, weight gain, puffy face, muscle weakness, hoarseness	Serum Thyroid Stimulating Hormone levels
Medication	Opiates, cholestyramine, Calcium-channel blockers, Anticholinergic medications	Medication history.
Neurologic disease	Concurrent multiple sclerosis, Parkinson disease, autonomic dysfunction(Shy-Drager)	History and neurologic examination
Pelvic floor dysfunction	Straining, self digitation	Rectal examination, defecography, anorectal manometry, balloon expulsion study
Colonic inertia	Infrequent bowel movements	Radiopaque markers, scintigraphy, wireless pH and motility capsule

Differential Diagnosis for Diarrhea predominant symptoms	Clinical features	Diagnosis
Crohn's disease	Diarrhea, abdominal pain	Colonoscopy, small bowel barium radiograph, CT enterography, magnetic resonance enterography
Ulcerative colitis	Present with abdominal pain, tenesmus, have diarrhea and rectal bleeding	Colonoscopy
Microscopic colitis	Watery diarrhea with nocturnal symptoms	Colonoscopy, flexible sigmoidoscopy and biopsy
Celiac disease	Diarrhea, steatorrhea, anemia	Endoscopy with small bowel biopsy, Tissue transglutaminase antibody
Neuroendocrine tumor	Gastrinoma, Carcinoid and VIP producing tumor	Urine 5HIAA, fasting gastritis(followed by secretin stimulation test), serum VIP
Hyperthyroidism	Increased appetite, insomnia, diarrhea, palpitations, heat intolerance, increased sweating	Serum TSH levels
Lactose intolerance	Flatulence, bloating with lactose consumption	Avoidance trial, lactose breath test
Infectious causes	Abdominal discomfort, diarrhea especially in the setting of recent travel	Stool for ova and parasites, stool Giardia antigen, stool culture, trial of metronidazole
Small bowel bacterial overgrowth	Bloating, diarrhea, abdominal distension	Jejunal aspirate, lactulose breath hydrogen test, antibiotic trial
Clostridium difficile infection(Psuedomembranous colitis)	Recent antibiotic treatment	Stool Polymerase Chain reaction

Differential Diagnosis for Pain predominant symptoms	Clinical Features	Diagnosis
Aerophagia, bloating	Anxiety may cause air swallowing	Abdominal radiograph
Intermittent small bowel obstruction	More likely with a history of previous abdominal surgeries	Abdominal radiograph, small bowel barium radiograph, CT scan
Ischemia	Intestinal angina especially in patients with atherosclerosis, weight loss, aversion to food, pain half an hour after meals	Mesentric angiography, Doppler USG, CT angiography
Chronic pancreatitis	Epigastric pain	Abdominal radiograph to assess for calcifications, endoscopic USG, CT scan
Endometriosis	Menstrual associated symptoms, pelvic symptoms	Diagnostic laproscopy
Acute Intermittent Porphyria	Rare, may have elevated liver enzymes and neurologic symptoms	Seum and urine porphyrins, especially porphobilinogen and amino levulinic acid