Inflammatory bowel disease

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Inflammatory Bowel Disease Main page

Patient Information




Crohn's disease
Ulcerative colitis

Differential Diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Synonyms and keywords: IBD ;


Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract that represents 2 distinctive disorders, Crohn's disease and ulcerative colitis. Both disorders are characterized by unpredictable exacerbations and remissions. Genetic and environmental factors are believed to play a key role in the pathogenesis of IBD. A dysregulated immune response to environmental factors in a genetically susceptible host results in activation of cytokines, triggering a cascade of reactions ultimately bowel inflammation. Common symptoms of inflammatory bowel disease include persistent diarrhea, abdominal pain, rectal bleeding/bloody stools, weight loss and fatigue. IBD can be diagnosed using a combination of endoscopy for Crohn’s disease or colonoscopy for ulcerative colitis and imaging studies, such as contrast radiography, magnetic resonance imaging, or computed tomography. The goal of medical therapy is to induce remission initially with medications, followed by the administration of maintenance medications to prevent a relapse of the disease. Sulfasalazine along with steroids are the main stay of treatment for IBD. Immunosuppressive agents such as infliximab or 6-mercaptopurine and azathioprine are recommended alternatives to steroids.


While the causes of inflammatory bowel disease is unknown, several possibly interrelated studies have been suggested following causes:

Common causes

Genetic factors

  • Mutations in the CARD15 gene (also known as the NOD2 gene) are associated with Crohn's disease.
  • Mutations of the transporter proteins such as OCTN1 and OCTN2 and scaffolding proteins such as the MAGUK family are believed to cause ulcerative colitis.

Environmental factors

  • Alterations in normal bacterial flora of the intestinal tract is responsible for Crohn's disease.
  • Smoking: Unlike Crohn's disease, ulcerative colitis has a lesser prevalence in smokers than non-smokers.
  • Use of NSAIDs
  • Stress
  • Red meat consumption

Rare causes


Inflammatory bowel disease can be classified into Crohn's disease and ulcerative colitis.

Inflammatory Bowel Disease
Crohn's Disease
Ulcerative colitis
Based on Region involved
Based on Severity
Ileocolic Crohn's disease
Crohn's ileitis
Crohn's colitis
Stricturing disease
Penetrating disease
Inflammatory disease
Based on Region involved
Based on Severity
Distal UC
Proximal UC

Differential diagnosis

Inflammatory bowel disease must be differentiated from other diseases that present with abdominal pain, fever and diarrhea which include appendicitis, diverticulitis, Whipple's disease, mesenteric ischemia, Tropical sprue, hepatitis and spontaneous bacterial peritonitis.

Disease Clinical manifestations Diagnosis Comments
Symptoms Signs
Abdominal Pain Fever Rigors and chills Nausea or vomiting Jaundice Constipation Diarrhea Weight loss GI bleeding Hypo-


Guarding Rebound Tenderness Bowel sounds Lab Findings Imaging
Inflammatory bowel disease Diffuse ± ± + + + Normal or hyperactive

Extra intestinal findings:

Acute appendicitis Starts in epigastrium, migrates to RLQ + Positive in pyogenic appendicitis + ± Positive in perforated appendicitis + + Hypoactive
  • Ct scan
  • Ultrasound
  • Positive Rovsing sign
  • Positive Obturator sign
  • Positive Iliopsoas sign
Acute diverticulitis LLQ + ± + + ± + Positive in perforated diverticulitis + + Hypoactive
  • CT scan
  • Ultrasound
Whipple's disease Diffuse ± ± + + ± N Endoscopy is used to confirm diagnosis.

Images used to find complications

Extra intestinal findings:
Toxic megacolon Diffuse + + + ± + Hypoactive CT and Ultrasound shows:
  • Loss of colonic haustration
  • Hypoechoic and thickened bowel walls with irregular internal margins in the sigmoid and descending colon
  • Prominent dilation of the transverse colon (>6 cm)
  • Insignificant dilation of ileal bowel loops (diameter >18 mm) with increased intraluminal gas and fluid
Tropical sprue Diffuse + + + N Barium studies:
  • Dilation and edema of mucosal folds
Infective colitis Diffuse + ± + + Positive in fulminant colitis ± ± Hyperactive CT scan
  • Bowel wall thickening
  • Edema
Viral hepatitis RUQ + + + Positive in Hep A and E + Positive in fulminant hepatitis Positive in acute + N
  • Abnormal LFTs
  • Viral serology
  • US
  • Hep A and E have fecal-oral route of transmission
  • Hep B and C transmits via blood transfusion and sexual contact.
Liver abscess RUQ + + + + ± + + + ± Normal or hypoactive
  • US
  • CT
Spontaneous bacterial peritonitis Diffuse + Positive in cirrhotic patients + ± + + Hypoactive
  • Ascitic fluid PMN>250 cells/mm³
  • Culture: Positive for single organism
  • Ultrasound for evaluation of liver cirrhosis
Mesenteric ischemia Periumbilical Positive if bowel becomes gangrenous + + + + Positive if bowel becomes gangrenous Positive if bowel becomes gangrenous Hyperactive to absent CT angiography
  • SMA or SMV thrombosis
  • Also known as abdominal angina that worsens with eating
Acute ischemic colitis Diffuse + ± + + + + + + + Hyperactive then absent Abdominal x-ray
  • Distension and pneumatosis

CT scan

  • Double halo appearance, thumbprinting
  • Thickening of bowel
  • May lead to shock

Abbreviations: RUQ= Right upper quadrant of the abdomen, LUQ= Left upper quadrant, LLQ= Left lower quadrant, RLQ= Right lower quadrant, LFT= Liver function test, SIRS= Systemic inflammatory response syndrome, ERCP= Endoscopic retrograde cholangiopancreatography, IV= Intravenous, N= Normal, AMA= Anti mitochondrial antibodies, LDH= Lactate dehydrogenase, GI= Gastrointestinal, CXR= Chest X ray, IgA= Immunoglobulin A, IgG= Immunoglobulin G, IgM= Immunoglobulin M, CT= Computed tomography, PMN= Polymorphonuclear cells, ESR= Erythrocyte sedimentation rate, CRP= C-reactive protein, TS= Transferrin saturation, SF= Serum Ferritin, SMA= Superior mesenteric artery, SMV= Superior mesenteric vein, ECG= Electrocardiogram