Initial Diagnosis: Peritonitis

I. What imaging technique is first-line for this diagnosis?

  • CT of the abdomen and pelvis with IV and oral contrast

  • In cases of septic shock with signs of acute peritonitis, surgical consultation should be considered with prompt resuscitative efforts

II. Describe the advantages and disadvantages of this technique for diagnosis of peritonitis.


  • Relatively quick imaging procedures that require minimal patient cooperation and are less susceptible to motion artifact than MRI

  • Able to assess for sources of infection including bowel perforation, abscess, ascites, appendicitis, pancreatitis and diverticulitis

  • Abnormal appearance to the gallbladder and adnexa may be visualized, which can be further evaluated with targeted ultrasound

  • Inflammatory stranding of the mesenteric fat can also point to a source of infection


  • Exposure to ionizing radiation

  • Potential renal injury from intravenous contrast agents

III. What are the contraindications for the first-line imaging technique?

  • Patients with allergic reactions (eg, itching, rash) to intravenous contrast

  • Patients with renal failure

  • Relatively contraindicated in pregnant women, especially within the first two trimesters.

IV. What alternative imaging techniques are available?

  • Acute abdominal series x-rays

  • Ultrasound

  • MRI

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of peritonitis.

Acute abdominal series x-rays


  • Can provide quick information regarding bowel dilation, obstruction and possible free air.


  • Findings are often nonspecific



  • For localized peritoneal signs, a targeted ultrasound may be warranted prior to CT

  • Can evaluate for signs of acute cholecystitis and choledocholithiasis

  • A pelvic ultrasound can evaluate for pyosalpinx, tubo-ovarian abscesses, ectopic pregnancy (if B-hcg is positive), and ovarian torsion.

  • Can evaluate for appendicitis in young or pregnant patients, thereby avoiding excessive radiation


  • Findings may be nonspecific

  • Not diagnostic for peritonitis



  • In pregnant women with focal right lower quadrant pain and suspicion for appendicitis, where the ultrasound is nondiagnostic, an MRI without gadolinium can be performed for further evaluation.

  • Does not require ionizing radiation


  • Expensive

  • Time consuming

  • Requires significant patient cooperation to minimize motion artifact

VI. What are the contraindications for the alternative imaging techniques?

Acute abdominal series x-rays

  • No significant contraindications


  • No significant contraindications


  • Non–MR-compatible hardware

  • Relative contraindication of contrast with renal failure

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