CT Abdomen

Aka: CT Abdomen, Abdominal CT, CT Abdomen and Pelvis, Abdominopelvic CT, Intravenous Contrast for Abdominopelvic CT, Oral Contrast for Abdominopelvic CT

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II. Background

  1. Modern CT Scanners capture isotropic voxels (3 dimensional pixels)
    1. Voxels allows for software recompositing of imaging into any slice plane (e.g. coronal slices)
    2. Does not require specific instructions beyond overall imaging technique (e.g. IV contrast)
    3. Jaffe (2007) Radiology 242:175-81 [PubMed]

III. Indications: Acute Abdominal Pain (Oral water and IV Contrast unless otherwise noted)

  1. Appendicitis
  2. Diverticulitis
  3. Bowel Obstruction
  4. Acute Pancreatitis
  5. Ureterolithiasis or Nephrolithiasis (no contrast)
  6. Abdominal Aortic Aneurysm (IV contrast only)
  7. Mesenteric Ischemia
  8. Crohn's Disease (CT enterography)
  9. Abdominal Trauma (IV contrast only)
  10. Intraabdominal abscess (with Oral Contrast in addition to IV contrast)

IV. Technique: Oral Contrast

  1. Most Abdominal CT protocols require oral water only (no Oral Contrast)
    1. Patients with increased abdominal fat require less contrast
    2. Evaluation for Appendicitis or Diverticulitis does NOT require Oral Contrast
  2. Low Attenuation Contrast (air, water) is usually preferable to high attenuation Oral Contrast (e.g. barium, diatrizoate)
    1. High attenuation contrast may obscure malignancy and intestinal Hemorrhage
    2. Air alone is an excellent contrast due to low attenuation (-1000 Hounsfield Units)
      1. Allows for pneumoperitoneum (perforation) detection
    3. Oral water (400-600 ml) immediately prior to CT helps identify gastric lesions
      1. Water distends Stomach and differentiates gastric masses from Stomach wall
    4. References
      1. Broder (2018) Crit Dec Emerg Med 32(6): 12-3
  3. High Attentuation Oral Contrast (Gastrografin/Gastroview, Omnipaque, Readi-Cat/Barium) Indications
    1. Patient indications for Oral Contrast
      1. Lean patient (e.g. BMI <19-20 kg/m2)
      2. Age <18 years old
    2. Condition indications for Oral Contrast
      1. Bowel Fistula
      2. Bowel perforation or Peptic Ulcer perforation
      3. Intraabdominal Abscess
  4. References
    1. Anderson (2005) Am J Surg 190(3): 474-8 [PubMed]
    2. Garcia (2013) Acad Emerg Med 20(8): 795-800 [PubMed]
    3. Harrison (2013) West J Emerg Med 14(6): 595-7 [PubMed]

V. Technique: Intravenous Contrast

  1. Types
    1. Non-Contrast CT
    2. Single Phase CT
      1. Imaging at a single time period after contrast injection
    3. Multi-Phase CT
      1. Imaging at more than one time period after contrast injection
      2. Generally avoided if possible due to greater radiation exposure
      3. Used in Blunt Abdominal Trauma to highlight vascular, parenchymal and urinary tract injuries
  2. Non-Contrast CT (or precontrast CT)
    1. Clearly delineates intraabdominal anatomy and identifies abnormal lesions
    2. Preferred imaging when Ureteral Stone is suspected
      1. Ureteral Stones are also seen well on IV contrast imaging (but avoid Oral Contrast)
    3. Non-Contrast CT also has high sensitivity for other conditions in which contrast is often used
      1. Pneumoperitoneum
      2. Abdominal Aortic Aneurysm
      3. Appendicitis
      4. Diverticulitis
      5. Small Bowel Obstruction
    4. Low sensitivity for lesions requiring CT contrast (high False Negative Rate)
      1. Vascular abnormalities (e.g. dissection, vessel obstruction, active Hemorrhage with extravasation)
      2. Solid organ infarction
      3. Biliary obstruction (surrounding liver parenchyma enhances with IV contrast)
      4. Solid organ mass (IV contrast highlights mass borders and invasion)
        1. With IV contrast, masses may be bright if hypervascular or enhance less if hypovascular
  3. Early Arterial Phase (15 to 25 sec after contrast injection)
    1. Evaluates for arterial pathology (e.g. Aortic Dissection, Mesenteric Ischemia, vascular injury)
  4. Late Arterial Phase (30 to 40 sec after contrast injection)
    1. Evaluates for vascular injury or dissection
    2. Also evaluates for hypervascular solid organ lesions (e.g. Hepatocellular Carcinoma)
  5. Pancreatic Phase (40 to 50 sec after contrast injection)
    1. Evaluates pancreatic lesions
  6. Portal Venous Phase (60 to 90 sec after contrast injection, Standard CT Timing)
    1. Standard CT imaging timing is the default protocol that identifies most pathology
    2. Primary imaging phase used in undifferentiated Abdominal Pain and solid organ Trauma
  7. Nephrogenic Phase or delayed phase (85 to 120 sec after contrast injection, e.g. CT Urogram)
    1. Additional images obtained as Kidney is clearing IV contrast
    2. Evaluates for renal and ureteral pathology, ideal for evaluation of persistent Hematuria source
    3. Also identifies urinary tract fistulas, masses
  8. Excretory Phase (5 to 10 minutes after contrast injection)
    1. Evaluates for urinary tract injury or leak

VI. Adverse Effects: Children

  1. Sold-tumor risk from CT radiation exposure in children
    1. See CT-associated Radiation Exposure
    2. Girls: 1 new cancer per 300-390 CT Abdomen and Pelvis
    3. Boys: 1 new cancer per 670-760 CT Abdomen and Pelvis
    4. Miglioretti (2013) JAMA Pediatr 167(8): 700-7 [PubMed]

VII. References

  1. Ashoo, Orman and Hollander in Herbert (2015) EM:Rap 15(6): 17
  2. Broder (2022) Crit Dec Emerg Med 36(5): 20-1
  3. Broder (2024) Crit Dec Emerg Med 38(8): 22-3

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Related Studies

Ontology: CT of abdomen (C0412620)

Concepts Diagnostic Procedure (T060)
ICD9 88.01
ICD10 1962 , 56401-00
SnomedCT 169070004, 303670004, 146290008
CPT 74150, 1010526
LNC LA15396-7
English Computerized tomography of abdomen, CT of abdominal organs (procedure), Computed tomography of abdomen (procedure), Computed tomography of abdomen, CT of abdominal organs, CT of abdomen, CT scan of abdomen, abdominal CT scan, computed tomography of abdomen, computed tomography of abdomen (procedure), Computerised tomography of abdomen, ct abdomen scan, ct of abdomen, ct scan abdomen, abdomen ct, abdomen ct scanning, abdomen ct scans, cat scan abdomen, abdomen cat scan, abdomen ct scan, cat scan of abdomen, ct abdomen, CT scan abdomen, Computed tomography of abdominal organs (procedure), CT of abdomen (procedure), Computed tomography of abdominal organs, Computed tomography, abdomen, CT scan - abdominal, Computerized axial tomography of abdomen, C.A.T. scan of abdomen, CT scan;abdomen, CT scan of the abdomen
Spanish tomografía computarizada de órganos abdominales, tomografía computarizada de órganos abdominales (procedimiento), TC de órganos abdominales, TAC de abdomen, TC de abdomen, tomografía computarizada de abdomen (procedimiento), tomografía computarizada de abdomen
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: CT of abdomen and pelvis (C1641132)

Concepts Diagnostic Procedure (T060)
ICD10 1963 , 56501-00
SnomedCT 419394006
CPT 74176, 74178, 1020544
Spanish TC de abdomen y pelvis, tomografía computarizada de abdomen y pelvis (procedimiento), tomografía computarizada de abdomen y pelvis
English Computerised tomography of abdomen and pelvis, Computerized tomography of abdomen and pelvis, ct scan abdomen and pelvis (procedure), ct scan abdomen and pelvis, CT scan of abdomen and pelvis, Computed tomography, abdomen and pelvis, CT of abdomen and pelvis, Computed tomography of abdomen and pelvis (procedure), Computed tomography of abdomen and pelvis
Derived from the NIH UMLS (Unified Medical Language System)

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