BODY CT PROTOCOL DESIGN


 
General abdomen/pelvis
 Oral contrast:  
● PO water (1000 mL) is given for most indications to help distend the bowel and better visualize the bowel wall and pancreatic head.
● Positive oral contrast is usually not necessary, except in the following circumstances:
○  Concern for intraabdominal abscess. Can help distinguish intraluminal fluid from extraluminal fluid.
○  Enterocutaneous fistula
1. Venous phase of abdomen and pelvis
 
Appendicitis
 Oral contrast:  Not required.
1. Venous phase of abdomen and pelvis
 Pearls 1,2       
● IV contrast is more important than oral for appendicitis.
● Ideally, oral contrast filling the appendix lumen excludes diagnosis, but in reality this requires too long of a delay.
● We do not use rectal contrast.
● USE MPRS and THIN SECTIONS, shown to improve ability to identify appendix and diagnostic confidence.
Illustrative cases
 
Case 1: 65 year old man with transmural appendicitis at pathology. Axial image (A), coronal MPR (B) from MDCT with IV contrast only show obstructed, fluid filled appendix with wall thickening and periappendiceal stranding, new from prior exam. Appendiceal obstruction and inflammation can be confidently diagnosed without oral contrast when IV contrast is administered.

(A) Axial CT
(B) Coronal MPR
Case 2: 63 year old man with acute appendicitis of the distal appendix. On axial images (A), the proximal to mid appendix (yellow arrow) is normal, and the inflamed distal appendix (oval) is not as well appreciated as on the coronal MPR (B).

(A) Axial CT
(B) Coronal MPR

1. Johnson PT, Horton KM, Kawamoto S, Eng J, Bean MJ, Shan SJ, Fishman EK. MDCT for suspected appendicitis: effect of reconstruction section thickness on diagnostic accuracy, rate of appendiceal visualization, and reader confidence using axial images. AJR Am J Roentgenol. 2009 Apr;192(4):893-901.

2. Paulson EK, Harris JP, Jaffe TA, Haugan PA, Nelson RC. Acute appendicitis: added diagnostic value of coronal reformations from isotropic voxels at multi-detector row CT. Radiology. 2005 Jun;235(3):879-85.
Bowel ischemia
Oral contrast:  PO water (1000 mL) can help better delineate the bowel wall. Do not give positive oral contrast, which can obscure the bowel wall.
 
 1. Arterial phase of abdomen and pelvis
 2. Venous phase of abdomen and pelvis
● Need to evaluate patency of both mesenteric arteries and veins.
 
Illustrative case: 91 year old male who presented with severe abdominal pain due to obstruction and bowel infarction. Arterial phase axial (A) and coronal (B) images demonstrate a dilated loop of small bowel in the right lower quadrant with hypoenhancing wall, as well as mesenteric fluid/stranding. At surgery, infarcted bowel secondary to adhesion was identified.

(A) Axial
(B) Coronal
GI hemorrhage
Oral contrast:   Do NOT give positive oral contrast! It can obscure intraluminal blood.
 
 1. Arterial phase of abdomen and pelvis
 2. Venous phase of abdomen and pelvis
● Change in morphology between arterial and venous phases confirms that hyperattenuating intraluminal material is hemorrhage. Ingested material (e.g. pills) will appear the same on arterial and venous phases.
● Can also provide information regarding rate of hemorrhage.
 
Illustrative case: 66 year old man with right colon diverticular hemorrhage. Although apparent on arterial phase (A), the gastrointestinal hemorrhage in the cecum is confirmed by detecting an increase in the hemorrhage from arterial to venous phase (B). The extent of hemorrhage is more apparent on the coronal MPRs (C,D).

(A) Axial arterial
(B) Axial venous

(C) Coronal arterial
(D) Coronal venous
IBD (inpatient or ED)
Oral contrast: PO water (1000 mL), if tolerated.
 
 1. Venous phase of abdomen and pelvis
Illustrative case: 30 year old woman with Crohn disease. Lumen of distal small bowel is filled with fluid enabling visualization of enhancing inflamed bowel wall (arrows) on coronal MPR (A) and sagittal MPR (B).

(A) Coronal
(B) Sagittal
IBD (CT enterography)
NPO for food 4-5 hours before study.
Oral contrast: A total of 1350 mL of the neutral oral contrast agent VoLumen VoLumen is a mixture of sorbitol and very dilute barium (0.1% w/v), and results in improved bowel distension compared to water alone. is given as follows:
● 1st Dose: 450 ml (Drink slowly within the first 10 minutes)
● 2nd Dose: 450 ml (10 minutes after 1st dose)
● 3rd Dose: 450 ml (10 minutes after 2nd dose)
 
 1. Arterial phase of abdomen and pelvis
 2. Venous phase of abdomen and pelvis
 
     For further information:
1. Raman SP, Horton KM, Fishman EK. Computed tomography of Crohn's disease: The role of three dimensional technique. World J Radiol. 2013;5(5):193-201.
2. Fishman, E. (2015, December 30). GI: CT Enterography - Siemens Flash Dual Source. Retrieved January 25, 2016, from http://www.ctisus.com/protocols/49497
SBO
Oral contrast: PO water (1000 mL), if tolerated.
 
 1. Venous phase of abdomen and pelvis
 
 
BROUGHT TO YOU BY:          MY-LINH NGUYEN, MD            KRISTIN PORTER, MD, PHD          PAMELA JOHNSON, MD
Icons made by Freepik and Yannick from flaticon.com and licensed under [CC BY 3.0]