Post #19:  How to Avoid Peer-to-Peer calls by selecting the correct contrasted CT scan: CT without contrast, with contrast, or a dual study (without and with contrast) - Part I

When I worked as medical director for a Radiology Benefits Management (RBM) company, I performed countless peer-to-peer phone conversations (P2P) clarifying the finer points of CT contrast.  Providers would correctly request a CT abdomen, but did not know whether contrast should be part of the exam or not.  Although many of the denied requests were eventually overturned and approved with the correct contrast component, much physician time was wasted. In this post, I will discuss when contrast should be used so as to avoid denials and P2P calls. 

Few primary care physicians, nurse practitioners, and physician assistant have had much formal training in image ordering, thus the wrong study may often be requested, resulting in a denied request.  They may request a CT when evidence-based guidelines prefer an MRI. They may request a contrast CT when a non-contrast CT is preferred.  Over the years, with improvement in technology and the quality of CT scanning, scans previously requiring dual contrast studies (contrast and non-contrast) 20 or 30 years ago may no longer require both imaging studies.  

Oral or IV contrast?  
Some physicians are confused as to the term “CT contrast,” and whether that term refers to oral contrast or IV contrast.  This is a critical point in abdominal imaging authorization because CT scans and their contrast components are identified by  specific CPT codes, and ordering the inappropriate code will result in a denial.  

When a CT abdomen or CT abdomen and pelvis is requested with contrast  (74160 or 74177) it refers exclusively to IV contrast.  CT scans requested without IV contrast use different CPT codes (74150 for CT abdomen without IV contrast and 74176 for CT abdomen and pelvis without IV contrast). Non-contrast CT scans are useful when searching for kidney stones or foreign bodies.  Non-contrast CT is also chosen for patients who cannot tolerate CT dye.  

Oral contrast in CT scanning is usually employed at the discretion of the radiologist and is helpful to highlight and visualize the GI tract.  Oral contrast does not change the CPT code.  For example, CT abdomen with IV contrast is coded 74160 whether or not oral contrast is administered.  Similarly, CT abdomen without contrast is coded 74150 whether or not oral contrast is given.  So a non-contrast CT abdomen (74150) may be performed with oral barium and still be a non-contrast CT.  

One imaging study that is occasionally ordered by gastroenterologist and performed with both IV and oral contrast is a CT enterogram. This study is for suspected or known inflammatory bowel disease.  Contrast is administered IV plus large volumes of ingested neutral bowel contrast material is swallowed to allow visualization of the small bowel; sort of a combination CT and Upper GI series with small bowel follow-through.  

The majority of CT scans of the abdomen are performed with contrast, because iv contrast highlights visceral blood vessels and allows the radiologist to characterize lymph nodes in the abdomen more clearly.   Non-contrast abdominal CT is the preferred  imaging study when patients are unable to tolerate contrast agents (because of allergy to CT dye or renal insufficiency). Diabetics and the very elderly may also develop acute renal insufficiency from contrast dye, and so non-contrast CT may be appropriately requested.  In the absence of renal concerns, CT abdomen without contrast has one other use: in the characterization of an adrenal nodule or mass.  Non-contrast CT is also used for suspected or known kidney stone, but these scans are usually ordered as CT abdomen and pelvis without contrast (74176), not as a CT abdomen without contrast (74150)  

CT for adrenal nodules are unique because such lesions are usually discovered on a CT chest or CT spine as an incidental finding, and have thus carry the label “adrenal incidentaloma”. Non-contrast CT abdomen is the recommended initial scan in order to calculate the lesion’s density (as measured in Hounsfield Units-HU). If the density is less than 10 HU the lesion is a benign lesion, and additional imaging is unnecessary.  If density is greater than 10 HU, advanced imaging is necessary, and will be described in the next post (Part II). 

Lesson #19:  The initial evaluation of abdominal signs or symptoms often begins with an ultrasound screening study unless a red flag sign is present. CT may be a follow-up study, and is usually performed with IV contrast.   This post outlined the few circumstances in which non-contrasted CTs should be requested, while the remainder of scans should be performed with contrast.  In the next post (Part II) I will expand contrast indications to include those examples when dual (without and with contrast) or triple (without contrast, with contrast, and delayed view) studies should be requested.