[CT colonography : Technique and indications]

BACKGROUND

Dedicated radiological expertise and a high-quality examination, performed according to current technical standards and for accepted indications, are prerequisite to achieve excellent results with CT colonography (CTC).

OBJECTIVES

The aim of this article is to review current standards of the examination technique as well as indications and contraindications for CTC based on recent recommendations and guidelines.

MATERIALS AND METHODS

Based on extensive literature research, current knowledge about the examination technique and the indications and contraindications is summarized.

RESULTS

CTC is the radiological examination of choice for the detection of colorectal neoplasia. Beside incomplete or refused colonoscopy and contraindications to colonoscopy, CTC is also a noninvasive option for opportunistic colorectal cancer screening. The examination technique is based on a CTC-specific patient preparation scheme that includes fecal tagging, colonic distension, low-dose CT scans in two patient positions and a combined 2D and 3D data evaluation.

CONCLUSIONS

Performing CTC according to current technical standards is prerequisite for high-quality examinations and is, thus, also a key factor to obtain a correct diagnosis. CTC is a noninvasive examination, capable of providing clinically relevant diagnoses for a wide range of indications.

Acute colonic pseudo-obstruction in two patients admitted with severe acute respiratory syndrome-coronavirus-2 pneumonia

We have described two cases of severe SARS-CoV-2 pneumonia presenting with acute colonic pseudo-obstruction with normal liver enzymes and serum lactate. These older adults presented predominantly with constitutional symptoms, silent hypoxia, distended abdomen, sluggish bowel sounds, and colonic dilatation supported by abdominal imaging (plain X-ray and computerized tomography of abdomen) to a tertiary care center in South India. Both patients received standard treatment for severe SARS-CoV-2 pneumonia and acute colonic pseudo-obstruction according to available guidelines but succumbed to complications during hospital stay. Acute colonic pseudo-obstruction in patients admitted with SARS-CoV-2 infection requires high index of suspicion as it warrants early mitigation by cessation of offending agents, optimizing electrolytes, and colonic decompression to prevent morbidity and mortality.

CTC technique: methods to ensure an optimal exam

CT colonography (CTC) has demonstrated equivalent accuracy to optical colonoscopy in the detection of clinically relevant polyps and tumors but this is only possible when technique is optimized. The two most important features of a high-quality CTC are a well-prepared colon and a distended colon. This article will discuss the dietary, bowel preparation, and fecal/fluid tagging options to best prepare the colon. Strategies to optimally distend the colon will also be discussed. CT scan techniques including patient positioning and radiation dose optimization will be reviewed. With proper technique which includes sufficient bowel preparation, fecal/fluid tagging, bowel distension, and optimized scan technique, high-quality CTC examinations should become more feasible, easier to interpret, and more consistently reproducible leading to increased utilization and increased referrals.

Degree of colonic distension: intrapatient comparison between CT colonography and CT with water enema

PURPOSE

Compare colonic distension using CT colonography (CTC) and CT with water enema (CTWE) in the same patients.

METHODS AND MATERIALS

Twenty-seven patients who underwent both CTC and CTWE, considering separately supine (CTC-S) and prone (CTC-P) acquisition of CTC were included. The colon was divided into six segments, performing both a qualitative and quantitative analysis.

RESULTS

Adequate distension of sigmoid colon was more frequently achieved with CTC-P and CTWE compared to CTC-S (P<.05). CTC-P and CTWE showed better distension of the left colon compared to CTC-S (P<.01 and P=.03 regarding sigmoid colon, respectively; P=.01 and P=.03 regarding descending colon, respectively).

CONCLUSIONS

Computed tomography (CT) studies of the colon should be customized to fulfill the clinical query.