Introduction
Computed tomography (CT) of the abdomen is an established diagnostic procedure, and
it covers a very wide range of indications. It is often the imaging modality of choice
in both acute and elective diagnostics. Historically, abdominal CT scans were almost
always performed after additional administration of enteral contrast media (CM) to
improve the diagnostic value of the examination [1 ]. Thanks to technical developments alongside improvements in image quality in recent
decades, the indications for enteral contrast have changed and are now obsolete (and
partly even counterproductive) for many clinical questions [2 ]
[3 ].
In Germany, medical care guidelines (particularly guidelines from the Association
of Scientific Medical Societies (AWMF)) provide the basis for efficient and indication-appropriate
diagnostics and therapy for specific clinical diseases or questions. These guidelines
are intended to support decision-making in clinical practice and ensure that current
evidence-based medical standards are observed [4 ]. However, technical details regarding the specific implementation of imaging diagnostics
are rarely included (neither in national nor international recommendations). This
also includes the possible additional application of enteral CM, which is only addressed
in exceptional cases, e.g. in corresponding AWMF guidelines [5 ].
In everyday clinical practice, the lack of clear recommendations for or against enteral
CM application in abdominal CT scans regularly leads to uncertainty on the part of
referring colleagues as well as radiologists. Lengthy discussions are often the result.
In addition, scientific studies on this topic are frequently outdated and the underlying
evidence is somewhat limited [6 ]. Doing something “because we’ve always done it this way” or “because the referring
colleague wants it” is neither keeping up with the times nor should it be the focus
of patient-oriented diagnostics.
Through its online survey, the Gastrointestinal and Abdominal Diagnostics Working
Group of the German Radiological Society (DRG) aims to capture the existing status
quo of clinical practice regarding enteral contrast in abdominal CT scans in German-speaking
countries, to identify possible gaps in implementing guidelines, and to derive future
recommendation needs. In the process, the results of this survey combined with an
extensive literature review are intended to provide the basis for expert recommendations
on enteral contrast administration for a variety of clinical questions, which will
be published in a subsequent position paper. The following article provides the results
of the online survey and critically analyzes them according to subtopic. Existing
guideline recommendations, if available, are appended to the survey results and compared
accordingly in the discussion section.
Materials and Methods
In preparation for the online survey, the board of the Gastrointestinal and Abdominal
Diagnostics Working Group identified technical aspects and clinically relevant indications
for abdominal CT, with particular emphasis placed on preparatory enteral contrast.
Based on this information, we created a questionnaire using the Surveymonkey web tool
(www.surveymonkey.com ) [7 ]. The DRG made this online questionnaire available to all its members via email,
newsletter, and the DRG INTERNET portal. The survey was posted online on February
2, 2024, and was available for 70 days until April 12, 2024. The anonymized survey
was divided into eight sections for respondents to provide information about their
clinical background and their use of enteral contrast agent in abdominal CT, in general,
as well as for specific clinical questions. The survey contained a total of 61 questions,
consisting of 51 single-choice questions, 9 multiple-choice questions, and a final
open question for comments and remarks. Estimated completion time was approximately
10 to 15 minutes. The full questionnaire is provided in Supplementary Tab. 1 .
For the evaluation, we used the implemented Surveymonkey tools. Additional statistical
analysis using descriptive methods was performed using Excel (Excel: mac 2023, version
16.78, Microsoft, WA, USA) and Prism 7.0 (GraphPad Software Inc., San Diego, USA).
Results
A total of 1,001 participants completed the survey and were therefore included in
the evaluation. Respondents did not have to answer all 61 questions; individual questions
could be skipped. In the following results sections, the absolute number of responding
participants is therefore given as the defined population.
General background information on the survey participants (1,001 responses)
33.2% (n=333) of the respondents stated that they work as a practicing physician in
a medical office or medical care center, while 66.8% (n=668) work primarily as a physician
in a hospital ([Fig. 1 ]). The surveyed number of beds of radiologists working in clinical settings showed
that the majority of 74.8% (n=564) work in hospitals with fewer than 1,000 beds, and
only 25.2% (n=190) work in hospitals with more than 1,000 beds. The majority of the
participating radiologists were not in management positions. Only 13.8% were part-owners
or owners of a medical office (n=138), 10.3% were chief physicians (n=103), and 8.7%
(n=87) worked in senior physician positions. Specialist physicians were the largest
group of respondents, with 27.3% (n=273), followed by senior physicians with 24.8%
(n=248), and physicians in training with 15.2% (n=152).
Fig. 1 Professional environment of all participants. Out of the 1,001 participants, 33.2%
worked in a medical office or medical care center, 66.8% in a hospital.
General aspects of performing enteral contrast in CT (924 responses)
The survey shows that the majority of respondents generally perform enteral contrast
during abdominal CT scans. 56.5% (n=522) reported administering enteral CM in less
than half of these scans, while 43.5% (n=402) used it in 50 to 100% of cases. In this
context, enteral contrast (oral/rectal/combined) is usually performed depending on
the exact clinical question (74.8% of participants). Selective, indication-dependent
enteral CM administration for specific clinical questions is favored by over 90% (n=859)
of participants.
Positive CM in the form of water-soluble iodine compounds is preferred by the majority
of respondents for both oral (66.1%) and rectal (80.6%) contrast filling ([Fig. 2 ]). The reasons given for using an enteral CM in CT scans (multiple selections allowed)
were, in particular, a substantial diagnostic gain (69.6%) and pressure from or request
by the referring physician (30.6%) ([Fig. 3 ]). On the other hand, the decision not to use enteral contrast (multiple selections
allowed) is justified primarily by a lack of substantial diagnostic gain (73.3%),
as well as time (44.8%) and organizational (34.2%) obstacles ([Fig. 3 ]). Based on additional comments from participants, it can also be deduced that rectal
CM application, in particular, is rarely carried out or is unusual in a medical office.
Medical office or hospital-internal SOPs for the regulated use of enteral CM are available
to 54.6% of the radiologists surveyed. 85.6% of participants feel confident or very
confident determining the indication for use of enteral CM.
Fig. 2 Preferred enteral contrast agents. Positive contrast agents are preferred for oral
as well as rectal contrast filling, with water-soluble iodine compounds leading the
way.
Fig. 3 Reasons for (a ) or against (b ) enteral contrast administration in abdominal CT (multiple answers possible).
Enteral contrast for specific clinical questions
Primary staging and follow-up of tumors of the upper gastrointestinal tract (875 responses):
The frequency of performing enteral contrast administration in CT scans of the upper
gastrointestinal tract for primary staging or follow-up varies considerably among
respondents. 33.8% (n=296) stated that they only use enteral CM in a maximum of 25%
of scans. In contrast, 50.7% (n=444) applied enteral CM in more than 75% of the scans.
In the majority of cases, CM application is purely oral (80.7%; n=706) and less frequently
combined oral and rectal administration or purely rectal contrast administration (8.8%).
Positive CM in the form of water-soluble iodine compounds is used by 48%, while water
is used as a neutral CM by 34.2% of respondents. The same applies to the follow-up
of patients with known tumors of the upper gastrointestinal tract ([Table 1 ]).
Table 1 Enteral contrast application with CT for staging of upper gastrointestinal tract tumors.
Primary staging
Follow-up exam
GIST = gastrointestinal stromal tumor; HCC = hepatocellular carcinoma; CCA = cholangiocarcinoma
Esophageal carcinoma
75.5%
73.8%
Gastric carcinoma
80%
78.4%
GIST
65.8%
64.7%
Pancreatic carcinoma
64.5%
62.4%
Duodenal carcinoma
75.1%
73.4%
HCC, CCA
30.2%
29.1%
Recommendations from national guidelines: Current AWMF guidelines only contain specifications for the use of enteral CM in individual
cases during CT staging scans and follow-up exams of the upper gastrointestinal tract.
According to the S3 guideline for the diagnosis and treatment of squamous cell carcinomas
and adenocarcinomas of the esophagus, CT should be performed, including oral negative
CM, which improves T-staging due to wall distension. The so-called “hydro technique”
with 1 to 1.5 liters of water and simultaneous spasmolysis is recommended [8 ]. A similar recommendation can be found in the S3 guideline on gastric cancer or
carcinomas of the esophagogastric junction. In patients with curative therapy, the
CT scan for gastric distension should be performed using oral CM or water, and should
be combined with intravenous contrast administration. Here, too, the “hydro-technique”
should be used. This leads to improved differentiation of local findings in diagnostics,
and makes it easier to visualize infiltration or differentiation from neighboring
organs [5 ]. The guidelines for gastrointestinal stromal tumor (GIST), exocrine pancreatic carcinoma,
hepatocellular carcinoma (HCC), or cholangiocarcinoma (CCA) do not contain specific
recommendations regarding the use of enteral CM [9 ]
[10 ]
[11 ].
Primary staging and follow-up of tumors of the lower gastrointestinal tract (843 responses):
Almost half (48.1%) of the participants used enteral contrast administration in more
than 75% of the CT scans performed for initial staging or follow-up of tumors of the
lower gastrointestinal tract ([Table 2 ]). Enteral contrast is mostly administered only orally (41%), less frequently combined
orally and rectally (29.1%), or only rectally (12%). Positive CM, especially water-soluble
iodine compounds (60.7%) are preferred, followed by water (16.8%).
Table 2 Enteral contrast application with CT for staging of lower gastrointestinal tract tumors.
Primary staging
Follow-up exam
GIST = gastrointestinal stromal tumor
Carcinoma of the small intestine (excluding duodenum)
59.2%
60%
GIST
55.8%
55.4%
Colon carcinoma
71.2%
68.7%
Rectal carcinoma
71.1%
70.2%
Malignant tumors of non-solid organs
52%
51.3%
Recommendations from national guidelines: Existing national guidelines on tumors of the lower gastrointestinal tract do not
currently contain any specific recommendations regarding enteral CMp administration
during abdominal CT.
Non-traumatic acute/unclear abdomen (806 responses):
In the context of CT of the unclear, acute abdomen, enteral CM application is usually
very restrictive. The majority of respondents (57.6%) perform these tests only rarely
(in less than 25% of scans), with small variations in different suspected clinical
diagnoses ([Fig. 4 ]). If enteral contrast is used, positive CMs with water-soluble iodine compounds
are preferred in various clinical scenarios (on average in 72% of cases).
Fig. 4 Enteral contrast application in abdominal CT for different clinical questions or suspected
diagnoses, respectively.
Recommendations from national guidelines: No generally applicable AWMF guideline exists for diagnostics of the acute, non-traumatic
abdomen. The S1 guideline for appendicitis recommends against oral contrast administration,
as this would not improve the diagnosis in non-obese patients and children [12 ]. The guideline on diverticular disease or diverticulitis describes the “status quo”
with regard to technical implementation in the background text, noting that most clinics
currently perform the examination using intravenous and oral positive contrast with
diluted iodine-containing CM. In addition, rectal contrast with water-soluble CM is
recommended to better assess the rectum and sigmoid colon. However, this recommendation
also includes a note that some recent studies have dispensed with intravenous and
oral or rectal contrast media administration, which has produced the same diagnostic
results. Nevertheless, the level of evidence from these studies is currently not considered
sufficient. As a result, a re-evaluation of the literature is recommended in the years
ahead [13 ].
Traumatic acute abdomen (798 responses):
Enteral CM application during CT imaging of the acute traumatic abdomen is not generally
performed (85.1% of participants; [Fig. 4 ]). However, up to 10.2% of respondents stated that they would carry out or consider
supplemental enteral contrast administration in individual cases, mostly orally and
with water-soluble iodine compounds (65%).
Recommendations from national guidelines: The S3 guideline for polytrauma and the treatment of severely injured patients states
that a multi-slice spiral CT should generally be performed for diagnostics of intra-abdominal
injuries after abdominal trauma. If a practical implementation of oral or rectal contrast
would be possible, it could be used to better visualize intestinal injuries. There
is no concrete recommendation as to which CM should be used [14 ].
Chronic inflammatory bowel diseases (788 responses):
As part of the CT for the diagnosis of Crohn’s disease or ulcerative colitis, the
majority of respondents regularly perform (i.e. in more than 75% of scans) enteral
contrast administration (Crohn’s disease: 57% or ulcerative colitis: 54.8%; [Fig. 4 ]). Enteral CM application is primarily oral (in 56.4%), and combined oral and rectal
is used less frequently (22.1%). Mainly water-soluble iodine compounds (55.2%) are
used, and less frequently water (17.6%) and mannitol or methylcellulose (17.9%).
Recommendations from national guidelines: According to the guideline on Crohn’s disease, MR enterography should be preferred
over CT for small bowel diagnostics due to radiation exposure while offering comparable
sensitivity. CT enterography can be used in emergency situations, but the form of
enteral contrast administration is not specified [15 ].
Postoperative complication diagnostics (772 responses):
In the CT diagnosis of postoperative complications, two main approaches emerge with
regard to supplementary enteral CM administration. 46.4% of participants reported
using enteral CM in 50% or fewer of CT scans, while 53.6% used enteral CM in more
than half of the corresponding CT scans. Variations in the application method exist,
particularly in cases of suspected postoperative fistula or leakage (oral: 63.1%;
rectal: 45%; combined oral and rectal: 47.3%; via a GI tube: 46.1%; via a stoma: 45%).
92.3% of respondents primarily use positive CM with water-soluble iodine compounds.
Similar results are available when using CT to check postoperative anastomosis. If
other clinical issues (e.g. bleeding, ileus, or transit disorder) are in the foreground,
most participants do not use additional enteral CM application ([Fig. 4 ]).
Recommendations from national guidelines: The guideline literature in Germany is very limited with regard to diagnostics of
postoperative complications. In the S3 guideline for the perioperative management
of GIST, the treatment of postoperative paralytic ileus recommends against the use
of osmotically effective X-ray contrast media such as Gastrografin [16 ].
Discussion
The present study by the DRG’s Gastrointestinal and Abdominal Diagnostics Working
Group is intended to present the current status of enteral CM application in the context
of CT diagnostics of the abdomen in Germany. With a total of 1,001 participants from
radiological colleagues in hospitals and medical offices, we consider this survey
to be representative. The high level of participation also confirms the strong interest
in the topic and its clinical relevance in everyday radiology practice. We therefore
wish to thank all of the survey participants.
Overall, it can be summarized that for most colleagues, selective, indication-dependent
enteral contrast is the main focus, but on the other hand, there are sometimes considerable
differences in the technical implementation and execution. Compared to historical
patient cohorts, routine enteral CM application is increasingly being omitted as part
of abdominal CT, particularly in acute cases. Exceptions are staging scans and follow-up
exams in patients with tumor diseases, who are regularly administered enteral CM,
primarily orally in the form of water-soluble iodine compounds or water.
In the diagnosis of tumors of the upper gastrointestinal tract, the survey shows that
oral CM administration continues to play an important role. This approach is consistent
with current guideline recommendations ([Table 3 ]) and is comparable with the results of an older survey from 2016 [17 ]. The somewhat restrictive use of enteral CM in other tumor entities investigated
may be due to the lack of clear recommendations in guidelines. The results are correspondingly
heterogeneous with regard to the type of enteral contrast administration and the substances
used.
Table 3 Current existing guideline recommendations regarding enteral contrast administration
with CT in relation to various clinical questions.
Recommendations based on current guidelines
GIST = gastrointestinal stromal tumor
Esophageal carcinoma [8 ]
CT including oral, negative CM, “hydro-technique” (1–1.5l water) under spasmolysis
Gastric carcinoma [5 ]
CT including oral CM or water, “hydro-technique” with i.v. contrasting
Appendicitis [12 ]
CT without oral CM in non-obese children and adults
Diverticulitis, diverticular disease [13 ]
CT including oral, positive CM (and, if necessary, rectal), water-soluble contrast
agent with i.v. contrasting
Abdominal trauma [14 ]
CT including oral or rectal CM, if practically possible
Crohn’s disease [15 ]
CT enterography only in exceptional situations
Postoperative paralytic ileus in GIST [16 ]
Avoid osmotically effective X-ray contrast media
In acute diagnostics of abdominal complaints, enteral CM is generally applied very
cautiously. This is certainly also due to the time-critical diagnostics of the often
clinically severely impaired patients, in combination with limited diagnostic value
added [18 ]. There is one exception with regard to the diagnosis of diverticulitis, where 60%
of respondents perform CT after enteral CM administration, although there are significant
differences with regard to the type of application (oral, rectal, or combined). This
only partially reflects the current recommendations in the corresponding AWMF guideline,
and it is certainly due, in part, to the increasing number of studies demonstrating
that enteral CM application can be avoided while maintaining the same diagnostic quality
[19 ]
[20 ].
In the context of diagnostics and follow-up for chronic inflammatory bowel diseases,
and in line with current guideline recommendations, CT diagnostics and CT enterography
play a subordinate role. In postoperative complication diagnostics, the survey results
suggest that there are certain scenarios in which the use of enteral CM appears beneficial.
Above all, this includes the diagnosis of leakages, fistulas, or clarification of
anastomotic insufficiency. The majority of respondents consistently stated that they
prefer positive CM in the form of water-soluble iodine compounds. Even though there
are no specific national guideline recommendations in this regard, there are studies
that attest to the added value provided by enteral CM administration in the above-mentioned
situations [21 ]
[22 ].
In summary, the survey responses paint a very heterogeneous picture of enteral CM
application in virtually all of the questions. This is certainly also due to a lack
of recommendations (whether for or against) in relevant guidelines. In addition, there
is often a lack of internal departmental or practice-specific SOPs that could serve
as guidelines, especially for younger physicians, in their everyday radiology work.
Pressure from referring colleagues and also habit still seem to play a role in how
examinations are conducted. It would therefore be desirable, as many survey participants
stated, to implement cross-departmental recommendations based on evidence or consensus.
In response to this feedback, the results of this survey will serve as a basis for
recommendations on enteral contrast administration in abdominal CT. Selective, indication-dependent
enteral contrast administration will be the focus, including an algorithm developed
as a decision-making tool for use in everyday clinical practice. Alongside a critical
evaluation of the evidence available and taking into account (inter)national guideline
recommendations, the Gastrointestinal and Abdominal Diagnostics Working Group plans
to publish these recommendations soon in a subsequent position paper.
