the potential value of adding colonic sonography

7/27/2019 The Potential Value of Adding Colonic Sonography

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Journal of Diagnostic Medical Sonography

27(3) 103 –111

© The Author(s) 2011

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DOI: 10.1177/8756479311407198

http://jdm.sagepub.com

JDM27 10.1177/875479 11407198L aulty

1Department of Diagnostic Imaging, The Ottawa Hospital,

Ottawa, Ontario, Canada2School of Dentistry and Health Sciences, Charles Sturt University,

Wagga Wagga, New South Wales, Australia

Corresponding Author:

Lysa Legault Kingstone, MAppSc, RDMS, RVT, CRGS, CRVT, RT

(MR), Department of Diagnostic Imaging, The Ottawa Hospital,

1053 Carling Ave, Ottawa, Ontario K1Y 4E9, Canada

Email: [email protected]

The Potential Value of Adding Colonic

Sonography to Routine Abdominal

Protocol in Patients With Active Pain

Lysa Legault Kingstone, MAppSc, RDMS, RVT, CRGS, CRVT, RT (MR)1,

Ania Z. Kielar, MD, FRCPC1, Matthew McInnes, MD, FRCPC1,

and Hans Swan, BSc (Hons), PhD2

Abstract

Abdominal sonography examinations include evaluation of solid intra-abdominal organs but do not routinely include

assessment of the colon. The focus of this study was to determine the utility of colonic sonography in addition toabdominal imaging in the prospective evaluation of patients with nonspecific acute or subacute abdominal symptoms.

Patients referred for abdominal sonography for investigation of abdominal pain were evaluated by performing routineabdominal sonography followed by a detailed colonic sonographic examination. Final diagnosis was established by

a clinical history questionnaire. Twelve colon (46%) or colon-related pathologies were identified, occurring in thecohort of 26 patients with a mean age of 23 years (range, 18–77 years). Sonographic findings included normal colon (n = 13),

inflammatory bowel diseases (n = 6), diverticular disease (n = 5), and colon-related ancillary findings (n = 1). Thededicated colon sonographic examination yielded a sensitivity of 91.6%, specificity of 92.8%, positive predictive value

of 91.6%, and negative predictive value of 92.8% (P < .17). Integrating the dedicated colon sonographic examination inaddition to the routine abdominal sonography identified significant bowel disease and provided additional information

regarding causes of patient symptoms. As this is a pilot study, additional prospective studies in larger populations arerequired to confirm the results and conclusions.

Keywordscolon, abdominal, disease, subacute, sonography

In tertiary care hospitals, abdominal sonography is com-

monly the first imaging study performed in patients pre-

senting with abdominal pain.1–3 Abdominal sonography

examinations include evaluation of intra-abdominal and

retroperitoneal organs but do not routinely include assess-

ment of the colon. The potential value of evaluating the

colon with abdominal sonographic imaging during a rou-

tine abdominal sonogram may identify potential causes

for the pain and help achieve a proper diagnosis in a moreefficient manner.1,2,4–6 Identification of bowel pathology

by sonography may also decrease the need for radiation

exposure that would occur with additional cross-sectional

computed tomography (CT) imaging. In addition, effi-

ciency of final diagnosis and patient disposition may be

increased by enabling streamlined triage of the cases that

have been evaluated with colonic sonography.1

Published studies2–10 have evaluated the accuracy of

colon imaging, including the range of pathological condi-

tions identifiable using sonography. Pathologic processes

that affect the colon include inflammatory, infectious,

ischemic, and neoplastic conditions; these conditions can

be identified and assessed on sonography using a high-

resolution transducer.1,2,4,7,10 Based on previously pub-

lished results, the inclusion of a detailed colon interrogation

for patients experiencing acute or subacute abdominal

pain may be beneficial for diagnosing abnormalities that

may be related to the gastrointestinal tract.1 The objective

of this prospective study was to determine the utility of

colonic sonography in addition to routine abdominal sono-graphic imaging in the prospective evaluation of patients

Original Research



Legault Kingstone et al. 105

Figure 1. Longitudinal view of the five normal layers of the colon wall (arrows). The first echogenic central l ine

represents the interface between the thin epithelium andthe lumen (A). The second is a hypoechoic line representingthe muscularis mucosa (B). Next, there is a moderatelyhyperechoic layer that is the submucosa (C). Following is amore pronounced hypoechoic layer, which consists of thecircular and longitudinal muscle layers or the muscularispropria or externa (D). Finally, the outer hyperechoic layerrepresents the interface between the serosa and the adjacentperitoneal fat (E).

Any pathological segments were imaged more exten-

sively, with possible inclusions of cineloop and/or power

or color Doppler imaging. Results of the routine abdomi-nal scan were reported without any changes to the stan-

dard of care for a routine abdominal sonogram. If any

significant colon abnormalities were detected, the radi-

ologists also reported these findings. Results of abnor-

malities detected on abdominal sonography were directly

communicated to the ordering physician.

Institutional patient medical records were reviewed

for outcome information, when available. Additional

follow-up information was obtained on all patients through

the completion of a clinical questionnaire. The question-

naire included information relating to the patient’s cur-

rent health status, clinical workup, and outcome sincehaving the sonographic examination, including additional

imaging, surgery, laboratory workup, or physical exami-

nations done by their own or referred physician. The

questionnaire was conducted by telephone three months

after the sonographic examination, and all patients, regard-

less if they had follow-up imaging or surgical intervention,

completed the questionnaire. Gold-standard cross-sectional

imaging or surgical exploration of the colon was unavail-

able in all patients, but for those who underwent any

gold-standard imaging or follow-up, sensitivity and spec-

ificity of the colon sonographic examination were calcu-

lated in comparison to the gold standard.

Statistical Analysis

The utility of colon sonography with regard to the pres-

ence or absence of colon disease was evaluated by calcu-

lating the sensitivity, specificity, and positive and negative

predictive values together with 95% confidence intervals.

Accuracy cannot be definitively calculated since there was

no gold-standard surgical or cross-sectional follow-up test

for each patient. In the absence of a gold standard, the

clinical course was based on the questionnaire answers to

determine the final diagnosis or outcome for every patient.

History, gender, prospective sonographic diagnosis,

segment of colon affected, focal versus diffuse disease,

abnormal colonic wall thickening, ancillary findings, clin-

ical diagnosis, additional imaging examinations, and clini-

cal findings were each considered categorical explanatory

variables. Degree of concordance was measured between

the sonographic classification of disease and disease clas-

sification based on the additional imaging and clinical/surgical findings. A logistic regression analysis model was

created using quasi-separation of data points to measure

our data. This method allowed us to assess the significance

of the association between the positive colon sonographic

examination and the probability of true colon disease. This

analysis was also used to estimate the rate of false-positive

and false-negative diagnoses.

Results

Of the 30 patients initially identified, 26 were included

in the final analysis for this pilot study. Two patientswere unable to provide follow-up and were therefore

excluded from the study. Two patients initially recruited

were pregnant, which led to their exclusion from the

study. The cohort of the 26 patients had a mean age of

23 years (range, 18–77 years). The group was com-

posed of 3 men (12%) and 23 women (88%). The clini-

cal indications of the patients included pain in the right

lower quadrant (27%), general abdominal pain (15%),

right upper quadrant pain (15%), epigastric pain

(11.5%), right-sided pain (11.5%), left lower quadrant

pain (11.5%), and left-sided pain (8%). The dedicated

colon interrogation took between 3 and 10 additionalminutes to complete.

All 26 (100%) of the patients included in the study had

clinical follow-up with their physicians or had additional

cross-sectional imaging. Thirteen patients (50%) had

additional cross-sectional imaging within three months of

the sonographic examination, confirming the normal or

abnormal findings. Twelve (46%) colon or related abnor-

malities were identified with the additional colon visu-

alization. Nine of the 12 colonic abnormalities identified

with sonography were confirmed with CT (n = 5),

magnetic resonance imaging (MRI; n = 1), or surgical

pathological report (n =

3) within three months of the



106 Journal of Diagnostic Medical Sonography 27(3)

sonographic examination, corroborating the positive

sonogram. The remaining three patients identified with

colon abnormalities during sonography were diagnosed

and treated solely based on the sonographic findings;

concordance with their symptoms was made through

clinical follow-up (i.e., true-positive sonograms). Colon-

related ancillary findings such as pericolonic abnormali-

ties, including perienteric fat alterations, free fluid,

abscess, fistulas, or adenopathy, were included as a false-negative sonogram (n = 1). One case identified free fluid

in the RLQ that resulted in a diagnosis of a retrocaecal

appendicitis confirmed by MRI. The findings and results

of the positive colon sonography with follow-up are sum-

marized in Table 1. In one case, the diagnosis of diver-

ticulosis by sonography did not correlate with the MRI’s

negative results (false positive). In 13 of 14 patients for

whom the sonogram was negative for colon disease,

follow-up did not detect any colon disease (true negative).

In all cases where positive colonic sonography findings

were confirmed with another imaging modality, the loca-

tion and disease type correlated.

Using additional cross-section imaging and surgical

pathology reports as the gold standard that was available

in 50% of the cases, the dedicated colon sonography

yielded a sensitivity of 91.6% and a specificity of 92.8%

using a 95% confidence interval with a total width of the

30%. The positive predictive value (PPV) was 91.6%,

and the negative predictive value (NPV) was 92.8%(Table 2). A significantly higher positive rate of colon

disease was observed in patients who underwent addi-

tional colon imaging (such as CT or MRI). The highest

sensitivity for sonographic evaluation of the colon was

found in the sigmoid colon: 6 of 11. The lowest sensitiv-

ity was found in the transverse colon: 1 of 10. Statistically

significant (P < .17) correlations were found between the

presence of localized pain during sonography and the

positive sonographic findings of the abnormal colon.

Table 1. Comparison of Sonography Colon Findings With Positive Clinical and Imaging Follow-Up Findings

Pt No.Pt Age, y/

Sex Final Sonography FindingsClinical, Imaging, or

Interventional Follow-Up Final Diagnosis

1 31 F Fluid-filled colon with no peristalsis inRLQ

Surgery Acute appendicitis

2 25 F Distended appendix, free fluid RLQ,periappendiceal inflammation— gangrenous appendicitis

Surgery Nonperforated acuteappendicitis

3 19 F Thickened appendix (7 mm), free fluidRLQ

Surgery Acute appendicitis

4 77 F Mild diverticulosis sigmoid colon Clinical Mild sigmoid diverticulosis

5 47 F Muscular propria thickening with singlediverticulum, surrounding echogenicfat in sigmoid colon—acuteuncomplicated diverticulitis

CT Sigmoid diverticulitis

6 24 M Free fluid in lower quadrants,prominent peristalsis in large colon

CT Pneumatosis cystoides of largebowel with sparing of rectum

7 72 M Echogenic material in appendix, single

diverticulum in sigmoid colon

CT Uncomplicated acute

appendicitis anduncomplicated colonicdiverticulosis

8 66 F Prominent/abnormal ileocecal valve,diverticula sigmoid

CT Diverticulosis of sigmoid colonby sonography and CT

9 29 M Severe thickening of ascending colon athepatic flexure, moderate amount of free fluid

CT Acute uncomplicateddiverticulitis of the hepaticflexure

10 77 F Mild diverticular thickening in sigmoidcolon

Clinical Mild diverticulosis

11 23 F Borderline prominence of terminalileum

Clinical Irritable bowel disease

12 29 F Free fluid in RLQ MRI Acute uncomplicatedretrocecal appendicitis

CT, computed tomography; MRI, magnetic resonance imaging; RLQ, right lower quadrant.




Figure 2. (A) Acute uncomplicated diverticulitis of the hepatic flexure. Sonographic transverse view of the ascending colonadjacent to the curvature of the liver in a man in his late 20s with vague right-sided abdominal pain. Arrow indicates there isdiffuse wall thickening with loss of layer stratification and delineation along with pericolonic fat changes (patient 9 in Table 1).(B) Acute uncomplicated diverticulitis of the hepatic f lexure. Follow-up computed tomography identified multiple scattereddiverticula (arrow) throughout the colon with moderate amount of stranding and pericolonic inflammatory process at the hepatic

flexure. Images were consistent with acute uncomplicated diverticulitis of the hepatic f lexure of the colon, explaining the rightupper quadrant symptomatology (patient 9 in Table 1).

Table 2. Concordance Between Sonography, Gold-Standard Diagnosis, and Clinical Correlation in the Diagnosis of Colon Disease

in 26 Patients

Gold Standard (CT, MRI, Surgical Intervention)

Present (Disease Posit ive): True Positive Absent (Disease Negative): False Positive Total

Sonography positive 11 1 12

Clinical Follow-Up Diagnosis

Present (Disease Posit ive): False Negative Absent (Disease Negative): True Negative Total

Sonography negative 1 13 14

Total 12 14 26

CT, computed tomography; MRI, magnetic resonance imaging.

Sonographic Findings and Disease Type

In 12 cases (46%), an abnormal colonic or related sono-

graphic finding was present. Findings of diverticular dis-

eases were sonographically depicted in five (19%) cases

(Figure 2A,B). Inflammatory bowel disease, including

appendicitis, was found in six (23%) cases. One of the

positive appendicitis findings included a gangrenous

appendicitis (Figure 3). Colon-related ancillary findings

such as pericolonic abnormalities, including free fluid,

were found in one (4%) case. Bowel inflammation, includ-

ing appendicitis, occurred mainly in the younger popula-

tion (mean age 35.2 years), whereas the older population

(mean age 61.3) tended to have colonic abnormalities




Figure 3. Acute gangrenous appendicitis. Longitudinal viewof the right lower quadrant showing marked distensionof the appendix with loss of appendiceal wall delineationand linear echogenic material (arrows) within the anteriorwall. Sonographic evidence of a moderate degree of periappendiceal inflammation and surgical pathological reportconfirmed gangrenous appendicitis (patient 2 in Table 1).

since abdominal pain is commonly related to gastrointes-

tinal disease.1 According to Lim,3 the detection of inci-

dental tumors and other bowel pathology, even in the

asymptomatic patient, warrants the inclusion of the colon

on a routine abdominal sonogram. As suggested by

Gritzmann et al.,5 the gastrointestinal tract should be

incorporated into the sonographic examination of the

abdomen, especially if the symptoms could be related.

Over the past decade, there has been a growing interest

expressed in the literature for including the colon as part

of the regular imaging protocol when looking for a pos-

sible source of abdominal pain.4

Few available published articles use sonography as the

primary imaging tool in patients with a clinical suspicion

of colon disease. A study by Parente et al.8 employed

sonography as the initial diagnostic imaging tool to pro-

spectively examine 487 patients with bowel symptoms or

signs suggestive of inflammatory bowel disorders. The

investigators determined that the overall sensitivity and specificity of colon sonography were 85% and 95%,

respectively, whereas the PPV was 98% and the NPV was

75%. By contrast, in one of the two other studies that

included patients with symptoms suggestive of colon car-

cinoma, the global sensitivity of sonography was lower

(79%), with an overall specificity of 92% and a PPV and

NPV of 81% and 91%, respectively.10 Differences in the

study populations, patient selection, prevalence of dis-

ease, type of sonographic equipment, sonographic opera-

tor experience, and the use of protocols to distinguish

abnormal colon segments by sonography may explain

some of the differences in results between these studies.In addition to the limited numbers of available studies,

CT is the primary investigative test recommended for

many patients experiencing acute abdominal pain.6,12

Stoker et al.,12 in a study assessing various imaging strat-

egies for patients with acute abdominal pain, determined

that using sonography first and then CT only for those

with negative or inconclusive sonographic examinations

resulted in the best sensitivity in addition to reduced radi-

ation exposure. Despite the greater accuracy of CT after

clinical evaluation, the authors determined that sonogra-

phy resulted in the highest overall sensitivity, with only

6% of urgent conditions missed. Although Puylaert6

reit-erated that sonography is being used less often than CT in

evaluations of the acute abdomen, he delineated specific

advantages of sonography over CT, including the lack of

ionizing radiation, a higher spatial resolution for target

organs such as the colon, the benefits of dynamic real-

time scanning, test availability, and the benefits of direct

communication with patients, which often lead to a better

diagnostic sonographic examination. However, sonogra-

phy does have some relevant limitations, such as reduced

penetration in patients with a large patient body habitus

associated with diverticular disease such as diverticulitis.

There were no statistically significant relationships identi-

fied between colon disease and a particular segment of the

bowel, patient gender, or type of pathology. Of the sono-

graphically abnormal cases, 40% of disease was located in

the sigmoid colon and 30% in the RLQ; 20% of cases

involved both the sigmoid colon and RLQ or the ascend-

ing and sigmoid colon, whereas the remaining 10% involved the ascending colon alone. One case of pneumatosis involved

the entire colon (Figure 4A,B).

In 14 cases (54%), sonography of the colon was nor-

mal. For these patients, clinical follow-up was left to the

discretion of the referring physician. Abnormal sono-

graphic findings outside the colon were found in five of

these patients; these findings included two cases of chole-

lithiasis, two gynecological abnormalities, two urinary

tract findings, and one musculoskeletal abnormality that

were believed to explain the origin of pain in these patients.

Discussion

Sonography is increasingly being used as the first-line

imaging tool in the initial evaluation of various causes of

abdominal pain, especially in the current era of radiation

safety concerns.2,3,12 Two of the most common causes of

acute abdominal pain include appendicitis and diverticu-

litis.12 However, abdominal sonography carried out

according to conventional methods does not routinely

include imaging of the colon. The inclusion of a detailed

colon interrogation may help identify the correct diagnosis




Figure 4. (A) Pneumatosis cystoides of the colon. Sonographic image demonstrating prominent peristalsis in bowel loops withfree fluid (arrow; patient 6 in Table 1). (B) Pneumatosis cystoides of the colon with sparing of the rectum. Computed tomographyconfirmed the presence of a distended bowel with discontinuous (arrows) gas within the bowel wall consistent with evidence of pneumatosis of the entire large bowel (patient 6 in Table 1).

Figure 5. Mild diverticulosis. Example of a longitudinalsonogram demonstrating asymmetric thickening (arrow) of the muscularis propria of the sigmoid colon. The sonographicdiagnosis of diverticulosis was confirmed with clinical findings(patient 10 in Table 1).

and reduced visibility in the presence of overlapping or

gas-filled loops of bowel. In addition, there is a subopti-

mal visualization of the rectum in patients whose bladder

is not full. With the increasing momentum of the “Image

Gently” campaign,13 sonography is beginning to be used

more commonly as the first test for nonspecific abdomi-

nal symptoms.

In a normal colon, three to five depicted layers can be

visualized.11 However, with the potential limitations of

sonography, not all five layers can always be seen. Whenall five layers are visible, the first luminal echogenic line

represents the interface between the thin mucosal surface

and the bowel contents. The second layer is a hypoechoic

line, which represents the deep muscularis mucosa. Next,

there is a moderately hyperechoic layer that is the submu-

cosa. Following this is a more pronounced hypoechoic

layer, which consists of the circular and longitudinal

muscle layers of the bowel or the muscularis propria.

Finally, the outer hyperechoic layer represents the inter-

face between the thin outer serosa and the adjacent




fat.5,11,14 The colon sonographic examination is consid-

ered abnormal when one or more of the four following

features is identified:

1. Colon wall thickness is greater than 4 mm or

there is loss of the layered appearance (Figure 5).

Abnormal wall symmetry, echo texture changes,

and stratification of the bowel wall, in addition

to the location within the wall (e.g., intraluminal,

mural, or exophytic), are noted.1,2,5

2. Lack of compressibility during graded compres-

sion. Compression is important for measuring

the true thickness of the bowel wall and assess-

ing the compressibility of the segment.1

3. Focal areas of increased vascularity, as identi-

fied with either color or power Doppler imaging

4. Pericolonic abnormalities, including perienteric

fat alteration, free fluid, abscess, fistulas, or ade-

nopathy

The results of the present pilot study confirm that the

integration of a dedicated colon sonographic examina-

tion in addition to the routine abdominal sonography

identified significant colon disease in patients present-

ing with nonspecific acute or subacute abdominal pain.

In our series of patients, linear regression statistical

analysis data concluded that sonography was able to

detect 91.6% of colon disease, and each of the positive

findings was correlated with CT, MRI, or surgical

pathology reports. The overall specificity of the colonic

sonography was 92.8%, and the additional colonic eval-uation had a PPV of 91.6% and an NPV of 92.8%. This

suggests that negative sonographic findings cannot

exclude with certainty all pathologic processes in the

colon. The sigmoid colon was the most common site of

disease, and inflammatory diverticular disease was

commonly detected in this location. Segments of the

colon, such as the rectum, were more difficult to image

because of overlying gas, deep positioning, and limited

visibility. This may have negatively influenced the PPV

and NPV of the study, particularly if the patient was

symptomatic for inflammatory colon disease such as

ulcerative colitis. Other major reported potential pitfallsof colonic sonography are operator dependency and

interobserver variability. All these factors could have

affected our overall accuracy results.

The major weakness of this study includes a lack of

consistent cross-sectional or surgical follow-up, such as

CT or MRI, as a gold standard. This was not possible in

most patients, although 50% did have one of these types

of follow-up. Follow-up CT scanning in all patients, par-

ticularly in those whose symptoms resolve, is not ethical

because of radiation exposure considerations. MRI is not

as accessible and is not considered a gold standard for

evaluating the colon. Follow-up surgery or colonoscopy

would also be unrealistic. A longer follow-up period

between the original sonographic study and the subse-

quent telephone interview could potentially be of benefit.

Another possibility to reaffirm the value of the colon

sonographic examination would be to perform a follow-

up colonic sonographic examination and correlate the

findings or to simply follow a larger number of patients

and only use those who subsequently have had CT, MRI,

or surgical follow-up to reaffirm the value of the colon

sonographic examination. A larger study population is

also required to answer the question of value in a more

definitive manner. In future studies evaluating utility of

sonography for evaluating the colon, exclusion and inclu-

sion criteria should be broadened to include all requests

for imaging abdomen pain, regardless of whether there is

a specific target organ in mind. This is because the local-

ized area of pain may not stem from the suspected organ

on the sonographic request but instead may originatefrom an adjacent colon loop. Further studies evaluating

the use of sonography for evaluation of the colon during

pregnancy are also warranted. Although two pregnant

patients were excluded from our study, one demonstrated

ancillary findings on sonographic evaluation of the colon

such that she was referred for MRI, which subsequently

confirmed appendicitis.

Conclusion

Results from this prospective pilot study suggest that

inclusion of the colon in the protocol for acute adultabdominal sonography has the potential to be a valuable

method for evaluating various pathologies of colon ori-

gin. This small prospective study may be the impetus for

a paradigm shift in the usual protocol for abdominal

imaging, but larger prospective studies are indicated to

corroborate these findings.

Acknowledgments

We thank the sonography staff of the Ottawa Hospital (Ottawa,

Ontario) with special gratitude to Micheline Heroux, RDMS,

RVT, for her invaluable assistance and Dr Michael Kingstone,

MD, for assistance with the manuscript. In addition, we thank Dr Phil Wells, MD, Dr Monica Taljaard, PhD, and James Jaffey

of the Ottawa Hospital Research Institute for their assistance

with the methodology and statistical analysis.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with

respect to the authorship and/or publication of this article.

Funding

The author(s) received no financial support for the research

and/or authorship of this article.




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the potential value of adding colonic sonography

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