Blinded comparison of faecal loading on plain radiography versus radio-opaque marker transit studies in the assessment of constipation

doi:10.1016/j.crad.2008.06.011

Clinical Radiology

Volume 63, Issue 12, December 2008, Pages 1326-1331

https://doi.org/10.1016/j.crad.2008.06.011 Get rights and content

Aim

To compare faecal loading on plain radiography versus radio-opaque marker transit studies in the assessment of constipation.

Methods

The study group was a convenience sample of patients attending the Durham Constipation Clinic. All patients underwent transit studies according to an established protocol, and severity of constipation was assessed contemporaneously using a validated questionnaire (PAC-SYM). Transit studies were performed using radio-opaque markers that were ingested over 3 consecutive days, with a radiograph taken on the fourth day. Digital images of the radiograph were digitally altered to remove all traces of the transit markers without affecting the underlying pattern of faecal loading. Four observers assessed faecal loading independently; two clinicians (C1 and C2) and two radiologists (R1 and R2). C1 and R1 used a previously described formal scoring method of assessing faecal loading, whereas C2 and R2 assessed the images as if they were in a clinic or reporting session, grading the faecal loading as mild, moderate, or severe.

Results

One hundred patients were recruited out of 186 presenting in a 2-year period. All patients completed assessments. The correlation between observers was only fair to moderate (r ranging from 0.34–0.51). There were some surprisingly marked disagreements in 10–18% of assessments. The correlation between faecal loading and transit was weak for all observers (r ranging from 0.261–0.311). Symptom severity did not correlate with faecal loading.

Conclusion

These results suggest that there is considerable inter-observer variation in the radiological assessment of faecal loading, irrespective of the training or method used by the observer, and that there is very poor correlation with colonic transit. The diagnosis of constipation, and the assessment of severity, is best performed clinically.

Introduction

The use of a plain abdominal radiograph (AXR) to assess colonic faecal loading, and thereby diagnose constipation, is commonplace in clinical practice, but has never been validated. There have been a number of attempts to develop scoring systems for faecal loading in paediatric practice1, 2, 3 with some assessment of inter-observer and intra-observer variability. However, even this basic assessment has not been performed in adults. Furthermore, the validity of the test as a meaningful determinant of constipation requires assessment against a reference standard, which would ideally be the contemporaneous assessment of intestinal transit.

Scintigraphy or radio-opaque marker studies can be used to assess colonic transit. Scintigraphy requires the use of specialist equipment and radiopharmaceuticals often only available in specialist units. Measurement of colonic transit time by ingestion of radio-opaque markers assessed on a plain AXR is validated and produces results that are reproducible, and can differentiate between constipated patients and normal controls.4, 5 One recognized method involves the ingestion of markers on 3 consecutive days with an AXR taken on the 4th day.⁶

As the assessment of faecal loading is a subjective process, it has not been possible to assess this on transit films without potential bias from the presence of the radio-opaque markers. The aim of this study was to utilize recent developments of digital image capture and image processing to carefully remove transit markers from transit AXRs and thus allow, for the first time, a blinded comparison of faecal loading against a reference standard measurement of colonic transit.

Section snippets

Study group

Over a 2-year period, consecutive new referrals to the Durham Constipation Clinic were invited to participate. Patients fulfilling Rome II criteria for chronic constipation⁷ were selected. The criteria require two or more of the following over a minimum 12-week period: straining at least 25% of the time, hard stools at least 25% of the time, incomplete evacuation at least 25% of the time, and two or fewer bowel movements per week, in the absence of an organic cause for constipation.

Results

One hundred (age range 20–75 years; mean 43 years; six males, 94 females) of the 186 consecutive patients attending the clinic were recruited and all underwent the assessments. There was a wide range of severity of constipation exhibited, both in terms of transit times and symptom scores. Symptom scores exhibited a normal distribution with a range of 0–3.75 (possible range 0–4) and a mean score of 2 (SD 0.78). Transit times ranged from 2–72 h (possible range 0–72) and were positively skewed,

Discussion

The use of plain AXRs to assess faecal loading and infer a diagnosis of constipation is commonplace but unvalidated. The results of the present study suggest that assessment of faecal loading on AXR involves a degree of observer-based subjectivity, and does not correlate well with colonic transit. A premise for using a plain abdominal AXR to diagnose constipation is that there should be agreement between observers evaluating the same plain film. This is the first study to assess inter-observer

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Radiological assessment of constipation
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Citation Excerpt :
This practice may be prudent. The radiographic degree of fecal loading does not correlate well with constipation symptoms or stool colonic transit time, [7] bolstering the case that physician judgment should supersede radiographic findings. Furthermore, interrater agreement of fecal loading on radiography is poor to fair, even when formal rating scales are used [7-9].
Abdominal radiographs are often obtained in ED patients with suspected constipation, although their utility in adults is not well understood. We sought to compare ED management when an abdominal radiograph is and is not obtained.
We performed a retrospective chart review study of adult ED patients with a chief complaint of constipation from 2010 through 2016. Trained abstractors recorded radiologic tests ordered, treatments received, and final diagnosis. We determined the physician interpretation of the abdominal radiograph and its use in clinical decision making.
Of 1142 eligible patients, 481 (42%) patients underwent abdominal radiography. Stool burden rated moderate or large was observed in 271 patients (46%). Sixteen patients (3%) were diagnosed with small bowel obstruction; 15/16 of these patients had high risk features such as old age, complex surgical history, history of small bowel obstruction, abdominal malignancy, or presented with vomiting or inability to pass flatus. Of the 197 patients with no or mild stool burden or normal radiograph, 109 (55%) were diagnosed with constipation and 89 (45%) received constipation treatment in the ED. Conversely, of the 271 patients with moderate or greater stool burden, 114 (42%) received no treatment for constipation in the ED and 104 (38%) were prescribed no discharge medications for constipation; 77 of these 271 patients (28%) were diagnosed with something other than constipation.
Plain abdominal radiography did not appear to significantly affect the ED management of patients presenting with constipation; it was common for patients to receive treatment that was in direct opposition to radiographic findings. Though a small number of patients had concerning diagnoses identified on plain radiography, the history and physical examination should have sufficiently excluded simple constipation, prompting an alternate diagnostic approach. Fecal loading on radiography does not preclude a more serious diagnosis. In conclusion, abdominal radiography appears to have low value in patients with constipation.
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Our results are in line with previous studies. Thus, a study by Cowlam et al., found no association between symptom severity (overall PAC-SYM score) and total GI transit time in patients with chronic constipation (Cowlam et al., 2008). Additionally, another study found only a poor correlation of subjective constipation symptoms, assessed by the Cleveland Constipation Score and Rome Criteria III, and colonic transit time (Knudsen et al., 2017).
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Twenty-five healthy male participants were enrolled in a randomized, double-blinded, placebo-controlled, five-day crossover study with the treatments oxycodone and placebo. Objective measures of GI transit times and colonic volumes were obtained by the means of the 3D-Transit System and magnetic resonance colonography, whereas subjective GI symptoms were measures via three validated questionnaires. The symptoms were then categorized into five groups; “abdominal symptoms”, “defecation difficulties”, “incomplete bowel evacuation”, “reduced bowel movement frequency”, and “stool symptoms”. Spearman's rank order correlation was used to determine correlations between the five groups of symptoms and the objective measures.
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View full text

Blinded comparison of faecal loading on plain radiography versus radio-opaque marker transit studies in the assessment of constipation

Aim

Methods

Results

Conclusion

Introduction

Section snippets

Study group

Results

Discussion

Gastroenterology

Chronic and occult stool retention: a clinical tool for its evaluation in school-aged children

Clin Pediatr (Phila)

Evaluation of a method of assessing faecal loading on plain abdominal radiographs in children

Pediatr Radiol

Radiological assessment of constipation

Arch Dis Childhood

How well does stool form reflect colonic transit?

Gut

What is the meaning of colorectal transit time measurement?

Dis Colon Rectum