Welcome to the Abdominal Imaging Section of Radiology Daily.

In the Abdominal Imaging section, we will be keeping you up to date on the latest information in the field of Abdominal Imaging, including abdominal ultrasound, colonoscopy, virtual colonoscopy, use of multiplanar reformations (MPRs) for abdomen and pelvis, MDCT, helical (single and multidetector-row) CT and MRI, CT/MR angiography, and CT cholangiography.

We will also include news on the current clinical challenges in abdominal imaging, including interpreting imaging studies, and how to choose and use the various imaging technologies in the hope of better patient outcomes.

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The objective of a recent study was to determine whether a new method of ultrasound assessment of stool retention could be used as a method of identifying children with functional chronic constipation.

The prospective study has concluded that ultrasound assessment of stool retention in children with functional chronic constipation has a high correlation with proctoscopic examination and colonic transit time.

Methodology
120 children with a diagnosis of constipation based on patient history and physical examination were recruited for this study. Chronic disease was defined as symptoms that had persisted for >6 months. The control group was comprised of 105 children with a normal defecation pattern who were diagnosed and treated for various symptoms.

Children with diagnosed constipation were examined first by ultrasound, followed by digital rectal examination, enema, proctoscopy, and ultrasound again. Ultrasound was used to measure the transverse diameter of the rectal ampulla and to measure the pelvic width (performed externally using a measuring tape). Pelvic width was defined as the distance between the external margins of the anterior superior iliac spines.

The recto pelvic ratio was determined by calculating the ratio between the transverse diameter of the rectal ampulla and the transverse diameter of the pelvis.

Other features assessed by ultrasound were rectal ampulla width, rectal ampulla filling, bowel filling at splenic flexure, and transverse colon filling.

Children who were diagnosed with megarectum, enlarged colon, and fecal impaction were referred for proctoscopy and measurement of colonic transit time.

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Results of the Study
Compared to controls, children with constipation experienced fecal impaction and overfilling of the splenic flexure significantly more often. The mean recto pelvic ratios were statistically significantly higher in the children diagnosed with chronic constipation than in the controls.

The greatest discrepancy was for children aged < =3 years who had an average recto pelvic ratio of 0.24, with the control group averaging 0.17. Those between 3 and 6 years of age also had markedly increased recto pelvic ratios compared to controls (0.23 versus 0.16). Children with an overfilled transverse colon as seen on ultrasound had a significantly longer mean segmental transit time.

Overall, the sensitivity of the ultrasound method in the diagnosis of fecal impaction, as compared to proctoscopy, was 88.3%.

Conclusions
This new method for diagnosis of stool retention and megarectum by ultrasound yielded an adequate sensitivity when using proctoscopy as the standard. The recto pelvic ratio allows diagnosis of megarectum in children with functional chronic constipation, with a cut-off value of 0.189.

Reviewer’s Comments
The authors present a novel ultrasound approach to assessing the child diagnosed with chronic constipation. By using the ratio of the rectal ampulla transverse diameter to the transverse diameter of the pelvis, a useful ratio was created that normalized the results.

It remains to be determined which children would benefit from this technique, although I would assume that follow-up examinations to evaluate for patient response to treatment might be one use.

Author: Basil Hubbi, MD

Reference
Bijos A, Czerwionka-Szaflarska M, et al. The Usefulness of Ultrasound Examination of the Bowel as a Method of Assessment of Functional Chronic Constipation in Children. Pediatr Radiol; 2007; 37 (December): 1247-1252:

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Tags: Chronic constipation, ultrasound