Understanding Functional Abdominal Distention

A recent study (Barba E, et al. Gastroenterol 2015; 148: 732-9) provides insight into why some patients develop functional abdominal distention.

In this prospective study of 45 patients (42 women), the researchers performed numerous tests to determine the reasons for abdominal distention.  Most patients had CT scan (n=39), and electromyography (EMG) of the abominothoracic wall (n=32) both at baseline and during distention. In addition, 15 patients underwent EMG-guided biofeedback.

Findings:

  • Abdominal distention was associated with diaphragm contraction (~19% increase from baseline) and intercostal contraction (~14% increase from baseline).
  • There was an increase in thoracic antero-posterior diameter compared with basal values with increase in anterior abdominal wall protrusion.
  • Biofeedback treatment was effective in reversing these changes.  This indicates that the distention is under voluntary control.

The authors use the term for the changes that cause the abdominal distention as “abdominal accommodation.”  They note that “in healthy subjects, an increase in intra-abdominal contents induces relaxation and ascent of the diaphragm, which permits cephalic expansion of the abdominal cavity with minor protrusion of the anterior wall.” In this study, the distention was determined in real-life settings to be due to “a paradoxical contraction of the diaphragm, that pushed abdominal contents downward, and relaxation of the anterior abdominal wall.”

Bottomline: These experiments provide a ‘proof-of-concept’ regarding the mechanisms of abdominal distention, though these experiments are not practical for most patients with these symptoms.

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