ACR Codes: 7.-1
In systemic sclerosis there is patchy deposition of excessive collagen in many parts of the body with the small intestine involved in about half the cases. Replacement of muscle bundles leads to dilatation and stasis. Longitudinal muscle fibers tend to be predominantly replaced, resulting in restriction of elongation without resistance to dilatation. This is the explanation given for the pathognomonic radiologic "hide bound" bowel sign which is found in over 60% of patients in whom systemic sclerosis affects the small bowel. Sacculation of the antimesenteric border of dilated small bowel loops is an infrequent finding, being more commonly seen when systemic sclerosis affects the colon.
The duodenum is the most frequently involved portion of the small bowel, second in the gastrointestinal tract only to the esophagus. Skin changes are usually present by this time, sclerodactyly being the most obvious. Clinically evident malabsorption is an infrequent feature. If present it is due to stasis and bacterial overgrowth and/or to a collagen deposition associated vasculitis in the submucosa that further impairs absorption.
Differential diagnosis from other causes of pseudo-obstruction becomes a problem only in cases where the hide bound bowel sign is absent and skin changes of scleroderma are not yet established. Other collagen diseases like lupus erythematosus or dermatomyositis, amyloidosis, endocrine disorders (hypothyroidism, diabetes), neurologic disorders, administration of certain drugs and an idiopathic subgroup of pseudo-obstruction have then to be considered in the differential diagnosis. The patient's history, and the pattern of changes in other organs like lungs, joints or kidneys, may be of diagnostic help.
FURTHER CASE EXAMPLES: Film .2, a plain film in a patient with abdominal distention, demonstrates considerably dilated loops of small bowel; is this a case of pseudo-obstruction or mechanical obstruction? One of the dilated bowel segments (arrows) shows crowding of straight folds, a feature that points away from mechanical obstruction. Film .3 is an overview of a small bowel enema done immediately after the plain film. Dilated small bowel loops are outlined with barium and show that folds are either crowded or of normal number per unit length; in the segment that was arrowed on the plain Film .2, there are now shown to be 5-6 folds per inch of length at a lumen diameter of 8.5 cm (arrow). This finding of a normal number of folds over 1 inch is not expected in conditions where lumen dilatation would be accompanied by elongation and an increased separation of folds, like mechanical obstruction or idiopathic pseudo-obstruction. Diagnosis: Systemic sclerosis with positive hide bound bowel sign shown as a normal number of folds in a dilated segment.
In another patient with systemic sclerosis involving the small bowel, the duodenum is predominantly affected. Film .4, a delayed spot film in a small bowel meal, shows an empty jejunum and barium well advanced into the colon while still opacifying the dilated and flaccid duodenum (arrows).
A film of a small bowel enema (Film .5) in a patient in whom malabsorption was part of the clinical presentation of systemic sclerosis, demonstrates not only lumen dilatation, now of the ileum, but also a mild degree of sacculation (arrows) of its antimesenteric border.
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Disease Topic 1723 
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