Dilated small bowel can occur either due to obstruction of the bowel or due to an ileus. Occaisionally the dilated bowel will contain fluid and is then difficult to visualise on plain radiographs. If the small bowel is obstructed distally multiple loops of distended bowel will be seen. if the obstruction is more proximal then less loops of bowel are seen. CT is often used to try to establish the cause and level of obstruction.
Diagnosis can be made by :
Abdominal radiograph
Computerised Tomography (CT)
What to look for (radiological findings) :
Multiple loops of dilated bowel. To differentiate between large and small bowel dilatation look for the following:
Large bowel :
Small bowel :
Bowel markings:
The bowel markings or folds do not fully cross the lumen of the bowel - the haustra
The bowel markings are often continuous across the bowel - the valvulae conniventes
Position :
Peripheral
Central
Size of bowel :
Can be become very distended up to 5 to 6 cm (the caecum can be distended up to 8 to 9 cm)
The small bowel can not become as distended as large bowel - up to 3 to 4 cm
This image shows dilated small bowel. The bowel markings or folds (valvulae conniventes) cross the lumen of the bowel.
annotate valvulae conniventes >>>
Discussion :
It is difficult to determine the cause of small bowel dilatation from a plain radiograph and difficult to establish if the dilated bowel is due to obstruction or ileus. If further imaging is needed a CT scan is used. Further imaging will help to determine the level of the obstruction and in the case of CT can give extra information about surrounding structures.
Causes of Obstructed Small Bowel :
Adhesions - the commonest cause.
Hernia
Gallstone ileus
Intussusception
Internal hernia
Tumour - arising from the bowel or extrinsic mass
Causes of an Ileus :
Postoperative
Intraabdominal infection or inflammation
Hypokalaemia
Anticholinergic drugs
