In what portions of the GI tract is normal gas located when the patient is radiographed in supine and prone positions?
Gas collects in nondependent portions of the GI tract. When the patient is lying in a supine position, the gastric antrum and transverse colon are the most anterior (nondependent) portions of the GI tract. An air-filled transverse colon less than 5 to 7 cm in diameter is a normal finding on a supine radiograph. When the patient lies in a prone position, the gastric fundus, ascending and descending colon, and midrectum are the most posterior (nondependent) portions of the GI tract.
