Mechanical Small-Bowel Obstruction

May 1, 2008
Eva Ilse Rubio, MD

An otherwise healthy 9-month-old girl was brought to the emergency department (ED) by her parents who reported a 12-hour history of nonbloody, nonbilious emesis. The patient had a mildly increased temperature and appeared to be dehydrated.

An otherwise healthy 9-month-old girl was brought to the emergency department (ED) by her parents who reported a 12-hour history of nonbloody, nonbilious emesis. The patient had a mildly increased temperature and appeared to be dehydrated.

These radiographs were obtained approximately 48 hours after the girl's initial presentation to the ED (Figure 1).

Figure 1 - These are supine and lateral decubitus views of the abdomen of a 9-month-old child who presented with a 12-hour history of nonbloody, nonbilious emesis.

1. What is your interpretation of these images?


A. Mid to distal large-bowel obstruction, with incidentally noted foreign bodies.
B. Small-bowel obstruction, with perforation, with incidentally noted foreign bodies.
C. Small-bowel obstruction, with suspicious foreign bodies.
D. Colonic obstruction, with metallic decorations of the patient's clothing projecting over the abdomen.

2. What imaging study would you request next?


A. CT scan, to determine the location of the foreign bodies.
B. Ultrasonography, to determine the cause of the bowel obstruction.
C. No further imaging is needed.



3. What is your impression of the bones?


A. The bones are normal.
B. There is evidence suggesting nonaccidental trauma.
C. There is evidence of chronic lead ingestion.



Answers & Discussion

1. What is your interpretation of these images? (C is the correct choice.)


These films show 3 loops of distended bowel in the midabdomen. The central location of the loops and their wall contour leave us fairly certain that these are loops of small bowel rather than colon. In particular, note the "stack of coins" appearance of the most superiorly located loop of bowel-a typical appearance for jejunum (Figure 2A). There is a small amount of air in the stomach and a very small amount of air and stool in the rectum (Figure 2B).

Figure 2 - The "stack of coins" appearance of the most superiorly located loop of bowel is a typical appearance for jejunum (A). Image B is a close-up view of jejunum; it shows a small amount of air in the stomach and a very small amount of air and stool in the rectum. These findings can be interpreted as a highgrade or complete mechanical small-bowel obstruction.

Without hesitation, I would call this a high-grade or complete mechanical small-bowel obstruction.

To evaluate for free air, it is helpful to have some sort of additional horizontal x-ray beam study. This means an upright, decubitus, or cross-table lateral radiograph to see where free air rises to the highest point of the peritoneal cavity. In this patient's case, the images do not clearly demonstrate free intraperitoneal air. A few modest air bubbles are seen in the right upper quadrant by the inferior tip of the liver (Figure 3) on the decubitus view. These most likely reside within the hepatic flexure of the colon, because free intraperitoneal air often has a more crescentic contour. Figure 4 provides a good example of the typical crescentic contour of pneumoperitoneum.

Figure 3 - A few air bubbles are seen in the right upper quadrant by the inferior tip of the liver on the decubitus view. These most likely reside within the hepatic flexure of the colon, because free intraperitoneal air often has a more crescentic contour.

Figure 4 - A decubitus view in another patient demonstrates the typical crescentic contour of pneumoperitoneum.

Let's turn our attention to the clustered metallic densities that project over the midabdomen. It is interesting (and relevant) that the clumped objects shift slightly as a group when the patient changes from the supine to the decubitus position. However, the objects themselves retain the same orientation to each other from one image to the next. If you have already concluded that these objects are inside the patient and not in a pocket of the patient's clothing, then this restricted motion of the objects becomes more suspect-particularly in the setting of a small-bowel obstruction. We now know that the metallic objects are within the abdomen, but they are not coursing through the bowel and heading for freedom from below. They are stuck.

2. What imaging study would you order next? (C is the correct choice.)

Additional imaging is not needed, will add no further information that will affect the patient's immediate treatment, and will only delay her inevitable trip to the operating room. The bowel is obstructed and the multiple ingested metallic foreign bodies that remain stubbornly clumped together are magnets. Magnets that reside in neighboring loops of bowel are still attracted to each other. The soft, thin loops of bowel that are trapped between the magnets suffer pressure necrosis and frank perforation. These magnets will not pass on their own, and surgery is the only solution.

Intraoperatively, 6 magnets and 1 watch battery were found in this child. There was a significant amount of turbid fluid within the peritoneal cavity, several areas of perforation, and a small-bowel to small-bowel fistula. A small segment of small bowel was resected.

The child recovered quickly and was discharged on the fourth postoperative day.

3. What is your impression of the bones? (A is the correct choice.)

The bones are normal, as are the inferior cardiac silhouette and the visualized lung bases-other important things to look at on any abdominal radiograph. The child's bones demonstrate appropriate mineralization and developmental stage.

Findings of lead ingestion-not seen here-would include bright flecks within the stomach or bowel and, in a chronic setting, may result in the finding of dense metaphyseal bands. (The latter has its own differential list that is beyond the scope of this discussion.) Bright flecks within the bowel are a nonspecific finding and may be seen after ingestion of vitamins, medications, and even some candies. Even a hard, long-standing stool ball may start to develop a mildly dense appearance. There is no evidence here to suggest heavy metal ingestion, however.