Intravenous fluids were started and dilaudid was given for pain control.  An obstructive series was read as a bowel obstruction without evidence of free intra-peritoneal air.  Following the results of the obstructive series, the surgical service was consulted for admission to the hospital.  The surgeon on call requested, by phone, a CT scan of the abdomen and pelvis.  A naso-gastric tube was inserted and approximately 800 ml. of oral CT contrast solution was infused into the stomach over approximately one-half hour, after which the tube was clamped to prevent siphoning of the solution.  The CT scan was done about an hour after the end of the infusion. 

While having the CT of the abdomen and pelvis, the patient began gurgling and vomited.  The patient was turned and physicians were called.  This required one of the two attendants to leave the patient’s bedside.  On the physicians’ assessment, the patient was poorly responsive.  When the pulse ox monitor became available, the oxygen saturation was about 85%.  The resuscitation was done, with the help of suction that had been brought into the room.  A follow-up chest radiograph showed bilateral lower lobe infiltrates.  The clinical diagnosis was aspiration of gastric contents into the lungs with hypoxia.

Vomiting and aspirating are not per se patient safety events.  However, for a patient at risk for vomiting and aspirating, prevention and/or mitigation of at least the aspiration should be part of safe medical care.  This patient had three commonly accepted indicators for being at greater than normal risk for aspiration of emesis: bowel obstruction with a full stomach, sedation from narcotics, and confinement in the supine position (during the CT scan).  Facilities should be prepared to identify and respond to patients at risk for aspiration because of vomiting (or other risk factors, such as bleeding into the airway).  For instance, if endotracheal intubation or monitoring or nursing accompaniment is not appropriate for an individual patient getting a CT scan with oral contrast, it might still be appropriate to:

1. Have a video monitor, as many CT scan rooms do, to display in the control room the parts of the patient not directly visible to the CT tech.
2. Have an emergency button available to providers within reach of the patient’s head.
3. Have suction constantly available in the room near the CT scanner.
4. Train the CT technicians to identify and do emergency treatment for aspiration.

Of particular interest in this report is the “routine” use of oral contrast for a diagnostic CT scan of the abdomen and pelvis in a patient with prior clinical and radiographic diagnosis of bowel obstruction. 

The American College of Radiology Committee on Appropriateness convened an Expert Panel on Gastrointestinal Imaging that developed Appropriate Criteria for Suspected Small Bowel Obstruction ¹.  The criteria for this clinical condition were revised in 2005.  The document is an excellent review of the subject that provides invaluable information to anyone considering imaging studies for such a patient. This guide states that “Patients with suspected high grade obstruction do not require additional oral contrast medium since the fluid in the bowel provides adequate contrast.”  On a scale of 1 (least) to 9 (most appropriate), the highest appropriate rating was given for CT of the abdomen and pelvis without oral contrast but with IV contrast (a rating of 8), followed by supine and upright abdominal x-ray (a rating of 7), then CT of the abdomen and pelvis with oral contrast and with IV contrast (a rating of 5).  (One of the benefits of the patient not having a clamped naso-gastric tube during the CT is that the gastro-esophageal sphincter is not held open in a supine patient with a full stomach.)  The literature, primarily from Indiana University, recommends that patients with signs of bowel obstruction on plain radiographs of the abdomen (air-fluid levels at differential heights in the same loop of bowel and mean air-fluid widths of at least 25 mm on upright abdominal radiographs) should not have oral contrast for clarifying CT scans of the abdomen and pelvis.^2,3

Facilities may wish to review their protocols for diagnostic imaging studies for patients with suspected small bowel obstruction in light of the recently revised Appropriateness Criteria from the American College of Radiology. They may also wish to review their ability to prevent and mitigate aspiration in all areas of their facilities where patients are at risk for this complication.

Notes

1. Ros PR, Huprich JE, Bree RL, et al. ACR appropriateness criteria: suspected small bowel obstruction. American College of Radiology [online.] 2005 Available from Internet: http://www.acr.org/SecondaryMainMenuCategories/quality_safety
   /app_criteria/pdf/ExpertPanelonGastrointestinalImaging
   /SuspectedSmallBowelObstructionDoc15.aspx
2. Lappas JC, Reyes BL, Maglinte DDT.  Abdominal radiographic findings in small-bowel obstruction: relevance to triage for additional diagnostic testing. AJR 2001;176:167-74.
3. Maglinte DDT, et al. The role of radiology in the diagnosis of small-bowel obstruction. AJR 1997;168:1171-80.

Self-Assessment Questions

The following questions about this article may be useful for internal education and assessment. You may use the following examples or come up with your own.

1. According to the American College of Radiology, the generally most appropriate imaging study for patients with suspected high grade small bowel obstruction is:
1. CT of the abdomen and pelvis with oral and IV contrast
2. supine and upright abdominal x-ray
3. CT of the abdomen and pelvis without oral contrast but with IV contrast
4. MRI of the abdomen
5. ultrasound of the abdomen
2. A radiographic finding strongly associated with a high grade obstruction of the small bowel is:
1. gas or feces in the colon
2. a mean air-fluid level width greater than 25 mm on upright radiographs
3. cecal width greater than 20 mm
4. gastric distension (in the absence of a nasogastric tube)
5. fluid in the cecum