You are called to the surgical floor to evaluate a 65-year-old female who underwent a right hemicolectomy for colon cancer four days prior. For the last few hours the patient has had multiple episodes of nausea with vomiting and has yet to have flatus or a bowel movement since her procedure. Her vital signs are normal, her abdominal exam is notable only for distension, and labs obtained earlier that morning are unremarkable. Of note, the patient is still requiring use of her morphine PCA for postoperative analgesia. You order a KUB, as seen in Figure 32-1.
Small bowel obstruction. Supine film showing dilated loops of small bowel and no gas in the colon. (Reproduced, with permission, from Doherty GM. Current Diagnosis & Treatment: Surgery. 13th ed. New York: McGraw-Hill; 2010. Figure 29-5.)
1. For this patient, name two key findings you should be looking for on the KUB.
2. How can you distinguish the small intestine from the colon on a KUB?
Reading and Using a KUB
Although they stand for kidneys, ureters, and bladder, KUBs are more commonly utilized to assess for abnormal conditions of the gastrointestinal tract and to determine the position of various indwelling devices, including NGTs, Dobhoff (feeding) tubes, and ureteral stents. In a patient such as this one, with a history of recent abdominal surgery and several bouts of nausea and vomiting, it is important to assess for the presence of obstruction or evidence of anastomotic breakdown (as indicated by the presence of free intraperitoneal air). A KUB is quick, relatively inexpensive, and has a lower radiation dose than CT, making it a common initial diagnostic study.
When encountering any type of film, including a KUB, it is important to take a systematic approach to interpretation. Doing so ensures that key findings pertinent to making appropriate decisions regarding a patient’s care are not missed. If previous films are available, it is helpful to compare the findings with those of the current study. After ensuring that you’re viewing the film for the correct patient, determine the orientation (right vs left as indicated by a marker or using the gastric air bubble in the LUQ as a guide). Also determine if you’re looking at a film that was obtained while the patient was supine versus erect as this will influence whether or not you’re able to visualize the presence of air–fluid levels and free air under the diaphragm. Keep in mind that on plain radiographs high-density structures (generally those that contain calcium such as bone, gallstones, and kidney stones) are white. Similarly, soft tissue and fluid are light gray, while gas is black.
After orienting yourself to the image, be sure to look for the presence of extraluminal ...