Kaplan USMLE Step 3: No bowel movement five days after kidney surgery

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.

A 61-year-old man undergoes a right radical nephrectomy for renal cell carcinoma. The procedure was performed via a flank incision over the 12th rib. The operation was contained within the retroperitoneum, and there was no evidence that the peritoneal cavity was entered during the procedure. Postoperatively, the patient's pain is managed with intravenous morphine sulfate that is infused through a patient-controlled analgesia (PCA) pump. The patient's initial postoperative course is uneventful. Within 48 hours of surgery, he is ambulating with assistance. Due to the painful nature of his flank incision, the patient utilizes a large quantity of morphine after surgery.

On postoperative day five, you are called to evaluate the patient after he vomited bilious material. Upon questioning, the patient states that he has not passed any flatus, nor has he had a bowel movement. He denies any chest pain or shortness of breath but refers some mild abdominal pain at the site of the incision. His temperature is 37.7ºC (99.9ºF), blood pressure is 137/62 mm Hg, pulse is 87/min, and respirations are 18/min. There are fine crackles over the right lung base.

Abdominal examination reveals a moderately distended abdomen and an incision that is clean, dry and mildly tender. Bowel sounds are hypoactive diffusely, and percussion displays tympanic sounds. He has no calf tenderness. His electrolytes are all within normal limits; however, his hemoglobin and hematocrit are 10.8 g/dL and 32%, respectively (preoperatively they were 13.1g/dL and 39%). An abdominal series shows dilated small and large bowel loops with air-fluid levels within the small bowel. There is no free air appreciated. What is the most appropriate next step in management?

A. Accept a blood transfusion

B. Begin eating solid food

C. Decrease the use of his PCA pump to the minimum dose

D. Force himself to vomit every six hours

E. Place patient on NPO status

F. Undergo a barium enema

The correct answer is E.

This patient is suffering from a prolonged postoperative ileus. An ileus is defined as the interval from the time of operation until the return of flatus and bowel movements. The expected time frame for return of bowel function varies with the operation performed. In a surgery such as nephrectomy, which is confined to the retroperitoneum, bowel function should return within 36-48 hours. The absence of bowel sounds, flatus or bowel movements beyond the expected period indicates delayed resolution or an adynamic ileus. This type of ileus usually responds to nonoperative intervention. It frequently requires intestinal decompression with the placement of a nasogastric tube. Diagnosis is made with a combination of history, physical and, if necessary, radiographic studies. The etiology of adynamic ileus is varied. Causes include neurogenic, metabolic, pharmacologic and infectious sources. It is important to "rule out" any of these which might be suspected. This patient's ileus is most likely from his increased use of narcotics. Conservative management by making the patient NPO and stopping his PCA should improve his condition.

Choice A. Although the patient's blood level is decreased from preoperative levels, he does not display any signs or symptoms of anemia (hypotension, tachycardia, fatigue, lightheadedness). Giving him a blood transfusion will not alleviate the ileus and will expose him to the risks associated with transfusion.