Small bowel obstruction (SBO) accounts for 2% of all cases of abdominal pain presenting to the ED and 15% of abdominal pain admissions to surgical units from the ED.1,2 SBO can be a difficult diagnosis; the most common symptoms include nausea, vomiting, abdominal pain, obstipation, and constipation. The symptomatology depends on multiple factors: the area of the blockage, length of obstruction, and degree of the obstruction (either partial or complete).3 An upper gastrointestinal (GI) blockage classically presents with nausea and vomiting, while a lower GI blockage often presents with abdominal pain, constipation, and obstipation. Complications of obstruction range from significant morbidity—such as bowel strangulation (23%) and sepsis (31%)—to mortality (9%).4 ED POCUS allows for rapid and accurate diagnosis of SBO.
CASE
A 60-year-old female with a past medical history of peptic ulcer disease and multiple abdominal surgeries, including umbilical hernia repair, appendectomy, and total abdominal hysterectomy, presented to the ED with an 8-hour history of nausea and vomiting. She reported that her abdomen felt bloated. She had experienced non-bloody, watery stools for the prior 3 weeks. She also reported three to four weeks of epigastric abdominal pain similar to her previous “ulcer pain.” Of note, she was evaluated in GI clinic one day prior to her ED visit for dysphagia, abdominal distention, and diarrhea and was scheduled for an outpatient upper endoscopy. Initial vitals were significant for a heart rate of 100 beats/min. Physical exam was significant for a mildly distended abdomen, tender to palpation at epigastrium without rebound or guarding. Labs showed a white blood cell count of 11.8 K/uL and otherwise unremarkable complete blood count, basic metabolic panel, liver function tests, and lactate measurement. Given the patient’s history of multiple abdominal surgeries and clinical presentation, POCUS was performed to evaluate for SBO. Dilated loops of small bowel were visualized in the lower abdomen gas, suggestive of SBO.
Since the small bowel encompasses a large portion of the abdomen, to fully evaluate for SBO, multiple views are necessary. These include the epigastrium, bilateral colic gutters, and suprapubic regions.5 Use the low-frequency curvilinear transducer to obtain these views, scanning in the transverse and sagittal planes (see Figures 1 and 2). Scan while moving the transducer in columns (ie, “mowing the lawn”), making sure to cover the entire abdomen. To assure that you are evaluating the small bowel, and not the large bowel, look for the characteristic plicae circularis of the small bowel (shown in Figure 3). In children and very slender adults, the high-frequency linear probe may provide enough depth to obtain adequate views.
Figures 1 and 2. POCUS scan pattern for SBO, known as “mowing the lawn.” Probe marker is to the patient’s right above in the transverse plane and to the patient’s head below in the sagittal plane.
Figure 3 - Dilated loops of small bowel with characteristic plicae circularis (white arrows).