Ultrasound of the Week: Obstipation
Author: Hannah Seyller, MS4
Edited by Christopher Parker, DO, & Molly Hartrich, MD
A 72-year-old man with metastatic rectal cancer, currently receiving chemotherapy, presents to the emergency department with obstipation and abdominal pain. His last bowel movement was three days ago, and he has not been passing flatus. He has had a decreased appetite and pain localized to his upper abdomen. Before presenting to the ED, he had one episode of non-bloody, non-bilious emesis. On examination, his vital signs are within normal limits. The patient's abdomen is distended but there is no tenderness to palpation, rebound, or guarding.
Point-of-care ultrasound is performed in the ED.
What findings are seen in this patient's ultrasound images below? What is the diagnosis?
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These images demonstrate the key POCUS findings seen in patients with small bowel obstruction, including bowel dilation greater than 2.5 cm, "to-and-from" peristalsis, keyboard sign, and tanga sign (Figure 2).
Figure 2. Bedside ultrasound with limited abdominal views showing findings consistent with small bowel obstruction, including dilated bowel loops (lines), tanga sign (arrowhead), "to-and-fro" peristalsis (arrow), and keyboard sign (bracket).
PEARLS & CASE CONCLUSION
SBOs account for two percent of ED visits with a chief complaint of abdominal pain. Properly identifying these patients in the ED is important because delay in diagnosis and management is associated with increased risk for bowel resection.3 Adhesions are the most common cause of SBO. SBO related to malignancy (termed malignant bowel obstruction) is estimated to occur in two percent of all patients with advanced malignancy and in 10-28.4% of patients with colorectal cancer.4 SBO should be suspected in patients with previous abdominal surgeries and/or previous or current malignancy who report constipation, obstipation, and/or abdominal distention.5
POCUS can be used to evaluate for SBO by looking for bowel dilation, altered peristalsis, keyboard sign, and tanga sign (Figure 2). Bowel dilation >2.5 cm is generally regarded as the most valuable POCUS finding in SBO evaluation, with a sensitivity of 91-98% and specificity of 84-100%.6,7,8 "To-and-fro" peristalsis refers to dysfunctional or bidirectional movement of bowel contents.7 The keyboard sign refers to visualization of plicae circulares on the bowel walls. The tanga sign describes the triangular shape that is sometimes created when there is free fluid visualized between loops of bowel.2 A common issue that arises when using POCUS for SBO evaluation is view obstruction due to bowel gas. If this occurs, graded compression can be used to displace intraluminal air, or the ultrasound probe can be moved to a lateral limited abdominal view.3
POCUS has a sensitivity of 94-100% and specificity of 81-100% for diagnosing SBO.1,3,9 Bedside ultrasound is superior to plain films and comparable to computer tomography scan, which is currently regarded as the gold standard for SBO diagnosis.3,6,7,10 Studies show that emergency providers with minimal ultrasound training can reliably detect SBO using POCUS,1,11 making it a valuable tool in the ED work-up of abdominal pain.
The patient underwent CT imaging, which confirmed a complete SBO. He received analgesia and intravenous fluid resuscitation. General surgery was consulted, a nasogastric tube was placed, and the patient was admitted for continued management.