Ultrasound Visceral Slide Assessment to Evaluate for Intra-abdominal Adhesions in Patients Undergoing Abdominal Surgery - A Systematic Review and Meta-analysis

Abdominal entry at the time of laparoscopy is a critical step with a risk of injury to underlying viscera owing to bowel adhesions. Ultrasound can be used as a preoperative tool to assess the slide of viscera underneath the abdominal wall to detect adhesion-free areas. The objective of this systematic review and meta-analysis was to determine the diagnostic accuracy of preoperative visceral slide assessment with ultrasound to detect intra-abdominal adhesions, compared with the gold standard of intraoperative findings. Using Cochrane, Medline PubMed, Embase, and Google Scholar electronic databases, 3737 articles were screened in April 2020 using a query that included variations of "adhesions" and "ultrasound." Reference lists of relevant articles were searched for further articles. Prospective and cross-sectional studies in English that included patients at risk for intra-abdominal adhesions who underwent preoperative ultrasound visceral slide assessment and subsequent intraoperative assessment of adhesions were selected. Two reviewers independently selected 25 articles, extracted data, and assessed bias using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Twenty-five articles reported on 1609 patients and 5812 assessed abdominal areas, with considerable heterogeneity of described abdominal areas and degrees of adhesions. Meta-analysis was performed for 21 studies. The periumbilical area was assessed specifically for bowel adhesions in 890 patients in 12 studies, with a 12.0% bowel adhesion rate. Ultrasound assessment for periumbilical bowel adhesions had a combined sensitivity of 95.9% (95% confidence interval, 82.7%-99.1%), specificity of 93.1% (85.1%-96.9%), positive predictive value of 60.4% (44.2%-74.7%), and negative predictive value of 99.2% (97.9%-99.7%) with low heterogeneity (I2 = 16%). Visceral slide assessment with ultrasound has a high negative predictive value for the absence of periumbilical bowel adhesions in patients at risk for adhesions and can function as a useful tool to detect adhesion-free areas to allow for safe laparoscopic entry.