What is the false negative rate for Computed Tomography (CT) scans with oral contrast in detecting gastrointestinal leaks?

From the Guidelines

The false negative rate for CT with oral contrast in detecting a leak is approximately 72%, as reported by Alharbi et al. [@49@], indicating a significant limitation in the sensitivity of this imaging modality for this specific purpose. This high false negative rate suggests that CT with oral contrast may not be reliable enough to rule out a leak, particularly in post-sleeve gastrectomy patients. Several factors can contribute to this high false negative rate, including the size and location of the leak, the timing of the scan relative to the leak occurrence, and the volume and type of contrast used. In cases where clinical suspicion for a leak remains high despite a negative initial CT, additional imaging modalities such as fluoroscopy or repeat CT scanning may be warranted. The experience of the radiologist interpreting the images also plays a significant role in accurately identifying subtle signs of leakage. Key findings that may indicate a leak on CT include perigastric fluid collection, variable wall enhancement, and extra-luminal gas, as these indirect signs are more commonly observed than direct evidence of a leak, such as oral contrast extravasation [@49@]. Given the potential consequences of a missed leak, including severe morbidity and mortality, a low threshold for further investigation or surgical exploration should be maintained, even in the face of a negative CT scan with oral contrast. It is essential to consider the clinical context and to weigh the benefits of additional imaging or surgical intervention against the risks, particularly in patients with a history of bariatric surgery who present with symptoms suggestive of a leak. The use of other imaging modalities, such as ultrasound or MRI, may also be considered, especially in pregnant patients where minimizing radiation exposure is a priority [@50@, @51@, @52@, @53@, @54@, @55@]. Ultimately, the management of suspected leaks in patients with a history of bariatric surgery requires a multidisciplinary approach, incorporating clinical judgment, imaging findings, and surgical expertise to optimize patient outcomes.

From the Research

False Negative Rate for CT with Oral Contrast in Finding a Leak

• The false negative rate for CT with oral contrast in finding a leak is not directly addressed in the provided studies.
• However, study 1 discusses the diagnostic value of CT scans with oral contrast in detecting anastomotic leaks after esophagectomy, and reports that the leakage of contrast and/or presence of mediastinal gas had a negative predictive value of 95.8%.
• Study 2 evaluates the diagnostic accuracy of contrast-enema computed tomography (CECT) in detecting anastomotic leakage after colorectal surgery, and reports a pooled sensitivity of 0.89 and specificity of 1.00 for CECT.
• Studies 3, 4, and 5 do not provide relevant information on the false negative rate for CT with oral contrast in finding a leak.

Relevant Findings

• Study 1 suggests that CT scans with oral contrast can be useful in detecting anastomotic leaks, but may have a low diagnostic value in the early postoperative period.
• Study 2 highlights the high diagnostic accuracy of CECT in detecting anastomotic leakage, but does not provide information on the false negative rate.
• The false negative rate for CT with oral contrast in finding a leak is not explicitly reported in the provided studies, and further research may be needed to determine this value.