P3.M253: Does BMI Play a Role in Diagnosing Tubo-Ovarian Abscess?

Background: Tubo-ovarian abscess (TOA) is a known complication of pelvic inflammatory disease characterized by an inflammatory mass of the fallopian tube, ovary, and/or other adjacent pelvic organs, and early diagnosis prevents complications. Although laparoscopy is the gold standard to diagnose TOA, ultrasound (US) is the diagnostic imaging modality preferred as it lacks ionizing radiation, is non-invasive, and has an accuracy of diagnosis with reported sensitivity 56-93% and specificity 86-98%. While US evaluation of appendicitis in children with obesity has shown decreased sensitivity compared to age matched peers; to our knowledge, no studies exist at examining the relationship between obesity and US sensitivity in diagnosing TOA. The study aimed to investigate if higher BMI patients diagnosed with TOA had a significant rate of false-negative US. We secondarily evaluated if the false-negative study was a transabdominal or transvaginal US.

Methods: This retrospective chart review study analyzed patients’ charts from 1/1/2018 to 12/31/2022 with the diagnosis of TOA in the Pediatric and Adult ED. Inclusion criteria included patients with at least one of the following imaging modalities: abdominal US, transvaginal US, or CT abdomen and pelvis. Patients without imaging were excluded. A patient was classified as positive for TOA if they had one positive imaging modality and received TOA treatment. A false-negative study was identified when one imaging modality was negative while another was positive for TOA, and the patient was treated for TOA. There were no false-positive studies as all patients received treatment for TOA. Patients were classified by their BMI as underweight, healthy, overweight, or obese.

Results: Of the 560 charts reviewed, 219 met inclusion criteria and of those, 54 were TOA positive patients. The average age in the positive group was 33.4 (SD 14.3). In the underweight and healthy groups, the sensitivity and negative predictive value of US diagnosing TOA were 100%. In the overweight group the sensitivity and negative predictive value of US was 85.7% and 96.3% respectively. The overweight group had one false-negative transabdominal US. In the obese group the sensitivity and negative predictive value of US decreased to 53.9% and 89.5% respectively. The obese group had four patients with false-negative US; two transvaginal and two with both US studies. Additionally, each overweight and obese group had one false-negative CT. In total, there were seven false-negative patients in the overweight and obese groups combined, and none in the normal or underweight group, with a statistical difference of p-value 0.0162.

Conclusion: This study highlights a statistically significant number of false-negative imaging studies in patients classified as overweight and obese with TOA diagnosis, the majority of which were US studies. Although further studies are needed to delineate optimal imaging, vigilance is needed in patients with high BMI, as imaging modalities may be inaccurate.