(114) Ultrasound assessment of upper abdominal free fluid after uncomplicated cesarean delivery

Objective: Ultrasound measurement of upper abdominal fluid is commonly used to assess for intraabdominal bleeding after trauma, but it has not been studied after cesarean delivery. We sought to define normal measurements after scheduled cesarean delivery.

Study Design: After IRB approval, a prospective cohort of patients undergoing scheduled cesarean delivery was recruited. Ultrasound measurements of fluid in the hepatorenal (RUQ) and splenorenal (LUQ) fossa in were taken in supine position immediately after surgery and repeated on postoperative day #1. Information on medical history, prenatal care, and postoperative course were abstracted from the medical record.  Continuous variables were compared with t-test and categorical compared with chi squared.

Results: 42 patients without concern for postoperative complication were included. The immediate postoperative RUQ and LUQ measurements were mean (SD [standard deviation]) 1.2 (1.8) mm and 1.3 (1.4) mm, 90^th percentile 2.9 mm and 3.8 mm, and no measurable fluid in 48% and 45% respectively. On postoperative day #1 the RUQ and LUQ measurements were mean (SD) 1.6 (1.2) mm and 1.0 (1.3) mm, 90^th percentile 3.5 mm and 3.7 mm, and no measurable fluid in 44% and 53%. Measurements were not obtained due to patient discomfort in 0 to 9.5% of cases. Change from initial to day #1 measurements were calculated, and the 90th percentiles were RUQ 2.0 mm and LUQ 2.2 mm. On postoperative day #1, 28.6% of patients had a composite of at least one measurement or change in a measurement greater than the 90^th percentile (table 1). This composite outcome was associated with repeat cesarean (p=.03) and with increased operative time (37 vs 53 minutes, mean difference 15.3 minutes [95% CI 5.8, 24.8], p=.002), but was not otherwise associated with maternal or surgical characteristics.

Conclusion: Measurements of fluid in the RUQ and LUQ were easily obtained and well tolerated after routine cesarean delivery, and our data show that finding more than 3.8 mm of fluid is abnormal and may help diagnose intraabdominal bleeding as it does after trauma.