This patient presents with a story suggestive of ruptured ectopic pregnancy, yet the Morison’s Pouch view here demonstrates no free fluid. After repositioning the patient in trendelenburg, the following view is obtained:
The sensitivity of a Morison’s Pouch view for free fluid increases as the patient goes from lying supine to trendelenburg positioning.1
Often patients with hemoperitoneum have increased pain when they lie flat because of the stretching of abdominal musculature,2 so adequate pain control with intravenous opiates may be required to obtain the optimal position.
For an unstable first trimester pregnant patient, the first view that should be obtained is Morison’s Pouch to look for free fluid. If positive, a diagnosis of ruptured ectopic is essentially made.
When evaluating Morison’s Pouch, it is imperative to visualize the caudal tip of the liver / inferior renal pole, as free abdominal fluid will first collect here.
The minimum volume of free intraperitoneal fluid required for detection by FAST has been reported to range from 100 to 620 mL.3
Abrams BJ, Sukumvanich P, Seibel R, Moscati R, Jehle D. Ultrasound for the detection of intraperitoneal fluid: the role of Trendelenburg positioning. Am J Emerg Med. 1999;17:(2)117-20. [pubmed]