The hepatorenal recess (“Morison’s pouch”) is a potential space between the liver and right kidney. With small volumes of intraabdominal blood (hemoperitoneum), ascites, or even peritoneal dialysis, fluid accumulates in this recess which shows up as a near-black stripe on ultrasound. This video shows Morison’s pouch containing no discernible fluid collection.
In the video above, the patient’s head is on the left and feet are on the right. The liver is the large structure occupying most of the left ultrasound field. You can make out the elliptical right kidney tissue and note the echogenic renal pelvis. Note how there’s a smooth, seamless transition between the liver and kidney tissue. This is where I often see fluid (usually black-gray depending on its composition) in the aforementioned conditions.
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