From the Guidelines
Morrison pouch, also known as the hepatorenal recess, is a potential space located between the liver and the right kidney in the abdominal cavity, and it is a critical area to examine for free fluid accumulation, particularly in trauma patients, as evidenced by the emergency ultrasound imaging criteria compendium by the American College of Emergency Physicians 1.
Clinical Significance
The Morrison pouch is the lowest part of the peritoneal cavity when a person is lying supine, making it a common site for fluid collection during abdominal trauma or infection. This anatomical space is clinically significant because it's routinely examined during focused assessment with sonography for trauma (FAST) exams to detect free intraperitoneal fluid, which may indicate internal bleeding, as described in the study by the American College of Emergency Physicians 1.
Anatomical Borders
The pouch is bordered by the liver anteriorly, the right kidney posteriorly, the hepatorenal ligament superiorly, and the transverse colon inferiorly. Due to its dependent position, even small amounts of fluid (as little as 200 mL) can accumulate here and be detected on ultrasound, making it valuable for early diagnosis of intra-abdominal hemorrhage or ascites.
Diagnostic Importance
Understanding Morrison pouch is essential for emergency physicians, radiologists, and surgeons when evaluating patients with abdominal trauma or pathology. The use of ultrasound to examine this area, as outlined in the emergency ultrasound imaging criteria compendium 1, allows for the rapid detection of free fluid, which can be critical in guiding immediate management decisions, especially in emergency settings.
Ultrasound Examination
The examination of Morrison's pouch involves placing the ultrasound probe in a subcostal location in the mid-clavicular line or using an intercostal approach to minimize rib shadowing, with the probe indicator directed toward the head of the rib, as detailed in the study 1. By angling the probe superiorly or inferiorly, different potential spaces, including the subhepatic space, the right pleural space, and Morison’s pouch, can be visualized for fluid accumulation.
From the Research
Definition of Morrison Pouch
- Morrison's pouch is the intraperitoneal space in the supramesocolic compartment located between the right liver lobe and right kidney 2.
- It is also known as the hepatorenal pouch or recess, and is a dependent area where fluid can accumulate 3, 4, 5, 6.
Clinical Significance
- The presence of fluid in Morrison's pouch can be an indicator of various pathological conditions, including hemoperitoneum, infectious or inflammatory processes, and neoplasms 2, 6.
- The evaluation of Morrison's pouch is important in the assessment of abdominal trauma, as it can help identify the need for operative intervention 3, 4, 5.
- Free fluid in Morrison's pouch on bedside ultrasound can predict the need for operative intervention in suspected ectopic pregnancy 5.
Imaging and Diagnosis
- Morrison's pouch can be visualized using various imaging modalities, including ultrasound, CT scans, and MRI 3, 2, 4, 6.
- The appearance of pathological entities on these imaging modalities can help radiologists make the correct diagnosis 2, 6.
- A linear function can be used to estimate the volume of free intraperitoneal fluid (FIPF) based on the thickness of fluid in Morrison's pouch on CT scans 3.