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Preperitoneal space

The preperitoneal space is a potential anatomical space situated between the parietal peritoneum and the transversalis fascia of the anterior abdominal wall. It contains loose connective tissue and variable amounts of fat. This space is continuous across the anterior abdominal wall but is most prominent in the lower abdomen and pelvis.

The preperitoneal space is clinically significant in hernia formation and repair, particularly inguinal, femoral, and ventral hernias. It is the surgical plane used during laparoscopic and open preperitoneal hernia repair. The space of Retzius (retropubic preperitoneal space) and the space of Bogros (lateral preperitoneal extension) are considered subdivisions.

Because of its fat content, the preperitoneal space is also a pathway for infection, fluid collections, hematomas, and spread of malignancy.

Synonyms

  • Extraperitoneal preperitoneal space

  • Preperitoneal fat space

  • Retzius space (retropubic subdivision)

  • Bogros space (lateral subdivision)

Function

  • Provides fat cushioning between peritoneum and abdominal wall

  • Serves as a surgical plane for hernia repair (e.g., TEP, TAPP approaches)

  • Acts as a potential pathway for spread of infection, hematoma, or tumors

  • Defines an important anatomical landmark in pelvic and abdominal surgery

MRI Appearance

T1-weighted images:

  • Preperitoneal fat appears hyperintense (bright)

  • Distinct from intermediate-signal abdominal wall muscles and low-signal peritoneum

T2-weighted images:

  • Fat remains  hyperintense

  • Pathologies such as fluid collections or edema appear bright hyperintense

STIR:

  • Suppresses fat, making fluid collections, edema, infection, or hematoma conspicuous as bright areas

  • Useful for identifying inflammatory or infiltrative pathology

T1 Fat-Saturated (Pre-contrast):

  • Preperitoneal fat signal suppressed, artery/vein distinction not emphasized (excluded by request)

  • Enhances visualization of abnormal lesions or soft tissue masses within the space

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Normal fat remains suppressed; enhancing collections, tumors, or inflamed peritoneum stand out

  • Useful in differentiating abscesses vs hematomas vs neoplastic infiltration

MRI 3D Imaging:

  • Provides full mapping of preperitoneal fat planes and surgical landmarks

  • Helpful in hernia planning and abdominal wall reconstruction

CT Appearance

CT Pre-Contrast:

  • Preperitoneal fat appears as low-density (-80 to -100 HU)

  • Differentiates clearly from higher-density muscle and peritoneal lining

  • Can demonstrate hematomas, masses, or fat stranding

CT Post-Contrast:

  • Fat remains unenhanced, but collections, inflammatory changes, or tumors enhance relative to suppressed fat density

  • Hernias are well defined by protrusion of fat, bowel, or omentum into or through the preperitoneal space

  • Widely used for hernia mapping, trauma, and infection assessment

MRI image

Preperitoneal space MRI sag anatomy image-img-00000-00000_00001

MRI image

Preperitoneal space MRI axial anatomy image-img-00000-00000_00001

CT image

Preperitoneal space CT axial image