Intraperitoneal paravesical spaces: CT delineation with US correlation

The urinary bladder, obliterated umbilical arteries, and inferior epigastric vessels located within the extraperitoneal space of the anterior abdominal wall indent the anterior parietal peritoneum, forming intraperitoneal paravesical fossae. These are the supravesical space and the medial and lateral inguinal fossae. More posteriorly, the peritoneum covering the bladder is reflected onto the rectum to form the rectovesical space, which is divided by the uterus into an anterior vesicouterine recess and a posterior rectouterine pouch, or cul-de-sac. The cul-de-sac is continuous with the pararectal and ovarian fossae and is bounded posterolaterally by the rectouterine (sacrogenital) folds. These peritoneal compartments form a large potential space for the accumulation of ascites and are separated from the equally large extraperitoneal paravesical spaces by only a thin layer of peritoneum or peritoneum and umbilicovesical fascia. The computed tomographic scans of 100 patients with ascites were reviewed, with particular attention to the differentiation between intraperitoneal and extraperitoneal paravesical collections. The scans of intraperitoneal collections were found to have certain characteristic appearances, including inferior displacement of the distended urinary bladder, visualization of the umbilical folds, and preservation of the preperitoneal fat.     

Choroidal melanomas: correlation of NMR spectroscopy and MR imaging

Six freshly enucleated, unfixed human eyes with choroidal melanomas were imaged on a 1.4-T superconducting magnetic resonance (MR) imaging system. Immediately thereafter the eyes were sectioned, and tumor samples were removed for study on a variable-field (0.19-1.4 T) nuclear MR spectroscopy unit. Shorter T1 and T2 relaxation times were observed in those tumors with the greater concentrations of melanin. This is believed to result from the paramagnetic effect of radicals known to exist in melanin. High magnetic field MR imaging can enable one to distinguish between pigmented melanomas; proteinaceous effusions; fresh and subacute hematomas; and nonmelanotic tumors, including amelanotic melanomas; but may not enable melanotic melanoma to be distinguished from fat or amelanotic melanoma from other nonpigmented tumors.     

Spinal cord central echo complex: histoanatomic correlation

Real-time sonography consistently demonstrates an echo complex centrally located in the spinal cord. This echogenic focus is currently attributed to the central canal. The authors sought the source of this central echo with ultrasound (US) and histoanatomic study of both fresh and fixed cadaver spinal cords. Correlative transverse sections of the spinal cord were stained with hematoxylin-eosin and Luxol fast blue for cells and myelin and with Holzer stain for glial fibrils. The central echo complex is produced by the interface between the myelinated ventral white commissure and the central end of the anterior median fissure. Variations in the shape of the central complex seem to reflect varying degrees of flaring of the central end of the anterior median fissure. The inconstant residual central canal and islands of residual ependymal cells are clearly not the source of the central echo complex.