The external iliac vessels course anteriorly adjacent to the iliopsoas to exit the pelvis at the inguinal ligament. The internal iliac (hypogastric) vessels course posteriorly across the sciatic foramen dividing rapidly into smaller branches. The common iliac vessels divide at the pelvic brim, marked on CT by the transition between the convex sacral promontory and the concave sacral cavity. The aorta and vena cava divide to form the common iliac vessels at the level of the top of the iliac crest. The arteries and veins define the location of the major lymphatic node chains in the pelvis ( Fig. This fossa is seen as a triangular area of fat density extending between the obturator internus laterally, the gluteus maximus posteriorly, and the anus and urogenital region medially. On CT, the most obvious portion of the perineum is the ischiorectal fossa. The perineum lies below the pelvic diaphragm. Any soft‐tissue density in this space is abnormal and must be explained. The presacral space between sacrum and rectum normally contains only fat. Fascial planes also allow communication with the scrotum and labia. The retropubic space (of Retzius) is continuous with the posterior pararenal space and the extraperitoneal fat of the abdominal wall. Pathologic processes from the pelvis may spread preferentially into the retroperitoneal compartments of the abdomen. The extraperitoneal space of the pelvis is continuous with the retroperitoneal space of the abdomen. The peritoneal cavity extends to the level of the vagina forming the pouch of Douglas in female individuals, or to the level of the seminal vesicles forming the rectovesical pouch in male individuals. These are important to understand because anatomic compartments allow determination of the origin and spread of disease. The pelvis is divided into three major anatomic compartments ( Figs. The pelvic diaphragm is penetrated by the rectum, urethra, and vagina. The pelvic diaphragm, which is composed of the levator ani anteriorly and the coccygeus posteriorly, stretches across the pelvis to separate the pelvic cavity from the perineum. The piriformis forms a portion of the lateral wall of the true pelvis. The piriformis muscles arise from the anterior sacrum and exit the pelvis through the greater sciatic foramen to insert on the greater trochanter of the femur. Involvement of these muscles by pelvic tumors precludes surgical resection of the tumor. The obturator internus muscles line the interior surface of the lateral walls of the true pelvis. The iliopsoas muscles exit the pelvis anteriorly to insert on the lesser trochanters of the femurs. The psoas muscles extend from the lumbar vertebra through the greater pelvis to join with the iliacus muscles arising from the iliac fossa. Muscle groups form prominent anatomic landmarks on CT. It contains small bowel loops and portions of the ascending, descending, and sigmoid colon. The false pelvis is open anteriorly and is bounded laterally by the iliac fossae. The true pelvis contains the rectum, bladder, pelvic ureters, and prostate and seminal vesicles in the male, or vagina, uterus, and ovaries in the female individual. The true (lesser) pelvis is divided from the false (greater) pelvis by an oblique plane extending across the pelvic brim from the sacral promontory to the symphysis pubis. Brant M.D., in Fundamentals of Body CT (Third Edition), 2006 Anatomy
0 kommentar(er)
