Imaging professionals must brush up on their knowledge of the pelvis, particularly the normal anatomy and its correlation with multidetector-row CT (MDCT) images, award-winning researchers from Spain have asserted.
MDCT is used frequently in the evaluation of pelvic pathology, but in many cases, normal anatomic landmarks are distorted. The relation between different pelvic structures and the altered anatomical points can be used to determine the nature of a pathologic process, noted Dr. Lina Marcela Cruz Hernandez, radiology resident, and colleagues from the department of medical imaging at Virgen de la Salud Hospital in Toledo, in an ECR 2014 e-poster presentation that received a cum laude award.
"Accurate knowledge of pelvic anatomy helps distinguish the precise location of the affected structures, and together with the clinical history, helps establish a differential diagnosis, which can sometimes be crucial in patient management and secondarily in its evolution," they explained. "Detailed anatomical knowledge of the pelvis allows more accurate evaluation of pathology to enable the radiologist to narrow the differential diagnoses. This precision helps the clinician to define therapeutic options."
In their ECR exhibit, the authors aimed to review and simplify the complex pelvic anatomy and its principal anatomic landmarks, describe normal anatomy and its correlation with MDCT using CT color-coded images, and to demonstrate how understanding the relevant pelvic anatomical structures allows the diagnosis of different pathological processes.
The authors' key points were:
The bony pelvis consists of innominate bones, each with three parts (ilium, ischium, and pubis), sacrum, and coccyx. It protects the pelvic viscera, provides attachment for the muscles of the trunk and lower limb, and enables stable transfer of the body weight from the spine to the femora.
An important anatomic landmark in CT evaluation of the pelvis is the obturator internus muscle. The portion of the obturator internus above this origin lies in the lateral wall of the false pelvis, whereas the lower portion forms part of the lateral wall of the ischiorectal fossa.
Between the anal canal and the urogenital diaphragm lies the central tendon of the perineum. This fibromuscular node is important as the central junction of most of the perineal muscles.
The posterior bladder spaces vary between the sexes. In men, there is the rectovesical pouch; while in women, there is the anterior uterovesical pouch, and the posterior rectouterine pouch or pouch of Douglas.
The following points about the arterial system should not be overlooked: The abdominal aorta divides into common iliac arteries at the L4-L5 level; the testicular and ovarian arteries originate below renal arteries; the common iliac arteries run anterior iliac veins and inferior to vena cava, descend behind the ureters and divide into external and internal iliac arteries at the sacroiliac joint level; and the inferior epigastric (medial) and deep iliac circumflex (lateral) arteries demarcate between the external iliac and common femoral arteries.
The external and internal iliac veins correspond to their arteries, and have a medial position with respect to the arteries and become posterior progressively. In the external iliac vein, upward continuation of the femoral vein occurs at the level of the inguinal ligament. The internal iliac vein begins near the upper part of the greater sciatic foramen.
The right gonadal vein drains into the vena cava, and the left gonadal vein drains into the left renal vein.
The sigmoid colon has variable length and morphology. It is supplied by the inferior mesenteric artery and vein, and coated by a double layer of the peritoneum. It lies in the extraperitoneal pelvis, and has mesenteric and systemic vessels (superior rectal branches of inferior mesenteric artery and vein, and middle and inferior rectal braches of internal iliac vessels).
