The pelvis is the area of transition between the trunk and lower limbs. In males, the pelvis is narrower, higher and more compact than that of their female counterpart. It is optimized for bipedal locomotion rather than pregnancy and childbirth. A study of the cross-sectional anatomy of this area allows a visual medium that facilitates the understanding of its structural organization. That will allow us to have a clear view of the positions, sizes, shapes and relationships of the male pelvic structures.
Anatomy of the male pelvis
The cross-sectional anatomy of the male pelvis shows five bones: two hip bones, sacrum, coccyx and two femurs. Each hip bone is formed by the fusion of three bones: the ilium, pubis and ischium. The sacrum and coccyx are also comprised of smaller bones. The first is formed by the fusion of the five sacral vertebrae (S1-S5), and the latter by the fusion of the four coccygeal vertebrae. The femur is the strong thigh bone. It articulates with the hip, forming the ball-and-socket hip joint.
There’s a numerous variety of muscles that can be seen in the male pelvis depending on the level of the cross section. The abdominal region includes the external oblique, internal oblique, transversus abdominis, rectus abdominis and pyramidalis muscles.
The back region includes the quadratus lumborum and the muscles belonging to the erector spinae.
The muscles present in the thigh region can be split into three sections - anterior, medial and posterior. The anterior compartment is comprised of the psoas major, iliacus, quadratus femoris and pectineus. The medial compartment is comprised of the adductor magnus, adductor minimus, adductor longus, adductor brevis, obturator externus and gracilis. The posterior compartment shows the semitendinosus muscle only.
In the gluteal region, the muscles seen there are the gluteus maximus, gluteus medius and gluteus minimus; as well as the deeper piriformis, gemellus superior, gemellus inferior and obturator internus muscle. The pelvic floor includes the levator ani, coccygeus, ischiocavernosus and bulbospongiosus muscles.
The major organs present in a male pelvis cross-section are those belonging to the digestive, urinary and reproductive systems. Organs of the digestive tract include the sigmoid colon, small intestine, rectum, and anus. Organs of the urinary system include the urethra, bladder and the two ureters. The main structures of the male reproductive system are the scrotum, epididymis, testes, seminal vesicles, spermatic duct, penis, and bulbourethral and prostate glands.
The arteries located in the male pelvic region include the aorta, common iliac, and branches of the external and internal iliac arteries. The veins in this area are similar to that of their corresponding arteries, with the addition of the inferior vena cava. The nerves present include those arising from the sacral and coccygeal plexuses, as well as the obturator nerve originating from the lumbar plexus.
Ultrasound is the imaging modality of choice for the evaluation of the male pelvis. However, it has its own set of shortcomings, like limited ﬁeld of view and its dependency on the operator’s skill and experience. Here, magnetic resonance imaging (MRI) becomes the diagnostic tool for male pelvic pathologies. This scan depends on the cross-sectional analysis of the complex anatomic structures in the male pelvic region, and plays a vital role in clinical practice. It is mainly used to detect prostate diseases, undescended testis, congenital abnormalities, cancers and swellings in that region. Computed tomography (CT) is only used in the setting of trauma, due to radiation exposure to the testis.