Retroperitoneal space and pelvic cavity

Case study

A 78-year-old female patient has an appointment with her gynaecologist because she increasingly passes urine when she coughs or sneezes. She has had these symptoms for a long time and has so far managed it well with pads, but now the involuntary passing of urine is becoming increasingly uncomfortable. The patient has four children, all born naturally (by vaginal delivery).

Result of examination

The physical examination is largely unremarkable. When her abdominal muscles contract (abdominal pressure), a mucus-coated enlargement prolapses into the vaginal orifice.

Diagnostic procedure

The vaginal examination (colposcopy) shows that the posterior wall of the urinary bladder has dropped (cystocele). When the intra-abdominal pressure increases, the anterior wall of the uterus also protrudes (uterine prolapse).

Diagnosis

Incontinence due to insufficiency of the pelvic floor, along with a cystocele and prolapse of the uterus ( Fig. a ). These issues are very common in elderly women and often caused by pregnancies. As the delivery mode apparently does not play an important role, caesarean sections would not significantly reduce the risk.

Treatment

The patient is advised to do pelvic floor exercises under the guidance of a physiotherapist. After two months the patient can increasingly better control the passing of urine.

Further developments

After five years, the incontinence gets worse again. The patient is admitted to the gynaecology ward for surgical treatment with so-called tension-free vaginal tapes (TVTs). After this, she is largely symptom-free.

Dissection lab

The pelvic floor (Diaphragma pelvis) and the adjacent perineum (Regio perinealis) are anatomically and clinically challenging regions. The pelvic floor can be easily dissected from the lesser pelvis once the pelvis has been split down the middle, and one half has been removed along with the bone. The Diaphragma pelvis is then visible as a striated muscle plate composed of three muscle parts.

Across various dissections, compare the different thicknesses of the pelvic floor in men and women. As the majority of body donors are elderly, the pelvic floor is often in a very poor condition.

These parts are predominantly innervated by direct branches of the Plexus sacralis, and designated ventrally as M. levator ani (consisting of the M. pubococcygeus and M. iliococcygeus), and dorsally as M. ischiococcygeus. The term ‘pelvic floor’ (Diaphragma pelvis) was chosen because this muscle plate caudally closes off a body cavity, in the same way as the diaphragm closes off the lower opening of the thorax. The muscles of both sides leave an opening medially, the Hiatus levatorius, for the passage of the anal canal, urethra and, in women, the vagina. The name for these muscles largely reflects their route from the hip bone to the sacrum and coccyx. The M. iliococcygeus does not have a bony origin, and is only indirectly attached to the pelvic bones because it originates from a duplication of the fascia of the M. obturatorius internus (Arcus tendineus m. levatoris ani). This muscle can be easily identified due to the Canalis obturatorius, which penetrates the muscle and leads the A./V. obturatoria and the N. obturatorius from the pelvic cavity to the anterior aspect of the thigh. Caudally of the Arcus tendineus m. levatoris ani, it disappears below the pelvic floor,

Here you can put your hand between the M. levator ani and the M. obturatorius internus to feel the different routes of the two muscles.

nestling against the lateral pelvic wall, where it is redirected at the ischium and then passes through the Foramen ischiadicum minus to the Trochanter major of the femur. This opening can be depicted better dorsally and caudally. To do this, the M. gluteus maximus must be detached medially from its origin in the dorsal gluteal region and folded back laterally. Then the M. piriformis becomes visible, as well as the Lig. sacrotuberale which bridges the Foramen ischiadicum minus. Through this opening, the A./V. pudenda interna and the N. pudendus pass caudally from the gluteal region into the Fossa ischioanalis, which occupies the posterior half of the perineal region on both sides of the anus. They are embedded here in another duplication of the fascia of the M. obturatorius (Canalis pudendalis, ALCOCK's canal).

Once you have seen the dimensions of this space, you will understand how septic foci (abscesses) almost the size of a fist can form here, most of which spread from fistulas in the anal canal.

The Fossa ischioanalis is a pyramid-shaped space largely filled with adipose tissue, which at the top is limited medially by the lower surface of the M. levator ani and laterally by the M. obturatorius internus along with the ALCOCK's canal. It extends at the front up to the perineal musculature and forms very variable prolongations up to the pubic symphysis (Symphysis pubica).

Back in the clinic

The pelvic floor supports all the pelvic organs which lie on top of it. This explains why it is important for urinary and faecal continence, although it does not form a sphincter like the muscles of the perineum. In perineal operations, an aggravating factor for stabilising the pelvic floor is the fact that the patients are mostly in the supine ‘lithotomy’ position, which you have to keep in mind when visualising the anatomical relationships.