Urinary tract

The anatomy of the urinary tract is important for gynaecological surgeons as the bladder and ureters are intimately related to the genital organs and can be damaged perioperatively.

Ureters

The ureters drain urine from the renal pelvises into the bladder. They descend into the pelvis retroperitoneally passing down on the psoas major muscle. When they reach the brim of the pelvis they turn posterioinferiorly, passing over the bifurcation of the common iliac arteries. They continue to pass into the pelvis attached to the lateral pelvic peritoneum and pass underneath the uterine artery before turning anteromedially into the bladder. The position in relation to the uterine artery is classically described as ‘water under the bridge' with the ureters containing ‘water' passing under the ‘bridge' of the uterine arteries.

During radical hysterectomy, when the uterus is lifted out of the pelvis, the ureters appear to pass downwards before entering the bladder and this is often referred to as the ‘genu'. As the ureter turns medially to enter the bladder, there are often vascular fibres between the bladder and the vagina that have to be divided during a radical hysterectomy for cancer. This area is often referred to as the ‘ureteric tunnel'. At the entrance to the bladder, the ureters are sur­rounded by valves that prevent the backflow of urine. These are the ureterovesical valves.

The blood supply to the ureters varies along their course. The upper part is supplied by the renal arteries. The middle is supplied by branches from the aorta and common iliac artery. The lower part is supplied from braches of the internal iliac, uterine, and superior vesical arteries.

The innervation is from nerves from T12-L2. It is for this reason that ureteric pain may be referred to the back and sides of the ab­domen as well as the labia majora.

The ureters are normally single on both sides.

Bladder and urethra

The bladder is divided into a fundus at the top and a trigone. The trigone is the triangular part of the bladder bordered by the two ur­eteric orifices and urethral opening. When empty, the posterior part of the bladder lies on the cervix and anterior vagina (Figure 3.3). The fundus is covered by peritoneum that is continuous with that over the uterus at the uterovesical fold. Similarly, the peritoneum is continuous with that of the abdominal wall anteriorly. Anteriorly and inferior to the abdominal wall fold of peritoneum there is an avascular space between the pubic bone and the bladder called the space of Retzius which is entered during some urogynaecological procedures. Either side of the space of Retzius are the paravesical spaces which are developed in some urogynaecological and gynae­cological oncology procedures.

The blood supply is via the internal iliac artery that gives off an inferior vesical artery and several superior vesical branches. Some blood supply also comes from the obturator, uterine, and vaginal arteries. The lymphatic drainage is via the obturator, internal, and external iliac chains nodes.

When full, the bladder has a capacity of about 400 mL. The sen­sation to void occurs via general visceral afferent fibres that follow the sympathetic efferent nerves from the hypogastric plexus on the superior surface and the course of the parasympathetic efferent from the splanchnic nerves and inferior hypogastric plexus on the inferior portion. Urine is expelled through the urethra following a contrac­tion of its main muscle (the detrusor muscle) with the opening of both the autonomically controlled internal urethral sphincter and voluntarily controlled external sphincter.

The female urethra is about 4 cm long and extends from the bladder neck and terminates at the vaginal vestibule. The urethra pierces the pelvic diaphragm and perineal membrane just posterior to the pubic symphysis. The opening can be seen on the external genitalia (Figure 3.2).

Clinical considerations

The hypogastric nerves can be damaged during some gynaeco­logical oncology and urogynaecological surgical procedures. This can sometimes result in altered bladder function. Modern sur­gical techniques now involve attempts to identify these fibres and preserve them.

Damage to supporting muscles and connective tissue in the pelvic diaphragm (often from childbirth) can cause prolapse of the bladder and incontinence. This is described in more detail in Chapters 56 and 57.