The prostate Prof. Abdulrazzaq Al-Salman
Embryology:/ From the primitive urethra as a series of solid epithelial buds
which in a matter of weeks become canalized. Surrounding mesenchyme
forms the muscular and connective tissue of the gland and has a major role
in differentiation (stromal epithelium interactions).
Surgical anatomy/ McNeal classification of the prostate into different zones:
the peripheral zone (PZ) which lies mainly posteriorly and from which most
carcinomas arise, and a central zone (CZ) which lies posterior to the
urethral lumen and above the ejaculatory ducts as they pass through the
prostate. There is a also periurethral transitional zone (TZ) from which most
benign prostatic hyperplasia (BPH) arises. Smooth muscle cells are found
throughout the prostate. The glands of the peripheral zone , lined by
columnar epithelium, lie in the fibromuscular stroma and their ducts which
are long and branched open into posterolateral grooves on either side of
the verumontanum( common ejaculatory ducts).Benign prostatic
hyperplasia (BPH) starts in the periurethral transitional zone and as it
increases in size it compresses the outer PZ of the prostate which
becomes the false capsule. There is also the outer true fibrous anatomical
capsule; and external to this lie condensations of endopelvic fascia known
as the periprostatic sheath of endo pelvic fascia. Between the anatomical
capsule and the prostatic sheath lies the abundant prostatic venous plexus.
The prostatic sheath is contiguous with the strong fascia of Denonvillier that
separate the prostate and its coverings from the rectum
Physiology:The prostate has a sexual function. The main hormone
acting on the prostate is testosterone which is secreted by the Leydig cells
of the testes, Testosterone is converted to 5-di-hydrotestosterone (DHT) by
the enzyme 5a-reductase,which is found in high concentration in the
prostate and the perigenital skin.Elaboration and secretion of prostate-
specific antigen (PSA) and acid phosphatase.
PSA
is a glycoprotein which
is a serine protease. Its function may be to facilitate liquefaction of semen,
but it is a marker for prostatic disease. The normal upper limit is about 4
nmollml.
Benign prostatic hyperplasia
BPH occurs in men over 50 years.
Aetiology ;Serum testosterone levels slowly but significantly decrease with
advancing age; however, levels of oestrogenic steroids are not decreased
equally. According to this theory the prostate enlarges because of
increased oestrogenic effects.
Pathology: BPH affects both glandular epithelium and connective tissue
stromal to variable degrees. BPH typically affects the submucous group of
glands in the transitional zone, forming a nodular enlargement.
Symptoms of ‘prostatism or lower urinary tract symptoms (LUTS)
Obstructive / Hesitancy (worsened if the bladder is very full) . Poor
flow (unimproved by straining) , Intermittent stream
— stops and starts ,
Dribbling (including after micturition), Sensation of poor bladder emptying ,
Episodes of near retention
Irritative/ Frequency, Nocturia, Urgency,Urge incontinence,Nocturnal
incontinence,(enuresis).
Bladder outflow obstruction:This is a urodynamic concept based on the
combination of low flow rates in the presence of high voiding pressures
• Urinary flow rates decrease [for a voided volume >200 ml; a peak
flow rate of >15 mI/second is normal , one of
10
—15 mI/
second equivocal
and one
<10 mI
/second low.
• Voiding pressures increase [pressures >80 cmH2O are high ,
pressures between 60 and 80 cmH2O are equivocal, pressures <60
cmH2O are normal]
Urodynamically proven bladder outlet obstruction
may result from:
BPH, bladder neck stenosis , bladder neck hypertrophy, prostate cancer,
urethral strictures,functional obstruction due to neuropathic conditions
Assessment of the patient with prostatism
Abdominal examination/ is usually normal. In patients with chronic
retention, a distended bladder will be found on palpation.
General physical examination/ may demonstrate signs of chronic renal
impairment with anaemia and dehydration. The external urinary meatus
should be examined to exclude stenosis, and the epididymes are palpated
for signs of inflammation.
Rectal examination /:In benign enlargement, the posterior surface of the
prostate is smooth, convex and typically elastic, The rectal mucosa can be
made to move over the prostate.
The nervous system is examined /to eliminate a neurological lesion.
Serum prostate-specific antigen/ to exclude prostate cancer . (If this is in
excess of 4 nmol/litre)
Flow rate measurement/Blood tests/:Serum creatinine, electrolytes and
haemoglobin .Examination of urine/,for glucose and blood, a midstream
specimen for bacteriological examination and cytological examination
.Upper tract imaging/if infection or haematuria, should be imaged by
means of an IVU or US.Cystourethroscopy / to exclude a urethral stricture,
a bladder carcinoma and the occasional non opaque vesical calculus..
Transrectal ultrasound scanning/ increases the rate of detection of
associated early prostate cancer .
Management
of benign prostatic hyperplasia or bladder outflow
obstruction
• Conservative ‘watchful waiting’ — general advice about fluid
intake, use of anticholinergic medication in men with mild symptoms.
•Drug
treatment to supplement conservative treatment in men with mild
symptoms (a-adrenergic blocking agents and 5a-reductase inhibitors)
Strong indications for treatment (usually prostatectomy) include:
1.
Acute &chronic retention
.
2. Associated with complications
:
stone
,
infection
and
diverticulum.
3.
haemorrhage
.4.
elective prostatectomy
for
severe symptoms of ‘prostatism’.
Conventional operative treatment:/This includes:
• transurethral resection of the prostate (TURP);• bladder neck
incision for the small prostate (<20 g);• open prostatectomy for the big
gland (>
—80—100 g).
Methods of performing prostatectomy:The prostate can be
approached (1) transurethrally
— TURP, (2) retropubically — RPP(Millin),
(3) through the bladder (transvesical
— TVP) or (4) from the perineum
(young). Preliminary vasectomy is now no longer performed.
Transurethral resection of the prostate:/TURP has largely replaced
other methods unless diverticulectomy or the removal of large stones
necessitates open operation; over 95 per cent of men being treated by
trained urologists can be dealt with by TURP. Hyponatraemia is avoided by
using 1.5 per cent isotonic glycine for irrigation and the recent introduction
of continuous flow resectoscope makes the procedure swift and safe in
experienced hands. At the end of the procedure, careful haemostasis is
performed and a three-way, self-retaining catheter irrigated with isotonic
saline is introduced into the bladder to prevent any further bleeding from
forming blood clots.
Complications:
-LocallHaemorrhage is a major risk following
prostatectomy.Secondary haemorrhage tends to occur after the patient
has been discharged.
Perforation of the bladder or the prostatic capsule.Sepsis, Wound
infection ,Incontinence. Retrograde ejaculation(65%) and impotence (5%).
Urethral stricture,this may be secondary to prolonged catheterisations,
Bladder neck contracture. Reoperation.
-General complications/Death occurs in about 0.2
—0.3 per cent,
Cardiovascular. Pulmonary atelectasis, pneumonia, myocardial
infarction, congestive cardiac failure and deep venous thrombosis .
Water intoxication(TUR syndrom). The absorption of water into the
circulation at the time of transurethral resection can give rise to congestive
cardiac failure, hyponatraemia and haemolysis. Accompanying this there is
frequently confusion and other cerebral events often mimicking a stroke.
The incidence of this condition has been reduced since the introduction of
isotonic glycine for performing the resections and the use of isotonic saline
for postoperative irrigation. The treatment consists of fluid restriction.
Newer treatments:
/ In general, newer, minimally invasive treatments
occupy a position intermediate between TURP and drug treatment.
Microwave and laser treatments and other methods of tissue destruction
lntraurethral stents