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262 Chapter 6: Genitourinary system

compensatorybladderhypertrophy.Overtime,theblad- Benign prostatic hyperplasia
der distends, then the ureters (causing hydroureters) and
Definition
finally the renal pelvises. Often there may be an un-
Hyperplasiaoftheprostateisacommoncauseof bladder
derlying chronic obstruction for example an enlarged
outflow obstruction.
prostate. Another factor may then cause acute urinary
retention, e.g. constipation, bed rest (e.g. after surgery).
Incidence/prevalence
Common.
Clinical features
The symptoms depend on the speed of onset and degree
Age
of obstruction.
Affects ∼50% of men age 50–60, >80% of men age >80.
Acute obstruction (acute urinary retention) causes se-

vere discomfort, due to a wish to void urine, without
Sex
the ability to do so. The bladder is tender, palpably en-
Males
larged. There is complete anuria, although there may
be small amounts of urine voided due to overflow in-
Aetiology
continence.
Thought to be due to increased androgen effects (di-
Chronic obstruction causes three features: hesitancy,

hydrotestosterone and its metabolites), or oestrogens.
poor urinary stream (<10 mL/second) and terminal
Functioning testes are important: castrati (before pu-
dribbling. Frequency and nocturia are not symptoms
berty) do not get BPH. Castration post-onset gives a
of obstruction. The symptoms usually develop over
30% reduction in size only.
years, and if left untreated patients may present with
renal failure. However, polyuria and/or nocturia may
Pathophysiology
be symptoms of the loss of concentrating ability of the
Androgens appear to act on the periurethral area of the
tubules, which can occur in long-standing obstruc-
prostate ‘McNeal’s transition zone’ to stimulate hyper-
tion.
plasia. There is compensatory bladder hypertrophy. At
30–40 years there is microscopic evidence, by 50 years it
Macroscopy
is macroscopically visible, by 60 years the clinical phase
Dilation above the obstruction. Bladder trabeculation.
begins.
The obstruction is due to both direct impingement
Complications of the enlarged prostate on the urethra and also the dy-
Asaresultofchronicobstruction,thebladderdilatesand namic smooth muscle contraction of the prostate, pro-
fails to empty fully, defined as >50 mL residual urine static capsule and bladder neck.
(normally 5–10 mL in young, fit person). Renal failure
can be caused by both acute and chronic obstruction. Clinical features
Chronic urinary retention leads to: Usually a long history of bladder outflow obstruction,
Reduced functional bladder capacity and therefore in- but may present as acute urinary retention or a UTI,

creased frequency. or with frequency and urgency symptoms. Per rectum
Recurrent UTI’s. examination reveals a smoothly enlarged prostate, with

Stone formation can be caused by urinary stasis, UTI’s intact median groove.

predispose to stone formation, and also stones may
predispose to infection. Macroscopy
There is hyperplasia of the transition zone. Nodules
Management formedofhyperplasticglandularacinidisplaceandcom-
Relief of the obstruction is usually by insertion of a uri- press the true prostatic glands peripherally forming a
nary catheter, followed by treatment of the underlying false capsule. Weight usually up to 200 g (normal is
cause. 15 g).