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270 Chapter 6: Genitourinary system

On examination the swelling is confined to one side Age
and the swelling is hot and very tender. Peaks age 20–50 years.

Microscopy Sex
Thereisextensiveinfiltrationoftheseminiferoustubules M > F (4:1)
and interstitium with neutrophils, initial oedema is con-
siderable and there is often patchy haemorrhage. Aetiology
Risk factors include: dehydration, urinary tract infec-
tions, disorders of calcium handling (hypercalcaemia,
Complications
hypercalciuria), hyperuricaemia, small intestinal dis-
Infertility is an important complication.
ease or resection, renal tubular acidosis, hereditary con-
ditions (such as cystinuria) and drugs in particular
Investigations
sulphonamides at high doses and indinavir (a protease
Urine (first catch is best, rather than MSU, under these
inhibitor used to treat HIV).
circumstances) and any urethral discharge should be
cultured.
Pathophysiology
Stone formation usually occurs because compounds of
Management
low solubility are present in the urine in high concentra-
Treatment is with antibiotics, bed rest and scrotal sup-
tions.Thereareinorganicinhibitorsofcrystalformation,
port. In young adults, erythromycin (to cover Chlamy-
such as magnesium, citrate and organic inhibitors such
dia)isprobably best, whereas in older individuals or
as glycoseaminoglycans and nephrocalcin. Uric acid ap-
where there is a good history of UTI, suggested antibi-
pears to interfere with this inhibition, so when present
otics are the same as those for UTI, e.g. trimethoprim.
in high concentrations it predisposes to the formation
of both uric acid and non-uric acid stones.
Stones commonly contain calcium oxalate (80%) but
Urinary stones about half of these also contain hydroxyapatite. ∼10%
are struvite (magnesium ammonium phosphate) stones
whichconsistofstruviteandcalciumcarbonate-apatite),
Urinary stones
with the remainder formed of calcium phosphate, uric
Definition acid or cystine (see Table 6.15).
The development of stones in the urinary tract or uroli-
thiasis. Clinical features
Renal or ureteric colic is the most common presentation.
Incidence/prevalence The pain is characteristically in sharp, intense waves over
Affects about 10% of the population at some time in abackground pain, occurring in the loin, radiating to
their lives. the groin and testes or labia. Patients feel sick and often

Table 6.15 Types of Urinary Stones
Type of stone Pathogenesis Features
Calcium 30% have hypercalciuria 1. Absorptive (primary increased intestinal absorption)
Idiopathic (most common)
2. Renal (primary renal loss of calcium compensated by ↑ absorption)
3. Resorptive (primary increased skeletal resorption)
Hypercalcaemia Less commonly
Oxalate ↑ urinary oxalate levels
Uric acid Hyperuricosuria ↑↑ uric acid stones ↑ calcium oxalate stones
Cystine Cystinuria Autosomal recessively inherited condition