Page 275 - Medicine and Surgery

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Chapter 6: Urinary stones 271

vomit. They are restless and move around trying to re- Lithotripsy (external ultrasound shock waves), US
lieve the pain. Bladder or urethral stones may cause pain guided, no need for anaesthetic. Stones within calyces
on passing urine, inability to pass urine or the sensation cannot be broken up this way.
of passing gravel. Ninety per cent have haematuria, some Lasertripsy, electrical.
may have proteinuria. Open surgery (nephrolithotomy or ureterolitho-
Infectionmaypresentasanacute,recurrentorchronic tomy), or percutaneous removal via a nephrostomy.
cystitis, pyelonephritis or pyonephrosis (obstruction Alternatively perurethral by cystoscopy witha Dormia
with a stone can lead to hydronephrosis, which if this basket for low stones.
then becomes infected, can make the patient very un-
well). Subsequent management
If the stone obstructs a single functioning kidney, To reduce the risk of recurrence, all patients should be
postrenal acute renal failure results. advised to drink plenty of fluid, especially at night and
to treat urinary infections early.
Investigations Patients with calcium stones should avoid calcium in-
Plain AXR: Most stones are radio-opaque and show take and vitamin D supplements. Potassium citrate

up on plain abdominal X-rays. Calcium oxalate stones may also be given to increase urine levels of citrate
lookspiky,calciumphosphatestonesareoftensmooth which inhibits calcium stone formation.
and can be large. Uric acid stones are radiolucent and Oxalate is found in tea, chocolate, nuts, strawberries,
cystine stones only slightly radio-opaque. spinach, rhubarb and beans.
IVU: i.v. contrast with AXR at 5 and 20 minutes to Uric acid excretion can be reduced using allopurinol.

show exactly where the stone is in relation to the kid- Cystine stones can be reduced using oral sodium bi-
neys and ureters. This should be avoided if there is carbonate to alkalinise the urine, or d-penicillamine.
significantrenalimpairmentbecauseexcretionispoor Consider looking for predisposing factors such as
so that images are less informative and there is an in- plasma calcium and parathyroid hormone (if radio-
creased risk of contrast causing acute renal failure. opaque stone), phosphate, urate if radiolucent stones,
Renal ultrasound may show stones inside kidney and and 24 hour collection of urine for components of

demonstrate hydronephrosis due to obstruction. CT stones.
is often more sensitive.
Serial X-rays to see if stone is moving.

Prognosis
Urine microscopy and culture. Strain all urine to try

Despite preventative strategies recurrence rates are as
to catch the stone so that it can be analysed. Crystals
high as 75%.
may be seen in urine which can help identify the type
of stone.
Stag horn calculus
Management
Treat pain, e.g. with opiates and/or NSAID such as di- Definition
clofenac (useful i.m. or as a suppository). Some recom- Aurinary stone which fills the calyces and pelvis of a
mend anti-spasmodic drugs. Ensure adequate fluid in- kidney, these are usually associated with infection and
take. Stones ≥5mmin diameter are less likely to pass, are formed of struvite.
stones <5mm especially in the lower half of ureter are
more likely to pass without intervention. Aetiology/pathophysiology
Surgical techniques are needed if the stone does not Stag horn calculi are struvite stones (i.e. formed of stru-
pass. It may be necessary to relieve obstruction urgently, vite and calcium carbonate-apatite). Infection with Pro-
if there is obstruction or infection. Obstruction can be teus or Klebsiella causes increased amounts of ammonia,
relieved by retrograde stent insertion (usually requires due to the presence of urease (which breaks down urea
general anaesthetic), or percutaneous nephrostomy in- into ammonia and carbon dioxide). This increases the
sertion under local anaesthetic. amount of ammonium, but also alkalinises the urine,