Kidney and ureteric stones are common and in daily urological surgical practice, stone procedures are performed weekly. Stones form within the kidney due to the patient not drinking enough fluid, and urine is allowed to crystallise and come out of solution and calcify. The typical kidney stone is a calcium based stone, either calcium oxalate or calcium phosphate and this is in 90% of stone cases. 10% of stones are uric acid stones in a patient with hyperuricaemia or gout. These uric acid stones, as distinct from the calcium stones, cannot be seen on a plain xray.
CT scanning is the gold standard way of detecting kidney or ureteric stones and the Hounsfield unit (HU) density, as measured by the radiologist, can tell us how calcium-rich a stone is. A Hounsfield density well above 500 and approaching 1000, implies a very hard stone. The relevance of this is that harder stones require more Holmium laser lithotripsy energy and possibly a slightly longer lasering time to destroy and fragment the stone. It is imperative that all kidney and ureteric stone patients have a urine culture to ensure sterility of the urine, as stone surgery with laser must not be performed when the urine is infected, as this can lead to post-operative sepsis, (blood poisoning).
Certain stones if left untreated can grow to become an internal cast of the urinary collecting system, and these are called partial staghorn or complete staghorn calculi, and these are much more difficult and challenging to manage.
Certain partial staghorn calculi can be managed with several sessions of retrograde Holmium laser lithotripsy, however complete staghorn calculi require either percutaneous nephrolithotomy punctures through the flank approach, (PCNL), or a combination of this in association with either retrograde laser or in combination with ESWL (external shock wave lithotripsy), as sandwich therapy.
Staghorn calculi are triple phosphate stones, that tend to harbour bacteria and their treatment carries a higher risk of post-operative infection, than simple smaller stones. In general, urologists will only electively access the kidney to laser a stone if it is > 5-7mm, the rationale here being that if this stone was to distally migrate into the ureter, a 5-7mm stone would like not spontaneously pass through the 22cm length of the ureter and may get blocked, either at the top, middle or bottom end of the ureteric pipe.
A common urological emergency presentation is for a kidney stone to migrate into the ureter, the tube that connects the kidney with the bladder and block that system, requiring the patient to present to emergency for opioid pain relief.
The urologist will initially place a hollow plastic decompressing tube to unblock that system under a short general anaesthetic, and the patient then returns to the rooms for further consultation and to time the definitive laser fragmentation and destruction retrieval of that stone with subsequent removal of that ureteric stent tube.
Certain patients, in particular diabetics who have a stone blocking the kidney, may concomitantly have infection and require lengthy in-hospital stays for intravenous antibiotic therapy, which ultimately delays the definitive laser stone procedure.
Prevention of kidney stones include drinking more water, 2-3 litres per day, adding citrus to the diet, which is a known inhibitor of calcium oxalate stones, and also for calcium stones, reducing foods rich in protein, salt and oxalate. Oxalate rich foods include foods containing; rhubarb, spinach, beer nuts, beer and tea.
In certain high volume and frequent recurrent stone formers, the patient is sent to a medical kidney specialist, (Nephrologist, Renal Physician), in order for a formal urinary and biochemical stone work up to be performed, which includes a 48 hour urine collection, and blood tests including uric acid, calcium, parathyroid hormone levels.
Certain recurrent calcium stone formers with hypercalcaemia may have a parathyroid adenoma that requires referral to an endocrinologist and/or head and neck surgeon.
Margaret Troup our clinical specialist practice nurse has substantial patient reading information regarding kidney stones.