Kidney stones (Renal calculi)腎結石

MEDICAL TREATMENT FOR RENAL CALCULI:

WHAT WORKS AND WHAT DON’T.

Dr Clarence Lei, FRCS Urol, Consultant Urologist, Stone Centre, NMSC

clarencelei@gmail.com

Urinary stones affects 5-15% of populations, with a 50% recurrence rate over 10 years. Ureteric colic is the most severe pain that men can ever experience and the standard treatment for most patients is that of Diclofenac. However, if this is given continuously for more than 48 hours, there is a nephrotoxic potential, especially in patients who are dehydrated.  For small stones (< 6 mm) in the lower ureter, removal can be facilitated by uroselective alpha-blockers (e.g. Tamsulosin, Alfuzosin). This is now known as MET medical expulsive therapy! Stones <5mm usually do not require intervention unless complicated by sepsis whereas untreated large stones eventually cause urosepsis.

The important medical treatment for urinary stones is that of water therapy such that the patient produces 2 litres of urine per day. The fluid intake of the patient depends on his environment.  Ideally, such fluid should be distributed throughout the day.  There is no good evidence of advantages of specific juices or herbals.

Uric acid stones can be effectively dissolved by medical therapy by urinary alkalinisation, keeping the urine pH at 7.0.  Uric acid stones comprise about 20% stones and are radiolucent on x-ray but readily seen on ultrasound and plain CT. Even staghorn uric acid calculi can be dissolved over 6 months.   However, the patient should have a good renal function to avoid accumulation of the medications used e.g. potassium, citrate, sodium (in Ural).

Potassium Citrate helps clear post ESWL lower pole fragments (“stone free = <5mm”). In a study when Potassium Citrate was given as Urocit-K tablets 60 meq/day, Urocit-K increased the stone-free rate to 45.5% from 12.5% in control group, over a 12 month period.  The citrate in the urine reduces crystallization of calcium and uric acid stones.  

Stones associated with infection are called struvite stones. Struvite stones are typically soft and faintly radiolucent. The stone and infection should be cleared by surgery and  vigorous antibiotic therapy (e.g. Amikacin) followed by prophylaxis e.g. Trimethoprim at night for 6 months, including in children. 

For patients who have underlying metabolic effects, the benefit of the specific medications may not justify the side effects and long term costs. The diet recommendations for patients with recurrent stone formation is that of less salt, and normal calcium. Patients with uric acid stones should take less uric acid in their diet e.g. red meat, nuts.

Reference (more pdfs available on request):  Singh SK et al.  Medical therapy for calculus disease.  Brit J Urol Int. 2011, 107: 356-368.;

Pak CYC Medical Stone Management: 35 yrs of advances. J Urol 2008, 180; 813 – 819.

Image taken from nursing crib.com

http://nursingcrib.com/nursing-notes-reviewer/medical-surgical-nursing/renal-problems-%E2%80%93-renal-calculi/