urinary stones

MANAGING UROLITHIASIS

Dr Clarence Lei Chang Moh, 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. There is a slight world wide increase in stone incidence. Managing urolithiasis is an important skill for all doctors.  Diagnosis is usually with urinalysis, ultrasound, plain Xray KUB & noncontrast low dose CT.  Prevention is as important as surgery. Ureteric colic is the most severe pain that men can ever experience and the usual analgesia is  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 by="" cause="" complicated="" do="" eventually="" intervention="" large="" not="" o:p="" require="" sepsis="" stones="" unless="" untreated="" urosepsis.="" usually="" whereas="">

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.

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 stones, eg post ESWL lower pole fragments. In one study Potassium Citrate 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 followed by prophylaxis 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, low oxalate, and normal calcium. Patients with uric acid stones should take less uric acid in their diet e.g. red meat, nuts.

Open surgery for urinary stones now comprises < 5% of surgical treatment eg in large multiple bladder stones in boys, bulky full staghorn kidney stones and giant ureteric stones. The later can  also be removed by laparoscopic surgery. The mainstay of stone surgery is endourology viz ureteroscopic lithotripsy, URS and percutaneous nephrolithotripsy, PCNL.  URS has a successful outcome in >90% cases but can be hazardous in the  upper ureter. The main complications of PCNL are bleeding & sepsis, occasionally fatal. Main energy sources for lithotripsy include  mechanical (“Lithoclast”), ultrasonic and laser. In recent years equipments have become smaller and better enabling miniPCNL, microPCNL and RIRS, retrograde intrarenoscopy.  ESWL, extra-corporeal shockwave lithotripsy remains the most significant advance in stone treatment, suitable for most upper urinary tract stones <20mm .="" achievable="" alara="" and="" as="" clearance.="" eg="" for="" in="" low="" management="" may="" must="" one="" radiation="" rather="" reasonably="" repeated="" require="" sessions="" some="" span="" stenting="" stones="" style="mso-spacerun: yes;" than="" the="" ultrasound="" ureteric="" use="" with="">  surgeon control of fluoroscopy, protection for staff and patient.

Efficient and safe clearance of the stone, with  followup preventive measures are needed for proper management of urinary stones.

College of Surgeons of Malaysia, Kuching, Annual Meeting, 25 May 2014, pages 45-46