Dealing with Urolithiasis in Primary Care

DEALING WITH UROLITHIASIS IN PRIMARY CARE,

MIMS GP Workshop, Sandakan, 22 September 2013

by Dr Clarence Lei Chang Moh; email: clarencelei@gmail.com

Urinary stones affect 5 – 15% of populations (commoner in young men), with a 50% recurrence rate over 10 years. Ureteric colic is the most severe pain that men experience.  In addition, urinary stones cause a variety of symptoms including backache, suprapubic discomfort, dysuria and haematuria.

A basic investigation in any clinic is that of a urinalysis. I use a urinalysis machine with a print-out, charged at the  PHCSA rate of RM10. Metabolic investigations to establish the cause of the stone include the following: serum calcium, serum uric acid, serum creatinine, urinalysis and urine culture. About 1% of patients coming to a stone centre for lithotripsy are found to have hypercalcaemia due to primary hyperparathyroidism.  Urinary stones are confirmed by imaging. The initial imaging is usually that of an ultrasound of the urinary tract, which readily pick up stones in the kidneys and bladder.  Small stones in the ureter can be seen almost instantly with non-contrast CT urography, low dose radiation.  IVP is outdated unless CT is not available. I also ask for a KUB as baseline for follow-up. In older patients, bladder stones may be due to associated BPH, benign prostatic hyperplasia.

Medical therapy and stone prevention is mainstay of therapy in general practice. The preferred analgesia for ureteric colic is diclofenac rather than an opiate, which  causes sedation. Patients who are allergic to diclofenac may be given tramadol. Diclofenac is nephrotoxic, if used for more than a week.  For passage of ureteric stones the lower ureter may be relaxed  by  MET, medical expulsive therapy. This consists of alpha-blockers e.g. prazosin 1 mg bd, terazosin 2mg ON.  This is  taken at night to reduce postural hypotension.  Stones smaller than 6 mm do not usually require surgical intervention unless complicated by sepsis. Large untreated urinary stones will  eventually cause urosepsis.

The most 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.  There is no good evidence of advantages of specific juices or herbals.  A diet suitable for a recurrent stone former is one with less salt, less uric acid (red meat, nuts, protein), less oxalate (chocolate, spinach, concentrated tea) and normal calcium.

Uric acid stones can be effectively dissolved by medical therapy through urinary alkalinisation, keeping the pH around 7.  Uric acid stones comprise of about 20% of stones and are radiolucent but readily seen on ultrasound and non-contrast CT.  Even staghorn calculi of uric acid can be dissolved over a period of 6 months.  However, the patient should have good renal function to avoid accumulation of  potassium in PotCit and sodium  in sodium citrate.  Citrate in the urine reduces crystallisation of the calcium and uric acid and increases the stone free rate following lithotripsy, from 45.5% recurrence to 12.5% compared to a controlled group, over a 12 month period.

Stones may also be associated with infection especially in ladies; infective stones are faintly radio-opaque.  Stone and infection should be cleared by surgery, vigorous antibiotic therapy and followed by prophylaxis e.g.  nitrofurantoin 50mg on night for 6 months. In Malaysia stones are also not uncommon during pregnancy.  Unfortunately, radiation and lithotripsy are contraindicated in pregnancy. Obstructed ureters during pregnancy can be drained  with a percutaneous nephrostomy or ureteric stent, until the baby is delivered.

Indications for referral to a urologist would include: persistent severe colic for more than 48 hours, fever above 38ºC indicating urosepsis, stones which are large or multiple. Most stones are removed by ESWL, extracorporeal shockwave lithotripsy or endoscopic lithotripsy viz ureteroscopy or percutaneous nephrolithotripsy.  Only 5% of stones require open surgery eg huge stones or bladder stones in children, the later to avoid injury to the small urethra.