MODERN MANAGEMENT OF URINARY STONES

By: Dr Clarence Lei Chang Moh,

 

KEY WORDS:  ESWL, extra-corporeal shockwave lithotripsy; PCNL, percutaneous

    nephrolithotripsy; URS, ureterorenoscopy; UTI, urinary tract infection.

Introduction:

Urinary stones occur in up to 15% of men in a “stone-belt” region like Malaysia; the incidence in women is 1/3 of men (1, 2). Paediatric urolithiasis is also common in Malaysia (3). Urinary calculi accounts for 1/3 of admissions to local urological units. A ureteric colic is reputed to be the most severe pain a man can ever experience.  However, pain is only manifested during the acute pathophysiological response.  Chronic obstruction and infection can be “silent”, giving patients a false belief that their traditional therapy has removed the stones.  The natural history of progressive stone disease followed up for years is urosepsis associated with mortality (4). Unfortunately, stones causing obstructive uropathy is still an important cause (2%) of renal failure in Malaysia (5).  It is therefore important that urinary stones be treated, especially when there are many modern modalities available.  Urinary stone disease is therefore an important topic in the curriculum of the family physician.  Patients already can access numerous websites (e.g. by MUA, Malaysian Urological Association, UCLA, University of California LA) with detailed information on stones as well as the choice of urological techniques.

Site and type of stones: 

Stones can be found in any part of the urinary tract (Fig. 1). 90% of stones are radio-opaque; ultrasound or spiral 5 mm. CT can detect the rest.  In the presence of normal blood urea, precise location and renal function is usually confirmed by IVU, intravenous urogram. The presentation, treatment and outcome depend partly on the site and size of the stone.  Ureteric and urethral stones cause more pain and renal damage because of obstruction.  Treatment and prophylaxis also depend on stone types (Table 1)(6).

Kidney stones:

Kidney stones can be located in the renal pelvis or calyces.  Such stones can cause pain by obstruction and haematuria e.g. on exercise.  These two types of stones are suitable for ESWL. Stones > 2.5 c. in size requires the endoscopic insertion of a pre ESWL ureteric stent to prevent ureteric obstruction by fragments.  Delay in treatment allows most kidney stones in Malaysia to grow and converge to become “staghorn” type in configuration.  The bulk of such a staghorn calculus and stones > 3.5 cm. will need to be removed by a more invasive technique like PCNL (8, 9). Up to 60% (7) of PCNL patients need ESWL for residual fragments not accessible through the percutaneous tract (Table 2). In bilateral renal calculi, the better kidney should be operated first (10). Hard stones more than 5 cm. in size, especially with an extra-renal pelvis may be more efficiently removed by open pyelo-nephrolithotomy. Nephrectomy is occasionally necessary when the kidney is non-functioning and becomes a source of recurrent septicaemia.

Ureteric stones:

Ureteric stones are most likely to be symptomatic in the acute phase because of obstruction.  The typical “renal” colic of loin to groin pain associated with haematuria is actually due to an ureteric stone.  In chronic obstruction, there is little pain.  In experimental complete ligation of the ureter in piglets, there is almost complete and irreversible loss of renal function after 2 weeks.  In stone disease, the obstruction may be partial but associated infection also causes renal damage.  In a febrile patient, the stone should be urgently bypassed with an external percutaneous nephrostomy (under LA) or with an internal temporary (< 6 months) ureteric double J-stent under anaesthesia. Proximal ureteric stones can be treated with ESWL (success about 70%) but distal ureteric stones can be more reliably (almost 100% success nowadays) (11) fragmented by ureteroscopic (URS) lithotripsy (12, 13).  Ureteric stones are classified as proximal if proximal to iliac vessels (around L5/S1) [Table 3].  Blind basket extraction, without fluroscopic control and guide wires, is not recommended. Previously, about 30% of ureteric stones are removed by open surgery (14). Large ( >2.5 cm.) ureteric stones can occasionally be removed intact by open surgery which also cost less than ESWL or URS.

Bladder stones:

Bladder stones may be primary or secondary to outlet obstruction or catheters. Bladder stones accounts for up to 30% of stones in developing countries like Malaysia (15).  Primary bladder stones occur in the young (< 40 years of age) including children.  The classical presentation is that of intermittent dysuria, haematuria and bladder outlet obstruction.  The obstruction to urine flow can be relieved by a change of posture, as the stone is shifted away from the bladder outlet.  ESWL of bladder stones is feasible (16) but not preferred because of cost and other easier methods.  Most bladder stones can be removed endoscopically after fragmentation by forceps or lithotripsy.  Large ( > 5 cm) or multiple bladder stones are more reliably removed intact by open surgery.

Stones in children:

With miniaturization of modern instruments, stones in children can almost be treated as in adults (17).  Moreover, the ureter in children can distend to accommodate the range of adult sized fragments.  However, large (e.g. >1 inch) bladder stones in small children in developing countries are more efficiently removed by open surgery. This can also bypass the inevitable urethral trauma and possible long term urethral stricture.

Stones in pregnancy:

Ureteric stones can complicate the existing predisposition to hydronephrosis and pyelonephritis of pregnancy.  As radio-contrast studies and ESWL are contraindicated during pregnancy, treatment is usually done with the help of ultrasound localisation and endoscopic lithotripsy (18, 19).  Occasionally open surgery, diverting nephrostomy tubes or ureteric stents had to be used, especially if a febrile UTI persists.

ESWL  & lithotripsy:

Patients often ask for “laser” therapy for their stones.  In fact, “laser” is not suitable for extra-corporeal treatment as it destroys tissue i.e. it cuts or burns!  Extra-corporeal therapy uses shockwave lithotripsy (ESWL) in which thousands of shockwaves are produced from a source outside the body and focused on the stone (Figure 2).  ESWL was first introduced by Dornier in 1980 and rapidly became easily suitable worldwide in compact versions (20).  The stone target is localised by ultrasound or x-rays and ESWL is applied over a period of about an hour.  Laser can be used directly on the stone e.g. via an endoscope (Figure 3).  However, there are much cheaper and more reliable energy sources e.g. mechanical energy (viz. by “Lithoclast” probes). The success of ESWL depends mainly on the size and partly on the location of the stone.  Lower calyceal stone fragments are dependent and do not clear well.  Mid-ureteric stones are obscured by the nearby bone and difficult to localise.  The success of ESWL range from 90% (renal pelvis stone < 1 cm.) as in Table 4 (21). More than one treatment is often necessary for stones >1 cm. (35.6% retreatment rate in lower calix).  Parenteral analgesia is often needed for ESWL.

Complications:

Complications of stone treatment include bleeding, infection and obstruction of the ureter by stone fragments (so called “steinstrasse” or stone street in German).  A coagulation profile and urine culture has to be done pre-ESWL.  Light haematuria for a few hours is seen in almost all patients.  Bleeding can occasionally manifest as peri-renal haematoma. If there is fever, parenteral antibiotics had to be given and ESWL suspended.  It is an unrealistic expectation that stones treated by lithotripsy will “vanish” with 1 session.  The fragments have to pass out by urine flow (i.e. the kidney has to be functioning) and this causes pain and haematuria.  If the stones get stuck in the ureter for >2 weeks, or if there is fever, urgent treatment is necessary as for ureteric stones.  ESWL can rarely cause death by splenic rupture (22) or rupture of nearby calcified vessels e.g. splenic or aorta (23).  Other rare complications include peri-renal haematoma, ileus, pancreatitis, pneumonitis and cardiac arrhythmia (21).

The list of contraindications for ESWL are as in Table 3.

Complications of endoscopic lithotripsy are similar plus the risk of instrumental perforation of the urinary tract and haemolysis through absorption of the irrigating fluid.  PCNL involves puncture of the kidney and the risk of bleeding is a little higher (3.6% needs blood transfusion) (24).

Metabolic work-up:

Chronic dehydration is the most important cause of stones.  For paediatric stones, recurrent stone formers, large or multiple stones and familial stones, it is important to rule out other underlying causes.  Serum PTH (parathyroid hormone) should be assayed if there is hypercalcaemia.  Surgical removal of the hyperactive parathyroid nodule will cure the hypercalcaemia. UTI is an important cause of stones, especially in females.  Infective stones usually consist of magnesium, ammonium, phosphate and are of the staghorn type.  Uric acid stones are radiolucent and patients may have gout as well.  Cystine stones are faintly radio-opaque and are familial. The basic metabolic work-up includes serum for calcium, uric acid and urine culture.  The stone can be sent for analysis.  For a more detailed work-up, a 24-hour urine collection can be sent for quantitative analysis of calcium, uric acid, oxalate and qualitative analysis for cystine. Calcium deposits in the dilated collecting tubules at renal papilla give rise to MSK, medullary sponge kidney.  Recurrent calcium stones, metabolic acidosis with paradoxical alkaline urine should alert one to the diagnosis of RTA, renal tubular acidosis. Cystinuria and hyperoxaluria are inherited in a autosomal recessive manner. Underlying structural abnormalities (e.g. diverticulum) and voiding dysfunction would be detected by IVU.

Spontaneous passage of stones:

Stones < 5 mm. in size has a 98% chance of spontaneous passage (13).  Nevertheless, some do not pass and all patients have to be followed up with KUB and renal ultrasound to rule out silent increase in hydronephrosis.  Female can pass out bigger stones as the ureters are dilated by hormonal changes of pregnancies and especially if there is a history of previous stone passage.  Spontaneous stone passage may be hastened by liberal intake of fluids.  Excessive fluid has been known to cause heart failure in the elderly and hyponatraemia requiring admission to ICU! 2 litres of urine output per day is sufficient to prevent stone formation.  The intake of fluid therefore depends on the patient’s environment and usually should not exceed 3 litres per day.  Diuretics (e.g. Frusemide and many Chinese preparations) were often prescribed but their use can cause hyponatraemia. 

Medical therapy:

Parenteral NSAID (nonsteroidal anti-inflammatory drug e.g. Diclofenac 75 mg ) is the standard treatment for severe colic.  This can be followed by the oral or rectal suppository forms.  Continuous usage should be limited to 3 days because of its nephrotoxic and ulcerogenic potential.  Narcotic analgesics are used as second line because of its side effects of sedation and nausea. Narcotics can also be abused.  Anti-spasmodics (e.g. “Buscopan”) are not effective for pain relief and causes gut paralysis with abdominal distension.

Medical therapy is possible in some cases and important for stone prevention.  Staghorn calculus of uric acid (mostly radiolucent) can be dissolved by urinary alkalinisation (keep urine pH 7-8 with potassium citrate (e.g. Mist Pot. Cit. or tablet “Urocit-K”) or sodium bicarbonate (e.g. “Ural” powder). Mist Pot. Cit. may contain too much glucose for diabetics. Hyperuricaemia can be reduced by oral Allopurinol 300 mg daily.  In patients with renal impairment, the serum potassium and sodium has to be monitored.  Alkalinisation also helps in cystine stones.  In recurrent cystine stones, Penicillamine may be used for dissolution therapy.  Infection must be cleared by therapeutic courses of antibiotics.  In recurrent UTI, a nightly dose of mild antibiotic (e.g. Trimethoprim) for 3-6 monthly is useful for prophylaxis.

Prevention and Follow-Up:

Urinary stones recur in > 50% of patients unless preventive measures are taken.  These include:

(a)    liberal fluids to produce 2 litres urine per day

(b)   normal serum uric acid level by dieting and Allopurinol, if necessary

(c)    normal serum calcium level; exclude hyper-parathyroidism

(d)   sterile urine.  Add nightly dose of antibiotic (e.g. Trimethoprim) for prophylaxis, if necessary

(e)    diet without excessive calcium (dairy products), oxalate (nuts) and urates (e.g. red meat)

(f)    in recurrent uric acid or calcium stone-formers, urinary alkalinisation with addition of citrate stone inhibitor (25) is helpful.

Minimally invasive therapy often produce residual fragments that require follow-up.  Follow-up KUB and/or ultrasound are done a few days after treatment.  Treatment (e.g. ESWL) is repeated till fragments are < 5 mm. Thereafter, imaging may be done at 2-4 weeks’ interval till all fragments have cleared. Twenty percent of local patients failed to return for the necessary follow-up upon review at 3 months (5).  Regular follow-up is therefore essential to prevent silent obstructive uropathy and to apply ESWL before it becomes >2 cm.  Most stone-formers can be followed up by clinic urinanalysis and ultrasound.

Summary:

Urinary stone disease can be diagnosed in the acute phase (pain and haematuria) or in the chronic phase on health screening (urine, ultrasound, x-ray).  Stone removal is usually by minimally invasive techniques like ESWL, PCNL, URS with open surgery reserved for large, multiple or hard stones.  Metabolic measures and regular follow-up can reduce morbidity and renal loss.

Table 1 : Kidney Stone Types (2, 6)

Stone Composition	Percentage of total
Calcium oxalate	60
Calcium phosphate	6
Magnesium Ammonium Phosphate Struvite (infection stones)	17
Uric acid	15
Cystine	2

Table 2 : Kidney Stone Treatment

 

Size (mm.)	Treatment
5 - 25	ESWL
25-35	ESWL + J stent
> 35	PCNL ± ESWL

 

Table 3 : Ureteric Stone Treatment

Site	Treatment
Proximal	ESWL
Distal	URS

TABLE 4 : Re-treatment and stone-free rates after ESWL, stratified by stone size

Location	Re-treatment Rate*		Stone-Free Rate+
	œ 1 cm.	> 1 cm.	œ 1 cm.	> 1 cm.
Pelvis	17/493 (3.4)	40/507 (7.9)	316/351 (90)	273/331 (82.5)
Upper calix	3/95     (3.2)	7/63     (11.1)	53/69     (77)	29/40     (72.5)
Mid calix	5/126   (3.9)	4/36     (11.1)	61/76     (80)	13/19     (68.4)
Lower calix	4/428 (0.93)	52/146 (35.6)	253/317 (80)	66/122   (54.1)

Values are given as number of patients/total (per cent).

*  1,894 patients treated.

+ 1,325 patients with 3-month follow-up.

Ref. (20)

TABLE 5 : Contraindications of ESWL

1.	Pregnancy
2.	Coagulation defects uncorrected.
3.	Febrile UTI
4.	Unrelieved obstructed kidney or calyx
5.	Non-functioning kidney
6.	Nearby vascular calcifications or aneurysm
7.	Stone cannot be focused (e.g. patient too small or too big or deformed)
8.	Stone too big (e.g. Staghorn) or too hard (e.g. calcium-oxalate monohydrate, cystine).
9.	Not a stone e.g. calcification of kidney or tumour.
10.	Uncontrolled medical conditions e.g. hypertension.
11.	Supporting endo-urological expertise not available.

References:

1.              Robertson G. Urinary tract calculi: In Nordin BEC, Need AG, Morris HA, eds.

Metabolic bone and stone disease.  New York: Churchill Livingstone, 1993:49-311.

2.         Pak CYC, Resnick MI, Preminger GM: Ethnic and geographic diversity of stone disease.  Urology; 50(4): 504-7, 1997.

3.         C C M Lei, P Mah, H W Yap et al: Paediatric Urolithiasis. Mal J of Child Health, 8.1: 121-123, 1996

4.              Singh M, Chapman R, Tressider GC, Blandy J: The fate of the untreated staghorn calculus. Brit J. Urol. 45: 581 – 585, 1973

5.              Tan HM, Cheung SH:  Experience with 395 ESWL in the treatment of renal and ureteric calculi Med J Mal. 45(2); 113-117, 1990

6.              Mobley D F, Baum N H:  Nephrolithiasis: a practical approach to diagnosis and treatment. Hosp. Med. 21-26 Feb 1999.

7.              Tan H M, Cheung S H:  Percutaneous renal surgery for urolithiasis.  Med J Mal. 45(2) 118 – 122, 1990.

8.         Lam H S, Lingeman, JE, Mosbaugh PG et al: Evolution Of The Technique Of Combination Therapy For Staghorn Calculi: A Decreasing Role For Extracorporeal Shock Wave Lithotripsy.  J Urol 148 1058-1062, 1992

9.              Segura JW, Preminger GM, Assimos DG, et al: Nephrolithiasis clinical guidelines panel summary report on the management of staghorn calculi.  J Urol 1994; 151: 1648-1651.

10.           Sreenevasan G.: Bilateral renal calculi: Ann r Coll Surg. Engl. 55: 3-12, 1974.

11.           Tan HM, Liew RPC, Chan CCW et al: Multimodal Approach in the Management of 1163 ureteric stone cases.  Med. J. Mal 50(i): 87-92, 1995.

12.           Liong ML, Clayman RV, Gittes RF et al. Treatment Options for Proximal Ureteral Urolithiasis: Review And Recommendations: J Urol.

13.           Segura JW, Preminger GM, Assimos DG et al: Ureteral Stones Clinical Guidelines Panel Summary Report On The Management Of Ureteral Calculi. J Urol 158, 1915 – 1921, 1997

14.           Sreenevasan G: Ureteric Stones – When and what to do? – that is the question.  S.E.A. J. Surg. 5 (1): 79-86, 1982.

15.           Sreenevasan G: Incidence of urinary stones in the various states of mainland Malaysia.  Med. J. Mal. 36(3): 142-147, 1981.

16.       P E P Ng, C S Lim, K Abdullah, C C M Lei. ESWL for Bladder Stones.  J. Endourology, 1992: 6.4: M-23

17.       Vandeursen H, Devos P, Baert L. Electromagnetic Extracorporeal Shock Wave Lithotripsy In Children.  J Urol 145: 1229 – 1231, 1991

18.           Denstedt J and Razvi H: Management Of Urinary Calculi During Pregnancy.

J Urol 148, 1072 – 1075, 1992

19.       Scarpa RM, Lisa AD, Usai E: Diagnosis And Treatment Of Ureteral Calculi During Pregnancy With Rigid Ureteroscopes.  J Urol 155: 875 – 877, 1996

20.       Teh C L, Aslan P, Preminger G M: What’s new in shock wave lithotripsy?  Contemp. Urol 9(10): 26-36, 1997

21.       Lingeman JE, Woods J, Toth, PD et al: The Role Of Lithotripsy And Its Side Effects.  J Urol 141: 793 – 797, 1989

22.       Rashid P, Steele D, Hunt J: Splenic Rupture After Extracorporeal Shock Wave Lithotripsy. J Urol 156, 1756 – 1757.

23.           Taylor JD, McLoughlin GA. Parson K F: Extracorporeal shock wave lithotripsy induced rupture of abdominal aortic aneurysm. BJU 76. 262-3, 1995

24.  Tan HM, Ng PEP:  Upper Pole Tracts in 442 PCNL Cases.

J. Endo. 12(1): S115, 1998.

25.           Lee YH, Huang WC, Tsai JY, Huang JK: The efficacy of potassium citrate based medical prophylaxis for preventing upper urinary tract calculi: a midterm followup study.  J Urol May: 161(5): 1453-1457, 1999.

About the Author

Dr Clarence Lei Chang Moh,

MBBS(Mal.), FRCS (Glasgow), FRCS Urol (UK), FEBU, FAMM

Consultant Urologist,

Kidney & Urology Centre, Normah Hospital, 93050 Kuching

Annual Magazine, Academy of  Family Physicians, Sarawak Branch, 2002: 28-35 

Updated 2 Oct 2013