UROLITHIASIS

Objectives:1-To list the etiological factors of urolithiasis.2-To manage urinary stones. 3-To enumerate the lines of prevention of stone recurrence.

A urinary stone can be defined as a mass of crystals bound together by cement substance, which is formed of proteins & provides a framework for crystal deposition.

Aetiology:Stone formation is the outcome of the interaction of multiple factors that includes:1. Supersaturation of urine due to antidiuresis or due to excessive excretion of poorly soluble salts in urine, e.g. calcium oxalate, phosphate, uric acid, cosine, or xanthine.2. Deficiency of inhibitors of crystallization e.g. magnesium, pyrophosphate &/or citrates3. Stasis along the urinary tract.4. Infection is an important predisposing factor. Product of infection, e.g. shreds of pus may provide a nucleus upon which crystals may form. In addition, infection by urea-splitting organisms e.g. proteus results in alkalinization of urine, which encourage the precipitation of phosphates.

Composition of Urinary Stones:1. Calcium stones are radio- opaque & constitute about 80% of UT calculi. They occur in the form ofa) Calcium oxalate b) Calcium phosphate

2. Uric acid calculi are radio-lucent & constitute 5-15% of UT calculi.

3. Triple phosphate stones "struvite" are formed of magnesium ammonium phosphate. They are formed only in association with infection &alkaline urine. They are present in 15-20% of cases either alone or a shell around calcium or uric acid nucleus.

4. Cystine stones constitute about 1% of UT calculi. They are faintly radio-opaque they are formed in acid urine in patients who secrete an excessive amount of cystine in urine due to a hereditary metabolic abnormality.

Metabolic abnormalities in calcium stone formers:1. Hypercalciuria is encountered in 65-75% of cases. There are 3 forms of Hypercalciuria: . a) Absorptive hypercalciuria Is the commonest type & is due to enhanced intestinal absorption of calcium. b) Renal or excretory: It is due to diminished renal tubular reabsorption of calcium (renal calcium leak). c) Resorptive hypercalciuria is due to increase bone resorption in patients with hyperparathyroidism or after prolonged immobilization.

2. Renal tubular acidosis. An inherited disorder that results in inability to acidify urine below a pH of 6.5, increased urinary calcium excretion and diminished excretion of citrate in urine enhancing the formation of calcium phosphate stones.

3. Hyperoxaluria is either primary (a rare congenital metabolic disorder) or secondary, the latter may be due to the intake of oxalate rich foods (e.g. boiled black tea, coffee, cola, carbonated beverages & some vegetables) or due to endogenous oxalate production (from metabolism of ascorbic acid).

4. Hyperuricosuria is encountered in 20% of calcium oxalate stone formers (& in all uric acid stone formers). Uric acid crystals act as a nidus upon which a calcium oxalate stone is formed.

5. Hypocitraturia is a common finding among calcium stone formers. Citrate is a potent inhibitor of calcium oxalate & calcium phosphate crystallization.

Metabolic etiology of uric acid calculi:1. Hyperuricemia due to primary or secondary gout (e.g. in case of lymphoma or after the intake of cytotoxic drugs).2. Hyperuricosuria without hyper-uricemia may be due to the intake of thiazides diuretics, salicylates or purine-rich foods.3. Chronic dehydration.4. Persistently high urinary acidity.

Aetiology of bladder stones:Most bladder stones are migrating stones coming down from the kidney via the ureter. Primary bladder stones (formed in situ) are due to:

1. Nutritional deficiencies in children of developing countries, a diet low in protein and phosphate predispose to ammonium acid urate stones.2. In adult men, bladder stones are due to stasis (infravesical obstruction), infection, neuropathic vesical dys-function or foreign bodies (e.g. indwelling catheters).

Aetiology of urethral calculi:Most urethral calculi are formed more proximally & become impacted in the urethra. Primary urethral calculi are rare & are formed in association with urethral diverticula, fistula or foreign body.

Pathology:Urinary tract stones may be single or multiple. Multiple stones are common if there is distal obstruction. The shape of the calculus depends on its location. Staghorn (branched) stones are found only in the kidney while ureteral stones are oblong or oval in shape, whereas bladder is usually spherical.

Urinary tract calculi have a deleterious effect on the kidney & urinary tract via:1. Predisposition to infection: infection in turn, may result in the deposition of phosphate salts on the surface of the primary stone leading to the formation of mixed or lamellated calculi.2. Stasis.3. Infection and stasis result in deterioration of the renal function.4. Calculous anuria results from the simultaneous impaction of stones in both ureters or in the or in the ureter of the sole functioning kidney. This is an emergency condition that leads to acute renal failure.

Fig: Various shapes of kidney stones (calcyeal, pelvic, staghorn)

Clinical features:Symptoms of upper urinary tract stones:1. Renal (ureteric) colic is characteristic of obstructing upper urinary calculi. It is a severe colicky pain that starts in flank or renal angle &

radiates towards the external genitalia. It is usually associated with lower urinary symptoms. It is sometimes accompanied by nausea & vomiting. 2. Dull aching loin pain is due to hydronephrosis secondary to urolithiasis. 3. Calyceal stones are usually asymptomatic until they obstruct the calyceal neck when they cause renal colic and dull aching loin pain. 4. Recurrent infection is common resulting in lower urinary symptoms and urinary turbidity. Acute infection of an obstructed kidney is manifested as fever & rigors. 5. Impacted stones in the intramural ureter give symptoms of vesical irritability: increased frequency, burning urination and urgency. 6. Haematuria, recurrent or persistent is common and is often preceded by renal colic.

Symptoms of bladder or urethral calculi:These include symptoms of vesical irritability such as burning pain on urination, which may be referred to the tip of penis & increased frequency of urination. In children, some itching may be felt at glans penis. Interrupted urinary stream is common in patients with bladder stones. The symptoms of bladder are more evident during day & relieved by rest or sleep.Impacted urethral calculi result in retention of urine and dribbling. The patient may be able to feel stone in the anterior urethra.

Physical signs:In most patients no abnormality can be detected, the renal angle may be tender. The kidney may be palpable if a ureteric calculus is chronically obstructive and resulted in severe hydronephrosis. Fever may be present in association with infection.

Investigations:A- Laboratory: 1. Urine analysis may show haematuria.2. Pyuria and bacteruria are frequent. 3. The type of crystals present in the urine may predict the composition of the stone. 4. Blood urea & serum creatinine give an estimate of the total renal function. B- X-Ray findings:1. A plain film of the abdomen will show radio-opaque calculi (80-90% of all stones). Confusing shadows include phleboli, calcified lymph nodes, fecolith, calcified ovaries or fibroids, foreign bodies and gall

stones. A right lateral view is essential when a radio-opaque shadow(s) is shown in the right renal area. A renal calculus overlies the vertebral bodies whereas gallstones are far anterior.

Plain X-ray showing left kidney stone

2. IVU is essential in all cases so that kidney function can be roughly assessed (transient derangement in cases of acute renal colic). Lucent stones are outlined; opaque stones can be assessed with certainty. A post-voiding film is essential to show ureterovesical and intramural calculi.

Fig: IVU

3. Ultrasonography is valuable during pregnancy, in anuric patients and if the patient is allergic to the contrast material. It shows the acoustic shadow of the stone, stasis or hydronephrosis are also shown.

U/S showing hydronephrosis (arrow head) due to a stone in the renal pelvis (arrow).

Management of upper urinary tract calculi:A- Diagnosis of the presence of the stone (s) and assessment of the condition of the urinary tract (vide supra).B- Emergency treatment of: 1. Renal (ureteric) colic: A combination of antispasmodics (e.g khelline, buscopan, papaverine,) , pain killers (e.g. voltaren, indocid,) given I.M. and diuretics will relieve most cases. Only the exceptional case will need the addition of opiates. A hot water bag on the painful side is beneficial in many cases.

2. Obstructive (Calculous) anuria: i) A short term conservative trial for 12 hours with diuretics (lasix6 amp or 15% mannitol) in addition to antispasmodics is warranted

ii) A plain X-Ray and ultrasonography show the obstructing stone(s) and the condition of the kidneys.

iii) Ureteric catheterization should be attempted in every case: it may succeed to bypass the obstruction and hence to drain the kidney(s).

iv) Urinary diversion above the level of the obstruction is required in most cases by: *Nephrostomy (formal or percutaneous) *Proximal ureterostomy. The obstruction is eventually corrected after stabilization of the renal function.

v) If the obstruction is due to a stone in the upper third or middle third of the ureter, an urgent ureterolithotomy is indicated if the field is fresh and the an experienced urologist is available.vi) In late, uncompensated cases of frank renal failure, Dialysis is indicated before any surgical procedure.

C- Treatment of the stone(s):1. Small stones less than 5mm in diameter usually pass spontaneously aided by adequate hydration: i. Diuretics, e.g. thiazides one tablet daily ii. Antispasmodics e.g. khelline products, hyocine (buscopan) or papaverine(no-spa) .2. Larger renal & ureteric stones can be managed by: a) Extracorporeal shock wave lithotripsy (ESWL) is suitable for stones smaller than 2.5 cm in diameter that are not associated with distal obstruction or active infection.

b) Percutaneous nephrolithotomy is best done under fluoroscopic (X-Ray) control and is suitable for most renal & upper ureteric calculi.

c) Ureteroscopic manipulations are suitable for stones in the lower or middle third of the ureter including:- Extraction of small stones using special forceps or Dormia basket- Disintegration of larger stones by ultrasound or electrohydraulic waves or by the pneumatic lithoclast or by Laser beam.

d) Impacted stones in the intramural ureter can be extracted cystoscopically after transurethral incision of the sub mucosal ureter (ureteral meatotomy).

3. The role of surgery is declining if the above mentioned endourologic facilities are available.a) For renal stones, the kidney is exposed extraperitoneally by a supracostal incision with the patient lying in the lateral position. Pyelolithotomy, i.e. extraction of the stone through an incision in the renal pelvis is the operation of choice.Nephrolithotomy, i.e. extraction of the stone through an incision in the renal parenchyma, is suitable for some calyceal stones which cannot be extracted via the renal pelvis.

Extended pyelolithotomy or pyelo-nephrolithotomy is indicated in branched (staghorn) stones.Partial Nephrectomy, excision of the lower third of the kidney is indicated in case of stone in the lower calyx whose drainage is defective. Nephrectomy should be avoided even in the management of staghorn stones; it is only done for a functionless destroyed kidney, or as a life saving measure because of intraoperative bleeding during renal stone surgery.

b) Surgical management of ureteral stones: Ureterolithotomy is indicated for large stones, stones with distal stricture or after failure of endourologic manipulations. The ureter is usually exposed extraperitoneally through a lumbar exposure, (upper 1/3), an iliac exposure (middle 1/3), or a midline exposure (lower 1/3).

The ureter is mobilized down to the level of the stone. The wall of the ureter is incised directly over the stone that is then extracted by an ureterolithotomy forceps. The ureter is calibrated by an 8 Fr fine plastic catheter to rule out distal obstruction. The wall of the ureter is repaired using 3/0 chromic catgut. The wound is closed in layers with drainage.

D- Prevention of Recurrence of Urolithiasis: 1. General measures, for all types of stones: a) Complete removal of the stone to avoid false recurrence. b) Correction of stasis. c) Control of infection. d) Hydration in order to produce at Least 2.5 liters of urine daily; the patient must drink 500ml water at bedtime to insure nocturnal diuresis.2. Specific measures: depend on the composition of the stone, which must be determined biochemically or by infrared spectroscopy.a) For calcium stones, metabolic evaluation includes estimation of: * 24-hour urinary calcium output (Normally less than 250 mg on a free diet). * Plasma calcium. * Plasma inorganic phosphate. * Parathyroid hormone assay in patients with hypercalcaemia. * Ammonium chloride loading test (or acid loading test) to detect renal tubular acidosis. * 24-hour urinary uric acid output may also be determined as Hyperuricosuria may predispose to calcium stone formation.

Any abnormality should be corrected, e.g.- Surgical treatment of hyperpara- thyroidism -Moderate calcium diet &/or calcium binding agents (e.g. bran, cellulose, phosphate) &/or thiazides for hypercalciuria. -Immobilized patient should be mobilized actively or passively.- Hyperuricosuria is corrected by low purine diet &/or allopurinol.- Potassium bicarbonate or potassium citrate to keep urinary pH at 6.0 to 6.5 in patients with renal tubular acidosis-The Oxalate intake should be minimized; the most important item to be restricted is the boiled strong (black) tea.-The diet should not contain an excessive amount of salt, sodium chloride enhances the intestinal absorption of calcium.

b) For uric acid stones, the plasma uric acid is to be estimated (normally below 7 mg/100ml) and also the urinary output of uric acid (normally less than 800mg/24hours). Hyper-uricaemia and hyperurisuria are treated by allopurinol (e.g. Xyloric) 100-300 mg daily. A low purine diet is advised; avoid liver, spleen, lungs, and sweet berries in addition to the limitation of red meat consumption. The urinary pH should be kept at 6.0-6.5 by sodium bicarbonate & potassium citrate.

Management of Lower Urinary Tract Calculi: A- Diagnosis:1. Symptomatology (vide supra).2. Physical signs: huge bladder stones (rare) can be palpated suprapubically or bimanually, posterior urethral calculi can be felt rectally whereas anterior urethral calculi can readily be felt along the bulbar or penile urethra. Stones in the fossa navicularis can be seen through the external meatus.3. X-Ray: the plain X-Ray should include the lower border of the symphysis pubis in order to detect posterior urethral calculi. Radio-opaque stones in the bladder or posterior urethra are easily demonstrated. Associated calculi in the upper urinary tract can also be seen. IVU &/or Ultrasonography are essential to assess the upper urinary tract to demonstrate radiolucent calculi, to detect residual urine and to diagnose infravesical obstruction, e.g. BPH.4. Cystourethroscopy is indicated in some cases to visualize the stone(s) and to assess any associated condition in the lower urinary tract , e.g. bladder neck obstruction, prostatic lesions, bladder tumors or diverticula.

B- Treatment of lower urinary tract calculi:1. Bladder stones:

Medium sized stones (1-2 cm in diameter) can be crushed by lithotrite and the fragments are evacuated by Ellik (Bigelow's) evacuator. The operation is called litholapaxy. It is contraindicated in cases of large calculi, urethral stricture or in the presence of other lesions that necessitates open surgery e.g. huge prostate, bladder tumor or retentive bladder diverticula. In such cases the bladder stone can be removed surgically, the operation is termed cystolithotomy. The bladder is approached extraperitoneally through a suprapubic midline incision. After removal of the stone, the bladder is closed by 2/0 or 3/0 chromic catgut; the wound is closed in layers with drainage of the retropubic space.

2. Urethral calculi:a) Posterior urethral calculi are cautiously pushed back by a urethral sound or by a urethroscope to the bladder to be treated as bladder calculi.b) Impacted stones at the fossa navicularis can be extracted by doing meatotomy of the external urinary meatus.c) Bulbar urethral stones can be extracted through the perineum (bulbar urethrolithotomy).d) Stones in the penile urethra are pushed back to the bulbar urethra and treated as such. They should never be pulled through the external meatus; this wrong technique will almost always result in a tight urethral stricture. If the stone is impacted, suprapubic cystostomy is done to relieve the retention of urine; the stone will be disimpacted within a few days. Penile urethrolithotomy should never be done; it will often be complicated by a urethral fistula &/or stricture.