Urinary Tract Calculi

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Urinary Tract Calculi


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EPIDEMIOLOGY OF STONES

Sex: men are affected thrice as

commonly as women.

Age : Peak incidence is between 3

rd

to5th decade.

Race ; Whites are affected 4 to 5times in comparison to places.

Urolithiasis is a life long disease withan average of 9 year interveningbetween episodes.


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ETIOLOGY AND PATHOGENESIS

Development of stones in urinary tract is a complex, poorlyunderstood multifactorial process.

Supersaturation

Ovur abundance of solute in solution.

This occurs fairly well for uric acid, cysteine and xanthinecalculi.

Inhibitiory substances in urine that black crystallization eg :Pyrophosphates, citrate, zinc, magnesium; lack of sufficient

urinary inhibition may cause precipitation of stones.

Matrix : Non crystalline mucoprotein often associated withurinary calculi. Pure matrix calculi may be seen in associationwith proteus infection.

Exogenous substances like indinavir and Triamterene may leadto formation of stones.


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STONES OF THE UPPER URINARYTRACT

Clinical presentation :

Usually silent.

When stone moves within urinary tract it produces eitherhaematuria, or some degree of urinary obstruction which

may be accompanied by pain, urinary infection,generalized sepsis, nausea or vomiting.

Sudden onset, severe colicky in flanks or abdominal painwhich may radiate to groin, testis , or tip of penisdepending on the location of obstruction.

Gross or microscopic haematuria.


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Diagnosis :

Initial evaluation includes urinalysis, urine cultureand plain x-ray of KUB.

Renal ultrasonogram demonstrates the presence ofstone along with any evidence of hydronephrosis ifpresent.

Axial spinal CT confirmes the presence of calculus,and demonstrates the degree of obstruction.

Spiral CT is rapid, does not require bowelpreparation and avoids use of IV & it has graduallyreplaced IVU as primary imaging modality for acuterenal colic.


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URINARY CALCULI AND COMPOSITION,FREQUENCY AND ETIOLOGIC FACTORS

S.No. Type of Stone Frequency Effect of pH Etiologic Factors

1.

a.

b.

c.

2.

3.

4.

5.

Calcium stones

Oxalate

Phosphate

Oxalate and Phosphate

Oxalate and Phosphate

Struvite

Uric acid

Cysteine

Other

Matrix

Xanthime

Triamtene

80%

35%

10%

35%

10%

8%

1%

1%

Solubility

Little effect

Increased at pH 7.5

Supersaturation of urine with

calcium due to

1.Renal leak

2.Intestinal absorption.

3.Bone resorption.

Alkaline urine due to urea

splitting organisms.

Hyperuricosuria

Cystinuria

Alkaline urine due to urea

splitting organisms


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Treatment :

Depends on size, location, degree of obstruction and patients clinicalstatus :

Common sites of stone impaction are :

Ureteropelvic junction .

Pelvic brim where ureter crosses pelvic vessels.

Ureterovesical junction.

Patients with infection in high grade obstruction require promptintervention in the form of retrograde ureteral catheter orpercutaneous nephrostomy drainage.

About 90% of ureteral calculi measuring less than 4 mm passspontaneously whereas only 20% of calculi measuring more than 6mm pass.

Expectant treatment in indicated in asymptomatic, non obstructed, noninfective with stone size less than 4 mm diameter in the lower third ofureter.


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Treatment :

Patient is asked to drink copious amount of water, four to six weeksduration is allowed for passage of stone.

Stone extraction is indicated for ureteral stones that do not passspontaneously.

Small stones may be grasped directly or engaged in stone basket andextracted. Longer stones may be fragmented using ultrasound,electrohydraulic, pneumatic or laser lithotripsy.

Shock wave lithotripsy is advantageous for urethral stones less than 8mm diameter. It may be performed with or without a stent or long asstone can be adequately visualized.

Patients are often placed in prone position for distal ureteral stones. Ureterolithotomy is rarely needed given the high success rate of non-

operative and minimally invasive technique like SWL, ureteroscopy andlaparoscopy.


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BLADDER STONES

Clinical presentation

Pain felt in hypogastrium or referred to penis.

Intermittent stream.

Dysuria.

Haematuria.

Recurrent urinary tract infections.

Commonly found in male patients of westernworld and increase the risk of sqaumousmetaplasia or carcinoma in long standing case.


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BLADDER STONES

Diagnosis :

Plain x-ray of KUB

Bladder ultrasonography Cystoscopy

Treatment : Lithotrites : Mechanical devices that

permit crushing of large, hard,

bladder stones, under direct vision. Itshould be done onl with bladder


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BLADDER STONES

Treatment :

Lithotrites : Mechanical devices that permit crushing of large,hard, bladder stones, under direct vision. It should be doneonly with bladder partially filled to prevent bladder wall injury.Fragments are then worked out through a resectoscopesheath.

Electrohydraulic Lithotripsy : Hydraulic shock wave is producednear stone that usually produces fragmentation after deliveryof several shocks.

Ultrasound Lithotripsy is based on ultrasound energy delivered

through a rigid probe passed through an endoscope causingfragmentation of stone which is removed by continous suction.

Cystolithotomy : It is performed through a small suprapubicincision. It has advantage of removing the entire store ratherthan leaving the fragments inside the bladder.


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RECURRENT STONE DISEASE

Diagnosis :

Predisposing factors can be found in 80% ofrecurrent stone formation. Passage of single

stone is an indication of screening studyincluding determination of serum calcium,phosphorus, uric acid and 24 hourly urinarycreatinine, calculi phosphorus, uric acid andoxalate levels.

Patients found to have any abnormality shouldhave an extensive evaluation.


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RECURRENT STONE DISEASE

METABOLIC EVALUATION :

Baseline studies already mentioned are performed & alongwith recording of urinary patient.

Dietary restriction of calcium to 400 mg and 100 mEq of

sodium for 1 week is done, followed by urine and serumstudies as previously described.

CALCIUM LOADING :

After on overnight fast during which only distilled water ispermitted patient reports at the clinic at 7 am.

First urine sample is discarded, a 2 hour pooled specimen iscollected from 7 to 9 am.

Patient receives 1 gm of calcium gluconate orally at 9 amand collected of the urine specimen from 9 am to 1 pm indone.


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HYPERCALCIURIA

Resorptive hypercalciuria : Constant hypercalcuriaregardless of dietary restriction. Hyperparathyroidism isa common cause and causes calcium urolithiasis. Othercauses include neoplasm metastatic to bone, multiple

myeloma, immobilization, Cushings disease etc.Treatment is by correction of the underlying disorder.

Absorptive Hypercalciuria : It is the most common causeand is responsible for formation of stones in more than50% of patients.

These patients have an exaggerated intestinalresponse to vitamin D leading to hyperabsorption ofingested calcium. Urinary calcium normalizes onrestriction of oral calcium and increases to abnormalrange under calcium loading.


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HYPERCALCIURIA

Treatment :

Diet and hydration.

Patients should be placed on a diet restricted to 400 mg of calciumper day & 100 meq of sodium per day.

Addition of bran in useful as it binds calcium in the gastro

intestinal tract.

Drinking of 3 to 4 litres of water daily to reduce urinary concentrationof calcium.

Cellulose phosphate : It is a calcium binding resin that exchangessodium for calcium in the gastrointestinal tract. It must be used inconjunction with calcium restricted diet.

Orthophosphates : They act by decreasing urinary excretion of calciumand increasing excretion of citrate and pyrophosphate both of whichact to inhibit calcium stone formation.

Renal Hypercalciuria : This disorder is caused by inability of kidney toabsorb calcium from tubular fluid. Thus, placing the patient on calcium

restricted diet will not reduce loss of calcium in the urine. Calcium

loading may increase urinary calcium even further.


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HYPERURICOSURIA

Pure uric acid stones account for approximately 10% of calculi. Uric acidbecomes insoluble in urine at pH less than 5.8.

ETIOLOGY :

Approximately 25% of patients with uric acid calculi are found to havegout.

However most of them neither have hyperuricemia or hyperuricosuria.

Calculi are probably caused by constantly acidic urine, dehydration orboth.

Treatment :

Hydration : Oral intake of atleast 3 litres water daily.

Alkalinization of urine is usually achieved by oral or I.V. sodiumbicarbonate.

Reduction of uric acid load may be achieved by dietary restriction anduse of allopininol. It is indicated in patients urine passive to hydrationand alkalination of urine, who have meloproliferative disorders, thosereceiving chemotherapy.


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HYPEROXALURIA

Oxalic acid is an extremely insoluble end product of metabolism.

Primary hyperoxaluria : Autosomal recessive disordercharacterized by early onset of nephrocalcinasis due to enzymaticdefect. Widespread deposition of oxalate in the kidneys and othersoft tissue eventually occurs. Pyridoxine daily has reported

reduction in oxalate excretion in some patients.

Enteric Hyperoxaluria : May occur in patients with malabsorptionfrom any cause like inflammatory bowel disease, small bowelbypass surgery. Increased amount of fatty acids in bowel bindscalcium leaving increased oxalate for absorption. Treatmentincludes low oxalate, low fat diet with oral fluid hydration and

calcium supplementation. Cholestyramine binds oxalate and hasgood results in patients with malabsorption.

Exogenous hyperoxaluria : When substances metabolized tooxalate are ingested in large quantities such as ethylene glycol, ascarbolic acid etc.


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STRUVITE STONES

Composed of magnesium ammonium phosphate andcarbonate.

They may grow to fill the entire renal pelvis and collectingsystem.

They form when urinary pH is markedly elevated and increasedconcentration of ammonia, carbonate & bicarbonate arepresent in the urine. Such conditions are caused by ureasplitting organisms producing urease enzyme. Proteis speciesare most common with others like Klebsiella, pseudomonasetc.

Female are affected more in ratio of 2:1 as compared to males Other at risk group are spinal cord injury patients, patients

having indwelling catheter for many year, patients with ilealconduit and other supravesical diversions


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STRUVITE STONES

Diagnosis :

Struvite stones should be suspected inany patient with high urinary pH causedby infection.

Plain X-ray of KUB will usuallydemonstrate the calculi.

IVU should be performed to determinewhether obstruction is present and

causing persistence of infection.


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STRUVITE STONES

Treatment :

Aim of treatment is to achieve complete elimination of stones,correction of any obstruction and eradication of infection.

Surgical Modalities :

Nephrolithotomy.

Nephrectomy in case of little or no renal function.

Partial staghorn causing renal parenchymal damage requirespartial nephrectomy.

Percutaneous lithotripsy : Recently it has replaced open surgery inmany patients and approximately 85% of patients can be renderedstone free at 3 months.

ESWL : ESWL alone produces stone free rates in range of 40 to60% and multiple treatments are usually required. Sandwichtechnique used effectively involves percutaneous lithotripsy,followed by ESWL followed by secondary percutaneous lithotripsy,extraction on chemolysis.


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STRUVITE STONES

CHEMOLYSIS :

Generally ineffective in calcium stones but can be used veryeffectively to dissolve uric acid, cysteine, struvite and carbonatestones.

Uric acid and cysteine stones : They are readily soluble in alkaline

solution by local irrigation through urethral or ureteral cather /Nephrostomy. Uric acid stones can be treated with solution ofsodium bicarbonate in normal saline. Oral alkalinizing agent such aspotassium citrate are better tolerated for long term maintenance ofan alkaline pH. Cysteine stones may be treated with solutioncontaining acetylcysteine, sodium bicarbonate and normal Saline.

Struvite and carbonate apatite calculi. They are amenable todissolution by acidic solution having pH of less than 5.5. The mostwidely used solution is 10% hemiacridin delivered to store vianephrostomy tube or ureteral catheter. Normal saline infusionshould be done priorly to determine response of collecting system.


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STRUVITE STONES

Important precautions while doing chemolysis :

Intrapelvic pressure must be below 30 cm water, monitoredthrough a manometer. Treatment should be discontinued ifpatient complaints flank pain.

Infusate must have adequate egress which may be a problemin infusion through a single ureteral catheter.

Chemolysis is contraindicated in presence of urinary tractinfection .

Hemocridin contains magnesium that can be absorbed to causehypermagnesemia.

Prevention : Prevention of struvite calculi depends anelimination of infection with urea splitting organisms. Ureaseinhibitor such as acetohydroxamic acid may be used todecrease urinary pH and ammonia levels.


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RENAL TUBULAR ACIDOSIS

Urolithiasis occurs only in type I, adisorder in which distal tubule isunable to maintain adequatehydrogen ion gradients. It accountsfor approximately 1% of calcium

stone forming patients.


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ENDOUROLOGIC TECHNIQUES

Percutaneous access to the upperurinary tract is the cornerstone ofendourologic technique.

The combination of rigid and flexibleendoscopes with ultrasound orelectrohydraulic lithotripsy allows

virtually all stones to be treated bypercutaneous means. It offers lowercost discomfort and reduced recoverytime in comparison with open surgery.


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Percutaneous puncture techniques

patient is placed on fluroscopy table inprone position and imaging of kidney is

carried out by fluoroscopy onultrasonography.

Puncture site is most commonly on posterioraxillary line midway between 12th rib and

iliac crest. Nephrostomy tube is placed through a renal

pyramid into a posterior calyx


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Ultrasound Lithotripsy :

High frequency sound waves causefragmentation after delivery through a

rigid probe passed through nephroscope. Small fragments are removed by

continuous suction.

Larger fragments are extracted withgrasping forceps or stone baskets underdirect vision.


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Electrohydraulic lithotripsy

Useful in stones resistant to US lithotripsy.

Hydraulic shock wave is produced near stoneproducing fragmentation.

Its probe is flexible and can be passed through bothrigid and fibreoptic endoscopes.

Fragments produced tend to scatter widely andretrieval is not as easy as with US lithotripsy.

Pneumatic Lithotripsy Delivery of jack hammer effectwith compressed in causing stone fragmentation.

Laser Lithotripsy Holmium laser in used which is aneffective incisor of tissue and additionally may be usedfor cutting scars and uretheral strictures.


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EXTRACORPOREAL SHOCKWAVE LITHOTRIPSY It was developed in Germany in the early 1980s.

Propogation of focussed shock wave through the body, whichfragment the stones.

Shock is produced by either discharging a high voltage ordeforming a piezocrystal or moving a membrane by

electromagnetic energy.

Average patient requires 1000 to 4000 shocks to fragmentstones completely.

In some cases fragments may cause obstruction of the ureter.

Combination of percutaneous techniques may be required to

reduce large staghorn calculi to smaller fragments before ESWLis performed.

Third generation machines are characterized by more compactdesigns, lower pressure and narrower focussing allowinganaesthesia free lithotripsy.


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CONTRAINDICATIONS OF ESWL

Infundibular obstruction.

Obstruction of ureter

Active urinary tract infection.


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Urinary Tract Calculi