2. INTRODUCTION
Renal calculus disease is uncommon in children, although it is being
detected more frequently.
An underlying metabolic cause can be identified in a significant
proportion of cases.
Vesical (bladder) calculi, endemic in some parts of India and other
developing countries, are chiefly related to dietary factors
Crystallization and calculus formation depends upon a number of
factors.
The point at which urine is saturated with a solute is called its
‘solubility product’
The point at which the solute can no longer remain in solution is
termed the ‘formation product.’
3. CONTD…
Between these two indices there is a metastable zone in which the
existing crystals grow but precipitation does not occur.
At the formation product, spontaneous nucleation takes place.
The role of inhibitors of calculus formation is poorly understood.
Substances such as magnesium, citrate, pyrophosphate, uropontin,
nephrocalcin, ribonucleic acid and zinc have been suggested to
inhibit formation of calcium crystals.
Citrate forms soluble complexes with calcium and reduces its free ion
concentration
Increased excretion of solutes, low urinary citrate and abnormal pH
are more important in calculus formation.
Urinary infection with urea-splitting organisms such as Proteus is
also an important cause of urolithiasis.
4. Metabolic calculi results commonly from primary metabolic disorders like
hypercalciuric states, distal RTA, hyperoxaluria, cystinuria and hyperuricosuria.
Stone promoting factors :-
Low intake of fluids causes increased supersaturation of stone forming salts.
Dairy products cause hypercalciuria and animal products increase the uric acid
production.
Increased oxalate content in vegetarian diet increases urinary excretion of
oxalate.
Immobilization leads to hypercalcemia and hypercalciuria.
Hypocitraturia resulting in reduced complexing of calcium with citrate causes
increased calcium oxalate super saturation.
Hypomagnesiuria results in reduced magnesium oxalate complexing,
producing increased calcium oxalate super saturation.
5. CLINICAL FEATURES
The usual symptoms are recurrent flank pain, renal colic, repeated
attacks of urinary tract infections and gross or microscopic hematuria.
The child may pass gravel or a small stone.
Occasionally the stone may be ‘silent’ and lead to obstructive
uropathy.
A stone in the urethra or in both ureters may rarely precipitate acute
renal failure
Noncalculi presentation as hematuria is seen in hypercalicuria and
even in hyperoxaluria and hyperuricosuria
Most of the times stones are identified during investigations for UTI,
hematuria, renal colic or renal failure
6. RADIOLOGICAL DIAGNOSIS
Radiological conformation is important
Plain X-ray of the abdomen shows radio-opaque stones like calcium oxalate
and calcium phosphate stones.
Radiolucent stones (uric acid, xanthine and cystine) are not seen in plain X-ray
abdomen.
But mixed uric acid and calcium oxalate stones as well as cystine stones with
more sulfur content can be radio-opaque. Infective stones exhibit varying
radio-opacity.
Ultrasonogram can identify the stones. They also detect hydronephrosis and
ureterohydronephrosis, which are the secondary effects. They also identify
associated anomalies of the tract.
Intravenous urography is useful in radiolucent stones by documenting the
filling defect. IVU is also useful to identify other anomalies of the tract.
7. Identification of etiology
Management of renal stone disease in children involves identification
of the etiology of urolithiasis as management depends on the
etiology.
Urine analysis is done for:
RBCs and pus cells in urine
Study of crystals in urine:
Calcium oxalate crystals Pyramid / Envelope shaped
Magnesium ammonium phosphate
crystals
Coffin lids (Triple phosphate)
Cystine crystals Flat hexagonal plates
Urate crystals Diamond /Trapezoid shaped
8. Urine culture is essential, as UTI may be secondary to a stone or
primary as in infective stones.
Renal function studies are mandatory for basal renal evaluation.
Acute renal failure may indicate bilateral ureteric obstruction or
obstruction to the single functioning kidney.
It signifies urgency in the management of obstruction
Serum electrolytes and arterial blood gas analysis are useful.
Normal anion gap hyperchloremic acidosis is the feature of Type I
RTA.
One has to look for hypercalcemia and hypercalciuria in every
stone disease.
Then look for hyperuricemia, hyperuricosuria, hyperoxaluria and
hypocitraturia
9. GENERAL STEPS OF MANAGEMENT
Increase the fluid intake to increase the urine volume.
Avoid unwanted intake of vitamin D, vitamin C and calcium
containing antacids.
Needed oral intake of milk should be advised in children.
Avoidance of oxalate rich substances is useful.
Colicky pain is usually treated with narcotic analgesics.
Surgical care for obstruction should be always considered.
Associated UTI, renal failure and obstruction modify the care to an
emergency one.
Liberal use of USG for monitoring is very much ideal.
10. SPECIFIC MANAGEMENT
HYPERCALCIURIA
Hypercalciuria is suspected when spot urine calcium/creatinine ratio in
the second morning urine sample is more than 0.21 and is confirmed by
24 hours urine calcium excretion of more than 4 mg/kg/day.
Hypercalciuria may be normocalcemic or hypercalcemic variety.
Conditions commonly seen with normocalcemic hypercalciuria are
idiopathic hypercalciuria and distal RTA.
Conditions usually seen with hypercalcemic hypercalciuria are
hyperparathyroidism, vitamin D intoxication and malignancy.
Idiopathic hypercalciuria is one of the common causes of renal calculi in
children.
11. In renal hypercalciuria, hydrochlorothiazide (2-3 mg/kg/day in 1-2 divided
doses) for increasing the tubular reabsorption of calcium is done.
Low sodium intake is mandatory for optimal effect.
In absorptive type of hypercalciuria decrease in calcium intake is needed but is
usually impossible in children.
Cellulose phosphate to bind calcium in the gut can be tried but there is
reduced calcium to complex with oxalate leading to increased oxalate
absorption and oxaluria.
Overall in hypercalicuria recommended dietary allowance of calcium and
protein should be allowed.
Gross reduction in calcium intake will lead to increased oxalate absorption due
to non-availability of adequate calcium to complex with oxalate leading to
hyperoxaluria.
Administration of potassium citrate (1.5-2 mEq/kg/day) results in reduction of
calcium excretion and an increase of urinary citrate and potassium
12. RENAL TUBULAR ACIDOSIS
About two thirds of children with distal RTA have nephrocalcinosis
and nephrolithiasis.
Calcium phosphate is the basic content of the stones with distal RTA.
High urine calcium, high urine pH and decreased citrate excretion are
the factors involved in stone formation in this condition.
Rickets can occur and growth may be poor.
Correction of acidosis with alkali therapy is done.
A child needs 3-5 mEq/kg/day of alkali.
Potassium citrate is better than sodium citrate.
Hydrochlorothiazide may also be needed to treat the associated
hypercalciuria
13. HYPEROXALURIA
Hyperoxaluria is defined as urine oxalate more than 0.7 mg/kg/day
or > 45 mg/1.73 m2 /day.
To cause a stone usually more than 1.4 mg/kg/day is needed.
This may be due to inherited or acquired disorder
Usual steps include reduction in intake of oxalate rich food,
administration of high dose pyridoxine, increasing the fluid intake,
normal dietary calcium intake to fascilitate calcium to bind to
oxalate in the gut and alkalinisation of urine with potassium citrate.
Citrate therapy reduces calcium oxalate supersaturation.
Reducing intake of spinach, cocoa, roasted coffee, peanuts etc
reduces dietary intake of oxalate.
14. In primary hyperoxaluria large doses of pyridoxine, maintaining
good hydration, hemodialysis to reduce oxalate burden are needed.
Combined liver and renal transplantations is the only real answer.
Acquired enteral variety is due to malabsorption of fat.
Normally good amount of oxalate is excreted as calcium oxalate, in
stool
For enteric hyperoxaluria, treatment of precipitating gastrointestinal
conditions and reducing the fat intake are needed
15. HYPERURICOSURIA
Low urine pH favours uric acid ionization resulting in crystalisation,
concretion formation, ending in stone formation.
Increased uric acid production (Gout due to enzyme defect, myelo-
lymphoproliferative diseases or excessive purine intake) and decreased
urinary volume as in chronic diarrhoea and ileostomy are the common
etiologies.
Uric acid further forms the nidus for calcium oxalate stone and it decreases
the concentration of inhibitors of calcium oxalate lithiasis in urine.
A value more than 750 mg/1.73 m2 or more than 11 mg/kg/ day is taken as
hyperuricosuria.
Reducing the dietary purine intake, urinary alkalinisation with potassium
citrate or with acetazolamide, increasing the fluid intake and allopurinol
administration if hyperuricemia is present are useful steps.
Diet rich in purine include majority of the animal protein, mushroom and
drybeans.
16. CYSTINURIA
Cystinuria is an autosomal recessive disorder with increased excretion
of cystine and dibasic amino acid ornithine, arginine and lysine.
There is a defective cystine transport across renal tubules and GI tract.
Cystine is usually insoluble in acid medium and hence crystal
precipitation occurs leading to urolithiasis.
Cystine is detected by the purple color reaction with cyanide
nitroprusside testing
Cystine stones are non radio-opaque unless the sulfur content and
calcium makes it radio-opaque
Beyond a urine pH above 7.5 the solubility is more and is difficult to
maintain this with alkali therapy.
Normal cystine values in urine is 30-50 mg/ 1.73 m2 or <
75 mg/gm of creatinine.
17. An increased fluid intake spread over 24 hours to reduce the
supersaturation along with adequate alkali therapy is the mainstay
of treatment.
D-Penicillamine therapy by forming cysteine-penicillamine
disulfide and excretion of it is useful but for its toxicity.
Surgical care may be needed for staghorn calculus or for removal
of bladder stones
18.
19. INFECTIVE STONES
Recurrent urinary infection with Proteus (rarely K. pneumoniae and
Serratia marcescens), such as in patients with obstructive uropathy
or urinary stasis, may cause stone formation.
Bacterial urease activity leads to formation of ammonium from urea,
which raises the urine pH causing precipitation of calcium
phosphate-carbonate (carbonate apatite) and magnesium
ammonium phosphate (struvite)
These amorphous stones mould easily into the renal calyces, grow
rapidly and fill the renal collecting system with staghorn calculi.
Surgical stone removal is difficult and recurrence of stone
formation is common
20. Acidification of urine and long-term chemoprophylaxis are the
usual post surgical care for infective stones
Conservative management is not advised, as infective calculi if left
untreated calculus pyonephrosis leading to destruction of kidney
can occur.
Percutaneous nephrolithotomy is employed to completely remove
struvite calculi, but some patients might require open surgery to
repair associated renal anomalies.
21. MEDICAL EXPULSIVE THERAPY
In a child with a renal or ureteral calculus, the decision whether to remove
the stone depends on its location, size, and composition (if known) and
whether obstruction and/or infection is present.
Pain is managed with nonsteroidal antiinflammatory drugs or, less often,
opiates.
Small ureteral calculi often pass spontaneously, although the child might
experience severe renal colic.
The narrowest segment of the ureter is the ureterovesical junction. Calculi
<5 mm will pass 80–90% of the time.
An α-adrenergic blocker, such as tamsulosin, 0.4 mg at bedtime, may
facilitate stone passage by decreasing ureteral pressure below the stone and
decreasing the frequency of the peristaltic contractions of the obstructed
ureter.
This intervention is termed medical expulsive therapy.
In many cases, passage of a ureteral stent past the stone endoscopically
relieves pain and dilates the ureter sufficiently to allow the calculus to pass.
22. SURGICAL MANAGEMENT
If the calculus does not pass or seems unlikely to pass or if there is
associated urinary tract infection, removal is necessary
Lithotripsy of bladder, ureteral, and small renal pelvic calculi using the
holmium laser through a flexible or rigid ureteroscope is quite effective.
Extracorporeal shock wave lithotripsy has been successfully applied to
children with renal and ureteral stones, with a success rate of > 75%
Another alternative is percutaneous nephrostolithotomy, in which access to
the renal collecting system is obtained percutaneously and the calculi are
broken down by ultrasonic lithotripsy.
In cases in which these modalities are unsuccessful, an alternative is
laparoscopic removal.
This procedure can be performed using the da Vinci robot.
23. Cystoscopic crushing or removal of the stones and basketing out
the VUJ junction stones are popular.
Lower ureteric stones are removed by ureteroscope.
Upper ureteric and pelvic stones are removed by percutaneous
nephrolithotomy.
ESWL alone or in combination with percutaneous nephrolithotomy
is useful in stones larger than 2.5 cms.
Open surgery is useful in difficult stones.
24.
25. REFERENCES
Nelson textbook of pediatrics
Principles and practice of pediatric nephrology by Nammalwar
Pediatric nephrology by Arvind bagga
