Urinary Lithiasis

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Information about Urinary Lithiasis

Published on March 16, 2014

Author: alanialiraqi



Urinary Lithiasis in children: Urinary Lithiasis in children Prof. Dr. Saad S Al Ani Senior Pediatric Consultant Head of Pediatric Department Khorfakkan Hospital Sharjah ,UAE Urinary Lithiasis : Urinary Lithiasis The wide geographic variation in the incidence of lithiasis in childhood is related to: Climatic Dietary Socioeconomic factors Approximately 7% of urinary calculi occur in children <16 yr of age. 2 Stone formation: Stone formation Approximately 75% of all stones contain calcium as a major constituent, and 60% are composed of calcium oxalate Most “ spontaneous ” stones are composed of c alcium, o xalate, or p hosphate crystals( COP ) Others are due to u ric acid, c ystine, a mmonium crystals, or p hosphate crystals, or a combination of these substances ( UCAP ) 3 Stone formation (Cont.): Stone formation (Cont.) The risk of stone formation increases in the presence of increasing concentrations of these crystals and is reduced with increasing concentrations of inhibitors. 4 Stone formation (Cont.): Stone formation (Cont.) Renal calculi develop from crystals that form on the calyx and aggregate to form a calculus Bladder calculi may be stones that formed in the kidney and traveled down the ureter, or they can form primarily in the bladder. 5 Stone formation (Cont.): Stone formation (Cont.) Stone formation depends on four factors : Matrix Precipitation - crystallization Epitaxy Absence of inhibitors of stone formation in the urine 6 Stone formation (Cont.): Stone formation (Cont.) 1. Matrix Is a mixture of protein , non-amino sugars, glucosamine, water, and organic ash Makes up 2-9% of the dry weight of urinary stones Is arranged within the stones in organized concentric laminations 7 Stone formation (Cont.): Stone formation (Cont.) 2. Precipitation-crystallization Refers to supersaturation of the urine with specific ions composing the crystal. Crystals aggregate by chemical and electrical forces. 8 Stone formation (Cont.): Stone formation (Cont.) Precipitation-crystallization ( Cont.) Saturation of urine with respect to the ions increases : Rate of nucleation, crystal growth, and aggregation likelihood of stone formation and growth 9 Stone formation (Cont.): Stone formation (Cont.) 3. Epitaxy Refers to the aggregation of crystals of different composition but similar lattice structure , thus forming stones of a heterogeneous nature. e.g. calcium oxalate and monosodium urate have similar structures and calcium oxalate crystals can aggregate on a nucleus of monosodium urate crystals . 10 Stone formation (Cont.): Stone formation (Cont.) 4. Inhibitors of stone formation Urine contains inhibitors of stone formation, including: i. Citrate ii. Diphosphonate iii. Magnesium ion 11 Clinical Manifestations: Clinical Manifestations Gross or microscopic hematuria Severe abdominal or flank pain (renal colic) ( If the calculus is in the renal pelvis, calyx , or ureter and causes obstruction ) Typically the pain radiates anteriorly to the scrotum or labia. Often the pain is intermittent 12 Clinical Manifestations (Cont.): Clinical Manifestations (Cont.) Irritative symptoms of dysuria , urgency , and frequency ( If the calculus is in the distal ureter) Asymptomatic . ( If the stone passes into the bladder) 13 Clinical Manifestations (Cont.): Clinical Manifestations (Cont.) Dysuria and difficulty voiding can result, particularly in boys. ( If the stone is in the urethra) Pass small amounts of gravel-like material . ( Some children ) 14 Diagnosis: Diagnosis Approximately 90% of urinary calculi are calcified to some degree and consequently are radiopaque on a plain abdominal film Struvite (magnesium ammonium phosphate) stones are radiopaque . Cystine , xanthine , and uric acid calculi may be radiolucent 15 Diagnosis (Cont.): Diagnosis (Cont.) Some children have nephrocalcinosis , ( which is calcification of the renal tissue itself ) Unenhanced spiral CT scan of the abdomen and pelvis is the most accurate study ( if a child with suspected renal colic) 96% sensitivity and specificity in: Delineating the number and location of calculi Demonstrates whether the involved kidney is hydronephrotic 16 Diagnosis (Cont.): Diagnosis (Cont.) An alternative is to obtain a plain radiograph of the abdomen and pelvis plus a renal ultrasonogram . Any material that resembles a calculus should be sent for analysis by a laboratory that specializes in identifying the components of urinary calculi 17 Metabolic Evaluation: Metabolic Evaluation A metabolic evaluation for the most common predisposing factors should be undertaken in all children with urolithiasis bearing in mind that structural, infectious, and metabolic factors often coexist. 18 Metabolic Evaluation (Cont.): Metabolic Evaluation (Cont.) Laboratory tests suggested for evaluation of urolithiasis 19 I. Serum Calcium Electrolytes and anion gap Phosphorus Creatinine Uric acid Alkaline phosphatase Metabolic Evaluation(Cont.): Metabolic Evaluation (Cont.) 20 II . Urine Urinalysis 24-hr collection for: - Creatinine clearance - Oxalate - Calcium - Uric acid - Phosphate - Dibasic amino acids Urine culture Calcium / creatinine ratio Spot test for cystinuria Metabolic Evaluation(Cont.): Metabolic Evaluation (Cont.) In children with hypercalciuria, further studies of : - Calcium excretion - Dietary calcium restriction - Calcium loading are necessary 21 Pathogenesis of specific Renal Calculi: Pathogenesis of specific Renal Calculi 1.Calcium Oxalate and Calcium Phosphate Calculi The most common metabolic abnormality in these patients is normocalcemic hypercalciuria Between 30% and 60% of children with calcium stones have hypercalciuria without hypercalcemia. 2 2 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi (Cont.) Hypercalciuria may be absorptive, renal, or resorptive 23 Type Serum Ca++ Restricted Ca++ (urine) Fasting Ca++ (urine) Ca++ load (urine) S.PTH Absorptive N N or ↑ N ↑ ↑ Renal N ↑ ↑ ↑ N Resorptive ↑ ↑ ↑ ↑ ↑ S.PTH :serum parathyroid hormone Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) Other metabolic aberrations that predispose to stone disease include : 24 1.Hyperoxaluria 2.Heterozygous cystinuria 3.Hyperuricosuria 4.Hypomagnesuria 5.Hypocitruria 6.Hyperparathyroidism 7.Renal tubular acidosis Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi (Cont.) 2.Cystine Calculi Cystinuria accounts for 1% of renal calculi in children Rare autosomal recessive disorder Disorder of the epithelial cells of the renal tubule that prevents absorption of the 4 dibasic amino acids ( C ystine, O rnithine , L ysine , A rginine,) ( COLA ) and results in excessive urinary excretion of these products. 25 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi (Cont.) 3.Struvite Calculi Magnesium ammonium phosphate In the kidney, the calculi often have a staghorn configuration , filling the calyces The calculi act as foreign bodies, causing: - Obstruction - Perpetuating infection - Causing gradual kidney damage 26 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi (Cont.) Struvite Calculi (cont.) Patients with struvite stones also can have metabolic abnormalities that predispose to stone formation. These stones often are seen in children with neuropathic bladder dysfunction , particularly those who have undergone an ileal conduit procedure 27 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) Urea-splitting organisms (most often Proteus spp, and occasionally Klebsiella spp , Escherichia coli , Pseudomonas spp, and others) 28 Urinary tract infections Urinary alkalinization and excessive production of ammonia Precipitation of magnesium ammonium phosphate (struvite) and calcium phosphate Struvite Calculi (cont.) Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) 4. Uric Acid Calculi Calculi containing uric acid are more common in less-developed areas of the world . Hyperuricosuria with or without hyperuricemia is the common underlying factor in most cases The stones are radiolucent 29 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) Uric Acid Calculi (cont.) Diagnosis should be suspected in a patient with persistently acid urine and urate crystalluria Hyperuricosuria can result from various inborn errors of purine metabolism 30 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) Uric Acid Calculi (cont.) Causes of urate calculi: Lesch-Nyhan syndrome Glucose- 6-phosphatase deficiency Short-bowel syndrome( e.g. ileostomies) Chronic dehydration and acidosis Some tumors and myeloproliferative diseases 31 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) 5.Indinavir Calculi Indinavir sulfate is a protease inhibitor approved for treating HIV infection . Up to 4% of patients acquire symptomatic nephrolithiasis. Most of the calculi are radiolucent and are composed of indinavir-based monohydrate, although calcium oxalate and/or phosphate have been present in some. 32 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) Indinavir Calculi (cont.) After each dose, 12% of the drug is excreted unchanged in the urine . The urine in these patients often contains crystals of characteristic rectangles and fan-shaped or starburst crystals. 33 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) Indinavir Calculi (cont.) Indinavir is soluble at a pH of <5.5 . Dissolution therapy by urinary acidification with : - Ammonium chloride or - Ascorbic acid 34 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) 6.Nephrocalcinosis Nephrocalcinosis refers to calcium deposition within the renal tissue. Often nephrocalcinosis is associated with urolithiasis. 35 Pathogenesis of specific Renal Calculi (Cont.): Pathogenesis of specific Renal Calculi ( Cont.) 6.Nephrocalcinosis (Cont.) The most common causes are: 36 Furosemide Cortical necrosis Distal RTA Hyperoxaluria Hyperparathyroidism Prolonged immobilization Medullary sponge kidney Cushing syndrome Hypophosphatemic rickets Hyperuricosuria Sarcoidosis Renal candidiasis Treatment: Treatment In a child with a renal or ureteral calculus, the decision whether to remove the stone depends on: - Location - Size - Composition (if known) - Obstruction and/or infection if is present . 37 Treatment (cont.) : Treatment (cont.) 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 38 Treatment (cont.) : Treatment (cont.) In children with hypercalciuria : - Some reduction in calcium and sodium intake is necessary - Thiazide diuretics also reduce renal calcium excretion. -Addition of potassium citrate , an inhibitor of calcium stones, with a dosage of 1-2 mEq/kg/24hr is beneficial. 39 Treatment (cont.) : Treatment (cont.) In patients with uric acid stones: - allopurinol is effective In patients with cystine stones : - Alkalinization of urine with sodium bicarbonate or sodium citrate is effective. D- penicillamine , which is a chelating agent that binds to cysteine or homocysteine, increasing the solubility of the product 40 Treatment (cont.) : Treatment (cont.) Treatment of type 1 RTA - Involves: * Correcting the metabolic acidosis * Replacing lost potassium and sodium Treatment of primary hyperoxaluria - Involves: * Liver transplantation * Kidney transplantation 41 References: References Lottmann H, Gagnadoux MF, Daudan M: Urolithiasis in children. In Gearhart JP, Rink RC, Mouriquand PDE, editors: Pediatric urology , ed 2, Philadelphia,2010, Saunders, pp 631–661 Nacaroglu HT, Demircin G, Bülbül M, Erdogan O, Akyüz SG, Caltik A. The association between urinary tract infection and idiopathic hypercalciuria in children. Ren Fail . 2013;35(3):327-32. 42 Thank you: Thank you Prof. Dr. Saad S Al Ani Khorfakkan Hospital ,Sharjah ,UAE

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