8: Management of pediatric kidney stone disease

Question 1

What is the current trend in the incidence of pediatric kidney stone disease?

Answer 1

The incidence of nephrolithiasis has increased over the past several decades at a rate of 5%–10% per year for children.

Question 2

Which age group has seen the greatest increase in pediatric kidney stone disease incidence?

Answer 2

Adolescents, particularly females, have seen the greatest increase in incidence.

Question 3

Do girls or boys have a higher frequency of kidney stones in the pediatric population?

Answer 3

Girls have a higher frequency of kidney stones compared to boys.

Question 4

What is the most common type of kidney stone in adults, and how does this compare to the distribution of stones in children?

Answer 4

In adults, approximately 75%–80% of stones are calcium oxalate, while children have a similar distribution of stones, with calcium phosphate stones being slightly more common and uric acid stones being less common.

Question 5

What is the notion about the causes of kidney stones in children, and is it true?

Answer 5

The notion that most kidney stones that form during childhood are caused by rare genetic causes, inborn errors of metabolism, or infection is not true.

Question 6

What comorbidities are pediatric patients with kidney stone disease at risk for?

Answer 6

Pediatric patients who develop kidney stone disease are at risk for development of comorbidities such as decreased bone mineral density, chronic kidney disease, and heart disease.

Question 7

What is the initial imaging study recommended for children with suspected nephrolithiasis?

Answer 7

Ultrasound is the initial imaging study recommended for children with suspected nephrolithiasis.

Question 8

When is a noncontrast computed tomography (CT) scan recommended for children with suspected nephrolithiasis?

Answer 8

A noncontrast computed tomography (CT) scan is recommended for children with suspected nephrolithiasis only if the clinical suspicion for stones remains high after a nondiagnostic ultrasound.

Question 9

What are the criteria for defining a stone on ultrasound?

Answer 9

The criteria for defining a stone on ultrasound are (1) hyperechoic focus in the renal papillae, calyces, or renal pelvis and (2) confirmatory twinkle artifact.

Question 10

What is the sensitivity and specificity of ultrasound for detecting urinary tract stones?

Answer 10

Ultrasound has >70% sensitivity and >95% specificity for detecting urinary tract stones, including stones located in the mid-ureter.

Question 11

What is the sensitivity and specificity of noncontrast CT for identifying kidney stones?

Answer 11

Noncontrast CT has nearly 100% sensitivity and specificity to identify kidney stones.

Question 12

What is the risk associated with ionizing radiation from CT scans?

Answer 12

Ionizing radiation from CT scans is associated with an increased risk for malignancy.

Question 13

What is the attributable risk for cancer from a single CT scan performed for kidney stones?

Answer 13

The attributable risk for cancer from a single CT scan performed for kidney stones is small (0.2%–0.3% above baseline).

Question 14

When should a low-dose noncontrast CT of the abdomen and pelvis be performed for children with suspected nephrolithiasis?

Answer 14

A low-dose noncontrast CT of the abdomen and pelvis should be performed for children with suspected nephrolithiasis when necessary (e.g., stone not visualized on ultrasound but with secondary signs of obstruction such as hydronephrosis).

Question 15

What is the first step in managing pediatric kidney stone disease?

Answer 15

Conducting an evaluation involves obtaining a medical history and conducting a focused dietary history. This helps to identify any risk factors that may contribute to the development of kidney stones.

Question 16

What information should be included in the dietary history for a patient with pediatric kidney stone disease?

Answer 16

The dietary history should include information on fluid and salt intake, vitamin and mineral supplementation, and any special diets the patient is following.
Explanation: The dietary history is an important aspect of the evaluation process, as it helps to identify dietary factors that may contribute to the development of kidney stones. For example, a diet high in sodium and low in fluids can increase the risk of stone formation.

Question 17

Why is a medication history important in the evaluation of pediatric kidney stone disease?

Answer 17

A medication history is important because certain medications can increase the risk of kidney stones.
Explanation: Medications such as corticosteroids, diuretics, protease inhibitors, antibiotics, and antiepileptics have been associated with an increased risk of kidney stone formation. Identifying any medication use is important in determining the cause of the kidney stones and developing an appropriate treatment plan.

Question 18

Which children are at increased risk for developing kidney stones?

Answer 18

Children with a history of prematurity, urinary tract abnormalities, urinary tract infections, intestinal malabsorption, and prolonged immobilization are at increased risk. Children with certain medical conditions or risk factors are more likely to develop kidney stones. These factors may affect urine composition, leading to the formation of stones.

Question 19

Why is the management of pediatric kidney stone disease important?

Answer 19

The management of pediatric kidney stone disease is important because untreated kidney stones can cause complications such as infection, obstruction, and damage to the kidneys.
Explanation: If left untreated, kidney stones can cause complications that can affect kidney function and overall health. Therefore, it is important to diagnose and manage kidney stones in children to prevent these complications.

Question 20

What is the purpose of a metabolic investigation in pediatric kidney stone disease?

Answer 20

The purpose of a metabolic investigation is to identify any metabolic abnormalities that could increase the risk of recurrence in children with kidney stones.

Question 21

How does the risk of recurrence differ between children with metabolic abnormalities and those without?

Answer 21

Children with a metabolic abnormality have a fivefold increased risk for recurrence compared with children with no metabolic disorder.

Question 22

Is a comprehensive metabolic evaluation necessary for all children with kidney stones?

Answer 22

The need for a comprehensive metabolic evaluation after a child’s first kidney stone has become somewhat controversial. However, some experts recommend that all children with kidney stones undergo a comprehensive metabolic evaluation to identify any underlying metabolic abnormalities.

Question 23

What type of analysis should be performed on a passed or retrieved stone?

Answer 23

An analysis should be performed on a passed or retrieved stone to determine its composition.

Question 24

What are some additional serum and urine studies that may be performed in pediatric kidney stone disease?

Answer 24

Additional serum and urine studies that may be performed include serum calcium, phosphorous, bicarbonate, magnesium, and uric acid levels, as well as a 24-hour urine collection to evaluate urinary levels of calcium, oxalate, uric acid, sodium, citrate, cystine, creatinine, as well as urinary volume and pH.

Question 25

What is the purpose of a serum creatinine test in pediatric kidney stone disease?

Answer 25

A serum creatinine test is used to evaluate for acute kidney injury or chronic kidney disease in children with kidney stones.

Question 26

What is hypercalciuria and how common is it in children with kidney stone disease?

Answer 26

Hypercalciuria is a condition where there is an excessive amount of calcium in the urine. It is found in 30% to 50% of children with kidney stone disease, making it one of the most common causes of pediatric stone formation.

Question 27

What is the most common cause of hypercalciuria in both children and adults?

Answer 27

The most common cause of hypercalciuria in both children and adults is idiopathic hypercalciuria, which means that there is no clear underlying medical condition that causes it.

Question 28

What can cause increased urinary oxalate excretion in children with kidney stone disease?

Answer 28

Increased urinary oxalate excretion may be caused by an inherited metabolic disorder called primary hyperoxaluria or as a secondary phenomenon caused by increased oxalate absorption or excessive intake of oxalate precursors.

Question 29

How can calcium-deficient diets increase the risk of hyperoxaluria in children?

Answer 29

Gastrointestinal absorption of oxalate varies inversely with dietary calcium intake, and, as a result, calcium-deficient diets may increase oxalate absorption and hyperoxaluria.

Question 30

What is cystinuria and how can it lead to pediatric stone formation?

Answer 30

Cystinuria is an autosomal recessive disorder that results in disordered amino acid transport in the proximal tubule. It can lead to the formation of kidney stones composed of cystine, an amino acid.

Question 31

Is uric acid nephrolithiasis common in children with kidney stone disease?

Answer 31

No, uric acid nephrolithiasis is rather rare in childhood, accounting for less than 5% of all renal calculi.

Question 32

What is the greatest risk factor for uric acid stone formation in children?

Answer 32

Hyperuricosuria in the setting of low urinary pH is the greatest risk factor for uric acid stone formation in children with kidney stone disease.

Question 33

Table 8.1

Inherited Conditions Leading to Nephrolithiasis

Answer 33

Question 34

What is medical expulsion therapy (MET)?

Answer 34

Answer: Medical expulsion therapy (MET) is the use of α-blockers or calcium-channel blockers to facilitate the passage of a ureteral stone.

Question 35

What is the mechanism for MET in increasing stone passage?

Answer 35

Answer: The mechanism for MET in increasing stone passage is that type 1a and 1d α-receptors are found in high concentrations in the smooth muscle of the distal third of the ureter and at the ureterovesical junction.

Question 36

Who is more likely to have spontaneous stone passage without MET?

Answer 36

Answer: Spontaneous stone passage without MET is higher among older patients and for smaller (<5 mm) and more distal ureteral stones.

Question 37

What is the recommendation for pediatric patients with uncomplicated ureteral stones ≤10 mm according to the American Urological Association (AUA) and Endourological Society Guideline?

Answer 37

Answer: The recommendation for pediatric patients with uncomplicated ureteral stones ≤10 mm according to the American Urological Association (AUA) and Endourological Society Guideline is that they should be offered “observation with or without MET using α-blockers” (Grade B Level of Evidence).

Question 38

What are the surgical management options for pediatric kidney stone disease?

Answer 38

Answer: The surgical management options for pediatric kidney stone disease include ureteroscopy (URS), shock wave lithotripsy (SWL), and percutaneous nephrolithotomy (PCNL).

Question 39

Why do up to 60% of children with kidney or ureteral stones require surgery?

Answer 39

Answer: Up to 60% of children with kidney or ureteral stones require surgery due to the size and location of the stone, patient anatomy, and patient (and provider) preference.

Question 40

What are the stone clearance rates for PCNL, URS, and SWL in pediatric patients?

Answer 40

Answer: The stone clearance rates for PCNL range from 70%–97%, for URS it is 85%–88%, and for SWL it is 80%–83%.

Question 41

What factors determine the choice of intervention for pediatric kidney stone disease?

Answer 41

Answer: The choice of intervention for pediatric kidney stone disease is determined primarily by the size and location of the stone, patient anatomy, and patient (and provider) preference.

Question 42

Why is a urine culture obtained before upper tract procedures?

Answer 42

A urine culture is obtained before upper tract procedures to determine if the urine is sterile. This information is used to guide preoperative antibiotic therapy to prevent infection.

Question 43

What is the recommended first-line treatment for children with ureteral stones who have failed observation/MET or have a renal stone burden of ≤20 mm?

Answer 43

Answer: The recommended first-line treatment for children with ureteral stones who have failed observation/MET or have a renal stone burden of ≤20 mm is either SWL or URS. SWL (shock wave lithotripsy) or URS (ureteroscopic management of upper urinary tract calculi) should be the first-line treatment for children with ureteral stones who have failed observation/MET or have a renal stone burden of ≤20 mm.

Question 44

What is the success rate of URS in children, and how does it compare to the adult population?

Answer 44

Answer: Stone clearance with URS in children exceeds 85%, and the success rate is similar to that in the adult population. Explanation: Despite the miniaturization and availability of endourologic instrumentation, URS has a success rate of over 85% in children, which is similar to that in the adult population.

Question 45

Is routine “prestenting” before URS recommended for children?

Answer 45

No, routine “prestenting” before URS is not recommended for children.
Explanation: Although 25% of children undergoing URS may require a staged procedure, routine “prestenting” before URS is not recommended.

Question 46

What are the complications of URS in children, and how common are serious complications?

Answer 46

The complications of URS in children include ureteral injury, urinary tract infection, and bleeding. Serious complications (> Clavien 3) are uncommon.
Explanation: The complications of URS in children include ureteral injury, urinary tract infection, and bleeding. Serious complications (> Clavien 3) are uncommon, and these include unrecognized ureteral injury, including mucosal flaps and tears, perforation, false passage, and partial to complete ureteral avulsion.

Question 47

What should be done if a ureteral injury occurs during URS in a child?

Answer 47

If a ureteral injury occurs during URS in a child, the procedure should be aborted, and a ureteral stent should be placed to mitigate shear force injury on the ureter, ischemic damage, and extravasation of irrigant or urine.
Explanation: If a ureteral injury occurs during URS in a child, the procedure should be aborted, and a ureteral stent should be placed to mitigate shear force injury on the ureter, ischemic damage, and extravasation of irrigant or urine.

Question 48

What is SWL and how is it used in the management of kidney and ureteral stones in children?

Answer 48

SWL stands for shock wave lithotripsy, which is a non-invasive procedure that uses shock waves to break up kidney and ureteral stones into smaller fragments that can be passed out of the body through the urine. It is one of the treatment options for upper tract calculi 15 mm or smaller in children, along with URS.

Question 49

How effective is SWL in treating upper tract calculi in children?

Answer 49

When used as a primary treatment option for upper tract calculi, SWL efficacy ranges from 68% to 84%, which is comparable to adult cohorts. However, stone clearance in children with a history of a urologic anomaly or urinary tract reconstruction is low. Depending on body habitus, stone size, and stone location, URS or PCNL may be better treatment options for these children.

Question 50

What factors influence the success of SWL in treating kidney and ureteral stones in children?

Answer 50

Stone size is an important determinant of stone clearance after SWL. Studies report a 91% clearance for mean stone diameter less than 10 mm versus 75% clearance for stone size greater than 10 mm. Stone location is also an important determinant of SWL outcomes, and the most effective management of lower pole calculi has yet to be determined in children. Stone composition is another important effect modifier of SWL efficacy, with cystine stones being uniquely challenging due to their hardness and high recurrence rates.

Question 51

When is SWL not recommended as a treatment option for kidney and ureteral stones in children?
What are the short-term side effects of SWL in children?

Answer 51

The short-term side effects of SWL include hematuria (up to 44%) and subcapsular or perirenal hematoma. Children treated with SWL need to pass stone fragments and are at risk for intermittent renal colic, emergency department visits for pain control, and steinstrasse. There is also concern for an increased risk of developing hypertension following SWL in children, although studies to date are not conclusive.

Question 52

When is SWL not recommended as a treatment option for kidney and ureteral stones in children?

Answer 52

SWL is not recommended as a primary treatment option for upper tract calculi in children with a history of a urologic anomaly or urinary tract reconstruction. Depending on body habitus, stone size, and stone location, URS or PCNL may be better treatment options for these children. Additionally, SWL may not be effective for stones larger than 20 mm, as the probability of clearance is lower than PCNL and may require multiple treatments.

Question 53

What is considered first-line therapy for renal stones greater than 20 mm in children?

Answer 53

PCNL (percutaneous nephrolithotomy) is considered first-line therapy for renal stones greater than 20 mm in children.

Question 54

What is the stone clearance rate for PCNL in children with renal stones greater than 20 mm?

Answer 54

The stone clearance rate for PCNL in children with renal stones greater than 20 mm is approximately 90%.

Question 55

Why might PCNL be a better option than SWL for children with renal stones greater than 20 mm?

Answer 55

PCNL may be a better option for children with renal stones greater than 20 mm because SWL is less effective than PCNL for large renal stones.

Question 56

What should be considered before performing PCNL on a child with kidney or ureteral stones?

Answer 56

Before performing PCNL on a child with kidney or ureteral stones, stone size, stone location, adjacent organs, and any alteration in renal anatomy caused by scoliosis, lordosis, or kyphosis should be considered.

Question 57

What are the risks associated with PCNL?

Answer 57

The risks associated with PCNL include bleeding requiring transfusion, delayed renal hemorrhage requiring angioembolization, sepsis, pneumothorax, hemothorax, urothorax, incomplete stone clearance, and injuries to adjacent organs.

Question 58

What should be done before PCNL if a child has a urinary tract infection?

Answer 58

If a child has a urinary tract infection, it should be treated before PCNL. A urine culture and antibiotic sensitivities should be checked 2 to 3 weeks before the procedure.

Question 59

What is sandwich therapy?

Answer 59

Historically, primary PCNL with adjunctive SWL to clear residual fragments was often performed for children, and this is called sandwich therapy.

Question 60

What are the most significant determinants affecting complication rates in PCNL for children?

Answer 60

The most significant determinants affecting complication rates in PCNL for children are operative time, sheath size, midcalyceal puncture, and partial staghorn formation.

Question 61

Can PCNL cause loss of kidney function or scarring in children?

Answer 61

PCNL has not been shown to cause loss of kidney function or scarring in children.

Question 62

How should complications of PCNL in children be treated?

Answer 62

Complications of PCNL in children, including hydrothorax, colonic injury, and postoperative bleeding, should be treated similarly to adults. If significant bleeding occurs, the operation should be aborted and the collecting system should be treated as clinically indicated. If a renal pelvis injury occurs, an antegrade ureteral stent should be placed, if feasible.

Question 63

In what patients are laparoscopic and robotic-assisted pyelolithotomy indicated?

Answer 63

Laparoscopic and robotic-assisted pyelolithotomy is indicated in children or adolescents with renal or ureteral stones and a coexisting anatomic anomaly, such as ureteropelvic junction (UPJ) obstruction. In these patients, robotic (or laparoscopic) pyeloplasty with concomitant stone removal is indicated.

Question 64

Table 8.2

2016 American Urological Association and Endourological Society Recommendations for the Surgical Management of Urinary Stones for Pediatric Patients

Answer 64

Question 65

Table 8.3

Historic and Contemporary Outcomes of Percutaneous Nephrolithotomy for Pediatric Patients

Answer 65

Question 66

Why is fluid intake important in the management of kidney and ureteral stones in children and adolescents?

Answer 66

Fluid intake is critical in reducing the concentration of lithogenic factors, such as calcium, oxalate, uric acid, and cystine, which are responsible for stone formation. By increasing fluid intake, the urine is diluted, making it less likely for these lithogenic factors to form crystals and cause stones.

Question 67

How much fluid intake is recommended for children and adolescents to prevent kidney stones?

Answer 67

Most clinicians recommend fluid intake at least equal to calculated maintenance rates in children and greater than 2-2.5 L in adolescents and adults. For children with cystinuria or primary hyperoxaluria, even higher fluid intake levels (1.5-2 L/m2) may be recommended.

Question 68

Are there any specific fluids that can help prevent calcium stone formation in children and adolescents?

Answer 68

Reports suggest that fluids that increase urinary pH and citrate excretion, such as orange juice, lemonade, and black currant juice, can reduce the risk of calcium stone formation. However, grapefruit juice appears to increase the risk for calcium-based stones.

Question 69

Is it controversial whether or not soft drinks increase lithogenic potential?

Answer 69

Yes, it remains controversial whether or not soft drinks increase lithogenic potential. Some studies have suggested that consumption of sugary drinks like soft drinks is associated with an increased risk of kidney stone formation, while others have not found a significant association. However, it is generally recommended to limit or avoid the intake of sugary drinks for overall health benefits.

Question 70

How does increased sodium intake affect the formation of kidney stones?

Answer 70

Increased sodium intake is associated with an increase in urinary calcium excretion and calcium stone formation. Sodium competes for reabsorption at the level of the renal tubules, leading to increased calcium excretion and stone formation.

Question 71

What is the recommended daily intake of sodium for children and adolescents with hypercalciuria or calcium-containing stones?

Answer 71

A low-salt diet corresponding to less than 2–3 mEq/kg/day in children or less than 2.4 g/day in adolescents or adults is generally recommended for patients with hypercalciuria or calcium-containing stones. This can help reduce urinary calcium excretion and prevent the formation of new stones.

Question 72

Can a low-salt diet also benefit patients with cystinuria?

Answer 72

Yes, a low-salt diet may also reduce urinary cystine excretion in patients with cystinuria. This can help prevent the formation of new stones in these patients.

Question 73

What is the recommended dietary measure for the medical management of pediatric kidney stones?

Answer 73

The recommended dietary measure for the medical management of pediatric kidney stones is to increase calcium intake.

Question 74

How does a higher calcium diet reduce the risk of stone formation in children and adolescents?

Answer 74

A higher calcium diet effectively binds dietary oxalate in the gut, which reduces intestinal oxalate absorption and eventual urinary oxalate excretion. This mechanism explains the seeming paradox that a higher calcium diet is associated with a reduced risk for stone formation.

Question 75

Should dietary calcium intake be restricted in children and adolescents with kidney and ureteral stones?

Answer 75

No, the current recommendation for stone formers is not to restrict dietary calcium intake. In fact, a higher calcium diet is recommended to reduce the risk of stone formation.

Question 76

What are some examples of dietary measures recommended for secondary prevention of pediatric kidney stones?

Answer 76

In addition to increasing calcium intake, other dietary measures recommended for secondary prevention of pediatric kidney stones include limiting sodium and animal protein intake, increasing fluid intake, and consuming a diet rich in fruits and vegetables.

Question 77

What is the role of dietary animal proteins in calcium oxalate stone formation?

Answer 77

There is evidence that dietary animal proteins (meat, fish, and poultry) contribute to the formation of calcium oxalate stones.
Explanation: A diet high in animal protein can increase the production of urinary oxalate, which can bind with calcium to form stones.

Question 78

What is the role of dietary oxalate in stone formation?

Answer 78

The role of dietary oxalate in stone formation is controversial because only approximately 10%–20% of urinary oxalate excretion is derived from the diet.

Question 79

When should dietary oxalate ingestion be limited?

Answer 79

Dietary oxalate ingestion should be limited in calcium oxalate stone formers who demonstrate evidence of hyperoxaluria.

Question 80

What are some high oxalate-containing foods?

Answer 80

Some high oxalate-containing foods include certain nuts (almonds, peanuts, cashews, walnuts, and pecans), spinach, soybeans, tofu, rhubarb, beets, sweet potatoes, wheat bran, okra, parsley, chives, black raspberries, star fruit, green tea, and chocolate.

Question 81

Why should Vitamin C supplements be discontinued in calcium oxalate stone formers with hyperoxaluria?

Answer 81

Vitamin C supplements have been associated with increased risk for calcium oxalate stone formation. Therefore, these supplements should be discontinued in calcium oxalate stone formers with hyperoxaluria.

Question 82

How does citrate help prevent calcium oxalate stone formation?

Answer 82

Citrate helps prevent calcium oxalate stone formation by binding with calcium in the urine, which makes it less likely to form crystals that can lead to stone formation. Citrate also inhibits crystal formation by preventing calcium oxalate particles from clumping together.

Question 83

How does a diet high in potassium help prevent urolithiasis?

Answer 83

A diet high in potassium can help prevent urolithiasis by increasing urinary citrate excretion. Potassium-rich fruits and vegetables contain large amounts of citrate, which is protective against calcium oxalate stone formation. In addition, a potassium-deficient diet can cause increased urinary calcium excretion, which can lead to stone formation.

Question 84

What are some dietary measures that can help prevent kidney stones in children and adolescents?

Answer 84

Dietary measures that can help prevent kidney stones in children and adolescents include increasing magnesium intake, avoiding high sucrose intake, and increasing phytate intake through high-fiber foods such as cereals, legumes, vegetables, and nuts.

Question 85

How does magnesium intake help prevent kidney stones in men and children with secondary hyperoxaluria?

Answer 85

Magnesium complexes with oxalate and may prevent enteric oxalate absorption, which in turn can decrease calcium oxalate supersaturation in the urine. Higher dietary magnesium has been associated with a lower risk for stone formation in men, and supplementation may be helpful in the treatment of children with secondary hyperoxaluria.

Question 86

What is the role of diuretics in the management of kidney and ureteral stones in children and adolescents?

Answer 86

A: Diuretics are often used in children with hypercalciuria that does not respond to a restricted sodium diet. A thiazide diuretic, such as hydrochlorothiazide, is usually recommended.

Question 87

What is the recommended dosage of hydrochlorothiazide for children with hypercalciuria?

Answer 87

A: The usual recommendation is 1-2 mg/kg per day, with a maximum adult dose of 25-100 mg per day.

Question 88

Why might potassium citrate be added to the treatment regimen of a child taking hydrochlorothiazide?

Answer 88

A: Hydrochlorothiazide can cause potassium depletion, so potassium citrate may be added to mitigate this effect.

Question 89

Are there any potential side effects or risks associated with using diuretics in children with kidney and ureteral stones?

Answer 89

A: As with any medication, there is always a risk of side effects. Common side effects of diuretics include low potassium levels, dehydration, and electrolyte imbalances. It is important to monitor children closely while they are taking these medications.

Question 90

What are alkali agents in the pharmacotherapy for kidney and ureteral stones?

Answer 90

Alkali agents are medications that increase the pH of urine by neutralizing acid, which helps to prevent the formation of kidney stones.

Question 91

What is the recommended dosage for potassium citrate in the treatment of calcium oxalate stone formation?

Answer 91

The recommended dosage of potassium citrate for patients with calcium oxalate stone formation is 2-4 mEq/kg/day for children and 30-90 mEq/day for adults.

Question 92

What is the effect of potassium citrate on calcium phosphate stone formation?

Answer 92

Potassium citrate may increase the risk for calcium phosphate stone formation by increasing the urinary pH above 6.5, which can decrease the calcium phosphate supersaturation product.

Question 93

What are the potential side effects of alkali agents?

Answer 93

The side effects of alkali agents are usually minor and gastrointestinal in nature, such as diarrhea, nausea, and abdominal discomfort.

Question 94

In what conditions is potassium citrate used to alkalinize the urine?

Answer 94

Potassium citrate is used to alkalinize the urine in patients with uric acid lithiasis (goal of urine pH >6.5), cystinuria (goal of urine pH >7), and hyperoxaluria.

Question 95

What are thiol-containing agents used for in the management of kidney and ureteral stones in children and adolescents?

Answer 95

Thiol-containing agents are used for patients with cystinuria in whom fluid/dietary modifications and urinary alkalinization are ineffective in preventing stone recurrences.

Question 96

What are the two most common thiol-containing agents used for cystinuria?

Answer 96

The two most common agents are D-penicillamine and α-mercaptopropionylglycine (tiopronin).

Question 97

How do thiol-containing agents work to prevent stone recurrences in patients with cystinuria?

Answer 97

These agents work by reducing the disulfide bond that bridges two molecules of cysteine.

Question 98

What are the adverse side effects of D-penicillamine?

Answer 98

D-penicillamine has a large number of adverse side effects including febrile reactions, gastrointestinal discomfort, liver dysfunction, impaired taste, bone marrow suppression, trace metal deficiencies, membranous glomerulopathy, myasthenia gravis, and skin eruptions (elastosis perforans serpiginosa).

Question 99

Are the adverse effects of α-mercaptopropionylglycine similar to those of D-penicillamine?

Answer 99

Yes, the incidence of adverse effects for α-mercaptopropionylglycine is similar but may be slightly less.

Question 100

What should be monitored regularly in patients taking thiol-containing agents?

Answer 100

Liver enzymes, complete blood count, urinalysis, and copper and zinc levels should be performed regularly in patients taking these medications.

Question 101

What is the mainstay of therapy for most children with uric acid calculi?

Answer 101

The mainstay of therapy for most children with uric acid calculi is a combination of high urine output and urinary alkalinization.

Question 102

What is the role of Allopurinol in the management of kidney and ureteral stones in children and adolescents?

Answer 102

Allopurinol is indicated in patients with both hyperuricemia and hyperuricosuria.

Question 103

What is the recommended dose of Allopurinol for children and adolescents with kidney and ureteral stones?

Answer 103

The recommended dose of Allopurinol is 4–10 mg/kg/day, with an adult maximum of 300 mg/day.

Question 104

What is the mechanism of action of Allopurinol?

Answer 104

Allopurinol inhibits xanthine dehydrogenase, leading to the accumulation and urinary excretion of xanthine.

Question 105

What is a potential side effect of chronic therapy with Allopurinol in children with kidney and ureteral stones?

Answer 105

Rarely, a secondary xanthinuria with xanthine calculi is observed in children on chronic therapy.

Question 106

When should Allopurinol be considered as the agent of choice for treating hyperuricosuric calcium oxalate urolithiasis?

Answer 106

Allopurinol may be the agent of choice for treating hyperuricosuric calcium oxalate urolithiasis if there is no concomitant evidence of hypercalciuria, hyperoxaluria, or hypocitraturia.

Question 107

What is pyridoxine and why is it important in the management of children and adolescents with kidney and ureteral stones?

Answer 107

Pyridoxine is an important cofactor of the alanine-glyoxylate transaminase (AGT) enzyme, which plays a crucial role in the metabolism of oxalate in the body. In approximately 10%–30% of children with PH1, pyridoxine can reduce urinary oxalate excretion by more than 30%, making it an important treatment option for these patients.

Question 108

What is PH1 and how is it related to pyridoxine sensitivity?

Answer 108

PH1 is a type of primary hyperoxaluria, which is a rare genetic disorder that causes an overproduction of oxalate in the body. In some cases of PH1, pyridoxine can help to reduce urinary oxalate excretion, making it a useful treatment option for these patients.

Question 109

How should pyridoxine be dosed in patients with suspected PH1?

Answer 109

In patients with suspected PH1, pyridoxine should be initiated at a dose of 2–5 mg/kg/day and titrated upward to a maximum dose of 8–10 mg/kg/day until a diagnosis can be made and response assessed.

Question 110

What are the potential side effects of large doses of pyridoxine?

Answer 110

Large doses of pyridoxine have been known to induce sensory neuropathies, which can cause numbness, tingling, and other nerve-related symptoms. It is important to monitor patients closely for signs of these side effects when using high doses of pyridoxine.