8: Management of pediatric kidney stone disease Flashcards
1
Q
What is the current trend in the incidence of pediatric kidney stone disease?
A
The incidence of nephrolithiasis has increased over the past several decades at a rate of 5%–10% per year for children.
2
Q
Which age group has seen the greatest increase in pediatric kidney stone disease incidence?
A
Adolescents, particularly females, have seen the greatest increase in incidence.
3
Q
Do girls or boys have a higher frequency of kidney stones in the pediatric population?
A
Girls have a higher frequency of kidney stones compared to boys.
4
Q
What is the most common type of kidney stone in adults, and how does this compare to the distribution of stones in children?
A
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.
5
Q
What is the notion about the causes of kidney stones in children, and is it true?
A
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.
6
Q
What comorbidities are pediatric patients with kidney stone disease at risk for?
A
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.
7
Q
What is the initial imaging study recommended for children with suspected nephrolithiasis?
A
Ultrasound is the initial imaging study recommended for children with suspected nephrolithiasis.
8
Q
When is a noncontrast computed tomography (CT) scan recommended for children with suspected nephrolithiasis?
A
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.
9
Q
What are the criteria for defining a stone on ultrasound?
A
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.
10
Q
What is the sensitivity and specificity of ultrasound for detecting urinary tract stones?
A
Ultrasound has >70% sensitivity and >95% specificity for detecting urinary tract stones, including stones located in the mid-ureter.
11
Q
What is the sensitivity and specificity of noncontrast CT for identifying kidney stones?
A
Noncontrast CT has nearly 100% sensitivity and specificity to identify kidney stones.
12
Q
What is the risk associated with ionizing radiation from CT scans?
A
Ionizing radiation from CT scans is associated with an increased risk for malignancy.
13
Q
What is the attributable risk for cancer from a single CT scan performed for kidney stones?
A
The attributable risk for cancer from a single CT scan performed for kidney stones is small (0.2%–0.3% above baseline).
14
Q
When should a low-dose noncontrast CT of the abdomen and pelvis be performed for children with suspected nephrolithiasis?
A
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).
15
Q
What is the first step in managing pediatric kidney stone disease?
A
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.
16
Q
What information should be included in the dietary history for a patient with pediatric kidney stone disease?
A
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.
17
Q
Why is a medication history important in the evaluation of pediatric kidney stone disease?
A
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.
18
Q
Which children are at increased risk for developing kidney stones?
A
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.
19
Q
Why is the management of pediatric kidney stone disease important?
A
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.
20
Q
What is the purpose of a metabolic investigation in pediatric kidney stone disease?
A
The purpose of a metabolic investigation is to identify any metabolic abnormalities that could increase the risk of recurrence in children with kidney stones.
21
Q
How does the risk of recurrence differ between children with metabolic abnormalities and those without?
A
Children with a metabolic abnormality have a fivefold increased risk for recurrence compared with children with no metabolic disorder.
22
Q
Is a comprehensive metabolic evaluation necessary for all children with kidney stones?
A
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.
23
Q
What type of analysis should be performed on a passed or retrieved stone?
A
An analysis should be performed on a passed or retrieved stone to determine its composition.
24
Q
What are some additional serum and urine studies that may be performed in pediatric kidney stone disease?
A
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.
25
What is the purpose of a serum creatinine test in pediatric kidney stone disease?
A serum creatinine test is used to evaluate for acute kidney injury or chronic kidney disease in children with kidney stones.
26
What is hypercalciuria and how common is it in children with kidney stone disease?
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.
27
What is the most common cause of hypercalciuria in both children and adults?
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.
28
What can cause increased urinary oxalate excretion in children with kidney stone disease?
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.
29
How can calcium-deficient diets increase the risk of hyperoxaluria in children?
Gastrointestinal absorption of oxalate varies inversely with dietary calcium intake, and, as a result, calcium-deficient diets may increase oxalate absorption and hyperoxaluria.
30
What is cystinuria and how can it lead to pediatric stone formation?
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.
31
Is uric acid nephrolithiasis common in children with kidney stone disease?
No, uric acid nephrolithiasis is rather rare in childhood, accounting for less than 5% of all renal calculi.
32
What is the greatest risk factor for uric acid stone formation in children?
Hyperuricosuria in the setting of low urinary pH is the greatest risk factor for uric acid stone formation in children with kidney stone disease.
33
Table 8.1
Inherited Conditions Leading to Nephrolithiasis
34
What is medical expulsion therapy (MET)?
Answer: Medical expulsion therapy (MET) is the use of α-blockers or calcium-channel blockers to facilitate the passage of a ureteral stone.
35
What is the mechanism for MET in increasing stone passage?
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.
36
Who is more likely to have spontaneous stone passage without MET?
Answer: Spontaneous stone passage without MET is higher among older patients and for smaller (<5 mm) and more distal ureteral stones.
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: 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).
38
What are the surgical management options for pediatric kidney stone disease?
Answer: The surgical management options for pediatric kidney stone disease include ureteroscopy (URS), shock wave lithotripsy (SWL), and percutaneous nephrolithotomy (PCNL).
39
Why do up to 60% of children with kidney or ureteral stones require surgery?
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.
40
What are the stone clearance rates for PCNL, URS, and SWL in pediatric patients?
Answer: The stone clearance rates for PCNL range from 70%–97%, for URS it is 85%–88%, and for SWL it is 80%–83%.
41
What factors determine the choice of intervention for pediatric kidney stone disease?
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.
42
Why is a urine culture obtained before upper tract procedures?
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.
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: 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.
44
What is the success rate of URS in children, and how does it compare to the adult population?
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.
45
Is routine "prestenting" before URS recommended for children?
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.
46
What are the complications of URS in children, and how common are serious complications?
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.
47
What should be done if a ureteral injury occurs during URS in a child?
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.
48
What is SWL and how is it used in the management of kidney and ureteral stones in children?
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.
49
How effective is SWL in treating upper tract calculi in children?
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.
50
What factors influence the success of SWL in treating kidney and ureteral stones in children?
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.
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?
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.
52
When is SWL not recommended as a treatment option for kidney and ureteral stones in children?
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.
53
What is considered first-line therapy for renal stones greater than 20 mm in children?
PCNL (percutaneous nephrolithotomy) is considered first-line therapy for renal stones greater than 20 mm in children.
54
What is the stone clearance rate for PCNL in children with renal stones greater than 20 mm?
The stone clearance rate for PCNL in children with renal stones greater than 20 mm is approximately 90%.
55
Why might PCNL be a better option than SWL for children with renal stones greater than 20 mm?
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.
56
What should be considered before performing PCNL on a child with kidney or ureteral stones?
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.
57
What are the risks associated with PCNL?
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.
58
What should be done before PCNL if a child has a urinary tract infection?
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.
59
What is sandwich therapy?
Historically, primary PCNL with adjunctive SWL to clear residual fragments was often performed for children, and this is called sandwich therapy.
60
What are the most significant determinants affecting complication rates in PCNL for children?
The most significant determinants affecting complication rates in PCNL for children are operative time, sheath size, midcalyceal puncture, and partial staghorn formation.
61
Can PCNL cause loss of kidney function or scarring in children?
PCNL has not been shown to cause loss of kidney function or scarring in children.
62
How should complications of PCNL in children be treated?
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.
63
In what patients are laparoscopic and robotic-assisted pyelolithotomy indicated?
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.
64
Table 8.2
2016 American Urological Association and Endourological Society Recommendations for the Surgical Management of Urinary Stones for Pediatric Patients
65
Table 8.3
Historic and Contemporary Outcomes of Percutaneous Nephrolithotomy for Pediatric Patients
66
Why is fluid intake important in the management of kidney and ureteral stones in children and adolescents?
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.
67
How much fluid intake is recommended for children and adolescents to prevent kidney stones?
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.
68
Are there any specific fluids that can help prevent calcium stone formation in children and adolescents?
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.
69
Is it controversial whether or not soft drinks increase lithogenic potential?
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.
70
How does increased sodium intake affect the formation of kidney stones?
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.
71
What is the recommended daily intake of sodium for children and adolescents with hypercalciuria or calcium-containing stones?
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.
72
Can a low-salt diet also benefit patients with cystinuria?
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.
73
What is the recommended dietary measure for the medical management of pediatric kidney stones?
The recommended dietary measure for the medical management of pediatric kidney stones is to increase calcium intake.
74
How does a higher calcium diet reduce the risk of stone formation in children and adolescents?
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.
75
Should dietary calcium intake be restricted in children and adolescents with kidney and ureteral stones?
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.
76
What are some examples of dietary measures recommended for secondary prevention of pediatric kidney stones?
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.
77
What is the role of dietary animal proteins in calcium oxalate stone formation?
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.
78
What is the role of dietary oxalate in stone formation?
The role of dietary oxalate in stone formation is controversial because only approximately 10%–20% of urinary oxalate excretion is derived from the diet.
79
When should dietary oxalate ingestion be limited?
Dietary oxalate ingestion should be limited in calcium oxalate stone formers who demonstrate evidence of hyperoxaluria.
80
What are some high oxalate-containing foods?
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.
81
Why should Vitamin C supplements be discontinued in calcium oxalate stone formers with hyperoxaluria?
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.
82
How does citrate help prevent calcium oxalate stone formation?
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.
83
How does a diet high in potassium help prevent urolithiasis?
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.
84
What are some dietary measures that can help prevent kidney stones in children and adolescents?
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.
85
How does magnesium intake help prevent kidney stones in men and children with secondary hyperoxaluria?
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.
86
What is the role of diuretics in the management of kidney and ureteral stones in children and adolescents?
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.
87
What is the recommended dosage of hydrochlorothiazide for children with hypercalciuria?
A: The usual recommendation is 1-2 mg/kg per day, with a maximum adult dose of 25-100 mg per day.
88
Why might potassium citrate be added to the treatment regimen of a child taking hydrochlorothiazide?
A: Hydrochlorothiazide can cause potassium depletion, so potassium citrate may be added to mitigate this effect.
89
Are there any potential side effects or risks associated with using diuretics in children with kidney and ureteral stones?
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.
90
What are alkali agents in the pharmacotherapy for kidney and ureteral stones?
Alkali agents are medications that increase the pH of urine by neutralizing acid, which helps to prevent the formation of kidney stones.
91
What is the recommended dosage for potassium citrate in the treatment of calcium oxalate stone formation?
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.
92
What is the effect of potassium citrate on calcium phosphate stone formation?
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.
93
What are the potential side effects of alkali agents?
The side effects of alkali agents are usually minor and gastrointestinal in nature, such as diarrhea, nausea, and abdominal discomfort.
94
In what conditions is potassium citrate used to alkalinize the urine?
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.
95
What are thiol-containing agents used for in the management of kidney and ureteral stones in children and adolescents?
Thiol-containing agents are used for patients with cystinuria in whom fluid/dietary modifications and urinary alkalinization are ineffective in preventing stone recurrences.
96
What are the two most common thiol-containing agents used for cystinuria?
The two most common agents are D-penicillamine and α-mercaptopropionylglycine (tiopronin).
97
How do thiol-containing agents work to prevent stone recurrences in patients with cystinuria?
These agents work by reducing the disulfide bond that bridges two molecules of cysteine.
98
What are the adverse side effects of D-penicillamine?
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).
99
Are the adverse effects of α-mercaptopropionylglycine similar to those of D-penicillamine?
Yes, the incidence of adverse effects for α-mercaptopropionylglycine is similar but may be slightly less.
100
What should be monitored regularly in patients taking thiol-containing agents?
Liver enzymes, complete blood count, urinalysis, and copper and zinc levels should be performed regularly in patients taking these medications.
101
What is the mainstay of therapy for most children with uric acid calculi?
The mainstay of therapy for most children with uric acid calculi is a combination of high urine output and urinary alkalinization.
102
What is the role of Allopurinol in the management of kidney and ureteral stones in children and adolescents?
Allopurinol is indicated in patients with both hyperuricemia and hyperuricosuria.
103
What is the recommended dose of Allopurinol for children and adolescents with kidney and ureteral stones?
The recommended dose of Allopurinol is 4–10 mg/kg/day, with an adult maximum of 300 mg/day.
104
What is the mechanism of action of Allopurinol?
Allopurinol inhibits xanthine dehydrogenase, leading to the accumulation and urinary excretion of xanthine.
105
What is a potential side effect of chronic therapy with Allopurinol in children with kidney and ureteral stones?
Rarely, a secondary xanthinuria with xanthine calculi is observed in children on chronic therapy.
106
When should Allopurinol be considered as the agent of choice for treating hyperuricosuric calcium oxalate urolithiasis?
Allopurinol may be the agent of choice for treating hyperuricosuric calcium oxalate urolithiasis if there is no concomitant evidence of hypercalciuria, hyperoxaluria, or hypocitraturia.
107
What is pyridoxine and why is it important in the management of children and adolescents with kidney and ureteral stones?
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.
108
What is PH1 and how is it related to pyridoxine sensitivity?
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.
109
How should pyridoxine be dosed in patients with suspected PH1?
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.
110
What are the potential side effects of large doses of pyridoxine?
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.
111
Clinical Vignette: A 10-year-old child presents with colicky pain in the abdomen. Upon imaging, a 7 mm ureteral stone is found. The parents are anxious and ask for treatment options.
Multiple-Choice Options:
A. Offer immediate surgical intervention.
B. Offer observation with or without medical expulsive therapy using α-blockers.
C. Proceed with percutaneous nephrolithotomy (PCNL) right away.
D. Order a CT scan.
Correct Answer: B
Explanation: According to the 2016 American Urological Association and Endourological Society Recommendations, in pediatric patients with uncomplicated ureteral stones less than 10 mm, observation with or without medical expulsive therapy using α-blockers should be offered. This offers a moderate net benefit and is supported by moderate certainty evidence.
Memory Tool: Think of "Small Stone, Small Steps" for ureteral stones less than 10 mm to remember observation or medical therapy.
Reference Citation: Table 43.3, Recommendation 1
Rationale: This information is vital for informing treatment decisions for pediatric patients with small ureteral stones. It sets a standard for when more invasive treatments should be considered.
112
Clinical Vignette: A 14-year-old boy is scheduled for PCNL to treat a renal stone. What imaging test should be performed before the procedure?
Multiple-Choice Options:
A. High-dose CT scan
B. Ultrasound
C. Low-dose CT scan
D. MRI
Correct Answer: C
Explanation: According to the guidelines, clinicians should obtain a low-dose CT scan on pediatric patients before performing PCNL. This is to ensure optimal treatment and is supported by low certainty evidence.
Memory Tool: Think "Low Dose, Less Risk" to remember a low-dose CT scan before PCNL.
Reference Citation: Table 43.3, Recommendation 3
Rationale: This question tests knowledge on preoperative imaging guidelines specific to pediatric patients, essential for minimizing radiation exposure.
113
Clinical Vignette: You're planning to perform a ureteroscopy (URS) for a 9-year-old with a 15 mm ureteral stone. Should a stent be placed prior to the URS?
Multiple-Choice Options:
A. Yes, always
B. No, not routinely
C. Only if the stone is larger than 20 mm
D. Only if the patient has anatomical abnormalities
Correct Answer: B
Explanation: The guidelines recommend not routinely placing a stent before URS in pediatric patients. This is a panel consensus based on members' clinical training, experience, knowledge, and judgment for which there is no evidence.
Memory Tool: Think "URS, No Strings Attached" to remember that stents are not routinely placed.
Reference Citation: Table 43.3, Recommendation 4
Rationale: Stent placement can cause additional discomfort and complications, and it's critical to know when it's not routinely recommended.
114
Clinical Vignette: A 12-year-old girl has been under observation for a ureteral stone. However, she shows no signs of passing the stone. What treatment options should you consider?
Multiple-Choice Options:
A. Continue with observation and medical expulsive therapy (MET) indefinitely.
B. Ureteroscopy (URS) or shock wave lithotripsy (SWL).
C. Open/laparoscopic/robotic surgery.
D. Active surveillance with periodic ultrasonography.
Correct Answer: B
Explanation: For pediatric patients with ureteral stones who are unlikely to pass the stones or who have failed observation and/or MET, URS or SWL should be offered. This is strongly recommended with moderate certainty.
Memory Tool: Think "Plan B, Go Big" for cases that fail observation and MET, indicating the need for URS or SWL.
Reference Citation: Table 43.3, Recommendation 2
Rationale: Knowing the next step after failed observation/MET is crucial in patient management to prevent complications like obstruction and infection.
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Clinical Vignette: You are treating a 13-year-old boy with a total renal stone burden of 18 mm. What would be your first-line therapy for this patient?
Multiple-Choice Options:
A. Open/laparoscopic/robotic surgery.
B. Shock wave lithotripsy (SWL) or ureteroscopy (URS).
C. Percutaneous nephrolithotomy (PCNL).
D. Active surveillance with periodic ultrasonography.
Correct Answer: B
Explanation: For pediatric patients with a total renal stone burden ≤ 20 mm, SWL or URS can be offered as first-line therapy. This comes with moderate net benefits and is supported by low certainty evidence.
Memory Tool: For stones "20 or Less, SWL or URS is Best."
Reference Citation: Table 43.3, Recommendation 5
Rationale: It helps differentiate the first-line treatment options based on the total renal stone burden, ensuring targeted and effective treatment.
116
Clinical Vignette: In which situation should open/laparoscopic/robotic surgery be considered for treating upper tract stones in pediatric patients?
Multiple-Choice Options:
A. Always, as it ensures complete stone removal.
B. Only in cases of coexisting anatomic abnormalities.
C. Never, as it is too invasive for pediatric patients.
D. When the total renal stone burden is > 20 mm.
Correct Answer: B
Explanation: Open/laparoscopic/robotic surgery should not be routinely performed for upper tract stones in pediatric patients, except in cases of coexisting anatomic abnormalities. This is a panel consensus based on clinical training, experience, knowledge, and judgment for which there is no evidence.
Memory Tool: Think "Anomaly? Open Policy" to remember when open/laparoscopic/robotic surgery is an option.
Reference Citation: Table 43.3, Recommendation 7
Rationale: The question emphasizes the need to understand exceptions to the rule against more invasive surgeries in pediatric patients.
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Question 7: Treatment for Pediatric Patients with Total Renal Stone Burden > 20 mm
Clinical Vignette: A 16-year-old patient presents with a total renal stone burden of 25 mm. What are acceptable treatment options for this patient?
Multiple-Choice Options:
A. Percutaneous nephrolithotomy (PCNL) only.
B. Shock wave lithotripsy (SWL) only.
C. Either PCNL or SWL, with stent or nephrostomy tube if SWL is used.
D. Ureteroscopy (URS) only.
Correct Answer: C
Explanation: For pediatric patients with a total renal stone burden > 20 mm, both PCNL and SWL are acceptable options. If SWL is utilized, clinicians should place an internalized ureteral stent or nephrostomy tube. This is a panel consensus.
Memory Tool: Think "Over 20? Two Ways with a Twist" to remember that both PCNL and SWL are options, but SWL requires an additional step.
Reference Citation: Table 43.3, Recommendation 6
Rationale: Knowing the tailored treatment options based on the size of the stone burden ensures that clinicians can offer the most appropriate care.
118
Clinical Vignette: A 7-year-old girl is found to have a nonobstructing renal stone on ultrasound but is asymptomatic. What's the next course of action?
Multiple-Choice Options:
A. Immediate surgical intervention.
B. Active surveillance with periodic ultrasonography.
C. Medical expulsive therapy using α-blockers.
D. Low-dose CT scan.
Correct Answer: B
Explanation: For pediatric patients with asymptomatic and nonobstructing renal stones, active surveillance with periodic ultrasonography may be utilized. This is a panel consensus based on members' clinical experience and judgment.
Memory Tool: Think "Silent Stone? Just Watch" to remember that asymptomatic and nonobstructing stones can be actively surveilled.
Reference Citation: Table 43.3, Recommendation 8
Rationale: The question focuses on conservative management options when surgical intervention is not necessary, providing an alternative approach in specific cases.
119
Clinical Vignette: You are planning a percutaneous nephrolithotomy (PCNL) for a 14-year-old boy. What preoperative imaging study is recommended?
Multiple-Choice Options:
A. Standard-dose CT scan
B. MRI
C. Low-dose CT scan
D. Ultrasound
Correct Answer: C
Explanation: Clinicians should obtain a low-dose CT scan on pediatric patients before performing PCNL. This is strongly recommended and supported by low certainty evidence.
Memory Tool: "Low-dose for the Little Ones" to remember that a low-dose CT scan is recommended before PCNL in pediatric patients.
Reference Citation: Table 43.3, Recommendation 3
Rationale: Knowing the correct preoperative imaging modality for a specific procedure can guide clinicians in ensuring patient safety and surgical success.
120
Clinical Vignette: You are considering ureteroscopy (URS) for an 11-year-old with a ureteral stone. Should you place a stent before the procedure?
Multiple-Choice Options:
A. Always, as it helps in guiding the URS
B. Never, as it increases the risk of complications
C. Only in cases with severe hydronephrosis
D. It should be individualized based on patient-specific anatomy
Correct Answer: B
Explanation: Clinicians should not routinely place a stent before URS in pediatric patients. This is a panel consensus based on clinical training, experience, knowledge, and judgment for which there is no evidence.
Memory Tool: "Stents Before? No More" to remember that stenting is not routinely recommended before URS.
Reference Citation: Table 43.3, Recommendation 4
Rationale: The question ensures that the examinee is aware of the recommendation against routine stent placement before URS, avoiding unnecessary interventions.
