Metabolic Causes of Kidney Stones in Children

Introduction

Kidney stones are small and hard deposits of minerals and acids that form within an individual's urinary tract. It could block urine drainage, resulting in severe pain, nausea, and vomiting. However, the occurrence of kidney stones is uncommon in children. Children need a comprehensive metabolic evaluation of abnormalities rather than only stone clearance, as kidney stones can lead to morbidity in pediatric patients.

What Are the Types of Kidney Stones in Children?

When a large amount of salts accumulate within the kidneys as stones and crystals, it leads to the formation of kidney stones. Kidney stones can develop due to improper diet, nutrition problems, or other diseases. According to some studies, excessive salt intake can be a cause of kidney stone formation in children. Uric acid levels must be measured in children.

Some of the kidney stone types are:

• Cystine stones develop in children with cystinuria, a congenital disorder that leads to stone formation in the kidney, bladder, and ureter.

• Urinary tract infections lead to struvite stone formation.

• Uric acid stones form following treatment with chemotherapy or gout.

• Calcium stones form due to excessive salt intake.

What Symptoms Develop in Children With Kidney Stones?

Children with kidney stones exhibit various symptoms. The individuals may be asymptomatic to develop severe pain due to urinary obstruction. A few of the present symptoms are:

• Pain in the groin, abdomen, back, or side.

• Nausea or vomiting.

• Hematuria.

• Frequent urination.

• Urinary tract infection.

What Causes Kidney Stones in Children?

• Dehydration: More salt intake and more water in urine.

• Genetic Disorders: Rare genetic disorders or a family history of stones can increase incidence.

• Immobility: Children who cannot move for prolonged periods following surgery are likely to develop kidney stones. This is caused when children's bones are inactive and cannot regenerate themselves, causing the mineral bone to be flushed into their system.

• Drugs or their metabolites, such as Phenytoin and Triamterene.

• Melamine-contaminated milk powder consumption.

• In developing countries, an idiopathic cause has been attributed to the development of kidney stones.

What Are the Metabolic Causes of Kidney Disorders?

Metabolic abnormalities were noted in 30 to 86 percent of children with kidney stones. Some of the metabolic causes are:

• Hypercalciuria: Condition in which urine contains excess calcium. Causes could be genetic factors, high intake of calcium or vitamin D, or diseases that could affect calcium absorption and excretion. The primary metabolic cause of hypercalciuria is kidney stones.

• Hypocitraturia: A condition where urine has significantly less citrate levels. Citrate works by preventing calcium from forming stones. Causes for hypocitraturia are consuming significantly fewer amounts of fruits and vegetables, genetic factors, or medications that tend to reduce the urinary pH (potential of hydrogen). Hypocitraturia is common in children ingesting a ketogenic diet. Hypocitraturia is the second most common cause of kidney stones and is more prevalent in pediatric patients.

• Hyperoxaluria: Condition in which excess oxalate is present within the urine. Oxalate binds to calcium within the urine. Disorders that affect oxalate metabolism and absorption, high intake of food containing oxalate, and genetic factors could cause hyperoxaluria development. Hyperoxaluria is the third most common diagnosis of kidney stones.

• Cystinuria: A rare genetic condition in which too much cysteine is present. Cystine forms hexagonal crystals in the urine that can form larger and recurrent stones that are difficult to cure.

• Struvite Stones: The stones are composed of magnesium, ammonium, and phosphate. When children develop urinary tract infections, a bacteria known as urease is produced; it produces an enzyme that increases pH and forms kidney stones.

• Hypomagnesemia: There are very few reported cases in pediatric patients.

• Metabolic Disorders: Kidney stones can develop in metabolic disorders as inborn or late-stage conditions.

• Inborn Error in Purine and Pyrimidine Metabolism: It is associated with nephrolithiasis of various compositions. Most of them are characterized by hyperuricosuria and calcium stone formation.

• Glycogen Storage Disease Type 1: The condition is caused by glucose 6 phosphate deficiency. Renal calculi are the most commonly described renal complication. Hyperuricemia and urate kidney stones are the most common causes of kidney stone formation.

What Are the Risk Factors for Kidney Stones in Children?

The risk factors for kidney stones are:

• Metabolic Disorders: In children with metabolic disorders, the food is not adequately broken down, causing high oxalate and cystine levels in urine, leading to stone formation.

• Anatomical Malformation of Urinary Systems: In children with congenital anomalies of the kidney and urinary tract system, an anomaly of the urinary system increases the incidence of kidney stones.

• Dehydration: Children with inadequate fluid intake produce concentrated and dark urine. When insufficient fluids are available to dissolve minerals normally, there is an increased chance of kidney stones and crystal formation.

• Diet: Children consuming a high protein diet will have increased acid production in the body, which lessens the amount of urine citrate formation. A high salt diet causes large amounts of salt to be passed through the urine, pulling calcium and increasing the incidence of kidney stone formation. Eating food containing oxalates, such as tea, green leafy vegetables, and chocolate, can worsen symptoms.

• Family History: Children have a higher chance of developing kidney stones if there is a family history.

How Are Kidney Stones in Children Diagnosed?

The diagnostic tests are:

• Urine analysis.

• Kidney ultrasound.

• Abdomen X-ray.

• Abdomen CT (computed tomography) or MRI (magnetic resonance imaging).

How Are Kidney Stones Treated?

Most kidney stones pass through the urinary system and are eliminated from the body. Pain can be managed by taking painkillers. In case of infections in the urinary system, antibiotics are administered. In some children, medications are given to help the child pass stones through urine. Alpha-blocker administration can help relax ureter muscles and allow the passage of kidney stones more quickly with less pain.

For children with larger kidney stones that cannot be passed through urine, dietary modifications are recommended with medications. Doctors recommend dietary sodium restriction with intake of calcium as per the recommended daily allowance for children. High potassium and low oxalate levels are advised for children.

Surgical procedures may be advised for stone removal. Ureteroscopic stone extraction, percutaneous nephrolithotomy, open stone surgery, and extracorporeal shockwave nephrolithotomy are available surgical measures.

What Is the Prognosis for Children With Renal Stones?

Generally, the prognosis for children with renal stones is good. However, few children may have significant morbidity and mortality. Some may experience lifelong complications due to kidney stones.

Conclusion

The incidence of kidney stones has been increasing in recent years. Improper diet with high salt intake and metabolic risk factors are the common causes of renal stones. Timely diagnosis and treatment can prevent the risk of morbidity and mortality in children.