Kidney stone overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Historical Perspective
Urinary stones was first discovered by E. Smith, an English archaeologist, in 1901 when he found bladder stone in Egyptian mummy aged 4500-7000 year. In the 4th century B.C., when Hipprocratic Oath was made,the line that refers to stones was mentioned: “I will not use the knife, not even on sufferers from stone, but will withdraw in favor of such men as are engaged in this work....I will not cut for the stone, but will leave this to be done by practitioners of this work.”In the 8th century B.C, treatment strategy for stone removal was developed by an Indian surgeon, Sushruta as written in Sushruta Samhita. In 1976, the first percutaneous stone surgery was performed by Fernstrom and Johansson. The famous cases of nephrolithiasis includes: in 1549, Michelangelo was diagnosed and treated for uric acid stones;in 1724, Sir Isaac Newton noted that he passed two small pea-sized stones and in 1961, Roger Moore, aka James Bond, experienced three kidney stone episodes and treated with surgery.
Classification
Nephrolithiasis may be classified according to [classification method] into 4 subtypes/groups: calcium stones, struvite stones, uric acid stones and cystine stones
Pathophysiology
It is understood that nephrolithiasis is the result of combination of different mechanism responsible for different types of stones. Calcium stones are the most common type of kidney stones. Approximately 80% of all calcium stones are calcium oxalate stones. The pathophysiology of calcium stones is complex and involves dietary concerns, hypercalciuria, hypocitaturia, hyperoxaluria, hyperuricosuria and biomineralization. The underlying pathophysiological mechanisms responsible for uric acid stones are low urine volume, hyperuricosuria and high acidic urine. Cystinuria is a rare hereditary gene disorder which causes impaired renal reabsorption of cationic amino acids and cystine. It is caused by mutations in either of the two subunits (rBAT(SLC3A2) and b0,+AT(SLC7A9)) forming cystine stones. Struvite stones are usually seen in patients which have infection with urease +ve organisms. Urine pH is usually alkaline (>7.2). Nephrolithiasis can be passed on to following generations due to rare causes of hypercalciuria such as hereditary distal renal tubular acidosis, dent disease, Bartter syndrome types III and IV, autosomal dominant hypocalcemic hypercalciuria and familial hypomagnesemia. Nephrolithiasis associated with Hyperparathyroidism, Gout, Hypocitaturia, Sarcoidosis, chronic urinary tract infections and Obesity.On gross pathology, the characteristic findings of nephrolithiasis include location = 80% unilateral, usually in calyces, pelvis or bladder. The size=variable, 2-3 mm usually. All stones contain an organic matrix of mucoprotein. The shape of struvite stone is staghorn shaped. On microscopic histopathological analysis, the characteristic findings of nephrolithiasis include different shapes of stones/crystals are such as cystine= hexagonal, struvite= coffin lid shape, calcium oxalate= pyramid shape to dumbbell shape and uric acid= rectangular/rhomboidal. Oxalate crystals are highlighted by polarized light. Also, foreign body giant cells and macrophages are seen with the stones.
Causes
The common causes of nephrolithiasis include hypercalcemia, hyperparathyroidism, hypercalciuria, infection with urea splitting microorganisms like Proteus and Pseudomonas, gout, dehydration, inflammatory bowel disease. Less common causes of nephrolithiasis include drugs such as loop diuretics, Acetazolamide, ciprofloxacin, indinavir, guaifenesin triamterene and magnesium trisilicate.
Differentiating Nephrolithiasis from Other Diseases
Nephrolithiasis should be differentiated from other conditions presenting with acute flank or upper abdominal pain, hematuria, nausea and vomiting.
Epidemiology and Demographics
In 2000, the incidence/prevalence of nephrolithiasis was estimated to be 116 cases per 100,000 individuals in the United States.The prevalence of nephrolithiasis is approximately 1116 per 100,000 individuals worldwide. It has increased from every 1 in 20 to 1 in 11 person in United States has kidney stones. According to American Journal of Kidney disease, 2016, 8% of women and 16% of men are developing nephrolithiasis by the age of 70 years. According to 2000 National Hospital Ambulatory Medical Care Survey of the United State,s there is an annual burden of more than 1,100,000 emergency department visits with a primary diagnosis of renal calculus or colic. Patients of all age groups may develop nephrolithiasis. The incidence of nephrolithiasis increases with age. At initial diagnosis, the mean age was 44.8 years in men and 40.9 years in women. Nephrolithiasis usually affects individuals of the white/Caucasian ethnicity. Males are more commonly affected by nephrolithiaisis than females. The male to female ratio is approximately 2 to 1. The trend keeps on changing , a study in 2010 claims the incidence rate ratio of men to women with urinary tract stones has narrowed from 3.4 to 1.3. Females are having increasing incidence rates owing to increase lifestyle disease like obesity. The majority of nephrolithiasis cases are reported in southeast belt of the United States. The number of cases increase from north to south and from west to east. The states of North Carolina, South Carolina, Georgia, Alabama, Mississippi, and Tennessee are considered in the “stone belt.” The ambient temperature and sunlight levels as risk factors for stones and differences in exposure to temperature and sunlight and beverages are also responsible for geographic variability.
Risk Factors
Screening
Natural History, Complications, and Prognosis
Diagnosis
Diagnostic Study of choice
History and Symptoms
Physical Examination
Laboratory Findings
Electrocardiogram
X-ray
An x-ray may be helpful in the diagnosis of nephrolithiasis. Findings on an x-ray suggestive of nephrolithiasis include radiopaque stones such as Calcium oxalatecalcium phosphate, struvite and radiolucent stones which includes uric acid stones and cystine stones.