Giới thiệu
Urolithiasis is the formation of urinary stones in the kidney, bladder, and/or urethra.
Dịch tễ học
Urolithiasis is a painful urologic disorder that occurs in 12% of the global population and has a high recurrence rate of 71-80% among male patients. The prevalence is higher in males, and the incidence peaks around the age of 3 in children, reflecting endemic or primary stones in developing countries, and around age 60 in adults.
Stone incidence depends on geographical, climatic, ethnic, dietary, and genetic factors. Urinary stone prevalence varies widely, reported between 1% and 13%. Bladder stones account for only about 5% of all urinary tract stones but are responsible for 8% of urolithiasis related mortality in developed countries, with a higher incidence observed in developing nations. Incidence rates vary by region, ranging from 1-5% in Asia to 20.1% in Saudi Arabia, with 5-9% in Europe, 12% in Canada, and 13-15% in the United States.
Sinh lý bệnh
Kidney stone formation begins with urinary supersaturation, where substances such as calcium, oxalate, and phosphate exceed their solubility and form crystals. These crystals undergo nucleation, growth, and aggregation, eventually developing into stones. Low urine volume and low urinary pH increase this risk. Crystals may also attach to renal epithelial cells, causing cellular injury and inflammation, which further promotes crystal growth and aggregation.
Yếu tố nguy cơ
Urolithiasis can develop from a combination of genetic, environmental, and lifestyle factors. The family history may reveal genetic predisposition to cystinuria (types A, B, and AB), 2,8-dihydroxyandeneinuria, xanthinuria, renal tubular acidosis (RTA) type 1, primary hyperoxaluria, Lesch-Nyhan syndrome, and cystic fibrosis. General factors include early onset of urolithiasis (especially in children and teenagers), familial history of stone formation, brushite-containing stones (calcium hydrogen phosphate), uric acid and urate-containing stones, infection stones, solitary kidney, recurrent stone formation, short time since last stone episode, and chronic kidney disease. The dietary history of the patient should include the average daily intake of fluids (amount and specific beverages), eating habits (meals and snacks), calcium, sodium, high oxalate-containing food, and fruits and vegetables. Nutritional factors associated with stone diseases include calcium intake that is below or significantly above the recommended dietary allowance, low fluid intake, high sodium intake, limited intake of fruits and vegetables, and high intake of animal-derived purines.
Stone-provoking medications include Probenecid, some protease inhibitors, lipase inhibitors, Triamterene, chemotherapy, vitamins C and D, and carbonic anhydrase inhibitors (eg Topiramate, Acetazolamide, Zonisamide). Conditions associated with stone disease include obesity, gout, hyperthyroidism, renal tubular acidosis (RTA) type 1, diabetes mellitus (DM) type 2, bone disease (ie mineral bone disorder), primary hyperparathyroidism, bariatric surgery, bowel or pancreatic disease, nephrocalcinosis, sarcoidosis, jejunoileal bypass and intestinal resection, polycystic kidney disease, increased levels of vitamin D, and spinal cord injury and neurogenic bladder.
Anatomical abnormalities associated with stone formation include medullary sponge kidney (tubular ectasia), ureteropelvic junction (UPJ) obstruction, calyceal diverticulum, calyceal cyst, ureteral stricture, vesico-uretero-renal-reflux, horseshoe kidney, and ureterocele. Environmental and occupational factors include elevated ambient temperatures and long-term lead and cadmium exposure.
Phân loại
Classification of Urinary Stones
Urolithiasis_Disease Background 1Size
The size is usually given in one or two dimensions and stratified to those measuring up to 5, 5-10, 10-20, and >20 mm in the largest diameter. This has influence on the choice of urological treatment strategies.
Location
Stones are classified according to anatomical position: Upper, middle, or lower calyx; renal pelvis; upper, middle, or distal ureters; and urinary bladder. Bladder stones are further classified into primary, secondary, or migratory. Primary or endemic bladder stones develop in the absence of underlying urinary tract pathology and are typically seen in children living in areas with poor hydration, recurrent diarrhea, and diets low in animal protein. Secondary bladder stones arise in the context of underlying urinary tract abnormalities, including bladder outlet obstruction, neurogenic bladder dysfunction, chronic bacteriuria, and foreign bodies (eg catheters, bladder diverticula, bladder augmentation or urinary diversion). Migratory bladder stones originate in the upper urinary tract and enter the bladder, where they can act as a nidus for further stone growth.
X-ray Characteristics
Stones are classified according to plain X-ray appearance (eg kidneys, ureters and urinary bladder [KUB] radiography), which varies according to mineral composition. Radiopaque stones are calcium oxalate dehydrate, calcium oxalate monohydrate, and calcium phosphates. Radiolucent stones are uric acid, ammonium urate, xanthine, 2,8-dihydroxyadenine, and drug stones. Poor radiopacity stones are magnesium ammonium phosphate, apatite, and cystine. Non-contrast computed tomography (NCCT) is used to classify stones according to density, structure, and composition, which can influence treatment decisions.
Etiology of Formation
Stones may be caused by the following: Non-infectious (eg ammonium urate, calcium oxalate, calcium phosphate, uric acid); infectious (eg magnesium, ammonium phosphate, carbonate apatite, ammonium urate); genetic causes (eg cystine, xanthine, 2,8-dihydroxyadenine); and medications (eg Ciprofloxacin, Ephedrine, Indinavir, Magnesium trisilicate, Melamine, sulfa drugs, Triamterene). Further diagnostic tests and management depend on the composition of the stone. The risk status of the stone formers should be assessed because it will define the probability of recurrence or regrowth and is imperative for the choice of pharmacological treatment.
Analysis of Stone Composition
Urolithiasis_Disease Background 2The analysis of stone composition should be performed for all first-time stone formers and recurrent stone formers. The preferred analytical procedures are infrared spectroscopy and X-ray diffraction analysis of urinary stones. Knowledge of stone composition will help direct preventive measures and surgical interventions for future stones. Stones composed of uric acid, cystine, or struvite suggest specific metabolic or genetic abnormalities. Repeat stone analysis is needed in cases of recurrence after pharmacological intervention, early recurrence after interventional therapy with complete stone clearance, and late recurrence after a prolonged stone-free period since stone composition may change over time.
Stone Types
Calcium Stones (Oxalate and Phosphate)
Calcium stones are the most common type of kidney stone, with a high risk of recurrence. These are formed when there is a high level of calcium in the urine and characterized as either large and smooth or rough and spiky. The diseases and disorders related to calcium stones are as follows: Hypercalciuria (an inherited condition), renal tubular acidosis, nephrocalcinosis, primary hyperparathyroidism, kidney disease, sarcoidosis (granulomatous disease), primary hyperoxaluria, and enteric hyperoxaluria.
Struvite or Infection Stones
Struvite or infection stones have a high risk of recurrence. These are composed of magnesium ammonium phosphate and may originate de novo or grow on pre-existing stones infected with urea-splitting bacteria. Predisposing factors for stone formation are neurogenic bladder, spinal cord injury or paralysis, continent urinary diversion, ileal conduit, foreign body, stone disease, indwelling urinary catheter, urethral stricture, benign prostatic hyperplasia, bladder diverticulum, cystocele, caliceal diverticulum, and uteropelvic junction (UPJ) obstruction.
Uric Acid and Ammonium Urate Stones
Uric acid and ammonium urate stones have a high risk of recurrence. These are associated with hyperuricosuria or low urinary pH. Hyperuricosuria may be due to dietary excess, endogenous overproduction (enzyme defects), myeloproliferative disorders, tumor lysis syndrome, drugs, gout, and catabolism. Ammonium urate stones are rare and are associated with inflammatory bowel disease, ileostomy diversion, laxative abuse, potassium deficiency, hypokalemia, and malnutrition. Uric acid stones can also be seen in patients with chronic diarrhea, diabetes mellitus (DM), and metabolic syndrome. These stones form in the urine at pH >6.5 (ammonium urate crystals) and <5.5 (uric acid stones).
Cystine Stones
Cystine stones have a high risk of recurrence and chronic kidney disease. These are associated with low urinary pH and low urine volume. These are poorly soluble in urine and crystallize spontaneously within the physiological urinary pH. Clinical manifestations are the same for patients who are genotypic or phenotypic type of cystinuria.
Other Stone Types
2,8-Dihydroxyadenine Stones and Xanthine Stones
Xanthine stones and 2,8-dihydroxyadenine stones have a high risk of recurrence. Both stone types are rare, and the diagnosis and prevention are similar to that of uric acid stones. The genetically determined defect of adenine phosphoribosyl transferase causes high urinary excretion of 2,8-dihydroxyadenine. Decreased levels of serum uric acid are seen in patients who form xanthine stones.
Drug-Induced Stones
Drug-induced stones are induced by pharmacological treatment and exist as stones formed due to unfavorable changes in urine composition under drug therapy and/or by the crystallized compounds of the drug. Compounds that cause drug stones are Allopurinol/Oxypurinol, Amoxicillin/Ampicillin, Ceftriaxone, quinolones, Ephedrine, Indinavir and other human immunodeficiency virus (HIV)-protease inhibitors, Magnesium trisilicate, sulphonamides, and Triamterene. Substances impairing urine composition include Acetazolamide, Allopurinol, Aluminium magnesium hydroxide, ascorbic acid, calcium, Furosemide, laxatives, Losartan, Methoxyflurane, Orlistat, Topiramate, vitamin D, and Zonisamide.
Matrix Stones
Pure matrix stones are extremely rare. These are more prevalent among females. The main risk factors are urinary tract infections (UTIs) due to Proteus mirabilis or Escherichia coli, previous surgery for stone disease, chronic renal failure, and hemodialysis.