Abstract
Nephrolithaises, which are also known as renal caculi and kidney stones, are stone-like deposits of acid salts and minerals that form within the kidneys when these substances exist in concentrations above the saturation point within the urine. This disease occurs more commonly in males and peaks between the ages of 30 and 50. Nephrolithiasis occurs more commonly in Caucasians than in Hispanics and is much less common in blacks. There is a family clustering of nephrolithiasis; men have a family history of kidney stones with a two to three times greater probability of suffering from this disease.
Variables that encourage the formation of renal calculi include the presence of red blood cells, urinary casts, low calcium diets, diets high in high fructose corn syrup and sodium, and other crystals that can form as nucleating nidus that may promote stone formation. Ambient temperature may also correlate with the increased formation of stones with a seasonal predilection for stone formation in the warmer southeast United States, during the summer months and in occupations exposed to high ambient temperatures (e.g., military deployments to hot desert climates). Urinary tract abnormalities such as horseshoe kidney may also increase the risk of nephrolithiasis. Some investigators believe that the obesity-metabolic syndrome-diabetes spectrum is also a risk factor for nephrolithiasis. The solubility of stone forming solutes can also be inhibited by the presence of citrate, glycoproteins, and magnesium. The pH of the urine can increase or decrease the incidence of renal calculi, depending on which type of kidney stone is being formed, with acidic pH encouraging calcium-based stone formation and discouraging formation of uric acid stones.
Keywords
nephrolithiasis, kidney stones, flank pain, hematuria, renal calculi, hyperuricemia, hypercalcemia, hyperparathyroidism, bariatric surgery, hypervitiminosis
ICD-10 CODE N20.0
Keywords
nephrolithiasis, kidney stones, flank pain, hematuria, renal calculi, hyperuricemia, hypercalcemia, hyperparathyroidism, bariatric surgery, hypervitiminosis
ICD-10 CODE N20.0
The Clinical Syndrome
Nephrolithiases, which are also known as renal calculi and kidney stones, are stone-like deposits of acid salts and minerals that form within the kidneys when these substances exist in concentrations above the saturation point within the urine. This disease occurs more commonly in males and peaks between the ages of 30 and 50. Nephrolithiasis occurs more commonly in Caucasians than in Hispanics and is much less common in blacks. There is a family clustering of nephrolithiasis; men have a family history of kidney stones with a two to three times greater probability of suffering from this disease.
Variables that encourage the formation of renal calculi include the presence of red blood cells, urinary casts, low calcium diets, diets high in high fructose corn syrup and sodium, and other crystals that can form as nucleating nidus that may promote stone formation. Ambient temperature may also correlate with the increased formation of stones with a seasonal predilection for stone formation in the warmer southeast United States, during the summer months, and in occupations exposed to high ambient temperatures (e.g., military deployments to hot desert climates). Urinary tract abnormalities such as horseshoe kidney may also increase the risk of nephrolithiasis. Some investigators believe that the obesity-metabolic syndrome-diabetes spectrum is also a risk factor for nephrolithiasis. The solubility of stone forming solutes can also be inhibited by the presence of citrate, glycoproteins, and magnesium. The pH of the urine can increase or decrease the incidence of renal calculi, depending on which type of kidney stone is being formed, with acidic pH encouraging calcium-based stone formation and discouraging formation of uric acid stones.
Renal calculi are most commonly calcium based, with calcium oxalate containing stones accounting for approximately 60% to 70% of stones ( Fig. 72.1 ). Calcium oxalate stones are seen in patients suffering from hyperparathyroidism, malabsorption postbariatric surgery, hypervitaminosis D, diets high in high oxalate foods such as nuts and chocolate, and in patients with chronic pancreatitis. Calcium phosphate stones are associated with hypercalciuria and urinary alkalization secondary to renal tubular acidosis or the use of topiramate and carbonic anhydrase inhibitors such as acetazolamide. Much less common are uric acid stones whose formation is thought to be associated with excessive protein intake, gout, low urine output, and acidic urine. Ammonium acid urate stones and struvite stones are also less common than calcium-containing stones. Ammonium acid stones are associated with inflammatory bowel disease, laxative abuse, and ileostomy. Struvite stones are most commonly associated with urinary tract infections with urease-positive bacteria that convert urea to ammonium. Disorders of cystine transport can also cause kidney stones.
Signs and Symptoms
Calculi can form in the intraparenchymal space, the calyx, and pelvis of the kidney, as well as the ureter and bladder. Variables, including the size of the calculus, its location, and the patient’s anatomy, will affect its clinical impact and symptomatology. The symptoms of nephrolithiasis are primarily the result of increased intraurinary tract pressure which stretches and stimulates nociceptive nerve endings in the urothelium. These pain impulses are carried via the afferent sympathetic and somatic nerves at the T11 to L1 levels.
The pain of nephrolithiasis tends to wax and wane and is often colicky in nature with spasm of the ureters and bladder occurring as stones pass distally. If the urinary obstruction is incomplete or intermittent, the pain will tend to wax and wane, with complete obstruction causing constant severe pain. Pain may be referred to the flank, groin, testicle, or labia with the location of the pain often reflecting the anatomic location at which the stone is obstructing the urinary system ( Fig. 72.2 ). Nausea and vomiting are frequently present as is hematuria. Urinary urgency, frequency, dysuria, and meatal pain is also common. The patient suffering from acute kidney stones may find it difficult to find a comfortable position and may pace the floor. Fever, rigors, and chills in patients with signs and symptoms thought to be caused by kidney stones are serious findings and immediate culture of urine and any retrieved calculi should be obtained and appropriate antibiotic therapy instituted.
