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Kidney stones (renal calculi, nephrolithiasis) are stone-like masses formed in the kidneys. Ureteral calculi are stones that originated in the kidneys but are found in the ureters. Normal urine contains predictable amounts of calcium, magnesium, uric acid, and other by-products of metabolism. These substances normally remain in solution and pass from the kidneys, down the ureters, into the bladder, and out of the body. When the concentration of these minerals and by-products in urine becomes too high, they form solid crystals on the inner surfaces of the kidneys. Over time, these crystals may accumulate to form small, hard, stone-like particles in the kidneys. Calcium-containing calculi are the most common type of renal calculi, comprising 60% to 80% of all urinary tract stones (Parmar).
In many cases, formation of renal calculi has no identifiable underlying cause (idiopathic). Rare inherited diseases such as renal tubular acidosis and cystinuria are associated with calculus formation, as are gout, blockage of the urinary tract, urinary tract infection, excess intake of vitamin D, polycystic kidney disease, and hyperparathyroidism. Intestinal bypass procedures and ostomy surgery are associated with an increased incidence of renal calculi.
Risk: Risk factors for developing renal and ureteral calculi include lack of fluids (dehydration), family or personal history of calculi or certain metabolic disorders, diet, a sedentary lifestyle, and use of certain drugs such as diuretics or indinivir (a drug used in the treatment of HIV). Renal calculi also are common after long periods of immobilization.
Men are 2 to 4 times more likely to develop urinary tract calculi than women (Fathallah-Shaykh, Parmar, Smith). However, renal calculi formed secondary to infection are more common in women than in men (Wolf).
Although the majority of urinary tract calculi develop in individuals between the ages of 20 to 49 (Wolf), the peak age of formation in men is age 30 and in women is age 35, with a second peak at age 55 (Parmar). Caucasians are more prone to develop calculi than African-Americans, Asian-Americans, or Hispanics (Fathallah-Shaykh). A high-protein diet, heredity, or living in hot, dry regions also increases the risk (Wolf).
Incidence and Prevalence: Between 5% and 12% of Americans will develop renal calculi at some point in their lives (Smith) with an annual incidence of 0.2% (Wolf).
Annual incidence of renal calculi in most developed countries is similar to the United States (Wolf). |
Source: Medical Disability Advisor
History: Symptoms vary according to the site and size of the stone. Small calculi frequently cause no symptoms until they begin to pass from the kidney into the ureter. The resulting pain (renal colic) often is excruciating and intermittent. Individuals may report pain that starts on the far right or far left side of the back (flank) and then moves toward the groin. Severe pain may precipitate nausea and vomiting. This can then result in significant dehydration. Bloody urine (hematuria) occurs in 90% of cases (Smith). Cloudy or foul-smelling urine also may be noted, as may fever, chills, and frequent urination. If the urethra is blocked, the individual may report being unable to urinate.
Physical exam: The individual will appear to be in severe pain. This may result in blood pressure elevation. Tapping softly on the flank often worsens the pain. If the urethra is blocked, light pressure applied with the fingertips (palpation) to the lower abdomen may reveal an enlarged and tender bladder (bladder distention).
Tests: Microscopic examination of the urine may reveal large numbers of red blood cells (hematuria), white blood cells (pyuria), and the presence of mineral crystals. A urine culture should be performed to check for evidence of infection. X-ray studies of the kidneys, ureters, and bladder (KUB) can confirm the presence of most renal calculi and show the site of the stone. The most definitive test is an x-ray of the kidneys taken after contrast medium is injected into the arm (intravenous pyelogram, [IVP]). This test can confirm the site of the calculus and indicate if there is obstruction of the urinary tract. CT scan and ultrasound scanning can also monitor obstruction.
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Source: Medical Disability Advisor
In 80% of individuals, calculi less than 4 millimeters in diameter are passed into the bladder with relatively few problems (Smith). Stones that are 4 to 6 millimeters will spontaneously pass into the bladder in 50% of individuals, but only 20% of calculi larger than 8 millimeters will do so (Smith). Fluid intake is increased to encourage the passage of the calculi from the kidney, through the ureter, into the bladder, and out through the urethra. Walking also is encouraged, as this facilitates passage of calculi. A renal calculus may take from 1 to 3 weeks to pass on its own (Parmer).
Approximately 20% of renal calculi are not spontaneously voided (Smith). Treatment may be necessary when a calculus does not pass after a reasonable period of time and causes constant pain or if it is too large to pass naturally. Treatment also is required when a calculus blocks the flow of urine, causes chronic urinary tract infection, damages kidney tissue, causes bleeding, or is enlarging. Several treatment modalities may be considered.
Extracorporeal shock wave lithotripsy (ESWL) uses shock waves originating outside the body to fragment calculi, making the pieces small enough to pass with urination. This procedure usually is performed using general or local anesthesia. A small, hollow tube (stent) may temporarily be inserted into the ureter to assist in locating the stone and helping the fragments pass following treatment. ESWL is the least invasive procedure but may need to be repeated, as it may not adequately fragment all calculi.
Ureteroscopy (URS) involves the use of an ureteroscope, a tube that is inserted into the ureter and up the urinary tract to the location of the calculus via cystoscopy. This allows the urologist to directly view the stone. Various devices can then be passed into the ureter in order to remove or fragment the calculus. This procedure usually is performed under anesthesia. A stent is left in the ureter for several days after treatment.
If a calculus is in a location that does not allow ESWL or results in blockage that cannot be bypassed with a stent, a surgeon may need to perform a percutaneous nephrolithotomy. Through a small incision in the flank, a nephroscope is used to locate and surgically remove the calculus. For larger calculi, a type of energy probe (ultrasonic, electrohydraulic, or hydraulic) may be used to shatter the stone. This procedure is performed using sedation or general anesthesia.
Open surgery for calculus removal is rarely necessary. This is the most invasive form of treatment. In open surgery, the ureter and/or kidney are exposed and the calculus is directly removed
If calculi are caused by a metabolic disorder, the individual may be treated with changes in diet and with drugs to lower the urine content of the substance from which the calculi are formed. Increased fluid intake may be necessary to help dissolve existing calculi and reduce the chance of recurrence. In individuals with hyperparathyroidism, removing the parathyroid tumor responsible for the condition may prevent recurrence.
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Source: Medical Disability Advisor
In most cases, the outcome of treatment is excellent whether the calculus passes without incident or the individual requires a procedure to effect its removal. However, people who have had one renal calculus are more likely to develop others. Calculi recur in 10% of individuals within the first year (Smith) And about half of all individuals treated for a renal calculus will have a recurrence within 5 to 10 years (Parmar, Smith).
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Source: Medical Disability Advisor
Renal and ureteral calculi may be associated with recurrent episodes of urinary tract infection. Any obstruction to urine flow may result in urinary tract and/or kidney damage (acute or chronic obstructive uropathy or nephropathy) or severe kidney infection (pyelonephritis). Renal failure, and, in rare cases death, may result.
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Source: Medical Disability Advisor
Individuals who are in the midst of passing a renal calculus are unable to work, but generally may resume work without restrictions once the stone passes. Those who have jobs in which the sudden and severe pain from a calculus could cause a safety risk (e.g., heavy-equipment operators, construction workers, drivers) may need to stay home or temporarily be assigned alternative duties when experiencing problems with renal calculi. Individuals with calculi may require restrictions on bending, stooping, and heavy lifting. All will require frequent access to fluids and more frequent bathroom breaks to aid in hydration and passing the stone. Those who are hospitalized will need from several days to weeks for recovery, depending on the procedure performed while in the hospital. If pain medication is used, company policy on medication usage should be reviewed to determine if medication use is compatible with job safety and function.
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Source: Medical Disability Advisor
| If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case. Regarding diagnosis:
- Has diagnosis of renal or ureteral calculus been confirmed through imaging studies (x-ray studies, ultrasound scanning, CT scan)?
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Has IVP been done to determine site and size of the calculus and whether there is obstruction?
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Has urine culture been done to determine the presence of infection?
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Has individual experienced any complications associated with renal or ureteral calculi?
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Does individual have an underlying condition such as a metabolic disorder or hyperparathyroidism that may affect recovery or recurrence?
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Regarding treatment:
- Does discomfort persist despite the passage of small calculi? Could additional, larger calculi still be present?
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Was ESWL successful in disintegrating the calculus into pieces small enough for easy passage? If not, was ultrasonic lithotripsy, electrohydraulic lithotripsy, or laser lithotripsy used?
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If not successfully removed via ureteroscope, what procedure was used for removal of calculus from ureter?
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Is individual compliant with prescribed diet, drug therapy, and increased fluid intake?
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Have calculi recurred?
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If calculi are associated with hyperparathyroidism, has one or more of the parathyroid glands been removed? Has this been effective in correcting the metabolic abnormalities of hyperparathyroidism?
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Regarding prognosis:
- With larger calculi, or if an infection or obstruction to the urinary flow is present, was surgical intervention required to prevent damage to kidney? What is the prognosis associated with that specific procedure?
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Does individual have a personal or family history of renal or ureteral calculi?
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What is being done to reduce risk factors for recurrence?
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Source: Medical Disability Advisor
| CitedFathallah-Shaykh, S., and R. Neiberger. "Urolithiasis." eMedicine. 22 Apr. 2008. Medscape. 24 Jul. 2009 <http://emedicine.medscape.com/article/983884-overview>.Smith, J. K., et al. "Nephrolisthiasis/Urolisthiasis." eMedicine. Eds. S. Perlmutter, et al. 21 Feb. 2007. Medscape. 24 Jul. 2009 <http://emedicine.medscape.com/article/381993-overview>. Wolf, J. S. "Nephrolisthiasis." eMedicine. Eds. Stephen W. Leslie, et al. 10 Dec. 2008. Medscape. 24 Jul. 2009 <http://emedicine.medscape.com/article/437096-overview>. Parmar, M. S. "Kidney Stones." BMJ 328 7453 (2004): 1420-1424. National Center for Biotechnology Information. National Library of Medicine. 12 Oct. 2009 <PMID: 15191979>. |
Source: Medical Disability Advisor
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