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Nephrolithiasis
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Abnormal |
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- Kidney Stones occur because substances in the blood filtered by the kidneys (made in to urine) tend to crystallize and precipitate in the urine. There are five major types of Kidney Stones: Calcium oxalate, Calcium phosphate, Uric acid, struvite, and cystine.
- Stones may occur in the kidney itself, or in the ureters (tubes that carry urine from the kidneys to the bladder). Kidney Stones are more common in warm climates during summer months, since Dehydration contributes to stone formation.
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- Severe pain in flank or low abdomen
- The pain may move from the flank to the low abdomen as the stone moves. The pain may also radiate to the testicles or vagina.
- May have increase urinary frequency and urgency
- May see Blood in the Urine
- Nausea/vomiting may occur
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- Tenderness in flank or
abdomen
- Plain X-Rays (KUB) show most stones (Calcium-containing stones and struvite are seen on X-Rays)
- Cystine stones cannot be seen
- Ultrasound is
helpful to find stones between the ureter and bladder
(ureterovesical junction)
- Intravenous pyelogram or spiral CT scan can make diagnosis if the above are not revealing
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- Initially, the patient is encouraged to keep well hydrated (drink lots of fluids), take pain medications, and wait to see if the Kidney Stones pass
without intervention. A screen filter is often given
to the individual to urinate through, in order to catch any
stones for later analysis.
- Stones in the ureter:
- Uteroscopy -- scope is passed up
the ureter and stone is retrieved
- Lithotripsy -- stones are broken up with Ultrasound
- Small stones (usually less than 3
cm) are treated with lithotripsy.
- Larger stones are treated by surgical removal (percutaneous nephrolithotomy). Antibiotics are given just before and after surgery.
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- If a stone is retrieved, it can be sent for analysis. The content of the stone will help determine what should be done for prevention. In addition, a 24-hour urine collection is evaluated for volume, pH, Calcium, Uric acid, oxalate, phosphate, and citrate. Additional 24-hour urine testing with specific dietary restrictions may be performed. Basic blood work, including a Complete blood count
and full chemistry panel, should be performed.
- Calcium Kidney Stones:
- Absorptive hypercalciuria (too much Calcium is excreted in the urine because too much Calcium is being absorbed from the intestine)
- Type I -- independent of Calcium in the
diet. Treated with cellulose phosphate or thiazide
diuretics
- Type II -- dependent on dietary Calcium (i.e., the more Calcium eaten, the more likely stones will form). The goal is to limit Calcium intake to
about 400mg/day.
- Type III -- this is due to phosphate loss into the urine, which causes more vitamin D to be made by the body, which in turn causes more Calcium to be absorbed by the intestine. Orthophosphates three times a day will replace the phosphate and stop the synthesis of the additional vitamin D.
- Resorptive hypercalciuria -- too much Calcium is
reabsorbed. This is due to Hyperparathyroidism. See section on Hyperparathyroidism
for treatment.
- Renal hypercalciuria -- the renal tubules do not efficiently deal with Calcium.
Hydrochlorothiazide and other
thiazide diuretics are used for treatment.
- Hyperoxaluric Calcium stones --
usually due to excess Diarrhea or inflammatory bowel syndromes in which Calcium is not available in the intestine to bind oxalate. As a result, it is absorbed and binds with Calcium in urine, to form Calcium oxalate
stones. Excess vitamin C may increase the risk of these types of stones. Keeping well hydrated may prevent them. Also, of course, treating any underlying condition such as ulcerative Colitis is
important.
- Hypocitraturic Calcium stones --
there is insufficient citrate to bind Calcium so there is more Calcium available to
bind to other substances and make stones. It is
caused by Chronic Diarrhea, Type
I renal tubular acidosis, or thiazide diuretic treatment.
- Hyperuricosuric Calcium stones --
due to over excretion of Uric acid. Small Uric acid crystals act as nidus (nucleus) for Calcium
stones. They are treated with dietary restrictions (of purines) or allopurinol.
- Uric acid kidney
stones -- these are due to excessively acidic urine that causes Uric acid to
precipitate in the urine. Contributing factors include high Uric acid in the blood, cancers, and increased Uric acid production,
dramatic weight changes up or down. Treatment includes
making the urine more alkaline, and this will usually
dissolve the stones.
- Struvite Kidney Stones -- these are composed of Magnesium-ammonium-phosphate. They are usually seen in women with repeated Urinary Tract Infections by urease-producing bacteria. These
bacteria include Proteus, Pseudomonas, and Klebsiella.
Antibiotics are needed. Acetohydroxamic acid inhibits
urease and is an effective treatment, but due to side
effects (gastrointestinal), it is not tolerated by most
patients.
- Cystine Kidney Stones -- these are due to an abnormal excretion of certain amino acids. Preventive measures include alkalinization of the urine and increased fluid intake. Penicillamine and Tiopronin medications may be considered.
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