Urinary Stones Urolithiasis Kidney stones Nephrolithiasis

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Urinary StonesUrolithiasisKidney stones
Nephrolithiasis

• Dr. salwa hamdi Gomaa
• Lecturer of chemical pathology
• MRI

Department of Medical Laboratory
Technology Faculty of Allied Medical Science
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Kidney stones

• Also known as nephrolithiasis, urolithiasis or
  renal calculi.
• Solid concretions ( crystal aggregations) of
  dissolved minerals in urine
• found inside the kidneys or ureters. They vary
  in size from as small as a grain of sand to as
  large as a grapefruit

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Cont.

• Kidney stones (calculi) are hardened mineral
  deposits that form in the kidney. They originate
  as microscopic particles and develop into stones
  over time. The medical term for this condition is
  nephrolithiasis, or renal stone disease.

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Location of Renal stones
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• A vast majority of stones will contain elements
  of calcium within them and therefore are easily
  seen on x-ray having the same density as bone.
• Depending on the size, number, and the location
  of the stone(s) as well as it's composition
  guides initial and then further management can be
  implemented.

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Renal stones

• Kidney stones occur in 1 in 20 people at some
  time in their life.
• Urolithiasis is rare in children. When present,
  it is often associated with specific metabolic
  disorders or anatomic abnormalities.
• For precipitation of crystals in urine to occur,
  the urine must be "supersaturated" for the
  precipitating crystal.

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• Stone formation secondary to infection and/or
  obstruction related to a congenital malformation
  of the urinary tract often present before the age
  of 5.
• Cystinuria, idiopathic calcium oxalate
  urolithiasis and primary hyperparathyroidism more
  often begin around puberty or in the mid-teens.

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Stone Formation

• Kidney stones form when there is a high level of
  mineral (s) i.e. calcium (hypercalciuria),
  oxalate (hyperoxaluria), or uric acid
  (hyperuricosuria) in the urine
• a lack of citrate in the urine or insufficient
  water in the kidneys to dissolve waste products.
• Urine normally contains chemicalscitrate,
  magnesium, pyrophosphatethat prevent the
  formation of crystals.

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Cont.

• Low levels of these inhibitors can contribute to
  the formation of kidney stones.
• Citrate is thought to be the most important
• The chemical composition of stones depends on the
  chemical imbalance in the urine.
• The four most common types of stones are
  comprised of calcium, uric acid, struvite, and
  cystine.

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Calcium Stones

• Approximately 85 of stones are composed
  predominantly of calcium compounds.
• The most common cause of calcium stone production
  is excess calcium in the urine (hypercalciuria).
• In hypercalciuria, excess calcium builds up in
  the kidneys and urine, where it combines with
  other waste products to form stones.
• Low levels of citrate, high levels of oxalate and
  uric acid, and inadequate urinary volume may also
  cause calcium stone formation.

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Cont.

• Calcium stones are composed of oxalate (calcium
  oxalate) or phosphate (calcium phosphate).
• Calcium phosphate stones typically occur in
  patients with metabolic or hormonal disorders
  such as hyperparathyroidism and renal tubular
  acidosis.
• These stones come in 2 different types -
  monohydrate and dihydrate.
• Calcium oxalate dihydrate stones usually break
  easily with lithotripsy.
• Monohydrate stones are among the most difficult
  stones to fragment.

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Cause of hypercalciuria.

• Increased intestinal absorption of calcium
  (absorptive hypercalciuria),
• excessive hormone levels (hyperparathyroidism),
• and renal calcium leak (kidney defect that
  causes excessive calcium to enter the urine)
• Prolonged inactivity also increases urinary
  calcium and may cause stones.
• Renal tubular acidosis (inherited condition in
  which the kidneys are unable to excrete acid)
  significantly reduces urinary citrate and total
  acid levels and can lead to stone formation.

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Calcium oxalate monohydrates

• Calcium oxalate dihydrates

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lithotripsy
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Uric Acid Stones

• Digestion produces uric acid.
• If the acid level in the urine is high or too
  much acid is excreted, the uric acid may not
  dissolve and uric acid stones may form.
• They are not visible on X-rays.
• Patients with gout often develop these stones.
• Uric acid stones form in acidic urine and often
  dissolve when the urine is alkalinized.

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Cont.

• Genetics may play a role in the development of
  uric acid stones, which are more common in men.
• Approximately 10 of patients with kidney stone
  disease develop this type of stone.

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Uric acid
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Struvite Stones

• Also called an infection stone, develops when a
  urinary tract infection (e.g., bladder infection)
  affects the chemical balance of the urine.
• Bacteria in the urinary tract release chemicals
  that neutralize acid in the urine, which enables
  bacteria to grow more quickly and promotes
  struvite stone development.
• They are capable of splitting urea into ammonia,
  decreasing the acidity of the urine and resulting
  in favorable conditions for the formation of
  struvite stones.

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Cont.

• Organisms which alkalinize the urine can cause
  struvite stones to form.
• Struvite stones are more common in women.
• The stones usually develop as jagged structures
  called "staghorns" and can grow to be quite
  large.

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Struvite
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Cystine Stones

• Cystine is an amino acid. Some people inherit a
  rare, congenital condition that results in large
  amounts of cystine in the urine. This condition
  (called cystinuria) causes cystine stones that
  are difficult to treat and requires life-long
  therapy.

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Cystine
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The key features to the formation of stones

• Family history,
• Age of onset,
• Fluid intake pattern,
• Diet, medications,
• History of infections.
• Certain stone formation has a genetic
  predisposition
• Some an autosomal recessive pattern, including
  cystinuria and primary hyperoxaluria,
• Some have an autosomal dominant pattern such as
  renal tubular acidosis (RTA) or the syndrome of
  idiopathic calcium oxalate urolithiasis.

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Causes and Risk Factors

• A low level of citrate is a risk factor for
  hypocitraturia.
• Congenital kidney defect that may increase
  urinary calcium loss and stone formation
  (medullary sponge kidney)
• Excessive parathyroid hormone, which causes
  calcium loss (hyperparathyroidism)
• Gout (caused by excessive uric acid in the blood)
  
• High blood pressure ( hypertension)
• Inflammation of the colon that causes chronic
  diarrhea, dehydration, and chemical imbalances
  (colitis)
• Sodium (hypernatremia)

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• Inherited condition in which the kidneys are
  unable to excrete acid (renal tubular acidosis)
• Painful joint inflammation (arthritis)
• Urinary tract infectious (affect kidney function)
  
• Diet plays an important role in the development
  of kidney stones. A diet high in sodium, fats,
  meat, and sugar, and low in fiber, vegetable
  protein, and unrefined carbohydrates increases
  the risk for renal stone disease.

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• High doses of vitamin C (i.e., more than 500 mg
  per day) can result in high levels of oxalate in
  the urine (hyperoxaluria) and increase the risk
  for kidney stones. Oxalate is found in berries,
  vegetables (e.g., green beans, beets, spinach,
  squash, tomatoes), nuts, chocolate, and tea.
• Stone formers should limit their intake of
  cranberries, which contain a moderate amount of
  oxalate.