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Types of Stones
Hyperoxaluria
Hyperoxaluria
from various causes results in the deposition of insoluble calcium
oxalate crystals in the kidney producing nephrocalcinosis and stone
formation.
Primary
(Inherited) Hyperoxaluria
Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive
disease caused by a deficiency of alanine: glyoxylate aminotransferase
(AGT). In this condition, hepatic overproduction of oxalate occurs.
The vast majority of families with PH1 show a horizontal autosomal
recessive pattern of inheritance. Treatment should include pyridoxine
(Vitamin B6) and magnesium supplementation as well as orthophosphate.
In
primary hyperoxaluria, type 2 (PH2), there is a deficiency of the
enzyme D-glycerate dehydrogenase/glyoxylate reductase. In contrast
to PH1, in which patient's progress to end stage renal failure (ESRF)
due to severe, bilateral nephrocalcinosis, patients with PH2 typically
present with nephrolithiasis without ESRF. The treatment of PH2
is mainly supportive. Unlike the benefits seen with vitamin B6 therapy
for the pyridoxine-sensitive patients with PH1, there is no effect
in PH2 patients.
Suggested
readings
Rumi LA, Pearle MS, Pak CYC. Medical therapy: Calcium oxalate urolithiasis.
Urol Clin North Am 1997, 24:1:117-133.
Hoppe
B, Danpure CJ, Rumsby G, Fryer P, Jennings PR, Blau N, Schubiger
G, Neuhaus T, Leumann E. A vertical (pseudodominant) pattern of
inheritance in the autosomal recessive disease primary hyperoxaluria
type 1: Lack of relationship between genotype, enzymic phenotype,
and disease severity. Amer J Kidney Diseases 1007, 29: 1: 36-44.
Kemper
MJ, Mullerwiefel DE. Nephrocalcinosis in a patient with primary
hyperoxaluria type 2. Pediatr Nephrol 1996, 10:4:442-444.
Enteric
Hyperoxaluria
Intestinal disease (malabsorption or short bowel syndrome) is the
most common cause of hyperoxaluria. Reduced availability of free
calcium to bind intestinal oxalate occurs in malabsorption. The
colon absorbs unbound oxalate. Other putative mechanisms include
increased colonic permeability and a decrease in Oxalobacter
formigenes (oxalate-degrading bacteria. Treatment includes calcium
citrate supplementation to bind intestinal oxalate and magnesium
and Vitamin B6 supplementation.
Suggested
readings
Rumi LA, Pearle MS, Pak CYC. Medical therapy: Calcium oxalate urolithiasis.
Urol Clin North Am 1997, 24:1:117-133.
Idiopathic
Hyperoxaluria
In this group of patients, the hyperoxaluria is generally mild.
Treatment consists of hydration and avoidance of foods containing.
If a low oxalate diet with adequate calcium intake does not normalize
urinary oxalate levels, Vitamin B6 may be added.
The
increase oxalate excretion in very low birth weight infants (VLBW)
is responsible for the high incidence of nephrocalcinosis and nephrolithiasis
in this group of patients. A spot urine for oxalate/creatinine ratio
is suitable for screening VLBW infants.
Suggested
readings
Rumi LA, Pearle MS, Pak CYC. Medical therapy: Calcium oxalate urolithiasis.
Urol Clin North Am 1997, 24:1:117-133.
Sonntag
J, Schaub J. The identification of hyperoxaluria in very low-birthweight
infants-Which urine sampling method? Pediatr Nephrol 1997, 11:2:205-207.
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