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Synonym: oxalosis, oxaluria
See also the separate article on Urinary Tract Stones (Urolithiasis).
Hyperoxaluria is defined by the presence of excess amounts of oxalic acid (oxalate) in the urine.It is a relatively common finding in those who suffer from calcium oxalate renal tract stones. High concentrations lead to formation of calcium oxalate-apatite crystals and ultimately to nephrolithiasis.
Primary hyperoxaluria represents a group of genetic disorders resulting in endogenous overproduction of oxalate.Secondary hyperoxaluria results from gastrointestinal disorders associated with fat malabsorption and increased absorption of dietary oxalate.
- Primary hyperoxaluria:
- Type I - due to recessive mutation in gene encoding hepatic alanine-glyoxylate aminotransferase (AGXT). It leads to glycolic aciduria and hyperoxaluria. There is autosomal recessive inheritance and it is the most common of the primary hyperoxalurias.
- Type II - due to mutation in gene encoding hepatic glyoxylate reductase/hydroxypyruvate reductase (GRHPR). It leads to L-glyceric aciduria and hyperoxaluria.
- Type III - this has no identified enzyme deficiency. It may be due to inborn error of oxalate absorption/excretion or abnormality of peroxisome biogenesis.
- Enteric hyperoxaluria:
- Accounts for about 5% of cases of hyperoxaluria.
- Excess exposure to bile salts of bowel mucosa increases oxalate absorption.
- It is caused by a variety of intestinal disorders that tend to cause chronic diarrhoea.
- Loss of intestinal calcium leads to increased oxalate absorption and subsequent urinary excretion.
- Related conditions include jejuno-ileal bypass, small intestine resection, blind loops, Crohn's disease, and chronic pancreatic and biliary tract disease causing fat malabsorption (including cystic fibrosis).
- Idiopathic (mild) hyperoxaluria:
- It is by far the most common type of hyperoxaluria.
- It may be due to excessive oxalate intake in diet or increased endogenous production.
- It is likely to be more problematic in those with low urinary volumes.
- Provoked hyperoxaluria: excessive vitamin C intake, oxalate or ethylene glycol poisoning, inhalational anaesthetic reactions, urinary tract glycine irrigation, aspergillus infection, pyridoxine deficiency.
Overall, hyperoxaluria appears to be more of a problem in developed countries. Urolithiasis is undoubtedly common in the UK, although exact figures are hard to come by. Oxalate stones are the most common kind of urinary tract stone.
- Idiopathic hyperoxaluria (including dietary causes) is usually asymptomatic until complications of nephrolithiasis develop.
- Primary hyperoxaluria:
- It may present in the first months of life with seizures, advanced renal failure and few, if any, calculi but dense nephrocalcinosis.
- Patients normally present in childhood with recurrent urolithiasis.
- Death from renal failure usually occurs before age 20 years if untreated but a minority of patients may have a more benign course.
- The latter stages of disease are associated with dense calcium oxalate nephrocalcinosis and development of ischaemic lesions in the extremities (especially in the pads of the fingers and toes).
- There is also a progressive peripheral neuropathy.
- The normal clinical course is of recurrent stones leading inevitably to renal failure.
- 24-hour urine sample to assess daily urinary oxalate excretion (and 24-hour urinary creatinine excretion/clearance to ensure collection is adequate). Consider also measuring:
- Other products that lead to stone formation, such as calcium, urate, sodium and phosphate.
- Inhibitors of stone formation (for example, potassium citrate and magnesium).
- 24-hour urinary volume and pH (to assess contribution of dehydration and pH to stone formation).
- Check U&E to assess renal function.
- If primary hyperoxaluria is possible, perform percutaneous needle liver biopsy for AGXT or GRHPR activity assay.
- Imaging studies. There are no specific tests for hyperoxaluria. However, studies may be useful to detect and assess; for example, any urolithiasis and/or hydronephrosis, including intravenous pyelogram (IVP), ultrasound and CT/MRI scanning.
- A dietary questionnaire may help to detect:
- Those with excessive oxalate consumption (for example, spinach, rhubarb, cranberry, nuts).
- Excessive vitamin C consumption (controversial).
- High meat protein consumption.
- A record of fluid intake may help to detect those patients who may benefit by drinking more.
- Primary hyperoxaluria:
- Definitive cure is by early liver and kidney transplantation.[3, 4, 5]
- Pyridoxine can be used and should be continued if urinary oxalate monitoring shows a beneficial response.
- Magnesium hydroxide/oxide chelate with oxalate in the intestinal tract and can reduce absorption.
- Urinary volumes should be maintained at 3-4 L/day.
- Glycosaminoglycans such as pentosan polysulfate are also used with some success.
- Oxalobacter formigenes is a bacterium which degrades oxalate. Ingestion may be a treatment for primary hyperoxaluria.[4, 6]
- Intensive dialysis is needed when there is renal failure (more than is required for simple uraemia).
- All patients who do not respond to pyridoxine eventually require liver transplantation ± renal transplant.
- Ultimately it is hoped that gene therapy may help in this condition.
- Enteric hyperoxaluria:
- Patients should eat low-fat meat and have a diet low in oxalate.
- Calcium citrate supplementation is the most effective treatment.
- Potassium citrate can be given to increase urinary pH and citrate levels which reduce stone formation.
- Colestyramine and organic marine hydrocolloid may also be used to reduce oxalate absorption.
- Organic marine colloid may be helpful in binding oxalate in the gut and reducing urinary excretion.
- Treatment of underlying enteric causes may be helpful.
- Idiopathic hyperoxaluria:
- Dietary oxalate restriction and maintenance of high urinary flow. Avoid foods such as spinach, rhubarb, nuts, beetroot, chocolate, wheat bran, tea and excessive meat intake which increase oxalate absorption.
- Pyridoxine may be trialled and continued in those who show reductions in urinary oxalate restriction.
- Phosphate and magnesium supplementation may be used.
- Avoid excessive vitamin C intake.
- Increase fluid intake (more than 1.5 L per square metre per day).
- Administration of an oxalate-degrading bacterium such as O. formigenes, which breaks down oxalate in the intestine, may prove a useful therapeutic avenue. These bacteria appear to be deficient in some patients with hyperoxaluria, but achieving reliable gut colonisation has been difficult.[8, 9]
Hyperoxaluria can cause not only nephrolithiasis and nephrocalcinosis, but also renal parenchymal disease with deposition of calcium oxalate crystals throughout the kidney, severe tubular damage and interstitial inflammation and fibrosis. Hyperoxaluric nephropathy presents clinically as acute kidney injury or chronic kidney disease that may progress to end-stage renal disease (ESRD).
Further reading and references
Hyperoxaluria, Primary, Type I, HP1; Online Mendelian Inheritance in Man (OMIM)
Hyperoxaluria, Primary, Type II, HP2; Online Mendelian Inheritance in Man (OMIM)
Lorenz EC, Michet CJ, Milliner DS, et al; Update on oxalate crystal disease. Curr Rheumatol Rep. 2013 Jul15(7):340. doi: 10.1007/s11926-013-0340-4.
Salido E, Pey AL, Rodriguez R, et al; Primary hyperoxalurias: disorders of glyoxylate detoxification. Biochim Biophys Acta. 2012 Sep1822(9):1453-64. doi: 10.1016/j.bbadis.2012.03.004. Epub 2012 Mar 14.
Ellis SR, Hulton SA, McKiernan PJ, et al; Combined liver-kidney transplantation for primary hyperoxaluria type 1 in young children. Nephrol Dial Transplant. 2001 Feb16(2):348-54.
Hoppe B, Latta K, von Schnakenburg C, et al; Primary hyperoxaluria--the German experience. Am J Nephrol. 2005 May-Jun25(3):276-81. Epub 2005 Jun 15.
Raju DL, Cantarovich M, Brisson ML, et al; Primary hyperoxaluria: clinical course, diagnosis, and treatment after kidney failure. Am J Kidney Dis. 2008 Jan51(1):e1-5.
Hoppe B, Beck B, Gatter N, et al; Oxalobacter formigenes: a potential tool for the treatment of primary hyperoxaluria type 1. Kidney Int. 2006 Oct70(7):1305-11. Epub 2006 Jul 19.
Shapiro R, Weismann I, Mandel H, et al; Primary hyperoxaluria type 1: improved outcome with timely liver transplantation: a single-center report of 36 children. Transplantation. 2001 Aug 1572(3):428-32.
Hoppe B, Leumann E, von Unruh G, et al; Diagnostic and therapeutic approaches in patients with secondary hyperoxaluria. Front Biosci. 2003 Sep 18:e437-43.
Hoppe B, von Unruh G, Laube N, et al; Oxalate degrading bacteria: new treatment option for patients with primary and secondary hyperoxaluria? Urol Res. 2005 Nov33(5):372-5. Epub 2005 Nov 13.
Robijn S, Hoppe B, Vervaet BA, et al; Hyperoxaluria: a gut-kidney axis? Kidney Int. 2011 Dec80(11):1146-58. doi: 10.1038/ki.2011.287. Epub 2011 Aug 24.
Glew RH, Sun Y, Horowitz BL, et al; Nephropathy in dietary hyperoxaluria: A potentially preventable acute or chronic kidney disease. World J Nephrol. 2014 Nov 63(4):122-42. doi: 10.5527/wjn.v3.i4.122.
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