Published online May 6, 2015. doi: 10.5527/wjn.v4.i2.235
Peer-review started: July 24, 2014
First decision: August 14, 2014
Revised: August 29, 2014
Accepted: February 4, 2015
Article in press: February 9, 2015
Published online: May 6, 2015
Hyperoxaluria is characterized by an increased urinary excretion of oxalate. Primary and secondary hyperoxaluria are two distinct clinical expressions of hyperoxaluria. Primary hyperoxaluria is an inherited error of metabolism due to defective enzyme activity. In contrast, secondary hyperoxaluria is caused by increased dietary ingestion of oxalate, precursors of oxalate or alteration in intestinal microflora. The disease spectrum extends from recurrent kidney stones, nephrocalcinosis and urinary tract infections to chronic kidney disease and end stage renal disease. When calcium oxalate burden exceeds the renal excretory ability, calcium oxalate starts to deposit in various organ systems in a process called systemic oxalosis. Increased urinary oxalate levels help to make the diagnosis while plasma oxalate levels are likely to be more accurate when patients develop chronic kidney disease. Definitive diagnosis of primary hyperoxaluria is achieved by genetic studies and if genetic studies prove inconclusive, liver biopsy is undertaken to establish diagnosis. Diagnostic clues pointing towards secondary hyperoxaluria are a supportive dietary history and tests to detect increased intestinal absorption of oxalate. Conservative treatment for both types of hyperoxaluria includes vigorous hydration and crystallization inhibitors to decrease calcium oxalate precipitation. Pyridoxine is also found to be helpful in approximately 30% patients with primary hyperoxaluria type 1. Liver-kidney and isolated kidney transplantation are the treatment of choice in primary hyperoxaluria type 1 and type 2 respectively. Data is scarce on role of transplantation in primary hyperoxaluria type 3 where there are no reports of end stage renal disease so far. There are ongoing investigations into newer modalities of diagnosis and treatment of hyperoxaluria. Clinical differentiation between primary and secondary hyperoxaluria and further between the types of primary hyperoxaluria is very important because of implications in treatment and diagnosis. Hyperoxaluria continues to be a challenging disease and a high index of clinical suspicion is often the first step on the path to accurate diagnosis and management.
Core tip: Hyperoxaluria is a disorder characterized by increased urinary oxalate excretion. Primary hyperoxaluria is an inherited defect of oxalate metabolism while secondary hyperoxaluria is seen in states of increased ingestion of oxalate, its precursors or altered gut flora. These disorders can lead to recurrent renal stones, nephrocalcinosis and eventually end stage renal disease. Despite these common features, the sub types of hyperoxaluria differ in their pathogenesis, severity of clinical presentation and treatment plan. Prompt clinical recognition and distinction between these disorders is essential not only for timely intervention but also impacts prognosis in patients with hyperoxaluria.