In hyperoxaluria, there is increased excretion of oxalic acid in the urine. This causes the oxalic acid to precipitate with calcium to form the poorly soluble calcium oxalate, leading to concretion formation in the kidneys. The condition can cause kidney failure and systemic impairment of various tissues.
What is hyperoxaluria?
Hyperoxaluria is a serious condition characterized by increased excretion of oxalic acid in the urine. Oxalic acid is a metabolic end product that is normally rapidly broken down into carbon dioxide and water. However, if this breakdown does not function properly or if too much oxalic acid enters the organism through food, calcium oxalates, which are difficult to dissolve with calcium, can form and settle as urinary stones in the urinary organs. This damages the kidneys in particular. There are both primary and secondary forms of hyperoxaluria. Thus, primary hyperoxaluria is always genetically determined and can be divided into three types. In all three types, there are enzyme defects that lead to increased oxalic acid formation or decreased oxalic acid degradation in the organism. Oxalic acid must be excreted in the urine. In the process, it combines with calcium to form calcium oxalate, which crystallizes in the kidneys and, in some cases, in other organs as well. Secondary hyperoxaluria is often associated with other metabolic diseases that lead to elevated blood calcium concentrations. Furthermore, it is also caused by increased intake of foods containing oxalic acid.
Causes
Genetic defects are present in primary hyperoxaluria. For example, primary hyperoxaluria type I is an autosomal recessive metabolic disorder characterized by a defect in the liver enzyme glyoxylate aminotransferase. The enzyme is responsible for the conversion of glyoxylate to glycine. When this enzyme is non-functional, glyoxylate accumulates, which is then broken down into oxalic acid. In primary hyperoxaluria type II (PH II), the oxalic acid concentration is also increased. Here, the enzyme glyoxylate reductase/hydroxypyruvate reductase is defective. As a result, oxalate accumulates because glyoxylate can no longer be converted. In PH III, the enzyme 2-keto-4-hydroxy-glutarate aldolase is non-functional, which also leads to increased oxalic acid concentration. The oxalic acid must be excreted in the urine. However, at very high oxalic acid concentrations, it precipitates as a calcium salt and forms urinary stones in the kidneys. The constant deposition of calcium oxalate causes kidney inflammation and scarring reactions, which eventually impair kidney function. Furthermore, systemic oxalosis also occurs. In the context of oxalosis, precipitates of calcium oxalate form in many other organs because the concentration of oxalic acid in the blood is increased. The organs affected include vascular walls, eyes, heart muscle, skin, bones and the central nervous system. This results in typical impairments of the affected organs such as blindness, bone oxalosis, cardiac arrhythmia or anemia. Organ failure even threatens death. In the secondary forms of hyperoxaluria, there are often other underlying metabolic diseases that are associated with an increased release of calcium. Calcium then binds more strongly with existing oxalic acid to form oxalates, which in turn can precipitate. This occurs in hyperparathyroidism, Cushing’s disease, sarcoidosis, [[bone metastases]), multiple myeloma, or vitamin D overdose, among others. Furthermore, secondary hyperoxaluria can also develop with excessive dietary intake of oxalic acid. Oxalic acid is particularly abundant in rhubarb, sorrel, spinach, or cocoa products.
Symptoms, complaints and signs
The symptoms of hyperoxaluria can be varied. The course of the disease can vary greatly among individuals, even with the same form. The increased concentration of oxalates in the urine is typical. In most cases, stone formation occurs in the urinary organs. In primary hyperoxaluria, oxalate formation in the kidneys and other organs can be so massive that significant kidney damage and other tissue damage occur even in childhood. Other individuals with primary hyperoxaluria may experience only occasional formation of kidney stones at older ages.Overall, symptoms characterized by severe renal dysfunction, urinary stone formation, renal colic, hematuria, fever and renal failure occur. When the kidneys stop working effectively, oxalate concentrations in the blood also increase, which can lead to the formation of oxalosis in various tissues. Cardiac arrhythmias, hypertension, partial tissue necrosis (gangrene) and limited joint mobility then occur.
Diagnosis and course of the disease
Hyperoxaluria is diagnosed by measuring the concentration of oxalic acid in the urine. Oxalic acid excretion should not exceed 40 milligrams per day.
Complications
Hyperoxaluria causes kidney discomfort in most patients. Other tissues in the patient’s body may also be affected by the disease. This results in increased formation of stones in the kidneys, causing significant pain in the patient. The tissue of the kidneys and other organs can be severely damaged by hyperoxaluria, so that restrictions of these organs may be expected. Most patients also suffer from fever and a general feeling of illness. In the worst case, complete kidney failure can occur if hyperoxaluria is not treated early by a physician. Furthermore, high blood pressure occurs, which in the worst case can lead to a heart attack. Untreated hyperoxaluria leads to a reduced life expectancy. Acute emergencies can usually be treated with a high fluid intake. However, in severe cases, transplantation of various organs in the patient is necessary. In this case, complications or other discomforts may occur under certain circumstances. However, these depend on the exact circumstances of the disease and cannot be predicted in general.
When should you see a doctor?
If symptoms and complaints such as urinary stones, renal colic, or fever are noticed, hyperoxaluria may be underlying. A doctor should be consulted if symptoms persist for more than two to three days. If further symptoms develop in the course of the disease, such as signs of hematuria or renal dysfunction, the family doctor must be consulted immediately. In the event of serious complications such as cardiac arrhythmias or tissue necrosis, a visit to the hospital is indicated. In severe cases, the emergency physician should be called immediately. This applies in particular if the complaints occur quite suddenly and are associated with signs of failure. In this case, it is best to seek medical advice immediately. People who have been diagnosed with corresponding genetic defects are particularly susceptible to the development of hyperoxaluria. So are people with Cushing’s disease, sarcoidosis or hyperparathyroidism. Anyone who belongs to these risk groups is best advised to consult a doctor immediately if they have the above-mentioned symptoms. In addition to the family doctor, a specialist in internal medicine or a nephrologist can be consulted.
Treatment and therapy
Hyperoxaluria is initially treated by increasing fluid intake. Furthermore, inhibitors that prevent the crystal formation of calcium oxalate are administered. These include magnesium, citrate or bicarbonate. The urine is kept as alkaline as possible to keep calcium oxalate in solution. In patients who are very sensitive to vitamin B6, pyridoxine is substituted to reduce the production of oxalate. These treatments can delay the progression of severe primary hyperoxaluria. However, in many cases, combined kidney-liver transplantation is necessary in infancy to prevent enzyme-induced oxalate formation and save patients’ lives.
Prospect and prognosis
The prognosis of hyperoxaluria varies widely. If left untreated, it can have a very severe course. Primary hyperoxaluria type I has a particularly poor prognosis. Like the other two primary forms of the disease, it is genetically determined. Secondary hyperoxaluria is in turn caused by a different disease. Common to all hyperoxalurias, however, is the deposition of calcium oxalate in the organism. Due to the high degree of saturation with calcium oxalate in the urine, the crystals precipitate especially in the kidneys and cause severe renal dysfunction over time. The oxalates appear as kidney stones, which constantly damage the kidney tissue.However, the disease can also be mild until old age, with only occasional kidney stones being diagnosed. In other cases, however, such as primary hyperoxaluria type I, severe kidney damage occurs in early childhood. Without treatment, hyperoxaluria is then often fatal. The oxalosis (deposition of oxalate crystals) often spreads to the entire organism after the increasing functional impairment of the kidneys. The heart muscle, vessels, eye, skin, bones and central nervous system are then frequently affected. As a result, complications such as cardiac arrhythmias, blindness, untreatable anemia, vascular diseases or oxalate bone diseases occur. In some cases, the diseases are fatal. In many cases, even intensive therapy with high fluid administration and medicinal inhibition of crystal formation can only delay the course of the disease, but not prevent it. Sometimes a combined liver–kidney transplant must be performed.
Prevention
Prevention from primary hyperoxaluria is not possible because it is genetic. If there is a predisposition, foods containing oxalic acid should be avoided. Overall, the consumption of very large amounts of rhubarb, spinach, or cocoa-containing products should be limited, as these can lead to secondary hyperoxaluria if necessary.
Follow-up
In the case of hyperoxaluria, the affected person is primarily dependent on a rapid diagnosis with subsequent treatment to prevent further complications and discomfort from this disease. The sooner a doctor is consulted, the better is usually the further course of this disease. The affected person should therefore contact a doctor at the first symptoms and signs of hyperoxaluria, because in the worst case it can also lead to death. Self-healing cannot occur with this disease, so that treatment is always necessary. The measures of an aftercare are limited. In most cases, hyperoxaluria is treated with the help of medication. Care must be taken to ensure that the dosage is correct and that the medication is taken regularly. Especially in children, parents must check the correct intake and dosage. In case of side effects or interactions, a doctor should be contacted first. Furthermore, regular examinations of the internal organs are very important in order to detect damage to the internal organs and to treat it in time. Possibly, therefore, the life expectancy of the affected person is also limited or significantly reduced due to hyperoxaluria.
What you can do yourself
In most cases, the complaints can be avoided relatively easily by a change in diet. However, early detection of the disease also has a very positive effect on the course of the disease and can prevent discomfort and damage to the kidneys. As a rule, those affected by hyperoxaluria should avoid foods containing oxalic acid. The intake of products containing cocoa should also be restricted as far as possible. Furthermore, the affected person must avoid spinach or rhubarb in his diet. In most cases, hyperoxaluria does not represent a major restriction in the patient’s everyday life and food intake. Patients can reduce the oxalate in their bodies by taking pyridoxine. The only thing that needs to be taken into account is regular intake, so that no further complaints arise. The acute symptoms of the disease are usually treated by an increased intake of fluids. Since the disease can also damage the kidneys or the heart, those affected should attend regular check-ups. In the case of psychological complaints or depression, discussions with other sufferers of hyperoxaluria or with close confidants and parents often help.