Rigi10™ Malleable Penile Prosthesis
Also Known As
Amino acids - urine, Urine amino acids, Hyperaminoaciduria, Aminoacidopathy, Renal aminoaciduria, Overflow aminoaciduria, Generalized aminoaciduria
Definition
Amino-aciduria refers to the presence of excessive amino acids in the urine, often indicating a metabolic disorder.1 This condition occurs when the urine contains abnormally high amounts of amino acids, which are the building blocks for proteins in the body.2 In a healthy kidney, the glomeruli filter all amino acids out of the blood, and the renal tubules then reabsorb over 95% of the filtered amino acids back into the blood.3
Amino-aciduria can be classified into two main types based on the underlying mechanism:
1. Overflow amino-aciduria: Occurs when abnormally high concentrations of amino acids in the blood plasma overwhelm the resorptive capacity of the renal tubules, resulting in high concentrations of amino acids in the urine.4 This may be caused by congenital disorders of amino acid metabolism, such as phenylketonuria, or may be secondary to liver disease.3
2. Renal amino-aciduria: Occurs when the renal tubules are unable to reabsorb the filtered amino acids back into the blood, causing high concentrations of amino acids in the urine.5 This may be caused by a defect in the transport proteins in the renal tubule, as occurs in Hartnup disease, or may be due to damage to the kidney tubule, as occurs in Fanconi syndrome.4
Inherited aminoacidurias are caused by defective amino-acid transport through renal (reabsorption) and in many cases also small intestinal epithelia (absorption).6 These disorders can affect the metabolism of specific amino acids or groups of amino acids, leading to their accumulation in the blood and subsequent excretion in the urine.7
Clinical Context
Amino-aciduria is clinically significant as it often serves as a biomarker for various metabolic disorders, particularly inborn errors of amino acid metabolism.1 In clinical practice, amino-aciduria is detected through urine amino acid analysis, which is typically performed when a metabolic disorder is suspected based on clinical presentation or as part of newborn screening follow-up.7
The clinical significance of amino-aciduria varies depending on the underlying cause:
1. Diagnostic value: Amino-aciduria patterns can help identify specific metabolic disorders. For example, phenylketonuria (PKU) is characterized by elevated phenylalanine in both blood and urine.1 Similarly, maple syrup urine disease shows elevated branched-chain amino acids.7
2. Patient selection criteria: Patients who may require urine amino acid testing include those with unexplained developmental delay, neurological symptoms, unusual odor, failure to thrive, or a family history of metabolic disorders.5
3. Clinical management: For many amino acid disorders, dietary restriction of the offending amino acid is the mainstay of treatment.1 This approach led to the evolution of the field of “Metabolic Nutrition.”1 For example, in PKU, phenylalanine-restricted diets have been successful in preventing intellectual disability when started early.1
4. Expected outcomes: Early diagnosis and appropriate management of amino acid disorders can significantly improve outcomes. Without treatment, many of these disorders can lead to intellectual disability, developmental delay, neurological damage, and in some cases, death.1 However, with proper management, many patients can lead relatively normal lives.7
In Fanconi syndrome, a cardinal feature is generalized aminoaciduria, where virtually every amino acid is found in excess in the urine.6 However, there are typically no clinical consequences from this specific aspect of the syndrome because the losses are trivial in relation to dietary intake.6
Screening infants for increased levels of amino acids can help detect problems with metabolism early. Early treatment for these conditions may prevent complications in the future.2