You are in: eMedicine Specialties > Pediatrics: General Medicine > Nephrology Renal GlucosuriaArticle Last Updated: May 8, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Leonard G Feld, MD, PhD, MMM, Chairman of Pediatrics, Carolinas Medical Center; Chief Medical Officer, Levine Children's Hospital, Carolinas Healthcare System Leonard G Feld is a member of the following medical societies: American Academy of Pediatrics, American College of Physician Executives, American Heart Association, American Physiological Society, American Society of Nephrology, American Society of Pediatric Nephrology, American Society of Transplant Surgeons, Eastern Society for Pediatric Research, International Society of Nephrology, Juvenile Diabetes Foundation International, National Kidney Foundation, Society for Experimental Biology and Medicine, and Society for Pediatric Research Editors: Laurence Finberg, MD, Clinical Professor, Department of Pediatrics, University of California at San Francisco and Stanford University; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Luther Travis, MD, William W Glauser Professor of Pediatrics and Pediatric Nephrology, Department of Pediatrics, Divisions of Nephrology and Diabetes, University of Texas Medical Branch and Children's Hospital; Howard Trachtman, MD, Program Director, Pediatrics Research, Schneider Children's Hospital, Department of Pediatrics, Division of Nephrology, Professor, Albert Einstein College of Medicine; Craig B Langman, MD, The Isaac A Abt, MD, Professor of Kidney Diseases, Feinberg School of Medicine, Northwestern University; Division Head of Kidney Diseases, Children's Memorial Hospital, Chicago Author and Editor Disclosure Synonyms and related keywords: renal glucosuria, renal glycosuria, glucose in urine, Fanconi syndrome, cystinosis, Wilson disease, hereditary tyrosinemia, oculocerebrorenal syndrome, Lowe syndrome, hyperglycemia, diabetes mellitus, hypophosphatemic rickets, dehydration, short stature, Kayser-Fleischer ring INTRODUCTIONSection 2 of 10
  BackgroundRenal glucosuria is the excretion of glucose in the urine in detectable amounts at normal blood glucose concentrations or in the absence of hyperglycemia. In general, renal glucosuria is a benign condition and does not require any specific therapy. Glucosuria may be associated with tubular disorders such as Fanconi syndrome, cystinosis, Wilson disease, hereditary tyrosinemia, or oculocerebrorenal syndrome (Lowe syndrome). PathophysiologyGlucose is freely filtered by the glomerulus with a fractional excretion of less than 0.1%. Adults excrete about 65 mg of glucose per day. Reabsorption of glucose occurs predominantly on the brush border membrane of the convoluted segment of the proximal tubule. Glucose enters the tubular cells by an active carrier-mediated transport process, which is sodium dependent, and exits via the basolateral membrane by facilitated diffusion by a glucose transporter, which is sodium independent. The sodium/glucose cotransporter is part of the SGLT1 group of sodium cotransport proteins. The human intestinal SGLT1 has been localized to chromosome 22. SGLT1 is found in the straight segment of the proximal tubule. The other cotransporter is SGLT2, which is expressed in the S1 segment of the proximal tubule and is localized to chromosome 6. The facilitative glucose transporters have isoforms GLUT 1-5. GLUT2 mainly is associated with glucose transport in the convoluted portion of the proximal tubule. In segments with high reabsorptive rates (S1 and S2 segments), the carrier is high capacity, low affinity. At birth, a high-affinity low-capacity pathway also exists to compensate for the reduced activity of the high-capacity low-affinity pathway. Glucose reabsorption is age dependent. In premature infants of less than 30 weeks' gestation, glucosuria is quite common because the filtered load of glucose delivered to the kidney often is too high for the immature nephron to handle. Glucosuria normally occurs when the plasma glucose content is above 300 mg/dL, but some glucose may be seen in the urine at plasma glucose levels as low as 150 because there is a great deal of variability in the glucose-handling capacity of individual nephrons. This variability arises from variation in the length of the proximal tubule and differences in glomerular size and location. Tubular maximum for glucose (Tm glucose, mg/min/1.73 m2) corrected for the glomerular filtration rate (GFR) does not vary as a function of age. Tm glucose/GFR (mg/mL) presents as follows:
The Tm glucose for children expressed in mg/min/1.73 m2 is as follows:
FrequencyUnited StatesIncidence is estimated at 0.16-6.3%. Mortality/MorbidityRenal glucosuria is a benign condition. However, morbidity is significant in Fanconi syndrome, Lowe syndrome, and cystinosis (see Differentials). CLINICALSection 3 of 10
HistoryMedical history offers no clues for either primary or benign renal glucosuria. In cases associated with combined tubular defects or hyperglycemia (ie, diabetes mellitus), history is specific to the disease or syndrome. Renal glucosuria is first noted on routine urinalysis. In cases of glucosuria associated with tubular disorders, a history of growth failure, polyuria, polydipsia, or dehydration may exist. PhysicalNo physical examination findings are relevant to renal glucosuria, unless associated with a secondary cause (eg, Fanconi syndrome, diabetes mellitus). In cases associated with tubular disorders, signs or symptoms may include hypophosphatemic rickets, dehydration, short stature, muscle hypotonia, or ocular changes of cataracts or glaucoma (Lowe syndrome) or Kayser-Fleischer ring (Wilson disease). CausesThe renal abnormality is specific to glucose and not other monosaccharides. The inheritance pattern is autosomal recessive, although autosomal dominance has been reported. Glucosuria can be divided into 3 clinical scenarios, as follows:
DIFFERENTIALSSection 4 of 10
Cystinosis Diabetes Mellitus, Type 1 Fanconi Syndrome Oculocerebrorenal Dystrophy (Lowe Syndrome) Wilson Disease
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