You are in: eMedicine Specialties > Radiology > GENITOURINARY Reflux NephropathyArticle Last Updated: Aug 23, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: George Gross, MD, Chief of Pediatric Radiology, University of Maryland Medical Center; Professor, Department of Diagnostic Radiology, University of Maryland School of Medicine George Gross is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Medical Association, Association of University Radiologists, Radiological Society of North America, Society for Pediatric Radiology, and Society of Thoracic Radiology Editors: Steven Perlmutter, MD, FACR, Clinical Associate Professor, Radiology Residency Program Director, Radiology Medical Director, Department of Radiology, University Hospital at Stony Brook; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Joshua A Becker, MD, Professor, Department of Radiology, New York University School of Medicine; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: chronic pyelonephritis, renal scarring, renal parenchymal scarring, vesicoureteral reflux, VUR, urinary tract infections, UTIs, intrarenal reflux INTRODUCTIONSection 2 of 11
  BackgroundHodson initially noted the association of vesicoureteral reflux (VUR) with renal parenchymal scarring. PathophysiologyReflux nephropathy is based on persistent reflux of sterile or infected urine from the bladder to one or both kidneys via the ureters. Although sterile VUR may cause renal scarring, most studies indicate that the appearance of renal scarring or the extension of established renal scars requires infection (Escherichia coli is the common pathogen). The higher the grade of reflux, the greater the likelihood of development of new or progressive scarring in association with infection. Intrarenal reflux, or the extension of VUR into the collecting tubules of the nephrons that allows urinary microorganisms access to the renal parenchyma, is believed to be particularly important in the development of renal scarring. Radiologic evidence of renal scarring is noted in 30-60% of children with VUR, and VUR is present in almost all children with severe renal scarring. A direct correlation between the prevalence of scarring and the grade of VUR has been demonstrated. Although VUR occurs at a similar rate in boys and girls, girls are at greater risk of developing reflux nephropathy because of increased incidence of urinary tract infection (UTI). In the absence of reflux and UTI, abnormalities of organ systems other than the genitourinary tract do not place a child at increased risk for developing reflux nephropathy. FrequencyUnited StatesThe incidence of renal scarring in children resulting from VUR is unknown. The prevalence of VUR in asymptomatic children is less than 0.5%, but VUR is present in 29-50% of children with UTIs. Mortality/MorbidityThe incidence of renal scarring in children caused by VUR is unknown. VUR is present in 29-50% of children with UTIs. RaceVUR and reflux nephropathy occur less frequently in black children than in other groups of patients. SexReflux occurs at a similar rate in boys and girls; however, the much higher incidence of UTI in girls places them at greater risk for reflux nephropathy. AgeIn children, the occurrence of VUR decreases with increasing age. The vesicoureteral insertion matures just prior to puberty. The mature bladder wall intramural portion of the ureter attains its 1.5-cm length. AnatomyMost cases of VUR are considered primary because of incompetence of the ureterovesical junction (UVJ), and it is not secondary to either obstruction or infection. As the UVJ matures to assume its adult 1.5-cm oblique path through the bladder wall, VUR tends to decrease in severity and eventually disappears just before puberty. An exception is in patients with an anatomic abnormality such as a bladder diverticulum, into which the refluxing ureter enters. Incompetence of the UVJ resulting from a lack of maturation is the most common cause of VUR in children. Obstruction and infection rarely cause reflux. With maturation of the incompetent UVJ, reflux usually eventually resolves. A small subgroup of children have a perpendicular ureteric insertion at the bladder wall, with a resultant golf-hole ureteric orifice. In these patients, surgical correction is necessary to eliminate VUR. A decision to perform a repair, either a ureteroneocystostomy or a collagen periurethral injection, is dependent on the appearance of the ureteric orifice. Nevertheless, all patient are covered with appropriate antibiotics to await the maturation of the intramural portion of the ureter or undergo surgery to stop the reflux. Clinical DetailsChildren with reflux nephropathy may be asymptomatic, may present with nonspecific symptoms (eg, failure to thrive, fever, poor food intake), may be acutely ill in association with acute pyelonephritis, or may present with renal failure with advanced renal scarring associated with reflux nephropathy. Vesicoureteral reflux is graded on a scale of 0-5. Grade 0 indicates no reflux; grade 1 indicates reflux into the ureter but not reaching the renal pelvis; grade 2 indicates reflux into the renal pelvis and calyces but without any dilatation; and grades 3, 4, and 5 indicate reflux to the renal pelvis and calyces with mild, moderate, and severe dilatation, respectively. Preferred ExaminationRenal ultrasonography (RUS) and voiding cystourethrography (VCUG) are the preferred radiologic methods. The 2 procedures provide complementary information. RUS helps in evaluating the upper urinary tract (kidneys and proximal portion of the collecting system) for anomalies, masses, calcification, hydronephrosis, and size and can identify renal scarring if moderate to severe in degree. VCUG helps in evaluating for VUR and the anatomy of the lower urinary tract (bladder and urethra). Limitations of TechniquesRenal scarring is detected and identified better by using nuclear medicine renal scanning with a cortical imaging agent (eg, technetium-99m dimercaptosuccinic acid) than with ultrasonography. Imaging with renal scanning may require sedation in younger children. Sedation is increasingly requested, although rarely necessary, for children undergoing VCUG. RADIOGRAPHSection 3 of 11
FindingsPlain images offer no diagnostic information regarding VUR and reflux nephropathy, although they can be used to evaluate spinal anomalies and potential urinary tract calculi, which rarely occur in this population. VCUG is essential in evaluating lower urinary tract anatomy and in identifying or excluding VUR.
Degree of ConfidenceWith VCUG, the degree of confidence is high for detecting VUR and low for detecting chronic pyelonephritic scarring. With IVU, the degree of confidence is moderate for detecting chronic pyelonephritic scarring. False Positives/NegativesFalse findings occur infrequently; however, the soft tissue of the bowel wall can simulate contrast enhancement in a ureter, and overlying stool and intestinal gas can sufficiently obscure the kidney to prevent identification of lesser degrees of VUR. Scarring from reflux nephropathy can usually be differentiated from scarring from other etiologies (such as parenchymal infarction) by the fact the calyx underlying the scar will be deformed in reflux nephropathy. CT SCANSection 4 of 11
FindingsCT scanning is not indicated in the evaluation of reflux nephropathy because of radiation dose, the need for intravenously administered contrast material, and the potential need for patient sedation. However, CT scans can demonstrate renal scarring and hydronephrosis but not VUR. MRISection 5 of 11
FindingsMRI is not routinely indicated in the evaluation of reflux nephropathy because of cost of the procedure and the potential need for patient sedation. However, MRI can demonstrate renal scarring and hydronephrosis but not VUR. ULTRASOUNDSection 6 of 11
FindingsAlteration of renal contour and reduced thickness to the renal parenchyma are the primary findings of reflux nephropathy. Ultrasonography is excellent for demonstrating upper urinary tract dilatation. Echo-enhanced cystosonography performed by using ultrasonographic contrast media is a new diagnostic procedure with a major attribute in the exclusion of ionizing radiation. Degree of ConfidenceWith ultrasonography, the degree of confidence is moderate in the detection of reflux nephropathy. Lesser degrees of renal scarring may not be evident with ultrasonography. Echo-enhanced cystosonography, in limited experience, is reported to be as accurate as radiographic VCU in the identification of reflux. False Positives/NegativesFetal lobation and other normal variants of renal development may be mistaken for renal scarring on sonograms. NUCLEAR MEDICINESection 7 of 11
FindingsTechnetium-99m dimercaptosuccinic acid and technetium-99m glucoheptonate are scintigraphic agents with a high affinity for the renal cortex because they are concentrated by renal tubular cells. As a result, they produce a relatively high level of renal detail. Concern for acute pyelonephritis, the assessment of renal cortical scarring, and the identification of a malpositioned kidney are among the indications for cortical scintigraphy. The use of single-photon emission computed tomography increases sensitivity of the agents to changes of renal scarring and acute pyelonephritis. Reduced accumulation of a cortical imaging isotope within the renal margins is an indication of renal scarring. Radionuclide cystogram provides an alternative to VCUG in identifying renal scarring. Cystograms have the primary disadvantage of poor anatomic resolution but the advantage of a lower radiation dose. Degree of ConfidenceDegree of confidence is high, with renal cortical imaging performed by using technetium-99m dimercaptosuccinic acid. False Positives/NegativesPatient motion, structural abnormalities of the kidneys, and unsatisfactory isotope administration may result in false-positive and false-negative findings. Patient motion results in inaccurate imaging depiction of isotope distribution and greater probability of underestimating renal scarring (false-negative findings). Hydronephrosis, anomalies such as ectopic and/or fused kidneys, and renal masses or cysts may result in the overestimation of severity of renal scarring (false-positive findings). ANGIOGRAPHYSection 8 of 11
FindingsAngiography does not play a role in the evaluation of reflux nephropathy. INTERVENTIONSection 9 of 11
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REFERENCESSection 11 of 11
Article Last Updated: Aug 23, 2007 | ||||||||||||||||||||||||||||||||||||||||
