Obstructed Megaureter Workup
- Author: Robert A Mevorach, MD; Chief Editor: Edward David Kim, MD, FACS more...
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- Sequential Multiple Analysis–6 different serum tests
- Sequential Multiple Analysis–6 different serum tests (SMA-6) includes measurement of creatinine and BUN to assess gross renal function.
- Levels of sodium, potassium, chloride, or bicarbonate may show subtle changes in some patients with bilaterality or associated dysplasia.
- In neonates, wait 3-5 days to evaluate the baby’s kidney function rather than the mother's kidney function.
- A creatinine level of 1 mg/dL or greater at age 1 year is prognostic for subsequent renal failure.
- A serum calcium assessment for associated ureteral calculi is an essential screening test for hyperparathyroidism.
- Urinalysis is recommended upon evidence of infection, proteinuria, high pH level, and low specific gravity that may reflect underlying infection or renal dysplasia or damage.
- Screen for UTI.
- Assess urine concentration and acidification in bilateral lesions and dysplasia.
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- Renal or bladder ultrasonography
- Prenatal imaging reveals both hydroureter and hydronephrosis. Repeat ultrasonography for hydronephrosis within the first few days of life in patients with solitary kidney or bilateral lesions. Hydroureter and unilateral lesions may be evaluated electively within the first 2 months of life.This renal sonogram demonstrates hydronephrosis with good parenchymal thickness and retained corticomedullary differentiation.
- Postnatal imaging is used to define the degree of hydronephrosis based on the following Society of Fetal Urology guidelines:
- Grade I - Splitting of the renal sinus more than 10 mm
- Grade II - Splitting of the renal sinus more than 10 mm in an extrarenal or intrarenal pelvis not extending to the calyces
- Grade III - Dilatation extending into the calyces without cortical thinning
- Grade IV - Dilatation extending into the calyces with cortical thinning
- Postnatal imaging further defines the following anatomy:
- Extent of hydroureter, presence of collecting system duplication
- Presence or absence of ureterocele
- Bladder configuration, size, and thickening
- Postnatal imaging further provides clinically relevant data, including the following:
- Presence or absence of calculi
- Echogenic debris suggesting infection
- Indirect evidence of degree of obstruction by presence of a ureteral jet
- Location and condition of remaining renal units
- Prenatal imaging reveals both hydroureter and hydronephrosis. Repeat ultrasonography for hydronephrosis within the first few days of life in patients with solitary kidney or bilateral lesions. Hydroureter and unilateral lesions may be evaluated electively within the first 2 months of life.
- Voiding cystourethrography (VCUG): This is performed to assess for the presence of vesicoureteral reflux and to further delineate the anatomy of the bladder and outlet. In boys with bilateral megaureter, posterior urethral valves must be excluded.
- Radionuclide renal scanning
- After ultrasonography and VCUG are performed, the diagnosis of primary megaureter may be secure; the only remaining clinical issue is evaluating for obstruction. In these cases, technetium Tc 99m diethylenetriamine pentaacetic acid (DTPA) or technetium Tc 99m mercaptotriglycylglycine (MAG-3) renal scanning may be used to assess renal blood flow, relative function, and drainage. It is also helpful in predicting the capacity for functional recovery prior to surgery.
- Increasing ureteral dilation warrants consideration of renal and ureteral drainage. Although kidney drainage may be normal, it may be the result of urine pooling in the abnormally dilated ureter, resulting in ureteral obstruction.
- Exact definitions of obstruction do not exist. Serial examinations to demonstrate a trend toward decreasing function or delayed drainage are often required to establish an accurate treatment approach. In addition, renal resistive index can be used to help identify true obstruction as long as renal function is good.This panel from a technetium Tc 99m mercaptotriglycylglycine (MAG-3) renal scan shows differential obstruction of each kidney. While the classic image of a primary obstructed megaureter is shown on the left, a severe congenital ureteropelvic junction obstruction is present in the contralateral kidney. (These images are viewed with the left kidney on the left portion of each panel and the right kidney on the right portion of each panel.)
- Intravenous urography: In cases in which anatomic definition is desired, intravenous urography (IVU) can be used if renal function is good and the degree of obstruction to the affected renal unit is mild.
- Magnetic resonance imaging: In centers that have the technology, MRI can be used to reconstruct a 3-dimensional depiction of the urinary collecting system. The requirement for special software to assess renal function accurately and the need for restraint, sedation, or general anesthesia limit its application in neonates and infants.
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- Antegrade pyelography
- Antegrade injection of contrast directly into the renal pelvis via percutaneous access is used as an adjunct to placement of a nephrostomy tube to drain an infected system or to define an equivocal obstruction (Whitaker test) by infusion of contrast medium at a fixed rate with concurrent pressure measurements in the kidney and bladder. Infusion rates for adults generally have been 10 mL per minute, and a pressure differential between kidney and bladder of less than 15 cm H2 O is accepted as normal. This study is often used to provide additional evidence of obstruction to support surgical intervention. This technique also helps to delineate anatomy when diagnostic questions persist after less-invasive testing, often in the same setting as planned surgical repair.
- As is evident from the 600-mL/h rate of urine flow that is used in the Whitaker test, the physiologic implications of all except negative test results are debatable. In the author's experience, this test is too dependent on variations in anatomy (renal collecting system compliance) and technique to provide any real benefit over a gestalt from antegrade pyelography alone.
- Retrograde pyelography: Placement of a catheter into the ureteral meatus via endoscopy with injection of contrast medium under real-time fluoroscopy is reserved for diagnostic dilemmas and as an adjunct to surgery.
Surgical pathology reveals 5 histologic types: (1) abnormal circular orientation of muscle fibers with hypertrophy and hyperplasia, (2) mural fibrosis with little normal muscle within the ureteral wall, (3) hypoplasia and atrophy of all ureteral musculature, (4) absent longitudinal musculature, and (5) normal ureteral anatomy.
Hendren WH, Henderson BM. Recent advances in pediatric surgery. Am J Surg. 1969 Sep. 118(3):338-55. [Medline].
Creevy CD. The atonic distal ureteral segment (ureteral achalasia). J Urol. 1967 Mar. 97(3):457-63. [Medline].
Williams DI, Hulme-Moir I. Primary obstructive mega-ureter. Br J Urol. 1970 Apr. 42(2):140-9. [Medline].
Mortell A, Fourcade L, Solari V, Puri P. Bilateral megaureters in the Adriamycin rat model. Pediatr Surg Int. 2005 Mar. 21(3):212-6. [Medline].
Kajbafzadeh AM, Payabvash S, Salmasi AH, Arshadi H, Hashemi SM, Arabian S, et al. Endoureterotomy for treatment of primary obstructive megaureter in children. J Endourol. 2007 Jul. 21(7):743-9. [Medline].
Tatlisen A, Ekmekçioglu O. Direct nipple ureteroneocystostomy in adults with primary obstructed megaureter. J Urol. 2005 Mar. 173(3):877-80. [Medline].
Arena F, Baldari S, Proietto F, Centorrino A, Scalfari G, Romeo G. Conservative treatment in primary neonatal megaureter. Eur J Pediatr Surg. 1998 Dec. 8(6):347-51. [Medline].
Bakker HH, Scholtmeijer RJ, Klopper PJ. Comparison of 2 different tapering techniques in megaureters. J Urol. 1988 Nov. 140(5 Pt 2):1237-9. [Medline].
Bapat S, Bapat M, Kirpekar D. Endoureterotomy for congenital primary obstructive megaureter: preliminary report. J Endourol. 2000 Apr. 14(3):263-7. [Medline].
Belman AB. Megaureter. Classification, etiology, and management. Urol Clin North Am. 1974 Oct. 1(3):497-513. [Medline].
DeFoor W, Minevich E, Reddy P, Polsky E, McGregor A, Wacksman J, et al. Results of tapered ureteral reimplantation for primary megaureter: extravesical versus intravesical approach. J Urol. 2004 Oct. 172(4 Pt 2):1640-3; discussion 1643. [Medline].
Erbas B, Royal SA, Joseph D. Scintigraphic evaluation of obstructing primary megaureter with Tc-99m MAG3. Clin Nucl Med. 1997 Jun. 22(6):355-8. [Medline].
Lee SD, Akbal C, Kaefer M. Refluxing ureteral reimplant as temporary treatment of obstructive megaureter in neonate and infant. J Urol. 2005 Apr. 173(4):1357-60; discussion 1360. [Medline].
Lockhart JL, Politano VA. Management of massively dilated ureters in children. Urology. 1981 Sep. 18(3):229-34. [Medline].
McLaughlin AP 3rd, Pfister RC, Leadbetter WF, Salzstein SL, Kessler WO. The pathophysiology of primary megaloureter. J Urol. 1973 May. 109(5):805-11. [Medline].
Patti G, Menghini ML, Todini AR, Marrocco G, Calisti A. The role of the renal resistive index ratio in diagnosing obstruction and in the follow-up of children with unilateral hydronephrosis. BJU Int. 2000 Feb. 85(3):308-12. [Medline].
Payabvash S, Kajbafzadeh AM, Tavangar SM, Monajemzadeh M, Sadeghi Z. Myocyte apoptosis in primary obstructive megaureters: the role of decreased vascular and neural supply. J Urol. 2007 Jul. 178(1):259-64; discussion 264. [Medline].
Rabinowitz R, Barkin M, Schillinger JF, Jeffs RD. Surgical treatment of the massively dilated primary megaureter in children. Br J Urol. 1979 Feb. 51(1):19-23. [Medline].
Rabinowitz R, Barkin M, Schillinger JF, Jeffs RD, Cook GT. Surgical treatment of the massively dilated ureter in children. Part II. Management by primary reconstruction. J Urol. 1977 Sep. 118(3):436-9. [Medline].
Rabinowitz R, Barkin M, Schillinger JF, Jeffs RD, Cook GT. The influence of etiology on the surgical management and prognosis of the massively dilated ureter in children. J Urol. 1978 Jun. 119(6):808-13. [Medline].
Shukla AR, Cooper J, Patel RP, Carr MC, Canning DA, Zderic SA, et al. Prenatally detected primary megaureter: a role for extended followup. J Urol. 2005 Apr. 173(4):1353-6. [Medline].
Stehr M, Metzger R, Schuster T, Porn U, Dietz HG. Management of the primary obstructed megaureter (POM) and indication for operative treatment. Eur J Pediatr Surg. 2002 Feb. 12(1):32-7. [Medline].
Tanagho EA. Embryologic basis for lower ureteral anomalies: a hypothesis. Urology. 1976 May. 7(5):451-64. [Medline].
Thompson A, Gough DC. The use of renal scintigraphy in assessing the potential for recovery in the obstructed renal tract in children. BJU Int. 2001 Jun. 87(9):853-6. [Medline].