90 - Megaureter: Analysis of Genesis and Prevalence of a Human Congenital Anomaly

Poster Board Number: 90
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Odd poster #s – first hour
Even poster #s – second hour

Abstract Body : Introduction and Objective: The prevalence of “Megaureter” or large ureter among children can be as high as 20-25%, it can be bilateral or unilateral, and in some cases the contralateral kidney either absent or dysplastic. While its hereditary nature is unclear it is seen in families. Embryologically, the permanent kidneys develop from the ureteric bud and the metanephric blastema. The ureteric bud is an outgrowth from the mesonephric duct and the stalk of the bud becomes the ureter. The ureters undergoes changes in their matrix components that includes collagen type and longitudinal and smooth muscle content. The megaureter is most often diagnosed in children as young as several months. It is also recognized as an incidental finding when other causes are investigated. Megaureter is more common in males and more often is on the left side. Megaureters can be categorized as obstructed, refluxing, obstructed and refluxing, or neither obstructed nor refluxing. Our objective is to elucidate and present the various causes of megaureter.
Materials and Methods: During routine student dissection of an 86-year-old female donor who died of atherosclerotic cardiovascular disease we observed the presence of large ureters on both kidneys with the right-side ureter being much larger than the left side. The upper and lower lobes of the right kidney were drained by independent ureters which were encased in a thin membranous connective tissue sheath. These two ureters joined forming a single ureter close to bladder entrance . The calyces of the upper and lower lobes of the right kidney were wide, and also showed diminished thickness of the renal medulla and cortex. Additionally, the uterus, fallopian tubes, ovaries, cervix and vagina were normal in size. The poster, in addition to providing a description of what was observed will discuss various causes, pathophysiology and alterations in the matrix composition of megaureter.
Results: Detailed measurements using an electronic caliper of the specimen showed the following: kidney length of 139.9mm right and 122.2mm left; width of 51.3mm and 55. 4mm left; thickness of 44.8mm right and 60.6mm left. Ureter length right kidney upper lobe 18.3cm, lower lobe 16.5cm before uniting and 7.5cm after uniting. Ureter length left kidney 24.2cm. Ureter lumen right kidney upper lobe proximal segment 24.7mm, 31.6mm middle segment and 11.9 mm distal segments(before uniting) and after uniting 14.6mm. Left ureter lumen 20.1mm proximal segment and 15.1mm distal segment. Cortex thickness at the hilum was 8.3mm and 19.4mm right and left respectively. Bladder wall thickness was 1.4-1.7mm.
Conclusion: In this donor the ureter lengths are normal for an adult female; however, the ureter lumens are very large especially of the right kidney. Normal lumen of an adult ureter is 3-5.1mm.
Significance/Implication One of many theories of megaureter includes a distal ‘aganglionic’ segment causing ‘aperistaltalsis’ of the ureter akin to megacolon. Early recognition of megaureter and its cause will enhance proper treatment options (slicing and by passing aganglionic part) and improve survival. Another possibility includes defective/lack of longitudinal muscle at the distal ureter.