What is a Megaureter?

Most children are born with a normal urinary tract. But in some infants the tube that connects the kidney and bladder gets wider. This can cause infections and block urine flow. If not treated, this can cause serious kidney damage.

Female Urinary Tract
Female Urinary Tract
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Male Urinary Tract
Male Urinary Tract
Medical Illustration Copyright © 2015 Nucleus Medical Media, All rights reserved

What Happens under Normal Conditions?

The urinary tract is like a plumbing system, with special ‘pipes' that allow water and salts to flow through them. The urinary tract is made up of 2 kidneys, 2 ureters, the bladder, and the urethra.

The kidneys act as a filter system for the blood. They remove toxins and keep the useful sugar, salts, and minerals. Urine, the waste product, is made in the kidneys and flows down 2, 10 to 12-inch-long tubes called ureters into the bladder. The ureters are about a quarter inch wide and have muscled walls which push the urine into the bladder. The bladder stretches or expands to store the urine until you're ready to drain it by peeing. It also closes the pathways into the ureters so urine can't flow back into the kidneys. The tube that carries the urine from the bladder out of the body is called the urethra.

What are Megaureters?

A megaureter ("large ureter") is when a ureter is wider than three-eighths of an inch. This can result from an abnormality of the ureter itself (primary) or from the bladder being blocked (secondary). The different types of megaureters are described below.

Primary Obstructed Megaureter

This type is when the ureter is too thin where it enters the bladder. This block causes the ureter to get wider further up. The narrowing can damage the kidney over time. Surgery may be needed to fix the problem and remove the block. It's important to follow up with your health care provider even if the symptoms improve.

Refluxing Megaureters

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In this type, the ureters are wider because of urine flowing back up the ureters from the bladder ("vesicoureteral reflux" ). Normally, once urine is in the bladder, it shouldn't go back up the ureters. A refluxing megaureter is a sign of vesicoureteral reflux. This is more common in newborn males. Sometimes the reflux and stretched ureters gets better over the first year of life. But if the problem doesn't go away, surgery may be needed. Refluxing megaureters may be linked to a health issue where the bladder doesn't drain all the way. Instead, it sends urine back up the ureters, and the bladder swells. This condition is called "megacystis megaureter syndrome."

Non-Obstructive, Non-Refluxing Megaureters

These are wide ureters that aren't caused by blocks or urine backflow. Many of these get better with time. Your health care provider will check carefully to rule out a block or reflux.

Obstructed, Refluxing Megaureters

This type is caused by a ureter that's blocked and also suffers from reflux. This is dangerous, as the ureters get bigger and more blocked with time. People with this problem are more likely to get urinary tract infections.

Secondary Megaureters

These are megaureters that show up as a result of other health problems. Some of these health problems that cause megaureters are:

  • posterior urethral valves (a block in the male urethra)
  • prune belly syndrome
  • neurogenic bladder (spina bifida, spinal cord injury, etc.)