What Should Be the Size of a Child's Kidney?
Determining kidney size for children is important in certain circumstances because enlarged kidneys can be evidence of obstruction along the ureters or urethral. Left untreated, some obstructions may lead to kidney failure. Kidney size is measured by ultrasound and is a routine part of a prenatal exam. Ultrasounds may be indicated in infants and children after urinary tract infections or the finding of an abdominal mass.
Assessing Kidneys
Your kidneys are located along the lower ribs and muscles of your back, just above the level of your belly button. The right kidney sits a little lower than the left because it is under your liver, the largest internal organ. Kidney size and other characteristics can be easily determined by ultrasound, as is done routinely during prenatal ultrasounds. After birth, routine blood and urine labs can add useful information about the kidneys' function.
- Your kidneys are located along the lower ribs and muscles of your back, just above the level of your belly button.
When to Assess Kidneys
Reasons for an Enlarged Kidney in Babies
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There are a couple of instances in which pediatricians might order an ultrasound of the kidneys 1. By far the most common is a urinary tract infection in girls up to age 6 or in boys of any age. Many pediatricians will forgive one urinary tract infection in older girls if they don't have a fever with it. The most urgent reason to get a kidney ultrasound is feeling a mass in your child's abdomen. Abdominal masses in children are almost always related to their urinary tract.
- There are a couple of instances in which pediatricians might order an ultrasound of the kidneys 1.
- By far the most common is a urinary tract infection in girls up to age 6 or in boys of any age.
Enlarged Kidneys
In infants and children, an enlarged kidney can be evidence of a blockage, either along the ureter from a kidney to the bladder, or along the urethra from the bladder to the outside world. A ureter obstruction affects the kidney on that side, while a urethral obstruction affects both kidneys. Obstructions are uncommon and most frequently caused by a ureter on one side not connecting to the bladder properly. If there's an obstruction, the urine that backs up will enlarge the kidney and cause abnormal pressure within it, eventually causing the kidney to fail. Finding an obstruction early can avoid such bad consequences, and treatment may require medication or surgery.
- In infants and children, an enlarged kidney can be evidence of a blockage, either along the ureter from a kidney to the bladder, or along the urethra from the bladder to the outside world.
Normal Kidney Size
What Are the Causes of Renal Pelvis Dilation?
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The kidneys of newborns are about 4.5 cm long, almost 2 inches, and weigh just less than an ounce. Kidneys of adults are about 12 cm long, nearly 5 inches, and weigh about 5 ozs. The growth of kidneys correlates more with a child's growth in height rather than age, and the normal length of the kidneys can be estimated using a simple mathematical formula based on your child's height. The kidneys grow rapidly in the first year of life, from 4.5 cm to 6.5 cm, and then gradually into adulthood, only about 0.3 cm, an eighth of an inch, per year on average.
- The kidneys of newborns are about 4.5 cm long, almost 2 inches, and weigh just less than an ounce.
- The kidneys grow rapidly in the first year of life, from 4.5 cm to 6.5 cm, and then gradually into adulthood, only about 0.3 cm, an eighth of an inch, per year on average.
Kidney Health
Kidneys are complex organs, not only filtering your bloodstream of wastes but also helping to regulate your blood pressure. They are such efficient filters that only one-fourth of one kidney is needed to properly filter the bloodstream, but they also need to last a lifetime. So keep your child well hydrated at all times, particularly during illnesses, and keep up with your child's regular health check-up appointments.
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References
- Nelson Textbook of Pediatrics 18th edition"; Robert M. Kliegman M.D., Richard E. Behrman M.D., Hal B. Jenson M.D., Bonita M.D. Stanton M.D.; 2007
- Riley Children's Health. (2020). Indian University Health. Ureterovesical junction obstruction.
- UCI Urology. Ureterovesical junction obstruction.
- Zaffanello M, Brugnara M, Cecchetto M, Manfredi R, Zuffante M, Fanos V. Paediatric unilateral giant hydroureteronephrosis from idiopathic ureterovesical stricture: a case report. BMJ Case Rep. 2009; 2009: bcr08.2008.0782. doi:10.1136/bcr.08.2008.0782
- Sfakianakis G N et al. A renal protocol for all ages and all indications: Mercapto-acetyl-triglycine (MAG3) with simultaneous injection of furosemide (MAG3-F0): A 17-year experience. Semin Nucl Med. 2009 May;39(3):156-73. doi:10.1053/j.semnuclmed.2008.11.001
- Children's Hospital of Philadelphia. Magnetic resonancy urography.
- Arrabal-Martín M, Zuluaga-Gómez A, Merino-Salas S, Nogueras-Ocaña M, Arrabal-Polo MA. Endoscopic treatment of ureterovesical junction obstructive pathology: A description of the oblique meatotomy technique and results. Can Urol Assoc J. 2013 Nov-Dec; 7(11-12): E728–E731. doi:10.5489/cuaj.496
- Boston Children's Hospital. Ureteral surgery.
- Children's Health. Pediatric robotic assisted laparoscopic ureteral reimplant.
Writer Bio
Dr. Robert Collins, a pediatrician since 1992, began writing in 2005. His work includes chemistry tutorials and a book on childhood discipline. He holds a Bachelor of Arts from the University of Virginia and a Doctor of Medicine from the Medical College of Virginia.