Overview By Mayo Clinic Staff Print Hydronephrosis is swelling of one or both kidneys. It happens when urine can't drain from a kidney and builds up in the kidney as a result. The condition can be due to a blockage in the tubes that drain urine from the kidneys. It also can happen due to a difference present at birth that prevents urine from draining properly. In some people, hydronephrosis causes kidney damage over time. Hydronephrosis can happen at any age. The condition often causes no symptoms. People who get symptoms may have side and back pain, painful urination, vomiting and fever. Healthcare professionals have various ways to spot hydronephrosis. Tests to find the condition can be done during infancy or sometimes before a baby is born. Treatment for hydronephrosis depends on the condition's cause. Some people need medicine or surgery to feel better and prevent kidney damage. Mild hydronephrosis sometimes goes away on its own over time. Request an appointment Diagnosis & treatment Nov. 06, 2024 Print Share on: FacebookTwitter Show references AskMayoExpert. Hydronephrosis (nonstone related) (adult). Mayo Clinic; 2023. Hydronephrosis. National Kidney Foundation. https://www.kidney.org/atoz/content/hydronephrosis. Accessed June 10, 2024. Ferri FF. Hydronephrosis. In: Ferri's Clinical Advisor 2025. Elsevier; 2025. https://www.clinicalkey.com. Accessed June 10, 2024. Zeidel ML, et al. Clinical manifestations and diagnosis of urinary tract obstruction (UTO) and hydronephrosis. https://www.uptodate.com/contents/search. Accessed Nov. 12, 2019. Hydronephrosis. National Health Service. https://www.nhs.uk/conditions/hydronephrosis/. Accessed June 10, 2024. Related Hydronephrosis Products & Services A Book: Mayo Clinic Family Health Book HydronephrosisSymptoms&causesDiagnosis&treatmentDoctors&departments Advertisement Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. Advertising & Sponsorship Policy Opportunities Ad Choices Mayo Clinic Press Check out these best-sellers and special offers on books and newsletters from Mayo Clinic Press. NEW: Listen to Health Matters Podcast - Mayo Clinic PressNEW: Listen to Health Matters PodcastMayo Clinic on Incontinence - Mayo Clinic PressMayo Clinic on IncontinenceThe Essential Diabetes Book - Mayo Clinic PressThe Essential Diabetes BookMayo Clinic on Hearing and Balance - Mayo Clinic PressMayo Clinic on Hearing and BalanceFREE Mayo Clinic Diet Assessment - Mayo Clinic PressFREE Mayo Clinic Diet AssessmentMayo Clinic Health Letter - FREE book - Mayo Clinic PressMayo Clinic Health Letter - FREE book CON-20357565 Patient Care & Health Information Diseases & Conditions Hydronephrosis