Urological Health Bladder Health An Overview of Hydronephrosis An abnormal retention of urine can lead to kidney swelling and damage By Jenny Lelwica Buttaccio, OTR/L Jenny Lelwica Buttaccio, OTR/L LinkedIn Twitter Jenny Lelwica Buttaccio, OTR/L, is a licensed occupational therapist and advocate for patients with Lyme disease. Learn about our editorial process Updated on June 23, 2020 Medically reviewed Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. These medical reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Matthew Wosnitzer, MD Medically reviewed by Matthew Wosnitzer, MD LinkedIn Twitter Matthew Wosnitzer, MD, is board-certified in urology. He is an attending physician at Yale New Haven Health System, Northeast Medical Group and teaches at the Frank Netter School of Medicine. Learn about our Medical Expert Board Print Table of Contents View All Table of Contents Overview Symptoms Causes Diagnosis Treatment Prevention Hydronephrosis, or swollen kidney, occurs when urine backs up into one or both of the kidneys. Usually, urine flows from the kidneys to the bladder. When a blockage or obstruction impedes the normal flow of urine, hydronephrosis can develop. Getty Images / Peter Dazeley Overview The urinary tract serves two distinct purposes. The primary function of the kidneys is to filter out extra water, salt, and waste. The second is to collect and excrete urine from the body. If the system becomes blocked, urine can accumulate, causing the kidneys to swell. This is hydronephrosis. When this impacts one kidney, it is called unilateral hydronephrosis; when both are affected, it’s called bilateral hydronephrosis. In most cases, only one kidney will be affected. Initially, a person with hydronephrosis may not experience any noticeable signs of dysfunction. But, over time, symptoms may appear as the swelling persists, causing notable discomfort. The extent of the symptoms depends on the reason for the blockage and its severity. If not treated in a timely and appropriate manner, hydronephrosis can damage one or both kidneys and contribute to the development of acute kidney failure. Symptoms A person with hydronephrosis may not be aware they have the condition. When symptoms are present, they may show up within a range of hours, weeks, or months. Symptoms can include: Flank pain Pain during urination Blood in the urine Fever Fatigue Malaise Nausea Vomiting Urinary tract infection (UTI) A persistent urge to urinate Changes in urinary frequency Inability to void the bladder completely Weak urine stream Incontinence Failure to thrive in infants In extreme cases, the kidney swelling may be detectable by appearance or palpation (touch). Causes Hydronephrosis can affect people of all ages, from before birth to adulthood. If hydronephrosis happens before birth, it is referred to as antenatal hydronephrosis or fetal hydronephrosis. Common risk factors for hydronephrosis include renal calculi (kidney stones that cause blockage when they move adjacent to or into the drainage tube of the kidney, called the ureter), enlarged prostate, pelvic masses or tumors (such as ovarian cysts, cervical cancer, or prostate cancer), and neurogenic bladder (the neurological loss of bladder control). Hydronephrosis can also occur during pregnancy as the developing fetus presses against the urinary tract. Among infants and children, boys are twice as likely to experience hydronephrosis as girls. However, the condition does not appear to be inherently linked to genetics or family history. Diagnosis To diagnose hydronephrosis, you may be referred to a urologist for a series of tests and examinations. The most standard include the following. Physical exam: The healthcare provider will take a detailed account of your symptoms and medical history and examine the kidney area. This will include a visual and manual exam to detect signs of kidney swelling or tenderness. Imaging studies: The healthcare provider may use ultrasound, X-rays, computed tomography (CT), or magnetic resonance imaging (MRI) to see if your kidney is swollen and where the obstruction is occurring. Contrast dyes are sometimes used to visualize blood vessels and soft tissue masses. Lab tests: Lab work may include a blood test to evaluate your kidney function (including urea and creatinine levels) and check if you could have an infection. You may also be asked to provide a specimen for a urinalysis to check for signs of an infection, blood, or kidney stones. To ensure the correct diagnosis, the healthcare provider may perform other tests to exclude causes that are similar to hydronephrosis. The differential diagnoses may include multicystic dysplastic kidney (a congenital malformation of the kidneys), ureteroceles (a birth defect of the ureters that connect the kidneys to the bladder), or vesicoureteric reflux (a condition where urine backflows from the bladder to the kidneys). Treatment Although the treatment for hydronephrosis varies depending on the reason for the condition, in some cases, the situation resolves without the need for medical intervention. In mild to moderate cases, your healthcare provider may choose to wait and see if the condition improves on its own. If your healthcare provider suspects a UTI or if you are at risk of developing one, they may prescribe you a course of antibiotics. If pain is an issue, you may also receive an over-the-counter or prescription nonsteroidal anti-inflammatory drug like ibuprofen or diclofenac. 1:29 Treating Kidney Stones In severe cases of hydronephrosis, surgery may be needed to remove obstructions or redirect the flow of urine. Hydronephrosis accompanied by a 5% to 10% loss of kidney function may warrant pyeloplasty (the surgical reconstruction of the kidney). Other indications for surgery include persistent kidney pain with obstructing ureteral stone, urine infection with ureteral stone, kidney dysfunction, or recurrent UTI with a high fever. Neurologic causes of hydronephrosis (such as a spinal cord injury that impairs bladder function) may require ongoing catheterization to help clear urine and anticholinergic drugs to increase bladder capacity. Severe hydronephrosis can cause permanent kidney damage, but, in most cases, only one kidney will be harmed. Fortunately, one kidney is usually capable of doing the work of two. Prevention When the cause of hydronephrosis is determined, there may be certain lifestyle modifications you can implement to lessen the chances of it happening again. For example, if you are prone to kidney stones, a specialized diet may help to avoid a recurrence of them. As another example, if hydronephrosis is caused by urinary retention, muscle and nerve problems in the pelvis, or organ prolapse, pelvic floor therapy from a trained physical therapist or bladder catheterization can assist with retraining the bladder to work in a more normal way. A Word From Verywell Any medical diagnosis can be scary, but thankfully the prognosis for hydronephrosis is good when you seek appropriate medical treatment. If you develop a fever; sudden pain in the abdomen, side, or back; or any other symptoms of hydronephrosis, don’t wait to get the care you need—see your healthcare provider as soon as possible. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 7 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Nuraj P, Hyseni N. The diagnosis of obstructive hydronephrosis with color doppler ultrasound. Acta Inform Med. 2017;25(3):178-81. doi:10.5455/aim.2017.25.178-181 Kazama I, Nakajima T. Postrenal acute kidney injury in a patient with unilateral ureteral obstruction caused by urolithiasis: a case report. Medicine (Baltimore). 2017;96(43):e8381. doi:10.1097/MD.0000000000008381 Sinha A, Bagga A, Krishna A, et al. 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