What Is Hydronephrosis?

  • Hadiza BelloDoctor of Medicine - MD, All Saints University, Saint Vincent, UK
  • Shivani GulatiMS Pharm, Medicinal Chemistry, National Institute of Pharmaceutical Education and Research, Hyderabad

Hydronephrosis is the distention of parts of the kidneys that form a pathway for urine. These include the renal calyces and pelvis. This distension is caused by the backflow of urine due to an obstruction in urine outflow downstream from the kidneys. 


Hydronephrosis can occur for several reasons, affect different populations and can happen in a short period of time or develop over an extended period. It is also possible for it to affect only one kidney (unilateral hydronephrosis) or both kidneys (bilateral hydronephrosis). The main cause of hydronephrosis is urine backflow, which can occur as a result of certain conditions, which we will discuss below.

Causes of hydronephrosis

Kidney stones - Kidney stones are concentrations of minerals and salts in your urine that may condense together and form stones which get stuck in the pathway of urine exit, thus preventing urine from exiting the body, creating backflow and, ultimately, hydronephrosis

Birth defects are abnormalities that occur during the development of a foetus before birth. Antenatal hydronephrosis is a type of hydronephrosis that is present before birth and may persist after. It is often a result of a birth defect in the urinary tract of a developing foetus, which involves narrowing of passages where urine flows through or abnormalities of the valves; vesicoureteral valve reflux is an abnormality of the urethral valve that controls the flow of urine between the bladder and the ureters that allows urine to flow back up to the kidneys

Benign prostatic hyperplasia - This is a non-cancerous enlargement of the prostate gland that happens with advancing age. Because this gland surrounds the urethra, it gradually compresses the urethra as it enlarges and restricts the passage of urine out of the bladder

Neurogenic bladder - It is a cause of bladder dysfunction caused by injury to the spinal cord or the nerves that supply the bladder and help control the voiding of urine. Neurogenic bladder is also possible in people with diabetic neuropathy1

Urinary tract obstruction - the urethra is a relatively narrow tube, which makes it easily obstructed by scarring, tumours, blood clots, or strictures

Pregnancy -  During pregnancy, the growing foetus compresses the bladder, resulting in temporary obstruction of the urinary tract and causing mild hydronephrosis, which resolves soon after birth

Signs and symptoms of hydronephrosis

While it can exist without any symptoms, the symptoms of hydronephrosis that may present depend on the duration of its existence. If it develops rapidly over a short period of time, it is more likely to be symptomatic compared to a situation where it develops over time. Some commonly seen signs and symptoms are

  • Flank pain
  • Lower abdominal pain or pressure
  • Nausea and vomiting
  • Costovertebral angle tenderness
  • Urinary urgency

Management and treatment for hydronephrosis


  • Pain medication: Pain medications are needed to manage the pain associated with hydronephrosis
  • Antibiotics: Depending on the cause of hydronephrosis, antibiotics could be used to treat urinary tract infections that have resulted in hydronephrosis 
  • Other Medications: Medications that help reduce the amount of uric acid in the blood could help prevent the condition by preventing the formation of kidney stones in people who are prone to them


  • Urethral catheterisation is often indicated in the first instance for the treatment of hydronephrosis. The procedure involves inserting a sterile tube into the bladder through the urethra to drain urine. This can help relieve the pressure caused by the backflow of urine. Surgery is indicated for more severe cases.
  • Surgery to repair any existing defects in the urinary tract may be done in some cases.


Urine tests: Urine tests are used to check for blood and certain substances that suggest a urinary tract infection or the presence of a kidney stone in the urethra 

Ultrasound: Often the first imaging test carried out for suspected hydronephrosis, ultrasonography is relatively cheaper than other imaging tests and is non-invasive. It is able to detect any abnormalities of the kidneys and if there are any obstructions in the urinary tract. Severe hydronephrosis

CT scan: Computed tomography scans create more detailed images of the body than ultrasounds and are useful for detecting smaller abnormalities or obstructions

Kidney function tests: These are blood tests that detect substances like urea, creatinine, and potassium in the blood. These are typically expelled from the body by the kidneys. If these substances are over the normal level they should be in the blood, it indicates an impairment in the function of the kidneys 


How can I prevent hydronephrosis?

Lifestyle: Regular exercise and a healthy balanced diet promote a healthy weight and kidney health. Adopting a healthy lifestyle also prevents and helps manage conditions that may lead to hydronephrosis

Proper management of underlying disorders: people who suffer from conditions that increase the risk of hydronephrosis, such as diabetes, benign prostatic hyperplasia, strokes, or kidney stones, should get regular follow-ups with their healthcare provider. Ensuring good compliance with medications, lifestyle modifications, or interventions needed to manage the condition

Hydration: Drinking adequate amounts of water to maintain proper hydration can help prevent the formation of kidney stones

How common is hydronephrosis?

Hydronephrosis is relatively common in pregnancy, is a common condition and is seen in up to 80% of pregnancies.2 Although it is not very common in healthy adults, its incidence increases with certain conditions that are related to age and lifestyle. Conditions like diabetes, BPH, and hypertension are more common in the older population. 

Who is at risk of hydronephrosis?

  • People who have had strokes 
  • People with spinal cord injuries
  • People with benign prostatic hyperplasia
  • Babies in utero

When should I see a doctor?

You should see a doctor if you have symptoms of a urinary tract infection, trouble passing urine, or a condition that puts you at risk of hydronephrosis. People with conditions that can lead to hydronephrosis should get regular checks with their healthcare provider. It is important to get a timely diagnosis and treatment, as severe hydronephrosis could result in permanent kidney damage if not caught in time.


Hydronephrosis is a condition that results from the backflow of urine from the bladder back to the kidneys, causing compression of the renal calyces. It has no long-term effects if treated on time. However, it might lead to damage to the affected kidney if it exists for an extended period of time. Obstruction of urine outflow that occurs along the ureters, chronic UTIs, and conditions that affect the nerves supplying the bladder leads to hydronephrosis. The main symptom of this condition is flank pain. Diagnosis consists of imaging, urine, and blood tests. Treatment focuses on removing the cause of the obstruction to stop the backflow of urine. By recognizing the underlying causes, individuals can take appropriate measures to prevent hydronephrosis or seek timely medical intervention. Additionally, adopting a healthy lifestyle and staying hydrated are important preventive strategies. Early diagnosis, proper treatment, and adherence to medical advice can significantly improve outcomes for individuals with hydronephrosis


  1. Spring M, Hymes J. Neurogenic bladder dysfunction as a complication of diabetes: report of seven cases. Diabetes [Internet]. 1953 May 1 [cited 2023 Jun 16];2(3):199–205. Available from: https://diabetesjournals.org/diabetes/article/2/3/199/5685/Neurogenic-Bladder-Dysfunction-as-a-Complication
  2. Thotakura R, Anjum F. Hydronephrosis and hydroureter. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Jun 16]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK563217/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Hadiza Bello

Doctor of Medicine - MD, All Saints University, Saint Vincent

Hadiza is a Medical Doctor who has worked in a clinical setting for five years, gaining valuable experience in diagnosing and treating a wide range of conditions.
She is currently pursuing an MSc in Infectious Diseases at the University of Kent
She is constantly exploring options to get involved in global health initiatives and is passionate about making healthcare more accessible and equitable for all.

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