Hydronephrosis
Hydronephrosis is a condition where one or both kidneys become swollen due to a buildup of urine. This usually happens when there’s a blockage or obstruction in the urinary tract that prevents urine from draining properly. Some people may experience pain, urinary changes, or recurrent infections, while others have no noticeable symptoms. Treatment depends on the cause and may involve procedures to relieve the blockage or manage underlying conditions.
Overview | Symptoms & Causes | Diagnosis | Treatment Options
The Urinary Tract
The kidneys are two bean-shaped organs that sit towards the back of the abdomen. Their main role is to filter waste and excess fluid from the blood, producing urine. They also help regulate blood pressure, maintain electrolyte balance, and support healthy red blood cell production. Once urine is produced, it flows through narrow tubes called ureters into the bladder, where it is stored until you urinate. Normally, this flow is unimpeded, allowing the kidneys to function efficiently.
Hydronephrosis occurs when urine cannot drain properly from the kidney into the bladder, causing the kidney to swell. This back pressure can stretch the kidney and, over time, affect its function. The degree of swelling can vary, and the condition may affect one kidney (unilateral) or both kidneys (bilateral), depending on the location and severity of the obstruction.
Understanding Hydronephrosis
Hydronephrosis can sometimes develop without noticeable symptoms, especially if it occurs gradually. When symptoms do appear, they can include:
- Pain in the side (flank) or lower back, often on one side if only one kidney is affected
- Abdominal discomfort or swelling
- Urinary changes, such as difficulty passing urine, decreased urine output, or frequent urination
- Nausea or vomiting, particularly if the swelling causes sudden obstruction
- In some cases, fever or signs of infection if a urinary tract infection develops alongside the obstruction
The severity and type of symptoms often depend on how quickly the obstruction develops and whether it affects one or both kidneys.
Causes & Risk Factors
Hydronephrosis occurs when urine cannot drain normally from the kidney to the bladder, causing the kidney to swell. This can happen for a variety of reasons:
| Kidney stones | These can block the flow of urine, leading to swelling. |
| Congenital abnormalities | Some people are born with structural differences in the urinary tract that make obstruction more likely. |
| Enlarged prostate | In men, an enlarged prostate can restrict urine flow and cause hydronephrosis. |
| Scar tissue or strictures | Narrowing of the ureter due to previous surgery, injury, or inflammation can block urine. |
| Tumours | Growths in or near the urinary tract can compress the ureters. |
| Pregnancy | The growing uterus can temporarily compress the ureters, causing mild hydronephrosis. |
Risk factors depend on the underlying cause and may include a history of kidney stones, urinary tract infections, or prior urinary tract surgery.
Diagnosing Hydronephrosis
Diagnosis usually starts with a clinical assessment if you have symptoms such as flank pain, urinary problems, or recurrent infections. Investigations are then used to confirm the presence of hydronephrosis, determine its severity, and identify the underlying cause.
| Urine & Blood Tests | These tests help assess overall kidney function and check for issues such as reduced filtration (eGFR) or possible infections. |
| Ultrasound | Often the first-line test, it can show swelling of the kidney, assess the degree of dilation, and sometimes suggest the cause, such as a kidney stone. |
| Additional Imaging | Provides more detail if the ultrasound is unclear or if a more complex cause is suspected, such as a tumour or structural abnormality. |
Treatment Options
Management depends on the severity of the swelling and the underlying cause. Mild cases may just need monitoring, while more significant obstruction or kidney function impairment requires treatment.
| Addressing the underlying cause | For example, removing a kidney stone, treating an infection, or correcting a structural problem in the urinary tract. |
| Monitoring | Mild or asymptomatic cases may be followed with repeat ultrasounds to ensure the kidney is not being damaged. |
| Medications | Antibiotics if there is an associated infection, or other drugs as required to manage symptoms or underlying conditions. |
| Surgery or procedures | In more severe cases, procedures may be needed to relieve obstruction, such as stent placement or surgical correction of anatomical abnormalities. |
The goal of management is to relieve obstruction, preserve kidney function, and prevent complications. Your clinician will tailor treatment based on your individual situation.
How can Lanthorn help?
Kidney Ultrasound - £300
A non-invasive first-line test to identify swelling, assess the degree of hydronephrosis, and check for potential causes such as stones or structural abnormalities.
Additional Imaging - From £450
Used when further detail is needed to understand the cause of obstruction, evaluate kidney function, or plan intervention.
Kidney & Liver Function Blood Test - £99
If there are concerns about kidney function, we can arrange blood tests (including eGFR and creatinine). These help assess how well the kidneys are working and whether any further steps are needed.
