7 Key Symptoms of Hydronephrosis You Should Never Ignore

Hydronephrosis is a medical condition characterized by the swelling of one or both kidneys due to the buildup of urine. This occurs when urine cannot drain properly from the kidney to the bladder, causing the kidney to stretch and potentially leading to serious complications if left untreated. While hydronephrosis can affect people of all ages, recognizing its symptoms early is crucial for preventing permanent kidney damage.

Understanding the warning signs of hydronephrosis can help you seek timely medical attention and preserve your kidney function. The symptoms can vary from mild to severe depending on whether the condition develops suddenly (acute) or gradually over time (chronic). In this comprehensive guide, we’ll explore the seven key symptoms of hydronephrosis that you should be aware of.

1. Flank Pain or Discomfort

One of the most common and noticeable symptoms of hydronephrosis is pain in the flank area, which is the side of your body between your ribs and hip. This pain typically occurs on the side where the affected kidney is located.

The characteristics of flank pain in hydronephrosis include:

• Sharp or dull aching sensation: The pain can range from a constant dull ache to sudden, sharp stabbing sensations depending on how quickly the blockage develops
• Location-specific: Usually felt on one side of the back, just below the rib cage, though it can affect both sides if both kidneys are involved
• Intensity variations: May worsen after drinking large amounts of fluids as more urine accumulates in the already swollen kidney
• Radiating pain: Can extend from the back to the lower abdomen or groin area

In acute hydronephrosis, the pain tends to be more severe and sudden, while chronic cases may present with a milder, persistent discomfort that patients sometimes describe as a feeling of fullness or pressure in the kidney area.

2. Changes in Urination Frequency and Output

Hydronephrosis significantly affects your urinary patterns, often causing noticeable changes in how often you urinate and the amount of urine produced. These alterations occur because the normal flow of urine from the kidneys to the bladder is disrupted.

Common urinary changes include:

• Decreased urine output (oliguria): You may notice that you’re producing significantly less urine than normal, even when drinking adequate fluids
• Increased urge to urinate: Paradoxically, some patients experience frequent urges to urinate but produce only small amounts
• Difficulty starting urination: You may have trouble initiating the flow of urine or feel that your bladder isn’t emptying completely
• Complete absence of urine (anuria): In severe cases, particularly when both kidneys are affected, urine production may stop entirely, which is a medical emergency

If you notice persistent changes in your urination patterns, especially a significant decrease in urine output lasting more than a day, it’s essential to seek medical evaluation promptly.

3. Urinary Tract Infection Symptoms

Hydronephrosis creates an environment where bacteria can thrive, making urinary tract infections (UTIs) more common and recurrent. The stagnant urine in the swollen kidney serves as an ideal breeding ground for bacterial growth.

UTI symptoms associated with hydronephrosis may include:

• Burning sensation during urination: A painful, burning feeling when passing urine is one of the hallmark signs of infection
• Cloudy or foul-smelling urine: Your urine may appear turbid and have an unusually strong or unpleasant odor
• Fever and chills: When infection spreads to the kidney (pyelonephritis), you may develop a high fever, often accompanied by shaking chills
• Urgency and frequency: A persistent, urgent need to urinate, often with only small amounts of urine passed
• Lower abdominal pressure: A feeling of pressure or discomfort in the lower belly or pelvic region

Recurrent UTIs, especially when accompanied by back pain, should prompt investigation for underlying structural problems like hydronephrosis. Kidney infections in the presence of hydronephrosis can be particularly serious and require immediate medical attention.

4. Nausea and Vomiting

Gastrointestinal symptoms, particularly nausea and vomiting, are frequently observed in patients with hydronephrosis. These symptoms occur due to the complex relationship between kidney function and digestive system regulation.

Several factors contribute to these symptoms:

• Pain-related nausea: Severe flank or abdominal pain from kidney swelling can trigger nausea and vomiting reflexes
• Toxin accumulation: When kidney function is impaired, waste products that would normally be eliminated build up in the bloodstream, causing nausea
• Associated infection: If hydronephrosis is complicated by a kidney infection, systemic illness can cause significant digestive upset
• Uremia: In severe or prolonged cases, the accumulation of urea and other waste products in the blood can lead to persistent nausea and loss of appetite

These gastrointestinal symptoms are often more pronounced in acute hydronephrosis or when the condition is accompanied by complete or near-complete urinary obstruction. The combination of severe back pain, nausea, and vomiting should be evaluated urgently as it may indicate a serious blockage requiring immediate intervention.

5. Abdominal or Side Swelling

Visible or palpable swelling in the abdomen or flank area is a significant physical sign of hydronephrosis, particularly when the condition is severe or has been present for an extended period. This swelling results from the progressive enlargement of the affected kidney as urine accumulates.

Key characteristics of this symptom include:

• Detectable mass: In some cases, especially in thin individuals or children, a swollen kidney may be felt as a smooth, rounded mass in the upper abdomen or back
• Unilateral swelling: The swelling typically occurs on one side of the body, corresponding to the affected kidney, though bilateral hydronephrosis can cause more generalized abdominal distension
• Tenderness: The swollen area may be tender to touch, and gentle pressure may increase discomfort
• Visible in infants: Hydronephrosis in newborns and infants may present as noticeable abdominal swelling or an abdominal mass that parents can observe during diaper changes
• Progressive enlargement: The swelling may gradually increase over time in chronic cases as the kidney continues to expand

While not all patients with hydronephrosis will have visible swelling, its presence indicates significant kidney enlargement and warrants prompt medical evaluation and imaging studies.

6. Blood in the Urine (Hematuria)

The presence of blood in the urine, known medically as hematuria, is an important warning sign that can occur with hydronephrosis. This symptom results from various mechanisms related to the underlying obstruction and kidney swelling.

Hematuria in hydronephrosis can present in two forms:

• Gross hematuria (visible blood): The urine appears pink, red, or cola-colored, indicating a significant amount of blood. This visible blood is immediately noticeable and often alarming to patients
• Microscopic hematuria: Blood cells are present in the urine but not visible to the naked eye, only detectable through laboratory testing. This form is often discovered during routine urine tests

Several factors can cause bleeding in hydronephrosis:

• Kidney stones: When stones cause the obstruction, they can damage the urinary tract lining, leading to bleeding
• Increased pressure: The elevated pressure within the kidney can cause small blood vessels to rupture
• Infection: Inflammation from urinary tract infections can result in bleeding
• Tissue damage: Prolonged stretching of kidney tissues may cause cellular damage and bleeding

Any episode of visible blood in the urine should be evaluated by a healthcare provider, as it can indicate hydronephrosis or other serious urological conditions.

7. Fatigue and General Malaise

Persistent fatigue and a general feeling of being unwell (malaise) are often overlooked but significant symptoms of hydronephrosis, especially when the condition has been present for some time or affects kidney function substantially.

These systemic symptoms develop due to:

• Impaired kidney function: When hydronephrosis reduces the kidney’s ability to filter waste and maintain proper fluid and electrolyte balance, the body’s overall function suffers, leading to fatigue
• Anemia: The kidneys produce erythropoietin, a hormone that stimulates red blood cell production. Reduced kidney function can lead to decreased red blood cell counts, causing tiredness and weakness
• Waste product accumulation: The buildup of metabolic waste products in the bloodstream creates a general feeling of illness and exhaustion
• Chronic pain: Dealing with persistent discomfort can be physically and emotionally draining, contributing to overall fatigue
• Sleep disruption: Frequent nighttime urination or pain can interfere with sleep quality, leading to daytime tiredness
• Body’s response to infection: If hydronephrosis is complicated by infection, the immune response can cause significant fatigue and malaise

While fatigue alone is not specific to hydronephrosis, when combined with other symptoms like flank pain, urinary changes, or recurrent infections, it should prompt further investigation. Many patients describe feeling “off” or “not themselves” for weeks or months before receiving a hydronephrosis diagnosis.

Common Causes of Hydronephrosis

Understanding what causes hydronephrosis can help in recognizing risk factors and seeking appropriate preventive care. Hydronephrosis develops when something blocks or impairs the normal flow of urine from the kidney to the bladder. The causes vary by age and can be broadly categorized as follows:

Obstructive Causes

• Kidney stones: One of the most common causes in adults, stones can lodge in the ureter (the tube connecting the kidney to the bladder) and block urine flow
• Urinary tract tumors: Cancerous or benign growths in the kidney, ureter, bladder, or nearby structures can compress or obstruct the urinary pathway
• Enlarged prostate: In men, particularly older men, an enlarged prostate gland can compress the urethra and cause urine to back up into the kidneys
• Ureteropelvic junction (UPJ) obstruction: A congenital narrowing where the kidney connects to the ureter, often diagnosed in children but sometimes not detected until adulthood
• Blood clots: Clots in the urinary tract can obstruct urine flow, though this is less common

Structural and Anatomical Causes

• Congenital abnormalities: Birth defects affecting the urinary tract structure are a leading cause of hydronephrosis in infants and children
• Vesicoureteral reflux (VUR): A condition where urine flows backward from the bladder into the ureters and kidneys
• Ureterocele: A balloon-like swelling of the ureter at the point where it enters the bladder
• Posterior urethral valves: Abnormal tissue folds in the urethra that obstruct urine flow, occurring in male infants

External Compression

• Pregnancy: The expanding uterus can compress the ureters, particularly on the right side, causing temporary hydronephrosis that typically resolves after delivery
• Abdominal or pelvic masses: Tumors or cysts in surrounding organs can press on the ureters
• Retroperitoneal fibrosis: Excessive fibrous tissue development in the back of the abdomen can encase and compress the ureters

Neurological and Functional Causes

• Neurogenic bladder: Nerve damage from conditions like spinal cord injury, diabetes, or multiple sclerosis can impair bladder function and cause urine retention
• Bladder dysfunction: Conditions affecting normal bladder emptying can lead to backpressure on the kidneys

Prevention Strategies

While not all cases of hydronephrosis can be prevented, especially those caused by congenital abnormalities, there are several strategies that can reduce your risk or help detect the condition early:

Stay Well Hydrated

Drinking adequate amounts of water throughout the day helps prevent kidney stone formation, one of the most common causes of hydronephrosis in adults. Aim for 8-10 glasses of water daily, or enough to keep your urine light yellow in color. Proper hydration also helps flush bacteria from the urinary tract, reducing infection risk.

Maintain a Healthy Diet

• Limit sodium intake: Excessive salt can increase calcium in the urine, promoting stone formation
• Moderate protein consumption: Very high protein diets can increase kidney stone risk
• Reduce oxalate-rich foods if prone to stones: Foods like spinach, nuts, and chocolate contain oxalates that can contribute to certain types of kidney stones
• Consume adequate calcium: Contrary to popular belief, adequate dietary calcium can actually help prevent stones by binding to oxalates in the intestine

Attend Regular Medical Check-ups

Routine physical examinations and urine tests can detect early signs of urinary tract problems before they progress to hydronephrosis. This is particularly important if you have risk factors such as a family history of kidney problems, recurrent UTIs, or known structural abnormalities.

Manage Underlying Conditions

• Prostate health: Men should discuss prostate screening with their healthcare provider, especially after age 50
• Diabetes control: Maintaining good blood sugar control helps prevent nerve damage that can affect bladder function
• Prompt UTI treatment: Seek medical care for urinary tract infections to prevent complications

Prenatal Care

For pregnant women, regular prenatal ultrasounds can detect fetal hydronephrosis, allowing for monitoring and planning appropriate postnatal care if needed. Pregnant women experiencing symptoms of hydronephrosis should inform their healthcare provider promptly.

Don’t Delay Urination

Regularly holding in urine for extended periods can contribute to bladder dysfunction and increase the risk of urinary tract problems. When you feel the urge to urinate, try to use the restroom within a reasonable time frame.

Be Aware of Family History

If you have family members with kidney problems, vesicoureteral reflux, or recurrent kidney stones, inform your healthcare provider. Genetic factors can play a role in some causes of hydronephrosis, and awareness allows for appropriate screening and preventive measures.

Frequently Asked Questions

Can hydronephrosis go away on its own?

Mild cases of hydronephrosis, particularly those caused by temporary conditions like pregnancy or a small kidney stone that passes, may resolve without intervention. However, most cases require medical treatment to address the underlying cause and prevent permanent kidney damage. You should never assume hydronephrosis will resolve on its own without consulting a healthcare provider.

Is hydronephrosis painful?

Hydronephrosis can be painful, especially in acute cases where the blockage develops suddenly. The pain is typically felt in the flank or side and may be severe. However, chronic hydronephrosis that develops slowly over time may cause only mild discomfort or be completely painless, which is why the condition sometimes goes undetected until advanced stages.

How serious is hydronephrosis?

The seriousness of hydronephrosis depends on several factors including whether one or both kidneys are affected, how severe the blockage is, how quickly it developed, and how long it has been present. Mild, unilateral hydronephrosis may have minimal impact, while severe bilateral hydronephrosis can be life-threatening if not treated promptly, potentially leading to kidney failure and requiring emergency intervention.

Can you live a normal life with hydronephrosis?

Many people who receive appropriate treatment for hydronephrosis can live completely normal lives, especially if the condition is caught early and the underlying cause is successfully addressed. Even those with mild chronic hydronephrosis may function well with one kidney compensating for the other. However, ongoing monitoring is typically necessary to ensure kidney function remains stable.

What is the difference between hydronephrosis and kidney stones?

Kidney stones are hard mineral deposits that form in the kidney, while hydronephrosis is the swelling of the kidney due to urine buildup. Kidney stones can cause hydronephrosis when they block the ureter, but hydronephrosis can also result from many other causes unrelated to stones, such as tumors, congenital abnormalities, or prostate enlargement.

How is hydronephrosis diagnosed?

Hydronephrosis is typically diagnosed through imaging studies. Ultrasound is often the first test performed as it’s safe, non-invasive, and effective at showing kidney swelling. CT scans provide more detailed images and can identify the cause of obstruction. Other tests may include MRI, intravenous pyelogram (IVP), or nuclear medicine scans. Blood and urine tests help assess kidney function and detect infection.

Can hydronephrosis occur in both kidneys?

Yes, hydronephrosis can affect one kidney (unilateral) or both kidneys (bilateral). Bilateral hydronephrosis is generally more serious as it affects total kidney function and can lead to acute kidney failure if severe. It often results from bladder outlet obstruction, such as from an enlarged prostate, or lower urinary tract abnormalities.

Is hydronephrosis common during pregnancy?

Mild to moderate hydronephrosis is relatively common during pregnancy, affecting up to 90% of pregnant women to some degree, though most cases are mild and asymptomatic. It typically occurs in the second and third trimesters as the growing uterus compresses the ureters. This pregnancy-related hydronephrosis usually resolves within a few weeks after delivery and rarely causes complications.

When should I see a doctor about hydronephrosis symptoms?

You should seek immediate medical attention if you experience severe flank pain, fever with back pain, complete inability to urinate, or blood in your urine. Schedule an appointment soon if you have persistent back or side pain, changes in urination patterns, recurrent urinary tract infections, or any combination of the symptoms described in this article. Early evaluation and treatment are key to preventing permanent kidney damage.

References:

• Mayo Clinic – Hydronephrosis
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• National Kidney Foundation
• Johns Hopkins Medicine – Hydronephrosis
• American Urological Association
• National Center for Biotechnology Information (NCBI) – Hydronephrosis