Symptoms and Causes of Hydronephrosis: What You Need to Know

Hydronephrosis, the medical term for kidney swelling due to a buildup of urine, presents a range of symptoms depending on the severity and underlying cause. While some individuals may experience noticeable discomfort, others remain asymptomatic for long periods, making early detection challenging. The condition typically arises from two primary categories of causes: mechanical obstruction and functional (or dynamic) impairment in the urinary tract.

Common Symptoms of Acute and Chronic Hydronephrosis

In cases of acute hydronephrosis, patients often report sudden and intense pain in the flank or lower back. This pain can radiate toward the lower abdomen or groin and is frequently associated with conditions like kidney stones. Known medically as renal colic, this type of pain comes in waves and may be accompanied by visible blood in the urine (gross hematuria) or blood detected only under a microscope (microscopic hematuria).

Chronic hydronephrosis, on the other hand, tends to develop gradually. Many patients do not notice any obvious symptoms until significant kidney damage has occurred. In these instances, the first signs might include subtle changes in kidney function, detected only through routine blood or urine tests. If left untreated, chronic swelling can lead to decreased kidney function or even permanent renal failure.

Primary Causes: Mechanical Obstruction Explained

The most frequent cause of hydronephrosis is mechanical blockage within the urinary system. Among these, kidney stones are the leading culprit. When a stone obstructs the ureter, it prevents urine from draining properly, leading to pressure buildup and kidney distension.

Other structural issues that can cause blockages include tumors in the bladder, ureters, or surrounding organs, as well as complications from infections such as tuberculosis of the urinary tract. Tumors, especially those affecting the urinary epithelium, often present with painless gross hematuria—an important warning sign that warrants immediate urological evaluation.

Less Common but Serious Structural Issues

Congenital abnormalities also play a role, particularly in younger patients. For example, a condition known as megaureter—where one or both ureters are abnormally enlarged—can impair normal urine flow from the kidneys to the bladder. These cases may go unnoticed for years but can eventually result in recurrent infections or impaired kidney function.

Functional and Neurogenic Causes of Urinary Backflow

Not all cases of hydronephrosis stem from physical blockages. Some are caused by functional disorders, commonly referred to as dynamic or neurogenic obstructions. A typical scenario involves lower urinary tract obstruction, often due to benign prostatic hyperplasia (BPH) in older men or urethral strictures resulting from injury or infection.

When the bladder cannot empty completely, residual urine accumulates and increases pressure within the urinary system. Over time, this can trigger vesicoureteral reflux—where urine flows backward into the kidneys—leading to dilation and potential damage. Patients with these conditions usually report symptoms such as weak urine stream, frequent urination, urgency, or incomplete bladder emptying.

Risks of Complications: Infection and Sepsis

One of the most dangerous complications of untreated hydronephrosis is urinary tract infection progressing to pyelonephritis or even sepsis. If bacteria enter the stagnant urine trapped in the swollen kidney, a severe systemic infection can develop rapidly. Signs include high fever, chills, nausea, and confusion—requiring emergency medical intervention.

Treatment Approaches Based on Underlying Cause

Effective management of hydronephrosis focuses on identifying and addressing the root cause. In many cases, removing an obstructing stone via lithotripsy or endoscopic surgery can restore normal urine flow and allow the kidney to recover. For tumor-related blockages, treatment may involve surgical resection, chemotherapy, or radiation, depending on the diagnosis.

In patients with chronic obstruction due to prostate enlargement, procedures such as transurethral resection of the prostate (TURP) can significantly improve urinary drainage and prevent further kidney damage.

Unfortunately, in advanced cases where the kidney has been severely damaged and no longer functions, nephrectomy—the surgical removal of the affected kidney—may be necessary. Fortunately, humans can live normally with a single healthy kidney, so this procedure can be life-saving when appropriate.

Early diagnosis through imaging studies like ultrasound, CT scans, or MRI plays a crucial role in preventing long-term complications. Anyone experiencing persistent back pain, unexplained changes in urination, or signs of infection should seek prompt medical evaluation to rule out hydronephrosis and its potentially serious consequences.