From the Guidelines
Hydronephrosis often indicates an obstruction in the urinary tract that prevents normal urine flow, causing the kidney to swell with backed-up urine, and can be due to various causes such as urolithiasis, malignant obstruction, or supravesical or bladder dysfunction, as noted in a 2024 study published in the Journal of the American College of Radiology 1.
Causes and Classification of Hydronephrosis
Hydronephrosis can be classified by cause and by unilateral versus bilateral involvement, with obstructive hydronephrosis further classified by level of obstruction, complete versus partial obstruction, and intrinsic versus extrinsic obstruction 1. The causes of hydronephrosis are diverse and include:
- Urolithiasis
- Malignant obstruction
- Stricture
- Upper urinary tract infection
- Traumatic or ischemic injury
- Postradiation changes
- Retroperitoneal fibrosis
- Supravesical or bladder dysfunction
- Bladder outlet obstruction, such as prostatic hyperplasia
- Mechanical compression, as with an enlarged uterus or pelvic organ prolapse
- Endometriosis
- Schistosomiasis
- Drug effects, such as cyclophosphamide or ketamine
- Vessel-related and/or congenital ureteropelvic junction obstruction
- Congenital posterior urethral valves
Diagnosis and Management
Diagnosis of hydronephrosis often involves imaging studies, with CT urography (CTU) being an effective tool for visualizing both the upper and lower urinary tracts, as it can help differentiate nonobstructive hydronephrosis from hydronephrosis due to true functional obstruction 1. Scintigraphic diuresis renography (DRG) is another diagnostic method that uses nuclear medicine and the administration of a diuretic to assess urinary tract function. Prompt treatment is crucial to prevent permanent renal damage, and the approach depends on the underlying cause, which might involve procedures to remove stones, stent placement, or surgery in more complex cases.
Importance of Prompt Medical Attention
Given that hydronephrosis can lead to permanent kidney damage if left untreated, as highlighted by the potential for silent upper urinary tract deterioration in adults 1, it is essential to seek medical attention promptly if symptoms such as flank pain, urinary tract infections, or difficulty urinating are experienced. Early diagnosis and treatment can significantly improve outcomes and preserve kidney function.
From the Research
Hydronephrosis Indications
Hydronephrosis often indicates several conditions, including:
- Abdominal or pelvic pathology, which can lead to acute kidney injury and permanent nephron loss if not corrected 2
- Ureteral stones or ureteral stone size >5mm, as hydronephrosis on ultrasound is predictive of a ureteral stone on CT 3
- Upper urinary tract infectious calculi, where the degree of hydronephrosis and CT value of calculi are negatively correlated with the efficacy of ureteroscopic lithotripsy (URSL) 4
- Renal colic, where hydronephrosis is a common finding and its resolution is associated with stone passage 5
Diagnostic Considerations
Hydronephrosis can be diagnosed using various modalities, including:
- Sonography
- Radiography
- Magnetic resonance imaging
- Nuclear medicine technology
- Computed tomography (CT) scan
- Ultrasound, which is comparable to CT in detecting severity of hydronephrosis 3
Clinical Implications
The presence and resolution of hydronephrosis have important implications for patient care, including: