From the Guidelines
Hydronephrosis is primarily caused by conditions that obstruct the flow of urine from the kidney to the bladder, including urolithiasis, malignant obstruction, stricture, upper urinary tract infection, and other factors that increase pressure in the collecting system of the kidney. The causes of hydronephrosis can be classified by the level of obstruction, complete versus partial obstruction, and intrinsic versus extrinsic obstruction 1.
Common Causes of Hydronephrosis
- Urolithiasis (kidney stones)
- 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 seen with an enlarged uterus or pelvic organ prolapse
- Endometriosis
- Schistosomiasis
- Drug effects, such as those from cyclophosphamide or ketamine
- Vessel-related and/or congenital ureteropelvic junction obstruction
- Congenital posterior urethral valves These conditions can lead to obstructive hydronephrosis, which may be further classified based on the level and nature of the obstruction 1.
Importance of Prompt Diagnosis and Treatment
Prompt treatment of the underlying cause of hydronephrosis is crucial to prevent permanent renal damage 1. The condition can often be silent, especially in adults, and may be detected incidentally or with nonspecific symptoms 1.
Diagnostic Approaches
Imaging studies such as CT urography (CTU) and scintigraphic diuresis renography (DRG) can be used to evaluate hydronephrosis and differentiate between nonobstructive and obstructive causes 1. CTU involves unenhanced and contrast-enhanced images to visualize the upper and lower urinary tracts, while DRG uses nuclear medicine and diuretics to assess urinary tract function 1. In clinical practice, identifying the underlying cause of hydronephrosis is essential for guiding treatment and preventing long-term kidney damage, and should be based on the most recent and highest quality evidence available, such as the studies published in the Journal of the American College of Radiology in 2024 1.