What is the diagnosis and treatment for Hydronephrosis (swelling of the kidney due to impaired renal function)?

From the Guidelines

Hydronephrosis requires prompt treatment to prevent permanent kidney damage, and the treatment approach depends on the underlying cause and severity of the condition. The condition is characterized by swelling of the kidney due to urine backup, typically caused by an obstruction in the urinary tract 1. For mild cases, observation with regular ultrasound monitoring may be sufficient, while more significant cases require relief of the obstruction, which might involve placing a ureteral stent or nephrostomy tube to bypass the blockage, or surgical correction of anatomical abnormalities like ureteropelvic junction obstruction or removal of kidney stones 1.

Causes and Classification

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. Causes of hydronephrosis include urolithiasis, malignant obstruction, stricture, upper urinary tract infection, traumatic or ischemic injury, postradiation changes, retroperitoneal fibrosis, supravesical or bladder dysfunction, bladder outlet obstruction as with prostatic hyperplasia, mechanical compression as with enlarged uterus or pelvic organ prolapse, endometriosis, schistosomiasis, drug effects as with cyclophosphamide or ketamine, vessel-related and/or congenital ureteropelvic junction obstruction, and congenital posterior urethral valves 1.

Diagnostic Approach

CT urography (CTU) is an imaging study that can be used to improve visualization of both the upper and lower urinary tracts, and it usually involves unenhanced images followed by intravenous (IV) contrast-enhanced images, including nephrographic and excretory phases acquired at least 5 minutes after contrast injection 1. CT abdomen and pelvis without IV contrast can also be useful in the setting of flank pain in general, and it may be useful in evaluating symptomatic patients when US is inconclusive 1.

Treatment and Management

Prompt treatment is essential as prolonged hydronephrosis can lead to permanent kidney damage. Antibiotics such as ciprofloxacin 500mg twice daily for 7-14 days are prescribed if infection is present, and pain management with medications like acetaminophen or NSAIDs may be needed 1. Patients should increase fluid intake to 2-3 liters daily unless contraindicated. Regular follow-up with urinalysis, renal function tests, and imaging is necessary to monitor resolution and prevent recurrence. In cases where percutaneous antegrade ureteral stenting is required, technical success can be achieved in up to 91.8% of renal units, with clinical success occurring in up to 89.8% of patients 1.

Key Considerations

• The presence of hydronephrosis can help predict the likelihood of ureteral stone on subsequent CT, with a positive predictive value of up to 88% 1.
• CT hydronephrosis has a sensitivity of up to 88.0% and specificity of up to 85.0% for predicting ureteric and obstructing renal pelvic calculi on CT 1.
• The absence of hydronephrosis does not rule out the diagnosis of ureteral stone, with a negative predictive value of up to 65% 1.

From the Research

Definition and Diagnosis of Hydronephrosis

• Hydronephrosis is diagnosed more often with the increased availability of computed tomography and ultrasound scanning 2
• It is an important consideration in patients with abdominal or pelvic pathology as progressive dilation of the upper urinary tract can lead to acute kidney injury and, if not corrected, permanent nephron loss 2
• Hydronephrosis can be diagnosed using various modalities, including sonography, radiography, magnetic resonance imaging, and nuclear medicine technology 3

Causes and Effects of Hydronephrosis

• Hydronephrosis, or dilation of the renal collecting system, can be caused by various factors, including obstruction of the urinary tract 4, 3
• Prompt treatment of hydronephrosis is crucial to prevent abscess, electrolyte instability, and a progressive loss of renal function 4
• In some cases, hydronephrosis can resolve or improve spontaneously, especially in newborns with severe unilateral hydronephrosis initially treated nonoperatively 5

Treatment Options for Hydronephrosis

• Treatment options for hydronephrosis include percutaneous nephrostomy tubes, ureteral stenting, and pyeloplasty 4, 6
• The choice of treatment depends on the underlying cause of the hydronephrosis, as well as the severity of the condition 6
• In some cases, conservative treatment may be sufficient, while in other cases, more aggressive medical treatment may be necessary 4

Grading and Follow-up of Hydronephrosis

• A grading scale for hydronephrosis is available to assess the severity of the condition 3
• Close follow-up is necessary to identify patients who require prompt treatment to prevent permanent loss of renal function 5
• In newborns with severe unilateral hydronephrosis, nonoperative treatment with close follow-up is safe and recommended, especially during the first 2 years 5