What is functional hydronephrosis (Hydronephrosis)?

From the Guidelines

Functional hydronephrosis should be managed with a focus on addressing the underlying cause, and treatment may include monitoring with ultrasound, medications such as alpha-blockers, and ensuring adequate hydration, as prompt treatment can prevent permanent renal damage 1.

Key Considerations

• The condition occurs when the normal flow of urine from the kidney to the bladder is impaired due to functional rather than anatomical issues.
• Treatment depends on the underlying cause, and in mild cases, observation may be sufficient as some cases resolve spontaneously, especially in children.
• For persistent cases, medications such as alpha-blockers (like tamsulosin 0.4mg daily) may help improve urine flow, and antibiotics are prescribed if infection is present, with options including trimethoprim-sulfamethoxazole or ciprofloxacin for 7-14 days depending on severity.

Diagnostic Approaches

• Initial imaging evaluation of hydronephrosis of unknown etiology can be conducted via CT urography (CTU) without and with contrast, MR urography (MRU) without and with contrast, or scintigraphic evaluation with mercaptoacetyltriglycine (MAG3) imaging 1.
• For symptomatic patients, CTU without and with contrast, MRU without and with contrast, MAG3 scintigraphy, or ultrasound of the kidneys and bladder with Doppler imaging are all viable initial imaging studies.

Management and Follow-up

• Regular follow-up is essential to monitor kidney function and prevent permanent damage, with renal function tests and ultrasound evaluations typically scheduled every 3-6 months initially.
• Surgical intervention is reserved for severe cases that don't respond to conservative management.
• The condition occurs because the ureter or bladder muscles don't coordinate properly, creating functional obstruction despite no physical blockage.

Important Points to Consider

• Hydronephrosis can be classified by cause and by unilateral versus bilateral involvement, and obstructive hydronephrosis can be 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.

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 can be diagnosed using various modalities, including sonography, radiography, magnetic resonance imaging, and nuclear medicine technology 3.
• Machine learning algorithms can recognize hydronephrosis in non-contrast CT images, with high accuracy 4.

Causes and Effects of Hydronephrosis

• Hydronephrosis 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.
• It can result in permanent renal injury, necessitating the utilization of imaging modalities for accurate diagnosis 4.
• The presence of hydronephrosis can be associated with a ureteral stone in patients with renal colic, but ultrasound is less sensitive than computerized tomography for the detection of ureterolithiasis 5.

Grading and Treatment of Hydronephrosis

• A grading scale for hydronephrosis is presented, and treatment options are explained 3.
• The severity of hydronephrosis can clarify prognosis and guide management for emergency department patients with acute ureteral colic 6.
• Differentiating "moderate-severe" from "absent-mild" hydronephrosis provides risk stratification value, and severe hydronephrosis is an important finding that warrants definitive imaging and referral 6.

Imaging Modalities for Hydronephrosis

• Ultrasound accurately identifies hydronephrosis, but it is less sensitive than computerized tomography for the detection of ureterolithiasis 5.
• Computed tomography is the gold standard for stone imaging and can assess hydronephrosis and stone size 6.
• Machine learning-assisted radiomics can be considered an effective tool for accurately predicting the presence of hydronephrosis 4.