Hydronephrosis

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Hydronephrosis: Definition & Overview - Swollen Kidneys 101

  • Definition: Dilation of the renal pelvis and calyces due to impaired urine outflow (obstruction).
  • Pathophysiology: Leads to ↑ intra-renal pressure, potentially causing progressive renal parenchymal damage, atrophy, and ↓ GFR.
  • Key Classifications:
    • Laterality: Unilateral or Bilateral.
    • Etiology/Onset: Congenital (e.g., PUJO, VUR) or Acquired (e.g., calculi, tumors, strictures).
    • Timing: Acute or Chronic.
  • Severity Grading: Commonly by Society for Fetal Urology (SFU) system (Grades 0-IV).
  • Hydronephrosis grades: Normal, Mild, Moderate, Severe

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Hydronephrosis: Etiology & Pathophysiology - The Blockage Culprits

UPJ obstruction in infant

Pathophysiology: Obstruction → ↑ Pressure → Dilation → Damage

  • Primary Blockage Culprits:
    • Ureteropelvic Junction Obstruction (UPJO): Most common overall.
    • Posterior Urethral Valves (PUV): Key cause in newborn males.
    • Vesicoureteral Reflux (VUR): High grades (e.g., IV-V) can lead to hydronephrosis.
    • Ureterovesical Junction Obstruction (UVJO).
  • Other Contributing Factors:
    • Ureterocele, ectopic ureter.
    • Neurogenic bladder dysfunction.
    • Acquired: Stones, strictures, extrinsic compression (e.g., aberrant vessels, tumors).

⭐ UPJO is the most common cause of significant antenatal hydronephrosis.

Hydronephrosis: Clinical Presentation - Spotting Trouble Signals

  • Antenatal: Often an incidental finding on routine maternal ultrasound.
  • Postnatal:
    • Frequently asymptomatic, especially if unilateral.
    • Palpable abdominal/flank mass.
    • Recurrent UTIs: fever, irritability, vomiting, poor feeding.
    • Failure to thrive (FTT).
    • Gross or microscopic hematuria.
    • Intermittent flank/abdominal pain (older children, Dietl's crisis).
    • Rarely, hypertension.

⭐ Antenatal hydronephrosis (ANH) is the most common urological anomaly detected on prenatal ultrasound, affecting 1-5% of pregnancies.

Hydronephrosis: Diagnosis & Grading - Kidney Detective Work

  • Initial Imaging: Ultrasonography (USG) is primary.
    • Antenatal: Measures Anteroposterior Diameter (APD).
      • Mild: APD <10mm (2nd tri), <10-15mm (3rd tri).
      • Severe: APD >15mm (3rd tri).
    • Postnatal: Confirms, monitors, guides further tests. APD >10mm significant.
  • Diagnostic Flow:
  • Key Investigations:
    • Micturating Cystourethrogram (MCU): Essential for VUR, Posterior Urethral Valves (PUV).
    • Diuretic Renography (MAG3/DTPA): Differentiates obstructive vs. non-obstructive.

      ⭐ T1/2 > 20 minutes post-furosemide strongly suggests obstruction.

  • SFU Grading (Society for Fetal Urology):
    • G1: Pelvis dilated. G2: Pelvis + some calyces.
    • G3: All calyces dilated, normal parenchyma. G4: G3 + parenchymal thinning. SFU Grades of Hydronephrosis Diagram

Hydronephrosis: Management Principles - Fixing the Plumbing

  • Core Goals: Relieve obstruction, preserve renal function, prevent complications (UTI, stones).
  • Strategy: Based on severity (SFU grade), symptoms, laterality, etiology, and renal function (DRF).
  • Conservative: Watchful waiting, serial USG. Antibiotics for recurrent UTI / high-grade VUR.
    • Intervention: ↑SFU grade, DRF < 40% or ↓ > 10%, symptoms, complications (UTI, stones).
  • Surgical:
    • Definitive (etiology-based): Pyeloplasty (PUJO), ureteric reimplantation (VUR/VUJO), valve ablation (PUV).
    • Temporary (severe obstruction/sepsis): PCN, ureteric stent.

⭐ Most cases of antenatally detected, asymptomatic, unilateral hydronephrosis with good differential renal function (DRF > 40%) can be managed conservatively with serial monitoring.

High-Yield Points - ⚡ Biggest Takeaways

  • Hydronephrosis, dilation of renal pelvis/calyces, is most commonly due to pelviureteric junction (PUJ) obstruction.
  • Often first identified on routine antenatal ultrasound.
  • Postnatal workup: renal ultrasound (RUS), MCU/VCUG (for VUR), and diuretic renography (DRS/MAG3 scan) to assess obstruction.
  • The Society for Fetal Urology (SFU) grading system is widely used for severity.
  • Complications include recurrent UTIs, renal scarring, and impaired renal function.
  • Management: Observation or surgical pyeloplasty for significant PUJO and/or symptomatic cases.

Practice Questions: Hydronephrosis

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Which of the following is typically seen on ultrasound in acute pyelonephritis?

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Flashcards: Hydronephrosis

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Newborns males with posterior urethral valves may have a _____ mass and bilateral hydronephrosis

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Newborns males with posterior urethral valves may have a _____ mass and bilateral hydronephrosis

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