Hydronephrosis

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).
• 

⭐ [Placeholder for exam-favourite fact]

Hydronephrosis: Etiology & Pathophysiology - The Blockage Culprits

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.

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.