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BASICS

Description

  • Hydronephrosis: dilation of renal calyces and pelvis.
  • May be accompanied by hydroureter.
  • Not synonymous with obstructive uropathy (renal damage from obstruction).
  • Can be acute or chronic, partial or complete, unilateral or bilateral.

Epidemiology

  • More common in children due to congenital anomalies.
  • In adults, more common in women <60 years and men >60 years.

ETIOLOGY AND PATHOPHYSIOLOGY

  • Caused by increased pressure in urinary collecting system from obstruction or nonobstructive causes.
  • Obstruction sites:
  • Kidney: nephrolithiasis, tumors, congenital ureteropelvic junction (UPJ) obstruction, blood clots.
  • Ureter: stones, strictures, tumors, retroperitoneal fibrosis, external compression.
  • Bladder: neurogenic bladder, outlet obstruction, extrinsic compression.
  • Urethra: prostatic hypertrophy/cancer, strictures.
  • Transplant kidneys: ureteral reflux, strictures, lymphocele compression, bladder dysfunction.
  • Nonobstructive causes: high urinary output (e.g., diabetes insipidus), physiologic pregnancy changes.

Pediatric Considerations

  • Antenatal hydronephrosis detected in 1-5% pregnancies by ultrasound.
  • Common causes: vesicoureteral reflux (VUR), congenital UPJ obstruction, posterior urethral valves, neurogenic bladder.
  • Neonatal abdominal mass common presentation.

Pregnancy Considerations

  • Physiologic hydronephrosis in up to 80% of pregnant women, more on right side.
  • Caused by hormonal and mechanical factors.
  • Usually asymptomatic; symptomatic cases require evaluation for stones or infection.

DIAGNOSIS

History

  • Varies by cause and severity.
  • Symptoms: flank/abdominal pain (vague to severe), hematuria, nausea, vomiting.
  • Fever/chills suggest infection.
  • Anuria indicates bilateral or solitary kidney obstruction.
  • Chronic symptoms of kidney disease or bladder outlet obstruction may be present.
  • Relevant history: malignancy, surgery, trauma, gynecologic disease, smoking, drug exposures.

Physical Exam

  • Volume overload signs (edema, HTN).
  • Fever/tachycardia if infection.
  • Abdominal exam: CVA tenderness, palpable bladder or mass.
  • Pelvic exam: masses, enlarged prostate, urethral abnormalities.

Differential Diagnosis

  • Kidney infection, nephrolithiasis, urinary tract obstruction, malignancy.

Diagnostic Tests

  • Urinalysis: hematuria, proteinuria, pyuria.
  • Urine culture to rule out infection.
  • Blood tests: renal function, electrolytes, CBC.
  • PSA in men >50 or suspected prostatic disease.
  • Urine cytology if malignancy suspected.
  • Imaging:
  • Ultrasound (US): Screening tool; shows dilated collecting system, parenchymal changes; safe in pregnancy.
  • Noncontrast helical CT (NHCT): Best for stones; shows hydronephrosis, hydroureter, perinephric stranding.
  • Radionuclide scan (DTPA/MAG-3): Assesses obstruction and split renal function.
  • Multiphase CT urography: Assesses obstruction, renal function, and soft tissue causes.
  • MR urography: Alternative if CT inconclusive or contraindicated; safe in pregnancy.
  • Cystoscopy and retrograde pyelogram may be needed for detailed evaluation.

TREATMENT

General Measures

  • Correct fluid/electrolyte abnormalities.
  • Pain control.
  • Antibiotics if infection present.
  • Prompt relief of obstruction if UTI, impaired renal function, or pain present.
  • Bladder outlet obstruction: catheterization.
  • Ureteric obstruction: stenting (retrograde or percutaneous).

Medical Expulsive Therapy

  • Ξ±-blockers or calcium channel blockers for ureteral stones <10 mm if stable and no infection.

Surgery/Procedures

  • Congenital UPJ obstruction: pyeloplasty (open/laparoscopic) or endopyelotomy.
  • Nephrolithiasis: extracorporeal shock wave lithotripsy (ESWL) or ureteroscopy.
  • Transitional cell carcinoma: nephroureterectomy.
  • Retroperitoneal fibrosis: ureterolysis.
  • Prostate obstruction: TURP or prostatectomy.

ONGOING CARE

  • Monitor renal function and blood pressure until stabilized.
  • Repeat imaging (ultrasound) to assess resolution.
  • Consider diuretic renal scan if persistent hydronephrosis.

PROGNOSIS

  • Depends on cause, presence of infection, degree and duration of obstruction.
  • Some recovery possible despite days of obstruction.
  • Delayed treatment risks irreversible renal damage.

COMPLICATIONS

  • Urinary stasis β†’ infection and stones.
  • Renal atrophy and loss of function.
  • Spontaneous calyceal rupture with urine extravasation.
  • Postobstructive diuresis: polyuria after obstruction relief; managed with hypotonic fluids to avoid volume overload.

REFERENCES

  1. Worster A, Preyra I, Weaver B, et al. The accuracy of noncontrast helical computed tomography versus intravenous pyelography in the diagnosis of suspected acute urolithiasis: a meta-analysis. Ann Emerg Med. 2002;40(3):280-286.
  2. Ramsey S, Robertson A, Ablett MJ, et al. Evidence-based drainage of infected hydronephrosis secondary to ureteric calculi. J Endourol. 2010;24(2):185-189.
  3. Seitz C, Liatsikos E, Porpiglia F, et al. Medical therapy to facilitate the passage of stones: what is the evidence? Eur Urol. 2009;56(3):455-471.
  4. Aboumarzouk OM, Kata SG, Keeley FX, et al. Extracorporeal shock wave lithotripsy (ESWL) versus ureteroscopic management for ureteric calculi. Cochrane Database Syst Rev. 2011;(12):CD006029.
  5. Shen P, Jiang M, Yang J, et al. Use of ureteral stent in extracorporeal shock wave lithotripsy for upper urinary calculi: a systematic review and metaanalysis. J Urol. 2011;186(4):1328-1335.
  6. Cohen EP, Sobrero M, Roxe DM, et al. Reversibility of long-standing urinary tract obstruction requiring long-term dialysis. Arch Intern Med. 1992;152(1):177-179.

Clinical Pearls

  • Ultrasound and noncontrast CT identify most causes of hydronephrosis.
  • Relief of obstruction is the primary treatment.
  • Prompt drainage required for infected hydronephrosis (pyonephrosis).
  • Postobstructive diuresis is managed with careful fluid replacement avoiding volume overload.