Obstructive Uropathy

Kumud P Mehta
Obstructive Uropathy - Investigations
After clinical evaluation, imaging of urinary tract is necessary.
Ultrasonography of kidneys ureters, urinary bladder is the most important single investigation in diagnosis of obstructive uropathy. Dilatation of pelvicalyceal system with hydronephrosis is a hallmark of PUJ obstruction. Hydronephrosis with hydroureter in VUJ obstruction, distended bladder and dilated urethra in PU valves are classical findings on antenatal USG. Postnatal USG should be done between days 3-7 when transient oliguria in newborns subsides and normal urine output is established. Ultrasonography can detect calculi, ureterocele and bladder diverticuli.

X-ray of KUB for diagnosis of calculi.

Micturating Cystourethrogram: If hydronephrosis is associated with distended bladder in male infant, catheterisation is done to relieve back pressure and micturating cystourethrogram performed to diagnose posterior urethral valves which requires immediate surgical intervention to relive obstruction and prevent renal damage.

If USG reveals dilatation of pelvis (AP diameter > 10mm) without dilated ureter/s and normal urinary bladder, serial USG's done at 1 month, 3 months, 6 months and 1 year combined with Tc99DTPA renal scan with Lasix at 1 month and 6 month to detect severity of PUJ obstruction is necessary to decide need for surgical intervention.

Mild to moderate PUJ obstruction can resolve over 12-18 months and requires close observation and regular follow up with USG and Tc99DTPA renal scan. (IVP is replaced by renal scan in children especially below 1 year of age because of poor images, risk of allergic reaction to radio-contrast dye, radiation risk etc.)

Laboratory evaluation includes S. creatinine with other tests to detect metabolic acidosis, hyperkalemia, rickets and urine routine and culture, colony count to detect UTI. High creatinine valves in PU valves or bilateral PUJ obstructions are reduced to 0.6-0.7 mg/dl after relief of obstruction by surgery. A S. creatinine value of 0.8 mg or more after relief of obstruction indicates developmental defects of kidneys with irreversible renal dysfunction which progresses to chronic renal failure/end stage renal disease later. Dilated and obstructed urinary tract is favorable for recurrent UTI, which can result in renal scars and contribute to CRF/ESRD. Hence prevention of UTI is very essential using antibiotic prophylaxis with amoxycillin/cephalexin (50mg bid) in first 3 months of life followed by cotriamoxazole or Nitrofurantoin as a single night dose for 6 months - 5 years or till dilatation resolves and obstruction is relieved.

Obstructive Uropathy Obstructive Uropathy 01/03/2001
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