Introduction
Obstructive uropathy includes congenital and acquired lesions that obstruct the urinary system and can lead to damage to renal parenchyma due to backpressure or urinary tract infections occurring in stagnant urine.
The approach to obstructive uropathy should be
- To detect site of obstruction: pelviureteral junction (PUJ), vesicoureteral junction (VUJ), ureters, urethra
- To find out whether obstruction is complete or partial, unilateral or bilateral
- To detect the cause of obstruction
- To decide need for surgery and to plan the medical treatment
Causes of obstructive uropathy in children
Congenital development defects of kidney and urinary tract
- Commonest: pelviureteral junction(PUJ) obstruction.
- Vesico-ureteral obstruction, ureterocele, diverticuli of bladder
- Posterior urethral valves with subvesical obstruction, anterior urethral valves, urethral atresia, meatal stenosis.
Dilatation of the proximal part of the urinary tract can be detected by antenatal sonography done at 16-18 weeks and then serially at 24-26 weeks and 30-32 weeks of gestation. Obstruction in utero can affect renal development and can cause permanent damage to renal function.
Acquired conditions
- Calculi in the ureter/s or urinary bladder or urethra
- Strictures due to tuberculosis
- Benign or malignant tumors in the urinary bladder or pressing from outside
- Post urologic surgery due to blood clots or procedures like cystoscopy etc.
Functional obstruction
- Neurologic diseases: meningomyelocele, lipomeningocele and other spinal defects.
- Non neurogenic bladder
Obstructive Uropathy - Clinical Evaluation
Clinically obstructive uropathy presents as recurrent UTI, hypertension, renal failure or calculus disease, or abnormal USG. Clinical evaluation of a suspected case of obstructive uropathy should include weight and height percentiles to detect growth retardation which may be the first clue to chronic renal insufficiency if the diagnosis is missed in the first year. B.P; examination of spine for nevus, a tuft of hair or lipoma (indicates underlying spinal defects); palpation of abdomen for renal lumps (hydronephrosis); persistently distended, firm urinary bladder (indicates distal obstruction due to PUV) should be looked for. Observing urinary stream in the male newborns is important to diagnose posterior urethral valves wherein the urinary stream is poor, interrupted with dribbling and straining while passing urine.
Investigations
After clinical evaluation, imaging of the urinary tract is necessary.
Ultrasonography
of kidneys ureters, the urinary bladder is the most important single investigation in the diagnosis of obstructive uropathy. Dilatation of the 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 diverticula.
X-ray of KUB
for diagnosis of calculi.
Micturating Cystourethrogram:
If hydronephrosis is associated with the distended bladder in male infant, catheterization is done to relieve back pressure and micturating cystourethrogram performed to diagnose posterior urethral valves which require immediate surgical intervention to relieve obstruction and prevent renal damage.
If USG reveals dilatation of pelvis (AP diameter >10 mm) 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 months to detect the severity of PUJ obstruction are necessary to decide the 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 an allergic reaction to the radio-contrast dye, radiation risk, etc.)
Laboratory Evaluation
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 amoxicillin/cephalexin (50 mg bid) in the first 3 months of life followed by co-trimoxazole or nitrofurantoin as a single night dose for 6 months - 5 years or till dilatation resolves and obstruction is relieved.
Obstructive Uropathy - Management
Management of PUJ obstruction depends on:
- Unilateral PUJ with mild to moderate hydronephrosis with normal contralateral kidney-conservative medical management-prophylactic antibiotics for 1 year.
- Unilateral severe PUJ obstruction with reduced renal function(35% or less)- surgery indicated at six months.
- Bilateral PUJ obstruction:
If AP diameter of pelvis >20 mm - surgery
If AP diameter of pelvis <20 mm - monitoring with USG and if dilatation increases - surgery.
Pyeloplasty is the surgery done by 3 months on the side with greater dilatation or lesser function. Mostly contralateral surgery is required later on.
Obstructive Uropathy - Follow Up
A regular follow up of a child with obstructive uropathy is important even after surgery because many children need oral alkali therapy for acidosis, Vitamin D & calcium supplements for renal rickets, and treatment to control anemia and hypertension which goes a long way in preserving renal function and helping in growth and development.
Yearly, S. Creatinine, USG, and BP with growth monitoring is the minimum requirement for follow up to 15- 20 years of age for a case of obstructive uropathy diagnosed at birth.