Obstructive nephropathy, also know as uropathy, refers to the syndrome caused by urinary tract obstruction, either functional or anatomic. It includes urinary tract dilatation, impedance and the resulting slowing of urine flow, change in the pressure inside the kidney tubular system and impaired kidney function. Blockage to the flow of urine leads to hydronephrosis and hydroureter.
Obstructive nephropathy is a common condition, and its incidence rises with advancing age.
In children, the leading cause is ureteropelvic junction obstruction, with an incidence of one in 1500. Urolithiasis in children occurs in 1-5%
Clinical Manifestations and Causes
Obstructive nephropathy may manifest in varying ways, from asymptomatic to acute renal failure.
It may be acute or chronic, unilateral or bilateral. Acute obstruction is most often due to ureteral stones. Chronic causes range include:
- Benign prostatic hyperplasia
- Neurogenic bladder
- urinary tract stones
- ureteral stricture
- congenital anomalies such as uretero-pelvic junction stenosis
- Fibrosis of the retroperitoneum
- Tumors of the ureter
- Cancers of the colon or of the pelvic viscera
- Metastatic tumors in the abdomen
Obstruction may not be present in all cases of urinary tract dilatation, such as in congenital megaureter, or following surgery on the renal pelvis or the ureter.
The symptoms of obstructive nephropathy may stem from the cause of obstruction as well as the dilated organ itself. Thus they include
- Back and loin pain, or groin pain
- Nausea and vomiting
- Urgency or frequency of urination
- Incomplete urination
- Dribbling of urine
Diagnosis and treatment
Diagnosis is based upon clinical examination followed by imaging tests such as intravenous urography, retrograde ureterography, ultrasound, CT scans, and contrast imaging.
Ultrasound has become the imaging technique of choice because it is available almost everywhere and is safe but sensitive.
CT scans are especially useful in identifying retroperitoneal or pelvic growths which are obstructing the ureter.
Dye excretion urography will show the characteristic dense nephrogram in case of ureteric obstruction.
Renal scintigraphy using I123-hippuran or technetium scans are helpful in assessing kidney function in a less invasive way, including the accumulation of the isotope, its transit time and excretion.
There are several other methods such as perfusion pressure studies and renal scintigraphy to help differentiate obstructed urinary tracts from those which are only dilated.
Early diagnosis of urinary obstruction is vital to prevent further damage or to reverse renal impairment.
Treatment is focused on removing the cause of obstruction, preventing any deterioration of kidney function and if possible, reversing any impairment that has already occurred. Acute obstruction is relieved by using stents, nephrostomy tubes or catheters.
Chronic obstruction often requires surgical repair, drainage of infection, or removal of one kidney.
Chronic obstruction may result in chronic kidney disease and renal failure. Overdistension of the bladder, such as following a bladder stone, may result in bladder damage and failure of proper voiding or leakage of urine.