Hydronephrosis is dilation of the renal pelvis and calyces of one or both kidneys due to an obstruction.
Obstruction to the normal flow of urine causes the urine to back up, resulting in increased pressure in the kidney. If the obstruc-tion is in the urethra or the bladder, the back pressure affects both kidneys, but if the obstruction is in one of the ureters because of a stone or kink, only one kidney is damaged.
Partial or intermittent obstruction may be caused by a renal stone that has formed in the renal pelvis but has moved into the ureter and blocked it. The obstruction may be due to a tumor pressing on the ureter or to bands of scar tissue resulting from an abscess or inflammation near the ureter that pinches it. The dis-order may be due to an odd angle of the ureter as it leaves the renal pelvis or to an unusual position of the kidney, favoring a ureteral twist or kink. In elderly men, the most common cause is urethral obstruction at the bladder outlet by an enlarged prostate gland. Hydronephrosis can also occur in pregnancy because of the enlarged uterus. High pressure in the bladder during the fill-ing phase, generally 15 cm H2O or higher, has been found to re-sult in hydronephrosis, due to the high pressure radiating to one or both kidneys via the ureter (Ghobish, 2001).
Whatever the cause, as the urine accumulates in the renal pelvis, it distends the pelvis and its calyces. In time, atrophy of the kidney results. As one kidney undergoes gradual destruction, the other kidney gradually enlarges (compensatory hypertrophy). Ultimately, renal function is impaired.
The patient may not have symptoms if the onset is gradual. Acute obstruction may produce aching in the flank and back. If infection is present, dysuria, chills, fever, tenderness, and pyuria may occur. Hematuria and pyuria may be present. If both kid-neys are affected, signs and symptoms of chronic renal failure may develop.
The goals of management are to identify and correct the cause of the obstruction, to treat infection, and to restore and conserve renal function. To relieve the obstruction, the urine may have to be diverted by nephrostomy or another type of di-version. The infection is treated with antibiotic agents because residual urine in the calyces leads to infection and pyelonephri-tis. The patient is prepared for surgical removal of obstructive le-sions (calculus, tumor, obstruction of the ureter). If one kidney is severely damaged and its function is destroyed, nephrectomy (removal of the kidney) may be performed.