Hydronephrosis is an abnormality that occurs with a disease, and is not a disease itself. It is swelling of one kidney due to a backup of urine.
Hydronephrosis is the most common abnormality reported on prenatal sonographic screening. The vast majority of cases are mild, so-called physiologic hydronephrosis, which are of no clinical significance. Numerous theories have been proposed to try to account for this common finding. In the past, one popular theory was that mild fetal hydronephrosis resulted from changes in maternal hydration.
Maternal hydronephrosis commonly occurs during pregnancy because of the influence of progesterone, a known smooth muscle relaxant. It has been suggested that maternal progesterone may also be responsible for mild fetal upper urinary tract dilatation.
A hydronephrosis may be obstructive or non-obstructive.
A ureter may be obstructed in four different ways:
- A mass within the lumen: A ureteral stone, a blood clot, a sloughed necrotic papilla may all get struck within the ureter, and cause obstruction.
- Narrowing of the wall: A structure may result from previous surgery such as ureteroscopy, or damage at open dissections. Fibrous narrowing is seen following renal tuberculosis and schistosomiasis. A tumor may result into stenosis. Failure of relaxation of the muscle along the pelviureteric junction leads to classical obstruction.
- Pressure from outside compressing the ureter: Metastatic lymph nodes or retroperitoneal fibrosis will cause a slow compression of the ureter.
- A mass at the end of the ureter obstructing outflow of urine: A bladder carcinoma or prostate carcinoma can invade the bladder wall, and constrict the ureteric orifice. In women, carcinoma of the cervix can cause a similar effect. A chronically distended bladder can cause back pressure and hydronephrosis.
A dilated renal pelvis and ureter may be chronically distended rather than obstructed; for example, reflux may produce a distended system.
Any type of obstructive uropathy can lead to this condition. The most common complication of an obstructed kidney is life-threatening infection, caused by urinary stasis that exacerbates renal damage. If it results from acute obstructive uropathy, the patient may develop paralytic ileus. Untreated bilateral hydronephrosis can lead to renal failure, a life-threatening condition.
The patient’s history and reason for seeking care will vary, depending on the cause of the obstruction. For example, a patient may have no symptoms, or complain of only mild pain, and slightly decreased urine flow.
The diagnosis of hydronephrosis is certain and easy, only when subsidence of the tumor occurs simultaneously with a sudden excessive discharge of urine, or when history of such an occurrence can be obtained. When the symptom is absent, the recognition of the disease depends on the ascertainment of the existence of a fluctuating renal tumor, and the absence of the signs of suppuration.
Hydronephrotic tumors have most frequently been confounded with ovarian cysts, ascites, and hydatid cysts. From an ovarian cyst, hydronephrosis is distinguished by the presence of the colon in front of the swelling, and by the absence of a bowel sound on percussion in the corresponding lumbar region. Ascites is distinguished, when the hydronephrosis is single, by the existence of dullness in both blanks, but when the renal tumor is double, and both flanks are consequently dull as in ascites, the latter is recognized by the change of level assumed by the fluid when the posture of the patient is altered.
If the disease be unilateral, and inferred to depend on the impaction of a calculus in the ureter, precautions should be taken against a similar occurrence taking place on the opposite side. The patient should be directed to keep the urine adequately diluted by systematic potation, especially at the time of going to bed.
Disclaimer: This article is for informative purposes only, and should not be used as a replacement for expert medical advice.