Hydronephrosis

    Hydronephrosis is a condition in which the kidney swells, due to a backup of urine. Hydronephrosis generally occurs with another disease.Symptoms of hydronephrosis include nausea, vomiting, urinary tract infection, fever, painful urination, increased urinary frequency and urgency, flank pain, and swelling of the abdomen. Treatment of hydronephrosis depends on the cause.
Hydronephrosis is distension and dilation of the renal pelvis calyces, usually caused by obstruction of the free flow of urine from the kidney, leading to progressive atrophy of the kidney.In case of hydroureteronephrosis, there is distention of both the ureter and the renal pelvis and calices.
Signs and symptoms
The signs and symptoms of hydronephrosis depend upon whether the obstruction is acute or chronic, partial or complete, unilateral or bilateral. Hydronephrosis that occurs acutely with sudden onset (as caused by a kidney stone) can cause intense pain in the flank area (between the hips and ribs), while a chronic occurrence that develops gradually will present with no pain or attacks of a dull discomfort. Nausea and vomiting may also occur. An obstruction that occurs at the urethra or bladder outlet can cause pain and pressure resulting from distension of the bladder. Blocking the flow of urine will commonly result in urinary tract infections which can lead to the development of additional stones, fever, and blood or pus in the urine. If complete obstruction occurs, kidney failure may follow.
Blood tests can show raised creatinine, urea and electrolyte imbalance. A urine test may show an elevated pH due to the secondary destruction of nephrons within the affected kidney. An enlarged kidney may be palpable upon examination.
Causes and Risk Factors
Hydronephrosis is the result of several abnormal pathophysiological occurrences. Structural abnormalities of the junctions between the kidney, ureter, and bladder that lead to hydronephrosis can occur during fetal development. Some of these congenital defects have been identified as inherited conditions, however the benefits of linking genetic testing to early diagnosis have not been determined. [4] Other structural abnormalities could be caused by injury, surgery, or radiation therapy.
Compression of one or both ureters can also be caused by other developmental defects not completely occurring during the fetal stage such as an abnormally placed vein, artery, or tumor. Bilateral compression of the ureters can occur during pregnancy due to enlargement of the uterus. Changes in hormone levels during this time may also affect the muscle contractions of the bladder, further complicating this condition.
Sources of obstruction that can arise from other various causes include kidney stones and blood clots.
The obstruction may be either partial or complete and can occur anywhere from the urethral meatus to the calyces of the renal pelvis.
Hydronephrosis can also result from the reverse flow of urine from the bladder back into the kidneys. This reflux can be caused by some of the factors listed above as well as compression of the bladder outlet into the urethra by prostatic enlargement or impaction of feces in the colon, as well as abnormal contractions of bladder muscles resulting from neurological dysfunction or other muscular disorders. [3]
Pathophysiology
Obstruction that occurs anywhere along the upper urinary tract will lead to increased pressure within the structures of the kidney due to the inability to pass urine from the kidney to the bladder. Obstruction occurring in the lower urinary tract can cause this increased pressure through the reflux of urine into the kidney. All of these factors will lead to the destruction of the delicate tissues that make up the filtration system within the kidneys, which could eventually result in infection, stone formation, or loss of function. Additional complications arising from obstruction of the lower urinary tract include the stagnation of urine flow which can also lead to infection in the bladder.
Tests
Ultrasound picture of hydronephrosis caused by a left ureteral stone.
Prenatal diagnosis is possible.
Blood (U&E, creatinine) and urine (MSU, pH) tests should be taken. IVUs, ultrasounds, CTs and MRIs are also important tests. Ultrasound allows for visualisation of the ureters and kidneys and can be used to assess the presence of hydronephrosis and / or hydroureter. An IVU is useful for assessing the position of the obstruction. Antegrade or retrograde pyelography will show similar findings to an IVU but offer a therapeutic option as well.
The choice of imaging depends on the clinical presentation (history, symptoms and examination findings). In the case of renal colic (one sided loin pain usually accompanied by a trace of blood in the urine) the initial investigation is usually a spiral or helical CT scan. This has the advantage of showing whether there is any obstruction of flow of urine causing hydronephrosis as well as demonstrating the function of the other kidney. Many stones are not visible on plain X-ray or IVU but 99% of stones are visible on CT and therefore CT is becoming a common choice of initial investigation. CT is not used however, when there is a reason to avoid radiation exposure, e.g. in pregnancy.
Treatment
Treatment of hydronephrosis focuses upon the removal of the obstruction and drainage of the urine that has accumulated behind the obstruction. Therefore, the specific treatment depends upon where the obstruction lies, and whether it is acute or chronic.
Acute obstruction of the upper urinary tract is usually treated by the insertion of a nephrostomy tube. Chronic upper urinary tract obstruction is treated by the insertion of a ureteric stent or a pyeloplasty.
Lower urinary tract obstruction (such as that caused by bladder outflow obstruction secondary to prostatic hypertrophy) is usually treated by insertion of a urinary catheter or a suprapubic catheter.
Surgery is not required in all cases