Hydronephrosis

Hydronephrosis is a condition in which the kidney swells, due to a backup of urine. Hydronephrosis generally occurs with another disease such as acute or chronic unilateral obstructive uropathy, vesicoureteric reflux, kidney stones, and during pregnancy. 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
Classification and external resources
Specimen of a kidney that has undergone extensive dilation due to hydronephrosis. Note the extensive atrophy and thinning of the renal cortex.
ICD-10	N13.0-N13.3
ICD-9	591
DiseasesDB	6145
MeSH	D006869

Hydronephrosis is distension and dilation of the renal pelvis and calyces, usually caused byobstruction of the free flow of urine from the kidney, leading to progressive atrophy of the kidney.^[1] In case of hydroureteronephrosis, there is distention of both the ureter and the renal pelvis and calices.^[2]

Contents  [hide] 1 Signs and symptoms 2 Aetiology 3 Tests 4 Prognosis 5 Treatment 6 References 7 External links

[edit]Signs and symptoms

The signs and symptoms of hydronephrosis depend upon whether the obstruction is acute orchronic, partial or complete, unilateral or bilateral. Unilateral hydronephrosis may occur without any symptoms, while acute obstruction can cause intense pain.^[1]

Blood tests can show raised creatinine, urea and electrolyte imbalance. Urinalysis may show an elevated pH due to the secondary destruction of nephrons within the affected kidney.

Symptoms that occur regardless of where the obstruction lies include loin or flank pain. An enlarged kidney may be palpable on examination.

Where the obstruction occurs in the lower urinary tract, suprapubic tenderness (with or without a history of bladder outflow obstruction) along with a palpable bladder are strongly suggestive ofacute urinary retention, which left untreated is highly likely to cause hydronephrosis.

Upper urinary tract obstruction is characterised by pain in the flank, often radiating to either theabdomen or the groin. Where the obstruction is chronic, renal failure may also be present. If the obstruction is complete, an enlarged kidney is often palpable on examination.

[edit]Aetiology

The obstruction may be either partial or complete and can occur anywhere from the urethral meatus to the calyces of the renal pelvis.

The obstruction may arise from either inside or outside the urinary tract or may come from the wall of the urinary tract itself. Intrinsic obstructions (those that occur within the tract) include blood clots, stones, sloughed papilla along with tumors of the kidney, ureter and bladder. Extrinsic obstructions (those that are caused by factors outside of the urinary tract) include pelvic or abdominal tumours or masses, retroperitoneal fibrosis or neurological deficits. Strictures of the ureters (congenital or acquired), neuromuscular dysfunctions or schistosomiasis are other causes which originate from the wall of the urinary tract.

Hardikar syndrome can include Hydronephrosis, Cleft lip and palate, Vesicoureteral reflux, Intestinal obstruction, Obstructive liver disease and other symptoms. ^[3]

[edit]Tests

Ultrasound picture of hydronephrosis caused by a left ureteral stone.

Prenatal diagnosis is possible.^[4]

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.

[edit]Prognosis

Left untreated, bilateral obstruction (occurring to both kidneys rather than one) has a poor prognosis.

[edit]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

Hydronephrosis Buy the Book Print This Topic Email This Topic Pronunciations creatinine hydronephrosis intravenous urography lithotripsy ostomy peristalsis prostate ultrasonography ureter urethra uterus Hydronephrosis is distention (dilation) of the kidney with urine, caused by backward pressure on the kidney when the flow of urine is obstructed. Kidney stones are common causes of urinary tract obstruction. When hydronephrosis occurs quickly, people may have excruciating pain, most often in the flank (the area between the ribs and the hips). When hydronephrosis occurs more gradually, people may have no symptoms or experience attacks of dull, aching discomfort in the flank. Doctors initially use bladder catheterization (or ultrasonography) to detect hydronephrosis, and they may use ultrasonography or another imaging test to determine the site of the blockage. Treatment depends on the cause of the obstruction. Hydronephrosis: A Distended Kidney In hydronephrosis, the kidney is distended because the flow of urine is obstructed and urine backs up in the kidney's small tubes and central collecting area (renal pelvis). Normally, urine flows out of the kidneys at extremely low pressure. If the flow of urine is obstructed, urine backs up behind the point of blockage, eventually reaching the small tubes of the kidney and its collecting area (renal pelvis), distending the kidney and increasing the pressure on its internal structures. The elevated pressure from obstruction may ultimately damage the kidney and can result in loss of its function. When the flow of urine is obstructed, urinary tract infections are fairly common and stones are more likely to form. If both kidneys are obstructed, kidney failure may result. Long-standing distention of the renal pelvis and ureter can also inhibit the rhythmic muscular contractions that normally move urine down the ureter from the kidney to the bladder (peristalsis). Scar tissue may then replace the normal muscular tissue in the walls of the ureter, resulting in permanent damage. Causes Hydronephrosis commonly results from an obstruction located at the junction of the ureter and renal pelvis (ureteropelvic junction). Causes of this type of obstruction include the following: Structural abnormalities—for example, a birth defect in which the insertion of the ureter into the renal pelvis is too high or there is inadequate development of the ureteral muscles (congenital ureteropelvic junction obstruction) Kinking at the ureteropelvic junction resulting from a kidney shifting downward (ptosis of the kidney) Stones (calculi) or a blood clot in the renal pelvis Compression of the ureter by bands of fibrous tissue, an abnormally located artery or vein, or a tumor Hydronephrosis can also result from an obstruction below the ureteropelvic junction or from backflow (reflux) of urine from the bladder. Causes of this type of obstruction include the following: Stones in the ureter Blood clot in the ureter Tumors in or near the ureter Narrowing of the ureter resulting from a birth defect, an injury, an infection, radiation therapy, or surgery Disorders of the muscles or nerves in the ureter or bladder Formation of fibrous tissue in or around the ureter resulting from surgery, radiation therapy, or drugs (especially methysergide) Bulging of the lower end of the ureter into the bladder (ureterocele) Cancers of the bladder, cervix, uterus, prostate, or other pelvic organs Obstruction that prevents urine flow from the bladder to the urethra, resulting from prostate enlargement (most often caused by a condition called benign prostatic hyperplasia—see Prostate Disorders: Benign Prostatic Hyperplasia (BPH)), or rectal impaction with feces Abnormal contractions of the bladder resulting from a birth defect or a spinal cord or nerve injury Hydronephrosis of both kidneys can occur during pregnancy as the enlarging uterus compresses the ureters. Hormonal changes during pregnancy may aggravate the problem by reducing the muscular contractions that normally move urine down the ureters. This condition, commonly called hydronephrosis of pregnancy, usually ends when the pregnancy ends, although the renal pelvis and ureters may remain somewhat distended afterward. Symptoms Symptoms depend on the cause, location, and duration of the obstruction. When the obstruction begins quickly (acute hydronephrosis), it usually produces renal colic—an excruciating, intermittent pain in the flank (the area between the ribs and hip) on the affected side. Obstruction on one side does not reduce urine flow. Obstruction can stop or reduce urine flow if blockage affects the ureters from both kidneys or if it affects the urethra. Obstruction of the urethra or bladder outlet may produce pain, pressure, and distention of the bladder. People who have slowly progressive (chronic) hydronephrosis may have no symptoms, or they may have attacks of dull, aching discomfort in the flank on the affected side. Sometimes a kidney stone temporarily blocks the ureter and produces painful hydronephrosis that occurs intermittently. Hydronephrosis may cause vague intestinal symptoms, such as nausea, vomiting, and abdominal pain. These symptoms sometimes occur in children when hydronephrosis results from a birth defect in which the junction of the ureter and renal pelvis is too narrow (ureteropelvic junction obstruction). People who have urinary tract infections may have pus in the urine, fever, and discomfort in the area of the bladder or kidneys. Diagnosis Early diagnosis is important, because most cases of obstruction can be corrected and because a delay in treatment can lead to irreversible kidney damage. Doctors may suspect hydronephrosis because of a person's symptoms and sometimes because of findings discovered during a physical examination. A distended kidney can occasionally be felt in the flank, particularly if the kidney is greatly enlarged in an infant or a child or a thin adult. A distended bladder can sometimes be felt in the lower part of the abdomen just above the pubic bone. Doctors depend on testing to make the diagnosis. Bladder catheterization (insertion of a hollow, flexible tube through the urethra) is often the first diagnostic test done in people with renal colic, pelvic pressure, or distention. If the catheter drains a large amount of urine from the bladder, then either the bladder outlet or the urethra is obstructed. Many doctors do ultrasonography to determine whether the bladder is filled with a large amount of urine before doing bladder catheterization. If the presence or site of obstruction is in doubt, various imaging tests can be done to identify evidence of obstruction such as hydronephrosis or a site of blockage. For example, ultrasonography is a very useful test in most people (particularly children and pregnant women) because it is fairly accurate and does not expose the person to any radiation. Computed tomography (CT) scanning is an alternative. It is rapid and highly accurate, particularly at identifying stones. Other imaging tests, such as intravenous urography, may be performed to identify the site of obstruction, if it is not visible with ultrasonography or CT. An endoscope (a rigid or flexible telescope) is sometimes used to look at possible sites of obstruction as closely as possible. An endoscope can be used to examine the urinary tract. Blood and urine tests are done. Blood test results are usually normal, but tests may reveal high levels of urea nitrogen (sometimes called BUN), creatinine, or both, if obstruction affects both kidneys. Results from an analysis of urine (urinalysis) are usually normal but white blood cells and red blood cells may be present when a stone or a cancer is the cause of obstruction, or when the obstruction is complicated by an infection. Prognosis Permanent kidney damage is unlikely to result unless both kidneys are obstructed for at least a few weeks. The prognosis is less certain for chronic hydronephrosis. Treatment Treatment usually aims to relieve the cause of obstruction. For example, if the urethra is obstructed because of an enlarged or cancerous prostate, treatment can include drugs, such as hormone therapy for prostate cancer (see Prostate Disorders: Prostate Cancer), surgery, or enlargement of the urethra with dilators. Other treatments, such as lithotripsy or endoscopic surgery, may be needed for stones that block the flow of urine. If the cause of obstruction cannot be rapidly corrected, particularly if there is infection, kidney failure, or severe pain, the urinary tract is drained. In acute hydronephrosis, urine that has accumulated above the obstruction can be drained with a soft tube inserted through the skin into the kidney (nephrostomy tube) or by insertion of a soft plastic tube that connects the bladder with the kidney (ureteral stent). Complications of nephrostomy tubes or ureteral stents can include displacement of the tube, infection, and discomfort. Urgent relief of chronic hydronephrosis is usually not required. Complications of hydronephrosis, such as urinary tract infections and kidney failure, if present, are treated promptly. Last full review/revision August 2007 by Glenn M. Preminger, MD