Urinary Tract Obstruction 

Updated: Mar 27, 2017
Author: Edward David Kim, MD, FACS; Chief Editor: Bradley Fields Schwartz, DO, FACS 

Overview

Practice Essentials

Urinary tract obstruction is a common problem encountered by urologists, primary care physicians, and emergency medicine physicians. Obstruction can occur at any point in the urinary tract, from the kidneys to the urethral meatus. It can develop secondary to calculi, tumors, strictures, anatomical abnormalities, or functional abnormalities. Obstructive uropathy can result in pain, urinary tract infection, loss in renal function, or, possibly, sepsis or death. Thus, suspected cases of urinary tract obstruction merit consultation with a urologist for evaluation.

Note the computed tomography (CT) image below.

A noncontrast, axial CT image showing right-sided A noncontrast, axial CT image showing right-sided hydronephrosis. In this particular case, the patient had a distal ureteral stricture secondary to prior ureterolithiasis.

History of the Procedure

Use of the urethral catheter to relieve urinary tract obstruction dates back to the time of Hippocrates. The first catheters were made of metal; by the Middle Ages, more flexible catheters were developed. Rubber catheters were developed in the 19th century. Currently, various sizes, compositions (eg, latex, silicone), and tips (coude, straight, council tip) of catheters are available.

Suprapubic access to the bladder can be traced back to the 16th century. It was initially considered a procedure of last resort but was refined in the 20th century. At present, it is a fairly common mode for relief of urinary tract obstruction.

Problem

Urinary tract obstruction impedes urine flow. Subsequent accumulation of urine distends the urinary tract proximal to the point of obstruction and can result in pain, which may be the first symptom of obstruction. Distortion of the urinary tract and acute kidney injury can develop; the severity depends on the degree and duration of obstruction. In addition, urinary stasis in an obstructed urinary tract may predispose to urinary tract infection.

Epidemiology

Frequency

In an autopsy series of 59,064 patients aged 0-80 years, the frequency of hydronephrosis was 3.1%. In women with uterine prolapse, hydronephrosis occurs in approximately 5% with first-degree prolapse and in 40% with third-degree prolapse.

In women, hydronephrosis is more likely develop during the third to seventh decade of life secondary to pregnancy and gynecologic malignancies. In men, hydronephrosis is most likely after age 60 years secondary to prostatic obstruction. Hydronephrosis is found in 2-2.5% of children.

Etiology

Obstruction of urinary flow can occur anywhere from the kidneys to the urethral meatus. Dividing the urinary tract into the upper urinary tract, defined as the kidney and ureter to the hiatus with the bladder, and the lower urinary tract, defined as the bladder and urethra to the urethral meatus, allows for further delineation of the cause of obstruction.

Certain points along the upper urinary tract are more susceptible to obstruction. The 3 points of narrowing along the ureter include the ureteropelvic junction (UPJ), the crossing of the ureter over the area of the pelvic brim (the iliac vessels), and the ureterovesical junction (UVJ).

Obstruction can be extrinsic, from compressive or restrictive force, or intrinsic, from a multitude of factors. The most common causes of intraluminal obstruction are calculi, blood clots, tumors, or sloughed papilla. These obstructions present acutely, leading to severe renal colic with flank pain, hematuria, nausea, vomiting, and fever. Ureteral strictures, which are caused by stone disease, cancer, maldevelopment, or iatrogenic causes such as ureteroscopy, tend to develop over time, causing chronic obstruction and renal atrophy.

Women may have an additional area of ureteral narrowing as the distal ureter crosses posterior to the pelvic blood vessels and the broad ligament in the posterior pelvis. Women can also experience urinary tract obstruction when the ureters become externally compressed by pelvic tumors or by advanced cervical or gynecologic malignancies.

In older women, prolapse of pelvic structures, such as the uterus and bladder, can lead to urinary tract obstruction. In younger women, pregnancy can result in ureteral obstruction from the gravid uterus.[1] Gynecologic malignancies should always be considered when upper tract obstruction is present.

In men, an enlarged prostate (benign prostatic hypertrophy) can cause urinary tract obstruction by obstructing the urethra. Urethral stricture can also lead to urinary tract obstruction.[2, 3]

Other extrinsic causes of ureteral obstruction can occur. Although less common, these can still cause significant obstruction secondary to inhibition of ureteral peristalsis or by applying external pressure to the ureter. Vascular causes such aberrant lower pole renal arteries oriented anterior to the ureter, known as crossing vessels, can apply pressure at the level of the UPJ or proximal ureter and cause obstruction. Abdominal aortic aneurysms and common iliac artery aneurysms can externally compress the ureter along its natural path. Vascular graft placement has been shown to cause hydronephrosis in up to 10-20% of patients from a mechanical obstruction of the ureter; these occasionally resolve spontaneously.[4]

Retroperitoneal fibrosis can trap the ureters in fibrotic tissue, inhibiting peristalsis. This can occur in a unilateral or bilateral fashion and can be caused by a coexistent malignancy in 8-10% of cases.

Persistence of the posterior subcardinal vein in utero may cause obstruction by coursing the ureter behind the inferior vena cava. This is known as a retrocaval ureter and occurs on the right side,  with a male predominance. Obstruction of the ureter typically becomes symptomatic in the third or fourth decade of life.[4]

In children, more common causes of obstruction include the following:

Prenatal screening with ultrasonography is important in early identification of obstruction. In addition, children with incontinence or urinary tract infection need a workup because they may also have some type of urinary tract obstruction.

Pathophysiology

Chronic urinary tract obstruction can lead to permanent damage to the urinary tract. Infravesical obstruction can lead to changes in the bladder, such as trabeculation, cellule formation, diverticula, bladder wall thickening, and, ultimately, detrusor muscle decompensation.

 Progressive back pressure on the ureters and kidneys can occur and can cause hydroureter and hydronephrosis. The ureter can then become dilated and tortuous, with the inability to adequately propel urine forward. Hydronephrosis can cause permanent nephron damage and renal failure. Urinary stasis along any portion of the urinary tract increases the risk of stone formation and infection, and, ultimately, upper urinary tract injury. Urinary tract obstruction can have long-lasting effects on the physiology of the kidney, including its ability to concentrate urine.

In the setting of an acute urinary tract obstruction, an increase in intraluminal pressure causes smooth muscle cells to increase contractions and ureteral wall pressure. As the duration of the obstruction lengthens, smooth muscle cells contract with less force and ureteral wall dilation increases. With a superimposed urinary infection, as often occurs in chronic obstruction, the loss of muscle tone is even more dramatic and progressive dilation occurs with no further increase or decrease in wall tension.[5]

Presentation

The clinical presentation of urinary tract obstruction varies with the location, duration, and degree of obstruction. Thus, a thorough history and physical examination are key in the patient evaluation.

Upper urinary tract obstruction (kidney, ureter) can manifest as pain in the flank, ipsilateral back, and ipsilateral groin. Nausea and vomiting are also common and usually occur in acute obstruction. Chronic obstruction is usually indolent and may be asymptomatic. When infection is present, the patient may experience fever, chills, and dysuria. Hematuria may also be present.

When bilateral obstruction or unilateral obstruction in a solitary kidney is severe and renal failure has occurred, uremia can be present. Uremia symptoms include weakness, peripheral edema, mental status changes, and pallor. If hydronephrosis is severe, the kidney may be palpable on physical examination, especially in children. In cases that involve an infectious process, costovertebral angle tenderness can indicate pyelonephritis.

Lower urinary tract obstruction (bladder, urethra) can manifest as voiding dysfunction such as urgency, frequency, nocturia, incontinence, decreased stream, hesitancy, postvoid dribbling, and a sensation of inadequate emptying. Suprapubic pain or a palpable bladder indicates urinary retention. Infection may be present, and patients may experience dysuria. Hematuria may be present with or without infection.

Digital rectal examination is indicated in men, as it can reveal prostatic enlargement, decreased rectal tone, or prostatitis.[6] Urethral stricture often requires cytoscopy for diagnosis. Meatal stenosis is usually apparent on physical examination. Patients with urethral stricture may report a history of trauma, instrumentation, or sexually transmitted diseases; lower urinary tract pain is common.[7]  They may also experience a split urinary stream. In women, uterine or bladder prolapse can be identified on a pelvic examination. A urethral diverticulum can also be palpated on pelvic examination.

Indications

A patient with complete urinary tract obstruction; any type of obstruction in a solitary kidney; obstruction with fever, infection, or both; or renal failure needs immediate attention by a urologist. Patients with pain that is uncontrolled by oral medications or with persistent nausea and vomiting that causes dehydration also need immediate attention, as well as hospital admission.

Relevant Anatomy

Obstruction to urinary flow can occur anywhere from the kidneys to the urethral meatus. Certain points along this path are more susceptible to obstruction. The 3 points of narrowing along the ureter include the UPJ, the crossing of the ureter over the area of the pelvic brim at the level of the iliac vessels, and the UVJ.

Contraindications

Different procedures carry different relative and absolute contraindications. Prior to any elective surgical intervention, the urine should be sterile and all coagulation parameters should be normal.

In the setting of pelvic trauma with possible urethral disruption, some urologists advocate placement of a suprapubic catheter instead of a Foley catheter because a Foley catheter can worsen the urethral disruption, introduce infection into a pelvic hematoma, and worsen pelvic bleeding.

When dealing with a pregnant woman with an obstructed urinary tract, some urologists place a ureteral stent, while others prefer placement of a percutaneous nephrostomy tube.

When patients have had previous abdominal or pelvic surgery, some urologists may prefer placing an open suprapubic tube instead of a percutaneously placed tube, in order to avoid causing bowel injury.

 

Workup

Laboratory Studies

Urinalysis

Urinalysis can provide useful information in evaluating for infection or hematuria. White blood cells (WBCs) in the urine can indicate infection or inflammation. Nitrite- or leukocyte esterase–positive urine indicates infection.

All urine specimens that contain WBCs or are positive for nitrite or leukocyte esterase should be sent for culture and antibiotic sensitivity testing

Red  blood cells can be present in patients with infection, stones, or tumor. A urologist should evaluate all patients with microscopic or gross hematuria to ensure that malignancy is not present. These patients require urine cytology and a full hematuria workup (cystoscopy, upper urinary tract imaging).

Measurement of urine pH is useful in the evaluation and workup of stones.

Basic metabolic panel

Renal insufficiency is detected on a basic metabolic panel on the basis of elevated blood urea nitrogen (BUN) and creatinine levels. This can result from bilateral renal obstructive processes or obstruction in a solitary kidney.

Other metabolic abnormalities can also be present in renal insufficiency. Hyperkalemia and acidosis may be present.

Complete blood cell count

Leukocytosis indicates infection. Anemia can be due to acute processes (eg, blood loss) or chronic processes (eg, chronic renal insufficiency, malignancy).

Imaging Studies

Ultrasonography

Ultrasonography of the kidneys and bladder is a useful imaging modality as an initial study. It is noninvasive and inexpensive and does not involve radiation exposure or depend on renal function. It is the initial study of choice in pregnant women.

In patients with allergy to intravenous pyelography (IVP) or with elevated creatinine levels, ultrasonography is a very useful source of imaging.

In children, this is often part of the initial workup for obstructive processes.

Ultrasonography is sensitive in revealing renal parenchymal masses, hydronephrosis, a distended bladder, and renal calculi.

The accuracy of this imaging modality depends heavily on the experience of the ultrasonographer.

In adults, if the ultrasonography findings are abnormal in any way, additional imaging is usually recommended. The combination of renal ultrasonography with flat-plate radiography of the kidneys, ureters, and bladder (KUB) is an inexpensive initial combination. See the image below.

Longitudinal image of right kidney displaying mode Longitudinal image of right kidney displaying moderate hydronephrosis.

Computed tomography

A CT scan is very useful in providing anatomic detail and is often a first-line test in the evaluation of a patient. CT provides information regarding the urinary tract, as well as any possible retroperitoneal or pelvic pathologic condition that can affect the urinary tract via direct extension or external compression.

A noncontrast CT scan should be obtained to assess for calculi. If calculi are found, a KUB film should be obtained to help determine calcium content and stone shape and to assist in monitoring the progress of the stone. Its progress can be observed with periodic simple radiography.

A contrast CT scan is needed to provide information on renal pathology.

If delayed contrast images are obtained, CT urography with 3-dimensional reconstruction can provide excellent visualization of the entire upper urinary tracts. A CT scan can be used to identify or rule out any other intra-abdominal processes that can cause presenting symptoms (eg, appendicitis, cholecystitis, diverticulitis, abdominal aneurysms, ovarian cysts).

See the images below.

Axial CT images with intravenous contrast, reveali Axial CT images with intravenous contrast, revealing right-sided hydronephrosis (left image) and an obstructing right ureteropelvic junction stone (right image).
Coronal CT image with intravenous contrast, displa Coronal CT image with intravenous contrast, displaying (left) delayed contrast excretion and bilateral hydronephrosis secondary to (right) bladder outlet obstruction from benign prostatic hyperplasia, and an extremely distended bladder.

Intravenous pyelography

With the advancements in CT urography, IVP is rarely performed. IVP involves the injection of contrast into the venous system and a series of KUB radiographs over time. It can be performed in patients with a normal creatinine value (<1.5 mg/dL) for visualization of the upper urinary tract. It provides both anatomical and functional information. Patients with IVP contrast allergy cannot undergo this test.

Delayed calyceal filling, delayed contrast excretion, prolonged nephrography results, and dilatation of the urinary tract proximal to the point of obstruction characterize obstruction.

If IVP is inadequate, retrograde pyelography can be performed to completely visualize the renal pelvis or ureter.

A combination CT scan and IVP (CT/IVP) test is commonplace. CT urography, as mentioned above, is also an excellent modality.

See the images below.

Intravenous pyelogram, 1-hour delayed image showin Intravenous pyelogram, 1-hour delayed image showing left-sided hydroureteronephrosis secondary to distal ureteral obstruction.
Intravenous pyelogram displaying right-sided urete Intravenous pyelogram displaying right-sided ureteropelvic junction obstruction and normal excretory image of the left collecting system.

Radionucleotide studies

A renal scan can be performed to determine the differential function of the kidneys, as well as to demonstrate the concentrating ability, excretion, and drainage of the urinary tract. Furosemide can be administered with the renal scan to verify delayed excretion and the presence of obstruction.

See the images below.

Mercaptoacetyltriglycine (MAG3) renal scan with fu Mercaptoacetyltriglycine (MAG3) renal scan with furosemide (Lasix); delayed emptying of left-sided collecting system consistent with obstructive hydronephrosis.
Mercaptoacetyltriglycine (MAG3) renal scan with fu Mercaptoacetyltriglycine (MAG3) renal scan with furosemide (Lasix); , delayed emptying of left-sided collecting system consistent with obstructive hydronephrosis.

Magnetic resonance imaging

MRI does not reveal urinary stones well and is not a first-line test used to evaluate the urinary tract. In patients who cannot tolerate a CT scan with contrast, an MRI with gadolinium can be performed to reveal any enhancing renal lesions.

MRI is useful in delineating specific tissue planes for surgical planning, as well as in evaluating the presence or extent of thrombus in a renal vein or the inferior vena cava in cases of renal tumors.

See the images below.

T2-weighted MRI, coronal image, displaying a right T2-weighted MRI, coronal image, displaying a right-sided duplicated system with obstruction of the lower pole moiety.
T2-weighted MRI, coronal image, displaying left-si T2-weighted MRI, coronal image, displaying left-sided ureteropelvic junction obstruction.

Retrograde urethrography

Radiographic dye is injected into the urethral meatus via Foley catheter at the distal urethra. Fluoroscopy is used to visualize the entire urethra for stricture or any abnormalities. This test can be particularly useful in working up lower urinary tract trauma. See the image below.

Retrograde urethrogram displaying complete obstruc Retrograde urethrogram displaying complete obstruction of prostatic urethra.

Retrograde pyelography: See Cystoscopy with retrograde pyelography.

Nephrostography

This can be performed in patients who have a nephrostomy tube in place. Radiographic dye is injected antegrade through the nephrostomy tube. With fluoroscopy, any abnormalities or filling defects in the renal pelvis or ureter are visible. This can be safely performed even in patients with IVP contrast allergies.

Diagnostic Procedures

Cystoscopy

Cystoscopy is the placement of a small camera called a cystoscope through the urethral meatus and passing through the urethra into the bladder (see the image below). Any abnormalities in the urethra, prostatic urethra, bladder neck, and bladder can be visualized. This can be performed in the office or in the operating room.

Cystoscopy with retrograde pyelography

Retrograde pyelography is performed in the operating room with a cystoscope in the bladder. Radiographic dye is injected into each ureteral orifice. Then, with the use of fluoroscopy, any ureteral or renal pelvis filling defects or abnormalities can be visualized. The contrast load does not interfere with renal function and can be used in patients with elevated creatinine levels. It can also be used in patients with an IVP dye allergy because the contrast remains extravascular.

Flexible cystoscope; Gyrus ACMI ICN-2. Flexible cystoscope; Gyrus ACMI ICN-2.

Histologic Findings

When upper urinary tract obstruction occurs, the kidney undergoes interstitial fibrosis, with the accumulation of collagens and other extracellular matrix components.

 

Treatment

Medical Therapy

Consultation with a urologist should be obtained in patients with urinary tract obstruction, as in hydronephrosis or urinary retention. A patient with complete urinary tract obstruction; any type of obstruction in a solitary kidney; obstruction with fever or infection; or renal failure needs immediate attention by a urologist. Patients with pain that is uncontrolled with oral medications or with persistent nausea and vomiting that causes dehydration also need immediate urological attention.

A partial urinary tract obstruction in the absence of infection can be initially managed with analgesics and prophylactic antibiotics until a complete urologic evaluation is performed and definitive management is completed.

Antibiotics are often given for prophylaxis and should cover common urinary tract pathogens. Commonly used antibiotics include trimethoprim-sulfamethoxazole, nitrofurantoin, cephalosporins, and fluoroquinolones.

Pain secondary to urinary tract obstruction is often managed with oxycodone, hydrocodone, acetaminophen, and nonsteroidal anti-inflammatory medications.

Surgical Therapy

The goal of surgical intervention is to completely relieve the urinary tract obstruction. This can be evaluated with reimaging to ensure that the obstruction is resolved, as well as renal function monitoring with a creatinine laboratory test. The recovery of renal function depends on the severity and duration of the obstruction.

Different interventions can be performed to temporarily relieve the point of obstruction. Surgical intervention is usually obtained once the point of obstruction is identified with radiographic imaging.

Lower urinary tract obstruction

Lower urinary tract obstruction (bladder, urethra) can be relieved with a urethral catheter or a suprapubic tube or catheter.

Urethral catheter

:A urethral catheter (size 8F-24F) is a flexible external catheter that extends from the bladder through the urethra. A physician or nurse can place it. If catheter placement is difficult, a urologist may be needed to avoid urethral trauma. The urologist may need to perform urethral dilation, cystoscopy, or both to pass the catheter. The catheter can be left indwelling, or, as an alternative, the patient can perform clean intermittent catheterization. If blood is present at the urethral meatus after pelvic trauma and suspicion of urethral injury exists, a urologist should be consulted prior to catheter placement. Retrograde urethrography needs to be performed to rule out urethral injury.

Suprapubic tube or catheter

If a Foley catheter cannot be passed, a suprapubic tube can be placed percutaneously (at the bedside) or in an open fashion (in the operating room). A suprapubic tube is placed on the lower anterior abdominal wall, approximately 2 finger-breadths above the pubic symphysis. Ultrasound guidance should be used for bedside procedures to ensure proper placement without injury to adjacent structures. In patients with previous abdominal surgery, adhesions and scar tissue may have changed the normal bowel location, so an open approach may be preferred. See the image below.

Cystoscopic image of vapor-resection of an obstruc Cystoscopic image of vapor-resection of an obstructing prostate. Obstructing lateral lobes can be seen proximal to the verumontanum.

Upper urinary tract obstruction

Upper urinary tract obstruction (ureter, kidney) can be relieved with a ureteral stent or a nephrostomy tube

Ureteral stent

A ureteral stent is a flexible tube that extends from the renal pelvis to the bladder (see the image below). It can be placed during cystoscopy to relieve obstruction along any point in the ureter. A ureteral stent generally needs to be changed every 3 months.

Kidney-ureter-bladder (KUB) image displaying a lar Kidney-ureter-bladder (KUB) image displaying a large right-sided renal stone and an indwelling ureteral stent.

Nephrostomy tube

A nephrostomy tube is a flexible tube that is placed through the back directly into the renal pelvis. If a ureteral stent cannot be placed cystoscopically in a retrograde fashion, a percutaneous nephrostomy tube can be inserted for relief of hydronephrosis. If needed, a ureteral stent can then be passed in an antegrade fashion through the nephrostomy tube tract.

Urologic emergencies

The following are urologic emergencies that require immediate attention and intervention:

  • Complete urinary tract obstruction

  • Any type of obstruction in a solitary kidney

  • Obstruction with fever, infection, or both

  • Renal failure

  • Pain that is uncontrolled with oral medications

  • Nausea and vomiting that causes dehydration

Preoperative Details

Before any surgical intervention or any manipulation of the urinary tract, broad-spectrum antibiotics should be initiated to prevent infection or urosepsis. Ideally, before any manipulation is performed, the urine should be sterile. However, this may not be possible in cases of emergent surgical intervention. Urine culture along with the administration of broad-spectrum antibiotics is important.

If cystoscopy and stent are needed emergently, coagulation is not a concern. If percutaneous drainage is necessary, coagulopathies should be corrected.

Intraoperative Details

Different interventions can be performed to temporarily relieve the point of obstruction. If the planned procedure cannot be performed safely or is not adequate in relieving urinary tract obstruction, other modes of urinary tract decompression can be tried.

Postoperative Details

When a patient has long-standing urinary tract obstruction that has been relieved, they may experience postobstructive diuresis.[8] This physiologic diuresis is usually self-limiting and can be managed conservatively with fluid replacement and, if needed, electrolyte replacement. Postobstructive diuresis is defined as diuresis of more than 200 mL/h for at least 2 hours. Patients with severe diuresis should receive intravenous fluid replacement in the form of half normal saline at 80% of the hourly urine volume for the first 24 hours, then 50%. Postobstructive diuresis usually lasts 24-72 hours. Most cases are not severe enough to require this level of attention.

Follow-up

Definitive treatment at the point of obstruction is needed after the acute obstruction is resolved. Adults and children often have different etiologies of urinary tract obstruction. Thus, various definitive surgical treatment options are available for each condition. After definitive treatment is achieved, a final imaging study is obtained to verify complete relief of the obstruction. The type of study performed, as well as the timing of the study, is left to the discretion of the urologist.

For patient education information, see Intravenous Pyelogram, Cystoscopy, Magnetic Resonance Imaging (MRI), and CT Scan.

Complications

A patient with urinary tract obstruction should see a urologist promptly because of the serious complications that the obstruction can impose. The following are complications of obstructive uropathy:

  • Infection, including cystitis (bladder infection), pyelonephritis (kidney infection), abscess formation, and urosepsis

  • Urinary extravasation with urinoma formation

  • Urinary fistula formation

  • Renal insufficiency or failure

  • Bladder dysfunction secondary to a defunctionalized bladder

  • Pain

Outcome and Prognosis

The prognosis of urinary tract obstruction depends on the cause, location, degree, and duration of obstruction, as well as the presence of a urinary tract infection. The longer the duration of obstruction, the greater the severity of obstruction, and the presence of a concomitant infection can lead to a worse prognosis. The prognosis is favorable if the renal function is normal, the infection is cleared, and the obstruction is relieved in a timely manner.

Future and Controversies

As time goes on, new procedures emerge and old procedures are modified to relieve urinary tract obstruction. In addition, with newer cameras and equipment and the use of laparoscopy, surgical intervention is becoming more advanced.