Urinary Tract Obstruction

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

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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.

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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.

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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.

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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]

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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.

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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.

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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.

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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.

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