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Urinary Tract Obstruction Workup

  • Author: Edward David Kim, MD, FACS; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
 
Updated: Nov 14, 2014
 

Laboratory Studies

Urinalysis

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

All urine that contains WBCs or is positive for nitrite or leukocyte esterase should be sent for culture analysis and antibiotic susceptibility.

RBCs in the urine can be present in 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).

Urine pH is useful in the evaluation and workup of stones.

Basic metabolic panel

Renal insufficiency is detected on a basic metabolic panel based on elevated 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).

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Imaging Studies

Ultrasonography

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

In patients with intravenous pyelography (IVP) dye allergies or 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 scan

A CT scan is very useful in providing anatomic detail and is often a first-line test in the evaluation of a patient.

A CT scan 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, flat-plate radiography of the abdomen (KUB) 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 contrasted 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.

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.

Patients with IVP contrast allergy cannot undergo this test.

A combination CT scan and IVP (CT/IVP) test is commonplace. With this combined technique, both modalities can be used. 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. Lasix 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 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 a renal vein or inferior vena cava thrombus in cases of renal tumors.

MRI does not reveal urinary stones well so is not often used as a first-line test.

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.

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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.
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Histologic Findings

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

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Staging

No staging system exists for urinary tract obstruction.

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Contributor Information and Disclosures
Author

Edward David Kim, MD, FACS Professor of Surgery, Division of Urology, University of Tennessee Graduate School of Medicine; Consulting Staff, University of Tennessee Medical Center

Edward David Kim, MD, FACS is a member of the following medical societies: American College of Surgeons, Tennessee Medical Association, Sexual Medicine Society of North America, American Society for Reproductive Medicine, American Society of Andrology, American Urological Association

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Repros.

Coauthor(s)

Suzette E Sutherland, MD Adjunct Associate Professor, Department of Urologic Surgery, University of Minnesota Medical School; Metro Urology, Centers for Continence Care and Female Urology

Suzette E Sutherland, MD is a member of the following medical societies: Alpha Omega Alpha, American Medical Association, American Urological Association, Minnesota Medical Association, International Continence Society, International Society for Sexual Medicine

Disclosure: Nothing to disclose.

Yvonne Katherine P Koch, MD Staff Physician, Department of Urology, Case Western Reserve University, University Hospitals of Cleveland

Yvonne Katherine P Koch, MD is a member of the following medical societies: American Urological Association, Endourological Society

Disclosure: Nothing to disclose.

James M Bienvenu, MD Resident Physician, Department of Urology, University of Tennessee Health Science Center College of Medicine

James M Bienvenu, MD is a member of the following medical societies: American College of Surgeons, American Urological Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Bradley Fields Schwartz, DO, FACS Professor of Urology, Director, Center for Laparoscopy and Endourology, Department of Surgery, Southern Illinois University School of Medicine

Bradley Fields Schwartz, DO, FACS is a member of the following medical societies: American College of Surgeons, Society of Laparoendoscopic Surgeons, Society of University Urologists, Association of Military Osteopathic Physicians and Surgeons, American Urological Association, Endourological Society

Disclosure: Nothing to disclose.

References
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Longitudinal image of right kidney displaying moderate hydronephrosis.
A noncontrast, axial CT image showing right-sided hydronephrosis. In this particular case, the patient had a distal ureteral stricture secondary to prior ureterolithiasis.
Flexible cystoscope; Gyrus ACMI ICN-2.
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, displaying (left) delayed contrast excretion and bilateral hydronephrosis secondary to (right) bladder outlet obstruction from benign prostatic hyperplasia, and an extremely distended bladder.
Intravenous pyelogram, 1-hour delayed image showing left-sided hydroureteronephrosis secondary to distal ureteral obstruction.
Intravenous pyelogram displaying right-sided ureteropelvic junction obstruction and normal excretory image of the left collecting system.
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-sided ureteropelvic junction obstruction.
Mercaptoacetyltriglycine (MAG3) renal scan with furosemide (Lasix); delayed emptying of left-sided collecting system consistent with obstructive hydronephrosis.
Mercaptoacetyltriglycine (MAG3) renal scan with furosemide (Lasix); , delayed emptying of left-sided collecting system consistent with obstructive hydronephrosis.
Retrograde urethrogram displaying complete obstruction of prostatic urethra.
Cystoscopic image of vapor-resection of an obstructing prostate. Obstructing lateral lobes can be seen proximal to the verumontanum.
Kidney-ureter-bladder (KUB) image displaying a large right-sided renal stone and an indwelling ureteral stent.
 
 
 
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