Close
New

Medscape is available in 5 Language Editions – Choose your Edition here.

 

Kidneys, Ureters, and Bladder Imaging

  • Author: Paul G Schmitz, MD, DPharm, FACP, CSH; Chief Editor: Caroline R Taylor, MD  more...
 
Updated: Aug 27, 2015
 

Overview

Various imaging studies are available to evaluate patients with suspected renal or urinary tract disease, including the following:[1]

  • Plain films of the abdomen
  • Renal ultrasonography
  • Intravenous pyelography
  • Computed tomography
  • Magnetic resonance imaging
  • Radionuclide scanning
  • Renal angiography
  • Retrograde pyelography
  • Diuretic renography

Common uses and limitations of each of these imaging modalities are discussed below.

Next

Plain Films of the Abdomen

Plain films of the abdomen are now rarely used to evaluate kidney and urinary tract disease. If obtained, plain films may reveal radiopaque kidney stones (usually calcium-containing stones but also struvite and cystine). An advantage of the plain film is that it can be performed in pregnant and pediatric patients, since the amount of radiation exposure is limited.

Plain film of the abdomen revealing a radiopaque s Plain film of the abdomen revealing a radiopaque staghorn calculus involving the entire pelvicalyceal system of the right kidney (arrows). This stone was composed of magnesium ammonium phosphate (struvite). Surgical excision, antimicrobial treatment, and consumption of 4-5 L/d of water are all required to treat and prevent this type of stone.

The sensitivity and specificity of plain abdominal films in detecting a stone is low in patients with renal colic and no history of kidney stones.[1] However, plain films can be used for follow-up of stone clearance, growth, or recurrence after operative or conservative treatment of stones.

It is difficult to distinguish vascular calcifications from ureteral calcifications with plain radiography. Owing to its higher sensitivity, CT imaging has replaced plain films for the diagnosis of urolithiasis and nephrolithiasis.[2]

Plain films are not sensitive enough to exclude tumors of the kidney or urothelial tract. This imaging technique does provide general information regarding kidney size and shape.

Indications

Plain abdominal films are indicated for the evaluation of radiopaque kidney stones (calcium-containing stones, struvite, cystine).

Previous
Next

Renal Ultrasonography

Renal ultrasonography is invaluable as a screening test for urinary tract dilatation (hydronephrosis), a hallmark of urinary tract obstruction. However, dilation of the urinary tract may also be observed in polyuria and normal pregnancy (uterine enlargement causes partial urinary tract obstruction). Urinary tract dilation may persist indefinitely, even after relief of urinary tract obstruction. Parapelvic cysts may also be mistaken for pelvocaliectasis.

Sonogram revealing a dilated collecting system cau Sonogram revealing a dilated collecting system caused by an enlarged lymph node in a patient with B-cell lymphoma.

Ultrasonography remains the procedure of choice for evaluation of acquired or hereditary polycystic kidney disease. Renal masses are also readily identified with ultrasonography.[3] Advanced kidney disease is usually accompanied by scarring and thinning of the renal cortex with small kidneys (< 9 cm in longitudinal length). These features are easily characterized with renal ultrasonography.[4, 5]

Numerous cystic structures are evident on the rena Numerous cystic structures are evident on the renal sonogram.

Although renal ultrasonography was once routinely used to identify kidney stones, noncontrast helical computed tomography has supplanted ultrasonography in the diagnosis of nephrolithiasis.

Color-Doppler ultrasonography is used to measure flow or velocity of blood in the main renal artery. It is primarily used to detect renal vascular occlusive disease.[6] Color-Doppler flow studies in the renal artery are highly operator-dependent.

Indications

Indications of renal ultrasonography are as follows:[1]

  • Evaluation of cystic kidney disease
  • Diagnosis of hydronephrosis
  • Measurement of kidney size and echogenicity as part of an evaluation of chronic kidney disease
  • Detection of renal artery occlusive disease via Doppler images
  • No exposure to radiation or contrast in pregnancy

Limitations

Limitations of renal ultrasonography are as follows:

  • Interpretation is operator-dependent
  • Large body habitus renders the interpretation difficult
Previous
Next

Intravenous Pyelography

Intravenous pyelography (IVP) was the earliest imaging technique to define the anatomy of the renal and urinary tract using iodinated contrast injection, which is excreted by the kidneys into the collecting system. IVP can be used to detect kidney stones and delineate the level of obstruction in patients with urinary tract obstruction. The acquisition of data is slower than other forms of imaging (eg, CT scanning). In pregnant patients, IVP with limited contrast can be performed if ultrasonography is unrevealing. IVP is an excellent modality to diagnose medullary sponge kidney and papillary necrosis.

Intravenous pyelogram in a patient with medullary Intravenous pyelogram in a patient with medullary sponge kidney. Note the brushlike pattern (arrows) involving the renal papillae. This pattern is consistent with numerous ectatic medullary collecting ducts and is pathognomonic for medullary sponge kidney.

Indications:

Indications of IVP are as follows:

  • Delineation of the gross anatomy of the renal and urinary tract
  • Evaluation of medullary sponge kidney and papillary necrosis

Limitations

Avoid IVP in patients with allergy to iodine contrast dye and in patients with impaired renal function (generally a serum creatinine level >2 mg/dL).

Previous
Next

Computed Tomography

Computed tomography (CT) provides similar information as renal ultrasonography but with additional detail due to high spatial resolution. CT scan is an excellent tool to evaluate masses, traumatic injury to the kidney, stones, and pyelonephritis.

CT scan reveals an enormous, contrast-enhanced mas CT scan reveals an enormous, contrast-enhanced mass in the right kidney of a patient with Wilms tumor. The mass consists of several hypodense areas most likely reflecting necrosis or hemorrhage.

Noncontrast helical CT scanning is the procedure of choice to evaluate kidney stones.[7] CT scanning is also used to differentiate malignant from nonmalignant renal masses.[3] Moreover, CT scanning is essential to evaluate the local spread of a renal malignancy. High-resolution CT angiography is excellent in defining the anatomy of the renal arteries and veins (eg, renal vein thrombosis).

Helical CT scanning in a patient with hematuria. N Helical CT scanning in a patient with hematuria. Nonenhanced CT image shows bilateral renal calculi (arrows). This imaging technique is considered the reference standard for stone evaluation.

CT scanning is superior to ultrasonography in identifying renal cysts, since it is capable of detecting small cysts (2-3 mm in diameter).

Because of safety and cost, renal ultrasonography is still used to screen for polycystic kidney disease.

Computed tomography scan of autosomal-recessive po Computed tomography scan of autosomal-recessive polycystic kidney disease revealing many small cysts. Note the small cyst in the head of the pancreas (arrow). RK = right kidney.

With the advent of multidetector CT scanning, CT urography is a feasible option to replace intravenous urography.

Multiphase CT urography[8] has a higher diagnostic yield in evaluating the etiology of hematuria and identifying urothelial tumors than intravenous urography. Some investigators believe it is comparable to cystoscopy and provides complementary data by simultaneously delineating extraurinary disease.

Indications

Indications of CT scanning are as follows:

  • Criterion standard for diagnosing nephrolithiasis
  • Evaluating kidney masses and staging renal tumors
  • Evaluating polycystic kidney disease

Limitations

The primary limitation of CT scanning is the risk of radiation and administration of contrast.

Technique

In the precontrast phase, a scan is obtained for baseline calcifications, stones, and space-occupying lesions in the kidney and urinary tract.

Within 70 seconds after injection of contrast, the renal vasculature is identified and renal cell carcinoma can be accurately staged.

In the nephrographic phase (ie, up to 180 seconds after contrast injection), renal masses can be differentiated from simple cysts, as malignant masses will enhance with contrast.

In the excretory phase (5 minutes after contrast injection), the ureter, bladder and pelvicaliceal system is imaged.

Limited CT urography (with an excretory phase only) can be performed to minimize radiation exposure.

Contraindications

Contrast should be avoided if the patient is allergic, has renal failure, or is pregnant.

Equipment

A multidetector CT scan with 4-64 sections is used.

Patient preparation

No preparation is required, but prehydration is typically performed, and the bladder should be empty before the procedure is begun. Intravenous saline administration or administration of 10 mg of intravenous furosemide is often used to increase opacification and distension of the collecting system.

Position of patient

The supine position seems to be satisfactory in most patients, but the prone position improves opacification of the distal urinary tract in some patients. Turning the patient several times prior to the excretory phase is necessary to prevent layering of contrast.

Previous
Next

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) provides a useful alternative to CT scanning in individuals at risk for toxicity from intravenous contrast. It may also offer an advantage in the evaluation of small renal masses. Magnetic resonance angiography has proven useful in the evaluation of stenosis in the mid and proximal renal arteries.

Recently, progressive systemic fibrosis (nephrogenic systemic fibrosis [NSF]) in patients with kidney failure has been recognized. This disorder has been reported only in patients receiving gadolinium, a contrast agent used to enhance the standard MRI. Although rare, these cases invariably progressed to death. To date, all of these cases have occurred in patients with advanced renal disease. Therefore, MRI with gadolinium contrast is typically avoided in patients with a serum creatinine level exceeding 2 mg/dL (estimated glomerular filtration rate [eGFR] < 30 mL/min), unless deemed urgent, and postexamination dialysis may be indicated in selected cases. Newer contrast agents at very low doses are under investigation as an alternate approach.

Newer modalities, such as magnetic resonance renography, have shown promising results in assessing morphology and function of the kidneys;[9] however, the risk of gadolinium contrast remains a significant concern in patients with renal insufficiency. Several recent studies of non–contrast-enhanced magnetic resonance angiography have revealed excellent sensitivity in detecting renal artery stenosis;[10] however, larger studies are needed before this approach can be recommended routinely in the evaluation of renal artery disease. Magnetic resonance urography is commonly used in children and pregnant women to avoid the risk of ionizing radiation.

Indications

Indications of MRI are as follows:

  • Detailed assessment of the kidney anatomy
  • Noninvasive assessment of kidney function
  • Estimation of GFR [11]
  • Magnetic resonance renography [12]
  • Assessment of congenital anomalies of the kidney, bladder, and urinary tract

Technique

T2-weighted magnetic resonance techniques rely on high signal intensity of urine for image contrast. Images can be obtained quickly and in any image plane. The images are appealing when compared to intravenous urography.

The signal-to-noise ratio (SNR) is increased with phased-array surface coils to achieve maximal interpretable resolution. A further increase in SNR is achieved by imaging with higher field strength; however, this also increases susceptibility artifacts from gas-filled bowel, and this technique therefore needs further investigation.

Magnetic resonance urography can be complemented with T2 weighting and excretory images after administration of intravenous gadolinium. Multiple acquisitions of static fluid MRIs can ensure adequate visualization of the entire ureter and assess fixed narrowing or obstruction.

When contrast is used for magnetic resonance urography, T1-weighted images are used to examine the kidney and vasculature. Intravenous furosemide is used to augment visualization of the excretory system. T1-weighted images are obtained to visualize the bladder for tumors before gadolinium reaches the bladder, as masses can be obscured because of heterogeneous enhancement.

Limitations

The image quality is less robust with an undistended urinary system. Several interventions such as intravenous fluids, diuretics, compression devices, and gadolinium chelate aid in improving the resolution of MRI. Respiratory and ureteral peristaltic movements may interfere with signal acquisition; however, forced breath-holding may improve the image.

A higher degree of patient cooperation and radiologist supervision is required.

MRI is not very sensitive for detecting calcifications, although renal calculi can be inferred from filling defects or ureteral dilatation.

The sensitivity of MRI in detecting urothelial and kidney malignancies is less well known than CT imaging.

Previous
Next

Radionuclide Scanning

Radionuclide scanning has been successfully used to evaluate renal perfusion in various settings, including renal artery stenosis and thrombosis. Although a radionuclide study can provide an assessment of renal tubular function, it is nonspecific and therefore cannot establish a definitive renal diagnosis. Radionuclide cystography is widely used by pediatric nephrologists to detect early vesicoureteral reflux in children.[13]

Technique

Differential renal function can be estimated from the uptake and clearance of tracer by each kidney over a specified period; 99mTc dimercaptosuccinic acid [DMSA] is traditionally used.

Blood samples must be obtained frequently after the tracer injection, and, if the GFR is less than 30 mL/min, an additional sample should be obtained at 24 hours. Renal blood flow can be estimated as a fraction of cardiac output depending on the amount of radioactivity in the kidney.

Urinary obstruction can also be identified based on the relative tracer excretion via each kidney.

Previous
Next

Renal Angiography

Renal angiography is the criterion standard for direct visualization of the renal vasculature. It is invaluable in the diagnosis and prognosis of renal artery stenosis and renal vein thrombosis.[14] Renal arteriography may also provide complementary information in the evaluation of a renal mass, especially for mapping before surgery.

Renal angiography in a patient with refractory hyp Renal angiography in a patient with refractory hypertension. Note the narrowing (arrow) of the right renal artery consistent with renal artery stenosis.
Previous
Next

Retrograde Pyelography

Retrograde pyelography is an essential tool for localizing the site of urinary tract obstruction. It may also prove therapeutic (eg, ureteral stents can be placed to relieve an obstruction). It has been supplanted by ultrasonography or CT scanning in most settings. However, it is helpful in patients with a known pelvic malignancy when hydronephrosis is absent owing to ureteral encasement.[15]

Dilated collecting system after injection of contr Dilated collecting system after injection of contrast into the ureter via a cystoscope. The flow of contrast is opposite the usual flow of urine, hence the term retrograde pyelography. This patient exhibited a stricture at the distal insertion of the ureter into the bladder.
Previous
Next

Diuretic Renography

Diuretic renography is widely used to discriminate functional versus anatomical obstruction after identification of a dilated upper urinary tract (usually with ultrasonography or CT scanning).[16] Two important functional aspects of kidney function can be assessed: (1) clearance of each kidney and (2) the flow of urine through the urinary tract.

Furosemide is administered with a radiopharmaceutical (usually MAG 3, technetium-99m-mercaptoacetyl triglycine). However, a single-kidney GFR of less than 15 mL/min significantly limits the usefulness of diuretic renography because of diuretic resistance.

Indications

Diuretic renography is primarily used to determine whether a dilated urinary tract is secondary to obstructive lesions (eg, tumors) or nonobstructive causes (eg, persistent dilation after relief of a previous obstruction).

Technique

The patient should be adequately hydrated to produce 1-3 mL/min of urine; 500 mL of oral hydration is given 30 minutes before the procedure. In some cases, the urine specific gravity is measured to ensure adequate hydration (ideally, the specific gravity should be less than 1.015). The bladder should be emptied before the test.

The dosage should be reduced in children based on body surface area. In infants, the washout interpretation is difficult owing to variable GFR, sodium absorption, renal blood flow, and urine-concentrating ability. Nonetheless, ruling out of obstruction is vital in this setting.[17]

Limitations

Patients with a single-kidney GFR of less than 15 mL/min will not respond to diuretic administration.

Previous
 
Contributor Information and Disclosures
Author

Paul G Schmitz, MD, DPharm, FACP, CSH Professor of Internal Medicine, Director of Organ Systems, Department of Internal Medicine, Division of Nephrology, St Louis University School of Medicine; Staff Physician, St Louis University Medical Center and John Cochran Veterans Affairs Medical Center

Paul G Schmitz, MD, DPharm, FACP, CSH is a member of the following medical societies: American College of Physicians, American Society of Hypertension, American Society of Nephrology, International Society of Nephrology

Disclosure: Nothing to disclose.

Coauthor(s)

Geetha Maddukuri, MD Fellow in Nephrology, St Louis University School of Medicine

Geetha Maddukuri, MD is a member of the following medical societies: American College of Physicians, American Medical Association, American Society of Nephrology, Missouri State Medical Association, National Kidney Foundation

Disclosure: Nothing to disclose.

Chief Editor

Caroline R Taylor, MD Associate Professor, Department of Diagnostic Radiology, Yale University School of Medicine; Chief, Diagnostic Imaging Service, Veterans Affairs Connecticut Health Care System

Caroline R Taylor, MD is a member of the following medical societies: Radiological Society of North America

Disclosure: Nothing to disclose.

References
  1. Mandeville JA, Gnessin E, Lingeman JE. Imaging evaluation in the patient with renal stone disease. Semin Nephrol. 2011 May. 31(3):254-8. [Medline].

  2. Choyke PL. Radiologic evaluation of hematuria: guidelines from the American College of Radiology's appropriateness criteria. Am Fam Physician. 2008 Aug 1. 78(3):347-52. [Medline].

  3. Bertolotto M, Cicero C, Perrone R, Degrassi F, Cacciato F, Cova MA. Renal Masses With Equivocal Enhancement at CT: Characterization With Contrast-Enhanced Ultrasound. AJR Am J Roentgenol. 2015 May. 204 (5):W557-65. [Medline].

  4. Bhutani H, Smith V, Rahbari-Oskoui F, Mittal A, Grantham JJ, Torres VE, et al. A comparison of ultrasound and magnetic resonance imaging shows that kidney length predicts chronic kidney disease in autosomal dominant polycystic kidney disease. Kidney Int. 2015 Jul. 88 (1):146-51. [Medline].

  5. Pei Y, Hwang YH, Conklin J, Sundsbak JL, Heyer CM, Chan W, et al. Imaging-based diagnosis of autosomal dominant polycystic kidney disease. J Am Soc Nephrol. 2015 Mar. 26 (3):746-53. [Medline].

  6. Nchimi A, Biquet JF, Brisbois D, Reginster P, Bouali K, Saive C, et al. Duplex ultrasound as first-line screening test for patients suspected of renal artery stenosis: prospective evaluation in high-risk group. Eur Radiol. 2003 Jun. 13(6):1413-9. [Medline].

  7. Tasian GE, Pulido JE, Keren R, Dick AW, Setodji CM, Hanley JM, et al. Use of and regional variation in initial CT imaging for kidney stones. Pediatrics. 2014 Nov. 134 (5):909-15. [Medline].

  8. Morcos SK. Computed tomography urography technique, indications and limitations. Curr Opin Urol. 2007 Jan. 17(1):56-64. [Medline].

  9. Bokacheva L, Rusinek H, Zhang JL, Lee VS. Assessment of renal function with dynamic contrast-enhanced MR imaging. Magn Reson Imaging Clin N Am. 2008 Nov. 16(4):597-611, viii. [Medline]. [Full Text].

  10. Grenier N, Hauger O, Cimpean A, Pérot V. Update of renal imaging. Semin Nucl Med. 2006 Jan. 36(1):3-15. [Medline].

  11. Grenier N, Mendichovszky I, de Senneville BD, Roujol S, Desbarats P, Pedersen M, et al. Measurement of glomerular filtration rate with magnetic resonance imaging: principles, limitations, and expectations. Semin Nucl Med. 2008 Jan. 38(1):47-55. [Medline].

  12. Silverman SG, Leyendecker JR, Amis ES Jr. What is the current role of CT urography and MR urography in the evaluation of the urinary tract?. Radiology. 2009 Feb. 250(2):309-23. [Medline].

  13. Hilson AJ. Functional renal imaging with nuclear medicine. Abdom Imaging. 2003 Mar-Apr. 28(2):176-9. [Medline].

  14. AbuRahma AF, Yacoub M. Renal imaging: duplex ultrasound, computed tomography angiography, magnetic resonance angiography, and angiography. Semin Vasc Surg. 2013 Dec. 26 (4):134-43. [Medline].

  15. Kunin M, Goodwin WE. The encased ureter: bullet and bodkin pattern, a reliable radiographic sign. Br J Urol. 1990 Nov. 66(5):471-4. [Medline].

  16. O'Reilly P, Aurell M, Britton K, Kletter K, Rosenthal L, Testa T. Consensus on diuresis renography for investigating the dilated upper urinary tract. Radionuclides in Nephrourology Group. Consensus Committee on Diuresis Renography. J Nucl Med. 1996 Nov. 37(11):1872-6. [Medline].

  17. Gordon I, Piepsz A, Sixt R. Guidelines for standard and diuretic renogram in children. Eur J Nucl Med Mol Imaging. 2011 Jun. 38(6):1175-88. [Medline].

 
Previous
Next
 
Sonogram revealing a dilated collecting system caused by an enlarged lymph node in a patient with B-cell lymphoma.
Dilated collecting system after injection of contrast into the ureter via a cystoscope. The flow of contrast is opposite the usual flow of urine, hence the term retrograde pyelography. This patient exhibited a stricture at the distal insertion of the ureter into the bladder.
Plain film of the abdomen revealing a radiopaque staghorn calculus involving the entire pelvicalyceal system of the right kidney (arrows). This stone was composed of magnesium ammonium phosphate (struvite). Surgical excision, antimicrobial treatment, and consumption of 4-5 L/d of water are all required to treat and prevent this type of stone.
CT scan reveals an enormous, contrast-enhanced mass in the right kidney of a patient with Wilms tumor. The mass consists of several hypodense areas most likely reflecting necrosis or hemorrhage.
Numerous cystic structures are evident on the renal sonogram.
Computed tomography scan of autosomal-recessive polycystic kidney disease revealing many small cysts. Note the small cyst in the head of the pancreas (arrow). RK = right kidney.
Helical CT scanning in a patient with hematuria. Nonenhanced CT image shows bilateral renal calculi (arrows). This imaging technique is considered the reference standard for stone evaluation.
Renal angiography in a patient with refractory hypertension. Note the narrowing (arrow) of the right renal artery consistent with renal artery stenosis.
Intravenous pyelogram in a patient with medullary sponge kidney. Note the brushlike pattern (arrows) involving the renal papillae. This pattern is consistent with numerous ectatic medullary collecting ducts and is pathognomonic for medullary sponge kidney.
 
 
 
All material on this website is protected by copyright, Copyright © 1994-2016 by WebMD LLC. This website also contains material copyrighted by 3rd parties.