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Clinical Procedures > Radiology
Bedside Ultrasonography, Obstructive Uropathy
Article Last Updated: May 20, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 13  
Author: Timothy Jang, MD, Director of Emergency Ultrasound, Olive View-UCLA Medical Center, Clinical Faculty, Division of Emergency Medicine, Washington University School of Medicine
Editors: James Quan-Yu Hwang, MD, Attending Physician, Department of Emergency Medicine, Brigham & Women's Hospital; Clinical Instructor, Harvard Medical School; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Author and Editor Disclosure
Synonyms and related keywords:
focused emergency renal sonography, FERS, renal ultrasound, bedside ultrasound, bedside ultrasonography, renal colic, obstructive uropathy, hydronephrosis, kidney ultrasound
Patients who present to the emergency department (ED) or other ambulatory care setting commonly report abdominal and flank pain. Unfortunately, patient history and physical examination often lack the necessary sensitivity and specificity to accurately diagnose underlying etiologies without further testing. Focused bedside ultrasonography is a valuable diagnostic tool that can often facilitate a timely diagnosis for these patients.1, 2, 3 4 Ultrasonography is especially important in determining the cause of the sudden onset of abdominal or flank pain, since patients with symptomatic abdominal aneurysms can be difficult to distinguish from those with renal colic. In fact, making an accurate diagnosis of ureteronephrolithiasis is especially important, since renal colic is the most common misdiagnosis in patients with missed abdominal aortic aneurysms. Click here to complete a Medscape CME activity on the evaluation of acute abdominal pain.
The benefits of focused emergency renal sonography (FERS) include the following: - Decreases the time to diagnosis for obstructive uropathy
- Helps accurately diagnose obstructive uropathy5
- Helps assess the degree of obstruction in renal colic
- Helps rule out other, more dangerous, pathology (eg, symptomatic aortic aneurysm)6
- Helps identify obstructive causes of renal insufficiency
- Can be performed quickly
- Is safe in pregnant patients and children and requires less radiation than either intravenous pyelography (IVP) or helical CT7, 8, 9, 10
Indications for focused emergency renal sonography (FERS) include the following: - Sudden onset of abdominal pain
- Colicky flank pain that radiates to the groin
- Hematuria (Click here to complete a Medscape CME course on persistent prostatic hematuria.)
- Acute renal insufficiency
While renal masses and cysts can often be identified by FERS, these are outside the scope of emergency ultrasonography. Patients with suspected renal masses or cysts should be referred to a radiologist for further evaluation.
Performance of focused emergency renal sonography (FERS) should not delay the initiation of emergent treatments such as intravenous fluids or pressors, when indicated. Although ongoing resuscitation and extremis are not contraindications, FERS can be difficult to perform in such situations.
Anesthesia is generally not necessary for sonographic evaluation.
- Ultrasound machine
- Ultrasound-conducting gel
Patients should be evaluated in the supine position but can be moved to the posterior oblique and lateral decubitus positions for improved visualization. Male patients should have the entire abdomen exposed for the examination. Take special care with female patients to minimize the exposure of sensitive areas.
Relevant anatomy
The kidneys are retroperitoneal structures; the right kidney is more caudal than the left. The right kidney is posteroinferior to the liver and gallbladder, while the left kidney is inferomedial to the spleen.
Components of examination
Focused emergency renal sonography (FERS) should include transverse and longitudinal views of both kidneys with clear anatomical relationship to the liver or spleen for unambiguous identification.
Technique
- To visualize the right kidney, the transducer-probe should be placed over the right flank, lateral to the liver. This allows the liver to be used as an acoustic window and avoids interference from air-filled bowel. In addition, the probe can be placed posterior to the liver for improved visualization of the kidney.
Probe placement for longitudinal view of the right kidney.
Probe placement for transverse view of the right kidney.
Longitudinal view of the right kidney. - To visualize the left kidney, the transducer-probe should be placed over the left flank, lateral and posterior to the spleen. This allows the spleen to be used as an acoustic window and also avoids interference from air-filled bowel.
Probe placement for longitudinal view of the left kidney.
Probe placement for anterior approach to the left kidney.
Longitudinal view of the left kidney. - The cortex of the kidneys should be gray but less echogenic than either the liver or spleen. Thus, hydronephrosis would be seen in the central areas.
Hydronephrosis.
Hydronephrosis. - The capsule of the kidneys should appear smooth and echogenic, forming clear borders to the kidneys.
- Scan both kidneys. This allows for more accurate assessment of hydronephrosis and avoids the pitfall of misdiagnosing prominent renal pyramids as hydronephrosis.
- Cysts can be mistaken for hydronephrosis. However, cysts tend to be peripheral and hydronephrosis should always be central.
- If the kidneys are difficult to visualize, reposition the patient in the posterior oblique or lateral decubitus position.
- Although the sensitivity of focused emergency renal sonography (FERS) for hydronephrosis in the setting of ureterolithiasis is only 80-90%, consider ultrasonography of the aorta if hydronephrosis is not seen.11, 3
- Consider nonstone causes of hydronephrosis, such as urinary retention, pregnancy, and neoplasm.
- Patients in whom cysts or masses are identified should be referred to a radiologist for further evaluation.
Typically, no complications are associated with this procedure.
The authors and editors of eMedicine gratefully acknowledge the assistance of Lars Grimm with the literature review and referencing for this article.
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Probe placement for longitudinal view of the right kidney. |
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Probe placement for transverse view of the right kidney. |
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Probe placement for longitudinal view of the left kidney. |
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| Media file 5:
Probe placement for anterior approach to the left kidney. |
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- Henderson SO, Hoffner RJ, Aragona JL, Groth DE, Esekogwu VI, Chan D. Bedside emergency department ultrasonography plus radiography of the kidneys, ureters, and bladder vs intravenous pyelography in the evaluation of suspected ureteral colic. Acad Emerg Med. Jul 1998;5(7):666-71. [Medline].
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- Dalrymple NC, Verga M, Anderson KR, Bove P, Covey AM, Rosenfield AT, et al. The value of unenhanced helical computerized tomography in the management of acute flank pain. J Urol. Mar 1998;159(3):735-40. [Medline].
- Manthey DE, Teichman J. Nephrolithiasis. Emerg Med Clin North Am. Aug 2001;19(3):633-54, viii. [Medline].
- Levy JA, Noble VE. Bedside ultrasound in pediatric emergency medicine. Pediatrics. May 2008;121(5):e1404-12. [Medline].
- Levy JA, Bachur RG. Bedside ultrasound in the pediatric emergency department. Curr Opin Pediatr. Jun 2008;20(3):235-42. [Medline].
- Sinclair D, Wilson S, Toi A, Greenspan L. The evaluation of suspected renal colic: ultrasound scan versus excretory urography. Ann Emerg Med. May 1989;18(5):556-9. [Medline].
Bedside Ultrasonography, Obstructive Uropathy excerpt Article Last Updated: May 20, 2008
Topic originally published: May 20, 2008
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