eMedicine Specialties > Radiology > Pediatrics

Multicystic Dysplastic Kidney: Imaging

Author: John S Wiener, MD, FACS, FAAP, Clinical Assistant Professor, Division of Urology, University of North Carolina at Chapel Hill; Associate Professor of Surgery and Associate Residency Program Director, Division of Urologic Surgery, Associate Professor of Pediatrics, Duke University School of Medicine
Coauthor(s): Michaella E Maloney, Duke University School of Medicine; Ana Maria Gaca, MD, Assistant Professor, Division of Pediatric Radiology, Duke University Medical Center
Contributor Information and Disclosures

Updated: Feb 19, 2008

Radiography

Findings

Incidental findings on kidney, ureter, and bladder (KUB) images include displacement of the bowels when the affected kidney is enlarged (see Image 1). Also, ringlike calcifications of the cyst walls may be seen on plain images.

Retrograde pyelography may demonstrate an atretic or absent ureter.

Computed Tomography

Findings

MCDK can be an incidental finding, but CT studies are not part of the diagnostic investigation. They show the typical multicystic appearance of MCDK with little or no parenchyma (see Images 8-9). Cyst wall calcification can be seen.

If a contrast-enhanced CT is performed, there is no excretion seen.

Magnetic Resonance Imaging

Findings

MCDK can be an incidental finding but these MRIs are not part of the diagnostic investigation. MRIs show the typical multicystic appearance of MCDK with little or no parenchyma (see Images 8-9).

Ultrasonography

Findings

Prenatal imaging (see Images 2-3) findings include hypoechoic cysts of variable sizes and shapes, interfaces between cysts, a nonmedial location of large cysts, the absence of an identifiable renal sinus, a lack of communication between cysts on sonograms, and minimal surrounding parenchyma. Only 20% of MCDKs have an identifiable reniform shape (compared with 90% of hydronephrotic kidneys). Bilateral MCDK may occur with oligohydramnios as a result of poor urine production. The cysts of MCDK may become enlarged, may shrink, or may involute during fetal life.

Postnatal sonograms are shown in Images 4-5. The diagnostic criteria for postnatal sonography are the same as those for prenatal sonography.

Degree of Confidence

Ultrasonography is an excellent diagnostic test for MCDK, with a high degree of confidence. An obstructive uropathy with little renal parenchyma can mimic MCDK, but radionuclide studies can provide confirmation of the diagnosis. Autosomal recessive PCKD is not usually mistaken for MCDK, as the cysts in PCKD are too small to be visualized on sonograms, and the parenchyma is generally homogeneously hyperechoic. Other cystic diseases typically appear with some functional parenchyma.

False Positives/Negatives

The greatest source of false-positive errors occurs in the setting of hydronephrosis or UPJO. A reniform shape and/or a large cystic structure in the medial portion of the kidney are more indicative of hydronephrosis than MCDK. Unlike in hydronephrosis, where there is communication with the central renal pelvis, the cysts of the classic form of MCDK do not communicate.

Regarding false-negative results, renal agenesis with non-renal cystic structures in the retroperitoneum (eg, an adrenal cystic mass) could potentially be mistaken for MCDK.

Nuclear Imaging

Findings

Nuclear renograms are used to evaluate the perfusion, function, and drainage of the kidneys, as there is uptake of the radiotracer into a functioning kidney and excretion into the renal pelvis, ureter, and bladder. In the area of the MCDK, a photopenic region is present that represents displaced tissue with background activity only (see Image 7).

Degree of Confidence

Nuclear medicine studies are the best imaging studies for differentiating between MCDK and hydronephrosis; however, severe hydronephrosis with poor renal function may still be difficult to distinguish from MCDK. The similarity may not be clinically relevant because reconstructive surgery is usually not indicated in the setting of poor (ie, <10-15%) differential function.

MAG-3, diethylenetriamine-pentaacetic acid (DTPA), and dimercaptosuccinic acid (DMSA) are the preferred agents. Tests with these agents are sensitive for detecting renal function, but the anatomic resolution is relatively poor. Other forms of imaging are required to visualize the specific anatomy of the kidney.

False Positives/Negatives

On a nuclear renogram, anything that impairs the renal circulation, such as a renal artery stenosis or a renal vein thrombosis, appears as a nonfunctioning kidney; nevertheless, the renal parenchyma should appear relatively normal with ultrasonography. In addition, renal agenesis may mimic the nonfunctioning kidney of MCDK, but the tissue is absent on sonograms.

False-negative results may arise in the setting of severe hydronephrosis. In a poorly functioning kidney, the intervention is the same as in MCDK; therefore, discriminating between these 2 disorders may not be imperative.

Angiography

Findings

Angiography is not indicated for the evaluation of MCDK; however, if catheterization, CT scanning, or MRA is performed, the ipsilateral renal artery is atretic or absent.

• Search for CME/CE on This Topic »

• Cystic Diseases of the Kidney (Urology)
• Multicystic Renal Dysplasia (Pediatrics: General Medicine)
• Polyhydramnios and Oligohydramnios (Pediatrics: Cardiac Disease and Critical Care Medicine)
• Neonatal Hypertension (Pediatrics: Cardiac Disease and Critical Care Medicine)