DOI:10.2214/AJR.08.1129
AJR 2009; 192:462-467
© American Roentgen Ray Society
Multitechnique Evaluation of Renal Hydatid Disease
Ahmet Tuncay Turgut1,
Kemal Ödev2,
Adnan Kabaalio
lu3,
Shweta Bhatt4 and
Vikram S. Dogra4
1 Department of Radiology, Ankara Training and Research Hospital, Ankara,
Turkey.
2 Department of Radiology, Meram Faculty of Medicine, Selçuk University,
Konya, Turkey.
3 Department of Radiology, Faculty of Medicine, Akdeniz University, Antalya,
Turkey.
4 Department of Imaging Sciences, University of Rochester School of Medicine,
601 Elmwood Ave., Box 648, Rochester, NY 14642.
Received April 23, 2008;
accepted after revision August 21, 2008.
Address correspondence to V. S. Dogra
(Vikram_Dogra{at}urmc.rochester.edu).
Abstract
OBJECTIVE. Hydatid involvement of the kidney accounts for only
2–4% of all cases of hydatid disease. The purpose of this article is to
review the imaging features of hydatid disease of the kidney and thus show the
role of radiography, excretory urography, sonography, CT, and MRI in the
diagnosis of hydatidosis.
CONCLUSION. The radiologist should be familiar with the imaging
findings of hydatid disease because early diagnosis is important for more
appropriate treatment.
Keywords: CT • hydatid cyst • kidney • MRI • sonography
Introduction
Hydatid disease, mainly caused by Echinococcus granulosus, is
endemic in many parts of the world. After the patient ingests food
contaminated by the eggs of the parasite, the embryos become lodged in several
organs, including the kidney. The formation of germinal and laminated
membranes causes the production of hydatid fluid, which is later replaced with
organized or calcified membranes
[1]. Hydatid involvement of the
kidney accounts for only 2% of all cases of hydatid disease
[2]. This article reviews the
imaging features of renal hydatidosis.
Imaging of Renal Hydatid Cyst
Radiography
The appearance of a soft-tissue mass or ring-shaped calcifications in the
renal region may be associated with renal hydatid disease
[2].
Excretory Urography
Excretory urography provides assessment of renal function. Caliceal
distortion is the predominant finding, followed by caliectasis and
nonfunctioning kidney, possibly caused by the mass effect of cystic lesions
[2]
(Fig. 1A). Excretory urography
may reveal the interaction between a renal hydatid cyst and the collecting
system, which results in the opacification of an extracaliceal cavity
[3]. Multiple round filling
defects representing daughter cysts can be seen in the excretory system in
such cases [4].
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Fig. 1A —56-year-old man with surgically proven renal hydatid disease.
Excretory urography image reveals curvilinear wall calcification
(arrowhead) of hydatid cyst located at upper pole of left kidney and
causing slight caliceal distortion (arrow).
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Sonography
The characteristic sonographic finding is anechoic lesions with
well-defined margins. In the classification system of Gharbi et al.
[5], hydatid cysts are
classified into five types on the basis of their sonographic appearance
[5]. Type I hydatid cysts
appear as well-defined, purely anechoic spaces that may be indistinguishable
from simple renal cysts. However, a double-contour thick wall or a history of
living in endemic regions strongly suggests a diagnosis of hydatid cyst
[4,
6]. The "falling
snowflakes" sign, which is characterized by multiple echogenic foci of
hydatid sand, is a pathognomonic finding for hydatid cyst
[4]. In type II hydatid cysts,
a focal or diffuse detachment of the inner germinal layer results in a
floating membrane inside the cyst (Fig.
2A). Although type III hydatid cysts with multiseptated daughter
cysts (Fig. 3A) can be
misinterpreted as congenital polycystic disease of the kidney
[7], diffuse and bilateral
involvement of both kidneys in the latter may aid in the differentiation
[2]. Type IV hydatid cysts
contain coarse infolded membranes and internal echoes. The heterogeneous
appearance of type IV lesions should be differentiated from infected renal
cysts, abscesses, and neoplasms
[8]. The presence of a linear
layer of fluid between the membranes with no posterior echoes within a
tumorlike mass, referred to as the "spiral sign," may be helpful
for differentiation of type IV cysts from renal neoplasms
[9]. Thus, the presence of a
daughter cyst and echoic membrane debris and the detection of hydatid cysts in
other organs favor the diagnosis of hydatidosis
[8]. Calcification with a
ringlike pattern occurs in the pericystic layer of the wall of the hydatid
cyst in type V lesions [4].
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Fig. 3A —14-year-old girl with serologically proven renal hydatid
disease showing solidification of internal echotexture of hydatid cyst.
Sonogram reveals daughter cyst (calipers) within renal hydatid cyst
with indistinct margins and mixed internal echogenicity (arrow). LK
indicates left kidney.
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CT
Typical CT findings for renal hydatidosis include a cyst with a thick or
calcified wall, a unilocular cyst with a detached membrane, a multiloculated
cyst with mixed internal density, and daughter cysts with lower density than
the maternal matrix [6,
10] (Figs.
2B and
4A). The fluid within type I
hydatid cysts has a low attenuation (Fig.
5A). The cyst wall in type I hydatid cysts is better delineated
with contrast-enhanced CT compared with sonography
[8]. The presence of daughter
cysts on CT helps to differentiate type III hydatid cysts from renal abscesses
[11]. A zone of decreased
contrast enhancement surrounding an early abscess, which represents infected
but nonnecrotic renal parenchyma, appears hyperdense on delayed CT scans.
Moreover, thickening of Gerota's fascia and perirenal stranding of tissue in
fat favor the diagnosis of an abscess. CT can be helpful in the diagnosis of
type IV hydatid cysts, which show an appearance similar to pseudotumor
[3]. Furthermore, ringlike
calcifications in the wall of type V hydatid cysts can be shown
[6,
10] (Figs.
1B and
1C). CT can also show other
organ involvement (Fig.
5B).
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Fig. 2B —40-year-old woman with serologically proven renal hydatid
disease. Axial CT scan shows unilocular left renal hydatid cyst with thick
wall (solid arrow) and slightly heterogeneous internal density
because of infolded parasitic membrane (dashed arrow).
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Fig. 5A —63-year-old man with serologically proven disseminated
hydatid disease. Sagittal sonogram shows type I renal hydatid cyst
(arrow) with well-defined, purely anechoic internal echotexture.
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Fig. 1B —56-year-old man with surgically proven renal hydatid disease.
Axial contrast-enhanced CT scans at nephrographic (B) and pyelographic
(C) phases show enhancement and calcification of cyst wall (dashed
arrow, B; dashed arrow, C).
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Fig. 1C —56-year-old man with surgically proven renal hydatid disease.
Axial contrast-enhanced CT scans at nephrographic (B) and pyelographic
(C) phases show enhancement and calcification of cyst wall (dashed
arrow, B; dashed arrow, C).
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Fig. 5B —63-year-old man with serologically proven disseminated
hydatid disease. Contrast-enhanced axial CT scan reveals involvement of liver
(solid arrow), spleen (dashed arrow), and right kidney
(open arrow) by hydatid disease.
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MRI
Hydatid fluid is hypointense on T1-weighted and hyperintense on T2-weighted
images [4] (Fig.
6A,
6B), although a heterogeneous
signal intensity may also be detected on T2-weighted images (Fig.
7A,
7B). The characteristic hypo
intense rim sign is more evident on T2-weighted images
[4,
10]
(Fig. 4B). The fluid within
the daughter cysts may appear hypointense, isointense, or hyperintense
relative to the maternal matrix on T1- and T2-weighted images
[4]
(Fig. 3B). MRI also reveals,
with all sequences, the hypointense infolded linear structures corresponding
to collapsed parasitic membranes
[4]
(Fig. 8A). Moreover, contrast
enhancement of the collapsed membranes and cyst wall can be depicted
(Fig. 8B).
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Fig. 6A —68-year-old woman with surgically proven renal hydatid
disease. Coronal T1-weighted (A) and T2-weighted (B) MR images
show decreased (arrow, A) and increased (arrow,
B) signal intensities, representing pure cystic character for hydatid
cyst located at upper pole of left kidney.
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Fig. 6B —68-year-old woman with surgically proven renal hydatid
disease. Coronal T1-weighted (A) and T2-weighted (B) MR images
show decreased (arrow, A) and increased (arrow,
B) signal intensities, representing pure cystic character for hydatid
cyst located at upper pole of left kidney.
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Fig. 7A —54-year-old man with surgically proven renal hydatid disease.
Coronal T1-weighted (A) and T2-weighted (B) MR images show
decreased signal intensity (solid arrow, A) and mixed internal
signal intensity (solid arrow, B) within hydatid cyst located
at upper pole of left kidney. Nodular liver lesion (open arrows,
A and B) that appears as heterogenously hypointense in A
and hypointense with peripheral and internal signal void areas in B
corresponds to hydatid cyst with internal and wall calcifications.
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Fig. 7B —54-year-old man with surgically proven renal hydatid disease.
Coronal T1-weighted (A) and T2-weighted (B) MR images show
decreased signal intensity (solid arrow, A) and mixed internal
signal intensity (solid arrow, B) within hydatid cyst located
at upper pole of left kidney. Nodular liver lesion (open arrows,
A and B) that appears as heterogenously hypointense in A
and hypointense with peripheral and internal signal void areas in B
corresponds to hydatid cyst with internal and wall calcifications.
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Fig. 4B —52-year-old woman with surgically proven left renal hydatid
cyst. Axial T2-weighted MR image reveals rim sign (arrow) with low
signal intensity corresponding to wall of left renal hydatid cyst as well as
daughter cysts (asterisk) appearing hyperintense relative to maternal
matrix.
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Fig. 3B —14-year-old girl with serologically proven renal hydatid
disease showing solidification of internal echotexture of hydatid cyst.
Pretreatment T2-weighted MR image shows well-circumscribed hyperintense cyst
with internal isointense daughter cysts (arrow).
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Fig. 8A —50-year-old man with surgically proven right renal hydatid
cyst. Axial T2-weighted MR image shows infolded hypointense linear structures
within right renal hydatid cyst (arrow), corresponding to collapsed
parasitic membranes.
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Imaging Alterations Secondary to Treatment
Medical Treatment
Medical treatment with benzimidazole compounds is expected to provide a
reduction in size and volume of renal hydatid cysts and solidification of the
cyst contents. This process can be monitored using sonography.
Surgery
The preferred surgical procedure is partial or total nephrectomy in cases
with significantly destroyed renal parenchyma
[12]. However, renal-sparing
surgery with only cyst removal may be an alternative
[13]. Recurrence is a
significant problem in the late postoperative period, with an incidence
ranging between 10% and 30%
[14]. Therefore, the
radiologist should be familiar with the follow-up imaging findings to prevent
misinterpretation of the postoperative images as recurrence.
Percutaneous Treatment
The technique of sonographically guided percutaneous aspiration, injection,
and reaspiration is safe and effective for the treatment of renal hydatidosis
[13]. All type I
(Fig. 2A) and type II lesions,
as well as some type III lesions without nondrainable solid material, are
appropriate for this technique. It is important to note that follow-up
findings such as a decrease in the dimensions of the cysts, solidification of
the contents, a change in echo pattern, and irregularity in the walls of cysts
are signs of a cure in patients treated with the percutaneous aspiration,
injection, and reaspiration technique
[13,
15] (Figs.
3C and
9A,
9B,
9C,
9D,
9E,
9F).
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Fig. 3C —14-year-old girl with serologically proven renal hydatid
disease showing solidification of internal echotexture of hydatid cyst.
Sagittal sonogram of right kidney obtained 1 year after percutaneous treatment
shows solidification of internal echotexture of hydatid cyst
(circumscribed lesion).
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Fig. 9A —17-year-old girl with serologically proven renal hydatid
disease. Serial sonograms obtained during (A and B) and then 1
week (C), 2 years (D), and 3 years (E and F) after
percutaneous treatment of left renal hydatid cyst reveal reduction in size and
volume of cyst, irregularity of cyst walls, and solidification of cyst
contents with changes in echo pattern, which are signs of cure. A and
B show sonographic guidance for puncture of cyst with 18-gauge Chiba
needle (arrow, A) and administration of absolute alcohol (95%)
to cavity through needle (arrow, B) for scolicidal effect and
sclerosis. Hydatid cyst (double arrows, C) shows mixed
echogenicity because of collapsed membranes. Pseudotumor appearance
(arrow, D) is present because of disappearance of fluid
component. Sagittal (double arrows, E) and axial
(arrow, F) sonograms of treated cyst show irregular,
hypoechoic, solid structure. LK indicates left kidney.
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Fig. 9B —17-year-old girl with serologically proven renal hydatid
disease. Serial sonograms obtained during (A and B) and then 1
week (C), 2 years (D), and 3 years (E and F) after
percutaneous treatment of left renal hydatid cyst reveal reduction in size and
volume of cyst, irregularity of cyst walls, and solidification of cyst
contents with changes in echo pattern, which are signs of cure. A and
B show sonographic guidance for puncture of cyst with 18-gauge Chiba
needle (arrow, A) and administration of absolute alcohol (95%)
to cavity through needle (arrow, B) for scolicidal effect and
sclerosis. Hydatid cyst (double arrows, C) shows mixed
echogenicity because of collapsed membranes. Pseudotumor appearance
(arrow, D) is present because of disappearance of fluid
component. Sagittal (double arrows, E) and axial
(arrow, F) sonograms of treated cyst show irregular,
hypoechoic, solid structure. LK indicates left kidney.
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Fig. 9C —17-year-old girl with serologically proven renal hydatid
disease. Serial sonograms obtained during (A and B) and then 1
week (C), 2 years (D), and 3 years (E and F) after
percutaneous treatment of left renal hydatid cyst reveal reduction in size and
volume of cyst, irregularity of cyst walls, and solidification of cyst
contents with changes in echo pattern, which are signs of cure. A and
B show sonographic guidance for puncture of cyst with 18-gauge Chiba
needle (arrow, A) and administration of absolute alcohol (95%)
to cavity through needle (arrow, B) for scolicidal effect and
sclerosis. Hydatid cyst (double arrows, C) shows mixed
echogenicity because of collapsed membranes. Pseudotumor appearance
(arrow, D) is present because of disappearance of fluid
component. Sagittal (double arrows, E) and axial
(arrow, F) sonograms of treated cyst show irregular,
hypoechoic, solid structure. LK indicates left kidney.
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Fig. 9D —17-year-old girl with serologically proven renal hydatid
disease. Serial sonograms obtained during (A and B) and then 1
week (C), 2 years (D), and 3 years (E and F) after
percutaneous treatment of left renal hydatid cyst reveal reduction in size and
volume of cyst, irregularity of cyst walls, and solidification of cyst
contents with changes in echo pattern, which are signs of cure. A and
B show sonographic guidance for puncture of cyst with 18-gauge Chiba
needle (arrow, A) and administration of absolute alcohol (95%)
to cavity through needle (arrow, B) for scolicidal effect and
sclerosis. Hydatid cyst (double arrows, C) shows mixed
echogenicity because of collapsed membranes. Pseudotumor appearance
(arrow, D) is present because of disappearance of fluid
component. Sagittal (double arrows, E) and axial
(arrow, F) sonograms of treated cyst show irregular,
hypoechoic, solid structure. LK indicates left kidney.
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Fig. 9E —17-year-old girl with serologically proven renal hydatid
disease. Serial sonograms obtained during (A and B) and then 1
week (C), 2 years (D), and 3 years (E and F) after
percutaneous treatment of left renal hydatid cyst reveal reduction in size and
volume of cyst, irregularity of cyst walls, and solidification of cyst
contents with changes in echo pattern, which are signs of cure. A and
B show sonographic guidance for puncture of cyst with 18-gauge Chiba
needle (arrow, A) and administration of absolute alcohol (95%)
to cavity through needle (arrow, B) for scolicidal effect and
sclerosis. Hydatid cyst (double arrows, C) shows mixed
echogenicity because of collapsed membranes. Pseudotumor appearance
(arrow, D) is present because of disappearance of fluid
component. Sagittal (double arrows, E) and axial
(arrow, F) sonograms of treated cyst show irregular,
hypoechoic, solid structure. LK indicates left kidney.
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Fig. 9F —17-year-old girl with serologically proven renal hydatid
disease. Serial sonograms obtained during (A and B) and then 1
week (C), 2 years (D), and 3 years (E and F) after
percutaneous treatment of left renal hydatid cyst reveal reduction in size and
volume of cyst, irregularity of cyst walls, and solidification of cyst
contents with changes in echo pattern, which are signs of cure. A and
B show sonographic guidance for puncture of cyst with 18-gauge Chiba
needle (arrow, A) and administration of absolute alcohol (95%)
to cavity through needle (arrow, B) for scolicidal effect and
sclerosis. Hydatid cyst (double arrows, C) shows mixed
echogenicity because of collapsed membranes. Pseudotumor appearance
(arrow, D) is present because of disappearance of fluid
component. Sagittal (double arrows, E) and axial
(arrow, F) sonograms of treated cyst show irregular,
hypoechoic, solid structure. LK indicates left kidney.
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Conclusion
Imaging features such as floating membranes, daughter cysts, and rim sign
are highly suggestive for hydatid disease. A renal hydatid cyst with these
features can be diagnosed accurately, but a diagnostic dilemma occurs in cases
with a nonspecific heterogeneous appearance. In such cases, a finding of
double-contour thick wall on sonography and the detection of hydatid cysts in
other organs favor the diagnosis of hydatid cyst, whereas CT findings such as
the thickening of Gerato's fascia and perirenal stranding of fat in tissue
suggest an abscess. Presence of the spiral sign may be helpful in
differentiating the pseudotumor appearance of a hydatid cyst from a renal
neoplasm.
Hydatid involvement of the kidney accounts for only 2% of all cases of
hydatid disease. This article reviews the imaging features of renal hydatid
disease and the role of imaging techniques in the diagnosis of hydatidosis.
Radiologically, the hydatid cyst may have an appearance ranging from a cystic
lesion to a completely solid one, depending on the stage of evolution of the
disease. The radiologist's familiarity with the imaging findings of the
disease is very important for early diagnosis and more appropriate
treatment.
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Abstract
Introduction
