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A benign looking lesion , not always naive , some times a source of confusion , in the lt kidney.

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Did you turn on color doppler for these images??
I agree with your Dx, Doc. Wish you could be able to map the camel hump with tissue doppler as well.

I have posted a pediatric image in the pediatric usound commnities section..check it out when you have time.

Thank you for your exciting postings

Bashir
Dormedary Hump – usually I overlook it in my practice.
Though it is benign – but we have to evaluate it with attention.
Thanks for refresh me!
Unfortunately,the diagnosis is 100% wrong.these two images show kidneys with HYPERTROPHIED COLUMN OF BERTIN--Which can be confused with a mass at mid pole,is common in left kidneys.The size must be less than 3cm,if it is more than 3cm it must always be evaluated for a mass by color doppler followed by CT scan or FNA/BIOPSY.
Whereas dormedary hump is another normal varient of kidneys which is more frequently present in left kidney and also more incidence in female.It is prominent bluding from anterior wall of cortex of lower pole.
ref; extra mass of normal tissue found only on the lateral portion of the left kidney
normal variant
"It's not a tumor."
- Arnold Schwartzenegger in Kindergarten Cop
Brian Funaki, MD - 6 February 1995.

Last updated: 1 September 2006
dromedary hump,
a bulge on the lateral surface of a kidney (usually the left), resembling the hump of a dromedary camel, seen in persons whose spleen or liver presses down.
Mosby's Medical Dictionary, 8th edition. © 2009, Elsevier.






Dr Md Azizul Islam said:
Dormedary Hump – usually I overlook it in my practice.
Though it is benign – but we have to evaluate it with attention.
Thanks for refresh me!
http://upload.wikimedia.org/wikipedia/commons/thumb/4/43/07._Camel_...






Syed Amir Gilani said:
Unfortunately,the diagnosis is 100% wrong.these two images show kidneys with HYPERTROPHIED COLUMN OF BERTIN--Which can be confused with a mass at mid pole,is common in left kidneys.The size must be less than 3cm,if it is more than 3cm it must always be evaluated for a mass by color doppler followed by CT scan or FNA/BIOPSY.
Whereas dormedary hump is another normal varient of kidneys which is more frequently present in left kidney and also more incidence in female.It is prominent bluding from anterior wall of cortex of lower pole.
ref; extra mass of normal tissue found only on the lateral portion of the left kidney
normal variant
"It's not a tumor."
- Arnold Schwartzenegger in Kindergarten Cop
Brian Funaki, MD - 6 February 1995.

Last updated: 1 September 2006
http://www.ajronline.org/cgi/content/full/188/5/1380
here is link of a good study about it.





Bashir H Samma;MD,PGD&C,SrMAIUM said:
I agree with your Dx, Doc. Wish you could be able to map the camel hump with tissue doppler as well.

I have posted a pediatric image in the pediatric usound commnities section..check it out when you have time.

Thank you for your exciting postings

Bashir
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DOI:10.2214/AJR.06.0920
AJR 2007; 188:1380-1387
© American Roentgen Ray Society
Pictorial Essay

Renal Pseudotumors

Shweta Bhatt1, Gregory MacLennan2 and Vikram Dogra1
1 Department of Radiology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Box 648, Rochester, NY 14642.
2 Department of Pathology, Case Western Reserve University, Cleveland, OH.

Received July 24, 2006; accepted after revision October 11, 2006.


Address correspondence to V. Dogra (vikram_dogra@urmc.rochester.edu).


Abstract
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

OBJECTIVE. Renal cell carcinoma is the most common malignant tumor to involve the kidneys; however, a number of other entities—called renal pseudotumors—may mimic renal neoplasms on imaging. This article presents the imaging features and pathologic correlation of some of the common and uncommon renal pseudomasses.

CONCLUSION. Many renal lesions look similar to renal cell carcinoma on radiologic imaging. The imaging features of renal pseudotumors presented in this article will help radiologists to identify them and to triage these patients for appropriate management.

Keywords: genitourinary imaging • kidney disease • renal disease


Introduction
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

Renal neoplasm is a common occurrence that is easily diagnosed using routine imaging. However, less is known about the lesions that mimic a renal neoplasm on imaging yet are proven at subsequent surgery and histopathology to be a wrong radiologic diagnosis. Such masses may be composed of normal or benign renal tissue and are referred to as renal pseudotumors. "Although common lesions such as abscesses and renal cysts may be confidently diagnosed on imaging, atypical presentations of such common entities and certain uncommon entities may simulate renal neoplasms and may lead to an unnecessary resection because of the concern for renal malignancy" [1].

This article presents the imaging features and pathologic correlation of some of the common and uncommon renal pseudomasses such as splenorenal fusion, renal pelvic hematomas, xanthogranulomatous pyelonephritis, extramedullary renal hematopoiesis, and arteriovenous malformation.

Renal pseudotumors may be categorized as developmental, infectious, granulomatous, and vascular in nature (Appendix 1).


APPENDIX 1 : Types of Renal Pseudotumors

Developmental
Prominent columns (septa) of Bertin
Persistent fetal lobulation
Dromedary hump
Splenorenal fusion
Cross-fused renal ectopia
Infectious
Abscess
Pyelonephritis
Scarred kidney
Granulomatous
Xanthogranulomatous pyelonephritis
Sarcoidosis
Malakoplakia
Tuberculosis
Vascular
Extramedullary hematopoiesis
Arteriovenous malformation
Renal pelvic hematomas
Anticoagulant-induced subcapsular hemorrhage
Miscellaneous
Regenerating nodule after reflux



Developmental Renal Pseudotumors
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

Prominent Columns of Bertin
Prominent (or hypertrophied) columns of Bertin (also known as "septa of Bertin") is a normal variant of the kidney formed of hyper-trophied cortical tissue located between the pyramids that projects into the renal sinus, resulting in splaying of the sinus. Hypertrophied but otherwise normal renal tissue not only distorts the renal sinus but can also result in what appear to be bizarre or disorganized calyces on excretory urography or CT urography because the papillae are not situated in the typical radial orientation. Columns of Bertin is usually located in the middle third of the kidney, more commonly the left kidney than the right [2]. Unusually large or atypical presentation of the prominent columns (septa) of Bertin on sonography may lead to further imaging, such as CT or MRI of the kidneys, to rule out an intrarenal tumor (Fig. 1A, 1B, 1C). Some sonographic features described in the literature that are suggestive of, but not specific for, a prominent columns (septa) of Bertin include "indentation on the renal sinus by the lesion, splitting of the sinus, well defined and distinct from the renal sinus, in continuity with the adjacent renal cortex, with similar echogenicity as that of adjacent renal cortex, engulfment of the papilla, and a cortical projection due to extension of the junctional parenchyma medially in the kidney" [3]. Although most people believe that the columns of Bertin has similar echogenicity to the adjacent renal cortex, according to Yeh et al. [4] a true columns of Bertin appears more echogenic than the normal renal cortex as a result of the anisotropic effect [5]. Because of the nonspecific nature of the previously described sonographic findings, patients with an atypical sonographic appearance or unusually large and prominent columns (septa) of Bertin are usually followed up with contrast-enhanced CT or MRI. Prominent columns (septa) of Bertin can be confirmed by showing its enhancement (perfusion) to be similar to that of surrounding renal parenchyma on contrast-enhanced CT, MRI, or contrast-enhanced sonography.




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Fig. 1A —46-year-old man with hypertrophied columns (septa) of Bertin. (Reprinted with permission from Paspulati RM, Bhatt S. Sonography in benign and malignant renal masses. Ultrasound Clinics 2006; 1:25-41 [2]) Longitudinal gray-scale sonogram of left kidney shows large hypertrophied columns of Bertin (arrows) located in middle third of kidney. It is continuous with normal renal cortex, and smooth renal surface overlies this pseudotumor.



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Fig. 1B —46-year-old man with hypertrophied columns (septa) of Bertin. (Reprinted with permission from Paspulati RM, Bhatt S. Sonography in benign and malignant renal masses. Ultrasound Clinics 2006; 1:25-41 [2]) Follow-up MRI was performed to rule out renal tumor. T1-weighted fat saturated (B) and gadolinium-enhanced (C) images of kidneys confirm presence of hypertrophied columns of Bertin (arrows), which shows similar signal intensity and identical homogeneous enhancement as that of normal renal cortex.



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Fig. 1C —46-year-old man with hypertrophied columns (septa) of Bertin. (Reprinted with permission from Paspulati RM, Bhatt S. Sonography in benign and malignant renal masses. Ultrasound Clinics 2006; 1:25-41 [2]) Follow-up MRI was performed to rule out renal tumor. T1-weighted fat saturated (B) and gadolinium-enhanced (C) images of kidneys confirm presence of hypertrophied columns of Bertin (arrows), which shows similar signal intensity and identical homogeneous enhancement as that of normal renal cortex.

Dromedary Hump
Dromedary hump appears as a focal bulge on the lateral border of the left kidney (Fig. 2). It forms as a result of the adaptation of the kidney to the adjacent spleen. It can usually be easily diagnosed on sonography and has the same perfusion as the surrounding renal parenchyma on contrast-enhanced sonography [6].



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Fig. 2 —25-year-old man with dromedary hump. Longitudinal gray-scale sonogram of left kidney shows presence of focal bulge (arrow) on lateral border of left kidney that has similar echotexture as adjacent renal cortex. Adjacent spleen (SP) is visualized, which is causing impression on kidney. (Reprinted with permission from Paspulati RM, Bhatt S. Sonography in benign and malignant renal masses. Ultrasound Clinics 2006; 1:25-41 [2])

Persistent Fetal Lobulation (Lobation)
The fetal kidneys are subdivided into lobes that may be separated by grooves. This lobulation usually diminishes by the end of the fetal period. Sometimes these lobulations persist into adulthood, and if not correctly identified, may be misdiagnosed as a renal tumor or a scarred kidney. Lobulation is characterized on sonography by the presence of renal surface indentations that overlie the space between the pyramids (Fig. 3), as compared with true renal scars, which are located overlying the medullary pyramids. Radiologically, persistent fetal lobulation of the kidney can be confirmed by documenting the presence of a renal pyramid in the bulge bounded by septa of Bertin on either side [3]. Scars related to renal infarcts are typically situated between pyramids. However, their focal nature usually allows them to be differentiated from fetal lobulations.



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Fig. 3 —32-year-old man with persistent fetal lobulation. Longitudinal gray-scale sonogram of right kidney shows sharp indentation (arrow) overlying space between pyramids. Resultant focal bulge on renal surface mimics renal tumor and should be carefully scanned to confirm presence of normal renal tissue within it.

Splenorenal Fusion
Splenorenal fusion is a rare benign entity; to our knowledge, only six cases of developmental splenorenal fusion have been described in the literature. Splenorenal fusion refers to the presence of heterotopic splenic tissue in the renal capsule. It may arise as a developmental anomaly secondary to the fusion of nephrogenic mesoderm and splenic anlage in the second month of gestation [7]. It may also be secondarily acquired as a result of splenosis after trauma or splenectomy, and the presence of a renal mass in such patients should raise the suspicion of splenosis.
Splenorenal fusion usually involves the left kidney, but its presence on the right side has also been documented. Patients usually present with an asymptomatic mass or, rarely, with symptoms of hypersplenism (anemia). On CT or gadolinium-enhanced MRI, splenorenal fusion appears as a solid enhancing mass arising from the kidney (Figs. 4A, 4B, 4C and 4D); a 99mTc sulfur colloid scan is confirmatory and shows uptake by the splenic tissue. Fine-needle aspiration biopsy or ferumoxides-enhanced MRI [8] may also be useful to confirm the diagnosis. Pathologically, the lesion consists of hemorrhagic-appearing tissue in the renal capsule, but it is distinctly separate from the adjacent normal renal parenchyma [1] (Fig. 4E).




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Fig. 4A —53-year-old woman with splenorenal fusion. Axial T1-weighted (A) and coronal T2-weighted (B) MRI images of kidneys show well-defined mass (arrow) in lower pole of left kidney, which is hypointense on T1-weighted and has intermediate signal on T2-weighted images. Multiple renal cysts are also present bilaterally.



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Fig. 4B —53-year-old woman with splenorenal fusion. Axial T1-weighted (A) and coronal T2-weighted (B) MRI images of kidneys show well-defined mass (arrow) in lower pole of left kidney, which is hypointense on T1-weighted and has intermediate signal on T2-weighted images. Multiple renal cysts are also present bilaterally.



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Fig. 4C —53-year-old woman with splenorenal fusion. Axial (C) and coronal (D) gadolinium-enhanced images of kidneys show intense enhancement of mass (arrow), simulating renal cell carcinoma.



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Fig. 4D —53-year-old woman with splenorenal fusion. Axial (C) and coronal (D) gadolinium-enhanced images of kidneys show intense enhancement of mass (arrow), simulating renal cell carcinoma.



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Fig. 4E —53-year-old woman with splenorenal fusion. Gross specimen of left kidney after nephrectomy reveals mass consists of hemorrhagic-appearing splenic tissue (SP) in renal capsule but sharply demarcated from adjacent renal parenchyma (K), confirming splenorenal fusion. (Reprinted with permission from Tynski Z, MacLennan GT. Renal pseudotumors. J Urol 2005; 173:600 [1].


Infectious Renal Pseudotumors
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

Focal Pyelonephritis
Renal infection confined to a single lobe is called focal pyelonephritis (Fig. 5). Renal infection involving multiple lobes of the kidney is referred to as multifocal pyelonephritis. It is more common in patients with diabetes and those who are immunocompromised. Patients typically present with flank pain, fever with chills, and pyuria. Focal pyelonephritis is seen on sonography as either a hypoechoic or hyperechoic lesion in the renal cortex extending from the renal medulla to the renal capsule, with decreased perfusion on color-flow Doppler imaging. CT shows a focal wedge-shaped area of low attenuation without a well-defined wall around it, and without an overlying bulge on the renal surface, which distinguishes it from renal cell carcinoma. Striations may also be observed in the nephrogram. Renal cortical scintigraphy, using 99mTc-labeled glucoheptonate or dimercaptosuccinic acid (DMSA), is more sensitive and specific for focal pyelonephritis than any other imaging technique and shows a focal cortical defect in the kidney [9]. Newer sonography techniques, such as tissue harmonic imaging, pulse inversion harmonic imaging, and contrast-enhanced sonography, may also be useful in the early detection of focal pyelonephritis [10].



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Fig. 5 —35-year-old woman with focal pyelonephritis. Contrast-enhanced CT scan of kidneys shows focal hypoattenuating lesion (arrowheads) in right kidney with decreased contrast enhancement. Absence of distinct wall around lesion and clinical information suggestive of infection are helpful in distinguishing this lesion from renal tumor.

Extension of the acute inflammatory process into the perirenal soft tissues may give the appearance of a renal malignancy. Some infiltrative renal tumors (particularly medullary renal carcinoma) may have an appearance similar to that of focal pyelonephritis. In such cases, clinical information can be helpful in making a diagnosis.
Renal Abscess
Renal abscesses are primarily caused by an ascending infection from the lower urinary tract with gram-negative bacilli and enteric bacteria, such as Escherichia coli, Klebsiella species, and Proteus species. Sonography and CT reveal a well-defined heterogeneous mass (Figs. 6A and 6B) that at times may simulate a renal malignancy. Features such as irregular walls with increased through-transmission on sonography and a low-attenuation lesion with enhancing walls on CT, along with a history of fever and a positive urinalysis and culture, indicate a renal abscess [11]. Differentiation from a renal malignancy may be difficult if clinical information does not support the presence of infection. Pathologically, renal abscess is identified by the presence of pus and debris with varying degrees of reactive inflammatory changes (Fig. 6C).




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Fig. 6A —36-year-old man with left renal abscess. Longitudinal gray-scale sonogram of left kidney shows well-defined hypoechoic mass (arrow) near mid region of kidney.



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Fig. 6B —36-year-old man with left renal abscess. Corresponding contrast-enhanced CT scan of kidneys shows low-attenuation mass (arrow) in mid region of left kidney simulating renal cell carcinoma.



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Fig. 6C —36-year-old man with left renal abscess. Gross specimen of kidney shows presence of pus and debris in lesion, consistent with abscess (arrowheads).

Scarred Kidney
Severely scarred kidney secondary to infectious processes such as pyelonephritis or renal infarcts may also present as a potential pseudotumor on imaging. Regions of preserved parenchyma may appear masslike on sonography or even in the nephrographic phase of CT and MRI. Appropriate corticomedullary differentiation in the early phases of enhancement on CT or MRI may be required to exclude a mass.

Granulomatous Renal Pseudotumors
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

Xanthogranulomatous Pyelonephritis (XGP)
XGP is a rare inflammatory condition usually secondary to chronic obstruction caused by nephrolithiasis and resulting in infection and irreversible destruction of the renal parenchyma. XGP is associated with a staghorn calculus in approximately 70% of cases. Patients with diabetes are particularly predisposed to the formation of XGP. XGP may rarely present with the classic urographic triad of unilaterally decreased or absent renal excretion, staghorn calculus, and diffuse renal enlargement [12]. XGP may present in a diffuse or focal pattern. Focal or segmental XGP is more likely to mimic renal cell carcinoma on imaging because of its radiologic similarities, which often result in its resection.

Establishing a definite preoperative diagnosis only on the basis of imaging in both focal and diffuse forms of XGP is difficult. Sonographically, XGP may appear as single or multiple hypoechoic areas in the parenchyma of an enlarged kidney, with central echogenic foci representing calculi. Sonographic findings are nonspecific but can nevertheless suggest a diagnosis of XGP. Although not confirmatory, CT evaluation can be considered helpful in the presence of features such as abscess replacing the renal parenchyma, with low-attenuation areas (lipid-rich xanthogranu-lomatous tissue) and calcification in the mass [13] (Figs. 7A and 7B). If calculi are not present, focal XGP with a low-attenuation area in the renal parenchyma may suggest a diagnosis of renal tumor. MRI has no advantage over CT and is usually not performed.




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Fig. 7A —47-year-old woman with xanthogranulomatous pyelonephritis (XGP). Contrast-enhanced CT scans of kidneys show enlarged right kidney with focal area of hypodensity (white arrow, A). Also seen is presence of calculus (arrowhead, B) and part of stent (black arrow, A) in right renal pelvis.



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Fig. 7B —47-year-old woman with xanthogranulomatous pyelonephritis (XGP). Contrast-enhanced CT scans of kidneys show enlarged right kidney with focal area of hypodensity (white arrow, A). Also seen is presence of calculus (arrowhead, B) and part of stent (black arrow, A) in right renal pelvis.

Pathologically, XGP is composed of multiple inflammatory cells, both acute and chronic, and xanthoma cells, which are lipidladen foamy macrophages that impart their yellow color to the mass [1] (Figs. 7C, 7D and 7E).



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Fig. 7C —47-year-old woman with xanthogranulomatous pyelonephritis (XGP). Surgical specimen of kidney (K in C) shows focal XGP (C) and necrotic debris (D). Debris was originally in cavity seen in C.



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Fig. 7D —47-year-old woman with xanthogranulomatous pyelonephritis (XGP). Surgical specimen of kidney (K in C) shows focal XGP (C) and necrotic debris (D). Debris was originally in cavity seen in C.



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Fig. 7E —47-year-old woman with xanthogranulomatous pyelonephritis (XGP). Microscopic slide shows abundant lipid-laden macrophages (arrowheads), xanthoma cells, with multiple acute and chronic inflammatory cells. (H and E, x40) (Reprinted with permission from Tynski Z, MacLennan GT. Renal pseudotumors. J Urol 2005; 173:600 [1])

Other Granulomatous Renal Pseudotumors
Sarcoidosis and malakoplakia are other rare granulomatous mass lesions that mimic a renal malignancy.
Sarcoidosis—Sarcoidosis is a multisystem disorder with varied extrapulmonary symptoms. In the United States, sarcoidosis is more common in the African American population, with age-adjusted annual incidence rates of 35.5 per 100,000 for African Americans and 10.9 per 100,000 for whites [14].

The disorder is characterized by the presence of noncaseating granulomas in multiple organs of the body [15]. Renal sarcoidosis can present in several ways, most commonly as aberrant calcium metabolism, including hypercalcemia, hypercalciuria (seen in 15-62% patients) [16], and nephrocalcinosis. Granulomatous involvement of the kidney has been reported in 7-22% of patients with sarcoidosis at autopsy, but radiographically distinct renal granulomas are rarely seen. Radiographically distinct lesions appear on contrast-enhanced CT as multiple small (2-3 cm), low-attenuation nodular masses in the renal parenchyma that simulate renal lymphoma or metastasis. Diffuse granulomatous infiltration of the kidney is a more rare radiologic finding than multiple nodules. Differentiation is usually done on the basis of the clinical setting, such as African American race and sickle cell trait, which favor sarcoidosis.

Granulomatous involvement of the kidney may also cause interstitial nephritis, which appears as a striated nephrogram on contrast-enhanced CT [17]. Biopsy is the only way to confirm the diagnosis. PET may show increased 18F-FDG uptake by sarcoidosis, which, along with clinical information and the new radiotracers such as fluoro--methyltyrosine, may be helpful in distinguishing renal sarcoidosis from malignant disease of the kidney [18].

Malakoplakia—Malakoplakia of the kidney is a rare inflammatory disorder related to defective macrophage function and is characterized by the deposition of soft, yellow-brown plaques in the kidney [13]. There is usually an underlying urinary tract infection that results in the formation of plaques in the bladder and the kidney. Radiologically, malakoplakia may appear as an enlarged kidney, a low-attenuation mass, or a diffuse infiltrative disease. Radiologic findings in renal malakoplakia are nonspecific and suggest an alternate diagnosis such as a renal tumor. Isolated renal malakoplakia without the presence of concurrent lower urinary tract involvement is rare and is more likely to be mistaken for a renal malignancy on radiologic studies. Diagnosis of malakoplakia is confirmed by histology. Microscopically, the presence of Michaelis-Gutmann bodies is pathognomonic of malakoplakia.


Vascular Renal Pseudotumors
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

Arteriovenous Malformation (AVM)
AVM may be congenital or acquired, with the most common cause being trauma. Other causes are surgery, tumors, or idiopathic. Arteriovenous fistulas comprise 70-80% of AVMs in the kidney [19]. Renal AVMs may be intraparenchymal or in the renal sinus (Fig. 8A), and therefore may be difficult to distinguish from a renal malignancy such as renal cell carcinoma or transitional carcinoma on contrast-enhanced CT because both these lesions will show enhancement. Sonography can exclude the possibility of a solid mass by showing anechoic spaces in the lesion that fill with color on color-flow Doppler sonography. A mass can be confirmed to be an AVM when a typical arteriovenous flow pattern is depicted in the lesion (Figs. 8B and 8C). MRI can also be useful in differentiating an AVM from a malignancy by showing internal flow voids in the lesion. Gadolinium-enhanced MRI can confirm an AVM during early arterial phase imaging, where it reveals the presence of abnormal tortuous vessels and an early draining vein characteristic of an AVM.




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Fig. 8A —35-year-old man with renal arteriovenous malformation. Nephrographic phase of contrast-enhanced CT scan of kidneys in this patient with no history of trauma or biopsy shows enhancing lesion in renal pelvis (arrowheads).



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Fig. 8B —35-year-old man with renal arteriovenous malformation. Subsequent gray-scale (B) and color Doppler (C) sonograms reveal anechoic structures (arrows, B) in renal pelvis (excluding possibility of solid mass), which fill with color, showing mosaic color-flow pattern with high-velocity, low-impedance pulsatile flow, which is consistent with vascular malformation rather than solid neoplasm.



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Fig. 8C —35-year-old man with renal arteriovenous malformation. Subsequent gray-scale (B) and color Doppler (C) sonograms reveal anechoic structures (arrows, B) in renal pelvis (excluding possibility of solid mass), which fill with color, showing mosaic color-flow pattern with high-velocity, low-impedance pulsatile flow, which is consistent with vascular malformation rather than solid neoplasm.

Subepithelial Renal Pelvic Hematoma
Renal hemorrhage can occur secondary to anticoagulant therapy or vasculitis and may form hematomas either in the perirenal soft tissues or in the renal pelvis. Subepithelial renal pelvic hematomas are also called Antopol-Goldman lesions [20]. These are rare lesions that usually present with hematuria and flank pain. To our knowledge, only 28 cases have been described in the literature, of which only one was managed conservatively. On CT, these hematomas appear as nonenhancing heterogeneously dense or hyperdense masses in the renal pelvis that may cause extrinsic luminal narrowing (Figs. 9A, 9B, 9C). They closely mimic renal pelvic malignancy; the correct diagnosis is revealed in most cases only after nephrectomy (Fig. 9D). Awareness of and a high index of suspicion for an Antopol-Goldman lesion can avoid an unnecessary nephrectomy, especially in patients with a nonenhancing renal pelvic mass causing extrinsic compression on the collecting system who have an underlying history of coagulopathy.



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Fig. 9A —35-year-old woman with subepithelial renal pelvic hematomas. Unenhanced CT scan of kidneys shows heterogeneous mass (arrow) in left renal hilum.



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Fig. 9B —35-year-old woman with subepithelial renal pelvic hematomas. Corresponding scan during corticomedullary phase of kidneys shows no enhancement of this heterogeneous mass (arrow).



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Fig. 9C —35-year-old woman with subepithelial renal pelvic hematomas. Excretory phase scan shows mass effect on collecting system due to left renal hilar mass (arrow).



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Fig. 9D —35-year-old woman with subepithelial renal pelvic hematomas. Cut section of surgically removed kidney shows multiple organizing hematomas (arrow) and thromboemboli (arrowhead) in hilar adipose tissue. Pathologic examination showed mass to be subepithelial renal pelvic hematomas secondary to vasculitis.

Extramedullary Hematopoiesis
Extramedullary hematopoiesis is a reactive process in response to the failure of hematopoiesis in the bone marrow. It commonly occurs in the spleen, liver, and lymph nodes; extramedullary hematopoiesis at other sites such as the pleura, kidneys, gastrointestinal tract, breast, skin, brain, and adrenal glands is uncommon. It commonly occurs in the presence of myelofibrosis with myeloid metaplasia (most frequent), chronic myeloproliferative disorder, polycythemia vera, and essential thrombocytosis. The presence of a renal mass in association with any of these disorders should raise the possibility of an extramedullary hematopoiesis.
Extramedullary hematopoiesis in the kidney occurs in three forms: parenchymal, intrapelvic, and perirenal [21]. A parenchymal type of renal involvement appears as a diffuse enlargement of the kidney or as either single or multiple small focal lesions. Pelvic involvement is either an extension of parenchymal involvement or is isolated. In the perirenal type of renal extramedullary hematopoiesis, a single hypoattenuating mass or multiple nodules may be seen either around or completely encasing the kidneys [22] (Figs. 10A, 10B and 10C). Biopsy confirmation is usually required in extramedullary hematopoiesis (Fig. 10D) to help to differentiate it from lymphoma or urothelial tumors, which are often the first diagnoses in such patients [21]. But extramedullary hematopoiesis should be considered high in the differential diagnosis when a renal mass or masses are present in association with the previously mentioned hematologic disorders.




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Fig. 10A —82-year-old woman with renal extramedullary hematopoiesis. Axial (A) and coronal (B) unenhanced CT scans of right kidney show multiple perirenal masses (arrowheads) with severe splenomegaly (SP).



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Fig. 10B —82-year-old woman with renal extramedullary hematopoiesis. Axial (A) and coronal (B) unenhanced CT scans of right kidney show multiple perirenal masses (arrowheads) with severe splenomegaly (SP).



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Fig. 10C —82-year-old woman with renal extramedullary hematopoiesis. Axial CT scan of pelvis at bone window setting shows coarsening of bone matrix and thinning of cortices, which are suggestive of extramedullary hematopoiesis.



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Fig. 10D —82-year-old woman with renal extramedullary hematopoiesis. Microscopy is characterized by presence of megakaryocytes (red arrow) (confirmation by positive immunostaining for factor VIIIra) and granulocyte precursors (blue arrow) (confirmation by positive Leder staining). Presence of these blood cell precursors suggests hematopoietic process in these masses. These microscopic features are confirmatory for extramedullary hematopoiesis. (H and E, x40)

Other entities that may present as renal pseudotumors but are not discussed in this article include crossed fused renal ectopia, renal tuberculosis, anticoagulant-induced subcapsular hemorrhage, and regenerating nodule after reflux.

Conclusion
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

Many renal lesions may mimic renal cell carcinoma on radiologic imaging. However, a high index of suspicion for renal pseudotumors as illustrated in this article may help avoid unnecessary additional imaging and urologic interventions.
































References
Top
Abstract
Introduction
Developmental Renal Pseudotumors
Infectious Renal Pseudotumors
Granulomatous Renal Pseudotumors
Vascular Renal Pseudotumors
Conclusion
References

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