|Year : 2014 | Volume
| Issue : 3 | Page : 357-359
Renal arteriovenous malformation with inferior vena caval extension mimicking renal cell carcinoma
Anuj Deep Dangi1, Ramani Kumar2, Nitin S. Kekre1
1 Department of Urology, Christian Medical College, Vellore, Tamil Nadu, India
2 Department of Pathology, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Web Publication||1-Jul-2014|
Anuj Deep Dangi
Department of Urology, Christian Medical College, Vellore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
| Abstract|| |
A young lady presented with complaints of right flank pain and a palpable mass. On contrast-enhanced tomography (CECT), a renal mass with extension into the inferior vena cava (IVC) - suggestive of renal cell carcinoma - was diagnosed and she underwent radical nephrectomy with en bloc excision of the IVC thrombus. Histopathology revealed a benign arteriovenous malformation that had extended into the IVC. Arteriovenous malformation should therefore be kept in the list of differentials for a renal mass with IVC extension.
Keywords: Inferior vena cava thrombus, renal cell carcinoma, renal arteriovenous malformation
|How to cite this article:|
Dangi AD, Kumar R, Kekre NS. Renal arteriovenous malformation with inferior vena caval extension mimicking renal cell carcinoma. Indian J Urol 2014;30:357-9
|How to cite this URL:|
Dangi AD, Kumar R, Kekre NS. Renal arteriovenous malformation with inferior vena caval extension mimicking renal cell carcinoma. Indian J Urol [serial online] 2014 [cited 2019 Jul 21];30:357-9. Available from: http://www.indianjurol.com/text.asp?2014/30/3/357/134237
| Introduction|| |
Renal vascular malformations are rare lesions. We describe a patient with a renal arteriovenous malformation with extension into the inferior vena cava (IVC) that was diagnosed as a renal cell carcinoma with IVC thrombus. To the best of our knowledge, this is the first report of a renal arteriovenous malformation presenting as a palpable renal mass with IVC extension.
| Case report|| |
A 22-year-old female presented with fever off and on for 4 years and dull, aching, non-radiating pain in the epigastric and right loin region for 2 months. There was no associated hematuria. She complained of significant weight loss, mild loss of appetite and generalized weakness over the last 1 year. There was no history of hemoptysis, jaundice or bone pain. Examination revealed a thinly built young lady with normal blood pressure and no pallor, icterus, pedal edema, palpable lymph nodes or clubbing. Abdominal examination revealed a 15 × 12 × 12 cm ballotable lump in the right lumbar region that moved with respiration. There were no dilated superficial veins over the abdominal wall.
Blood investigations revealed a hematocrit of 34%, ESR of 20 mm in the first hour, platelet count of 126,000 with giant platelets on the smear and normal renal and liver function tests. Urine microscopy and chest X-ray were normal. On contrast-enhanced computed tomography (CECT) of the abdomen and pelvis, an 8.5 × 8.4 cm heterogeneously enhancing renal mass with solid and cystic components was seen extending into the right renal vein and IVC below the hepatic segment [Figure 1]. On delayed images, it was seen extending into the pelvicalyceal system with resultant hydronephrosis. Posteriorly, fat planes were preserved between the tumor and the abdominal wall; medially, it was in relation to the uncinate process of pancreas (with infiltration considered unlikely) and laterally it was abutting segments 5 and 6 of the liver (where infiltration could not be excluded). There were no other visceral or lymph nodal lesions.
|Figure 1: Contrast-enhanced computed tomography (arterial phase and venous phase): Heterogeneously enhancing right renal mass with thrombus extension into the right renal vein and inferior vena cava|
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She underwent open right radical nephrectomy with IVC thrombectomy using a transperitoneal approach (Chevron incision). The tumor was removed en bloc with IVC thrombus. There were no enlarged lymph nodes. The post-operative course was uneventful.
Gross examination revealed a tumor measuring 9 × 8 × 7 cm with a firm white surface on cut section, displacing the entire kidney and abutting the renal pelvis. A 2 cm fleshy mass with cut surface similar to the tumor was seen to extend out of the renal vein without infiltrating it (IVC thrombus). Light microscopy findings are described in [Figure 2]a. The stromal cells were negative for HMB45 [Figure 2]b], SMA, CD34, Melan A, S-100 [Figure 3]a], EMA [Figure 3]b] and desmin on immunohistochemistry. Slides were reviewed by a second expert pathologist and the diagnosis of arteriovenous malformation of right kidney was confirmed.
|Figure 2: (a) Hematoxylin and eosin stain (X50): Renal tissue with variably angulated and dilated blood vessels, distributed in a copious hyaline fi brous matrix. The spindle cells in the stroma did not show any atypia or pleomorphism. (b) Human melanoma black 45 immunostaining (X200): Negative, rules out angiomyolipoma|
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|Figure 3: (a) S-100 immunostaining (X200): Negative, rules out neural lesions. (b) Epithelial membrane antigen immunostaining under X200: Negative, rules out epithelial lesions, e.g. carcinomas|
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She remained asymptomatic on follow-up for 2 years and there was no local recurrence on abdominal sonography. She has since married and has one child.
| Discussion|| |
Vascular malformations within the kidney are rare. They can be congenital, acquired or idiopathic.  Benign vascular lesions are classified as hemangiomas, lymphangiomas, vascular ectasias, reactive vascular malformations and glomus tumors. Hemangiomas are further divided into pyogenic granulomas, capillary and cavernous hemangiomas. Anatomically, they may arise from the arteriolar end, venous end or from capillaries, and have a variable amount of abnormal vessel density and mesenchymal tissue. These two facts account for their varied clinical, radiological and gross appearance. Initial presentation may include painful or painless hematuria, hypertension or symptoms due to massive arterio-venous shunting of blood such as cardiomegaly, congestive heart failure or bruit.  On cross-sectional imaging, they are seen as lesions of vascular density in the renal sinus and peripelvic areas with or without the presence of prominent renal vein.  In cases where there is a large volume of blood shunting taking place in the vascular malformation, the renal vein can be seen in the arterial phase itself.
Vascular malformations mimicking renal cell carcinoma have been described in the literature. , This is due to the fact that renal cell carcinomas themselves have abnormal vasculature resulting in shunting of blood.  The variable amount of stromal tissue in arteriovenous malformations also has a bearing on how they are seen on cross-sectional imaging. The typical homogenous appearance of vascular density may not be seen if there is a larger component of fibrous stroma. We hypothesize that the absence of bruit and pulsatility intra-operatively in this case could be attributed to this fact and the probable connection of abnormal vasculature with a low-pressure system (capillaries and venules). Renal angiography aids in diagnosis by delineating the vasculature of the malformation.  Treatment options (if required) range from embolization to partial or total nephrectomy. 
Our case is atypical on many counts. Palpable flank lesion with flank pain is a very unusual presentation for a renal vascular malformation. There was no history of hematuria, she was normotensive and there was no bruit. Investigations revealed normal urine microscopy. CECT revealed a mass that on arterial phase showed heterogeneous enhancement and had extension into the renal vein and infrahepatic IVC. Intraoperatively, we could not recognize it as an arteriovenous malformation as it was non-pulsatile and firm in consistency. On reviewing the CECT after the histopathology report was available, expert radiologists still felt that it was not possible to label the image as a vascular malformation of the kidney, although there were a few features not typical of renal cell carcinoma: The lesion was well encapsulated and showed heterogeneous enhancement in the region of 30-100 Hounsfield units (somewhat more than what would be expected for a typical RCC). It is a matter of conjecture whether this lesion would have responded to angio-embolization if identified pre-operatively, and this renal unit could have been saved.
| Acknowledgment|| |
Authors acknowledge Dr. Christopher Fletcher, Prof. of Pathology, Harvard Medical School, for reviewing the slides and confirming the diagnosis.
| References|| |
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[Figure 1], [Figure 2], [Figure 3]