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PEARLS OF WISDOM
Year : 2006  |  Volume : 22  |  Issue : 3  |  Page : 272-274
 

Pseudotumor in chronic renal failure: Diagnostic relevance of radioisotope scan


Department of Urology, Post Graduate Institute of Medical, Education and Research, Chandigarh, India

Correspondence Address:
S K Singh
Department of Urology, Post Graduate Institute of Medical, Education and Research, Chandigarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-1591.27642

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Keywords: Pseudotumor, renal scan, tubulointerstitial nephritis


How to cite this article:
Mandal AK, Garg S, Acharya N, Singh S K. Pseudotumor in chronic renal failure: Diagnostic relevance of radioisotope scan. Indian J Urol 2006;22:272-4

How to cite this URL:
Mandal AK, Garg S, Acharya N, Singh S K. Pseudotumor in chronic renal failure: Diagnostic relevance of radioisotope scan. Indian J Urol [serial online] 2006 [cited 2019 Sep 15];22:272-4. Available from: http://www.indianjurol.com/text.asp?2006/22/3/272/27642



   Introduction Top


Solid renal masses are usually malignant and are treated by either radical nephrectomy or nephron-sparing surgery, depending on their size. Occasionally, pseudotumor of the kidney has not been diagnosed preoperatively and the patients have undergone nephrectomy unnecessarilly.[1] Different imaging modalities, in combination have been advocated to avoid embarrassment of having removed the kidney without any sinister lesion. Application of contrast enhanced computed tomography (CECT) might be limited due to concomitant renal failure. Radionuclide study may aid in the differentiation of pseudotumor from malignant mass. Had we paid attention to the radioisotope scan performed preoperatively, the undesirable nephrectomy could have been avoided.


   Case Report Top


A 49-year-old hypertensive man with chronic renal failure (CRF) was detected to have a solid renal mass on routine ultrasonography. His hemoglobin was 9.1 gm/dl, total leucocyte count 8900/mm 3, blood urea 60 mg/dl and serum creatinine 4.5 mg/dl. His blood sugar, serum calcium, inorganic phosphate and liver function tests were normal. Urinalysis was unremarkable. Chest roentgenogram was unremarkable. Both kidneys showed increased cortical echogenicity with loss of corticomedullary differentiation and compact pelvi-calyceal system on ultrasonography. The right kidney was 7.1 cm and left 7.4 cm in length. A well-defined exophytic homogeneous soft tissue mass was seen occupying the interpolar and lower polar region of the left kidney. Noncontrast computed tomography (NCCT) of abdomen revealed 6 5 cm hypodense mass, occupying the major part of the left kidney [Figure - 1]. Considering his high serum creatinine, CECT was not done. The mass on color-flow Doppler ultrasonography showed increased blood flow suggestive of malignant lesion. Renogram was performed to assess the contribution of the left kidney in total renal function and therefore to assess the impact of removal of the affected kidney on overall renal function. The renal scan showed relatively better uptake in the region of the mass lesion, whereas the remaining part of the left kidney and the right kidney showed negligible uptake with diffuse background activity consistent with CRF [Figure - 2]. Although the possibility of a benign lesion was considered preoperatively, the findings of the exophytic solid renal mass with increased vascularity on Doppler ultrasonography weighed over the findings on the renogram and a malignant lesion was suspected. The preoperative fine-needle aspiration biopsy was not considered in view of high false negativity. The patient underwent exploration extraperitoneally through bed of the 12th rib and left nephrectomy was performed. The mass involved almost the whole of the left kidney and therefore nephron-sparing surgery was technically not feasible. After closure of the incision, the patient was made supine and Tenckhoff catheter was placed for continuous ambulatory peritoneal dialysis (CAPD). Postoperatively, the patient's serum creatinine was elevated to 9 mg% and he underwent hemodialysis on the fifth postoperative day. Continuous ambulatory peritoneal dialysis was initiated after two weeks. The mass was homogeneous on cut section. Histopathological examination of the mass revealed scattered sclerosed glomeruli, dense interstitial inflammation with aggregates of lymphocytes, monocytes and plasma cells concentrated throughout the interstitium with foci of atrophic tubules, fibrinoid necrosis in the vessels and focal lymphohistiocytic giant cells. The epithelium of damaged tubules showed necrosis and degeneration. The histological findings were consistent with the diagnosis of tubulointerstitial nephritis with no evidence of malignancy [Figure - 3]. The patient is on regular CAPD and is well at six months of follow-up.


   Discussion Top


Tubulointerstitial nephritis rarely present as focal mass lesion in the kidney. Common benign lesions posing as tumors include focal xanthogranulomatous pyelonephritis, hilar lip, hypertrophied column of Bertin, renal malakoplakia, chronic pyelonephritis and renal tuberculosis etc.[2] Rarely, inflammatory myofibroblastic lesion may also pose as pseudotumor.[3] The other benign tumors which commonly cause a preoperative dilemma are oncocytoma, angiomyolipoma, metanephric adenoma etc. Tubulointerstitial nephritis (TIN) accounts for 4.2% of patients with CRF. Clinical manifestations of TIN depend on the degree of involvement, the tubular sites involved and the level of compensation that the uninvolved areas provide.[4] This level of compensation and hypertrophy may occasionally result in the formation of the pseudotumor.

More than 90% of solid renal masses are malignant and in practice, all solid renal masses are considered malignant unless proved otherwise. On the other hand, it is imperative on the part of the urologist not to operate on a patient with renal pseudotumor presenting with renal mass. Different imaging modalities, like CECT, magnetic resonance imaging (MRI) and renal scan, have been analyzed to overcome such situations. CECT most often easily differentiates pseudotumors from true renal tumors; however, it has its own limitations.[5] It is avoided in cases with renal failure, which may get worsened due to contrast. Moreover, because of poor functioning of the kidney the contrast excretion is suboptimal yielding poor quality films.[6] In such trying situations, MRI with gadolinium administration is helpful because gadolinium is less nephrotoxic and causes few anaphylactoid reactions. We had supplemented NCCT with color Doppler ultrasonography and were carried away by finding solid renal mass on NCCT and increased vascularity of the mass on color Doppler ultrasonography, a feature of malignant lesion.[7] The finding of the renal scan showing uptake in the area of the lesion was not given due importance. This would have clinched the diagnosis, as the malignant tumors are not "Hot" on scan.[1] Fine-needle biopsies are of limited value in the diagnosis of obvious renal masses, the major problem being the high negative rate in renal malignancy. Nondiagnostic biopsies ultimately rely on radiology for excision.[8],[9]

 
   References Top

1.Felson B, Moskowitz M. Renal pseudotumors. The regenerated nodule and other lumps, bumps and dromedary humps. Am J Roent Rad Ther Nucl Med 1969;107:720-9.  Back to cited text no. 1  [PUBMED]  
2.Lopez FA. Renal pseudotumors. Am J Roent Rad Ther Nucl Med 1970;109:172-84.   Back to cited text no. 2  [PUBMED]  
3.Kapusta LR, Weiss MA, Ramsay J, Lopez-Beltran A, Srigley JR. Inflammatory myofibroblastic tumors of kidney: A clinicopathologic and immunohistochemical study of 12 cases. Am J Surg Pathol 2003;27:658-66.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Goldfarb D. Etiology, pathogenesis and management of renal failure. In : Walsh PC, Retik AS, editors. Campbell's Urology, 7th ed. Saunders: Philadelphia; 1998. p. 286-340.  Back to cited text no. 4    
5.Israel GM, Bosniak MA. How I Do It: Evaluating renal masses. Radiology 2005;236:441-50.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Choyke PL. Detection and staging of renal cancer. Magn Reson Imaging Clin N Am 1997; 5:29-47.  Back to cited text no. 6  [PUBMED]  
7.Erden I, Beduk Y, Karalezli G, Aytac S, Anafarta K, Safak M. Characterization of renal masses with color flow Doppler ultrasonography. Br J Urol 1993;71:661-3.   Back to cited text no. 7  [PUBMED]  
8.Herts BR, Baker ME. The current role of percutaneous biopsy in the evaluation of renal masses. Semin Urol Oncol 1995;13:254-61.  Back to cited text no. 8  [PUBMED]  
9.Singh JC, Kekre NS. Role of needle biopsy in solid renal masses: When does the pudding require a proof? Indian J Urol 2006;22:61-3.  Back to cited text no. 9    


    Figures

  [Figure - 1], [Figure - 2], [Figure - 3]

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