Inflammatory Pseudotumor of the Renal Pelvis

Abstract

Background: Inflammatory pseudotumor of the kidney is a rare disease of unknown etiology. There are no specific clinical or radiologic findings. The lesion can mimic renal cell carcinoma or transitional cell carcinoma depending on the site of involvement. These tumors, if diagnosed correctly, may respond to medical management. We present a case in which an inflammatory pseudotumor of the renal pelvis was misdiagnosed as a transitional cell carcinoma and unwarranted surgical intervention was performed.

Case Presentation: A 39-year-old man presented with left flank pain and gross hematuria. On MRI, there was a hypointense 2.4 × 1.8 cm lesion involving the left renal pelvis. The urine cytology and biopsy of the lesion were inconclusive. On follow-up cans the lesion increased in size and patient had repeated hematuria. The lesion was clinically presumed to be a transitional cell carcinoma of the left renal pelvis. A laparoscopic left side nephroureterectomy along with bladder cuff excision and para-aortic lymphadenectomy was performed. The histology report revealed the lesion to be inflammatory pseudotumor of the renal pelvis.

Conclusion: Inflammatory pseudotumor should always be considered in differential diagnosis of pelvic tumors, especially when image findings and biopsies are inconclusive.

Introduction

Inflammatory pseudotumors are rare and commonly affect the lungs. Primary renal involvement is unusual and the isolated involvement of renal pelvis is extremely uncommon. We describe a case of an inflammatory pseudotumor of renal pelvis, which was misdiagnosed as a transitional cell carcinoma. The case highlights the problems associated with the diagnosis of these tumors as the signs, symptoms, and imaging characteristics mimic those of the more common renal malignancies.

Case Presentation

A 39-year-old man had history of pain in the left flank for 3 months with one episode of hematuria and clot retention, which was managed conservatively. His blood investigations were within normal limits except an elevated creatinine (1.6 mg/dL). There was history of knee arthroscopy in the past but no significant personal or familial history. He was a nonsmoker. The clinical examination was normal. MRI revealed a 2.4 × 1.8 cm lesion involving the left renal pelvis, which was hypointense on T2 weighted images. The lesion extended up to the pelviureteral junction and there was perilesional fat stranding along with mild hydronephrosis. The mass was inseparable from the cortex. There was no significant hilar or retroperitoneal lymphadenopathy and the contralateral kidney was normal (Fig. 1a, b).

FIG. 1.

(a) The axial images of the T2 weighted MRI scan showing the hypointense left renal pelvic mass (red arrow), (b) coronal T2 weighted image depicting the extension up to pelviureteral junction (red arrow) and mild hydronephrosis, (c) CT image showing the mildly enhancing mass (red arrow) with stent in situ, and (d) PET-CT image at the same level showing mild uptake in the mass.

A diagnostic left ureteroscopy was performed, which showed old clots in the ureter, but the ureteroscope could not be negotiated in the upper ureter. A ureteral barbotage was done and 4F Double-J stent was inserted with difficulty at the end of the procedure. The cytology of urine from the bladder and that of the ureteral washing was inconclusive. A percutaneous core biopsy of the mass was performed, which was also inconclusive. The creatinine decreased to 1.1 mg/dL. The patient wished for no active intervention at this time. A positron emission tomography-CT scan was performed after 4 weeks on which the mass showed a mild increase in size. It had heterogeneous contrast enhancement and a standardized uptake value of 3.5 (Fig. 1c, d). The patient again had an episode of gross painless hematuria. A bladder wash and clot evacuation was done along with removal of the stent. A ureteroscopy was repeated, but ureteroscope could not be negotiated in the pelvis.

The case was discussed in a multidisciplinary meeting. As the clinical picture and investigations were suggestive of a transitional cell carcinoma of renal pelvis, a transperitoneal laparoscopic left nephroureterectomy, bladder cuff excision, and para-aortic lymphadenectomy was performed. The left ureter was densely adherent to the para-aortic tissue and could be lifted with difficulty. There were inflammatory changes at the level of the hilum with a membrane-like tissue covering the hilar vasculature and pelvis. A lower polar accessory artery was identified and divided between clips. The main artery was seen in close relation to the posterior aspect of the renal vein (Fig. 2a–d). The plane between the artery and vein could not be developed satisfactorily and hence en mass division of the hilum was performed using a vascular stapler, after mobilization of the upper pole.

FIG. 2.

(a) The ureter being lifted away, (b) the membranous tissue covering the hilum and the pelvis, (c) the tissue anterior to the renal vein being dissected, (d) the left main renal artery (yellow arrow) seen behind the vein, the clips on the lower polar artery can also be seen.

On gross examination, the pelvis showed a grayish fibrotic lesion measuring 2.5 × 1.4 × 1 cm. On microscopic examination, the lesion showed dense chronic lymphoplasmacytic inflammation with fibrosis, sclerosis, and focal storiform pattern with areas of obliterative vasculitis suggestive of inflammatory pseudotumor (Fig. 3a, b). Immunohistochemical examination showed uptake with Kappa and Lambda confirming the presence of plasma cells. Congo red and IgG4 did not show any uptake ruling out the possibility of amyloidosis and IgG4 nephropathy. The ureter, bladder cuff, cut ends of renal arteries, vein and retroperitoneal nodes were unremarkable. The patient made an uneventful recovery and was discharged on the third postoperative day. His creatinine, at the third month of follow-up was 1.8 mg/dL, which decreased to 1.6 mg/dL at 6 months and remained at this level after that. The follow-up scan done at the end of 1 year was within normal limits. The patient is currently on follow-up and is doing well.

FIG. 3.

(a) Histopathologic image showing dense lymphoplasmacytic infiltrates with adjacent urothelium (hematoxylin and eosin, 10 × magnification), (b) prominent plasma cells (hematoxylin and eosin, 40 × magnification).

Discussion

Inflammatory pseudotumors commonly affect the lungs and are usually benign but can rarely be malignant. Renal inflammatory pseudotumors are uncommon, with only a few cases reported in the literature. The isolated involvement of renal pelvis is even more rare.¹ The etiology is unknown, but an association has been found with previous history of infection, autoimmune process, trauma, or surgery. The patients usually present with pain and hematuria.^1–3 On imaging, the lesions lack any specific characteristics and a high index of suspicion is needed to diagnose them. Ultrasonography examination usually shows a hypo- or hyperechogenic mass with increase vascularity on Doppler. On CT scan, mild enhancement is observed after contrast administration and there may be areas of calcification or necrosis. The lesions may be hypo- or hyperintensity on T2 weighted MRI images.² These features are similar to those found with renal cell carcinoma or transitional cell carcinomas, if the lesion is in the pelvicaliceal system like in our patient.⁴ It has been suggested that the lack of a capsule and the penetration of renal arteries in the tumor without encasement may be the subtle pointers to differentiate them from renal cell carcinoma and transitional cell carcinoma, respectively.² A majority of these patients are subjected for surgery and only then the diagnosis is confirmed by histopathologic and immunohistochemical examination. The incidence of postsurgery recurrence is rare, especially in the genitourinary inflammatory pseudotumors, long-term follow-up of the patients may still be desirable.

The clinicians should consider an inflammatory pseudotumor in differential diagnosis of pelvic tumors, especially in cases when image findings and biopsies are inconclusive. Inadvertent surgical intervention may be avoided if a clinical diagnosis can be made as these lesions may respond to nonsteroidal anti-inflammatory drugs, systemic steroids, and radiation therapy.⁵

Conclusion

To conclude, we describe a rare case of the inflammatory pseudotumor of the renal pelvis. The symptoms, image findings of these tumors mimic those of transitional cell carcinoma. As these tumors may respond to medical management, clinicians should keep them in mind when working up the patients to avoid surgery.

Ethical Approval

The written and informed consent was duly obtained.

Abbreviations Used

MRI

magnetic resonance imaging

PET-CT

positron emission tomography-computed tomography

Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received by any of the authors. There are no conflicts of interests.

Cite this article as: Jindal T, Dhanalakshmi M, Pawar P, Panda J, Midha D (2020) Inflammatory pseudotumor of the renal pelvis, Journal of Endourology Case Reports 6:4, 405–408, DOI: 10.1089/cren.2020.0144.