Metanephric Adenoma Associated with Unusual Urinary Candidiasis: A Challenging Morbidity from Postoperative Anastomotic Leak

morbidity resulting from prolonged perinephric leakage secondary to urinary and perinephric fungus infection as a part of systemic candidiasis. The clinical, morphological and immunohistochemical features are presented together with a review of the current literature.


Introduction
Metanephric adenoma (MA) is an extremely rare benign neoplasm of the kidney, representing 0.2% of adult renal epithelial tumors [1]. Most cases are seen in the fifth and sixth decades, predominantly in females by a 2:1 ratio [2]. It may have some overlapping features with the solid variant of papillary renal cell carcinoma and is often difficult to distinguish from malignant neoplasms. Immunohistochemistry seems to be sufficient in the diagnosis of MA in the majority of cases and it usually has a good prognosis. Li et al. demonstrated multiple variants of MA, suggesting a wider classification spectrum than originally described, which advocate timely surgical treatment in all patients [3]. Partial nephrectomy is a highly recommended treatment option, despite some cases presented with metastatic disease [3].
Invasive fungus infection of the kidney is unusual and is difficult to treat. The guidelines of the Infectious Diseases Society of America (IDSA) recommended empirical antifungal therapy for patients with recent abdominal surgery anastomotic leaks [4]. This report describes a case of a MA associated with urinary candidiasis, resulting in unpredicted morbidity after successful partial nephrectomy.

Case Presentation
A 42-year-old non-smoker lady was referred to our tertiary care center after incidentally being discovered to have a right renal mass. She has recurrent aching pain localized to the right loin. The patient has no hematuria, bothersome voiding symptoms, or any constitutional symptoms. She was medically free with no past surgical history apart from cesarean sections with a current breast mass. There was no family history of malignancy or relevant medical conditions. Physical examination was unremarkable, and all preoperative laboratory workup was within the average range. Serum creatinine was 0.48 mg/dl, haemoglobin (Hb) level was 12.8 g/dl, and WBCs was 4.68×10 9 /L. Contrast-enhanced CT of the abdomen and pelvis showed a 3.5×4×4 cm, well-defined exophytic and lobulated soft tissue mass arising from the lateral aspect of the mid pole of the right kidney, which was inseparable from the adjacent liver. There was no evidence of tumor thrombus, lymphadenopathy or radiological signs of distant metastasis ( Figure 1  Four-week later, the patient came to the ER with fever of 39.6°C and remittent right loin pain, which was aggravated by inspiration and relived by NSAID. Serum creatinine was 0.76 mg/dl, Hb was 11.6 g/dl, and WBCs was 10.11×10 9 /L. CT/KUB revealed perinephric localized collection of 4.6×3.7×5.6 cm attached to the surgical bed, with normal enhancement of the right kidney, with no residual tumor local recurrence ( Figures 3A & 3B). This finding has not been detected in the postoperative contrast imaging performed on the 5 th postoperative day. Percutaneous drainage of the perinephric collection was performed guided by CT with insertion of a pigtail catheter, while the ureteral stent was removed under local anaesthesia. During cystoscopy, the bladder showed heavy pyuria with precipitation of purulent Candida albicans biofilm on the ureteral stent, as approved by culture and sensitivity, especially at its renal end ( Figure 3C). Postoperative urinary leakage continued for 14 days, where its creatinine contents was <10 mg/dl. The culture of the perinephric fluid showed heavy Candida albicans, similar to the high vaginal swab, which was managed with fluconazole orally daily for 7 days.  The tube drain was removed 48-hours of complete non-drainage, and a contrast-enhanced CT scan demonstrated normal enhancement of the right kidney and complete resolution of the previously mentioned perinephric collection. Follow-up till 10-month, showed normal kidney function and complete blood count. Last contrast-enhanced CT study revealed no local recurrence or distant metastasis (Figure 4).

Discussion
MA of the kidney was classified by the World Health Organization (WHO) as an epithelial benign tumor, which generally occurs in adults. However, it may include heterogeneous histological subtypes, with the coexistence of malignant components [3]. Nephron-sparing surgery is the treatment option of choice, with an excellent prognosis. In the current indexed case, partial nephrectomy was performed, and the postoperative contrast-enhanced CT showed no leakage. At the early postoperative course, the patient had severe pruritis vulva with whitish vaginal discharge, which was diagnosed by a gynaecologist as a fungal infection necessitating local antifungals. It seems that this was the source of ascending renal infection with Candida albicans, as proved later with urine culture and sensitivity. Despite the fact that funguria may be common in hospitalized patients, invasive kidney infection is unusual and is difficult to manage. Risk factors in this patient, including indwelling urethral catheter, intraoperative ureteral stent, and prior antibiotic therapy, may predispose to such infection [5]. Symptoms and signs may include flank pain, costovertebral angle and tenderness, which were the presenting manifestations after discharge.
Complications associated with fungal infections of the kidneys include fungus ball formation, perinephric abscess and surgical wound infection. Prolonged urinary leak from the partial nephrectomy bed seems to result from renal candidiasis; therefore, the ureteral stent was removed once the infection was confirmed, with discontinuation of antibiotics to reduce risk factors for acquisition of candiduria. Drainage of the perinephric collection alone may cure some patients with fungus infection. However, the guidelines of the Infectious Diseases Society of America (IDSA) recommended empirical antifungal therapy for patients with recent abdominal surgery, especially if they have anastomotic leak [4]. Considering the positive culture for Candida albicans from urine and perinephric collection, oral fluconazole was started, especially it will target the most likely species and will achieve adequate urinary concentration. After intravenous administration, fluconazole achieves equal serum and peritoneal concentrations [4]. Intravenous amphotericin B deoxycholate is an accepted alternative to fluconazole at a dose of 0.3-0.6 mg/kg daily.

Conclusion
Metanephric adenoma is a rare entity, which is managed by partial nephrectomy with good prognosis. Attention should be focused upon reducing the risk factors for candidiasis in surgical patients, such as removal of catheters and ureteral stents and discontinuation of antibiotics. Systemic antifungal is recommended for all patients with symptomatic candiduria.