Our understanding of renal infection by
C. Albicans is greatly advanced though the study of animal model. It has been shown that this fungus can be detected in all main organs, especially in the brain or kidneys [
11] shortly after inoculation. In the kidneys, yeasts pass through the vascular walls into both of the cortex and medulla, attracting neutrophilic infiltration. Infection in the kidneys, as contrasted to other organs, is not controlled [
11,
12]. In the first 12
h, yeast forms elongate and rupture from the interstitium into renal tubules, produce germ tubes and markedly proliferate and elongate. Mycelial casts move down into the medulla and are caught in the loop of Henle, here elongated hyphae can rupture into the interstitium and cause an inflammation reaction mainly composed of mononuclear cells. The hyphae gradually fractured and disappeared. Two weeks after the inoculation, only cellular scars are left in the cortex. If the initial inocula are too much, mice can die due to organ failure and sepsis. The kidneys have diffusely scattered abscess. If the inocula are sublethal, a so-called excretory lesion can be resulted, which mainly confined to the renal pelvis, collecting ducts and ureter [
2].
Candida cause diseases in human when the body defense is compromised such as diabetes mellitus, human immunodeficiency virus infection, cancers, neutropenia, or immunosuppression due to organ transplantation, or when the patients undergo certain procedures such as bladder catheterization or urologic procedure [
13]. Patient with type II diabetes mellitus have more infections and course of infections is more complicated. One possible explanation for this is a defect in immune response. It has been shown that a TH2-axis shift, which decreases TH1-dependent immunity. In addition, decrease in cytokine response after stimulations or low-complement factor 4 may contribute for the compromise of humoral innate immunity. It has also been demonstrated that there are decreased functions in chemotaxis and phagocytosis in diabetic PMNs and monocytes [
14].
C. Albicans infection can present as a mass lesion and have been reported in stomach [
15], pancreas [
16], liver [
17], and hand [
18]. Couple of cases of granulomatous pyelonephritis have been reported in kidneys [
9,
10]. Mass-forming property may be related to the fungal ability to produce pseudohyphae.
C. glabrata does not produce true hyphae and cannot produce pseudohyphae except under special cultural conditions. This hyphaeless fungus rarely produces renal mass in the renal pelvis [
19].
C. Albicans infection in the urinary system can occur through two ways, one is through the blood to spread into the renal parenchyma, and the other is retrograde through the urinary tract [
2].
In our case, the mass is composed of granulomatous inflammation, necrosis, and abscess consistent with xanthogranulomatous pyelonephritis (XGP) [
20]. No tumor was identified in a well-sampled nephrectomy specimen. XGP is a chronic granulomatous inflammation, most commonly occurred in middle-aged women [
9,
20]. The most common microorganisms are
Escherichia coli and
Proteus mirabilis [
21–
24]. Candida can be a cause but is very rare [
9,
10]. Computed tomography (CT) is a major diagnostic tool. The findings include hydronephrosis (90.9%), renal stones (72.7%), pyonephrosis (45.5%), intraparenchymatous collection (45.5%), cortical renal atrophy (45.5%), nonfunctioning kidney (36.4%), abscess (36.4%), and perinephric fat accumulation (18.2%) [
25]. In our case the imaging findings are not typical. We found a heterogeneous and ill-defined mass involving the kidney with extension into outside of kidney. No real calculus or hydronephrosis was identified albeit the patient underwent cystoprostatectomy with neobladder three years ago.
All in all, in our case, patient's previous history of bladder cancer status after bladder resection in combination of type 2 diabetic mellitus and smoking may all contribute the infection.
In summary, C. Albicans is a rare cause for xanthogranulomatous pyelonephritis, which can mimic various benign and malignant conditions. Treatments include nephrectomy and antifungal medications.
