Incidental Renal Botryomycosis in a Nonfunctioning Kidney

Botryomycosis is a unique form of bacterial infection, closely mimicking actinomycosis. The usual site of occurrence is the skin and renal botryomycosis is very rare. The most common organism is Staphylococcus aureus which can be identified using Gram stain and confirmed by culture. Early and accurate diagnosis can ensure appropriate antibiotic therapy. We present a young lady diagnosed to have incidental botryomycosis of the kidney, following nephrectomy.


Introduction
Botryomycosis is a rare chronic suppurative bacterial condition characterized by the presence of masses of funguslike sulphur granules. This infection may involve the skin or visceral organs [1,2]. To the best of our knowledge, very few cases of renal botryomycosis have been reported in the literature [3][4][5].

Case Report
A 29-year-old nondiabetic lady presented with right loin pain and fever of two months duration. The urine microscopy revealed numerous red blood cells and bacteria, and serum urea and creatinine levels were normal. An intravenous pyelogram showed a staghorn calculus. A dimercaptosuccinic acid (DMSA) scan performed at the same visit showed a right hydronephrotic, poorly functioning kidney ( Figure 1). A right percutaneous nephrostomy with double J stenting was performed and pus was obtained during the procedure. She was discharged with a right DJ stent left in situ. Six weeks later, she presented with persistent loin pain and diethylene triamine pentaacetic acid (DTPA) renogram showed a poorly functioning right kidney (19.29%). A right nephrectomy was undertaken and the specimen was sent for histopathological examination. Grossly, the right kidney appeared small and shrunken with cortical scarring and adherent capsule. Cut section of the kidney revealed cortical atrophy with a dilated pelvicalyceal system containing luminal necrotic debris. On histopathological examination, the renal interstitium showed fibrosis and dense inflammation composed of lymphocytes, plasma cells, neutrophils, eosinophils, and occasional multinucleated giant cells. The tubules were focally dilated and contained necrotic debris ( Figure 2). Occasional glomeruli showed periglomerular fibrosis. The renal parenchyma showed abscesses containing Gram negative organisms surrounded by amorphous eosinophilic material suggestive of Splendore Hoeppeli phenomenon (Figures 3 and 4). These bacterial colonies were negative for Grocott-Gomori silver and Ziehl-Neelson stains. A final diagnosis of renal botryomycosis superimposed on chronic pyelonephritis was rendered. The patient was treated with cefuroxime (2nd generation cephalosporin) for two weeks and prulifloxacin (new generation fluroquinolone) for 3 days. On followup, two years hence, the patient is asymptomatic and her urine microscopy is normal.

Discussion
Botryomycosis is an uncommon chronic granulomatous bacterial infection, primarily affecting the cutaneous and subcutaneous tissue. Visceral involvement is unusual [2,3].    The lung is the most common viscera involved; however botryomycosis of the liver, trachea, heart, bowel, and brain have also been documented [6]. Rare cases of renal botryomycosis have been reported in the literature ( Table 1). The most common causative agent of botryomycosis is Staphylococcus aureus, followed by Pseudomonas aeruginosa. Other bacterial etiological agents include Micrococcus pyogenes, Streptococcus, Escherichia coli, and Neisseria [2].
The factors implicated in the pathogenesis of botryomyocosis are impaired cellular immunity, virulence of the causative agents, phagocytic defects, and delayed hypersensitivity reactions [3]. Predisposing conditions include skin trauma, immunosupression due to diabetes mellitus, steroid therapy, or human immunodeficiency virus infection and cystic fibrosis [2,3]. These factors were absent in this case.
The most important differential diagnosis of botryomycosis is actinomycosis. Both these lesions demonstrate Splendore-Hoepple phenomenon characterized by deposition of periodic acid-Schiff positive amorphous eosinophilic material around bacterial colonies [6]. Gram and Grocott-Gomori silver stain help is distinguishing these two entities. Gram stain identifies the causative bacterial agent in botryomycosis, which is confirmed by culture. These bacterial colonies are usually negative for Grocott-Gomori silver  stain [6][7][8]. The present case revealed Gram negative bacilli. Specific subtyping could not be done due to lack of urine culture.
Furthermore renal botryomycosis can rarely present as a renal mass mimicking a neoplastic process and may pose a diagnostic dilemma. The diagnosis of botryomycosis if considered preoperatively on needle biopsy can be treated with appropriate antibiotic regimen, preventing the need for radical nephrectomy [1,5]. In the present case, the indication for nephrectomy was a poorly functioning hydronephrotic kidney in which botryomycosis was detected incidentally. As the urine culture was not done, we cannot categorically state that the botryomycotic infection presented prior to percutaneous nephrostomy.
In conclusion, renal botryomycosis is a rare treatable condition and if diagnosed early and accurately can prevent unnecessary sacrifice of the kidney.