Duplication of kidney with emphysematous pyelonephritis in lower moiety

Clinical History

A 50-year-old man suffered from abdominal fullness for 3 weeks and fever on and off for 2 days. He had a history of renal stone and duplication of the left kidney. Physical examination revealed a firm tender mass over the left upper quadrant of the abdomen.

Imaging Findings

Laboratory tests showed abnormal elevation of white blood cell count (21 190/mm³), blood urea nitrogen (84 mg/dl), and creatinine (5.4 mg/dl). Urine analysis was positive for occult blood, but no glucosuria or pyuria was noted. Plain abdominal radiography showed a huge ovoid air density in the left upper abdomen (Fig. 1). Ultrasound of the right renal fossa showed "dirty" echogenic shadows and non-visualization of the right kidney. Plain computed tomography (CT) of the abdomen showed destruction of the left kidney and a cystic mass, measuring 13×15.5×18 cm, with air-fluid level in the left retroperitoneum (Fig. 2). A preserved upper moiety of the left kidney was noted in the medial part. Ultrasound-guided percutaneous drainage was done and a large amount of gas and brownish pus was drained out. The pus culture grew Bacteroides species. Magnetic resonance imaging (MRI) after the drainage procedure showed stenosis in the lower moiety of the left upper ureter with a residual thick-walled abscess in the left lower kidney. The upper moiety was small and compressed by the mass. Because of the poor effect of percutaneous nephrostomy and because of the flared up of fever, a left nephrectomy was then done. Histology revealed pelvicalyceal dilation with necrotic debris coating. The renal parenchyma had a diffuse brownish and fragile necrotic appearance. The renal capsule was fibrotic and adhered to the perirenal fat which also showed necrosis. Histological diagnosis was compatible with left pyelonephritis and pyonephritis. The postoperative course was uneventful and clinical follow-up 2 months later was unremarkable.

Discussion

Emphysematous pyelonephritis is a fatal disease with reported mortality from 40% to 90% [1-3]. It is characterized by rapid, progressive high fever, renal parenchyma necrosis and gas trapping in the kidney. Most of the patients have diabetes (90–98%) [1-3], and in non-diabetic patients, most of them have urinary obstruction [1]. Women are predominant (2:1), with a mean age of 55 years old. Most patients have had some renal impairment before admission [1, 2, 4]. Escherichia coli is the most common infecting organism [1], followed by Klebsiella pneumoniae, Aerobacter aerogenes, Proteus mirabilis, and mixed or other flora [5]. Recently, Wan et al. [6] defined two types of emphysematous pyelonephritis. Type I is characterized by parenchymal destruction with either absence of fluid or presence of streaky or mottled gas. Type II is characterized by either renal or perirenal fluid collections with bubbly or loculated gas in the collecting system. The mortality rate for type I (69%) is higher than for type II (18%) [5]. Symptoms and signs are usually non-specific. Nausea, general malaise, flank pain and fever are major complaints. Pyuria, hyperglycemia and electrolyte imbalance can also be found [1-3, 7-9]. Because the symptoms are obscure, the diagnosis of emphysematous pyelonephritis relies on radiographs. A plain film of the abdomen may show mottled gas within the renal outline and with extension to the perinephric space or retroperitoneum through the Gerota’s fascia [2]. Somehow the plain abdominal films show renal parenchymal gas in only 33% of the patients [1]. In Roy et al.’s study [5], only 2 of 5 patients had gas on radiographs. Moreover, it is difficult to differentiate from the overlying bowel gas on radiographs. In our case, a huge gas shadow was noted on the plain radiography of the abdomen, which was rarely seen in previous reports. On ultrasonography, gas can cause echogenic foci (comet tail artifact), which can be mistaken for calculi or bowel gas. In study by Narlawar et al.[2], 8 of 11 patients with ultrasonography had comet tail and reverberation. In addition, ultrasonography has a limitation in detecting intrarenal gas because of the confusion either with surrounding bowel gas or with calcifications within the kidney [3, 8]. CT has advantages of defining the extent and quantification of the gas and also gives an idea of the destruction of the renal parenchyma and identifies the location of gas impaction [2]. Our case was characterized by duplicated and conjoined ureters. The ureters showed hydronephrosis and pyonephrosis of the lower moiety of the left kidney with obstruction in the left upper ureter, and the upper moiety was compressed by the mass. Only few cases of such a condition have been reported. Management should include control of diabetes, balance of electrolytes and potent antimicrobial therapy. Before the advance of interventional radiology, surgery was the gold standard for treating emphysematous pyelonephritis [1, 4, 10, 11]. Imaging guided percutaneous drainage combined with antibiotic therapy is an acceptable alternative to surgical intervention [12, 13, 14].

Differential Diagnosis List

Final Diagnosis

Pyelonephritis and pyonephritis, left kidney

URL:	https://www.eurorad.org/case/5087
DOI:	10.1594/EURORAD/CASE.5087
ISSN:	1563-4086