Muconephrosis

Abstract

We report a case of a mucus-filled kidney (muconephrosis) encountered during laparoscopic nephrectomy for presumed xanthogranulomatous pyelonephritis. Conversion to open nephrectomy and en-bloc right hemicolectomy were necessary because of severe perinephric fibrosis and suspected renal-enteral fistula. Pathologic examination revealed a renal pelvic villous adenoma and diffuse intestinal metaplasia of the urothelium; no enteral communication or gastrointestinal pathologic features were found. Urothelial villous adenoma is extremely rare, and one should consider neoplastic etiologies, including appendiceal mucinous cystadenocarcinoma and mucus-secreting adenocarcinoma of the renal pelvis, in directing the appropriate management of muconephrosis.

Intestinal type villous adenoma of the renal pelvis

“…Only four cases of renal pelvis villous adenoma have been reported in the English-language literature. [5][6][7] Bhat and colleagues noted moderate dysplasia without invasion 4 and Fudge and colleagues demonstrated superficial stromal invasion. 5 These findings are similar to our own case, which is predominantly a lowgrade villous adenoma, with areas of high-grade dysplasia and microscopic stromal infiltration.…”

“…Symptoms noted in prior cases of villous adenoma of the renal pelvis include back or flank pain, fever, abdominal discomfort and weight loss. [4][5][6] A history of urinary tract infection 6 and nephrolithiasis 4,5 have been identified as risk factors. In the more common cases arising in the bladder, patients commonly present with irritative voiding symptoms and hematuria.…”

“…There are no specific imaging findings on CT scan for villous adenoma of the renal pelvis. In this case and the four previous cases, hydronephrosis and thinning of the renal cortex was identified on CT. [4][5][6][7] In a case of villous adenoma of the ureter, there was obstruction and hydroureternephrosis on both CT and retrograde pyleogram to the L3 level. 9 A mass, which may include cystic changes, is also common.…”

“…10 While the presence of mucous may suggest intestinal-type villous adenoma, this can also be found in association with pseudomyxoma peritonei, xanthogranulomatous pyelonephritis and local invasion from gastrointestinal malignancy. 6,11 Therefore, definitive diagnosis relies on light microscopy.…”

“…1,6 Intestinal metaplasia of the urinary tract is often associated with chronic inflammation, in particular urinary tract infection, stones, or chemical injury. 1,4 In the pathogenesis of both colorectal adenocarcinoma and urothelial carcinoma of the upper urinary tract, there has been recent interest in DNA mismatch repair proteins.…”