A 72-year-old female presents with left flank pain of two months duration, attenuated with position changes, accompanied by fever and polyuria. She is hospitalized and antibiotic treatment is started under the clinical suspicion of complicated pyelonephritis. During the approach, a computed tomography (CT) scan with intravenous contrast was performed. It revealed a left renal abscess, hydronephrosis, and a staghorn calculus, for which percutaneous drainage was placed (Fig. 1A). As there was no clinical improvement, coupled with the formation of a cutaneous fistula draining purulent fluid, a simple nephrectomy was performed, but was complicated due to the presence of multiple peritoneal adhesions at the level of the splenic flexure of the colon, so during the procedure it was decided to perform splenectomy and partial colectomy as well. Gross examination revealed a terminal kidney, a staghorn calculus occupying the renal pelvis, purulent fluid, and multiple exophytic lesions with a papillary appearance, which extended close to the ureteral surgical border (Fig. 1 B).
Histopathological findings were villoglandular fronds lined by pseudostratified columnar epithelium, in addition to intestinal metaplasia in the renal pelvis and ureter with involvement of the ureteral surgical border. Another finding was of intestinal-type adenocarcinoma with microinvasion to the lamina propria (Fig. 2). Immunohistochemistry (IHC) stains were performed for CK20, CDX2, and SATB2, all of which were positive and corroborated the intestinal differentiation of the tumor (Fig. 3).
After five days of favorable clinical evolution during the patient's postoperative period, hospital discharge was decided. After one year of follow-up, the patient is asymptomatic, in good general condition, and with no evidence of distant metastasis.