The incidence of renal cell cancer has been rising over the decades. In Russia, kidney cancer (most commonly renal cell carcinoma, RCC) accounts for 3.9 % of all malignant tumors. The country recorded 8,430 deaths from the disease in 2014 and 22,234 new kidney cancer patients were revealed [1]. If RCC is diagnosed at clinical stage T1 [2], then partial nephrectomy — the gold standard of treatment for renal tumors smaller than 4 cm in diameter — can be effectively performed. It should be noted that recent years have witnessed an increase in the number of laparoscopic and robotic surgeries in this group of patients in recent years.

Congenital anomalies of the kidney and urinary tract are common in about 3.3–11 % of the population [3]. According to autopsy data, renal fusion accounts for 16.5 % of all kidney anomalies — 1 in every 425–700 people. The number of men with such anomalies is twice higher than women. The most common and clinically significant type of renal fusion is the horseshoe kidney, which is characterized by the fusion of the lower poles (in about 90 % of cases) and rarely of the upper poles, causing the joined kidneys to take a U-shape form, resembling a horseshoe. In addition, each kidney has its own ureter emptying into the bladder and supply vessels [4].

Diagnosing renal anomalies of shape at the present stage is not difficult since ultrasound imaging can identify the presence and type of abnormal fusion. Intravenous contrast-enhanced computed tomography scan provides more complete information about the state of the renal parenchyma, blood supply, urinary tract, and relationship with neighboring organs. So, according to studies, horseshoe kidney has abnormal blood flow in 70–84.3 % of cases [5].

Description of clinical case

Patient V., 65 years old, came to the Hertzen Moscow Cancer Research Institute (HMCRS) with previously identified space- occupying lesions of the right kidney.

From the patient’s history, it was known that the patient had been feeling sick since August 2015 when he experienced increased body temperature of up to 38.5–40 °C and was hospitalized at the infectious department of a medical unit in Chelyabinsk. Ultrasound imaging was used to examine the abdominal cavity, which identified a tumor in the right kidney. Afterwards, the patient decided to visit HMCRS for treatment.

The patient has a hereditary burden: the father suffered from lung cancer. Among the comorbidities are stage II hypertension, type 2 diabetes (decompensation stage), cirrhosis of the liver caused by toxins (class B according to Child-Pugh score), portal hypertension, esophageal varices complicated by bleeding for which endoscopic ligation was performed in 2014.

A tumor of 34 x 35 x 35 mm in size without any signs of invasion into the pyelocaliceal system was found through ultrasound imaging and spiral computed tomography scan of the abdomen and retroperitoneal space at the border of the upper and lower third of the right kidney on the front surface. Besides, renal fusion in the lower pole region was identified. The defect detected was a medical finding since it had no clinical manifestations in the patient. The RENAL nephrometry score was 4a (fig. 1, fig. 2).

No regional and distant metastasis were found by assessment of the prevalence of tumoral process. Diagnosis: tumor in the right half of horseshoe kidney, stage I, cT1aN0M0.

Laparoscopic resection of the right half of the horseshoe kidney was performed in October 19, 2015. After pneumoperitoneum was created using a Veress needle, three trocars were inserted by a standard technique [6]. During inspection on the border of the upper and middle third of the right half of the horseshoe kidney along the lateral surface, a tumor mass, 4 cm maximum size, was identified. The renal hilum was mobilized, and a clamp was imposed on it through a counteropening. A cold scissors was used to resect the tumor within healthy tissues. Kidney wound was cut down by atraumatic suture using non-absorbable clips Absolok (Ethicon, Belgium, USA) (fig. 3). During the operation, we used tools and devices from endoscope manufacturer Karl Storz (Germany).

The surgery lasted for 160 minutes, anoxia period lasted for 20 minutes, and there was 400 ml of blood lost. The postoperative period was uneventful. Glomerular filtration rate at the preoperative stage was 87 mL/min, at the 4th day — 59 mL/min, and 8th day — 67 mL/min. The patient was discharged on the 9th day in a satisfactory condition.

Morphological study revealed a clear-cell renal cell carcinoma G1, without extension to the perirenal fat and with no tumor cells on the resection edge (R0) (fig. 4).