The kidney is one of the most common sites for the cyst in the body (prevalence about 5%). Kidney cysts are sacs of fluid in the kidneys which are characterized as "simple" cysts with a thin wall (1). They become common as people getting old and are with no symptoms or harm. Because they often don’t cause symptoms are incidentally found by renal imaging including computed tomography (CT) and ultrasonography (2, 3). The prevalence, number, and size of renal cysts are greater in men compared to women and are connected to age, hypertension, and smoke (4). Most renal cysts (sporadic, acquired, or hereditary) arise from parts of nephrons or collecting ducts, while multicystic dysplasia arises before the formation of nephrons (5).
The calyceal diverticulum or pyelocalyceal diverticulum is a urine-containing cystic cavity within the renal parenchyma lining by transitional epithelium and surrounded by muscularis mucosae which are connected to the collecting system (6). The majority of calyceal diverticula can be diagnosed by ultrasound and intravenous urogram (IVU) and retrograde studies are required to confirm calyceal diverticula diagnosis. More often than not, the diverticulum is misdiagnosed as a complex cyst or even as a neoplasm.
The treatment strategy is completely dependent on the exact diagnosis of cysts or calyceal diverticula and it is critical to discriminate cysts from calyceal diverticula. In some patients, there is not possible to place a Double J stent because of the skeletal situation of patients or make the surgery duration shorter. In the current study, we use laparoscopic methylene blue in cysts to ensure there is no contact with the pyelocaliceal system.
A 52-year woman referred to Sina hospital complaining about vague right flank pain and heavy feeling. Her diagnosis was a large flank cyst. She had no family examination, no history of surgery, and no other illness. Abdominal and pelvic computed tomography with and without contrast and simple culture indicated to the 15 cm cyst.
We selected this case and all steps of our study were completely adhere to CARE guidelines. She was the candidate for surgery but there was no certain diagnosis between renal cysts and calyceal diverticulum. In the flank position and through the open access the trocar 15 was embedded. Then peritoneoscopy was performed and 2 trocars 5 were implanted. The colon with strong adhesion was fully medialized. Now the cyst was exposed (Figure 1). The needle was inserted through the skin into the large cyst and sterile methylene blue was injected (Figure 2). The cyst was complete with blue color. The catheter was checked to see whether the blue color enters the urine stream or not (Figure 3). Fortunately, it was completely clear and its roof was unroofed. At the bottoms of the cyst, several small cysts were observed so we inject methylene blue as mentioned above and check for urine color, after approved that the lesions are cyst, the cyst wall was removed. After six weeks and six months, the patient report the satisfying result of surgery with no vague right flank pain or cyst recur in follow-up sonography.
Figure 1: Reveal cyst
Figure 2: Injection of methylene Blue
Figure 3: Check of urine color
The exact diagnostic between renal cysts and calyceal diverticulum is problematic. In the current study, we use a new approach for antegrade detection by using methylene blue color. In fact, for renal cystic treatment the percutaneous aspiration, with or without sclerotherapy can be the lucrative minimally invasive option with very high recurrence rates (up to 90%) (7, 8).
Calyceal diverticulum mimics solitary or multiple fluid-filled spaces located within one or both kidneys (9, 10). They are mostly placed in the upper pole of the kidney in the connection with the minor calyx so their treatment strategy is different from renal cysts. Surgical ablation of calyceal diverticula by percutaneous endoscopy, laparoscopy, and ureteroscopy has fundamentally taken the place of both extracorporeal shock wave lithotripsy (ESWL) and open surgical fulguration in almost all cases of diverticular cavities (11). In our case, it was important to know it is calyceal diverticula or Pyelogenic Cysts. The typical renal cyst looks transparent and is black and blue in some areas so injecting methylene blue into the cyst can aid the surgeon to identify the cyst wall more accurately (12). Methylene blue is a fluorophore and a heterocyclic aromatic compound with a diameter of 1.43 nm, 320Da, with an excitation peak of 670 nm and an emission peak of 690 nm (13). It was reported by Roberts and his colleagues that for parenchymal cysts, the methylene blue injection through the ureteral catheter can make it clear there is no communication with the collecting system (14). In 2018, Wang and his colleagues represented a modified method for easily locating cystic wall by methylene blue Injection via percutaneous penal cyst puncture in the flexible ureteroscope (15). In our study, the needle was inserted through the skin into the small cysts and methylene blue injection indicated no connection with renal calyx so the lesion is renal cysts.
In some patients, there is not possible to place a Double J stent because of the skeletal situation of patients or make the surgery duration shorter. Also, Double J has its complication and difficulties. Laparoscopic injection of methylene blue can be a new approach for distinguishing a cyst from a calyceal diverticulum in such cases.
SMKA was the principal surgeon and who suggest this novel method, HRZ was the surgeon, and FKH wrote the manuscript.
Special thanks to Urology Research Center (URC), Tehran University of Medical Sciences, Tehran, Iran.
Conflict of interest
All authors claim that there is no competing interest in this case report of surgery.
There was no founding.
All authors ensured our manuscript reporting adheres to CARE guidelines for reporting of case reports.
CT Computed tomography
Dj Double J stent
ESWL Extracorporeal shock wave lithotripsy
IVU Intravenous urogram